Surface Subsidence Control Research Articles

Experimental Research on the Performance of All-Solid-Waste Cementitious Grouting Filling Materials

Overburden bed separation grouting is a green mining method to control surface subsidence and protect surface buildings (structures). The performance of cementitious grouting material is the key factor affecting grouting filling. Although offering good fluidity and low cost, the fly ash (FA) slurry demands a significant water supply, undergoes high dehydration rates, and lacks cementing property. These factors result in low grouting efficiency and negatively impact the safety of operations in complex-structure areas. This work developed a CBF + D series all-solid-waste cementitious grouting filling material with blast furnace slag (BFS), FA, carbide slag (CS), desulfurization gypsum (DG), and calcium chloride (CaCl2) as components. Based on the orthogonal test, the basic performance test of the grouting material was carried out using macroscopic and microscopic test methods. The influences of the water–cement ratio, the mass ratio of BFS to FA, the proportion of CS, and the proportion of DG on the slurry density, fluidity, water extraction rate, and uniaxial compressive strength (UCS) of the stone body were assessed. The material’s hydration mechanism was analyzed by combining X-ray diffraction (XRD) and scanning electron microscopy (SEM) microscopic experiments. The optimal parameters for this test were as follows: a water–cement ratio of 0.7, a mass ratio of BFS to FA of 3:1, a proportion of CS of 40%, and a proportion of DG of 4%. Under the optimal conditions, the density of the slurry was 1.41 g·cm−3, with a fluidity of 15.7 cm, a water extraction rate of 0.107, and a UCS of the stone body of 6.25 MPa. The water extraction rate of the slurry is 67% lower than that of the FA slurry and the slurry has good cementation performance, while still maintaining its fluidity. This significantly enhanced the safety and applicability of the grouting filling process. In addition, CBF + D series all-solid-waste cementitious materials have solved the large accumulation of industrial wastes such as FA, BFS, and CS, which maximized the resource utilization rate of these wastes and brought significant economic benefits.

Bending properties and damage evolution of fiber-reinforced aeolian sand backfill materials

Backfilling is a promising measure for controlling surface subsidence in mined-out areas and disposing solid wastes from the mineral processing, there are increasing demands of enhanced toughness and anti-cracking properties of backfill materials to prolong the service life under the complex loads. In this study, polypropylene (PP) fibers were employed to improve performance of backfills, four-point bending and uniaxial compression tests were conducted to investigate the failure process and damage evolution of fiber-reinforced aeolian-sand backfill materials (FABs) using Digital Image Correlation (DIC) and Acoustic Emission (AE) techniques. The results show that the compressive strength tends to decrease with the increasing fiber volume fractions, while the four-point bending strength shows a tendency to increase initially and then decrease, and the optimum volume fraction of PP fiber is 0.6%. At the optimal fiber volume fraction, PP fibers with lengths of 3 mm and 9 mm resulted in a 65.25% and 81.62% increase in the four-point bending strength of FABs, respectively. As indicated by DIC measurements, PP fibers with a length of 9 mm were more effective in controlling the horizontal and vertical displacements of FABs under four-point bending loads than that of 3 mm, and the cracks developed more slowly at the same deflection. In addition, PP fibers with a length of 9 mm have stronger crack extension delay characteristics due to longer effective anchorage distance, as evidenced by more frequent acoustic emission ringing counts and higher cumulative ringing counts. The results of the study may provide a theoretical basis for the application of FABs materials in backfilling.

Subsidence Prediction Method Based on Elastic Foundation Beam and Equivalent Mining Height Theory and Its Application

Grouting technology in overburden separation is recognized as an effective method to prevent surface subsidence and reuse solid waste. This study used mechanical analysis to explore deflection characteristics of key strata and accurately predict and control surface subsidence. Conceptualizing the coal–rock mass beneath the key strata as an elastic foundation, we developed a method to calculate the elastic foundation coefficients for various regions and established an equation for key strata deflection, validated through discrete element numerical simulations. This simulation also examined subsidence behavior under different grout injection–extraction ratios. Additionally, combining the equivalent mining height theory with the probability integral method, we formulated a predictive model for surface subsidence during grouting. Applied to the 8006 working face of the Wuyang Coal Mine, this model was supported by numerical simulations and field data, which showed a maximum surface subsidence of 546 mm at a 33% injection–extraction ratio, closely matching the theoretical value of 557 mm and demonstrating a nominal error of 2%. Post-grouting, the surface tilt was reduced to below 3 mm/m, meeting regulatory standards and eliminating the need for ongoing surface structure maintenance. These results confirm the model’s effectiveness in forecasting and controlling surface subsidence with grouting. The study can provide a basis for determining the grouting injection–extraction ratios and evaluating the effectiveness of surface subsidence control in grouting into overburden separation projects.

WITHDRAWN: Characterization of soil response in mining with grouting into overburden bed-separation based on similar material simulation

Revealing the response laws of soils under various mining conditions is of significance for the scientific protection of farmland in mining areas. To avoid the interference from the spatial heterogeneity of natural soil on the research results, similar simulation experiments were employed. Two models for soil responses under mining with and without grouting into overburden bed-separation were designed, and monitoring was conducted for soil quality factors (moisture content, silt and clay content, and bulk density) and surface deformation factors (subsidence, inclined, and horizontal deformation). The results indicate that it can significantly control surface subsidence in mining with grouting into overburden bed-separation, the maximum subsidence value was reduced by 66.67%, the average subsidence value of each measuring point in the main section was reduced by 78.92%, and the subsidence area was reduced by 34.68%. The coefficient of variation of soil quality factors in the mining-affected area was obviously higher than that in the control area and the initial value before mining. Compared with mining without grouting, the variation coefficient of soil quality factor under mining with grouting was reduced by 2.71-6.79%. Soil quality factors and surface deformation factors show a significant quadratic function relationship, among which horizontal deformation has the greatest influence on soil quality factors, followed by subsidence and inclination. Therefore, it can effectively control surface subsidence and protect cultivated land when mining with grouting into overburden bed-separation.

Near Real-Time Monitoring of Large Gradient Nonlinear Subsidence in Mining Areas: A Hybrid SBAS-InSAR Method Integrating Robust Sequential Adjustment and Deep Learning

With the increasing availability of satellite monitoring data, the demand for storage and computational resources for updating the results of monitoring the surface subsidence in a mining area continues to rise. Sequential adjustment (SA) models are considered effective for rapidly updating time series interferometry synthetic aperture radar (TS-InSAR) measurements. However, the accuracy of surface subsidence values estimated through traditional sequential adjustment is highly sensitive to abnormal observations or prior information on anomalies. Moreover, the surface subsidence associated with mining exhibits nonlinear and large gradient characteristics, making general InSAR methods challenging for obtaining reliable monitoring results. In this study, we employ the phase unwrapping network (PUNet) to obtain unwrapped values of differential interferograms. To mitigate the impact of abnormal errors in the near real-time small baseline subset InSAR (SBAS-InSAR) sequential updating process in mining areas, a robust sequential adjustment method based on M-estimation is proposed to estimate the temporal deformation parameters by using the equivalent weight model. Using a coal backfilling mining face in Shanxi, China, as the study area and the Sentinel-1 SAR dataset, we comprehensively evaluate the performance of unwrapping methods and subsidence time series estimation techniques and evaluate the effect of filling mining on surface subsidence control. The results are validated using leveling measurements within the study area. The relative error of the proposed method is less than 5%, which can meet the requirements of monitoring the surface subsidence in mining areas. The method proposed in this study not only enhances computational efficiency but also addresses the issue of underestimation encountered by InSAR methods in mining area applications. Furthermore, it also mitigates unwrapping phase anomalies on the monitoring results.

Study on the Movement of Overlying Rock Strata and Surface Movement in Mine Goaf under Different Treatment Methods Based on PS-InSAR Technology

The goaf treatment of underground metal mines is an important link in mining, and it is particularly important to master the laws of overlying rock strata and surface movement of goaf. In this paper, Persistent Scatterer Interferometric Synthetic Aperture Radar (PS-InSAR) technology is used to monitor the surface subsidence of the Taibao lead-zinc mine, and the surface subsidence laws of goaf-closure, partial-filling, and full-filling treatments are analyzed by the time-series method. The findings indicate that the surface subsidence of the closed goaf is solely governed by the pillars, with the quality of these pillars playing a pivotal role in controlling such subsidence. Factors like stope span also influence the surface subsidence of partially filled goaf. Prior to compaction, it is primarily the pillars that control surface subsidence; however, after compaction, filling and pillars jointly regulate this phenomenon. Notably, in filled goaf, the quality of both roof and pillars significantly impacts surface subsidence. Before compaction occurs, control over surface subsidence is not evident, yet post-compaction, the filling is effective and tends to stabilize this process. The research findings are significant in enhancing goaf’s treatment efficacy, mitigating surface damage and minimizing ecological environmental impact.

A design approach of panel size for the cooperative development of cropland protection and coal mining in a coal-cropland overlapping area.

Cropland is the foundation of food security. Coal is the guarantee of energy security. As China's demand for coal and grain continues to increase, so does the overlap area of their production bases. Unrestrained underground mining can cause serious damage to cropland, leading to increasing conflicts between coal mining and food production. Thus, this paper used a partial backfilling mining technology to control surface subsidence and thus protect cropland. The key to successfully implementing the technology is how to design the panel size. However, the design efficiency of the conventional enumeration method is low. Therefore, this paper proposed a design approach based on improved particle swarm optimization. The results indicated that the approach could quickly find the optimal size of the panel compared with the enumeration method and particle swarm optimization. Moreover, if the longwall panel is mined according to the size designed by the approach, the cropland will be protected, and the cost will be reduced. This study can provide technical support for the cooperative development of cropland protection and coal mining in a coal-cropland overlapping area.

Experimental study on failure characteristics and rheological properties of pillar-like rock samples with different shapes

The stability of coal pillar is extremely important to the control of rock strata movement and surface subsidence. It is of great significance for mining design to analyze the stability and failure characteristics of coal and rock pillars left after mining and to study the failure characteristics and rheological properties of coal and rock with different shapes. In this paper, based on uniaxial compression and rheological tests on rock samples, the rheological properties of rock samples with different shapes were discussed by using the nonlinear theoretical mechanics and damage theory, and the rheological mechanical characteristics of coarse yellow sandstone samples under the action of different free surface areas and the same loading contact area were investigated by means of experimental research, theoretical analysis and numerical simulation. The following conclusions were drawn: the failure characteristics and dynamic change process of rock samples with different shapes under the same loading contact area are obtained by uniaxial compression test and multi-stage rheological loading. The uniaxial compressive strengths of rock samples with the same loading contact surface area and different free surface areas are inversely proportional to their free surface areas. For the round sample, the stress level in the rheological test is obviously lower than the instantaneous peak uniaxial compression strength, while for the other samples, the stress level in the rheological test is close to the instantaneous peak uniaxial compression strength. For rock all these samples, both the ratio of steady-state rheological time to final failure time and the deformation degree decrease with the increase of free surface area.

Solid waste filling and roadway retaining for longwall mining by numerical investigation

Solid waste filling and roadway retaining can effectively control surface subsidence and alleviate solid waste accumulation pollution. In order to effectively evaluate the advantages of solid waste filling in deformation control of overlying strata and surrounding rock of retained roadways, this study used theoretical analysis and numerical simulation methods to analyze the factors affecting surface subsidence, as well as the deformation characteristics of surrounding rocks and retaining tunnels during backfill mining. By calculating the influence of factors such as the foundation coefficient and the filling rate on the subsidence of the roof, it is concluded that the filling rate is the main controlling factor affecting the subsidence of the roof. Through simulation and comprehensive analysis of the impact of different filling rates on overlying rock migration, it was found that when the filling rates are 70 % and 80 %, it can effectively control the subsidence of overlying rock in the mining area. By simulating the effects of these two filling rate conditions on the deformation of surrounding rock within the retained roadway zone, the results show that the optimal filling rate that can effectively control the subsidence of the overlying rock and improve the stability of the retained roadway is 80 %.

Study of the Overlying Strata Movement Law for Paste-Filling Longwall Fully Mechanized in Gaohe Coal Mine

Green mining plays a vital role in achieving environmentally friendly and ecologically sound mining practices. In domestic mining areas, the coal mining method is gradually transitioning from collapse mining to filling mining. Paste filling has been proven effective in controlling surface deformation, although the understanding of its underlying control mechanisms remains incomplete. This study focuses on the E1302 paste-filling working face at Shanxi Gaohe Energy Co., Ltd. and conducts a comprehensive investigation into the movement patterns of overlying strata in longwall fully mechanized mining with paste filling. Through mathematical analysis, a mechanical model for overburden movement in paste-filling faces is established, and the movement behavior of overburden is studied through numerical simulations. Field measurements are conducted to analyze the primary influencing factors of overburden movement, while surface subsidence monitoring is employed to analyze the subsidence characteristics of paste-filling faces. The research reveals that the deflection formula for the roof behind the paste-filling face follows a unitary quartic equation. The key factors influencing significant roof subsidence in filling faces include the filling step distance, filling body strength, and filling rate. Compared to traditional caving mining, filling mining exhibits reduced stress concentration, a smaller range of stress influence, and less deformation in the surrounding rock. The coefficient of gentle subsidence for the overlying rock in filling mining is approximately one-tenth of that in caving mining. The development of cracks in filling mining can be divided into three stages: initial crack propagation, crack recompaction, and stable maintenance of cracks. Notably, the progression of advanced cracks assumes a “sail-shaped” pattern, and the area of crack recompaction is located above the rear side of the excavation. Cracks behind the working face only appear in the basal roof rock layer. When the filling rate in longwall fully mechanized mining with paste filling exceeds 94%, the top plate of the filling working face remains intact but exhibits bending and sinking. The sinking of the top plate increases exponentially with the filling step distance, and approximately 80% of the filling body’s deformation occurs within 20 m after filling. Following backfilling mining, the stability period of the overlying rock is significantly shortened compared to caving mining, resulting in a relatively gentle movement without an active surface movement phase. After six months of backfilling, the overlying rock settles steadily and consistently. The subsidence coefficient for backfilling mining is 0.065, with a maximum surface subsidence of 215 mm. These findings highlight the successful control of surface subsidence. The research outcomes provide an effective theoretical foundation and research direction for predicting overburden movement and surface subsidence in paste-filling faces.

Compaction Response of Mining-Induced Rock Masses to Longwall Overburden Isolated Grouting

Surface subsidence in coal mine areas can cause serious geological hazards. After a coal seam is mined, the overlying rock layers fracture, collapse, and expand; the fractured and bulking rock masses are then continuously compacted under the action of overburden load, which eventually leads to surface subsidence. Overburden isolated grout filling via surface boreholes, and high-pressure grouting to mining-induced fissures under the hard rock layer, uses the grouting pressure to compact the lower fractured and bulking rock masses in advance, replacing the subsidence void and effectively controlling the surface subsidence. The characteristics of rock mass collapse, bulking, and compaction associated with mining and grouting are the key to the design of grouting parameters and surface subsidence control. In this paper, a theoretical model of the rock masses’ compactness during grouting injection is proposed, which determines the compaction of rock masses under the action of grouting filling. An experimental study was conducted to reproduce the grouting pressure evolution and the rock masses compaction in response to grout filling. The results indicated that the rock mass compaction was small in the no-pressure stage, and that the low-pressure and pressure-boost stages were key to generating the compaction effect of the grout filling. It was found that compaction grouting substantially increased the filled volume by transforming the fractured and bulking space of the rock masses into a filled space. Using engineering measurement data, the rock masses compaction law for grouting is verified. This paper provides a theoretical basis for the design of overburden grouting parameters and the evaluation of subsidence control effectiveness.

A New Method of Regional Mining Subsidence Control for Sustainable Development in Coal Areas

Coordinated and sustainable development of production-living-ecological space (PLES) is directly related to the global energy security and quality of life in coal areas. However, the current surface subsidence control methods have some problems, such as low resource recovery rate, high cost, insufficient materials, which are difficult to meet the requirements for the PLES sustainable development in coal areas. Under this background, based on characteristics of surface subsidence and deformation due to sub-critical extraction, the large protection area, and high deformation tolerance in PLES of mining areas, the new method of regional mining subsidence control was proposed, with the combination of source control and ground rehabilitation. The effectiveness of the method was verified by numerical simulation results and practical applications, and the application principles and implementation methods were proposed. The research results could provide technical support for the sustainable development of coal areas in major coal producing countries of the world.

Properties of a backfill material prepared by cementing coal gangue and fly ash through microbial-induced calcite precipitation

Microbes can induce the production of calcium carbonate deposits, which cement solid wastes such as coal gangue to form backfill materials. Filling such backfill materials in underground goafs can facilitate the disposal of solid wastes and control surface subsidence. In view of this, the idea of preparing a backfill material by cementing coal gangue and fly ash through microbial-induced calcite precipitation (MICP) induced by B. pasteurii was proposed and the preparation procedure and test methods of properties of the backfill material were introduced. Changes in the slump flow and bleeding rate of the backfill material under conditions of different bacterial concentration, urea concentration, and mass concentration were studied. Influences of factors including the bacterial concentration, urea concentration, mass concentration, curing time, and curing temperature on the compressive strength of the backfill material were estimated. Results show that as the bacterial concentration increases, the slump flow increases, the bleeding rate decreases, while the compressive strength of the backfill material increases. An increase in the urea concentration reduces the slump flow and bleeding rate of the backfill material while first increasing, then decreasing the compressive strength; excessive concentrations of urea suppress bacterial activities. An increase in the mass concentration decreases the slump flow and bleeding rate of the backfill material, while increasing the compressive strength. As the curing temperature is increased, the compressive strength of the backfill material first increases, then decreases and the temperature range of 30 ∼ 40℃ is more conducive to bacterial hydrolysis of the urea and chemical reactions in the coal gangue-fly ash slurry. The prolonged curing time can significantly improve the compressive strength of the backfill material. The research results provide a theoretical basis for the application of microbial-induced calcite precipitation (MICP) in backfilling mining of coal mines.

Slurry Leakage Channel Detection and Slurry Transport Process Simulation for Overburden Bed Separation Grouting Project: A Case Study from the Wuyang Coal Mine, Northern China

The 8006 working face at the Wuyang Coal Mine adopts grout injection into bed separation technology for surface subsidence control. Surface grout leakage occurred during the grout injection into the bed separation process of this working face. Grout leakage has adverse effects on the grouting filling effect, grouting cost and the environment. To determine the grout leakage channels and the slurry transport process, and to provide a theoretical basis for slurry leakage prevention and control, this paper first used 3D seismic exploration technology to identify the fault distribution characteristics of the study area, and then used COMSOL Multiphysics to carry out the numerical simulation of the grout transport process. The conclusions are as follows. Fifteen normal faults were identified in the vicinity of the 8006 working face. Among all the faults, the F1, F11, F18, F19 and F27 faults penetrate the surface and are the main channels for the grout to run to the surface. Based on the distribution characteristics of the faults and the spatial location relationship among the bed separation, faults and grout leakage points, the theoretical analysis of the leakage causes of each grout leakage point was carried out, and the main leakage channels of the grout injection into bed separation were proposed to be the bed separation and faults. The results of the numerical simulation of grout transport show that, as the permeability of the bed separation space and fault is much better than that of the surrounding rock, during the grout injection process the grout diffuses through the bed separation and fault in turn, and finally to the surface, where leakage occurs. The simulation results confirm that the main leakage channels for the grout are bed separation and faults.

The Influence of Pile-Beam-Arch Construction on the Stratum and Station Support Structure

The PBA construction method is suitable for urban subway construction in situations with dense traffic and many surrounding buildings and can effectively reduce surface disturbance and control surface subsidence. Based on field-measured data, this study creates numerical finite element models of 3D stratum-structure, studies the influence of each process conversion on the subsidence of the ground surface and the force of the station supporting structure during the construction of the PBA station, and clarifies the optimal construction parameters. The research results show that the consistency between the field monitoring data and the simulation data is more than 80%, which verifies the correctness of the model. It is concluded that the formation of the pile-beam-arch is the main part of the supporting structure and that digging the pilot tunnel and the formation of the beam arch are the control factors of surface settlement. Based on this, the best sequence of pilot tunnel excavation and arch buckle of the two-story two-span station is obtained, and the optimal pilot tunnel excavation scheme of first the middle and then the side, first the upper and then the lower, and the best arch buckle scheme of the synchronous arch buckle on both sides is determined. The results of the research can serve as a guideline when selection the construction parameters for similar PBA stations.

Experimental method and application of the slurry “diffusion-bleeding-seepage” of isolated overburden grout injection

Isolated overburden grout injection (IOGI) is a green mining method to control surface subsidence. Slurry water significantly influences grouting effectiveness and mining safety. This study establishes a three-dimensional visualization experimental system for slurry “diffusion-bleeding-seepage” to investigate the seepage law of slurry water. The system is composed primarily of a transparent box (1.2 m × 0.5 m × 0.25 m) and support, with the solid–liquid coupling seepage similar material and modules for mining, grouting injection, slurry pressure and displacement monitoring, overburden saturation monitoring, and water leakage monitoring of the working face. A similar material with good permeability and non-disintegration is obtained by hydrophilic, water absorption, and permeability tests. Grouting and mining are simulated by pulling acrylic sheets and pumping slurry. With the fly ash slurry entering the injection layer, the slurry undergoes water–cement separation, and the water bleeding is formed to seep into the similar material. The volumetric water content of the similar material is obtained by arranging multiple groups of volumetric water content sensors into the similar material. The corresponding saturation is obtained by theoretical calculation. The experimental system is used to simulate the seepage of slurry water in a high initial saturation overburden, and the characteristics of injection slurry diffusion and water bleeding are obtained. The profile distribution of seepage of slurry water is found to possess a semi-elliptical shape. Under the condition of high initial saturation, slurry water appears in the working face. The system provides a convenient method for further research of IOGI slurry water seepage.

Research on the Overburden Movement Law of Thick Coal Seam Without-Support Gangue-Filling Mining

Filling mining technology is a feasible and effective means to build a green mine and protect the environment. In order to investigate the overlying rock movement law of gangue-filling mining under the condition of no support for thick coal seams, this paper takes the Sima mine as the research object and determines the relevant parameters of rock mechanics in the mine area through a uniaxial compression test, a uniaxial tensile test, and a uniaxial shear test, which lay the foundation for the numerical simulation and similar simulation experiments. The optimal solution was determined by the numerical simulation, the effects of mining width and mining sequence on the overlying rock stress and deformation were analyzed, and the accuracy of the results was further confirmed by combining with similar simulation experiments. The results show that the mining sequence of jump mining with large intervals adopted in this paper can make the backfill solidify fully and is more conducive to the working face support and roof management. The larger the mining width, the larger the deformation of the overlying rock seam and the surface. It shows that the smaller the mining width, the smaller the increase of stress caused by excavation and filling, which is more favorable to the stability of the coal column and filling body. This paper deals with coal mine solid waste, while realizing the effective control of surface subsidence and providing a theoretical basis for the construction of green mines.

Overlying Strata Movement and Mine-Pressure Weakening Law of High-Efficiency Longwall Paste Backfilling of Thick Coal

This work focused on the serious coal compression under buildings, railways, and water bodies in central and eastern China; the wide range of rock formation damage during the collapse mining process; the high pressure of mines; and difficulties in controlling surface subsidence after mining. The E1302 working face of Shanxi Gaohe Energy was taken as the engineering background in the work. The mechanical properties of gangue paste-filling materials were studied through laboratory tests, and the critical conditions for bending and fracture of the coal seam roof were analyzed. Discrete-element numerical simulation software was used to study the fracturing process of the roof, and the reasonable filling rate to ensure roof stability was determined to be 95%. Meanwhile, overlying stratum movement and mine-pressure weakening law were studied through numerical simulations and field measurement. The results showed that fracture development during the mining process of thick-coal paste filling was divided into the advanced development, re-compaction, and steady-state maintenance of fractures. Fractures advanced in a “sail shape” and developed only in the main-roof rock strata after recompaction. The maximum subsidence angle of the working face was 87.13° after mining, with a subsidence factor of 0.034 and a maximum horizontal movement coefficient of 0.71. The advanced stress value was weakened by 40%, and the influenced area was reduced by 13%. Overlying stratum movement was controlled, and mine pressures were significantly weakened. The work can provide a scientific basis for green backfill mining, roadway support design, and backfill mining equipment selection.

Investigation of the Effectiveness of a New Backfilling Method: “Multi-Arch Pier-Column”

Owing to the shortcomings of blindness and inaccuracy when backfilling in goafs and based on the key stratum theory, we propose the “multi-arch pier-column” backfilling method. This method involves drilling holes at specific locations on the surface to inject filling and slurry materials into the goaf and separation area under the key stratum. This allows the broken gangue to be cemented to form a stone body, to improve its overall strength. This process, along with filling in the separation area under the key stratum, ensures that the key stratum does not break, forming a joint medium of “separation area filling body + backfilled pier-columns + key stratum + coal column”, which prevents new subsidence on the surface layer. Using the Gaojialiang coal mine as an example, the effects of the proposed method on controlling surface subsidence were determined using a numerical simulation based on FLAC3D simulation software. The results indicate that this method can effectively control the key stratum and ensure that the surface subsidence is within a safe range. The multi-arch pier-column backfilling method utilises the self-bearing capacity of the overburden structure and greatly reduces the backfilling workload and the cost of backfilling for controlling surface subsidence. At present, the multi-arch pier-column system of the new backfill method is an unexplored and new area of research.

New surface subsidence control technology based on upward backfilling method of bottom drainage roadway

New surface subsidence control technology based on upward backfilling method of bottom drainage roadway