Research on the Application of Cement-Soil Mixing Pile Technology in Soft Soil Foundation Reinforcement

Research on the Application of Cement-Soil Mixing Pile Technology in Soft Soil Foundation Reinforcement | Authorea try { document.documentElement.classList.add('js'); } catch (e) { } var _gaq = _gaq || []; _gaq.push(['_setAccount', 'G-8VDV14Y67G']); _gaq.push(['_trackPageview']); (function() { var ga = document.createElement('script'); ga.type = 'text/javascript'; ga.async = true; ga.src = ('https:' == document.location.protocol ? 'https://ssl' : 'http://www') + '.google-analytics.com/ga.js'; var s = document.getElementsByTagName('script')[0]; s.parentNode.insertBefore(ga, s); })(); Skip to main content Preprints Collections Wiley Open Research IET Open Research Ecological Society of Japan All Collections About About Authorea FAQs Contact Us Quick Search anywhere Search for preprint articles, keywords, etc. Search Search ADVANCED SEARCH SCROLL This is a preprint and has not been peer reviewed. Data may be preliminary. 21 January 2025 V1 Latest version Share on Research on the Application of Cement-Soil Mixing Pile Technology in Soft Soil Foundation Reinforcement Author : Jiangjiang Liu 0009-0000-3080-4593 [email protected] Authors Info & Affiliations https://doi.org/10.22541/au.173744173.33608872/v1 948 views 583 downloads Contents Abstract Information & Authors Metrics & Citations View Options References Figures Tables Media Share Abstract In engineering construction, soft soil foundations are common. Their characteristics of high water content, high compressibility, and low bearing capacity pose a serious threat to the stability and safety of buildings. To ensure the normal use of the superstructure, effective foundation reinforcement measures are essential. The cement-soil mixing pile technology forms a composite foundation with good strength and stability by forcibly mixing cement and foundation soil. It is outstanding in enhancing soil strength, reducing compressibility, and improving overall stiffness, and is widely used in engineering practice. This article starts from the principle of this technology and deeply explores its application and innovative ideas in soft soil foundation reinforcement, aiming to provide a reference for similar projects. Research on the Application of Cement-Soil Mixing Pile Technology in Soft Soil Foundation Reinforcement Author: Jiangjiang Liu Afflications: Guangzhou Construction Industry Research Institute Co., Ltd Abstract: In engineering construction, soft soil foundations are common. Their characteristics of high water content, high compressibility, and low bearing capacity pose a serious threat to the stability and safety of buildings. To ensure the normal use of the superstructure, effective foundation reinforcement measures are essential. The cement-soil mixing pile technology forms a composite foundation with good strength and stability by forcibly mixing cement and foundation soil. It is outstanding in enhancing soil strength, reducing compressibility, and improving overall stiffness, and is widely used in engineering practice. This article starts from the principle of this technology and deeply explores its application and innovative ideas in soft soil foundation reinforcement, aiming to provide a reference for similar projects. Keywords: Soft soil foundation reinforcement; Cement-soil mixing pile technology; Quality control 1. Introduction The acceleration of urbanization and the continuous advancement of infrastructure construction have brought an extremely urgent demand for soft soil foundation reinforcement. Traditional foundation treatment methods such as replacement method and preloading method can improve the foundation performance to a certain extent, but generally have disadvantages such as long construction period, high cost, and large environmental impact. The cement-soil mixing pile technology forms high-strength piles through a unique mixing process, effectively improving the bearing capacity and deformation modulus of the foundation. At the same time, it has the advantages of short construction period, low cost, and good environmental protection, which meets the needs of modern engineering construction and has important application value in the field of soft soil foundation reinforcement. 2. Principle of Cement-Soil Mixing Pile Technology The cement-soil mixing pile is a commonly used soft soil foundation reinforcement technology. Its principle is to use a special mixing machine to vigorously mix the cement slurry and soft soil within the pile body range to form a cement-soil mixture. During the construction process, the drill bit of the mixing pile machine cuts and breaks the soft soil, and the hollow mixing shaft simultaneously injects the cement slurry into the soil layer. After repeated shearing and mixing by the mixing head, the cement slurry and soft soil are evenly mixed. The hydration products generated by the cement hydration reaction fill the pores of the soft soil and cement the soil particles, enhancing the strength and stiffness of the soil. At the same time, the friction and interlocking between the cement particles and the soil particles and the spatial network structure formed by the cement stone effectively improve the deformation resistance of the composite soil and reduce the compressibility. The penetration and staggered distribution of many mixing piles improve the integrity and homogeneity of the soft soil foundation, relieve local stress concentration, and increase the overall bearing capacity and stability of the foundation. In addition, the construction process is vibration-free, noise-free, and pollution-free, which conforms to the green construction concept. 3. Application of Cement-Soil Mixing Pile Technology in Soft Soil Foundation Reinforcement 3.1 Project Overview A large coastal chemical plant project is located in the coastal plain with complex strata and weak underlying layers. The silt and muck are widely distributed in the site. The thickness of the silty soil layer is 3.5 - 6.7m, the natural water content is 38.2% - 54.7%, and the static cone penetration is 8 - 12, which is classified as highly compressible soft soil. The thickness of the underlying muck layer is 0.5 - 4.2m, the natural water content is 54.6% - 72.5%, and the static cone penetration is 10 - 16, which is also highly compressible muck. The static load test shows that the compression modulus of the soft soil is only 3.1 - 5.7MPa, and the characteristic value of the bearing capacity is 45 - 80kPa. If not treated, the foundation will have serious uneven settlement under the building load, endangering the structural safety. Considering the technical, economic and construction period factors, the project selected the cement-soil mixing pile technology to reinforce the foundation. 3.2 Design Scheme of Cement-Soil Mixing Pile According to the engineering geological and hydrogeological conditions of the site and combined with the structure, load and use requirements of the plant, the dry jetting method of cement-soil mixing pile technology is adopted in this project. The diameter of the mixing pile is 500mm, and the pile length is 8.5 - 12.0m, penetrating through the silty soil layer and the muck layer, and the pile end is placed on the underlying medium-dense fine sand layer. Considering the large load of the plant, the triple-tube rotary jetting process is used for the pile body. The outer pile diameter is 1200mm, the inner pile diameter is 800mm, and the core pile diameter is 500mm. Through the indoor mix proportion test, the cement content is determined to be 18%, the water-cement ratio is 0.6 - 0.7, and the unconfined compressive strength of the pile body reaches 2.5 - 3.2MPa after 28 days of curing, meeting the design requirements. The pile layout is square, the pile spacing is 1.5m, the ratio of pile diameter to pile spacing is 0.33, and the conversion area coefficient of the composite foundation is 0.54. The finite element numerical simulation shows that the equivalent deformation modulus of the composite foundation is 80 - 120MPa, the characteristic value of the bearing capacity is increased to 230 - 280kPa, and the deformation is within the allowable range. The specific design parameters are shown in Table 1. Mixing Pile Diameter (mm) 500 Mixing Pile Length (m) 8.5~12.0 Triple-tube Rotary Jetting Outer Pile Diameter (mm) 1200 Triple-tube Rotary Jetting Inner Pile Diameter (mm) 800 Triple-tube Rotary Jetting Core Pile Diameter (mm) 500 Cement Content (%) 18 Water-cement Ratio 0.6~0.7 Unconfined Compressive Strength of Pile Body (MPa) 2.5~3.2 Pile Spacing (m) 1.5 Ratio of Pile Diameter to Pile Spacing 0.33 Conversion Area Coefficient of Composite Foundation 0.54 Equivalent Deformation Modulus of Composite Foundation (MPa) 80~120 Characteristic Value of Bearing Capacity of Composite Foundation (kPa) 230~280 Based on the above design, the dry jetting method is used for construction, and the construction process and quality inspection are strictly controlled to ensure that the pile body quality and the performance of the composite foundation meet the standards, effectively control the settlement of the building and ensure the safety and applicability of the project. 3.3 Construction Process and Quality Control of Cement-Soil Mixing Pile The construction process of the dry jetting method in this project includes the positioning of the mixing pile machine, drilling, grouting and mixing, and lifting and mixing. During construction, the pile machine is first aligned with the pile position and vertically positioned, and the mixing shaft is drilled to the designed pile bottom elevation by self-weight and auger cutting. When the mixing shaft reaches 2m above the bearing layer, the cement slurry is pumped and injected into the soil through the high-pressure rotary jetting device, and at the same time, the mixing shaft is rotated for mixing. After reaching the pile bottom elevation, the mixing shaft is lifted to the ground surface at a speed of 0.5 - 0.8m/min to ensure that the pile body is evenly mixed. During the whole construction process, the amount of cement slurry and the mixing time are strictly controlled to ensure that the diameter and strength of the pile body meet the design requirements. The following measures are taken to ensure the construction quality: Raw Material Control: Ordinary Portland cement with a strength grade not lower than 42.5 is selected, with complete factory certificates, and the chloride ion content and soundness are qualified on site. The mixing water should be clean and pollution-free, and seawater is prohibited. Construction Process Control: A special mixing pile machine is used, and the vertical deviation of the mixing shaft is ≤1%, and the pile position deviation is ≤50mm. The automatic recorder is used to monitor the drilling speed (0.5 - 1.0m/min), the cement slurry injection volume (150 - 200L/m), the lifting speed (0.5 - 0.8m/min), the mixing time (≥5min/m) and other parameters to ensure that they meet the design requirements. See Table 2 for details. Table 2. Construction Parameter Table of Cement-Soil Mixing Pile Vertical Deviation of Mixing Axis ≤1% Pile Position Deviation (mm) ≤50 Drilling Speed (m/min) 0.5~1.0 Cement Slurry Injection Volume (L/m) 150~200 Lifting Speed (m/min) 0.5~0.8 Mixing Time (min/m) ≥5 Pile Quality Inspection: The pile diameter, pile length, pile integrity and pile strength are detected according to the design requirements. The pile diameter and pile length are measured by core drilling, the pile integrity is detected by the sonic transmission method, and the pile strength is measured by the uniaxial compressive strength of the core sample. The results should meet the design and specifications. At the same time, the load test of the composite foundation is carried out to ensure that the characteristic value of the bearing capacity and the deformation modulus meet the requirements. 4. Optimization and Innovation of Cement-Soil Mixing Pile Technology 4.1 Optimization of Material Proportion and Application of New Materials To improve the reinforcement effect and engineering performance of the cement-soil mixing pile, efforts are made from the optimization of material proportion and the application of new materials. The traditional cement-soil mix proportion design relies on empirical formulas and laboratory tests, and it is difficult to balance the economy and performance. In recent years, the optimization method based on orthogonal test and neural network has been used to explore the influence laws of cement content, water-cement ratio, curing time, etc. on the strength through multi-factor and multi-level orthogonal tests, and a nonlinear prediction model is constructed by combining neural network training to achieve optimization. For example, in a high-speed railway project, the optimization is carried out within the range of cement content of 15% - 25%, water-cement ratio of 0.5 - 0.8, and curing time of 3 - 28 days. The results are shown in Table 3. Table 3. Material Proportion Optimization Table Cement Content (%) 22 Water-cement Ratio 0.65 Curing Time (d) 14 Predicted Unconfined Compressive Strength (MPa) 3.5 Field verification shows that the unconfined compressive strength after 28 days of optimization reaches 3.2 - 3.8MPa, which is more than 20% higher than that of the traditional mix proportion. In addition, adding industrial waste residues such as fly ash and slag powder to the cement-soil can reduce the cost and improve the performance. Research shows that adding 30% fly ash can increase the compressive strength by 15% - 25% and the impermeability by 12 orders of magnitude; adding 45% slag powder can increase the compressive strength by 10% - 20% and the frost resistance by more than 30%. Nanomaterials have broad prospects in the modification of cement-soil. Adding 1% - 3% nano-SiO₂ can increase the compressive strength by 20% - 40% and the durability by more than 50%; adding 0.5% - 1% nano-CaCO₃ can increase the compressive strength by 15% - 30% and the frost resistance by 20% - 40%. Nanomaterials have a large specific surface area and high surface energy, which can fill pores, optimize the pore structure, promote cement hydration and crystal growth, and improve the mechanical properties and microstructure of cement-soil. 4.2 Research on Cement-Soil Mixing Pile Composite Foundation Technology The cement-soil mixing pile composite foundation technology forms a composite foundation by using the mixing pile and the soil between the piles to play the joint role of the pile and the soil and improve the bearing capacity and stability of the foundation. Its working mechanism includes pile reinforcement, compaction of the soil between the piles, and stress transfer between the pile and the soil. The pile bears the upper load and transfers it to the bearing layer. The soil between the piles is compacted to increase its strength and stiffness. The pile and the soil transfer stress and bear the load together through friction. Reasonable design of pile diameter, pile length and pile spacing is the key to playing the joint role. In an airport terminal project, the water content of the silty clay in the site is 40% - 60%, and the compression modulus is 36MPa. The design adopts a mixing pile with a diameter of 500mm and a length of 15m, and the pile spacing is 1.2m. The conversion area coefficient of the composite foundation is 0.55. Through indoor model and field static load tests, the variation laws of pile-soil stress ratio, pile side friction resistance and pile end resistance with pile diameter, pile spacing and load are obtained. See Table 4. Table 4. Test Table for the Application of Cement-Soil Mixing Pile Composite Foundation Technology 500 1.2 3.5~4.2 15~25 80~120 600 1.5 4.2~5.0 20~30 100~150 700 1.8 5.0~6.0 25~35 120~180 800 2.0 6.0~7.5 30~40 150~220 The results show that the larger the pile diameter and the smaller the pile spacing, the higher the pile-soil stress ratio and the greater the proportion of the pile load. Under the premise of ensuring the pile quality, optimizing the pile diameter and pile spacing can regulate the load sharing and give full play to the joint role. The project finally adopts a scheme with a diameter of 600mm and a spacing of 1.5m. The characteristic value of the bearing capacity of the composite foundation reaches 220kPa, and the deformation modulus is 25MPa, meeting the design requirements. In addition, setting auxiliary measures such as sand-gravel piles and plastic drainage boards in the composite foundation can accelerate consolidation and drainage and improve the overall performance. Research shows that setting sand-gravel piles can increase the degree of consolidation by 20% - 30% and the bearing capacity by 15% - 25%; setting plastic drainage boards can increase the degree of consolidation by 30% - 50% and the bearing capacity by 20% - 30%. 4.3 Numerical Simulation and Design Optimization of Cement-Soil Mixing Pile The design and construction quality of the cement-soil mixing pile is related to the safety and economy of the project. The traditional design is based on empirical formulas and simplified theories, and it is difficult to accurately consider the pile-soil interaction and anisotropy, resulting in conservative or unsafe results. With the development of numerical analysis technology, numerical simulation methods such as finite element and finite difference are used for refined design and optimization analysis, which has become an important means to improve the reinforcement effect and guide engineering practice. In a coastal expressway project, the subgrade is underlain by 30 - 50m thick soft soil layer, and the cement-soil mixing pile is used for reinforcement. The project uses the three-dimensional finite element software MIDAS GTS NX to simulate and analyze the composite foundation. First, a three-dimensional geological model including soft soil layer, medium-dense sand layer and mixing pile is constructed based on the geological exploration and laboratory test data. The modified Cambridge model and Mohr-Coulomb model are used to describe the constitutive relationships of the soft soil and the mixing pile respectively. The Contac element is used to simulate the pile-soil interface behavior. Then, 9 design schemes with pile diameters of 500mm, 600mm, 700mm and pile spacings of 1.2m, 1.5m, 1.8m are compared to obtain the relationships between pile diameter, pile spacing and settlement of the composite foundation and the overall stability safety factor. The simulation shows that the larger the pile diameter and the smaller the pile spacing, the smaller the settlement and the better the stability, but the cost increases. Under the premise of meeting the settlement and stability requirements, optimization algorithms such as genetic algorithm and particle swarm optimization algorithm are used to find the optimal combination to achieve the balance between the reinforcement effect and the cost. The project finally selects a scheme with a diameter of 600mm and a spacing of 1.5m. The settlement is controlled within 20cm, and the safety factor is 1.41, meeting the specifications. Based on the parametric model and intelligent optimization algorithm, a design optimization platform is established to quickly generate and compare design schemes and improve the design efficiency. 5. Conclusion The cement-soil mixing pile technology, as an effective means of soft soil foundation reinforcement, has significant advantages and is widely used. This article systematically expounds its technical principle and design method, and discusses in detail the key points of construction process and quality control. Combined with engineering cases, the application effect is analyzed. With the progress of science and technology, with the help of material optimization, process innovation and numerical simulation and other technologies, its reinforcement mechanism will be clearer, the design theory will be more perfect, and the construction effect will be more prominent. Looking forward to the future, this technology is expected to play an important role in more fields, promoting the development of soft soil foundation treatment technology and helping urban construction and infrastructure projects to reach a new level. References [1] Li Xueping. Application of Large-diameter Cement-soil Mixing Piles in Deep Soft Soil Subgrade [J]. Guangdong Building Materials, 2023, (12): 71-73. [2] Bai Yang, Jiang Chenbing, Zhao Di, Zhao Linghui, Zhu Haoyu. Application of Cement-soil Mixing Piles in Coastal Soft Soil Foundation Reinforcement [J]. Yellow River, 2022, (S2): 280-281. [3] Cao Chong. Discussion on the Construction Technology of Cement-soil Mixing Pile Foundation Pit Support [J]. Jiangxi Building Materials, 2020, (07): 172-173. [4] Chen Shengyuan, Zhang Weifeng, Wei Wei. Research Status and Development Prospect of Cement-soil Mixing Pile Technology [J]. Engineering Construction, 2020, (04): 6-10. Information & Authors Information Version history V1 Version 1 21 January 2025 Copyright This work is licensed under a Non Exclusive No Reuse License. Keywords cement-soil mixing pile technology quality control soft soil foundation reinforcement Authors Affiliations Jiangjiang Liu 0009-0000-3080-4593 [email protected] Guangzhou Construction Industry Research Institute Co Ltd View all articles by this author Metrics & Citations Metrics Article Usage 948 views 583 downloads .FvxKWukQNSOunydq8rnd { width: 100px; } Citations Download citation Jiangjiang Liu. Research on the Application of Cement-Soil Mixing Pile Technology in Soft Soil Foundation Reinforcement. Authorea . 21 January 2025. DOI: https://doi.org/10.22541/au.173744173.33608872/v1 If you have the appropriate software installed, you can download article citation data to the citation manager of your choice. Simply select your manager software from the list below and click Download. For more information or tips please see 'Downloading to a citation manager' in the Help menu . Format Please select one from the list RIS (ProCite, Reference Manager) EndNote BibTex Medlars RefWorks Direct import Tips for downloading citations document.getElementById('citMgrHelpLink').addEventListener('click', function() { popupHelp(this.href); return false; }); $(".js__slcInclude").on("change", function(e){ if ($(this).val() == 'refworks') $('#direct').prop("checked", false); $('#direct').prop("disabled", ($(this).val() == 'refworks')); }); Cited by Jiagui Xiong, Yangqing Gong, Xianghua Liu, Yan Li, Liangjie Chen, Cheng Liao, Chaochao Zhang, A PSO-XGBoost Model for Predicting the Compressive Strength of Cement–Soil Mixing Pile Considering Field Environment Simulation, Buildings, 15 , 15, (2740), (2025). https://doi.org/10.3390/buildings15152740 Crossref Loading... View Options View options PDF View PDF Figures Tables Media Share Share Share article link Copy Link Copied! 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