Simulation and Experiment of Self-adaptive Device for Hydraulic Support with Roadway Anchor Bolt

Simulation and Experiment of Self-adaptive Device for Hydraulic Support with Roadway Anchor Bolt | Research Square window.SnipcartSettings = { analytics: { enabled: false } }; (function() { var accessVector = localStorage.getItem('access_vector') || ''; window.dataLayer = window.dataLayer || []; if (accessVector) { window.dataLayer.push({ user: { profile: { profileInfo: { snid: accessVector } } } }); } })(); (function(w,d,s,l,i){w[l]=w[l]||[];w[l].push({'gtm.start':new Date().getTime(),event:'gtm.js'});var f=d.getElementsByTagName(s)[0],j=d.createElement(s),dl=l!='dataLayer'?'&l='+l:'';j.async=true;j.src='https://www.googletagmanager.com/gtm.js?id='+i+dl;f.parentNode.insertBefore(j,f);})(window,document,'script','dataLayer','GTM-K279D39R'); Browse Preprints In Review Journals COVID-19 Preprints AJE Video Bytes Research Tools Research Promotion AJE Professional Editing AJE Rubriq About Preprint Platform In Review Editorial Policies Our Team Advisory Board Help Center Sign In Submit a Preprint Cite Share Download PDF Article Simulation and Experiment of Self-adaptive Device for Hydraulic Support with Roadway Anchor Bolt Dong An, Zhiyang Wang, Hailiang Xu, Jiawei Tu, Runsong Tang This is a preprint; it has not been peer reviewed by a journal. https://doi.org/ 10.21203/rs.3.rs-8203278/v1 This work is licensed under a CC BY 4.0 License Status: Posted Version 1 posted You are reading this latest preprint version Abstract For the two support methods currently used in coal mine roadways, namely bolt support and hydraulic support, the supporting capacity of a single support method is limited under various complex conditions. The impact resistance of combined support is 30% − 50% higher than that of single support, which can improve the stability of coal mine roadways. However, the problems of stress concentration and impact damage caused by the protrusion of bolt ends in the collaborative operation of the hydraulic support-bolt support system have not been well solved so far.In this paper, an innovative hydraulic support top beam buffer ball device is designed, which well addresses this issue. Through laboratory tension-compression tests, the schemes of dense/loose nylon ball arrangements and the addition of rubber soft balls are compared. The data show that the loose nylon ball arrangement increases the total energy absorption by 77.8% more than the dense nylon ball arrangement. Furthermore, a finite element model is established using ABAQUS to simulate the mechanical response under impact load, verifying the effectiveness of the device. Physical sciences/Energy science and technology Physical sciences/Engineering Hydraulic support Anchor support Buffer ball device Impact ground pressure Finite element simulation Experimental study Figures Figure 1 Figure 2 Figure 3 Figure 4 Figure 5 Figure 6 Figure 7 Figure 8 Figure 9 Figure 10 Figure 11 Figure 12 Figure 13 Introduction Coal mine impact ground pressure 1 – 3 refers to the violent dynamic disaster phenomenon triggered by the sudden release of elastic deformation energy accumulated in the coal and rock bodies around the underground mining space 4 . This process is usually accompanied by explosive destruction of coal and rock bodies, material ejection, shock wave effect, abnormal gas outpouring, and other characteristics, and has become a very destructive type of geological disaster in deep coal mining. At the same time ofhigh technology and equipment to promote production capacity, as coal mines continue to mine to the depth, the complexity of geological conditions and the superpositioneffect of the mining stress field 5 , resulting in the frequency of this type of disaster trend and the intensity of destruction showed a significant increase in the situation.As the core equipment of a modernized mine tunnel support system, hydraulic support plays an irreplaceable role in guaranteeing the safety of mining operations and improving production efficiency. The traditional rigid support structure is difficult to adapt to the complex working conditions such as large deformation of the surrounding rock in the deep tunnel and high geostress, while the hydraulic support 6 , under its adaptive support characteristics, dynamically adjusts the support force through the hydraulic system, effectively controlling the deformation of the surrounding rock, and significantly improves the stability of the tunnel. As the core technology of active reinforcement of surrounding rock, anchor support 7 , 8 has become an important part of the modern mine tunnel support system by its unique advantage of “timely support and strengthening bearing”. Different from the traditional passive support method, the anchor rod is closely combined with the surrounding rock to form a “surrounding rock-anchor structure” synergistic bearing system, which significantly improves the self-supporting capacity of the rock body and effectively suppresses the deformation of the roadway. The introduction of innovative technologies such as prestressing anchor cable group and grouting modified cooperative support has promoted the development of anchor support from single reinforcement to the multi-dimensional prevention and control mode of “active pre-tensioning - dynamic reinforcement - peripheral rock modification” 9 .As shown in Fig. 1 .Two kinds of coal mine roadway support methods are very mature.It plays an important role in roadway surrounding rock support. It is difficult for a single support technology to meet the dynamic control demand of the “high intensity deformation and non-uniform load” of the surrounding rock in the roadway. Pan Yishan et al. 10 put forward the theory and technology of three-level support, and the synergistic mechanism of hydraulic support and anchor support has become a key technology path to realize the stability of the whole life cycle of the tunnel. Hydraulic bracing actively exerts a strong support force, rapidly suppresses the initial deformation of the surrounding rock, and balances the mining stress; anchor support is deep inside the rock, through the anchoring structure to mobilize the surrounding rock's self-supporting capacity, forming a “surface-deep” linkage of the composite load-bearing system. From preventing impact initiation to weakening impact damage, a systematic prevention and control chain is formed, significantly reducing the hazards of impact ground pressure on the roadway and personnel 11 . In roadway perimeter rock support projects, stress concentration from the protruding end of the anchor support system is a key hazard limiting support effectiveness. As shown in Fig. 2 , the anchor and hydraulic bracket support system under impact pressure causes uneven compression between the hydraulic bracket top plate and protruding anchor ends, distorting stress distribution. This effect intensifies when the exposed anchor length is excessive or pallet size mismatches, as collisions between anchor ends and the hydraulic bracket top plate exacerbate end stress concentration. The resulting high-stress zones induce micro-fractures in surrounding rock, accelerating fragmentation and weakening the anchoring system's overall bearing capacity. Stress concentration may also cause fatigue fracture of anchor thread sections or pallet deformation, reducing support reliability. Anchor damage caused by brackets is a frequent problem that seriously affects the reliability and engineering efficiency of the support system. After in-depth analysis, the cause of the problem covers both explicit and implicit dimensions: the explicit dimension is manifested in the direct contact between the bracket and the anchor, while the implicit dimension originates from the mismatch between the two stiffnesses, resulting in an imbalance in the force transfer mechanism. The solution strategies of “Dodging anchor” and “protecting anchor” are proposed. “Dodging anchor” reduces the physical contact conflict through spatial layout optimization or structural design avoidance; “protecting anchor” adjusts the bracket force pattern from the perspective of mechanical optimization, avoiding local stress concentration in the anchor and strengthening the protection mechanism. Its core adaptive goals focus on: adapting to the diversity of irregular anchor patterns,matching the complex conditions of uneven roof slabs, guaranteeing the uniform force on the roof beams to optimize the mechanical balance, and matching the geological characteristics of the rigidity of the roof slabs of the coal seams, so as to improve the overall adaptability and stability of the support system.The design idea of the device is shown in Fig. 3 . At present, there are three main types of bolt protection devices installed on the top beam of the hydraulic support, as shown in Fig. 4 . The first type is a sliding beam that slides by a guide rail, and an avoidance that matches the anchor rod or anchor cable is formed between adjacent raised structures. The advantage is that the structure is simple, and the adaptability to the regular row spacing anchors is good, but the disadvantage is that the top beam is under concentrated force; the second type is that the top beam is discretely arranged with single or multiple rows of top-connected hydraulic supports to form a flexible top-connected unit to achieve the function of avoiding the anchor. The advantage is that it has good adaptability to the irregular row spacing anchors and uneven roof plates. The disadvantage is that hydraulic control is required, the operation program is too complicated, the stability of the support is poor, and the top beam is under concentrated force. The third type is that the wire rope controls the support beam on the top beam of the hydraulic support, which has the advantage that Interrow spacing anchors have good adaptability and uniform stress distribution on top beams, but they are not suitable for high working resistance requirements. This paper designs a buffer ball device, which is installed inside the roof of the hydraulic support through a multi-stage buffer mechanism of nylon and rubber balls to prevent the end of the anchor rod from directly contacting the roof of the hydraulic support. The simulation software is used to analyze the 2D planar state of the device, observe the stress nephogram of the entire model movement under impact load, verify the theoretical feasibility of the device, and further verify the practical feasibility of the buffer ball device through hydraulic press experiments, providing a new idea for mine roadway support Design of the Roof Buffer Ball Device for Hydraulic Support The device is jacked vertically upward to simulate the contact between the hydraulic support and the rock stratum roof. By utilizing the mechanism of the buffer ball for adaptive position adjustment, the purpose of protecting the anchor bolt is achieved through adjusting the space and bearing part of the impact pressure. Energy transfer path: external load→nylon ball plastic deformation (energy consumption 30%) residual energy released through the stent hydraulic system, forming a “graded energy consumption - energy storage - energy drainage” chain 12 . Structural design of the buffer ball device The buffer ball device is arranged in the hydraulic bracket support top plate, the top plate is welded around by steel plate to form an uncovered groove, the internal uniform arrangement of three layers of buffer balls with a diameter of 50mm, the bottom of the 50mm rubber ball padding, the rubber ball on the uniform arrangement of the two layers of 50mm nylon ball, as shown in Fig. 5. Figure 5 Working principle of adaptive device The experiment of the Buffer ball device Experimental preparation of the buffer ball device According to the research purpose and research program of the buffer ball device, the laboratory tensile press was used to conduct experiments, and the tensile testing machine loaded the buffer ball at the elevating base plate, and after the load calculation, the 60t tensile testing machine was used to ensure the stability of the test loading. (1) Buffer ball device. The device is formed by welding a steel plate into an iron box, with an internal placement of white nylon balls and numbered for each ball, nylon ball diameter of 50mm. the test selected HRB500 left-hand threaded steel anchor, nominal diameter of 22mm, with the nut welded to an anchor disk used to prevent the anchor inserted into the device when the nylon ball was extruded out of the iron box. (2) 60 tons tensile testing machine. Its wide range of uses can be metal, non-metallic composite materials, tensile, compression, bending, shear, and other experiments. The use of a high-precision pressure transducer for force measurement the data collected more accurate, testing machine in Fig. 6 . (3) Overall assembly: Fix the anchor rod on the crossbeam of the tension-compression testing machine, and place the buffer ball device under the anchor rod to ensure that the anchor rod can be fully inserted into the buffer ball device when the testing machine controls the lift table to rise. The experimental setup is arranged as shown in Fig. 7 . Study of buffer ball arrangement programs (1) The buffer ball device is fully loaded with nylon balls: tight and loose arrangements are set up separately. The characteristics of the nylon balls in different arrangement modes are explored in depth. In the tight arrangement, the gap between the nylon balls is negligible, focusing on analyzing the uniqueness of the energy transfer path and cushioning mechanism in this state; in the loose arrangement, focusing on the influence of the relative motion space between the balls on the overall stability and cushioning efficiency of the bulk, analyzing in detail how the different arrangement 13 modes shape the spatial structure of the bulk and the characteristics of mechanical response, and accurately revealing the potential influence of the spatial distribution characteristics of the bulk on the cushioning performance. (2) Adding soft rubber balls to the buffer ball device: The arrangement of soft and hard staggered layers and the lower soft and upper hard layers is set up, respectively.the lower soft and upper hard layers is set up, respectively. Adding rubber balls can improve the performance of the adaptive adjustment of the buffe ball device as shown in Fig. 8 . For the soft-hard staggered layered arrangement, investigate the process of soft-hard ball synergy to achieve efficient cushioning when the force is applied in multiple directions, and analyze the energy distribution mechanism between the soft-hard balls in the force transfer path; for the lower soft-hard layered arrangement, focus on researching the initial resistance of the upper hard ball to the impact force and the subsequent energy absorption characteristics of the lower soft ball, and analyze the arrangement. In response to the different strengths and directions of the impact of the adaptive adjustment process, revealing its optimization of the buffer performance of the intrinsic mechanical principles, for the practical application of the buffer ball device to provide more targeted theoretical support. Analysis of experimental results Indicators for research and analysis $$\:E={\int\:}_{0}^{\delta\:-{\delta\:}_{0}}F\left(S\right)ds$$ $$\:{F}_{mean}=\frac{1}{\delta\:-{\delta\:}_{0}}{\int\:}_{0}^{\delta\:-{\delta\:}_{0}}F\left(S\right)ds$$ Full placement of hard nylon balls i) compact arrangement The test begins. The anchor rod is inserted into the buffer ball and comes into contact with the ball, the force on the anchor rod remains unchanged during the jacking of the loading bottom plate. After the anchor rod penetrates 46 mm into the box, the load suddenly increases, and a relatively loud noise occurs. It is speculated that the anchor rod directly hits the sphere.The spheres inside the box are relatively dense, and there is no room for adjustment. The load continues to increase without dropping back. When the load rises to 25 kN, the test is stopped.The anchor rod cannot be fully immersed in the box. ii)loose arrangement The test begins. The anchor rod is inserted into the loose sphere and makes contact with the sphere. the force on the anchor rod remains basically unchanged during the jacking of the bottom plate. After the anchor rod penetrates 80 mm into the box, the fluctuation of the load indicates the frictional contact between the anchor rod and the sphere. When the displacement of the bottom plate rises to 93 mm, the load rises slightly and then drops, and the sphere adjusts automatically under the extrusion of the anchor rod. When the displacement reaches 106 mm and 113 mm, the load experiences two rises and falls, and the extrusion contact of the anchor rod makes the arrangement of the spheres redistribute. It can be seen from the jacking displacement of the bottom plate and the photos that the anchor rod has fully penetrated into the box.As shown in Fig. 9 , the test of the anchor rod kept going deeper and deeper into the buffer ball, contacting the ball with friction and squeezing, and the ball automatically made adjustments to fit into the anchor space. As can be seen in the photos before and after the test, the 18th ball fell from the middle layer into the lower layer, the 20th ball squeezed the 23rd ball into the upper layer, the 34th ball fell from the upper layer into the lower layer, the 25th ball went from the outer ring to the inside, and the 29th ball position also changed. Adding rubber soft balls i) Hard and soft layering To investigate the adaptability of spherical structures under extreme conditions, a scenario is set where soft spheres and hard spheres are distributed completely randomly, with approximate considerations given to the packing of spheres at engineering sites. An empty box is taken, and two authors randomly place hard spheres and soft spheres into it without any restrictions on quantity, position, layer, or density until the box is full. When the loading base plate is jacked up, the force on the anchor rod remains constant; the load suddenly increases to a depth of approximately 80 mm to 100 mm in the box, after which the load continues to grow. ii) Layered arrangement with soft bottom and hard top The bottom of the box is all filled with rubber soft balls, and the upper part is filled with nylon balls to test the stratifiedarrangement situation with soft at the bottom and hard at the top.The anchor rod inserts into and contacts with the ball. When the loading floor is jacked up, the force on the anchor rod remains unchanged.After the anchor rod penetrates 100mm into the box, the load begins to suddenly increase, and continuously grows without falling back. When the load rises to 25kN, the test is stopped.All data is shown in Fig. 10 . As evidenced by the data presented in Table 1 , the loose arrangement demonstrates a 1.6% increase in the average bearing capacity (F mean ) and a 77.8% rise in total energy absorption (E) compared to the compact configuration, indicating a notable improvement in energy dissipation efficiency. The incorporation of rubber spheres leads to a marginal enhancement in the energy absorption performance of the device, which may be attributed to their viscoelastic characteristics. In the case of the randomized configuration comprising both hard and soft spheres, a 1.5% increase in F mean and a 13% rise in E are observed relative to the loose arrangement. For the layered configuration with hard spheres positioned above soft spheres, F mean is enhanced by 8.6% and E by 3.5% compared to the loose arrangement. Table 1 Performance indicators for different arrangements project \(\:\varvec{\delta\:}\) /mm \(\:{\varvec{\delta\:}}_{0}/\) mm E/J F mean/ KN compact 50.79 44 12.79 9.47 loose 131.3 106.3 57.6 9.63 hard and soft layering 127.6 91 66.23 9.78 soft bottom and hard top 115.3 91.8 59.7 10.54 Buffer ball device finite element simulation The finite element software ABAQUS 14 is used to establish a 2D planar finite element model for the buffer ball device, and the buffer ball device model is divided into four parts: rock layer, anchor rod, buffer ball, and top plate of the hydraulic support. The material parameters for the rock formation model are set as Table 2 : density of 2.46×10 3 kg/m 3 , elastic modulus of 19.5GPa, and Poisson’s ratio of 0.2. For the anchor rod material, the parameters are: density of 7.85×10 3 kg/m, modulus of elasticity is 210GPa, Poisson's ratio is 0.26, yield stress is 235Mpa; rubber ball material parameter setting density is 2.1×10 3 kg/m 3 , modulus of elasticity is 0.5GPa, Poisson's ratio is 0.4; nylon ball material parameter setting density is 1.15×10 3 kg/m 3 , modulus of elasticity is 3.5GPa, Poisson's ratio is 0.3, yield stress is 70Mpa; hydraulic bracket top plate material parameters are set to 7.85×10 3 kg/m 3 , elastic modulus is 210GPa, Poisson's ratio is 0.26, yield stress is 890Mpa. The length of both the rock layer and the top plate of the hydraulic support is 4000mm, and an anchor is arranged at an interval of 1000mm, and the Dynamic-Explicit algorithm is used to set the two analysis steps of movement and compression,with the movement step set at 0.2s, the compression step set at 0.1s, and the friction factor at 0.2. The rock layer is kept completely fixed, and the top plate of the hydraulic support underneath is constrained to move and rotate in the direction of x-axis and kept the top plate moving in y-axis direction, and set upward 24Mpa instantaneous pressure at the bottom of the hydraulic bracket top plate. Table 2 Material Properties part Density(kg/m 3) modulus of elasticity(Gpa) Poisson's ratio yield stres(Mpa) rock 2.46×10 3 19.5 0.2 anchor rod 7.85×10 3 210 0.26 235 rubber ball 2.1×10 3 0.5 0.4 nylon ball 1.15×10 3 3.5 0.3 70 hydraulic bracket top plate 7.85×10 3 210 0.26 890 Anchor force Analysis After completing the full-model simulation, the entire insertion process of the anchor rods into the buffer ball device was monitored. During insertion, the buffer ball continuously adjusts its spatial position through compressive deformation (compressive deformation). Relevant experimental data were collected, and the effectiveness of the device in preventing direct contact between the anchor rods and the hydraulic support top plate after the completion of pressure loading was verified 15 . In the simulation model, the three anchor rods were labeled as A-anchor, B-anchor, and C-anchor from left to right, respectively. The stress distribution nephograms of the three anchors at their respective maximum stress states were analyzed (Fig. 11 ). It is observed that the maximum stress of all three anchors is concentrated at the anchor-anchor rod connection interface, which is consistent with the mechanical characteristics of the assembled structure under impact loading. Time-stress curves of the three anchors were plotted based on the temporal evolution of stress during the simulation (Fig. 12 ). It is found that after 0.1 s, slight stress fluctuations occur in the anchors immediately after contact with the buffer ball, which is attributed to the initial contact interaction and elastic energy exchange between the anchor and the buffer ball. For the A-anchor, the stress begins to increase linearly at approximately 0.19 s. Further analysis of the time-stress curve of the A-anchor reveals that after 0.19 s, the stress exhibits a nonlinear steep rise, accompanied by multiple peaks and valleys within the time interval of 0.19–0.2 s. This phenomenon indicates that the initial spatial position of the buffer ball is not optimal; thus, after contact with the A-anchor, the buffer ball undergoes several rounds of fine adjustments (e.g., elastic deformation and displacement compensation) to redistribute the local stress concentration. During this process, the buffer ball absorbs impact energy through periodic elastic deformation, leading to an oscillatory decay trend of the anchor stress, which is a typical dynamic response of elastic buffer components under transient loading. For the B-anchor, the time-stress curve shows no significant peaks or valleys during the instantaneous compression stage. This is because the B-anchor achieves an optimal contact position with the buffer ball after the first compressive adjustment. When the overall structure stabilizes under impact loading, the stress on the B-anchor tends to flatten, indicating that the buffer ball can effectively dissipate impact energy and balance the stress distribution for anchors at the optimal contact position. The C-anchor exhibits 1–2 minor stress fluctuations within the 0.19–0.2 s interval, with an amplitude lower than that of the A-anchor. Subsequently, the maximum stress of the C-anchor undergoes a sudden sharp decrease followed by a continuous rise. A unique mechanism is proposed for this phenomenon: due to the large length span of the entire simulation model, the center of gravity of the system may shift slightly when the hydraulic support top plate moves upward again. After being subjected to instantaneous compression, the left A-anchor and the middle B-anchor bear most of the impact load, resulting in a stress decrease in the C-anchor after reaching its maximum stress value. Experimental verification shows that all three anchors avoid direct collision with the hydraulic support top plate under impact loading, which fully meets the core design requirement of the device. During the insertion of the anchors into the buffer ball device, the maximum stress of each anchor does not exceed the yield strength of the anchor material, ensuring the structural integrity and service safety of the anchors. In conclusion, the simulation results of the buffer ball device are consistent with the expected experimental theory and meet the structural design intent of the device. This study provides reliable theoretical support and experimental basis for the engineering application of the buffer ball device in hydraulic support systems. 16 Parameter Optimisations To investigate and optimize the parameters of the device for better buffering performance, several sets of buffer balls with different parameters were subjected to numerical simulations. The aim was to observe and analyze the effects of different parameters on the buffer ball device and identify a superior solution. First, balls with different elastic moduli were selected as experimental subjects. To ensure data uniformity, the simulation was set up for a single anchor rod, with balls having elastic moduli of 190 GPa, 200 GPa, 210 GPa, and 220 GPa, while other parameters remained unchanged. The maximum stress of the anchor rod was then observed. For data accuracy, each set of simulation experiments was repeated five times, and the average values were calculated, as presented in Table 3 . Table 3 Material Properties Modulus of elasticity(GPa) Group One(Mpa) Group Two(Mpa) Group Three(Mpa) Group Four(Mpa) Group Five(Mpa) Mean(Mpa) 190 208.9 204.3 207.1 203.3 212.8 207.3 200 203.4 205.9 203.2 204.1 203.6 204.0 210 195.5 198.7 195.3 197.1 196.2 196.6 220 232.9 234.7 232.2 232.9 231.0 232.7 It is worth noting that the elastic modulus does not present a monotonically linear relationship with the maximum stress. The material with an elastic modulus of 210 GPa may exhibit superior low-stress performance, which can be ascribed to its intrinsic mechanical propertie. These properties facilitate a more homogeneous stress distribution during finite element simulations, in accordance with the mechanics principle of stress propagation and equilibrium in composite systems. In contrast, the material with an elastic modulus of 220 GPa, due to its excessively high stiffness, is prone to stress concentration under loading conditions. This phenomenon violates the stress compatibility condition at the structural interfaces, thereby inducing a drastic escalation in the maximum stress, which is consistent with the theoretical prediction of stress concentration in high-modulus materials under constrained deformation,as illustrated in Fig. 13 . Advantages of the device (1) The buffer ball device is an independent mechanism capable of modular production. It offers greater versatility and ease of installation, allowing for free combination with any equipment having relevant requirements. Moreover, it does not necessitate modifications to the structure of the carrier equipment, ensuring that the structural strength of the carrier equipment remains unaffected. (2) When the avoidance device is interfaced with the hydraulic support, the connection is achieved through the engagement between the fixing pins welded to the lower surface of the beam and the mounting holes on the roof beam of the hydraulic support. These fixing pins not only serve as a connection mechanism but also directly bear the lateral forces exerted by the roadway roof plate, thereby protecting critical components“the hydraulic cylinders”from damage. Conclusion This study uses experiments and software simulation to verify the applicability and feasibility of the device, and the buffer ball structure of the device can well solve the problem that the collision between the anchor rod and the roof plate of the hydraulic bracket and the anchor support in the mine roadway under the situation of coordinated work of hydraulic bracket support and anchor support leads to the damage of the anchor rod by the force, which makes the anchor perimeter rock support effect ineffective. The main research results are as follows: (1) By analyzing the experimental data, the energy absorption index E of the loose arrangement of the buffer balls of this device is 77.8% higher than that of the compact arrangement, and the average force Fmean is increased by 1.6%, which should be avoided for the highly tight arrangement. (2) After the incorporation of rubber soft balls, the energy absorption effect of the device has been slightly improved. Through analysis, it is concluded that the random arrangement of hard and soft balls, which is closer to the on-site layout in construction, represents the optimal solution. (3) Based on the design principle of this hydraulic support roof device, more and better devices can be developed in the future by modifying the material and size of the spheres inside the device, as well as integrating other forms of support methods. Declarations Author contributions statement AD, XHL contributed to the conception of the study. WZY, TJW, TRS performed the experiment. AD, WZY contributed significantly to analysis and manuscript preparation. AD,WZY performed the data analyses and wrote the manuscript. All authors read the manuscript. Competing interests The authors declare no competing interests. Additional information Correspondence and requests for materials should be addressed to H.X. Funding Declaration This work was supported by the National Natural Science Foundation of China (No. 52427805). Author Contribution AD, XHL contributed to the conception of the study. WZY, TJW, TRS performed the experiment. AD, WZY contributed significantly to analysis and manuscript preparation. AD,WZY performed the data analyses and wrote the manuscript. All authors read the manuscript. Acknowledgement This work was supported by the National Natural Science Foundation of China (No. 52427805). Data Availability All data, models, or code that support the findings of this study are available from the corresponding author upon reasonable request. References Zhang, C. L., Wang, P. Z., Wang, E. Y., Chen, D. P. & Li, C. Characteristics of coal resources in China and statistical analysis and preventive measures for coal mine accidents. Int. J. Coal Sci. Technol. 10 (1), 22 (2023). Jiang, Y. D., Pan, Y. S., Jiang, F. X., Dou, L. M. & Ju, Y. State of the art review on mechanism and prevention of coal bumps in China. J. China Coal Soc. 39 (2), 205–213 (2014). Dou, L., Mu, Z., Li, Z., Cao, A. & Gong, S. Research progress of monitoring, forecasting, and prevention of rockburst in underground coal mining in China. Int. J. Coal Sci. Technol. 1 (3), 278–288 (2014). Zhang, Q. H. et al. A review of rockburst prevention and control methods in tunnels: graded and classified prevention and control. Bull Eng. Geol. Environ 83 (3), (2024). Wang, M. Z., Cai, M., Maloney, S. & Dunn, M. 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2","display":"","copyAsset":false,"role":"figure","size":84889,"visible":true,"origin":"","legend":"\u003cp\u003eSchematic diagram of the hydraulic support and anchor support system\u003c/p\u003e","description":"","filename":"2.jpg","url":"https://assets-eu.researchsquare.com/files/rs-8203278/v1/f875865c9f5f958e532696fc.jpg"},{"id":97557595,"identity":"a7675366-33e8-463a-bf61-91349d362be8","added_by":"auto","created_at":"2025-12-05 19:12:32","extension":"jpg","order_by":3,"title":"Figure 3","display":"","copyAsset":false,"role":"figure","size":136784,"visible":true,"origin":"","legend":"\u003cp\u003eSchematic principle diagram of the device design\u003c/p\u003e","description":"","filename":"3.jpg","url":"https://assets-eu.researchsquare.com/files/rs-8203278/v1/792b8a1385813b4528524233.jpg"},{"id":97557600,"identity":"8e3cbed0-823e-45c8-b770-b7e2151c934e","added_by":"auto","created_at":"2025-12-05 19:12:32","extension":"jpg","order_by":4,"title":"Figure 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device\u003c/p\u003e","description":"","filename":"5.jpg","url":"https://assets-eu.researchsquare.com/files/rs-8203278/v1/6f4d9296d101c34799bf1817.jpg"},{"id":97557610,"identity":"f885ddb3-81b0-4512-937d-c6762e64e2df","added_by":"auto","created_at":"2025-12-05 19:12:32","extension":"jpg","order_by":6,"title":"Figure 6","display":"","copyAsset":false,"role":"figure","size":159596,"visible":true,"origin":"","legend":"\u003cp\u003eExperimental preparation of buffer ball device (a) Steel plate welded iron box unit (b) Anchor rods and plate\u003c/p\u003e","description":"","filename":"6.jpg","url":"https://assets-eu.researchsquare.com/files/rs-8203278/v1/61efc4b88efb17c7398293c5.jpg"},{"id":97557609,"identity":"f8d133ab-3fc4-48fd-8fa6-fd24715343cc","added_by":"auto","created_at":"2025-12-05 19:12:32","extension":"jpg","order_by":7,"title":"Figure 7","display":"","copyAsset":false,"role":"figure","size":131041,"visible":true,"origin":"","legend":"\u003cp\u003eExperimental arrangement of buffer ball device\u003c/p\u003e","description":"","filename":"7.jpg","url":"https://assets-eu.researchsquare.com/files/rs-8203278/v1/568895c6d7cea790dc95c499.jpg"},{"id":97557605,"identity":"3ae6869e-eb0a-4adb-a986-8c2980b92031","added_by":"auto","created_at":"2025-12-05 19:12:32","extension":"jpg","order_by":8,"title":"Figure 8","display":"","copyAsset":false,"role":"figure","size":86038,"visible":true,"origin":"","legend":"\u003cp\u003eLayout of different arrangement schemes for buffer balls\u003c/p\u003e","description":"","filename":"8.jpg","url":"https://assets-eu.researchsquare.com/files/rs-8203278/v1/00a526659229e88b8d2216ad.jpg"},{"id":97557612,"identity":"c4a8b06d-143e-4ac1-8245-f60ee170437e","added_by":"auto","created_at":"2025-12-05 19:12:32","extension":"jpg","order_by":9,"title":"Figure 9","display":"","copyAsset":false,"role":"figure","size":114290,"visible":true,"origin":"","legend":"\u003cp\u003eDisplacement of labelled spheres after the experiment\u003c/p\u003e","description":"","filename":"9.jpg","url":"https://assets-eu.researchsquare.com/files/rs-8203278/v1/781f456f5dd57e1c56c9e460.jpg"},{"id":97557614,"identity":"5f6710ad-d200-4373-a918-b27e29319a73","added_by":"auto","created_at":"2025-12-05 19:12:32","extension":"jpg","order_by":10,"title":"Figure 10","display":"","copyAsset":false,"role":"figure","size":71632,"visible":true,"origin":"","legend":"\u003cp\u003eDisplacement-force curve.(a)compact arrangement (b)loose arragement (c)soft and hard staggered layered arrangements (d)layered arrangement with soft bottom and hard top\u003c/p\u003e","description":"","filename":"10.jpg","url":"https://assets-eu.researchsquare.com/files/rs-8203278/v1/d2ce73d6af4e5d2ee6dcf5d2.jpg"},{"id":97557619,"identity":"dc3dc26a-9b4e-4678-a7a7-46074988bb43","added_by":"auto","created_at":"2025-12-05 19:12:32","extension":"jpg","order_by":11,"title":"Figure 11","display":"","copyAsset":false,"role":"figure","size":223200,"visible":true,"origin":"","legend":"\u003cp\u003eAnchor maximum stress diagram\u003c/p\u003e","description":"","filename":"11.jpg","url":"https://assets-eu.researchsquare.com/files/rs-8203278/v1/7cf0383b5b469fb363ce7a7f.jpg"},{"id":97673004,"identity":"28e9256e-1278-4279-8a7b-e07c3051c2e0","added_by":"auto","created_at":"2025-12-08 09:39:16","extension":"jpg","order_by":12,"title":"Figure 12","display":"","copyAsset":false,"role":"figure","size":57798,"visible":true,"origin":"","legend":"\u003cp\u003eTime-Stress profile of Anchor\u003c/p\u003e","description":"","filename":"12.jpg","url":"https://assets-eu.researchsquare.com/files/rs-8203278/v1/aad65d676659e8a4996e1fc3.jpg"},{"id":97672291,"identity":"c25e9844-f02c-41c0-b122-9e64b4740252","added_by":"auto","created_at":"2025-12-08 09:35:03","extension":"jpg","order_by":13,"title":"Figure 13","display":"","copyAsset":false,"role":"figure","size":144844,"visible":true,"origin":"","legend":"\u003cp\u003eMaximum Stress Diagram for Rock Bolts Under Different Material Modulus Parameters\u003c/p\u003e","description":"","filename":"13.jpg","url":"https://assets-eu.researchsquare.com/files/rs-8203278/v1/cbd16d772dca052736c16724.jpg"},{"id":100413283,"identity":"0d3be6a6-a91a-404d-b7b6-0cc995479c54","added_by":"auto","created_at":"2026-01-16 13:17:04","extension":"pdf","order_by":0,"title":"","display":"","copyAsset":false,"role":"manuscript-pdf","size":2281860,"visible":true,"origin":"","legend":"","description":"","filename":"manuscript.pdf","url":"https://assets-eu.researchsquare.com/files/rs-8203278/v1/c3d3446f-9631-4d74-9131-b57d545598ed.pdf"}],"financialInterests":"No competing interests reported.","formattedTitle":"Simulation and Experiment of Self-adaptive Device for Hydraulic Support with Roadway Anchor Bolt","fulltext":[{"header":"Introduction","content":"\u003cp\u003eCoal mine impact ground pressure\u003csup\u003e\u003cspan additionalcitationids=\"CR2\" citationid=\"CR1\" class=\"CitationRef\"\u003e1\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR3\" class=\"CitationRef\"\u003e3\u003c/span\u003e\u003c/sup\u003e refers to the violent dynamic disaster phenomenon triggered by the sudden release of elastic deformation energy accumulated in the coal and rock bodies around the underground mining space\u003csup\u003e\u003cspan citationid=\"CR4\" class=\"CitationRef\"\u003e4\u003c/span\u003e\u003c/sup\u003e. This process is usually accompanied by explosive destruction of coal and rock bodies, material ejection, shock wave effect, abnormal gas outpouring, and other characteristics, and has become a very destructive type of geological disaster in deep coal mining. At the same time ofhigh technology and equipment to promote production capacity, as coal mines continue to mine to the depth, the complexity of geological conditions and the superpositioneffect of the mining stress field\u003csup\u003e\u003cspan citationid=\"CR5\" class=\"CitationRef\"\u003e5\u003c/span\u003e\u003c/sup\u003e, resulting in the frequency of this type of disaster trend and the intensity of destruction showed a significant increase in the situation.As the core equipment of a modernized mine tunnel support system, hydraulic support plays an irreplaceable role in guaranteeing the safety of mining operations and improving production efficiency. The traditional rigid support structure is difficult to adapt to the complex working conditions such as large deformation of the surrounding rock in the deep tunnel and high geostress, while the hydraulic support\u003csup\u003e\u003cspan citationid=\"CR6\" class=\"CitationRef\"\u003e6\u003c/span\u003e\u003c/sup\u003e, under its adaptive support characteristics, dynamically adjusts the support force through the hydraulic system, effectively controlling the deformation of the surrounding rock, and significantly improves the stability of the tunnel.\u003c/p\u003e\u003cp\u003eAs the core technology of active reinforcement of surrounding rock, anchor support\u003csup\u003e\u003cspan citationid=\"CR7\" class=\"CitationRef\"\u003e7\u003c/span\u003e, \u003cspan citationid=\"CR8\" class=\"CitationRef\"\u003e8\u003c/span\u003e\u003c/sup\u003e has become an important part of the modern mine tunnel support system by its unique advantage of \u0026ldquo;timely support and strengthening bearing\u0026rdquo;. Different from the traditional passive support method, the anchor rod is closely combined with the surrounding rock to form a \u0026ldquo;surrounding rock-anchor structure\u0026rdquo; synergistic bearing system, which significantly improves the self-supporting capacity of the rock body and effectively suppresses the deformation of the roadway. The introduction of innovative technologies such as prestressing anchor cable group and grouting modified cooperative support has promoted the development of anchor support from single reinforcement to the multi-dimensional prevention and control mode of \u0026ldquo;active pre-tensioning - dynamic reinforcement - peripheral rock modification\u0026rdquo;\u003csup\u003e9\u003c/sup\u003e.As shown in Fig.\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003e.Two kinds of coal mine roadway support methods are very mature.It plays an important role in roadway surrounding rock support.\u003c/p\u003e\u003cp\u003eIt is difficult for a single support technology to meet the dynamic control demand of the \u0026ldquo;high intensity deformation and non-uniform load\u0026rdquo; of the surrounding rock in the roadway. Pan Yishan et al. \u003csup\u003e10\u003c/sup\u003e put forward the theory and technology of three-level support, and the synergistic mechanism of hydraulic support and anchor support has become a key technology path to realize the stability of the whole life cycle of the tunnel. Hydraulic bracing actively exerts a strong support force, rapidly suppresses the initial deformation of the surrounding rock, and balances the mining stress; anchor support is deep inside the rock, through the anchoring structure to mobilize the surrounding rock's self-supporting capacity, forming a \u0026ldquo;surface-deep\u0026rdquo; linkage of the composite load-bearing system. From preventing impact initiation to weakening impact damage, a systematic prevention and control chain is formed, significantly reducing the hazards of impact ground pressure on the roadway and personnel\u003csup\u003e\u003cspan citationid=\"CR11\" class=\"CitationRef\"\u003e11\u003c/span\u003e\u003c/sup\u003e.\u003c/p\u003e\u003cp\u003eIn roadway perimeter rock support projects, stress concentration from the protruding end of the anchor support system is a key hazard limiting support effectiveness. As shown in Fig.\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003e, the anchor and hydraulic bracket support system under impact pressure causes uneven compression between the hydraulic bracket top plate and protruding anchor ends, distorting stress distribution. This effect intensifies when the exposed anchor length is excessive or pallet size mismatches, as collisions between anchor ends and the hydraulic bracket top plate exacerbate end stress concentration. The resulting high-stress zones induce micro-fractures in surrounding rock, accelerating fragmentation and weakening the anchoring system's overall bearing capacity. Stress concentration may also cause fatigue fracture of anchor thread sections or pallet deformation, reducing support reliability.\u003c/p\u003e\u003cp\u003e\u003c/p\u003e\u003cp\u003e\u003c/p\u003e\u003cp\u003eAnchor damage caused by brackets is a frequent problem that seriously affects the reliability and engineering efficiency of the support system. After in-depth analysis, the cause of the problem covers both explicit and implicit dimensions: the explicit dimension is manifested in the direct contact between the bracket and the anchor, while the implicit dimension originates from the mismatch between the two stiffnesses, resulting in an imbalance in the force transfer mechanism. The solution strategies of \u0026ldquo;Dodging anchor\u0026rdquo; and \u0026ldquo;protecting anchor\u0026rdquo; are proposed. \u0026ldquo;Dodging anchor\u0026rdquo; reduces the physical contact conflict through spatial layout optimization or structural design avoidance; \u0026ldquo;protecting anchor\u0026rdquo; adjusts the bracket force pattern from the perspective of mechanical optimization, avoiding local stress concentration in the anchor and strengthening the protection mechanism. Its core adaptive goals focus on: adapting to the diversity of irregular anchor patterns,matching the complex conditions of uneven roof slabs, guaranteeing the uniform force on the roof beams to optimize the mechanical balance, and matching the geological characteristics of the rigidity of the roof slabs of the coal seams, so as to improve the overall adaptability and stability of the support system.The design idea of the device is shown in Fig.\u0026nbsp;\u003cspan refid=\"Fig3\" class=\"InternalRef\"\u003e3\u003c/span\u003e.\u003c/p\u003e\u003cp\u003e\u003c/p\u003e\u003cp\u003eAt present, there are three main types of bolt protection devices installed on the top beam of the hydraulic support, as shown in Fig.\u0026nbsp;\u003cspan refid=\"Fig4\" class=\"InternalRef\"\u003e4\u003c/span\u003e. The first type is a sliding beam that slides by a guide rail, and an avoidance that matches the anchor rod or anchor cable is formed between adjacent raised structures. The advantage is that the structure is simple, and the adaptability to the regular row spacing anchors is good, but the disadvantage is that the top beam is under concentrated force; the second type is that the top beam is discretely arranged with single or multiple rows of top-connected hydraulic supports to form a flexible top-connected unit to achieve the function of avoiding the anchor.\u003c/p\u003e\u003cp\u003eThe advantage is that it has good adaptability to the irregular row spacing anchors and uneven roof plates. The disadvantage is that hydraulic control is required, the operation program is too complicated, the stability of the support is poor, and the top beam is under concentrated force. The third type is that the wire rope controls the support beam on the top beam of the hydraulic support, which has the advantage that Interrow spacing anchors have good adaptability and uniform stress distribution on top beams, but they are not suitable for high working resistance requirements.\u003c/p\u003e\u003cp\u003e\u003c/p\u003e\u003cp\u003eThis paper designs a buffer ball device, which is installed inside the roof of the hydraulic support through a multi-stage buffer mechanism of nylon and rubber balls to prevent the end of the anchor rod from directly contacting the roof of the hydraulic support. The simulation software is used to analyze the 2D planar state of the device, observe the stress nephogram of the entire model movement under impact load, verify the theoretical feasibility of the device, and further verify the practical feasibility of the buffer ball device through hydraulic press experiments, providing a new idea for mine roadway support\u003c/p\u003e"},{"header":"Design of the Roof Buffer Ball Device for Hydraulic Support","content":"\u003cp\u003eThe device is jacked vertically upward to simulate the contact between the hydraulic support and the rock stratum roof. By utilizing the mechanism of the buffer ball for adaptive position adjustment, the purpose of protecting the anchor bolt is achieved through adjusting the space and bearing part of the impact pressure. Energy transfer path: external load\u0026rarr;nylon ball plastic deformation (energy consumption 30%) residual energy released through the stent hydraulic system, forming a \u0026ldquo;graded energy consumption - energy storage - energy drainage\u0026rdquo; chain\u003csup\u003e\u003cspan citationid=\"CR12\" class=\"CitationRef\"\u003e12\u003c/span\u003e\u003c/sup\u003e.\u003c/p\u003e\u003cdiv id=\"Sec3\" class=\"Section2\"\u003e\u003ch2\u003eStructural design of the buffer ball device\u003c/h2\u003e\u003cp\u003e\u003c/p\u003e\u003cp\u003eThe buffer ball device is arranged in the hydraulic bracket support top plate, the top plate is welded around by steel plate to form an uncovered groove, the internal uniform arrangement of three layers of buffer balls with a diameter of 50mm, the bottom of the 50mm rubber ball padding, the rubber ball on the uniform arrangement of the two layers of 50mm nylon ball, as shown in Fig.\u0026nbsp;5.\u003c/p\u003e\u003cp\u003e\u003cb\u003eFigure\u0026nbsp;5\u003c/b\u003e Working principle of adaptive device\u003c/p\u003e\u003c/div\u003e\n\u003ch3\u003eThe experiment of the Buffer ball device\u003c/h3\u003e\n\u003cdiv id=\"Sec5\" class=\"Section2\"\u003e\u003ch2\u003eExperimental preparation of the buffer ball device\u003c/h2\u003e\u003cp\u003eAccording to the research purpose and research program of the buffer ball device, the laboratory tensile press was used to conduct experiments, and the tensile testing machine loaded the buffer ball at the elevating base plate, and after the load calculation, the 60t tensile testing machine was used to ensure the stability of the test loading.\u003c/p\u003e\u003cp\u003e(1) Buffer ball device. The device is formed by welding a steel plate into an iron box, with an internal placement of white nylon balls and numbered for each ball, nylon ball diameter of 50mm. the test selected HRB500 left-hand threaded steel anchor, nominal diameter of 22mm, with the nut welded to an anchor disk used to prevent the anchor inserted into the device when the nylon ball was extruded out of the iron box.\u003c/p\u003e\u003cp\u003e(2) 60 tons tensile testing machine. Its wide range of uses can be metal, non-metallic composite materials, tensile, compression, bending, shear, and other experiments. The use of a high-precision pressure transducer for force measurement the data collected more accurate, testing machine in Fig.\u0026nbsp;\u003cspan refid=\"Fig5\" class=\"InternalRef\"\u003e6\u003c/span\u003e.\u003c/p\u003e\u003cp\u003e\u003c/p\u003e\u003cp\u003e(3) Overall assembly: Fix the anchor rod on the crossbeam of the tension-compression testing machine, and place the buffer ball device under the anchor rod to ensure that the anchor rod can be fully inserted into the buffer ball device when the testing machine controls the lift table to rise. The experimental setup is arranged as shown in Fig.\u0026nbsp;\u003cspan refid=\"Fig6\" class=\"InternalRef\"\u003e7\u003c/span\u003e.\u003c/p\u003e\u003cp\u003e\u003c/p\u003e\u003c/div\u003e\n\u003ch3\u003eStudy of buffer ball arrangement programs\u003c/h3\u003e\n\u003cp\u003e(1) The buffer ball device is fully loaded with nylon balls: tight and loose arrangements are set up separately. The characteristics of the nylon balls in different arrangement modes are explored in depth. In the tight arrangement, the gap between the nylon balls is negligible, focusing on analyzing the uniqueness of the energy transfer path and cushioning mechanism in this state; in the loose arrangement, focusing on the influence of the relative motion space between the balls on the overall stability and cushioning efficiency of the bulk, analyzing in detail how the different arrangement\u003csup\u003e\u003cspan citationid=\"CR13\" class=\"CitationRef\"\u003e13\u003c/span\u003e\u003c/sup\u003e modes shape the spatial structure of the bulk and the characteristics of mechanical response, and accurately revealing the potential influence of the spatial distribution characteristics of the bulk on the cushioning performance.\u003c/p\u003e\u003cp\u003e(2) Adding soft rubber balls to the buffer ball device: The arrangement of soft and hard staggered layers and the lower soft and upper hard layers is set up, respectively.the lower soft and upper hard layers is set up, respectively. Adding rubber balls can improve the performance of the adaptive adjustment of the buffe ball device as shown in Fig.\u0026nbsp;\u003cspan refid=\"Fig7\" class=\"InternalRef\"\u003e8\u003c/span\u003e. For the soft-hard staggered layered arrangement, investigate the process of soft-hard ball synergy to achieve efficient cushioning when the force is applied in multiple directions, and analyze the energy distribution mechanism between the soft-hard balls in the force transfer path; for the lower soft-hard layered arrangement, focus on researching the initial resistance of the upper hard ball to the impact force and the subsequent energy absorption characteristics of the lower soft ball, and analyze the arrangement. In response to the different strengths and directions of the impact of the adaptive adjustment process, revealing its optimization of the buffer performance of the intrinsic mechanical principles, for the practical application of the buffer ball device to provide more targeted theoretical support.\u003c/p\u003e\u003cp\u003e\u003c/p\u003e"},{"header":"Analysis of experimental results","content":"\u003cdiv id=\"Sec8\" class=\"Section2\"\u003e\u003ch2\u003eIndicators for research and analysis\u003c/h2\u003e\u003cp\u003e\u003cdiv id=\"Equa\" class=\"Equation\"\u003e\u003cdiv format=\"TEX\" class=\"mathdisplay\" id=\"FileID_Equa\" name=\"EquationSource\"\u003e\n$$\\:E={\\int\\:}_{0}^{\\delta\\:-{\\delta\\:}_{0}}F\\left(S\\right)ds$$\u003c/div\u003e\u003c/div\u003e\u003c/p\u003e\u003cp\u003e\u003cdiv id=\"Equb\" class=\"Equation\"\u003e\u003cdiv format=\"TEX\" class=\"mathdisplay\" id=\"FileID_Equb\" name=\"EquationSource\"\u003e\n$$\\:{F}_{mean}=\\frac{1}{\\delta\\:-{\\delta\\:}_{0}}{\\int\\:}_{0}^{\\delta\\:-{\\delta\\:}_{0}}F\\left(S\\right)ds$$\u003c/div\u003e\u003c/div\u003e\u003c/p\u003e\u003cp\u003e\u003cem\u003eFull placement of hard nylon balls\u003c/em\u003e\u003c/p\u003e\u003cp\u003ei) compact arrangement\u003c/p\u003e\u003cp\u003eThe test begins. The anchor rod is inserted into the buffer ball and comes into contact with the ball, the force on the anchor rod remains unchanged during the jacking of the loading bottom plate. After the anchor rod penetrates 46 mm into the box, the load suddenly increases, and a relatively loud noise occurs. It is speculated that the anchor rod directly hits the sphere.The spheres inside the box are relatively dense, and there is no room for adjustment. The load continues to increase without dropping back. When the load rises to 25 kN, the test is stopped.The anchor rod cannot be fully immersed in the box.\u003c/p\u003e\u003cp\u003eii)loose arrangement\u003c/p\u003e\u003cp\u003eThe test begins. The anchor rod is inserted into the loose sphere and makes contact with the sphere. the force on the anchor rod remains basically unchanged during the jacking of the bottom plate. After the anchor rod penetrates 80 mm into the box, the fluctuation of the load indicates the frictional contact between the anchor rod and the sphere. When the displacement of the bottom plate rises to 93 mm, the load rises slightly and then drops, and the sphere adjusts automatically under the extrusion of the anchor rod. When the displacement reaches 106 mm and 113 mm, the load experiences two rises and falls, and the extrusion contact of the anchor rod makes the arrangement of the spheres redistribute. It can be seen from the jacking displacement of the bottom plate and the photos that the anchor rod has fully penetrated into the box.As shown in Fig.\u0026nbsp;\u003cspan refid=\"Fig8\" class=\"InternalRef\"\u003e9\u003c/span\u003e, the test of the anchor rod kept going deeper and deeper into the buffer ball, contacting the ball with friction and squeezing, and the ball automatically made adjustments to fit into the anchor space. As can be seen in the photos before and after the test, the 18th ball fell from the middle layer into the lower layer, the 20th ball squeezed the 23rd ball into the upper layer, the 34th ball fell from the upper layer into the lower layer, the 25th ball went from the outer ring to the inside, and the 29th ball position also changed.\u003c/p\u003e\u003cp\u003e\u003c/p\u003e\u003cp\u003e\u003cem\u003eAdding rubber soft balls\u003c/em\u003e\u003c/p\u003e\u003cp\u003ei) Hard and soft layering\u003c/p\u003e\u003cp\u003eTo investigate the adaptability of spherical structures under extreme conditions, a scenario is set where soft spheres and hard spheres are distributed completely randomly, with approximate considerations given to the packing of spheres at engineering sites. An empty box is taken, and two authors randomly place hard spheres and soft spheres into it without any restrictions on quantity, position, layer, or density until the box is full. When the loading base plate is jacked up, the force on the anchor rod remains constant; the load suddenly increases to a depth of approximately 80 mm to 100 mm in the box, after which the load continues to grow.\u003c/p\u003e\u003cp\u003eii) Layered arrangement with soft bottom and hard top\u003c/p\u003e\u003cp\u003eThe bottom of the box is all filled with rubber soft balls, and the upper part is filled with nylon balls to test the stratifiedarrangement situation with soft at the bottom and hard at the top.The anchor rod inserts into and contacts with the ball. When the loading floor is jacked up, the force on the anchor rod remains unchanged.After the anchor rod penetrates 100mm into the box, the load begins to suddenly increase, and continuously grows without falling back. When the load rises to 25kN, the test is stopped.All data is shown in Fig.\u0026nbsp;\u003cspan refid=\"Fig9\" class=\"InternalRef\"\u003e10\u003c/span\u003e.\u003c/p\u003e\u003cp\u003eAs evidenced by the data presented in Table\u0026nbsp;\u003cspan refid=\"Tab1\" class=\"InternalRef\"\u003e1\u003c/span\u003e, the loose arrangement demonstrates a 1.6% increase in the average bearing capacity (F\u003csub\u003emean\u003c/sub\u003e) and a 77.8% rise in total energy absorption (E) compared to the compact configuration, indicating a notable improvement in energy dissipation efficiency. The incorporation of rubber spheres leads to a marginal enhancement in the energy absorption performance of the device, which may be attributed to their viscoelastic characteristics. In the case of the randomized configuration comprising both hard and soft spheres, a 1.5% increase in F\u003csub\u003emean\u003c/sub\u003e and a 13% rise in E are observed relative to the loose arrangement. For the layered configuration with hard spheres positioned above soft spheres, F\u003csub\u003emean\u003c/sub\u003e is enhanced by 8.6% and E by 3.5% compared to the loose arrangement.\u003c/p\u003e\u003cp\u003e\u003c/p\u003e\u003cp\u003e\u003cdiv class=\"gridtable\"\u003e\u003ctable float=\"Yes\" id=\"Tab1\" border=\"1\"\u003e\u003ccaption language=\"En\"\u003e\u003cdiv class=\"CaptionNumber\"\u003eTable 1\u003c/div\u003e\u003cdiv class=\"CaptionContent\"\u003e\u003cp\u003ePerformance indicators for different arrangements\u003c/p\u003e\u003c/div\u003e\u003c/caption\u003e\u003ccolgroup cols=\"5\"\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c1\" colnum=\"1\"\u003e\u003c/div\u003e\u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c2\" colnum=\"2\"\u003e\u003c/div\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c3\" colnum=\"3\"\u003e\u003c/div\u003e\u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c4\" colnum=\"4\"\u003e\u003c/div\u003e\u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c5\" colnum=\"5\"\u003e\u003c/div\u003e\u003cthead\u003e\u003ctr\u003e\u003cth align=\"left\" colname=\"c1\"\u003e\u003cp\u003eproject\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c2\"\u003e\u003cp\u003e\u003cspan class=\"InlineEquation\"\u003e\u003cspan class=\"mathinline\"\u003e\\(\\:\\varvec{\\delta\\:}\\)\u003c/span\u003e\u003c/span\u003e/mm\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c3\"\u003e\u003cp\u003e\u003cspan class=\"InlineEquation\"\u003e\u003cspan class=\"mathinline\"\u003e\\(\\:{\\varvec{\\delta\\:}}_{0}/\\)\u003c/span\u003e\u003c/span\u003emm\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c4\"\u003e\u003cp\u003eE/J\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c5\"\u003e\u003cp\u003eF\u003csub\u003emean/\u003c/sub\u003eKN\u003c/p\u003e\u003c/th\u003e\u003c/tr\u003e\u003c/thead\u003e\u003ctbody\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003ecompact\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e\u003cp\u003e50.79\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e44\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e\u003cp\u003e12.79\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e\u003cp\u003e9.47\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eloose\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e\u003cp\u003e131.3\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e106.3\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e\u003cp\u003e57.6\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e\u003cp\u003e9.63\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003ehard and soft layering\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e\u003cp\u003e127.6\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e91\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e\u003cp\u003e66.23\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e\u003cp\u003e9.78\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003esoft bottom and hard top\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e\u003cp\u003e115.3\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e91.8\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e\u003cp\u003e59.7\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e\u003cp\u003e10.54\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003c/tbody\u003e\u003c/colgroup\u003e\u003c/table\u003e\u003c/div\u003e\u003c/p\u003e\u003c/div\u003e\n\u003ch3\u003eBuffer ball device finite element simulation\u003c/h3\u003e\n\u003cp\u003eThe finite element software ABAQUS\u003csup\u003e\u003cspan citationid=\"CR14\" class=\"CitationRef\"\u003e14\u003c/span\u003e\u003c/sup\u003e is used to establish a 2D planar finite element model for the buffer ball device, and the buffer ball device model is divided into four parts: rock layer, anchor rod, buffer ball, and top plate of the hydraulic support. The material parameters for the rock formation model are set as Table\u0026nbsp;\u003cspan refid=\"Tab2\" class=\"InternalRef\"\u003e2\u003c/span\u003e: density of 2.46\u0026times;10\u003csup\u003e3\u003c/sup\u003ekg/m\u003csup\u003e3\u003c/sup\u003e, elastic modulus of 19.5GPa, and Poisson\u0026rsquo;s ratio of 0.2. For the anchor rod material, the parameters are: density of 7.85\u0026times;10\u003csup\u003e3\u003c/sup\u003ekg/m, modulus of elasticity is 210GPa, Poisson's ratio is 0.26, yield stress is 235Mpa; rubber ball material parameter setting density is 2.1\u0026times;10\u003csup\u003e3\u003c/sup\u003ekg/m\u003csup\u003e3\u003c/sup\u003e, modulus of elasticity is 0.5GPa, Poisson's ratio is 0.4; nylon ball material parameter setting density is 1.15\u0026times;10\u003csup\u003e3\u003c/sup\u003ekg/m\u003csup\u003e3\u003c/sup\u003e, modulus of elasticity is 3.5GPa, Poisson's ratio is 0.3, yield stress is 70Mpa; hydraulic bracket top plate material parameters are set to 7.85\u0026times;10\u003csup\u003e3\u003c/sup\u003ekg/m\u003csup\u003e3\u003c/sup\u003e, elastic modulus is 210GPa, Poisson's ratio is 0.26, yield stress is 890Mpa. The length of both the rock layer and the top plate of the hydraulic support is 4000mm, and an anchor is arranged at an interval of 1000mm, and the Dynamic-Explicit algorithm is used to set the two analysis steps of movement and compression,with the movement step set at 0.2s, the compression step set at 0.1s, and the friction factor at 0.2. The rock layer is kept completely fixed, and the top plate of the hydraulic support underneath is constrained to move and rotate in the direction of x-axis and kept the top plate moving in y-axis direction, and set upward 24Mpa instantaneous pressure at the bottom of the hydraulic bracket top plate.\u003c/p\u003e\u003cp\u003e\u003cdiv class=\"gridtable\"\u003e\u003ctable float=\"Yes\" id=\"Tab2\" border=\"1\"\u003e\u003ccaption language=\"En\"\u003e\u003cdiv class=\"CaptionNumber\"\u003eTable 2\u003c/div\u003e\u003cdiv class=\"CaptionContent\"\u003e\u003cp\u003eMaterial Properties\u003c/p\u003e\u003c/div\u003e\u003c/caption\u003e\u003ccolgroup cols=\"5\"\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c1\" colnum=\"1\"\u003e\u003c/div\u003e\u003cdiv align=\"char\" char=\"\u0026times;\" class=\"colspec\" colname=\"c2\" colnum=\"2\"\u003e\u003c/div\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c3\" colnum=\"3\"\u003e\u003c/div\u003e\u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c4\" colnum=\"4\"\u003e\u003c/div\u003e\u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c5\" colnum=\"5\"\u003e\u003c/div\u003e\u003cthead\u003e\u003ctr\u003e\u003cth align=\"left\" colname=\"c1\"\u003e\u003cp\u003epart\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c2\"\u003e\u003cp\u003eDensity(kg/m\u003csup\u003e3)\u003c/sup\u003e\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c3\"\u003e\u003cp\u003emodulus of elasticity(Gpa)\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c4\"\u003e\u003cp\u003ePoisson's ratio\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c5\"\u003e\u003cp\u003eyield stres(Mpa)\u003c/p\u003e\u003c/th\u003e\u003c/tr\u003e\u003c/thead\u003e\u003ctbody\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003erock\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\"\u0026times;\" colname=\"c2\"\u003e\u003cp\u003e2.46\u0026times;10\u003csup\u003e3\u003c/sup\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e19.5\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e\u003cp\u003e0.2\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u0026nbsp;\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eanchor rod\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\"\u0026times;\" colname=\"c2\"\u003e\u003cp\u003e7.85\u0026times;10\u003csup\u003e3\u003c/sup\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e210\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e\u003cp\u003e0.26\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e\u003cp\u003e235\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003erubber ball\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\"\u0026times;\" colname=\"c2\"\u003e\u003cp\u003e2.1\u0026times;10\u003csup\u003e3\u003c/sup\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e0.5\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e\u003cp\u003e0.4\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u0026nbsp;\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003enylon ball\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\"\u0026times;\" colname=\"c2\"\u003e\u003cp\u003e1.15\u0026times;10\u003csup\u003e3\u003c/sup\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e3.5\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e\u003cp\u003e0.3\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e\u003cp\u003e70\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003ehydraulic bracket top plate\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\"\u0026times;\" colname=\"c2\"\u003e\u003cp\u003e7.85\u0026times;10\u003csup\u003e3\u003c/sup\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e210\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e\u003cp\u003e0.26\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e\u003cp\u003e890\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003c/tbody\u003e\u003c/colgroup\u003e\u003c/table\u003e\u003c/div\u003e\u003c/p\u003e\n\u003ch3\u003eAnchor force Analysis\u003c/h3\u003e\n\u003cp\u003eAfter completing the full-model simulation, the entire insertion process of the anchor rods into the buffer ball device was monitored. During insertion, the buffer ball continuously adjusts its spatial position through compressive deformation (compressive deformation). Relevant experimental data were collected, and the effectiveness of the device in preventing direct contact between the anchor rods and the hydraulic support top plate after the completion of pressure loading was verified\u003csup\u003e\u003cspan citationid=\"CR15\" class=\"CitationRef\"\u003e15\u003c/span\u003e\u003c/sup\u003e. In the simulation model, the three anchor rods were labeled as A-anchor, B-anchor, and C-anchor from left to right, respectively. The stress distribution nephograms of the three anchors at their respective maximum stress states were analyzed (Fig.\u0026nbsp;\u003cspan refid=\"Fig10\" class=\"InternalRef\"\u003e11\u003c/span\u003e). It is observed that the maximum stress of all three anchors is concentrated at the anchor-anchor rod connection interface, which is consistent with the mechanical characteristics of the assembled structure under impact loading.\u003c/p\u003e\u003cp\u003e\u003c/p\u003e\u003cp\u003eTime-stress curves of the three anchors were plotted based on the temporal evolution of stress during the simulation (Fig.\u0026nbsp;\u003cspan refid=\"Fig11\" class=\"InternalRef\"\u003e12\u003c/span\u003e). It is found that after 0.1 s, slight stress fluctuations occur in the anchors immediately after contact with the buffer ball, which is attributed to the initial contact interaction and elastic energy exchange between the anchor and the buffer ball. For the A-anchor, the stress begins to increase linearly at approximately 0.19 s. Further analysis of the time-stress curve of the A-anchor reveals that after 0.19 s, the stress exhibits a nonlinear steep rise, accompanied by multiple peaks and valleys within the time interval of 0.19\u0026ndash;0.2 s. This phenomenon indicates that the initial spatial position of the buffer ball is not optimal; thus, after contact with the A-anchor, the buffer ball undergoes several rounds of fine adjustments (e.g., elastic deformation and displacement compensation) to redistribute the local stress concentration. During this process, the buffer ball absorbs impact energy through periodic elastic deformation, leading to an oscillatory decay trend of the anchor stress, which is a typical dynamic response of elastic buffer components under transient loading.\u003c/p\u003e\u003cp\u003eFor the B-anchor, the time-stress curve shows no significant peaks or valleys during the instantaneous compression stage. This is because the B-anchor achieves an optimal contact position with the buffer ball after the first compressive adjustment. When the overall structure stabilizes under impact loading, the stress on the B-anchor tends to flatten, indicating that the buffer ball can effectively dissipate impact energy and balance the stress distribution for anchors at the optimal contact position.\u003c/p\u003e\u003cp\u003eThe C-anchor exhibits 1\u0026ndash;2 minor stress fluctuations within the 0.19\u0026ndash;0.2 s interval, with an amplitude lower than that of the A-anchor. Subsequently, the maximum stress of the C-anchor undergoes a sudden sharp decrease followed by a continuous rise. A unique mechanism is proposed for this phenomenon: due to the large length span of the entire simulation model, the center of gravity of the system may shift slightly when the hydraulic support top plate moves upward again. After being subjected to instantaneous compression, the left A-anchor and the middle B-anchor bear most of the impact load, resulting in a stress decrease in the C-anchor after reaching its maximum stress value.\u003c/p\u003e\u003cp\u003e\u003c/p\u003e\u003cp\u003eExperimental verification shows that all three anchors avoid direct collision with the hydraulic support top plate under impact loading, which fully meets the core design requirement of the device. During the insertion of the anchors into the buffer ball device, the maximum stress of each anchor does not exceed the yield strength of the anchor material, ensuring the structural integrity and service safety of the anchors. In conclusion, the simulation results of the buffer ball device are consistent with the expected experimental theory and meet the structural design intent of the device. This study provides reliable theoretical support and experimental basis for the engineering application of the buffer ball device in hydraulic support systems.\u003csup\u003e\u003cspan citationid=\"CR16\" class=\"CitationRef\"\u003e16\u003c/span\u003e\u003c/sup\u003e\u003c/p\u003e\u003cdiv id=\"Sec11\" class=\"Section2\"\u003e\u003ch2\u003eParameter Optimisations\u003c/h2\u003e\u003cp\u003eTo investigate and optimize the parameters of the device for better buffering performance, several sets of buffer balls with different parameters were subjected to numerical simulations. The aim was to observe and analyze the effects of different parameters on the buffer ball device and identify a superior solution. First, balls with different elastic moduli were selected as experimental subjects. To ensure data uniformity, the simulation was set up for a single anchor rod, with balls having elastic moduli of 190 GPa, 200 GPa, 210 GPa, and 220 GPa, while other parameters remained unchanged. The maximum stress of the anchor rod was then observed. For data accuracy, each set of simulation experiments was repeated five times, and the average values were calculated, as presented in Table\u0026nbsp;\u003cspan refid=\"Tab3\" class=\"InternalRef\"\u003e3\u003c/span\u003e.\u003c/p\u003e\u003cp\u003e\u003cdiv class=\"gridtable\"\u003e\u003ctable float=\"Yes\" id=\"Tab3\" border=\"1\"\u003e\u003ccaption language=\"En\"\u003e\u003cdiv class=\"CaptionNumber\"\u003eTable 3\u003c/div\u003e\u003cdiv class=\"CaptionContent\"\u003e\u003cp\u003eMaterial Properties\u003c/p\u003e\u003c/div\u003e\u003c/caption\u003e\u003ccolgroup cols=\"7\"\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c1\" colnum=\"1\"\u003e\u003c/div\u003e\u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c2\" colnum=\"2\"\u003e\u003c/div\u003e\u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c3\" colnum=\"3\"\u003e\u003c/div\u003e\u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c4\" colnum=\"4\"\u003e\u003c/div\u003e\u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c5\" colnum=\"5\"\u003e\u003c/div\u003e\u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c6\" colnum=\"6\"\u003e\u003c/div\u003e\u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c7\" colnum=\"7\"\u003e\u003c/div\u003e\u003cthead\u003e\u003ctr\u003e\u003cth align=\"left\" colname=\"c1\"\u003e\u003cp\u003eModulus of elasticity(GPa)\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c2\"\u003e\u003cp\u003eGroup One(Mpa)\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c3\"\u003e\u003cp\u003eGroup Two(Mpa)\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c4\"\u003e\u003cp\u003eGroup Three(Mpa)\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c5\"\u003e\u003cp\u003eGroup Four(Mpa)\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c6\"\u003e\u003cp\u003eGroup Five(Mpa)\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c7\"\u003e\u003cp\u003eMean(Mpa)\u003c/p\u003e\u003c/th\u003e\u003c/tr\u003e\u003c/thead\u003e\u003ctbody\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003e190\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e\u003cp\u003e208.9\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e\u003cp\u003e204.3\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e\u003cp\u003e207.1\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e\u003cp\u003e203.3\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c6\"\u003e\u003cp\u003e212.8\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c7\"\u003e\u003cp\u003e207.3\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003e200\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e\u003cp\u003e203.4\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e\u003cp\u003e205.9\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e\u003cp\u003e203.2\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e\u003cp\u003e204.1\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c6\"\u003e\u003cp\u003e203.6\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c7\"\u003e\u003cp\u003e204.0\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003e210\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e\u003cp\u003e195.5\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e\u003cp\u003e198.7\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e\u003cp\u003e195.3\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e\u003cp\u003e197.1\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c6\"\u003e\u003cp\u003e196.2\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c7\"\u003e\u003cp\u003e196.6\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003e220\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e\u003cp\u003e232.9\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e\u003cp\u003e234.7\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e\u003cp\u003e232.2\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e\u003cp\u003e232.9\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c6\"\u003e\u003cp\u003e231.0\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c7\"\u003e\u003cp\u003e232.7\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003c/tbody\u003e\u003c/colgroup\u003e\u003c/table\u003e\u003c/div\u003e\u003c/p\u003e\u003cp\u003eIt is worth noting that the elastic modulus does not present a monotonically linear relationship with the maximum stress. The material with an elastic modulus of 210 GPa may exhibit superior low-stress performance, which can be ascribed to its intrinsic mechanical propertie. These properties facilitate a more homogeneous stress distribution during finite element simulations, in accordance with the mechanics principle of stress propagation and equilibrium in composite systems.\u003c/p\u003e\u003cp\u003eIn contrast, the material with an elastic modulus of 220 GPa, due to its excessively high stiffness, is prone to stress concentration under loading conditions. This phenomenon violates the stress compatibility condition at the structural interfaces, thereby inducing a drastic escalation in the maximum stress, which is consistent with the theoretical prediction of stress concentration in high-modulus materials under constrained deformation,as illustrated in Fig.\u0026nbsp;\u003cspan refid=\"Fig12\" class=\"InternalRef\"\u003e13\u003c/span\u003e.\u003c/p\u003e\u003cp\u003e\u003c/p\u003e\u003c/div\u003e\u003cdiv id=\"Sec12\" class=\"Section2\"\u003e\u003ch2\u003eAdvantages of the device\u003c/h2\u003e\u003cp\u003e(1) The buffer ball device is an independent mechanism capable of modular production. It offers greater versatility and ease of installation, allowing for free combination with any equipment having relevant requirements. Moreover, it does not necessitate modifications to the structure of the carrier equipment, ensuring that the structural strength of the carrier equipment remains unaffected.\u003c/p\u003e\u003cp\u003e(2) When the avoidance device is interfaced with the hydraulic support, the connection is achieved through the engagement between the fixing pins welded to the lower surface of the beam and the mounting holes on the roof beam of the hydraulic support. These fixing pins not only serve as a connection mechanism but also directly bear the lateral forces exerted by the roadway roof plate, thereby protecting critical components\u0026ldquo;the hydraulic cylinders\u0026rdquo;from damage.\u003c/p\u003e\u003c/div\u003e"},{"header":"Conclusion","content":"\u003cp\u003eThis study uses experiments and software simulation to verify the applicability and feasibility of the device, and the buffer ball structure of the device can well solve the problem that the collision between the anchor rod and the roof plate of the hydraulic bracket and the anchor support in the mine roadway under the situation of coordinated work of hydraulic bracket support and anchor support leads to the damage of the anchor rod by the force, which makes the anchor perimeter rock support effect ineffective. The main research results are as follows:\u003c/p\u003e\u003cp\u003e(1) By analyzing the experimental data, the energy absorption index E of the loose arrangement of the buffer balls of this device is 77.8% higher than that of the compact arrangement, and the average force Fmean is increased by 1.6%, which should be avoided for the highly tight arrangement.\u003c/p\u003e\u003cp\u003e(2) After the incorporation of rubber soft balls, the energy absorption effect of the device has been slightly improved. Through analysis, it is concluded that the random arrangement of hard and soft balls, which is closer to the on-site layout in construction, represents the optimal solution.\u003c/p\u003e\u003cp\u003e(3) Based on the design principle of this hydraulic support roof device, more and better devices can be developed in the future by modifying the material and size of the spheres inside the device, as well as integrating other forms of support methods.\u003c/p\u003e"},{"header":"Declarations","content":"\u003cp\u003e\u003ch2\u003eAuthor contributions statement\u003c/h2\u003e\u003cp\u003eAD, XHL contributed to the conception of the study. WZY, TJW, TRS performed the experiment. AD, WZY contributed significantly to analysis and manuscript preparation. AD,WZY performed the data analyses and wrote the manuscript. All authors read the manuscript.\u003c/p\u003e\u003c/p\u003e\u003cp\u003e\u003cstrong\u003eCompeting interests\u003c/strong\u003e\u003cp\u003eThe authors declare no competing interests.\u003c/p\u003e\u003c/p\u003e\u003cp\u003e\u003ch2\u003eAdditional information\u003c/h2\u003e\u003cp\u003eCorrespondence and requests for materials should be addressed to H.X.\u003c/p\u003e\u003c/p\u003e\u003ch2\u003eFunding\u003c/h2\u003e\u003cp\u003eDeclaration\u003c/p\u003e\u003cp\u003eThis work was supported by the National Natural Science Foundation of China (No. 52427805).\u003c/p\u003e\u003ch2\u003eAuthor Contribution\u003c/h2\u003e\u003cp\u003eAD, XHL contributed to the conception of the study. WZY, TJW, TRS performed the experiment. AD, WZY contributed significantly to analysis and manuscript preparation. AD,WZY performed the data analyses and wrote the manuscript. All authors read the manuscript.\u003c/p\u003e\u003ch2\u003eAcknowledgement\u003c/h2\u003e\u003cp\u003eThis work was supported by the National Natural Science Foundation of China (No. 52427805).\u003c/p\u003e\u003ch2\u003eData Availability\u003c/h2\u003e\u003cp\u003eAll data, models, or code that support the findings of this study are available from the corresponding author upon reasonable request.\u003c/p\u003e"},{"header":"References","content":"\u003col\u003e\u003cli\u003e\u003cspan\u003eZhang, C. L., Wang, P. Z., Wang, E. Y., Chen, D. P. \u0026amp; Li, C. Characteristics of coal resources in China and statistical analysis and preventive measures for coal mine accidents. \u003cem\u003eInt. J. Coal Sci. Technol.\u003c/em\u003e \u003cb\u003e10\u003c/b\u003e (1), 22 (2023).\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003eJiang, Y. D., Pan, Y. S., Jiang, F. X., Dou, L. M. \u0026amp; Ju, Y. State of the art review on mechanism and prevention of coal bumps in China. \u003cem\u003eJ. China Coal Soc.\u003c/em\u003e \u003cb\u003e39\u003c/b\u003e (2), 205\u0026ndash;213 (2014).\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003eDou, L., Mu, Z., Li, Z., Cao, A. \u0026amp; Gong, S. Research progress of monitoring, forecasting, and prevention of rockburst in underground coal mining in China. \u003cem\u003eInt. J. Coal Sci. Technol.\u003c/em\u003e \u003cb\u003e1\u003c/b\u003e (3), 278\u0026ndash;288 (2014).\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003eZhang, Q. H. et al. A review of rockburst prevention and control methods in tunnels: graded and classified prevention and control. \u003cem\u003eBull Eng. Geol. Environ\u003c/em\u003e \u003cb\u003e83\u003c/b\u003e(3), (2024).\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003eWang, M. Z., Cai, M., Maloney, S. \u0026amp; Dunn, M. Determination of mine-wide in-situ stress using numerical back analysis: a case study of Jwaneng mine. \u003cem\u003eInt. J. Rock. Mech. Min.\u003c/em\u003e \u003cb\u003e194\u003c/b\u003e, 106235 (2025).\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003eWang, G. \u0026amp; Pang, Y. Relationship between hydraulic support and surrounding rock coupling and its application. \u003cem\u003eJ. China Coal Soc.\u003c/em\u003e \u003cb\u003e40\u003c/b\u003e (1), 30\u0026ndash;34 (2015).\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003eWang, Q. et al. Feasibility study of synergistic anchoring and supporting in coal entry heading faces with moderately stable surrounding rock. \u003cem\u003eSci. Rep.\u003c/em\u003e \u003cb\u003e15\u003c/b\u003e (1), 15794 (2025).\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003eLi, C. G., Duan, H. M. \u0026amp; Wang, D. Q. The application of high strength anchor about compound roof support about in Guantun Coal Mine. \u003cem\u003eAdv. Mater. Res.\u003c/em\u003e \u003cb\u003e813\u003c/b\u003e, 281\u0026ndash;283 (2013).\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003eZeng, Q. L., Ma, X. Q., Wan, L. R., Zhu, Y. P. \u0026amp; Yue, Y. P. Research on the hydraulic support face guard mechanism and coupling characteristic of rib spalling in large mining heights. \u003cem\u003eSci. Rep.\u003c/em\u003e \u003cb\u003e14\u003c/b\u003e (1), 8110 (2024).\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003ePan, Y. S. et al. Theory and technology of three levels support in bump-prone roadway. \u003cem\u003eJ. China Coal Soc.\u003c/em\u003e \u003cb\u003e45\u003c/b\u003e (5), 1585\u0026ndash;1594 (2020).\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003ePan, Y., Xiao, Y., Li, Z. \u0026amp; Wang, K. Study of tunnel support theory of rockburst in coal mine and its application. \u003cem\u003eJ. China Coal Soc.\u003c/em\u003e \u003cb\u003e39\u003c/b\u003e (2), 222\u0026ndash;228 (2014).\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003eMa, J. et al. Research on the Energy-Absorbing and Cushioning Performance of a New Half-Bowl Ball Rubber Body in Tunnel Support. \u003cem\u003eProc.\u003c/em\u003e 12(9), (2024).\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003eHiroshi, M. Study on arrangements of solid balls in 3-space. (1800).\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003eHou, J., Liu, P. A., Qu, E. X. \u0026amp; Zhang, K. Mechanical performance modeling of CFRP bar-steel composite component based on ABAQUS. \u003cem\u003eJ. Phys. Conf. Ser.\u003c/em\u003e \u003cb\u003e3093\u003c/b\u003e (1), 012006 (2025).\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003eChang, J. C., Qi, C., Yin, Z. Q., Shi, W. B. \u0026amp; Gao, X. Propagation and failure characteristics of stress wave of full anchor solid under dynamic load. \u003cem\u003eJ. China Coal Soc.\u003c/em\u003e \u003cb\u003e48\u003c/b\u003e (5), 1996\u0026ndash;2007 (2023).\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003eCao, J. C., Zhang, N., Wang, S. Y., Qian, D. \u0026amp; Xie, Z. Z. Physical model test study on support of super pre-stressed anchor in the mining engineering. \u003cem\u003eEng. Fail. Anal.\u003c/em\u003e \u003cb\u003e118\u003c/b\u003e (104833), 104833 (2020).\u003c/span\u003e\u003c/li\u003e\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":"Hydraulic support, Anchor support, Buffer ball device, Impact ground pressure, Finite element simulation, Experimental study","lastPublishedDoi":"10.21203/rs.3.rs-8203278/v1","lastPublishedDoiUrl":"https://doi.org/10.21203/rs.3.rs-8203278/v1","license":{"name":"CC BY 4.0","url":"https://creativecommons.org/licenses/by/4.0/"},"manuscriptAbstract":"\u003cp\u003eFor the two support methods currently used in coal mine roadways, namely bolt support and hydraulic support, the supporting capacity of a single support method is limited under various complex conditions. The impact resistance of combined support is 30% \u0026minus;\u0026thinsp;50% higher than that of single support, which can improve the stability of coal mine roadways. However, the problems of stress concentration and impact damage caused by the protrusion of bolt ends in the collaborative operation of the hydraulic support-bolt support system have not been well solved so far.In this paper, an innovative hydraulic support top beam buffer ball device is designed, which well addresses this issue. Through laboratory tension-compression tests, the schemes of dense/loose nylon ball arrangements and the addition of rubber soft balls are compared. The data show that the loose nylon ball arrangement increases the total energy absorption by 77.8% more than the dense nylon ball arrangement. Furthermore, a finite element model is established using ABAQUS to simulate the mechanical response under impact load, verifying the effectiveness of the device.\u003c/p\u003e","manuscriptTitle":"Simulation and Experiment of Self-adaptive Device for Hydraulic Support with Roadway Anchor Bolt","msid":"","msnumber":"","nonDraftVersions":[{"code":1,"date":"2025-12-05 19:12:27","doi":"10.21203/rs.3.rs-8203278/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":"846d026b-960b-413c-bd7c-e68545f16e50","owner":[],"postedDate":"December 5th, 2025","published":true,"recentEditorialEvents":[],"rejectedJournal":[],"revision":"","amendment":"","status":"posted","subjectAreas":[{"id":59041792,"name":"Physical sciences/Energy science and technology"},{"id":59041793,"name":"Physical sciences/Engineering"}],"tags":[],"updatedAt":"2026-01-16T11:33:21+00:00","versionOfRecord":[],"versionCreatedAt":"2025-12-05 19:12:27","video":"","vorDoi":"","vorDoiUrl":"","workflowStages":[]},"version":"v1","identity":"rs-8203278","journalConfig":"researchsquare"},"__N_SSP":true},"page":"/article/[identity]/[[...version]]","query":{"redirect":"/article/rs-8203278","identity":"rs-8203278","version":["v1"]},"buildId":"8U1c8b4HqxoKbykW_rLl7","isFallback":false,"isExperimentalCompile":false,"dynamicIds":[84888],"gssp":true,"scriptLoader":[]}