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Surface subsidence induced by underground mining is one of the challenging problems in mining engineering, which can destroy ground surface buildings and cause huge economic losses to the mine. In this study, a two-dimensional numerical model, established by the discrete element method code PFC2D, was adopted to investigate the mechanical mechanism of surface subsidence and backfill material movement induced by underground mining in the Hongling lead-zinc mine. In the first simulation case, the ore body was excavated from the ground surface to the mining level 705 m by the sublevel caving mining method, and the stress evolution during the mining process was analyzed to reveal the mechanical mechanism of surface subsidence. In the second and third simulation cases, the mined-out areas above 905 m were backfilled by the noncemented tailings and an insulating pillar was reserved beneath the backfill material, and then the deep ore body was excavated by two different mining methods to study the movement law of the backfill material and rock strata induced by underground mining. The numerical simulation results show that when the sublevel caving mining method is adopted, underground mining can induce toppling failures in the hanging wall and lead to a large collapse pit in the ground surface. After the toppling failures in the hanging wall, the collapsed waste rock in the mined-out area can provide support force for the surrounding rock and restrict the further collapse of the hanging wall. Furthermore, when the cut-and-fill mining method is adopted for the excavation of deep ore body, the insulating pillar can restrict the horizontal displacement of surrounding rock and maintain the stability of the backfill material. The cut-and-fill mining method can efficiently control the surface subsidence and prevent the occurrence of collapse pit in the ground surface and is recommended for the Hongling lead-zinc mine to solve the surface subsidence problem.

Surface subsidence induced by underground coal mining activities, especially longwall mining operations, can cause various problems to interstate highways ranging from structural integrity, drivability to safety. Accurate subsidence prediction, correct influence assessments, and effective mitigation measures are the keys to ensure the safety of highway traffic. The surface subsidence prediction program, called comprehensive and integrated subsidence prediction model (CISPM), was developed based on the principle of influence function method and has been validated with a large number of subsidence measurements. In this paper, the techniques to use the predicted final surface movements and deformations for assessing their influence on the integrity and functionality of highway structures (e.g., road surface pavements, concrete slabs, transverse joints, etc.), vehicle dynamics, comfort level, and drivability are presented. A number of mitigation measures to protect the highway structures and to ensure traffic safety are proposed along with an application case.

The Sentinel-1 data is currently the latest free SAR data and is well suited for land subsidence monitoring based on InSAR technology due to its 6-day revisit cycle. In this paper, the urban area and surrounding areas of Handan City are used as research areas, and 29 scences of S1A data (December 2017 – December 2018) was used for time series SBAS processing. The results shows that the surface cumulative deformation ranged from -42 to 30 mm in most regions of Handan City. The maximum settlement is 69 mm, which is near the Hankuang Group Julong Company. The areas where the settlement is obvious include Wu'an City, Daishan Village, Dashe Town, Zhangxibao Town, Baijia Street, Dongxingtai Village, Gaonan Village and Hankuang Group Julong Company. Slightly elevated in the southeast of Handan City.

To define the deformation of time and space during the construction of a long and deep foundation pit in collapsible loess, the field-measured data of 10 open excavation stations in Xi’an metro are analyzed statistically. The results indicate that the vertical deformation of the ground and the lateral deformation of the soldier pile caused by the excavation of a long and deep foundation pit in collapsible loess increase with time. The maximum surface subsidence decreases with the increase in stiffness (K) of the foundation pit support system, increases linearly with the excavation depth (Hw), and decreases with the increase in the aspect ratio of the foundation pit. The lateral maximum deformation value of the soldier pile decreases linearly with the increase in insertion ratio and decreases with the increase in K of the support system. The surface subsidence of the foundation pit is characterized by a “groove shape”, and the deformation of the soldier pile is characterized as the “medium convex”. These results can provide a reference for the design and construction of similar projects in loess areas, and can predict and evaluate the deformation size and safety of similar projects, which is of great significance for further understanding the deformation mechanism of deep foundation pits in loess areas, thus perfecting the design theory and preventing foundation pit accidents.

Gangue, produced from coal mining and washing process, is a serious threat to the ground environment. Gangue backfilling mining method can solve this problem and reduce mining-induced hazards, e.g., controlling surface subsidence and preventing water inrush from seeping into goaf by cracks in overlying strata. In this paper, effects of the original particle size distribution (PSD) and water content on the particle crushing behavior and seepage properties of granular gangues were investigated. Experimental results show that the crushing behavior can promote the compaction of gangue particles; the variation of PSD after crushing reveals distinct fractal characteristics. With the increasing compression stress, the particle crushing ratio and fractal dimension increase, while the permeability decreases. Due to the rearrangement of particles and newly generated fine particles filled the gap among larger particles, it is difficult to reduce the permeability by increasing the compressive stress. In addition, the variation of fractal dimensions is similar to the crushing ratio, so the particle crushing can be illustrated by fractal dimensions. The relationship between porosity and permeability established by the Kozeny-Carman equation can model the effect of particle crushing in this research. The reliability of the equation is verified by the comparison of model result and experimental data. To increase the mitigation rate of mining-induced hazards and environmental pollution by GBM method, granular gangues can be crushed into smaller particles and dehydrated before backfilling.

A ‘pit in pit’ is a common problem in the excavation of foundation pits and yet this issue has not been researched systematically. The variability of its form not only complicates the condition of the surrounding stress and displacement fields, but also brings difficulty to design and construction. This paper analyses the surface subsidence features of pit-in-pit foundations based on the typical sand–cobble stratum in the Beijing area by applying finite-difference software. According to a comparison of three factors that affect the surface subsidence the most, a conclusion can be drawn that the depth of the inner pit is greater than the edge distance (from the inner pit to the wall of the outer pit), which is greater than the width of the inner pit. The application of stratum compensation theory to pit-in-pit engineering is discussed to analyse the relationship between the surface deformation and lateral displacement of retaining walls. The cause of inaccuracy is also discussed, although this was found to be within acceptable limits. The research findings provide guidance for engineering inspections and control during construction in pit-in-pit foundations in sand–cobble and other similar strata.

Most prediction methods used to calculate mining-induced subsidence are empirical, which cannot explain the mechanism of fundamental rock strata movement. In this paper, based on key stratum theory and the mechanical analysis of overburden, a new analytical solution, the Analogous Hyperbola Subsidence Model (AHSM), was proposed to describe the movement and damage of inner burden. Mining-induced rock strata movement was verified using the Distinct Element Method (UDEC), to assess the performance of the theoretical model. Three subsidence parameters (Smax/T, Sgoaf/Smax, D/H), generally used to describe surface subsidence trough, agree with statistical field measurements of the South Coalfield in Australia. The surface subsidence and the movement boundary in the overburden are very close to the theoretical predictions. Additionally, the primary key stratum damages the least in the overlying strata: its broken length is the smallest. The width of subsidence trough and maximum surface subsidence increase as the primary key stratum drops.

Shallow coal seam exploitation not only causes serious surface subsidence but also induces extensive ground fissures, which severely threaten the safety of underground mining and the surface eco-environment. We use the Daliuta coal mine of the Shendong mining district in China as a case study to investigate and characterize the influence of underground coal mining on the development of ground fissures. A new comprehensive impact parameter K of geology and mining for ground fissure development is introduced to explain the effects of mining speed on the developmental features of ground fissures. The results show that ground fissures often develop in the surface tensile zone ahead of the working face advancing position and show an inverted C-shape on the surface, which is similar to periodic fracturing of the basic roof. The ground fissure angle increases linearly with mining speed and logarithmically with K, while the developmental cycle decreases linearly with mining speed. We propose a technical measure to control ground fissure disasters by adjusting mining speed, which provides a theoretical reference for eco-environmental governance in shallow coal seam mining districts.

The exploitation of underground resources can lead to overburden deformation and destruction, surface subsidence with fissure development. In order to reveal the evolution laws of land damage in mining process, the paper used resistivity imaging technology to test the spatio-temporal evolution of surface soil cracks caused by underground mining. Access to land under the influence of mining damage evolution process of the whole cross-section resistivity data volume. Grasp the spatio-temporal evolution of electrical resistivity at overlying geotechnical and surface fissures during the entire mining process. The results show that: With the advance of working face, dynamic cracks in mining appear one or more “cracking–closing” processes. Dynamic fissures always develop ahead of the current working location, advance angle of break is approach to vertical angle. It indicates that dynamic fissures have fast “selfhealing” features and manual repairmen might not be necessary. Electrical resistivity imaging technology is sensitive to the change of soil micro structure. The development and failure depth of cracks in layered soil can be accurately reflected. At the same time, the deformation and failure of overlying surrounding rock caused by mining influence can also be obtained through this monitoring method. The electrical data monitoring results are basically consistent with the results obtained by actual close-range photography technology, indicating that it is feasible to use the resistivity imaging technology to monitor the evolution law of land damage caused by mining of working face. This achievement and understanding can provide technical support for the study of land ecological damage caused by coal mining.

With the continuous reduction of coal resources, mining conditions become more and more complex, showing a trend of deep and large dip. There are two main problems in the mining of high dip seam: on the one hand, the roof caving characteristics of high dip seam mining are more complex, and the solution of this problem is helpful to formulate a reasonable and effective support scheme for the roof in the production process of coal mine; on the other hand, the characteristics of surface subsidence caused by mining of high dip seam, which is related to the prediction and prediction of surface subsidence. Prevention and cure. Based on this, firstly, according to the knowledge of elasticity mechanics, the mining dynamic model of high dip coal seam is established; secondly, the geological model of high dip coal seam is established by using the simulation numerical software FLAC3D, and the excavation process is simulated; finally, the excavation of the working face with 40 m and 14 m coal pillars is simulated by FLAC3D. The results show that the mining of high dip coal seam will cause a large amount of surface subsidence, which will seriously affect the surrounding rock by stress concentration. After setting 40 m and 14 m coal pillars, the serious problems of surface subsidence and surrounding rock destruction caused by mining can be effectively reduced.

This paper presents the stability assessment of a century old coalmine situated under a railway track. The mine openings may lead to the surface subsidence which can endanger the track safety. To assess the stability, this paper presents a unified approach of observational, empirical, and analytical methods. Observational approach monitored the immediate roofs with geotechnical instruments during a period. In empirical approach, the coal pillar safety factors were assessed using rock mass classification. Finally, the analytical study was performed using numerical simulation. All these studies found that the openings and the coal pillars are stable for the track safety.

Igneous rock often appears in coal measure strata, and its occurrence, size, and distribution play important roles in mining safety. The failure of hard and thick igneous rocks can result in dynamic disasters such as rock burst, mine seismicity, gas outburst, and surface subsidence, all of which seriously threaten the safety of mine production. The fracture failure step distance of the hard and thick igneous rock was deduced based on the occurrence law of microseismic (MS) events, the characteristics of surface subsidence, and the change law of support resistance in the 10416 working face at Yangliu coal mine (YLCM). And this study used the theoretical analysis method to deduce the calculation method of the fracture failure of hard and thick key strata. Based on plate yield line theory and the energy method, the hard, thick critical layer collapse mechanism and the calculation expression of fracture step distance were obtained under the condition that three edges are clamped and one edge is simply supported. The fracture failure step distance of the hard and thick igneous rock that was obtained through field measurement and analysis were approximately identical with those calculated by the theoretical formula, verifying the accuracy of the theoretical calculation process and the results. Results of this study can guide the prevention and control of dynamic disasters and the roadway support design under the condition of overlaying the hard and thick key layer on the working face.

Coal mining results in surface subsidence and make ecological environment more fragile. The dynamics of arbuscular mycorrhizal (AM) fungi response to host plants, slope position and subsidence have been investigated at the Shendong Bulianta coal mining area in north-central China. A total of 57 AM fungal operational taxonomic units (OTUs) were identified and subdivided into five genera. It was noticed that at the top slope position, the AM fungal infection and extraradical hyphal (ERH) density were significantly higher than at the middle and bottom, AM fungal diversity indices showed a significant decrease with the increasing slope position. Significantly different phylogenetic indices were observed among the three host plants. In addition, the AM fungal ERH density and phylogenetic index were observed to be significantly higher in areas without subsidence. Soil available P and pH significantly influenced AM fungal infection and ERH density. The findings highlight that host plants, slope position and subsidence has strong influence on AM fungal community via edaphic variables change. This study provided the groundwork to further clarify AM fungal ecological function, which can potentially help in vegetation restoration and reduced erosion in coal mining areas.

Fly ash cement is used to solidify marine clay to prepare marine-clay-based cemented paste backfill (MCCPB) to fill the underground goaf of mines, which not only utilizes solid waste such as fly ash and marine clay, but also controls surface subsidence and protects the environment. To simulate the complex underground mine water environment of the filling body, a dry-wet cycle aquatic environment test under different material ratios and curing ages was designed. The water absorption and unconfined compression strength (UCS) of MCCPB with curing ages of 7 and 28 days under the action of 0, 1, 3, and 7 dry-wet cycles were investigated. The results indicate as the number of dry-wet cycles increases, the surface of MCCPB becomes significantly rougher, and the water content and the solid mass decrease accordingly. Different ratios and curing ages of MCCPB in dry-wet cycles of the UCS tend first to increase, then decrease. Meanwhile, the stress-strain curve of the specimen shows that the trend in the elastic modulus is consistent with that of UCS (first increasing, then decreasing), and that, the minimum UCS value of the specimen still meets the early strength requirements of cemented paste backfill in coal mine geothermal utilization. On the one hand, it proves the feasibility of fly ash cement-solidified marine clay for use as cemented paste backfill in coal mines; on the other hand, it also expands the available range of cemented paste backfill materials in coal mines.

Surface subsidence caused by coal mining has a great impact on the geological and ecological environments and causes damage to houses, roads, and industrial buildings. In order to understand the subsidence pattern in the mountainous mining regions, three mining faces of the Zhangjiamao mining area in the north of Shaanxi province, northwestern China are taken as case study. Firstly, the small baseline subset (SBAS) technology is used to process 12 images obtained in the mining area to investigate the subsidence data from December 2019 to April 2020. The boundary of surface deformation of the mining area interpreted by the SBAS-InSAR technology is inconsistent with the theoretical boundary suggested by coal mine subsidence theories. Especially, there are some areas in which the real subsidence are larger than estimated area. This discrepancy must be corrected as steep slopes near the theoretical boundary may increase the likelihood of landslides. Our research indicates that: (1) The accumulated displacement and the maximum deformation rate reached −120.759 mm and −270.012 mm/yr in the study area, and the subsidence boundary of the three mining faces is revealed; (2) the combination of the predicted boundary and slope stability analysis can effectively identify the landslide region at the edge of subsidence boundary; (3) the field surveys have proved the effectiveness of this method. The mining area subsidence revealed by our research helps to further understand the impact of land subsidence caused by mining in the mountainous areas and provides a practical method to predict subsidence boundaries and the likelihood for landslides.

In order to make a reasonable evaluation of the effect of backfill mining on non-coal mines, the first phase of the Laixin iron ore mine project is taken as an example. First, a geomechanical model of iron ore mining was established according to geological theory; second, numerical simulation software FLAC3D was used to analyze the surface subsidence, horizontal displacement, plastic failure range of the surrounding rocks, and stress conditions of the surface and surrounding rocks under unfilled and filled conditions; finally, the observation data of surface subsidence in the open area were analyzed against the background of the Phase I mining project of Laixin iron ore mine. The results show that: (1) the amount of surface subsidence increases with the increase of burial depth. As the mining depth increases, the amount of ground subsidence gradually increases. (2) Numerical simulation of the amount of surface subsidence and horizontal displacement in the unfilled condition is ten times that in the filled condition; the plastic zone of destruction in the unfilled condition extends to the surface, and the plastic destruction in the filled condition is mainly in the vicinity of the mining location, and the vertical stress in the unfilled condition is much larger than that in the filled condition; (3) the on-site measured results are basically consistent with the numerical simulation results, and the numerical simulation can be used to reasonably predict the amount of subsidence and horizontal displacement of the ground surface, and the force on the goaf.

In an environment, one of the natural geological hazards is land surface subsidence. Underground mining and subsurface coal fires are primarily responsible for subsidence of land. Activities, such as, over-exploitation of coal, minerals, groundwater and petroleum resources, depillaring of the existing galleries and water logging of the relinquished galleries are the major factors resulting in subsidence. The deformation is primarily measured in terms of change in ground elevation values (Z-dimension) at different time intervals at identified ground locations. All the conventional and exiting techniques have certain limitations in monitoring and predicting land surface subsidence. In this work, we predict the land subsidence in Jharia Coalfield, Dhanbad, India for one year in the interval of twelve days on the datasets collected through a monitoring technique called Modified PSInSAR. The sample datasets contains 14 locations and 67 previous land subsidence value calculated from each location. We train and test predictive models and perform the prediction of the land subsidence using Vanilla and Stacked long short-term memories. Finally, we demonstrate the predicted deformation values of the 14 locations for one year. The prediction model shows the subsidence rate in Nai-dunia basti near Jharia, Dhanbad is alarming as 93.8 mm/year where as Digwadih and Godhar showed the critical rate as 82 mm/year.

This work deals with modelling surface subsidence that aims to help industrialize Underground Coal Gasification (UCG). UCG is a long-known, but poorly industrialized method of energy extraction from coal. Risks of surface subsidence and groundwater pollution are two main hurdles that are affecting the potential industrialization of UCG. The particular challenge is the existence of groundwater because of implications to both its pollution and its influence on surface subsidence. Additionally, the coal combustion and the complex geometry of the UCG reactors impacts surface subsidence. To meet these challenges, the thermal and fluid analyses should be included in the model and surface subsidence should be modelled in three dimensions to capture the collapsed shape of the UCG reactor. Based on nature of these challenges and an earlier successful implementation, the commercial software FLAC3D by Itasca with the intrinsic thermal and fluid models is chosen to model surface subsidence. This study discovers that the inclusion of fluid analysis improves the predictions of surface subsidence when compared with measurements at the highly watered Shatsk UCG site. In turn, thermal analysis mildly influences the modelled surface subsidence. The fluid analysis shows that the flow in the upper aquifer influences surface subsidence more greatly than the flow in the lower aquifers. High temperature causes an upward flow in the lower aquifer located above the UCG reactor, but does not change the flow pattern in the upper aquifer. The fluid analysis also reveals that if the UCG reactor is filled with water, the surface subsidence does not occur.

Multi-temporal interferometric synthetic aperture radar (MT-InSAR) has been used to produce deformation velocity map for investigating the surface subsidence in the rapidly urbanizing metropolitan regions. However, simple analysis techniques like thresholding cannot detect and locate the widely distributed local-scale subsidence reliably. In this study, we propose a deep-learning based method to automatically detect the local-scale subsidence bowls in the deformation velocity map. To test our method, we choose the Guangdong-Hong Kong-Macao Greater Bay Area (GBA) as the study region, where widespread local-scale subsidence bowls exist associated with the urbanization. Using deformation velocity maps spanning 2015–2017 derived from MT-InSAR, our method detects several subsidence bowls due to dewatering, excavation of foundation pits and subways, and other engineering works. The results demonstrate the potential applicability of the proposed method to automatically detect and analyze the local-scale subsidence bowls in the built-up regions.

The coal mining technology of fully mechanized solid filling is an efficient and green mining method that integrates “sediment reduction” and “emission reduction.” However, the discharge of wasted gangue and surface subsidence are controlled by the amount of wasted gangue used in filling mining and the compaction rate of gangue filled into a goaf, respectively. To increase the consumption of wasted gangue and reduce surface subsidence, mixed gangue composed of equal-quality washed gangue and crushed gangue is proposed as a raw material for solid filling on the basis of gradation theory. Next, a screening experiment was performed to analyze the grain gradation of different specimens, and a compression experiment was executed to compare and analyze the compression characteristics. The results show that the nonuniformity coefficient of mixed gangue is 55.2 and the curvature coefficient is 1.53, which significantly improve the grain gradation of washed gangue. The degree of relative compaction of mixed gangue is 1.226, which is significantly lower than that of washed gangue, which is 1.33. The deformation modulus of mixed gangue is 23–135 MPa, which is better than that of washed gangue (26–100 MPa), indicating that the compressive resistance of mixed gangue is significantly improved. The case study of the Tangkou mine suggests that mixed gangue greatly promotes the consumption of wasted gangue and can effectively control the surface deformation.

Differential interferometry of synthetic aperture radar (DInSAR) can be used to generate high-precision surface displacement maps in continuous permafrost environments, capturing isotropic surface subsidence and uplift associated with the seasonal freeze and thaw cycle. We generated seasonal displacement maps using DInSAR with ultrafine-beam Radarsat-2 data for the summers of 2013, 2015, and 2019 at Cape Bounty, Melville Island, and examined them in combination with a land-cover classification, meteorological data, topographic data, optical satellite imagery, and in situ measures of soil moisture, soil temperature, and depth to the frost table. Over the three years studied, displacement magnitudes (estimated uncertainty ± 1 cm) of up to 10 cm per 48-day DInSAR stack were detected. However, generally, the displacement was far smaller (up to 4 cm). Surface displacement was found to be most extensive and of the greatest magnitude in low-lying, wet, and steeply sloping areas. The few areas where large vertical displacements (&gt, 2.5 cm) were detected in multiple years were clustered in wet, low lying areas, on steep slopes or ridges, or close to the coast. DInSAR also captured the expansion of two medium-sized retrogressive thaw slumps (RTS), exhibiting widespread negative surface change in the slump floor.

In addition to spaceborne Interferometric Synthetic Aperture Radar (InSAR), airborne data such as those obtained by the Uninhabited Aerial Vehicle Synthetic Aperture Radar (UAVSAR) have also been utilized to measure surface subsidence in permafrost areas in recent years. Motivated by the integration of multiplatform InSAR data, we generated two UAVSAR interferograms and one Advanced Land Observing Satellite (ALOS)‐2 L‐band interferogram over a permafrost area near Yellowknife, Canada, then compared the surface subsidence in the thaw seasons of 2017. The correlation coefficient and the root mean square error (RMSE) of subsidence difference are calculated to compare the airborne and spaceborne InSAR measurements. The results demonstrate that the two UAVSAR measurements are self‐consistent, with the correlation coefficient between independent airborne measurements ∼0.7. While the RMSE of the difference between surface subsidence measured by UAVSAR and ALOS2 is ∼2.0 cm, and the correlation coefficients are less than 0.41, that is, a noticeable deviation exists between the UAVSAR and ALOS2 results possibly due to different spatial resolution and the calibration processing of airborne and spaceborne InSAR data. In addition, both UAVSAR and ALOS2 interferograms show larger surface subsidence within taiga needleleaf forest regions than in regions of other biome types (including needleleaf forest, shrubland, and grassland). The results demonstrate that a scheme for the elimination of systematic differences needs to be developed before merging multisource InSAR results. This intercomparison will provide valuable insights for narrowing the gap between radar‐based measurements and planning the integration of airborne and satellite InSAR measurements in permafrost environments., Key Points We compare the seasonal subsidence derived from airborne and satellite InSAR measurementsTwo UAVSAR interferograms are self‐consistent while a significant deviation exists between the UAVSAR and ALOS2 resultsWe discuss the difference and the potential combination use of spaceborne and airborne InSAR to improve subsidence measurements over permafrost regions

Based on Platts theory of ground pressure, the traditional formation stress distribution method was improved, and a stress model was constructed by the ring distribution. Then, the equilibrium equation of force was obtained considering the confining pressure. Based on that, the relationship between the limit equilibrium height of the pressure arch and the parameters of the tunnel was revealed. Then, the calculation model of the limit equilibrium height of the pressure arch was established considering the circumferential action of the rock mass in the shallow-buried tunnels. Via the finite differential method, a three-dimensional calculation model of the shallow-buried tunnels under V-level surrounding rock geological conditions was established, and tunnel excavation was simulated. Based on the results of the numerical simulation, the relation curve between the maximum principal stress and the tunnel depth was obtained, and then the limit equilibrium height of the pressure arch was determined. In addition, the error between the numerical simulation results and the theoretical calculation results was analyzed to verify the accuracy of the calculation formula, which proved the accuracy of the calculating model. Finally, the calculation model was applied to calculate the limit equilibrium height of the pressure arch of the Qianyu tunnel, which is an important section of the Lunan Highway in Shandong Province. According to the results, we found that the burial depth of the Qianyu tunnel was less than the minimum burial depth of the forming pressure arch, which was the essential reason for the collapse and surface subsidence during tunnel excavation. Therefore, the improved calculation model of the pressure arch height can be further used to calculate the limit equilibrium height of the pressure arch in shallow-buried tunnels.

The microtopographic changes induced by coal mining subsidence caused a series of environmental problems such as soil erosion, and vegetation degradation in the mining area. However, the corresponding influence on surface vegetation and soil characteristic in different parts of the slope was completely different. To understand soil and vegetation degradation in coal mines and their future ecological restoration, it was crucial to investigate the origin. The relationship between soil microbial community diversity, structure, and taxa in the slope of subsidence area of different topographic locations in Daliuta coal mine, Shannxi, China, was determined by high throughput sequencing and molecular ecological network analysis. The relationship between the bacterial communities, environmental factors, and soil physicochemical properties was also investigated. We found a new topographic trait formed by surface subsidence to deteriorate the living environment of vegetation and the bacterial community from top to the bottom of the subsidence slope. The available potassium and available nitrogen in the soil decreased. The vegetation coverage, soil water content, organic matter, and urease and dehydrogenase activities decreased significantly (p < 0.05). Although soil bacterial community diversity in the subsidence area did not differ significantly, the dominant taxa in different topographic locations varied. The molecular ecological networks representing bacterial community structure and function were also totally different and were fewer at the middle and the top of the slope than at the bottom of the slope. The network approached complication, and the network connection and interconnection increased dramatically. However, the network in the bottom slope approached simplicity, and weak interaction, predominantly cooperative, was observed within and between modules. Meanwhile, the double stress of aridity and the lack of carbon source induced by subsidence also enhanced the capacity of the soil bacterial community to metabolize complex carbon sources at the bottom of the slope.

Precipitation directly affects the redistribution of surface mass, causing the elastic deformation of the solid earth, and the crustal deformation caused by this surface load can directly respond to the vertical displacement of the GNSS reference station. Based on the vertical displacement data of 2011 to 2015 and the corresponding daily precipitation data of four China's tectonic environmental monitoring network (land state network) sites in Beijing, this paper completed the analysis of the spatio-temporal correlation characteristics of the two factors. The result demonstrates that the vertical displacement of GNSS reference station is closely related to the corresponding precipitation of the site. Through the analysis of experimental/testing data, it shows that (1) there is a lag period of about 6 months, and (2) the positive and negative correlations of rainfall on surface subsidence is not fixed, and (3) mathematics model can predict the vertical component changes in some extent.

The subsidence caused on the surface due to the construction of subsurface tunnels for various purposes in urban areas is a major concern for both the tunnel and the overlaid buildings. Seeing the importance of study, different models has been created keeping reference of commercial and residential buildings. The amount of surface deformation and the stresses so generated are calculated, which plays a paramount role before construction. These models are analyzed on circular and semicircular tunnels with various loading conditions and varying litho. In this paper, two software’s namely STAAD Pro and Rocscience were used for structural design and analysis respectively. The study gives the basic idea of behavior of these two shapes of tunnels with varying loading condition and strata which shows a path for predicting unforeseeable displacements in real life situations.

Surface subsidence and its secondary effects caused by underground coal mining continually threaten the safety and property of residents in mining areas. The commonly used total station and leveling approach is time-consuming and laborious, and the spatial range is limited. In this study, an FEIMA D2000 quadrotor unmanned aerial vehicle (UAV) was used to conduct 4-cm / pixel photogrammetry in four trial periods over a surface influence area (3.75 km2) of a working mine face. The performance comparison experiments from five point-cloud filtering algorithms in two sub-regions of the study area show that the ATIN algorithm provides the best filtering for this study area. Coal mining subsidence monitoring in mountainous area based on time-series UAV photogrammetry technology is proposed. Using this approach, the ATIN algorithm was used to filter the overall point cloud data in the study area to obtain the digital elevation model (DEM). The surface dynamic subsidence basin was determined with two phases of DEM subtraction. The results show that, compared with the measured leveling data in the field in the same period, the average root mean square error is 165 mm, and the maximum subsidence monitoring accuracy reaches 98%.

Shallow coal seam with thick soil layer is widely reserved in the Jurassic Coalfield, Western China, mining-induced subsidence represents complex characteristics. Combining with physical simulation, theoretical analysis and in-situ observation, the overburden strata structure in dip direction were revealed, and the subsidence prediction models were established, based on this, the subsidence equations of overburden strata and ground surface were proposed. The results show that after shallow coal seam mining, based on the subsidence and movement characteristics, the overburden strata structure can be divided into three zones, which are "boundary pillar F-shape zone" (BPZ), "trapezoid goaf zone" (TGZ) and "coal pillar inverted trapezoidal zone" (CPZ). The subsidence of overburden strata depends on the key stratum, while the subsidence of soil layer depends on the bedrock subsidence basin, which is between the bedrock and thick soil layer. The bedrock subsidence is mainly related to mining height and bulking coefficient in TGZ, while it is mainly affected by mining height and distribution load on the key stratum in BPZ and CPZ. According to physical simulation and theoretical model, the maximum surface subsidence of No.1–2 seam mining in Ningtiaota coal mine are 1.1m and 1.07m respectively, which is basically consistence with the result of in-situ observation (1.2m).

This paper describes a case study of surface subsidence in the Hongling Lead-Zinc Mine. Hongling Lead-Zinc Mine is located in Inner Mongolia, China, about 240 km away from the border between China and Mongolia. There is a batch of outcrops of the near-surface thick steep-dip metamorphic orebody. The large-scale surface subsidence induced by underground excavation has brought some impact on the safety of herdsmen and their daily husbandry activities nearby. The requirements of reclamation for subsidence areas in the relevant laws and regulations, raise enormous pressure and risk on safe and economic operation. In this paper, a 3D numerical model of this mine was built by 3DMine and FLAC3D to analyse the excavation procedure and mechanism. The results of the simulation were in good agreement with the field subsidence data collected by satellites and unmanned aerial vehicles from 2009 to 2019. The analysis showed that the current mining method—an integrated underground method of stoping and caving—accelerated the surface subsidence, and some measures of monitoring, controlling and management were expected to take in order to improve economic and ecological benefits.

In order to solve the current two major environmental problems of urban waste pollution and surface subsidence above the coal mine goaf, the technology of sealing and backfilling the goaf with urban waste is proposed. This technology takes "waste disposal" and "goaf backfilling" as the design theme, and uses waste screening, processing, transportation, and backfilling as the design links. Aiming at the processing of loose waste, the waste drying and briquetting integrated machine is designed, which comprehensively utilizes the methods of waste physical disposal and heat disposal to dehydrate and press the waste into a block with a particle size of 150mm, and finally pass the six-sided winding package. The entire processing technology ensures the strength of the waste materials and no filtrate. For the processing of solid aggregate waste, it is crushed into recycled concrete raw materials for goaf backfilling. Aiming at the goaf backfilling, the goaf backfilling coal mining method is designed, the backfilling hydraulic support is modified, and the backfilling mechanism is added to realize the integration of “mining-backfilling” in the working face. The backfilling technology embodies the key issues of the sealing of the backfilling space and the strength of the backfilling body with third times of sealing strengthening. Using urban waste as the backfilling materials for the goal area, the waste pollution and the surface subsidence are turned into “two benefits”, and the construction of waste-free cities and green mines is promoted.

We use Ice, Cloud, and land Elevation Satellite 2 (ICESat‐2) laser altimetry crossovers and repeat tracks collected over the North Slope of Alaska to estimate ground surface‐height change due to the seasonal freezing and thawing of the active layer. We compare these measurements to a time series of surface deformation from Sentinel‐1 interferometric synthetic aperture radar (InSAR) and demonstrate agreement between these independent observations of surface deformation at broad spatial scales. We observe a relationship between ICESat‐2‐derived surface subsidence/uplift and changes in normalized accumulated degree days, which is consistent with the thermodynamically driven seasonal freezing and thawing of the active layer. Integrating ICESat‐2 crossover estimates of surface‐height change yields an annual time series of surface‐height change that is sensitive to changes in snow cover during spring and thawing of the active layer throughout spring and summer. Furthermore, this time series exhibits temporal correlation with independent reanalysis datasets of temperature and snow cover, as well as an InSAR‐derived time series. ICESat‐2‐derived surface‐height change estimates can be significantly affected by short length‐scale topographic gradients and changes in snow cover and snow depth. We discuss optimal strategies of post‐processing ICESat‐2 data for permafrost applications, as well as the future potential of joint ICESat‐2 and InSAR investigations of permafrost surface‐dynamics., Key Points ICESat‐2 altimetry can resolve surface subsidence that is related to changes in snow‐cover depth and seasonal thawing of the active layerICESat‐2 measurements of surface‐height change are affected by along‐track topographic gradients and complex surface roughnessComplementary ICESat‐2 and InSAR datasets can be jointly leveraged for future studies in periglacial environments

Gradual instability of coal pillars left behind underground with room mining is one of the main reasons for sudden roof caving in the gob, surface subsidence, and other significant hazards. Moreover, room mining implies great losses of coal resources. In this paper, the main failure mode and room mining coal pillar process were analyzed according to the coalfield regional engineering geological and hydrogeological conditions. A numerical model was adopted to study the effect of different sizes of coal mining pillars and progressive instability failure of coal pillar on the plastic zone’s evolution characteristics and stress field of coal pillars in the stope. The proposed technologies of cemented paste backfilling and reinforcement of residual coal pillars are applied, and a numerical simulation model is established to study the strata movement characteristics and analyze the stability degree of residual coal pillar and key aquiclude strata in the Pliocene series of Neogene. Consequently, the performance and application prospect were evaluated. The results obtained substantiate a new method for the long-term stability control of coal pillars in room mining and protecting the ecological environment in China’s western eco-environmental frangible area.

Underground coal fires have become a worldwide disaster, which brings serious environmental pollution and massive energy waste. Xinjiang is one of the regions that is seriously affected by the underground coal fires. After years of extinguishing, the underground coal fire areas in Xinjiang have not been significantly reduced yet. To extinguish underground coal fires, it is critical to identify and monitor them. Recently, remote sensing technologies have been showing great potential in coal fires’ identification and monitoring. The thermal infrared technology is usually used to detect thermal anomalies in coal fire areas, and the Differential Synthetic Aperture Radar Interferometry (DInSAR) technology for the detection of coal fires related to ground subsidence. However, non-coal fire thermal anomalies caused by ground objects with low specific heat capacity, and surface subsidence caused by mining and crustal activities have seriously affected the detection accuracy of coal fire areas. To improve coal fires’ detection accuracy by using remote sensing technologies, this study firstly obtains temperature, normalized difference vegetation index (NDVI), and subsidence information based on Landsat8 and Sentinel-1 data, respectively. Then, a multi-source information strength and weakness constraint method (SWCM) is proposed for coal fire identification and analysis. The results show that the proposed SWCM has the highest coal fire identification accuracy among the employed methods. Moreover, it can significantly reduce the commission and omission error caused by non-coal fire-related thermal anomalies and subsidence. Specifically, the commission error is reduced by 70.4% on average, and the omission error is reduced by 30.6%. Based on the results, the spatio-temporal change characteristics of the coal fire areas have been obtained. In addition, it is found that there is a significant negative correlation between the time-series temperature and the subsidence rate of the coal fire areas (R2 reaches 0.82), which indicates the feasibility of using both temperature and subsidence to identify and monitor underground coal fires.

Strip mining in mines is one of the main mining methods to control surface subsidence and protect the ecological environment. In recent years, strip mining has induced frequent rock burst accidents due to the increase in mining intensity and mining depth. Based on two typical deep strip mining accidents, the characteristics of the changes in spatial structure of the overlying strata caused by strip mining are studied, and the influencing factors of the occurrence of strip mining rock burst are analyzed. A support pressure calculation model is proposed, and estimated and verified in a mine after an analysis of the change law of the overlying strata structure in strip mining and research on the distribution and evolution law of support pressure. Based the above research, a risk evaluation model of the strip mining face is proposed based on the possibility index method, the 4203 working face of a mine is evaluated. Compared with the numerical simulation results, this method is well consistent with the theoretical calculation model. It can be seen that this method has strong practicability and is of great significance for studying the rock burst characteristics of coal seams in strip mining and evaluating the risk of rock burst of coal seams.

The research on the key factors of surface subsidence in paste backfilling mining of thick coal seam in deep mine is a complex system engineering, which involves mining, backfilling, support, subsidence, safety, and other aspects. At present, there is no systematic research on the key factors of surface subsidence in paste backfilling mining of thick coal seam more than 6 meters in a deep mine. In this paper, field research, laboratory experiments, theoretical analysis, and other research methods are used to carry out the research about 3# coal seam under buildings in the Lu’an area. The main conclusions are as follows: through the construction of the fuzzy extension model of surface subsidence in paste backfilling mining, five types of surface subsidence are obtained, including overburden structure, roof subsidence before backfilling, nonbackfilling account, the strength of filling body, and backfilling technology. It is the key factor to control the surface subsidence; the optimization measures are given to provide a reference for the reasonable design of paste backfilling mining in other working faces. The research conclusion has a certain reference value for solving a series of problems such as coal resources under buildings, solid waste disposal, controlling strata and surface movement, improving the recovery rate of mine resources, and extending the service life of mine.

The growth of market requirements for socio-economic and environmental parameters of coal resources in most developed (“old”) mining areas (MA) of Ukraine has led to the closure of mines and quarries, including by the method of “wet conservation”. This process is most actively developing in the MA of Donbas, including in areas affected by armed conflict. In most developed EU countries, the decommissioning of coal mines, which have large depths and area of minefields, is a research and production complex of post-mining (PM), which is based on scientific and technical measures to prevent dangerous changes in the geological environment (GE)—subsidence of the earth’s surface, flooding of lands, release and surface outgassing of explosive and toxic gases, limiting the leakage of polluted water. In general, the set of PM measures is aimed at maintaining the balance and protective potential of the GE as a mineral and landscape base of the biosphere. In this regard, the article compares the protective potential of the GE of the Chernobyl accident zone and the Donbas region, as well as performs an expert assessment of the environmental protection potential of the PM in the leading coal MA of Ukraine. It is shown that a new model of mineral resources use, structure of geological exploration works, scientific substantiation of maximum allowable changes of GE at the closing of “old” and formation of new MA, improvement of environmental monitoring based on GIS technologies and remote sensing of the Earth is needed.

Cemented coal gangue paste backfill (CCGPB) containing coal gangue and fly ash is a backfilling technique newly developed in coal mines in China that allows environmentally hazardous products, such as gangue and fly ash, to be reused in underground stopes. CCGPB materials provide efficient ground support for the caving of strata and reduce surface subsidence. In this paper, field monitoring of CCGPB properties was conducted in an underground coal mine, which mainly included the measurement of the longwall face temperature, humidity, CCGPB internal hydration temperature, stress conditions inside the backfills, and displacement. First, the components of the backfills, paste technique, slurry generation procedures, coalfield geology, and mining conditions were introduced. Then, a monitoring system was designed in the field. An online monitoring system was installed. The results of the field monitoring showed that the curing temperature significantly varied, i.e., from 26°C near the main gate to 37°C near the tailgate. The curing humidity had the same trends, increasing from 60% relative humidity (RH) near the main gate to 81% RH near the tailgate. The internal hydration process of the paste was divided into four stages, i.e., the rapid hydration stage, slower hydration stage, rapid decline hydration stage, and relatively stable stage. The highest hydration temperature was 50°C, which was measured on the second day after the backfill process. The temperature approached stability at 41°C. The evolution of the roof stress applied on the CCGPB was divided into four stages: the development stage, regulation stage, rapid growth stage, and relatively stable stage. The maximum roof loading was 12 MPa in the middle of the longwall face. The deformation of the backfill experienced four stages, i.e., the rapid deformation stage, slow deformation stage, relatively stable stage, and long-term stable stage. The maximum deformation was 104.3 mm, appearing in the middle of the face. In addition, the compression ratio of the backfill was approximately 4%. The results of this study showed that the working conditions of backfills in the field were different from those in the laboratory. This paper provides guidance for the design of the CCGPB technique and the predictions of surface subsidence induced by the production process of underground mining.

In the process of coal mining, when the buried depth is large and the loose layer is thick, the ground subsidence tends to be abnormal, thus causing great damage to the surface ecological environment. In order to reveal the mechanism of mining ground subsidence under ultrathick loose layer, taking 1305 working face of a mine as the background, the law of mining ground subsidence under ultrathick loose layer was analyzed through field measurement. The law of bedrock subsidence is analyzed by similar simulation test, and the role of ultrathick loose layer in bedrock subsidence is quantitatively analyzed. The hydrophobic settlement model of ultrathick loose layer is established by settlement theory calculation, and the law of ground subsidence caused by hydrophobic of ultrathick loose layer is analyzed. The results show that the ground subsidence is mainly composed of bedrock subsidence and hydrophobic settlement of ultrathick loose layer. The maximum ground subsidence measured in the field is 4.201 m, the bedrock surface subsidence obtained by the simulation test of similar materials is 3.552 m, and the subsidence of ultrathick loose layer obtained by hydrophobic settlement analysis is 0.58 m. Adding the subsidence of bedrock surface and the subsidence of ultrathick loose layer, the ground subsidence is 4.132 m. It is in good agreement with the total ground subsidence measured in the field, which verifies the rationality that the ground subsidence mainly includes bedrock subsidence and hydrophobic settlement of ultrathick loose layer.

In modern life, metro and high-speed rails have become indispensable transportation and have been playing an important role in many areas, especially in cities. The metro and high-speed rails have varying degrees of impact on the surface and surrounding buildings, which must be carefully understood to minimize the risk of hazards. This work is aimed at investigating the deformation of ground surface and the surrounding structures, caused by the excavation of underground tunnels. Because of the spatiotemporal characteristics of the land subsidence induced by underground tunnel construction, the measurements obtained from InSAR (Synthetic Aperture Radar Interferometry) and leveling techniques are integrated to study the subsidence phenomenon of the ground surface above the shield tunnels and the surrounding buildings. The subsidence-related parameters, including the advance angles, lag angles, and boundary angles, are derived from the deformation results. This study suggests that leveling and InSAR observations can provide technical support to study the subsidence of dense buildings on the surface of shield tunnel excavation and to protect the surrounding environment.

International audience; From 1910 to 2002, the Mines Domaniales de Potasse d'Alsace (MDPA) exploited two potash layers, located at depths greater than 400 m in the southern Upper Rhine Graben. This mining activity has caused surface subsidence, investigated here using SAR interferometry (InSAR) and Persistent Scatterer Interferometry (PSI) approach is used to follow mining induced surface displacements over the Alsatian potassic basin. The SAR images acquired by three distinct satellites (ERS, ENVISAT, Sentinel-1) over the last 24 years cover both mining and post-mining periods. Until 1996/1997, InSAR results do not fit the high vertical displacement deduced from levelling campaigns due to unwrapping errors and are therefore not reliable to quantify the mining subsidence. From 1996/1997, InSAR results and levelling measurements become consistent, allowing us to study the subsidence following the activity of the mine. The surface subsidence decreases quickly after the end of mining operations, with current subsidence estimated below 5 mm/yr in 2018. The InSAR results obtained for the postmining period show a correlation between residual subsidence amplitude and the mined thickness. Taking together the InSAR and levelling measurements for the whole 24 years period, the combined time series are approximated by a sum of two exponential terms, which reveals the role of the goaf compaction at depth. The study shows that SAR interferometry is well suited for monitoring small amplitude mining-induced subsidence over the residual phase, helping to better mitigate the related risk in these regions.

In order to deal with solid wastes and protect the fragile ecological environment on the ground, using gangues as the filling materials in the underground goaf can not only achieve favorable waste disposal but also alleviate surface subsidence and protect surface buildings and the ecological environment, with great practical significance and application prospects. During the water seepage process, the evolution rules of inner seepage channels in the bulk filling materials are the theoretical foundation for the realization of water-preserved mining. In order to gain clear knowledge of the seepage characteristics of the bulk filling gangues with different sizes, the evolution rules of some seepage parameters mainly including the displacement, the porosity, and the permeability of gangues and hydraulic pressure were analyzed via COMSOL numerical simulation. The evolution rules of the seepage characteristics of the bulk filling materials with different sizes were revealed by combining the present experimental and numerical results. Moreover, the present seepage experiment was proved to be reliable by comparing with numerical simulation results. This work can provide theoretical foundation for investigating the evolution characteristics of inner seepage paths in the bulk filling materials and selecting appropriate bulk filling materials under different stress and seepage environments.

In mining engineering, after the extraction of underground resources, the maximum surface subsidence is usually less than the mining thickness of coal seam. However, under the condition of thick loose layer, some special phenomena appear in surface subsidence, for example, the maximum surface subsidence value is greater than the mining thickness of coal seam. This special phenomenon cannot be predicted by traditional subsidence prediction methods. To solve this problem, by using the numerical simulation software Fast Lagrangian analysis of continua (Flac), we study the changing rules of subsidence with different strata lithology and unconsolidated layer thickness and reveal the formation mechanism of this law. The results show that the effect of the thick unconsolidated layer on the hard rock is greater than that of the soft rock. When the rock is soft, the unconsolidated layer moves as a whole following the bedrock during the whole mining process. The surface subsidence decreases approximately linearly with the thickness ratio increase of the unconsolidated layer to bedrock. However, when the rock is hard or medium hard, there are supporting structures formed inside the rock stratum, which has supporting effect on the overlying strata. The surface subsidence undergoes three proportional sections, first increases, then decreases, and finally increases with the thickness ratio increase of the unconsolidated layer to bedrock. Combined with these laws, based on the theory that the rock strata space can be completely compressed gradually, we derive the calculation method of surface subsidence under the condition of thick unconsolidated layer and apply it to practice. The results show that the prediction results are consistent with the actual situation and meet the engineering requirements. The research results can provide a reference for the subsidence prediction of similar conditions.

In the process of urban rail transit construction, underground excavation method is often used in subway station construction. Based on a large number of measured data of Qingdao Metro Line 3, this paper analyzes and studies the ground subsidence law of long-span shallow buried excavation station. The research results show that vertical surface settlement will be caused by the excavation of both sides of the guide hole, but the settlement is relatively small, basically within −10 mm. Large surface settlement will occur during the middle or middle guide hole excavation, with a large settlement up to −30 mm. Through data fitting, it is found that the regression analysis using cubic polynomial of one degree can get better fitting effect. The horizontal surface variation rules of underground excavation stations are affected by the tunnel depth, geological conditions, management level of monitoring units, monitoring layout and monitoring accuracy, and so on. The differences in horizontal surface deformation and settlement between stations are large. Wannianquan Road Station basically conforms to the deformation law of ground settlement trough in Peck, and Junfeng Road Station directly above belongs to the whole subsidence type. This study has accumulated a large number of surface settlement monitoring data, which can provide a certain reference for the subsequent design of similar lines.

Summary The mechanical influence of pore fluids on rock behaviour has important implications for sandstones which are increasingly targeted for extraction and storage of sustainable energy resources to support decarbonisation. Changes in pore fluid pressure arising from these activities may lead to surface subsidence, induced seismicity, fault initiation or promotion of fault slip, hence the need for prediction of rock behaviour in the presence of pore fluids. Here, we investigate the stress path evolution of porous (25%) Hollington sandstone under conditions simulating fluid injection and depletion. Yield is defined by an elliptical cap that is consistent with most porous sandstones, but with a near vertical high mean stress side. Post-yield compaction under undrained conditions raises pore pressure, thereby deflecting the stress path towards lower effective mean stresses, eventually tracking the yield surface until critical state is attained. Progressive increments of pore pressure can lead to faulting and unloading of the rock by slip along the generated fault, while progressive reduction of pore pressure deflects the stress path towards purely compactant deformation, which can exacerbate pore collapse and thus promote subsidence. The results highlight the importance of fluid volume and rate management during deep subsurface injection or depletion.

Summary A sustainable energy transition requires societal acceptance. In turn, social acceptance is built on trust. Trust, that geoscientists and engineers are well-educated, but more importantly willing to detect short-, mid- and long-term risks in the first place, at the right point in time - ideally the planning phase. Beyond the detection, it furthermore requires the ability and willingness to speak up, finally followed by taking appropriate actions. Within the context of the reassessment of the structural integrity of the againg salt cavern storage facility Etzel (Lower Saxony basin / Germany), the author discusses the geoethical obligations of staff involved, the main salt cavern subsurface risks as well as the required geotechnical skills. Preliminary results conspicuously show a high potential of a major incidents due to quickly converging caverns (THE CAUSE), seriously elevated surface subsidence (THE EFFECT) … and in between the critically stressed, probably hydraulically conductive main fault, subject to a potential fault reactivation.

The fragile habitat of alpine mining areas can be greatly affected by surface disturbances caused by mining activities, particularly open-pit mining activities, which greatly affect the periglacial environment. SBAS-InSAR technology enables the processing of SAR images to obtain highly accurate surface deformation information. This paper applied SBAS-InSAR technology to obtain three years of surface subsidence information based on the 89-scene Sentinel-1A SLC products, covering a mining area (tailings and active areas) in the Tianshan Mountains and its surroundings from 25th December 2017 to 2nd January 2021. The data were adopted to analyze the characteristics of deformation in the study region and the mining areas, and the subsidence accumulation was compared with field GNSS observation results to verify its accuracy. The results showed that the study area settled significantly, with a maximum settlement rate of −44.80 mm/a and a maximum uplift rate of 28.04 mm/a. The maximum settlement and accumulation of the whole study area over the three-year period were −129.39 mm and 60.49 mm, respectively. The mining area had a settlement value of over 80 mm over the three years. Significantly, the settlement rates of the tailings and active areas were −35 mm/a and −40 mm/a, respectively. Debris accumulation in the eastern portion of the tailings and active areas near the mountain was serious, with accumulation rates of 25 mm/a and 20 mm/a, respectively, and both had accumulation amounts of around 70 mm. For mine tailing pile areas with river flows, the pile locations and environmental restoration should be appropriately adjusted at a later stage. For gravel pile areas, regular cleaning should be carried out, especially around the mining site and at the tunnel entrances and exits, and long-term deformation monitoring of these areas should be carried out to ensure safe operation of the mining site. The SBAS-InSAR measurements were able to yield deformations with high accuracies over a wide area and cost less human and financial resources than the GNSS measurement method. Furthermore, the measurement results were more macroscopic, with great application value for surface subsidence monitoring in alpine areas.

To solve the problems of surface deformation and destruction of buildings caused by urban mining and realise the coordinated development of mining cities, the solid backfilling method was used to extract coal resources beneath the buildings of Tangshan. Based on surface deformation monitoring data of the continuously operating reference station (CORS) system for the past 5 years, the surface deformation process caused by solid backfilling was analysed. The final results revealed a maximum surface subsidence of 66 mm in the T zone coal area and 31 mm in the F zone area. Furthermore, the surface control effects of the caving method and the solid backfilling method were compared and analysed, and it was shown that solid backfilling could meet the surface building setup requirements. Moreover, based on the probability integral method, the effects on surface deformation due to the surface length of the F zone, compression ratio, and coal pillar width were analysed, and the effects on the prediction results due to the subsidence factor, tangent of the major effective angle, and offset distance of the inflection point were studied. The results showed that the compression ratio is the main factor controlling the surface deformation and that it should be kept above 80% for solid backfilling of urban mines. The subsidence factor should be 0.82, and the tangent of the major effective angle should be 2.15 when the surface subsidence of solid backfilling is to be predicted. This paper provides a technical reference for the realisation of urban mining with solid backfilling.

Mining-induced subsidence is a great concern for environmental protection in underground mining areas in China and all over the world. In view of the fact that the research on land degradation above underground coal mines are completely or partially independent of coal mining activity and the fact that the mechanism behind mining-induced subsidence has not been well understood, this study presents a field measurement and numerical study of mining-induced subsidence with respect to mining activity of three adjacent longwall panels in a coal mine in Northwest China. This study shows that surface subsidence lags far behind panel extraction or mining activity. The profiles of ground surface are dominated and manifested by the subsurface strata structures. The subsidence influence throughout the whole length of a longwall panel varies. Stability of strata structures within overburden before the final subsidence controls the stability of ground surface land. Chain pillars of 20 m between panels of 240 m wide with cover depth of 600 m have been crushed in the gob and do not have any function in supporting the overburden strata. The final subsidence of the three adjacent panels is far to come in the future and the land reuse above underground coal mines should be carefully planned by making sure that the gob is completely compacted or no potential secondary subsidence occurs in the future.

The aim of this study is to obtain movement laws of overlying strata above a fully mechanized coal mining face backfilled with gangue and solve the problem of surface subsidence during coal mining. This study was carried out based on gangue backfilling mining of Jiulishan Coal Mine (Jiaozuo City, Henan Province, China) from the perspectives of deformation of backfilled gangue under compaction, surrounding rock of a stope, and activities of key strata. The method combining with rock mechanics, viscoelastic mechanics, control theory of rock mass under mining, and numerical simulation was used based on physical and mechanical characteristics of backfilled gangue. On this basis, the research analyzed the temporal-spatial relationships of activities of surrounding rock of the stope, compressive deformation of backfilling body, failure depth of the floor, deformation characteristics of the main roof with laws of surface subsidence. The movement characteristics of overlying strata above the fully mechanized coal mining face backfilled with gangue and the traditional fully mechanized mining face were compared. It is found that, under the same conditions of overlying strata, movement laws of overlying strata are mainly determined by the mining height of coal seams and the heights of a caving zone and a fracture zone are nearly linearly correlated with the mining height. Through analysis based on thin-plate theory and key stratum theory, the location of the main roof of the fully mechanized coal mining face backfilled with gangue in coal seams first bending and sinking due to load of overlying strata was ascertained. Then, it was determined that there are two key strata and the main roof belongs to the inferior key stratum. By using the established mechanical model for the main roof of the fully mechanized coal mining face backfilled with gangue and the calculation formula for the maximum deflection of the main roof, this research presented the conditions for breaking of the main roof. In addition, based on the theoretical analysis, it is concluded that the main roof of the fully mechanized coal mining face backfilled with gangue does not break, but bends. The numerical simulation results demonstrate that, with the continuous increase of strength of backfilled gangue, the stress concentration degree of surrounding rock reduces constantly, so does its decrease amplitude. Moreover, the compressive deformation of backfilling, failure depth of the floor, and bending and subsidence of the main roof continuously decrease and tend to be stable. The mechanical properties of backfilling materials determine effects of gangue backfilling in controlling surface subsidence. Gangue backfilling can effectively control movement of overlying strata and surface subsidence tends to be stable with the increase of elastic modulus of gangue.