Study on the seismic stability of urban sewage treatment and underground reservoir of abandoned mine pumped storage power station

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This paper delves into cutting-edge models and attributes of integrating pumped storage hydropower systems with subterranean reservoirs and advanced wastewater treatment facilities within these decommissioned mines. By utilizing the expansive underground voids left by coal extraction, this method aims to achieve multifaceted objectives: efficient energy storage and generation, reclamation of mine water, and treatment of urban sewage. The research enhances the development and deployment of pumped storage technology in the context of abandoned mines, demonstrating its potential for fostering sustainable energy solutions and optimizing urban infrastructure. This study not only facilitates the progressive transformation and modernization of energy cities but also provides crucial insights for future advances in ecological mining practices, energy efficiency, emission mitigation, and green development strategies in the mining industry. Earth and environmental sciences/Environmental sciences/Environmental impact Earth and environmental sciences/Environmental social sciences/Energy and society Earth and environmental sciences/Environmental social sciences/Sustainability Abandoned mine Pumped storage power station Multi-energy complementation Sewage treatment Seismic stability Sustainable development Figures Figure 1 Figure 2 Figure 3 Figure 4 Figure 5 Figure 6 Figure 7 Figure 8 Figure 9 Figure 10 Figure 11 Introduction China's coal resources have been continuously exploited on a large scale for a long time. According to statistics, the number of abandoned mines worldwide has exceeded 1 million, and by 2030, China is expected to have 15,000 abandoned mines, with the number of closed and abandoned mines increasing daily 1 . After a mine is abandoned, it leaves behind considerable volumes of various forms of underground roadways and chambers. If these are not treated or reused, they can lead to serious water pollution and geological disasters 2 . Therefore, the rational utilization of space and water resources left by abandoned mines to achieve efficient secondary utilization of underground resources has been a long-standing challenge for China's coal industry. Since 1960, R.D. Harza proposed the concept of utilizing underground or open-pit mines for building pumped storage power stations 3 . Successively, countries such as Austria, the United Kingdom, the United States, and China, among others, have repurposed abandoned mines for constructing pumped storage power stations 4 . This approach not only positively impacts disaster prevention and control in underground goafs but also contributes to the ecological restoration of mines. Economically, repurposing abandoned underground spaces reduces construction time and significantly lowers investment costs 5 . Simultaneously, urbanization has led to increased discharge of domestic sewage, necessitating measures for sewage recycling to address water shortages and pollution 6 , 7 . However, challenges persist in sewage treatment, including low inlet water concentration, suboptimal collection rates, and high operating costs, severely impeding sustainable socioeconomic development 8 . "Energy conservation, carbon reduction, and efficiency enhancement" are critical imperatives for urban sewage plants. Various countries, including the United States, the United Kingdom, and Japan, are developing underground sewage treatment plants, which have demonstrated favorable economic and social outcomes 9 . With decreasing costs associated with underground space development, the feasibility of underground sewage treatment plants is growing, aligning with the trend of modern metropolitan facilities moving underground. The construction of underground sewage treatment plants is well-suited to China's conditions of high population density, limited land availability, and climatic diversity. Therefore, as China enhances water environment governance, underground sewage treatment plants are poised for significant global development 10 . In summary, the pumped storage power station and urban sewage plant form a small integrated energy system with electricity, water, and carbon coupling and mutual influence 11 . Introducing a multi-energy complementary integrated energy system into the underground sewage treatment plant of an abandoned mine can effectively compensate for high energy consumption, playing a key role in improving the daily operation, energy conservation, and energy security of the underground sewage treatment plant 12 . Therefore, considering the vast underground space of coal mines, a strategic concept of transforming and upgrading abandoned mines and comprehensively utilizing underground space is proposed, including establishing pumped storage power stations, wind power stations, photovoltaic power stations, and urban sewage treatment plants. Treating urban sewage while storing water in abandoned mines can efficiently utilize the underground space of abandoned mines and overcome the site selection restrictions of conventional pumped storage power stations. Based on systematically collected hydrogeological data of abandoned mines in China, this paper sorts out the secondary development and utilization methods of abandoned mine underground space, comprehensively analyzing and demonstrating the feasibility of urban sewage treatment in abandoned mine pumped storage projects. It constructs a comprehensive utilization model of urban sewage treatment based on abandoned mine pumped storage power stations under regional conditions in China, which not only efficiently and reasonably utilizes underground resources of abandoned mines but also has certain reference and guiding significance for the ecological restoration of abandoned mines and urban sewage treatment. Feasibility study of model system Research status of pumped storage power stations in abandoned mines The inception of pumped storage power stations in China dates back to 1968 13 . However, during that era, power shortages were the primary concern within the power system, overshadowing the regulatory potential of pumped storage stations. It wasn't until 1980 that the expansion of power grids in Guangdong Province, North China, and East China accelerated, exposing the limited load regulation capacity of the existing power system as a bottleneck hindering economic development 14 . Presently, Japan boasts an in-service pumped storage capacity comprising 8.5% of its total installed power supply capacity, while Italy, Spain, Germany, and France range from 3.5% to 6.6% 15,16 . Fig. 1 illustrates the evolution of China's total pumped storage capacity since 2010 and its contribution to the nation's overall installed power capacity. Despite the rapid growth of new energy installations in China, a substantial gap persists when comparing the proportion of installed capacity to that of developed nations and China's own pumped storage development targets. Based on incomplete statistics gathered from public data sources such as Power China and local government websites, Fig. 2 illustrates the distribution, scale, and average construction costs of pumped storage power stations in China 17–19 . By the conclusion of 2023, 43 pumped storage power stations had been completed and commissioned in China, boasting an aggregated installed capacity of 46.85GW. Fig. 3 provides a geographic breakdown of operational and under-construction pumped storage power stations across various provinces and regions nationwide. This portrayal reveals an uneven development landscape characterized by significant disparities in installed capacity. Currently, pumped storage power station development is predominantly concentrated in economically advanced eastern regions and central, northern, and northeastern China, where thermal power holds sway. Notably, provinces such as Guangdong, Zhejiang, Anhui, Hebei, and Fujian feature prominently in this regard. Conversely, the western provinces, including Xinjiang and Tibet, host only a sparse number of pumped storage facilities. Furthermore, pumped storage resources remain exceedingly scarce in other provinces 20 . Research status of multi-energy complementary comprehensive utilization With China's ongoing adjustments to its energy structure, the proportion of renewable energy sources, particularly wind and solar, has been steadily increasing 21 . However, wind and solar energy exhibit characteristics such as randomness, volatility, intermittency, seasonality, and regional disparities, leading to poor sustainability and stability of energy supply, thereby presenting significant challenges to grid integration 22,23 . To mitigate the impacts of these renewable sources on the power grid, large-scale energy storage solutions are essential 24,25 . Currently, mature energy storage technologies capable of large-scale power storage mainly include pumped storage and compressed air energy storage systems 25,26 . However, traditional ground-based installations for pumped storage and compressed air energy storage require stringent site selection criteria, necessitating abundant high-altitude energy storage space, which is limited in availability. Conversely, abandoned mines, abundant in various European and American countries due to their well-developed mining industries, offer vast underground spaces suitable for energy storage facility construction, making them pioneers in abandoned mine utilization 27,28 . Since the 1960s, the United States, the United Kingdom, Germany, and other European and American nations have conducted extensive research and practical applications concerning abandoned mines, yielding remarkable results. In contrast, China's exploration into abandoned mine development commenced relatively late, constrained by factors such as complex mine geology and numerous partially closed mines. Initial efforts in this area have primarily focused on industrial experiments, including coal mine gas extraction, underground coal gasification, underground reservoir construction, and gas storage within abandoned mines 29,30 . Therefore, leveraging the hydrogeology of abandoned mines, along with their spatial resource conditions above and below ground, adjacency relationships between mines, and factors such as wind, solar, and other new energy sources, a paradigm of multi-energy complementarity and comprehensive utilization, notably pumped storage power generation within abandoned mines, has started to emerge 31–34 . The schematic representation of the comprehensive utilization system of abandoned mines is depicted in Fig. 4. Research status of urban sewage treatment In recent years, with the continuous advancement of urbanization, the discharge of urban domestic sewage has continued to grow, and the recycling of urban sewage has become an important measure to solve the problem of population water shortage and water environment pollution. However, the corresponding sewage treatment methods are lagging behind, which seriously restricts the sustainable development of social economy 35–37 . It can be seen that strengthening urban sewage treatment is an important way to comprehensively enhance urban functions and improve public services. Fig. 5 illustrates the typical urban wastewater treatment process in China, comprising primary physical treatment, secondary biological treatment, and tertiary advanced treatment 38–40 . Primary treatment involves units such as the grid, regulating tank, lifting pump, and primary sedimentation tank. The grid intercepts suspended solids, the regulating tank regulates and homogenizes water quality, and the lifting pump transfers sewage to the primary sedimentation tank for further sedimentation and filtration. Secondary treatment primarily employs microorganisms to remove organic matter, nitrogen, and phosphorus, mitigating CH 4 and N 2 O emissions while generating carbon emissions. Effluent from the biochemical tank undergoes secondary sedimentation for mud-water separation; the supernatant, typically containing microorganisms, nitrogen, and phosphorus, can serve as agricultural or irrigation water. The deposited sludge exhibits significant biochemical activity; a portion is recirculated to the biochemical tank via the reflux pump to maximize activity, while the remainder, along with sludge from the primary sedimentation tank, is directed to the biogas tank. Tertiary treatment utilizes adsorption, electrodialysis, reverse osmosis, and similar methods for comprehensive removal of organic matter, nitrogen, and phosphorus from secondary effluent, yielding tertiary effluent suitable for industrial miscellaneous reclaimed water. The current ground sewage treatment plants face various issues including air and noise pollution, wastage of land resources, and high operational costs. Consequently, underground sewage or reclaimed water plants are increasingly favored due to their ability to mitigate these challenges. The development of underground sewage treatment facilities aligns with the trend of modern metropolises moving public infrastructure underground 41,42 . Many countries, including China, the United States, the United Kingdom, and Japan, are actively developing such facilities, yielding positive economic and social outcomes. While underground sewage treatment plants offer benefits, they pose challenges such as increased energy consumption due to the need for ventilation and deodorization systems. The energy demands of underground plants surpass those of equivalent above-ground facilities, necessitating innovative power supply solutions to address this issue urgently 43–45 . Model performance evaluation Power generation and storage assessment After a mine is abandoned, a large area of ground and underground space is left unused. This not only reduces the need for extensive dam construction during subsequent development but also results in cost savings. Additionally, the structure of photovoltaic power generation systems is straightforward, comprising only photovoltaic arrays, inverters, and combiner boxes. This simplicity streamlines the process of integrating photovoltaic energy storage devices, facilitating the timely storage and utilization of photovoltaic electricity through pumped storage stations. This approach promotes the efficient consumption of renewable energy while mitigating the environmental pollution associated with photovoltaic energy storage devices, thus contributing to the enhancement of the surrounding ecological environment. Furthermore, the incorporation of photovoltaic power into pumped storage power stations enhances their peak regulation capacity. In summary, utilizing abandoned mines for the construction of wind and photovoltaic pumped storage power stations represents a prudent choice concerning power grid operations, the utilization of renewable energy, ecological preservation, and economic viability. Assessment of sewage treatment capacity The operation of urban sewage treatment plants is directly related to treatment efficiency and costs. In the context of sewage treatment systems for pumped storage power stations, considerations include water treatment processes, carbon emissions, sewage classification, utilization, and available space in abandoned mines. This entails analyzing intake forecasts, pollutant concentrations, and water demand for the following day. Coordination of environmental protection objectives in sewage plant operation involves a comprehensive assessment of energy costs, carbon emissions, equipment maintenance, sewage reuse benefits, and environmental benefits related to water quality improvement, while meeting treatment standards and operational constraints 46,47 . Compared to traditional sewage purification plants, the sewage treatment system of pumped storage power stations is equipped with a three-stage sedimentation tank before the regulating tank. This arrangement facilitates the natural sedimentation of large particles in the sewage, resulting in predominantly turbid colloids entering the regulating pool. This condition optimally prepares for subsequent coagulation, thereby reducing the required dosage of flocculants. The primary advantage lies in addressing energy consumption issues typically associated with sewage plants, consequently reducing operational costs 48–50 . Integrated technology model of urban sewage treatment by multi-energy complementary abandoned mine pumped storage powerstation Multi-energy complementary power generation mode of abandoned mines The abandoned mine pumped storage power station consists of two main components. The first part resembles a traditional pumped storage power station, operating on the principle of utilizing surplus power from the grid during periods of low demand to drive water turbine units in the lower reservoir 51,52 . This water is then pumped into the upper reservoir for energy storage. Conversely, during peak electricity demand, water from the upper reservoir is released to turn hydro-generator units in the lower reservoir, converting gravitational potential energy into electrical energy. The second part incorporates photovoltaic and wind power generation systems. The structure of the pumped storage power station is depicted in Fig. 6, illustrating the underground framework utilized for the construction of the pumped storage system and the ground structure for the wind photovoltaic power generation system 53,54 . The underground structure primarily comprises four components: the upper reservoir, the lower reservoir, the underground plant, and the waterway system. Leveraging the significant height difference between the underground mine void and the upper roadway void, the underground roadway and void serve as the lower reservoir, while the upper shaft roadway void is utilized as the upper reservoir. The plant accommodates various equipment, such as pump generators, turbines, generators, and related controls, and can be constructed within underground roadways and spaces. The waterway system includes a channel and a tailwater channel connecting the upper reservoir and the lower reservoir, with the main pipeline of the pumped storage power station typically situated in the mountain apart from the inlet and outlet. The construction of surface wind photovoltaic power stations primarily involves utilizing a large area of abandoned land in abandoned mines and selecting suitable areas for the installation of photovoltaic arrays and wind power generation. Solar panels, brackets, inverters, and box-type transformers are arranged in the photovoltaic array, with the azimuth angle determined by the terrain, slope, and inclination angle of the bracket installation in the abandoned mine 55 . Sewage treatment mode of abandoned mine pumped storage power station Fig. 7 illustrates the structural layout of the sewage treatment plant. Equipped with various facilities such as regulating pools, secondary pools, and tertiary pools, the waste mine sewage treatment system not only satisfies the demand for sewage treatment and water collection but also offers flexibility for regulating water volume. Tailored to the characteristics of underground sewage treatment plants, advanced technologies including high-standard deodorization, ventilation, fire protection, efficient underground lighting, and emergency safety facilities ensure compliance with high effluent standards and promote energy efficiency. This approach presents a viable solution for upgrading underground wastewater treatment plants and enhancing effluent quality 56 . Integrated operation mode of abandoned mine pumped storage power station Based on the ground space resources, water resources, surrounding wind energy conditions, and photovoltaic conditions of the abandoned mine, a multi-energy complementary development and utilization design scheme suitable for pumped storage and sewage treatment can be proposed, as illustrated in Fig. 8. Spatial layout of the engineering model The pumped storage power station, a technology in use for over a century, stands as the most reliable, economical, and largest-scale energy storage solution 57,58 . Operating on the same principle as conventional pumped storage stations, the abandoned mine pumped storage power station employs surplus power, wind energy, solar energy, or other electricity from the grid for energy storage. During this process, water is pumped from a lower reservoir to an upper reservoir, representing the energy consumption phase. Subsequently, during peak electricity demand, water from the upper reservoir is discharged through a generator to the lower reservoir, converting potential energy into electrical energy. The distinguishing feature of the abandoned mine pumped storage power station lies in its lower reservoir, which utilizes underground waste spaces such as roadways and goafs. Additionally, both upper and lower reservoirs are designed as sewage treatment stations, maximizing space utilization and addressing the energy consumption challenges of sewage treatment plants. Analysis of the comprehensive utilization benefits of abandoned mine pumped storage power station With the aim of "increasing the proportion of non-fossil energy" in China, a target of over 1.2 billion kilowatts of wind and solar installed capacity by 2030 has been proposed. This necessitates concurrent improvements in energy storage systems and security measures. It is anticipated that pumped storage capacity will exceed 62 million kilowatts by 2025, and production capacity is expected to reach about 120 million kilowatts by 2030 59–61 . The growing integration of wind and solar power into the grid escalates the demand for pumped storage in the power system. However, economic considerations significantly impact the feasibility of constructing pumped storage facilities in abandoned mines, hence necessitating comprehensive cost-benefit analyses in the early stages to assess their viability and economic rationale. Comparison of investment costs of new pumped storage power stations and conventional pumped storage power stations (1) Economic construction costs The construction of conventional pumped storage power stations is restricted by various factors such as topography, land occupation, engineering costs, and ecological environmental protection, especially in the cities of the North China Plain, where finding natural high-drop terrain conditions suitable for surface pumped storage power stations is difficult. However, abandoned mines, resulting from resource exploitation, perfectly meet this site selection condition. After mineral resource extraction, vast underground spaces are formed. The rational utilization of this space for the new pumped storage power station's ground, lower reservoir, and equipment storage warehouse not only effectively reduces the construction costs of surface and underground reservoirs but also provides natural elevation differences and ample water resources. This creates favorable conditions for potential energy and geographic features for the new pumped storage power station to treat urban sewage, thereby realizing efficient space resource utilization. Presently, the investment standard for conventional pumped storage power stations ranges from 5,000 to 6,000 yuan/kW, whereas investment in pumped storage power stations based on abandoned mine transformation is around 3,000 yuan/kW 62,63 . It is evident that abandoned mine pumped storage power stations not only satisfy societal development needs but also consider ecological and economic benefits. (2) Water resources costs On water resources protection, traditional pumped storage power stations experience significant evaporation and leakage due to their primary working cycle being located on the surface. In contrast, abandoned mine pumped storage power stations are mainly underground, which largely avoids water evaporation caused by direct sunlight or harsh environmental conditions, thus reducing the waste of water resources. Additionally, a steady stream of sewage input ensures the stable operation of the pumped storage power station 64 . Comprehensive economic benefits of multi-energy complementary utilization of abandoned mines Power generation efficiency Under the comprehensive utilization of solar energy, wind energy, and other renewable resources in abandoned mines, it is estimated that 1 MW of photovoltaic power generation requires an area of 2 to 2.67 hectares, with the upper reservoir covering 0.75 hectares. Therefore, it can be estimated that a photovoltaic power station with a capacity of 0.33 MW can be constructed. Based on the installed capacity of photovoltaic power generation of 0.33 MW, operating at an actual efficiency of 70%, and generating power continuously for 10 hours per day, it is projected to produce 8.4×10 5 kW·h of electricity annually 65,66 . Effluent treatment benefits Sewage, encompassing various organic, inorganic, and microbial substances generated from urban living and industrial activities, poses significant challenges in treatment due to its complex composition. Conventional sewage treatment processes involve extensive use of electrical equipment and high power consumption, leading to substantial direct production costs and contributing significantly to overall energy consumption in water treatment plants 67–69 . The utilization of pumped storage in abandoned mines presents a sustainable solution, enabling a green and efficient production cycle encompassing power generation, sewage treatment, and tap water supply. Proper treatment of urban industrial and domestic wastewater in these facilities yields significant circular economic benefits. Additionally, repurposing the land surrounding abandoned mines for the construction of solar photovoltaic power stations facilitates self-consumption and electricity production, leveraging clean energy sources to achieve sustainable energy practices. Moreover, sewage treatment in abandoned mines mitigates carbon dioxide, ammonia, and chlorine emissions, effectively reducing air pollution levels 70 . Environmental Benefits Thermal power plants emit significant amounts of harmful gases, including carbon dioxide, sulfur dioxide, and nitrogen oxides. In comparison, abandoned mine pumped storage power stations emit substantially fewer harmful gases while generating the same amount of power. Consequently, deploying abandoned mine pumped storage stations allows for a reduction in the construction of thermal power plants of equivalent capacity, thereby greatly mitigating nitrogen oxide emissions. Leveraging its environmentally friendly attributes, renewability, and low energy consumption, pumped storage technology enhances the energy mix, fosters sustainable national economic development, and promotes the creation of a green, low-carbon society 71–73 . Research on seismic mechanism of underground reservoir in abandoned mine During operation, the underground reservoir of a coal mine is constantly subjected to dynamic loads, such as mining activities near the working face, roof collapses in goaf areas, mine-induced seismic events, and regional earthquakes, all of which pose threats to the safety and stability of the reservoir's underground roadways. Therefore, studying its seismic performance is essential to ensure the safety of coal mine underground reservoir projects. Influencing factors of earthquake-induced underground reservoirs in abandoned mines Research into the mechanisms of reservoir-induced earthquakes in China commenced in the 1980s. It was discovered that under specific conditions, reservoirs can alter seismic activities in their vicinity. Factors such as the structural geology, hydrogeological characteristics, tectonic stress accumulation, fault distribution, pore water pressure, and the physical and chemical effects of reservoir water on rock composition are crucial considerations for earthquake occurrence 74–76 . Based on the aforementioned research, it is evident that seismic activity in underground reservoirs of abandoned mines is intricately linked to water presence within the reservoir. Whether the impoundment of the reservoir can induce seismic activity hinges upon the environmental conditions present in the dam area. Current understanding suggests that these conditions can be broadly categorized into two groups: reservoir water infiltration and seismic tectonic conditions. Geologically, permeability represents a static factor predominantly determined by rock properties and their arrangement, while seismic conditions denote dynamic factors reflecting the contemporary tectonic activity of a region. (1) Permeation conditions Water in the Earth's crust exhibits permeability and capillary effects. Reservoir impoundment penetrates the original discontinuous micro-fractures in the reservoir bedrock, altering the stress state of the rock and inducing liquid flow and fracture deformation. This process significantly enhances permeability with increasing pore water pressure. Furthermore, the change in groundwater level due to the water body's forced load on the rock mass in the reservoir area markedly augments the elastic stress of the reservoir foundation. This not only alters the stress state of the bedrock but also elevates pore pressure, modifying the frictional resistance of fracture surfaces. Consequently, the shear strength of weak structural planes is reduced, leading to rock mass displacement—a necessary condition for reservoir-induced seismicity. Clearly, a pathway for reservoir water infiltration must exist. As fracture channels gradually develop to depth, stress corrosion and elastic deformation of the reservoir base cause local stress imbalances, resulting in microseismic activities within the reservoir area 77,78 . (2) Conditions of earthquake occurrence The power source generated by a reservoir results from the combined influence of the original stress field in the rock body before impoundment and the additional stress field post-impoundment. As reservoir water permeates the ground, it releases strain energy through weak surfaces, triggering induced seismic events. These weak surfaces, known as seismic structures or active faults, serve a dual function in reservoir-induced earthquakes: they act as pathways for reservoir water infiltration and as sites for induced seismicity. Thus, active faults constitute an indispensable environmental factor in water-induced earthquakes 79 . Fig. 9 illustrates the seismic factors influencing the reservoir and their interrelations. It is evident that the occurrence of reservoir-induced earthquakes post-impoundment depends not only on reservoir-specific factors such as water depth, capacity, and layout but also on surrounding environmental variables and their collective conditions. Therefore, a thorough analysis of these factors is crucial for making informed assessments regarding the likelihood of reservoir-induced seismicity. Analysis of seismic stability of underground reservoirs in abandoned mines The stress analysis illustrated in Fig. 10 reveals the pressures acting on the roadway wall within the underground reservoir of the abandoned mine. This analysis demonstrates that the roadway wall experiences a composite influence, including overlying rock pressure, water storage pressure, lateral pressure from surrounding rock masses in the goaf, and the impact force from water body displacement due to expansive rock mass movement, seismic activity, or mine-related tremors. Therefore, ensuring the safety and stability of the roadway under such unique working conditions is imperative 80–82 . The mechanical model depicted in Figure 11 elucidates the displacement and progressive failure dynamics of the roadway when subjected to seismic activity. From Fig. 11. it is evident that seismic loading induces stress concentration at the reservoir bottom, resulting in substantial displacement and damage to the roadway. Reinforcement scheme of underground reservoir of abandoned mine When the seismic performance of the underground reservoir in an abandoned mine fails to meet safety production standards, seismic reinforcement treatment becomes necessary. Existing engineering experience suggests three main methods for reinforcing underground reservoirs: replacement, enhancement, and pressurization 83,84 . While these methods can enhance seismic resistance, they may still fall short in improving the seismic performance of abandoned mine reservoirs. Therefore, the following reinforcement schemes are proposed to further enhance the seismic resilience of such reservoirs. (1) When repurposing abandoned mines for hydropower stations, unused roadways must be backfilled to optimize space utilization. Typically, materials such as flocculating agents, plugging agents, clay, stone, cement, and sawdust are used for backfilling. Additionally, plastic concrete may be added to better accommodate rock mass deformation, significantly reducing wall stress and preventing cracking. (2) To ensure that the strength and permeability of the rock mass beneath the reservoir meet standards, anti-seepage measures are implemented on the mine roadway floor. Primarily, cement grouting is employed for the anti-seepage treatment of the reservoir foundation. In areas where erosion is detected on roadway rock walls or hollowed bottom plates, the affected sections are chiseled until fresh concrete is exposed, after which concrete soil is reapplied to enhance reservoir wall stability. Conclusions Currently, research and engineering practices related to pumped storage power generation from abandoned mines, underground reservoir treatment and construction, and mine sewage treatment in China remain in an exploratory and preliminary stage. Systematic theoretical methodologies and technical specifications have yet to be established in these areas, highlighting the need for widespread attention. Advancements in theory, technology, engineering demonstration, and promotion within these domains hold the potential to not only facilitate effective energy storage and power generation but also foster new growth opportunities within China's renewable energy sector. This paper proposes a comprehensive construction and operation scheme for abandoned mines, leveraging the functionalities and characteristics of pumped storage power stations and sewage treatment, leading to the following conclusions and policy implications: (1) The underground reservoir of a pumped storage power station constitutes a vast system with multiphase and multi-physics coupling, encompassing factors such as the stability of surrounding rock, reservoir capacity, and groundwater dynamics. This study introduces an integrated approach, beginning with the design phase of three types of power stations—pumped storage, wind power, and photovoltaic—to effectively propose a combined technology involving mine sewage treatment plants and pumped storage power generation. This approach simultaneously addresses multiple objectives, including mine water storage, power generation, sewage treatment, and new energy development. The model presents favorable conditions for the establishment and utilization of multi-energy complementary systems, demonstrating feasibility in constructing pumped storage power stations and sewage treatment plants within a multi-energy complementary framework. Such initiatives contribute to subsidence control, ecological balance maintenance in mining areas, and offer far-reaching implications for modern and ecologically sustainable mining, energy efficiency, emission reduction, and green development initiatives. (2) The reuse of abandoned mine resources serves as the cornerstone for transforming resource-depleted regions. Simultaneously, by repurposing abandoned mines for the construction of pumped storage power stations and utilizing both above and below-ground reservoirs for urban sewage treatment, this approach breaks through traditional construction modes and land use concepts associated with "abandoned mine construction pumped storage power stations". This innovative model integrates photovoltaic and wind power stations with pumped storage systems, addressing not only the functional demands of sewage treatment plants but also achieving secondary development goals for abandoned mines. It offers fresh perspectives for establishing environmentally friendly, low-carbon, energy-saving, and sustainable underground sewage treatment plant models in abandoned mine areas. (3) Underground reservoir-induced earthquakes are contingent upon a specific combination of environmental factors, namely infiltration and seismic conditions. Furthermore, these factors are intricately linked and essential in the seismic induction process. Introducing the concept of the safety factor for coal mine reservoirs, this study theoretically analyzes the seismic safety performance of coal pillar roadways and proposes reinforcement schemes. Additionally, it underscores the need to explore the impact of various seismic wave types on the safety of underground reservoir roadways in coal mines. Moreover, the presence of sewage in the underground reservoir poses a threat to the structural integrity of coal pillar roadways, necessitating a comprehensive safety evaluation of their stability under sewage storage conditions. (4) Research on utilizing abandoned mines to construct underground reservoirs for pumped storage power stations is in its nascent stages, with a lack of experience in design and construction. Leveraging abandoned mines for this purpose, particularly in treating urban sewage, offers potential benefits for ecological restoration and urban sustainability. However, challenges arise due to the intricate nature of underground spaces and the complexity of urban sewage composition. Notably, hydraulic issues in underground reservoirs are prominent. It is recommended that subsequent research actively address these hydraulic challenges while exploring related fields, thereby offering scientific guidance and ensuring the safe construction of underground reservoirs for pumped storage power stations. (5) After a mine is abandoned, there often remain abundant usable resources, but a lack of awareness regarding reuse persists. Pumped storage power plants have proven to be sustainable, cost-effective energy storage solutions that hold great potential in advancing various renewable energy sources. Relevant departments should establish and improve abandoned mine management organizations and devise reuse plans prior to mine closure. Meanwhile, mining enterprises should effectively leverage technical reserves and strategies to facilitate the reuse and multifunctional utilization of abandoned mines, promoting environmental restoration and economic recovery in mining areas. Declarations All data are included in this article, and any further information will be made available from the corresponding author on reasonable request. Author contributions Designed the study: All authors, field works and samples collection: B.W.; L.G.; H.Z., Writing—original draft preparation, all authors. Writing—review and editing, B.W.; L.G. Funding acquisition, H.Z., all authors commented on previous versions of the manuscript. All authors read and approved the final manuscript. Funding This research was funded by the National Science Fund (NO. 51474220) and the National Natural Science Foundation Youth Fund Project (NO. 51804222). Data Availability All data are included in this article, and any further information will be made available from the corresponding author on reasonable request. References Du, K., Xie, J., Khandelwal, M. & Zhou, J. Utilization Methods and Practice of Abandoned Mines and Related Rock Mechanics under the Ecological and Double Carbon Strategy in China—A Comprehensive Review. Minerals 12 , 1065 (2022). Lu, P. et al. Main challenges of closed/abandoned coal mine resource utilization in China. Energy Sources, Part A: Recovery, Utilization, and Environmental Effects 42 , 2822–2830 (2020). Sivakumar, N., Das, D., Padhy, N. P., Senthil Kumar, A. R. & Bisoyi, N. Status of pumped hydro-storage schemes and its future in India. Renewable and Sustainable Energy Reviews 19 , 208–213 (2013). 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A Review of Stability of Dam Structures in Coal Mine Underground Reservoirs. Water 16 , 1856 (2024). Chen, Z., Zhao, X., Han, Z., Ji, Y. & Qiao, Z. Reasonable Size Design and Influencing Factors Analysis of the Coal Pillar Dam of an Underground Reservoir in Daliuta Mine. Processes 11 , 2006 (2023). Shi, J., Ma, T. & Gao, L. Analysis of seismic performance of gravity dam based on ultra-high performance concrete reinforcement. IOP Conf. Ser.: Earth Environ. Sci. 560 , 012067 (2020). Xu, Q., Zhang, T., Chen, J., Li, J. & Li, C. The influence of reinforcement strengthening on seismic response and index correlation for high arch dams by endurance time analysis method. Structures 32 , 355–379 (2021). Additional Declarations No competing interests reported. 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14:38:06","currentVersionCode":1,"declarations":"","doi":"10.21203/rs.3.rs-6163578/v1","doiUrl":"https://doi.org/10.21203/rs.3.rs-6163578/v1","draftVersion":[],"editorialEvents":[],"editorialNote":"","failedWorkflow":false,"files":[{"id":79680536,"identity":"70a6f2ea-bedc-49ff-a1c4-c556bbdf7d7f","added_by":"auto","created_at":"2025-04-01 12:46:12","extension":"png","order_by":1,"title":"Figure 1","display":"","copyAsset":false,"role":"figure","size":54849,"visible":true,"origin":"","legend":"\u003cp\u003eInstalled capacity and proportion of pumped storage in China from 2010 to 2023\u003c/p\u003e","description":"","filename":"floatimage1.png","url":"https://assets-eu.researchsquare.com/files/rs-6163578/v1/b6896b5dfbc32e8e8dc92446.png"},{"id":79680538,"identity":"f17b4536-f6ce-44a0-b61b-ee9f47c2de82","added_by":"auto","created_at":"2025-04-01 12:46:12","extension":"png","order_by":2,"title":"Figure 2","display":"","copyAsset":false,"role":"figure","size":24715,"visible":true,"origin":"","legend":"\u003cp\u003eDistribution, scale and average construction cost of pumped storage power stations in China\u003c/p\u003e","description":"","filename":"floatimage2.png","url":"https://assets-eu.researchsquare.com/files/rs-6163578/v1/e206b6f5b1fde2c67a11381a.png"},{"id":79680539,"identity":"db074fdd-01e9-4811-8329-1ecab20fea87","added_by":"auto","created_at":"2025-04-01 12:46:12","extension":"png","order_by":3,"title":"Figure 3","display":"","copyAsset":false,"role":"figure","size":26357,"visible":true,"origin":"","legend":"\u003cp\u003eDistribution of installed capacity of pumped storage in China\u003c/p\u003e","description":"","filename":"floatimage3.png","url":"https://assets-eu.researchsquare.com/files/rs-6163578/v1/e01f7128b5ef8bb56f45ea1b.png"},{"id":79681432,"identity":"534e2dc1-177f-485e-bf64-d7c91ff2a477","added_by":"auto","created_at":"2025-04-01 12:54:12","extension":"png","order_by":4,"title":"Figure 4","display":"","copyAsset":false,"role":"figure","size":88862,"visible":true,"origin":"","legend":"\u003cp\u003eComprehensive utilization system of abandoned mine\u003c/p\u003e","description":"","filename":"floatimage4.png","url":"https://assets-eu.researchsquare.com/files/rs-6163578/v1/41f7ee77224fa4aa8e884426.png"},{"id":79680541,"identity":"5714297f-69f5-4f81-a0c6-da81752d6572","added_by":"auto","created_at":"2025-04-01 12:46:12","extension":"png","order_by":5,"title":"Figure 5","display":"","copyAsset":false,"role":"figure","size":83780,"visible":true,"origin":"","legend":"\u003cp\u003eUrban sewage treatment process\u003c/p\u003e","description":"","filename":"floatimage5.png","url":"https://assets-eu.researchsquare.com/files/rs-6163578/v1/526a80dfe5fbacd4aef45b50.png"},{"id":79680540,"identity":"b5f79248-70a3-49f6-8386-08199666f7c8","added_by":"auto","created_at":"2025-04-01 12:46:12","extension":"png","order_by":6,"title":"Figure 6","display":"","copyAsset":false,"role":"figure","size":68759,"visible":true,"origin":"","legend":"\u003cp\u003eSchematic diagram of the structure of an abandoned mine pumped storage power station\u003c/p\u003e","description":"","filename":"floatimage6.png","url":"https://assets-eu.researchsquare.com/files/rs-6163578/v1/6950fde16fe73d9c7db42a8c.png"},{"id":79680546,"identity":"623e0479-b4d9-48f3-a7f2-98ae2199a37c","added_by":"auto","created_at":"2025-04-01 12:46:12","extension":"png","order_by":7,"title":"Figure 7","display":"","copyAsset":false,"role":"figure","size":107471,"visible":true,"origin":"","legend":"\u003cp\u003eSchematic diagram of the structure of urban sewage treatment plant\u003c/p\u003e","description":"","filename":"floatimage7.png","url":"https://assets-eu.researchsquare.com/files/rs-6163578/v1/b72d17c85fb0ffc05ab5df9d.png"},{"id":79680555,"identity":"ead11cb8-3008-4ef9-9dcb-eb6c787fca44","added_by":"auto","created_at":"2025-04-01 12:46:12","extension":"png","order_by":8,"title":"Figure 8","display":"","copyAsset":false,"role":"figure","size":298354,"visible":true,"origin":"","legend":"\u003cp\u003eComprehensive utilization model diagram of abandoned mine\u003c/p\u003e","description":"","filename":"floatimage8.png","url":"https://assets-eu.researchsquare.com/files/rs-6163578/v1/a000812711f3a9089c77259a.png"},{"id":79681915,"identity":"0cf67bf6-65d6-46f0-82d0-2cbff1585f03","added_by":"auto","created_at":"2025-04-01 13:02:12","extension":"png","order_by":9,"title":"Figure 9","display":"","copyAsset":false,"role":"figure","size":114803,"visible":true,"origin":"","legend":"\u003cp\u003eRelation diagram of earthquake inducing factors of underground reservoir\u003c/p\u003e","description":"","filename":"floatimage9.png","url":"https://assets-eu.researchsquare.com/files/rs-6163578/v1/ff1ef9d1ba26f72bc2b0b51b.png"},{"id":79681440,"identity":"ea46c990-4a55-47b7-b650-20d59fef41cd","added_by":"auto","created_at":"2025-04-01 12:54:12","extension":"png","order_by":10,"title":"Figure 10","display":"","copyAsset":false,"role":"figure","size":81789,"visible":true,"origin":"","legend":"\u003cp\u003eSchematic diagram of the force of the underground reservoir roadway\u003c/p\u003e","description":"","filename":"floatimage10.png","url":"https://assets-eu.researchsquare.com/files/rs-6163578/v1/49c26ab86c57cf7397335cbd.png"},{"id":79681442,"identity":"f75d606b-b65a-4da5-b443-37afa30b7fa5","added_by":"auto","created_at":"2025-04-01 12:54:13","extension":"png","order_by":11,"title":"Figure 11","display":"","copyAsset":false,"role":"figure","size":20639,"visible":true,"origin":"","legend":"\u003cp\u003eMechanical model diagram of the underground reservoir\u003c/p\u003e","description":"","filename":"floatimage11.png","url":"https://assets-eu.researchsquare.com/files/rs-6163578/v1/a479472803af3ac44e9e6d5b.png"},{"id":81103878,"identity":"3c2d929c-3171-4450-bf6d-db3b9bb12ec5","added_by":"auto","created_at":"2025-04-22 09:17:26","extension":"pdf","order_by":0,"title":"","display":"","copyAsset":false,"role":"manuscript-pdf","size":2130318,"visible":true,"origin":"","legend":"","description":"","filename":"manuscript.pdf","url":"https://assets-eu.researchsquare.com/files/rs-6163578/v1/586666e6-d60e-4929-89d7-16a0c642a7b1.pdf"}],"financialInterests":"No competing interests reported.","formattedTitle":"Study on the seismic stability of urban sewage treatment and underground reservoir of abandoned mine pumped storage power station","fulltext":[{"header":"Introduction","content":"\u003cp\u003eChina's coal resources have been continuously exploited on a large scale for a long time. According to statistics, the number of abandoned mines worldwide has exceeded 1\u0026nbsp;million, and by 2030, China is expected to have 15,000 abandoned mines, with the number of closed and abandoned mines increasing daily\u003csup\u003e\u003cspan citationid=\"CR1\" class=\"CitationRef\"\u003e1\u003c/span\u003e\u003c/sup\u003e. After a mine is abandoned, it leaves behind considerable volumes of various forms of underground roadways and chambers. If these are not treated or reused, they can lead to serious water pollution and geological disasters\u003csup\u003e\u003cspan citationid=\"CR2\" class=\"CitationRef\"\u003e2\u003c/span\u003e\u003c/sup\u003e. Therefore, the rational utilization of space and water resources left by abandoned mines to achieve efficient secondary utilization of underground resources has been a long-standing challenge for China's coal industry.\u003c/p\u003e \u003cp\u003eSince 1960, R.D. Harza proposed the concept of utilizing underground or open-pit mines for building pumped storage power stations\u003csup\u003e\u003cspan citationid=\"CR3\" class=\"CitationRef\"\u003e3\u003c/span\u003e\u003c/sup\u003e. Successively, countries such as Austria, the United Kingdom, the United States, and China, among others, have repurposed abandoned mines for constructing pumped storage power stations\u003csup\u003e\u003cspan citationid=\"CR4\" class=\"CitationRef\"\u003e4\u003c/span\u003e\u003c/sup\u003e. This approach not only positively impacts disaster prevention and control in underground goafs but also contributes to the ecological restoration of mines. Economically, repurposing abandoned underground spaces reduces construction time and significantly lowers investment costs\u003csup\u003e\u003cspan citationid=\"CR5\" class=\"CitationRef\"\u003e5\u003c/span\u003e\u003c/sup\u003e. Simultaneously, urbanization has led to increased discharge of domestic sewage, necessitating measures for sewage recycling to address water shortages and pollution\u003csup\u003e\u003cspan citationid=\"CR6\" class=\"CitationRef\"\u003e6\u003c/span\u003e,\u003cspan citationid=\"CR7\" class=\"CitationRef\"\u003e7\u003c/span\u003e\u003c/sup\u003e. However, challenges persist in sewage treatment, including low inlet water concentration, suboptimal collection rates, and high operating costs, severely impeding sustainable socioeconomic development\u003csup\u003e\u003cspan citationid=\"CR8\" class=\"CitationRef\"\u003e8\u003c/span\u003e\u003c/sup\u003e. \"Energy conservation, carbon reduction, and efficiency enhancement\" are critical imperatives for urban sewage plants. Various countries, including the United States, the United Kingdom, and Japan, are developing underground sewage treatment plants, which have demonstrated favorable economic and social outcomes\u003csup\u003e\u003cspan citationid=\"CR9\" class=\"CitationRef\"\u003e9\u003c/span\u003e\u003c/sup\u003e. With decreasing costs associated with underground space development, the feasibility of underground sewage treatment plants is growing, aligning with the trend of modern metropolitan facilities moving underground. The construction of underground sewage treatment plants is well-suited to China's conditions of high population density, limited land availability, and climatic diversity. Therefore, as China enhances water environment governance, underground sewage treatment plants are poised for significant global development\u003csup\u003e\u003cspan citationid=\"CR10\" class=\"CitationRef\"\u003e10\u003c/span\u003e\u003c/sup\u003e.\u003c/p\u003e \u003cp\u003eIn summary, the pumped storage power station and urban sewage plant form a small integrated energy system with electricity, water, and carbon coupling and mutual influence\u003csup\u003e\u003cspan citationid=\"CR11\" class=\"CitationRef\"\u003e11\u003c/span\u003e\u003c/sup\u003e. Introducing a multi-energy complementary integrated energy system into the underground sewage treatment plant of an abandoned mine can effectively compensate for high energy consumption, playing a key role in improving the daily operation, energy conservation, and energy security of the underground sewage treatment plant\u003csup\u003e\u003cspan citationid=\"CR12\" class=\"CitationRef\"\u003e12\u003c/span\u003e\u003c/sup\u003e. Therefore, considering the vast underground space of coal mines, a strategic concept of transforming and upgrading abandoned mines and comprehensively utilizing underground space is proposed, including establishing pumped storage power stations, wind power stations, photovoltaic power stations, and urban sewage treatment plants. Treating urban sewage while storing water in abandoned mines can efficiently utilize the underground space of abandoned mines and overcome the site selection restrictions of conventional pumped storage power stations. Based on systematically collected hydrogeological data of abandoned mines in China, this paper sorts out the secondary development and utilization methods of abandoned mine underground space, comprehensively analyzing and demonstrating the feasibility of urban sewage treatment in abandoned mine pumped storage projects. It constructs a comprehensive utilization model of urban sewage treatment based on abandoned mine pumped storage power stations under regional conditions in China, which not only efficiently and reasonably utilizes underground resources of abandoned mines but also has certain reference and guiding significance for the ecological restoration of abandoned mines and urban sewage treatment.\u003c/p\u003e"},{"header":"Feasibility study of model system","content":"\u003cp\u003e\u003cstrong\u003eResearch status of pumped storage power stations in abandoned mines\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThe inception of pumped storage power stations in China dates back to 1968\u003csup\u003e13\u003c/sup\u003e. However, during that era, power shortages were the primary concern within the power system, overshadowing the regulatory potential of pumped storage stations. It wasn\u0026apos;t until 1980 that the expansion of power grids in Guangdong Province, North China, and East China accelerated, exposing the limited load regulation capacity of the existing power system as a bottleneck hindering economic development\u003csup\u003e14\u003c/sup\u003e. Presently, Japan boasts an in-service pumped storage capacity comprising 8.5% of its total installed power supply capacity, while Italy, Spain, Germany, and France range from 3.5% to 6.6%\u003csup\u003e15,16\u003c/sup\u003e. Fig. 1 illustrates the evolution of China\u0026apos;s total pumped storage capacity since 2010 and its contribution to the nation\u0026apos;s overall installed power capacity. Despite the rapid growth of new energy installations in China, a substantial gap persists when comparing the proportion of installed capacity to that of developed nations and China\u0026apos;s own pumped storage development targets.\u003c/p\u003e\n\u003cp\u003eBased on incomplete statistics gathered from public data sources such as Power China and local government websites, Fig. 2 illustrates the distribution, scale, and average construction costs of pumped storage power stations in China\u003csup\u003e17\u0026ndash;19\u003c/sup\u003e. By the conclusion of 2023, 43 pumped storage power stations had been completed and commissioned in China, boasting an aggregated installed capacity of 46.85GW. Fig. 3 provides a geographic breakdown of operational and under-construction pumped storage power stations across various provinces and regions nationwide. This portrayal reveals an uneven development landscape characterized by significant disparities in installed capacity. Currently, pumped storage power station development is predominantly concentrated in economically advanced eastern regions and central, northern, and northeastern China, where thermal power holds sway. Notably, provinces such as Guangdong, Zhejiang, Anhui, Hebei, and Fujian feature prominently in this regard. Conversely, the western provinces, including Xinjiang and Tibet, host only a sparse number of pumped storage facilities. Furthermore, pumped storage resources remain exceedingly scarce in other provinces\u003csup\u003e20\u003c/sup\u003e.\u0026nbsp;\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eResearch status of multi-energy complementary comprehensive utilization\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eWith China\u0026apos;s ongoing adjustments to its energy structure, the proportion of renewable energy sources, particularly wind and solar, has been steadily increasing\u003csup\u003e21\u003c/sup\u003e. However, wind and solar energy exhibit characteristics such as randomness, volatility, intermittency, seasonality, and regional disparities, leading to poor sustainability and stability of energy supply, thereby presenting significant challenges to grid integration\u003csup\u003e22,23\u003c/sup\u003e. To mitigate the impacts of these renewable sources on the power grid, large-scale energy storage solutions are essential\u003csup\u003e24,25\u003c/sup\u003e. Currently, mature energy storage technologies capable of large-scale power storage mainly include pumped storage and compressed air energy storage systems\u003csup\u003e25,26\u003c/sup\u003e. However, traditional ground-based installations for pumped storage and compressed air energy storage require stringent site selection criteria, necessitating abundant high-altitude energy storage space, which is limited in availability. Conversely, abandoned mines, abundant in various European and American countries due to their well-developed mining industries, offer vast underground spaces suitable for energy storage facility construction, making them pioneers in abandoned mine utilization\u003csup\u003e27,28\u003c/sup\u003e. Since the 1960s, the United States, the United Kingdom, Germany, and other European and American nations have conducted extensive research and practical applications concerning abandoned mines, yielding remarkable results. In contrast, China\u0026apos;s exploration into abandoned mine development commenced relatively late, constrained by factors such as complex mine geology and numerous partially closed mines. Initial efforts in this area have primarily focused on industrial experiments, including coal mine gas extraction, underground coal gasification, underground reservoir construction, and gas storage within abandoned mines\u003csup\u003e29,30\u003c/sup\u003e. Therefore, leveraging the hydrogeology of abandoned mines, along with their spatial resource conditions above and below ground, adjacency relationships between mines, and factors such as wind, solar, and other new energy sources, a paradigm of multi-energy complementarity and comprehensive utilization, notably pumped storage power generation within abandoned mines, has started to emerge\u003csup\u003e31\u0026ndash;34\u003c/sup\u003e. The schematic representation of the comprehensive utilization system of abandoned mines is depicted in Fig. 4.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eResearch status of urban sewage treatment\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eIn recent years, with the continuous advancement of urbanization, the discharge of urban domestic sewage has continued to grow, and the recycling of urban sewage has become an important measure to solve the problem of population water shortage and water environment pollution. However, the corresponding sewage treatment methods are lagging behind, which seriously restricts the sustainable development of social economy\u003csup\u003e35\u0026ndash;37\u003c/sup\u003e. It can be seen that strengthening urban sewage treatment is an important way to comprehensively enhance urban functions and improve public services.\u003c/p\u003e\n\u003cp\u003eFig. 5\u0026nbsp;illustrates the typical urban wastewater treatment process in China, comprising primary physical treatment, secondary biological treatment, and tertiary advanced treatment\u003csup\u003e38\u0026ndash;40\u003c/sup\u003e. Primary treatment involves units such as the grid, regulating tank, lifting pump, and primary sedimentation tank. The grid intercepts suspended solids, the regulating tank regulates and homogenizes water quality, and the lifting pump transfers sewage to the primary sedimentation tank for further sedimentation and filtration. Secondary treatment primarily employs microorganisms to remove organic matter, nitrogen, and phosphorus, mitigating CH\u003csub\u003e4\u003c/sub\u003e and N\u003csub\u003e2\u003c/sub\u003eO emissions while generating carbon emissions. Effluent from the biochemical tank undergoes secondary sedimentation for mud-water separation; the supernatant, typically containing microorganisms, nitrogen, and phosphorus, can serve as agricultural or irrigation water. The deposited sludge exhibits significant biochemical activity; a portion is recirculated to the biochemical tank via the reflux pump to maximize activity, while the remainder, along with sludge from the primary sedimentation tank, is directed to the biogas tank. Tertiary treatment utilizes adsorption, electrodialysis, reverse osmosis, and similar methods for comprehensive removal of organic matter, nitrogen, and phosphorus from secondary effluent, yielding tertiary effluent suitable for industrial miscellaneous reclaimed water.\u003c/p\u003e\n\u003cp\u003eThe current ground sewage treatment plants face various issues including air and noise pollution, wastage of land resources, and high operational costs. Consequently, underground sewage or reclaimed water plants are increasingly favored due to their ability to mitigate these challenges. The development of underground sewage treatment facilities aligns with the trend of modern metropolises moving public infrastructure underground\u003csup\u003e41,42\u003c/sup\u003e. Many countries, including China, the United States, the United Kingdom, and Japan, are actively developing such facilities, yielding positive economic and social outcomes. While underground sewage treatment plants offer benefits, they pose challenges such as increased energy consumption due to the need for ventilation and deodorization systems. The energy demands of underground plants surpass those of equivalent above-ground facilities, necessitating innovative power supply solutions to address this issue urgently\u003csup\u003e43\u0026ndash;45\u003c/sup\u003e.\u003c/p\u003e"},{"header":"Model performance evaluation","content":"\u003cp\u003e\u003cstrong\u003ePower generation and storage assessment\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eAfter a mine is abandoned, a large area of ground and underground space is left unused. This not only reduces the need for extensive dam construction during subsequent development but also results in cost savings. Additionally, the structure of photovoltaic power generation systems is straightforward, comprising only photovoltaic arrays, inverters, and combiner boxes. This simplicity streamlines the process of integrating photovoltaic energy storage devices, facilitating the timely storage and utilization of photovoltaic electricity through pumped storage stations. This approach promotes the efficient consumption of renewable energy while mitigating the environmental pollution associated with photovoltaic energy storage devices, thus contributing to the enhancement of the surrounding ecological environment. Furthermore, the incorporation of photovoltaic power into pumped storage power stations enhances their peak regulation capacity. In summary, utilizing abandoned mines for the construction of wind and photovoltaic pumped storage power stations represents a prudent choice concerning power grid operations, the utilization of renewable energy, ecological preservation, and economic viability.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eAssessment of sewage treatment\u003c/strong\u003e\u003cstrong\u003e\u0026nbsp;capacity\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThe operation of urban sewage treatment plants is directly related to treatment efficiency and costs. In the context of sewage treatment systems for pumped storage power stations, considerations include water treatment processes, carbon emissions, sewage classification, utilization, and available space in abandoned mines. This entails analyzing intake forecasts, pollutant concentrations, and water demand for the following day. Coordination of environmental protection objectives in sewage plant operation involves a comprehensive assessment of energy costs, carbon emissions, equipment maintenance, sewage reuse benefits, and environmental benefits related to water quality improvement, while meeting treatment standards and operational constraints\u003csup\u003e46,47\u003c/sup\u003e.\u003c/p\u003e\n\u003cp\u003eCompared to traditional sewage purification plants, the sewage treatment system of pumped storage power stations is equipped with a three-stage sedimentation tank before the regulating tank. This arrangement facilitates the natural sedimentation of large particles in the sewage, resulting in predominantly turbid colloids entering the regulating pool. This condition optimally prepares for subsequent coagulation, thereby reducing the required dosage of flocculants. The primary advantage lies in addressing energy consumption issues typically associated with sewage plants, consequently reducing operational costs\u003csup\u003e48\u0026ndash;50\u003c/sup\u003e.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eIntegrated technology model of urban sewage treatment by multi-energy complementary abandoned mine pumped storage powerstation\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eMulti-energy complementary power generation mode of abandoned mines\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThe abandoned mine pumped storage power station consists of two main components. The first part resembles a traditional pumped storage power station, operating on the principle of utilizing surplus power from the grid during periods of low demand to drive water turbine units in the lower reservoir\u003csup\u003e51,52\u003c/sup\u003e. This water is then pumped into the upper reservoir for energy storage. Conversely, during peak electricity demand, water from the upper reservoir is released to turn hydro-generator units in the lower reservoir, converting gravitational potential energy into electrical energy. The second part incorporates photovoltaic and wind power generation systems.\u003c/p\u003e\n\u003cp\u003eThe structure of the pumped storage power station is depicted in Fig. 6, illustrating the underground framework utilized for the construction of the pumped storage system and the ground structure for the wind photovoltaic power generation system\u003csup\u003e53,54\u003c/sup\u003e. The underground structure primarily comprises four components: the upper reservoir, the lower reservoir, the underground plant, and the waterway system. Leveraging the significant height difference between the underground mine void and the upper roadway void, the underground roadway and void serve as the lower reservoir, while the upper shaft roadway void is utilized as the upper reservoir. The plant accommodates various equipment, such as pump generators, turbines, generators, and related controls, and can be constructed within underground roadways and spaces. The waterway system includes a channel and a tailwater channel connecting the upper reservoir and the lower reservoir, with the main pipeline of the pumped storage power station typically situated in the mountain apart from the inlet and outlet. The construction of surface wind photovoltaic power stations primarily involves utilizing a large area of abandoned land in abandoned mines and selecting suitable areas for the installation of photovoltaic arrays and wind power generation. Solar panels, brackets, inverters, and box-type transformers are arranged in the photovoltaic array, with the azimuth angle determined by the terrain, slope, and inclination angle of the bracket installation in the abandoned mine\u003csup\u003e55\u003c/sup\u003e.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eSewage treatment mode of abandoned mine pumped storage power station\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eFig. 7 illustrates the structural layout of the sewage treatment plant. Equipped with various facilities such as regulating pools, secondary pools, and tertiary pools, the waste mine sewage treatment system not only satisfies the demand for sewage treatment and water collection but also offers flexibility for regulating water volume. Tailored to the characteristics of underground sewage treatment plants, advanced technologies including high-standard deodorization, ventilation, fire protection, efficient underground lighting, and emergency safety facilities ensure compliance with high effluent standards and promote energy efficiency. This approach presents a viable solution for upgrading underground wastewater treatment plants and enhancing effluent quality\u003csup\u003e56\u003c/sup\u003e.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eIntegrated operation mode of abandoned mine pumped storage power station\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eBased on the ground space resources, water resources, surrounding wind energy conditions, and photovoltaic conditions of the abandoned mine, a multi-energy complementary development and utilization design scheme suitable for pumped storage and sewage treatment can be proposed, as illustrated in Fig. 8.\u0026nbsp;\u003c/p\u003e"},{"header":"Spatial layout of the engineering model","content":"\u003cp\u003eThe pumped storage power station, a technology in use for over a century, stands as the most reliable, economical, and largest-scale energy storage solution\u003csup\u003e57,58\u003c/sup\u003e. Operating on the same principle as conventional pumped storage stations, the abandoned mine pumped storage power station employs surplus power, wind energy, solar energy, or other electricity from the grid for energy storage. During this process, water is pumped from a lower reservoir to an upper reservoir, representing the energy consumption phase. Subsequently, during peak electricity demand, water from the upper reservoir is discharged through a generator to the lower reservoir, converting potential energy into electrical energy. The distinguishing feature of the abandoned mine pumped storage power station lies in its lower reservoir, which utilizes underground waste spaces such as roadways and goafs. Additionally, both upper and lower reservoirs are designed as sewage treatment stations, maximizing space utilization and addressing the energy consumption challenges of sewage treatment plants.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eAnalysis of the comprehensive utilization benefits of abandoned mine pumped storage power station\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eWith the aim of \u0026quot;increasing the proportion of non-fossil energy\u0026quot; in China, a target of over 1.2 billion kilowatts of wind and solar installed capacity by 2030 has been proposed. This necessitates concurrent improvements in energy storage systems and security measures. It is anticipated that pumped storage capacity will exceed 62 million kilowatts by 2025, and production capacity is expected to reach about 120 million kilowatts by 2030\u003csup\u003e59\u0026ndash;61\u003c/sup\u003e. The growing integration of wind and solar power into the grid escalates the demand for pumped storage in the power system. However, economic considerations significantly impact the feasibility of constructing pumped storage facilities in abandoned mines, hence necessitating comprehensive cost-benefit analyses in the early stages to assess their viability and economic rationale.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eComparison of investment costs of new pumped storage power stations and conventional pumped storage power stations\u0026nbsp;\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003e(1) Economic construction costs\u003c/p\u003e\n\u003cp\u003eThe construction of conventional pumped storage power stations is restricted by various factors such as topography, land occupation, engineering costs, and ecological environmental protection, especially in the cities of the North China Plain, where finding natural high-drop terrain conditions suitable for surface pumped storage power stations is difficult. However, abandoned mines, resulting from resource exploitation, perfectly meet this site selection condition. After mineral resource extraction, vast underground spaces are formed. The rational utilization of this space for the new pumped storage power station\u0026apos;s ground, lower reservoir, and equipment storage warehouse not only effectively reduces the construction costs of surface and underground reservoirs but also provides natural elevation differences and ample water resources. This creates favorable conditions for potential energy and geographic features for the new pumped storage power station to treat urban sewage, thereby realizing efficient space resource utilization. Presently, the investment standard for conventional pumped storage power stations ranges from 5,000 to 6,000 yuan/kW, whereas investment in pumped storage power stations based on abandoned mine transformation is around 3,000 yuan/kW\u003csup\u003e62,63\u003c/sup\u003e. It is evident that abandoned mine pumped storage power stations not only satisfy societal development needs but also consider ecological and economic benefits.\u0026nbsp;\u003c/p\u003e\n\u003cp\u003e(2) Water resources costs\u003c/p\u003e\n\u003cp\u003eOn water resources protection, traditional pumped storage power stations experience significant evaporation and leakage due to their primary working cycle being located on the surface. In contrast, abandoned mine pumped storage power stations are mainly underground, which largely avoids water evaporation caused by direct sunlight or harsh environmental conditions, thus reducing the waste of water resources. Additionally, a steady stream of sewage input ensures the stable operation of the pumped storage power station\u003csup\u003e64\u003c/sup\u003e.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eComprehensive economic benefits of multi-energy complementary utilization of abandoned mines\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003ePower generation efficiency\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eUnder the comprehensive utilization of solar energy, wind energy, and other renewable resources in abandoned mines, it is estimated that 1 MW of photovoltaic power generation requires an area of 2 to 2.67 hectares, with the upper reservoir covering 0.75 hectares. Therefore, it can be estimated that a photovoltaic power station with a capacity of 0.33 MW can be constructed. Based on the installed capacity of photovoltaic power generation of 0.33 MW, operating at an actual efficiency of 70%, and generating power continuously for 10 hours per day, it is projected to produce 8.4\u0026times;10\u003csup\u003e5\u003c/sup\u003e kW\u0026middot;h of electricity annually\u003csup\u003e65,66\u003c/sup\u003e.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eEffluent treatment benefits\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eSewage, encompassing various organic, inorganic, and microbial substances generated from urban living and industrial activities, poses significant challenges in treatment due to its complex composition. Conventional sewage treatment processes involve extensive use of electrical equipment and high power consumption, leading to substantial direct production costs and contributing significantly to overall energy consumption in water treatment plants\u003csup\u003e67\u0026ndash;69\u003c/sup\u003e.\u0026nbsp;The utilization of pumped storage in abandoned mines presents a sustainable solution, enabling a green and efficient production cycle encompassing power generation, sewage treatment, and tap water supply. Proper treatment of urban industrial and domestic wastewater in these facilities yields significant circular economic benefits. Additionally, repurposing the land surrounding abandoned mines for the construction of solar photovoltaic power stations facilitates self-consumption and electricity production, leveraging clean energy sources to achieve sustainable energy practices. Moreover, sewage treatment in abandoned mines mitigates carbon dioxide, ammonia, and chlorine emissions, effectively reducing air pollution levels\u003csup\u003e70\u003c/sup\u003e.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eEnvironmental Benefits\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThermal power plants emit significant amounts of harmful gases, including carbon dioxide, sulfur dioxide, and nitrogen oxides. In comparison, abandoned mine pumped storage power stations emit substantially fewer harmful gases while generating the same amount of power. Consequently, deploying abandoned mine pumped storage stations allows for a reduction in the construction of thermal power plants of equivalent capacity, thereby greatly mitigating nitrogen oxide emissions. Leveraging its environmentally friendly attributes, renewability, and low energy consumption, pumped storage technology enhances the energy mix, fosters sustainable national economic development, and promotes the creation of a green, low-carbon society\u003csup\u003e71\u0026ndash;73\u003c/sup\u003e.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eResearch on seismic mechanism of underground reservoir in abandoned mine\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eDuring operation, the underground reservoir of a coal mine is constantly subjected to dynamic loads, such as mining activities near the working face, roof collapses in goaf areas, mine-induced seismic events, and regional earthquakes, all of which pose threats to the safety and stability of the reservoir\u0026apos;s underground roadways. Therefore, studying its seismic performance is essential to ensure the safety of coal mine underground reservoir projects.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eInfluencing factors of earthquake-induced underground reservoirs in abandoned mines\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eResearch into the mechanisms of reservoir-induced earthquakes in China commenced in the 1980s. It was discovered that under specific conditions, reservoirs can alter seismic activities in their vicinity. Factors such as the structural geology, hydrogeological characteristics, tectonic stress accumulation, fault distribution, pore water pressure, and the physical and chemical effects of reservoir water on rock composition are crucial considerations for earthquake occurrence\u003csup\u003e74\u0026ndash;76\u003c/sup\u003e.\u003c/p\u003e\n\u003cp\u003eBased on the aforementioned research, it is evident that seismic activity in underground reservoirs of abandoned mines is intricately linked to water presence within the reservoir. Whether the impoundment of the reservoir can induce seismic activity hinges upon the environmental conditions present in the dam area. Current understanding suggests that these conditions can be broadly categorized into two groups: reservoir water infiltration and seismic tectonic conditions. Geologically, permeability represents a static factor predominantly determined by rock properties and their arrangement, while seismic conditions denote dynamic factors reflecting the contemporary tectonic activity of a region.\u0026nbsp;\u003c/p\u003e\n\u003cp\u003e(1) Permeation conditions\u0026nbsp;\u003c/p\u003e\n\u003cp\u003eWater in the Earth\u0026apos;s crust exhibits permeability and capillary effects. Reservoir impoundment penetrates the original discontinuous micro-fractures in the reservoir bedrock, altering the stress state of the rock and inducing liquid flow and fracture deformation. This process significantly enhances permeability with increasing pore water pressure. Furthermore, the change in groundwater level due to the water body\u0026apos;s forced load on the rock mass in the reservoir area markedly augments the elastic stress of the reservoir foundation. This not only alters the stress state of the bedrock but also elevates pore pressure, modifying the frictional resistance of fracture surfaces. Consequently, the shear strength of weak structural planes is reduced, leading to rock mass displacement\u0026mdash;a necessary condition for reservoir-induced seismicity. Clearly, a pathway for reservoir water infiltration must exist. As fracture channels gradually develop to depth, stress corrosion and elastic deformation of the reservoir base cause local stress imbalances, resulting in microseismic activities within the reservoir area\u003csup\u003e77,78\u003c/sup\u003e.\u0026nbsp;\u003c/p\u003e\n\u003cp\u003e(2) Conditions of earthquake occurrence\u0026nbsp;\u003c/p\u003e\n\u003cp\u003eThe power source generated by a reservoir results from the combined influence of the original stress field in the rock body before impoundment and the additional stress field post-impoundment. As reservoir water permeates the ground, it releases strain energy through weak surfaces, triggering induced seismic events. These weak surfaces, known as seismic structures or active faults, serve a dual function in reservoir-induced earthquakes: they act as pathways for reservoir water infiltration and as sites for induced seismicity. Thus, active faults constitute an indispensable environmental factor in water-induced earthquakes\u003csup\u003e79\u003c/sup\u003e.\u003c/p\u003e\n\u003cp\u003eFig. 9\u0026nbsp;illustrates the seismic factors influencing the reservoir and their interrelations. It is evident that the occurrence of reservoir-induced earthquakes post-impoundment depends not only on reservoir-specific factors such as water depth, capacity, and layout but also on surrounding environmental variables and their collective conditions. Therefore, a thorough analysis of these factors is crucial for making informed assessments regarding the likelihood of reservoir-induced seismicity.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eAnalysis of seismic stability of underground reservoirs in abandoned mines\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThe stress analysis illustrated in Fig. 10 reveals the pressures acting on the roadway wall within the underground reservoir of the abandoned mine. This analysis demonstrates that the roadway wall experiences a composite influence, including overlying rock pressure, water storage pressure, lateral pressure from surrounding rock masses in the goaf, and the impact force from water body displacement due to expansive rock mass movement, seismic activity, or mine-related tremors. Therefore, ensuring the safety and stability of the roadway under such unique working conditions is imperative\u003csup\u003e80\u0026ndash;82\u003c/sup\u003e.\u003c/p\u003e\n\u003cp\u003eThe mechanical model depicted in Figure 11 elucidates the displacement and progressive failure dynamics of the roadway when subjected to seismic activity.\u0026nbsp;\u003c/p\u003e\n\u003cp\u003eFrom Fig. 11. it is evident that seismic loading induces stress concentration at the reservoir bottom, resulting in substantial displacement and damage to the roadway.\u0026nbsp;\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eReinforcement scheme of underground reservoir of abandoned mine\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eWhen the seismic performance of the underground reservoir in an abandoned mine fails to meet safety production standards, seismic reinforcement treatment becomes necessary. Existing engineering experience suggests three main methods for reinforcing underground reservoirs: replacement, enhancement, and pressurization\u003csup\u003e83,84\u003c/sup\u003e. While these methods can enhance seismic resistance, they may still fall short in improving the seismic performance of abandoned mine reservoirs. Therefore, the following reinforcement schemes are proposed to further enhance the seismic resilience of such reservoirs.\u003c/p\u003e\n\u003cp\u003e(1) When repurposing abandoned mines for hydropower stations, unused roadways must be backfilled to optimize space utilization. Typically, materials such as flocculating agents, plugging agents, clay, stone, cement, and sawdust are used for backfilling. Additionally, plastic concrete may be added to better accommodate rock mass deformation, significantly reducing wall stress and preventing cracking.\u003c/p\u003e\n\u003cp\u003e(2) To ensure that the strength and permeability of the rock mass beneath the reservoir meet standards, anti-seepage measures are implemented on the mine roadway floor. Primarily, cement grouting is employed for the anti-seepage treatment of the reservoir foundation. In areas where erosion is detected on roadway rock walls or hollowed bottom plates, the affected sections are chiseled until fresh concrete is exposed, after which concrete soil is reapplied to enhance reservoir wall stability.\u003c/p\u003e"},{"header":"Conclusions","content":"\u003cp\u003eCurrently, research and engineering practices related to pumped storage power generation from abandoned mines, underground reservoir treatment and construction, and mine sewage treatment in China remain in an exploratory and preliminary stage. Systematic theoretical methodologies and technical specifications have yet to be established in these areas, highlighting the need for widespread attention. Advancements in theory, technology, engineering demonstration, and promotion within these domains hold the potential to not only facilitate effective energy storage and power generation but also foster new growth opportunities within China's renewable energy sector. This paper proposes a comprehensive construction and operation scheme for abandoned mines, leveraging the functionalities and characteristics of pumped storage power stations and sewage treatment, leading to the following conclusions and policy implications:\u003c/p\u003e \u003cp\u003e(1) The underground reservoir of a pumped storage power station constitutes a vast system with multiphase and multi-physics coupling, encompassing factors such as the stability of surrounding rock, reservoir capacity, and groundwater dynamics. This study introduces an integrated approach, beginning with the design phase of three types of power stations\u0026mdash;pumped storage, wind power, and photovoltaic\u0026mdash;to effectively propose a combined technology involving mine sewage treatment plants and pumped storage power generation. This approach simultaneously addresses multiple objectives, including mine water storage, power generation, sewage treatment, and new energy development. The model presents favorable conditions for the establishment and utilization of multi-energy complementary systems, demonstrating feasibility in constructing pumped storage power stations and sewage treatment plants within a multi-energy complementary framework. Such initiatives contribute to subsidence control, ecological balance maintenance in mining areas, and offer far-reaching implications for modern and ecologically sustainable mining, energy efficiency, emission reduction, and green development initiatives.\u003c/p\u003e \u003cp\u003e(2) The reuse of abandoned mine resources serves as the cornerstone for transforming resource-depleted regions. Simultaneously, by repurposing abandoned mines for the construction of pumped storage power stations and utilizing both above and below-ground reservoirs for urban sewage treatment, this approach breaks through traditional construction modes and land use concepts associated with \"abandoned mine construction pumped storage power stations\". This innovative model integrates photovoltaic and wind power stations with pumped storage systems, addressing not only the functional demands of sewage treatment plants but also achieving secondary development goals for abandoned mines. It offers fresh perspectives for establishing environmentally friendly, low-carbon, energy-saving, and sustainable underground sewage treatment plant models in abandoned mine areas.\u003c/p\u003e \u003cp\u003e(3) Underground reservoir-induced earthquakes are contingent upon a specific combination of environmental factors, namely infiltration and seismic conditions. Furthermore, these factors are intricately linked and essential in the seismic induction process. Introducing the concept of the safety factor for coal mine reservoirs, this study theoretically analyzes the seismic safety performance of coal pillar roadways and proposes reinforcement schemes. Additionally, it underscores the need to explore the impact of various seismic wave types on the safety of underground reservoir roadways in coal mines. Moreover, the presence of sewage in the underground reservoir poses a threat to the structural integrity of coal pillar roadways, necessitating a comprehensive safety evaluation of their stability under sewage storage conditions.\u003c/p\u003e \u003cp\u003e(4) Research on utilizing abandoned mines to construct underground reservoirs for pumped storage power stations is in its nascent stages, with a lack of experience in design and construction. Leveraging abandoned mines for this purpose, particularly in treating urban sewage, offers potential benefits for ecological restoration and urban sustainability. However, challenges arise due to the intricate nature of underground spaces and the complexity of urban sewage composition. Notably, hydraulic issues in underground reservoirs are prominent. It is recommended that subsequent research actively address these hydraulic challenges while exploring related fields, thereby offering scientific guidance and ensuring the safe construction of underground reservoirs for pumped storage power stations.\u003c/p\u003e \u003cp\u003e(5) After a mine is abandoned, there often remain abundant usable resources, but a lack of awareness regarding reuse persists. Pumped storage power plants have proven to be sustainable, cost-effective energy storage solutions that hold great potential in advancing various renewable energy sources. Relevant departments should establish and improve abandoned mine management organizations and devise reuse plans prior to mine closure. Meanwhile, mining enterprises should effectively leverage technical reserves and strategies to facilitate the reuse and multifunctional utilization of abandoned mines, promoting environmental restoration and economic recovery in mining areas.\u003c/p\u003e "},{"header":"Declarations","content":"\u003cp\u003eAll data are included in this article, and any further information will be made available from the corresponding author on reasonable request.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eAuthor contributions\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eDesigned the study: All authors, field works and samples collection: B.W.; L.G.; H.Z., Writing\u0026mdash;original draft preparation, all authors. Writing\u0026mdash;review and editing, B.W.; L.G. Funding acquisition, H.Z., all authors commented on previous versions of the manuscript. All authors read and approved the final manuscript.\u0026nbsp;\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eFunding\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThis research was funded by the National Science Fund (NO. 51474220) and the National Natural Science Foundation Youth Fund Project (NO. 51804222).\u0026nbsp;\u003c/p\u003e\u003ch2\u003eData Availability\u003c/h2\u003e\u003cp\u003eAll data are included in this article, and any further information will be made available from the corresponding author on reasonable request.\u003c/p\u003e"},{"header":"References","content":"\u003col\u003e\n\u003cli\u003eDu, K., Xie, J., Khandelwal, M. \u0026amp; Zhou, J. 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The influence of reinforcement strengthening on seismic response and index correlation for high arch dams by endurance time analysis method. \u003cem\u003eStructures\u003c/em\u003e \u003cstrong\u003e32\u003c/strong\u003e, 355\u0026ndash;379 (2021).\u003c/li\u003e\n\u003c/ol\u003e"}],"fulltextSource":"","fullText":"","funders":[],"hasAdminPriorityOnWorkflow":false,"hasManuscriptDocX":true,"hasOptedInToPreprint":true,"hasPassedJournalQc":"","hasAnyPriority":false,"hideJournal":true,"highlight":"","institution":"","isAcceptedByJournal":false,"isAuthorSuppliedPdf":false,"isDeskRejected":"","isHiddenFromSearch":false,"isInQc":false,"isInWorkflow":false,"isPdf":false,"isPdfUpToDate":true,"isWithdrawnOrRetracted":false,"journal":{"display":true,"email":"[email protected]","identity":"researchsquare","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":true,"externalIdentity":"","sideBox":"","snPcode":"","submissionUrl":"/submission","title":"Research Square","twitterHandle":"researchsquare","acdcEnabled":true,"dfaEnabled":false,"editorialSystem":"","reportingPortfolio":"","inReviewEnabled":false,"inReviewRevisionsEnabled":true},"keywords":"Abandoned mine, Pumped storage power station, Multi-energy complementation, Sewage treatment, Seismic stability, Sustainable development","lastPublishedDoi":"10.21203/rs.3.rs-6163578/v1","lastPublishedDoiUrl":"https://doi.org/10.21203/rs.3.rs-6163578/v1","license":{"name":"CC BY 4.0","url":"https://creativecommons.org/licenses/by/4.0/"},"manuscriptAbstract":"\u003cp\u003eAs coal’s share in primary energy consumption wanes, the annual increase in abandoned coal mines presents escalating safety and environmental concerns. This paper delves into cutting-edge models and attributes of integrating pumped storage hydropower systems with subterranean reservoirs and advanced wastewater treatment facilities within these decommissioned mines. By utilizing the expansive underground voids left by coal extraction, this method aims to achieve multifaceted objectives: efficient energy storage and generation, reclamation of mine water, and treatment of urban sewage. The research enhances the development and deployment of pumped storage technology in the context of abandoned mines, demonstrating its potential for fostering sustainable energy solutions and optimizing urban infrastructure. This study not only facilitates the progressive transformation and modernization of energy cities but also provides crucial insights for future advances in ecological mining practices, energy efficiency, emission mitigation, and green development strategies in the mining industry.\u003c/p\u003e","manuscriptTitle":"Study on the seismic stability of urban sewage treatment and underground reservoir of abandoned mine pumped storage power station","msid":"","msnumber":"","nonDraftVersions":[{"code":1,"date":"2025-04-01 12:46:07","doi":"10.21203/rs.3.rs-6163578/v1","editorialEvents":[{"type":"communityComments","content":0}],"status":"published","journal":{"display":true,"email":"[email protected]","identity":"researchsquare","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":true,"externalIdentity":"","sideBox":"","snPcode":"","submissionUrl":"/submission","title":"Research Square","twitterHandle":"researchsquare","acdcEnabled":true,"dfaEnabled":false,"editorialSystem":"","reportingPortfolio":"","inReviewEnabled":false,"inReviewRevisionsEnabled":true}}],"origin":"","ownerIdentity":"862c4948-aa6b-485b-8c96-b04789347d76","owner":[],"postedDate":"April 1st, 2025","published":true,"recentEditorialEvents":[],"rejectedJournal":[],"revision":"","amendment":"","status":"posted","subjectAreas":[{"id":46184290,"name":"Earth and environmental sciences/Environmental sciences/Environmental impact"},{"id":46184291,"name":"Earth and environmental sciences/Environmental social sciences/Energy and society"},{"id":46184292,"name":"Earth and environmental sciences/Environmental social sciences/Sustainability"}],"tags":[],"updatedAt":"2025-04-22T09:09:16+00:00","versionOfRecord":[],"versionCreatedAt":"2025-04-01 12:46:07","video":"","vorDoi":"","vorDoiUrl":"","workflowStages":[]},"version":"v1","identity":"rs-6163578","journalConfig":"researchsquare"},"__N_SSP":true},"page":"/article/[identity]/[[...version]]","query":{"redirect":"/article/rs-6163578","identity":"rs-6163578","version":["v1"]},"buildId":"8U1c8b4HqxoKbykW_rLl7","isFallback":false,"isExperimentalCompile":false,"dynamicIds":[84888],"gssp":true,"scriptLoader":[]}