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Mining protective coal seams is an effective approach for coal and gas outburst control, but a large amount of gangue is usually produced when mining a thin protective seam and dealing with the gangue can be a challenging task. In the paper, a novel integrated mining system by extracting two panels simultaneously was demonstrated in the 12th coal mine of the Pingdingshan coalfield: one panel was mined in the thin protective coal seam, and the other one was mined in the protected coal seam. The thickness of the protective seam was only 0.8 m, but the mining height reached 1.8 m, indicating that there was about 1 m thick roof stone being mined. An underground coal preparation plant was built, and the mixture of coal and gangue from the protective panel was sorted underground. The sorted coal was delivered to the surface stockpile, while the waste rock was directly backfilled into the gob of the panel in the protected coal seam. Thus, waste rock did not need to be lifted up to the surface, which can reduce material handing cost and minimise mining footprint on the surface. In order to prevent the migration of pressure relief gas into the working areas of the protective coal seam, the main reasons causing gas exceedance in the upper corner of U-shaped ventilation system were investigated, and then the Y-shaped ventilation system and various gas extraction boreholes were implemented to effectively control the pressure relief gas. Numerical models were developed to assess the effect of applying gob backfilling during the extraction of two panels in parallel. The results show that the gob backfilling can reduce the surface subsidence and horizontal movement, which is very helpful for the protection of ground water and surface infrastructures.

Statistically homogeneous pixel (SHP) selection and DS phase optimization are two critical steps in the distributed scatterer interferometric SAR (DS-InSAR) time series method. In this paper, a new...

Underestimation of customized shortwall mining parameters of deep extra-thick coal seams (namely, mining height, mining width, and pillar width) may result in coal pillar instability, surface subsidence, and mining structure failure, while their overestimation would cause a waste of coal resources. This study proposes a new method for optimizing these parameters, whose main purpose is to achieve the maximum coal recovery rate while satisfying surface deformation and coal pillar stability requirements. A case study of an extra-thick coal seam in Eastern China with one km-overburden depth and a thickness of 10 m was analyzed. First, a new method for predicting surface deformation under deep customized shortwall mining based on surface deformation data from fully caving mining was proposed. The variation pattern of the extreme values of surface deformation parameters (including surface subsidence, tilt, curvature, and horizontal strain) versus the area-based recovery rate and mining width was analyzed. After that, the evolution law of the surface deformation with the changing mining height and area-based recovery rate was simulated using the FLAC3D software. The maximum recovery rate and the corresponding mining height, the area-based recovery rate were preliminarily determined, while the surface deformation fell within the allowable range. Simulations of evolutions of the plastic zone width, elastic core ratio, and vertical stress of coal pillars with varying coal pillar width under the maximum recovery rate were performed. The optimal mining scheme had a mining height of 10, a mining width of 100, a coal pillar width of 122 m. It ensured the coal pillar’s long-term stability with the surface deformation within the allowable range and achieved the maximum coal recovery rate of 45%. These findings are considered instrumental in the customized shortwall mining of extra-thick coal seams under buildings, in particular, under Eastern China mining and geological conditions.

Stowing is an important aspect for mine stability and surface subsidence. In general, sand is used as a standard stowing material in most of the underground coal mines in India. But now-a-days, sand is being excessively used in construction industry, whereas its replenishment is very slow. Thus, the study's significance is to identify alternate material for stowing which can replace sand. The aim of the study is to find the suitability of bottom ash as stowing material with and without addition of settling agent. Potassium aluminium sulphate [K2(SO4).Al2(SO4)3·24H2O] is used as the settling agent. Different experiments are conducted for physical and drainage characterization of bottom ash. A prototype for simulating stowing operation in the laboratory is fabricated and the efficacy of the bottom ash with and without addition of settling agent is calculated by conducting various experiments. The experiments have been carried out using different percentages (i.e. 2%, 4%, 6%, and 8%) of settling agents. Bottom ash-water slurry at 50% concentration (by weight) with addition of 4% settling agent (by weight of solid) has found to be most effective for stowing operations based on faster percolation, quick settlement and good permeability characteristics. Load-bearing capacity test of the filled solid after stowing is carried out to find the empirical equation to predict the percentage of settlement with respect to in situ stress for particular range of depths. Settlement percentage of the stowed bottom ash is found to be in the range of 10.34–12.71% for the depth of 50–90 m.

We describe the history of studying the current crustal movements by various methods and discuss technogenic effects recorded at large water-reservoir zones and mineral deposits in Siberia. Initially, classical surveying techniques aimed to obtain high-accuracy ground-based measurements of height, tilt and direction. Modern geodesy techniques and methods for measuring absolute gravity are now available to investigate displacement, deformation, tilt and other phenomena taking place on the Earth’s surface. These methods are used to estimate kinematic parameters of the crust areas (e.g. rates of subsidence and horizontal movements) and to monitor fluid motions in mineral deposits. Such data are critical for ensuring a proper management of the mineral deposits. In this article, we analyse technogenic processes observed in the Ust Balyk oil-gas field, the Zapolyarny gas deposit, the water-reservoir zone at the Sayano-Shushenskaya hydroelectric power station (SSHPS) on the Yenisei river, and large open-pit mines in the Kuzbass basin. Our analysis is based on surface displacement rates estimated from the data collected in different periods of observations at large man-made facilities. In the study of the hydro technical objects, we estimated the displacement rates at 5.0 mm per year. In the northern areas of the West Siberian petroleum basin, subsidence rates amounted to 20–25 mm per year in the early 2000s. These estimates were supported by the high-accuracy gravity measurements showing an increase up to 6–7 microGal per year in the oil-gas field development areas. We assess a possibility of triggering effects related to weak seismicity due to a high stress accumulation rate (1 KPa per hour) in the SSHPS area. A connection between earth tides and catastrophic events, such as gas emissions in high amounts on mining sites, is discussed. Having analysed the surface monitoring records taken in South Primorye in September 2017, we conclude that underground nuclear explosions in North Korea in this period did not cause any significant displacement of the surface in this most southerly region of the Russian Far East territories.

Backfill coal mining, an environmentally friendly practice, is widely used to mitigate the hazards of water and sand inrushes (WSIs) and surface subsidence. In this study, a quantitative analysis for assessing the hazard reduction of WSIs due to backfilling was established that combines a modified analytic hierarchy process (AHP) with a geographic information system (GIS) and entropy. The analytical and quantitative model consists of four criteria and eight factors for the hazard assessment target layer. The weight of each index is comprehensively determined based on the modified AHP and entropy. Then, a hazard zone map that is color-coded is overlay analyzed based on GIS to comparatively evaluate the degrees of hazard from WSI due to longwall caving and paste backfill. The Taiping coal mine was used as a case study to validate the accuracy of the evaluation model. The results indicate that paste backfilling can effectively reduce the influence of the overburden failure height on WSI hazards. The highest hazard index of backfill mining was significantly reduced, and high-hazard and very high-hazard zones of longwall caving were transformed into low-hazard or even no-hazard zones. The evaluation results are in good agreement with actual engineering practices and offer an effective reference for practical engineering projects and prevention and control measures for safe mining under loose sand aquifers.

Land surface subsidence due to excessive groundwater pumping is an increasing concern in California, USA. Interferometric Synthetic Aperture Radar (InSAR) is a remote sensing technique for measuring centimeter-to-millimeter surface deformation at 10–100 m spatial resolution. Here, a data-driven approach that attributes deformation to individual depth intervals within an aquifer system by integrating head data acquired from each of three screened intervals in a monitoring well with InSAR surface deformation measurements was developed. The study area was the Colusa Basin in northern Central Valley. To reconstruct the surface deformation history over the study area, 13 ALOS-PALSAR scenes acquired between 2006 and 2010 were processed. Up to ~3-cm year−1 long-term subsidence and up to ~6 cm seasonal subsidence were observed using the InSAR technique. The technique developed in this paper integrates the InSAR-observed seasonal deformation rate and the co-located head measurements in multiple depth intervals to estimate the elastic skeletal storage coefficient, the time delay between the head change and the observed deformation, and subsequently the deformation of each depth interval. This technique can be implemented when hydraulic head measurements within each depth interval are not correlated with each other. Using this approach, the depth interval that contributed the most to the total subsidence, as well as storage parameters for all intervals, are estimated. The technique can be used for identification of the depth interval within the aquifer system responsible for deformation.

We discuss the results of gravimetric and satellite geodetic measurements at the Zapolyarnoye and Yamburgskoye gas and oil deposits in Transpolar Western Siberia in subarctic zone of Yamal-Nenets autonomous okrug. The development of mineral deposits and large number of pipelines require monitoring of recent motions of the Earth’s surface. Displacements and other phenomenon were studied by satellite geodesy and absolute gravimetry. It is now possible to obtain the kinematic parameters (rates of subsidence and horizontal motion) and addition information on fluid motion into the layers of the deposits. The ground displacements rate in different short periods recorded at large man-made objects are shown. Rates for hydroobjects are estimated at 5 mm/yr. The gravimetry and satellite geodesy results obtained at the Zapolyarnoye deposit in the northern part of Western Siberia were analyzed. Subsidence rates of 21–23 mm/yr were estimated. An increase in gravity of up to 7 µGal were recorded at the deposits (2006–2008). In this case, the increased gravity is related to surface subsidence (with a normal vertical gradient). Subsidence rates of 16–21 mm/yr were estimated at the Yamburgskoye field. This result is consistent with the rates at Zapolyarnoye. The horizontal rates and orientation differed at different deposits.

During TBM construction of urban underground tunnels, it is necessary to strictly measure the surface subsidence, crown settlement inside the tunnel, clearance convergence, horizontal, and vertical displacement of pile wall. In this study, to better understand the TBM construction parameters and the stress and displacement inside the tunnels and pile wall with time, a nonlinear viscoelastic constitutive equation for variable modulus considering the time effect is established. Through laboratory tests on the sandy mudstone samples of Chongqing Metro Line 9, basic mechanical parameters are obtained, and the calculation parameters of the constitutive equation for variable modulus are also obtained. By using generalized rheological theory, numerical calculations are performed on the surface subsidence and surrounding rock deformation, with the calculation results basically consistent with the field measurement results. The accumulative change value for surface subsidence is subject to logarithmic law, and our results can be used to quantitatively guide the collaborative relationship between tunnel excavation and support, dynamically adjust TBM construction parameters, and predict surface subsidence and surrounding rock deformation, thereby providing guidance and reference for similar projects.

In this study, the No. 6 pit in the eastern mining area of the Jinning phosphate mine in China was taken as the research background. In order to reduce the cost of filling, an improved pillarless sublevel caving method is proposed. This method greatly improves the ore recovery rate by adding a recovery route. In addition, the combination of similar material simulation experiments and numerical simulations (discrete element and universal distinct element code) revealed the deformation and failure laws of the surrounding roof rock and the characteristics of the surface subsidence. The results indicate the following. (1) The similar simulation experimental results indicate that the deformation of the overlying rock layer originated from the direct roof of the goaf and gradually developed into the deep part of the rock layer. An irregular stepped caving zone formed in the goaf. The maximum surface subsidence was located above the phosphorus orebody, and it gradually decreased toward both sides. As the stope approached propulsion, the location of the maximum subsidence gradually moved toward the propulsion direction. (2) The numerical results revealed that the displacement of the overlying strata was nonlinear, and it decreased with increasing roof height. A support pressure concentration area was formed within a certain range of the stope roof. The numerical simulation results are basically consistent with the similar simulation experimental results.

Coal bump often occurs in coal mining among many working faces in mine group under the control of large geological bodies. In order to study the coal bump mechanism between adjacent working faces under the conditions of large fault and huge thick overburden conglomerate, this paper regards Yima mining area as a practical engineering background and theoretically analyzes the mechanical behavior of overlying rock in the spatial structure. Then, the deep-ground and whole-space measurement is carried out in the 13230 working face of Gengcun mine and 21121 working face of Qianqiu mine. The results show that the basic structural unit in Yima mining area is composed of two goafs, middle coal pillar, and overlying conglomerate. Under the condition of nonsynchronous mining in adjacent working faces, there is a comovement effect similar to lever’s “prying” phenomenon in thick conglomerate beam—the conglomerate strata above larger goaf side induce an overall uplift movement of the corresponding strata above smaller goaf side, and uplift length of the conglomerate strata is related to the mining length, coal pillar width, caving angle, and coal-conglomerate distance. The results of surface subsidence, microseism, and stress in the two working faces verify the conglomerate’s phenomenon of comovement effect and disturbance range and further explain the role of active movement of F16 fault and overall causes of huge thick conglomerate on the coal bump. The vertical stress of the 13230 face is relatively low at the beginning, and high horizontal stress by fault activation causes typical bump accident with the horizontal sliding of coal body. With the increasing development of 13230 face, the intensity and frequency of coal bump in horizontal direction decrease obviously, but with high proportion in vertical direction. The results provide a theoretical basis for the study on the mechanism of coal bump between two adjacent working faces under the conditions of huge thick conglomerate and large thrust fault.

Monitoring large gradient ground deformation due to temporal and spatial image decoherence has long been a challenge. We attempted an improvement using Sentinel-1A and Sentinel-1B C-band data fusio...

Shaft stability evaluation (SSE) is one of the most crucial and important tasks in view of the role of vertical shaft in mining engineering, the accuracy of which determines the safety of on-site workers and the production rate of target mine largely. Existing artificial methods are limited to the amount of data and complex process of modeling as well as rare consideration of comprehensive evaluation model in this field. In this way, this paper introduces a high-efficient model that incorporating the unascertained measurement (UM) and multiple weights (the analysis hierarchy process, entropy and the criteria importance through intercriteria correlation) to meet the engineering requirements. Simultaneously, the main parameters, including surface subsidence velocity, cumulative surface subsidence(CSS), loose strata thickness(LST), the water level drop in aquifer (WLD), shaft wall thickness, construction methods and shaft wall types, and diameter ratio of shaft and shaft lining quality, are prepared to analyze the shaft stability. Linear and nonlinear membership functions are utilized to investigate the index correlation belonging to different risk levels. The stability class is determined through the index measurement vectors and classic classification criteria considering the individual index importance. The confusion matrix-based results show that the ensemble model with optimal structure has inspired performance in SSE with 100% accuracy. Furthermore, the shaft is sensitive to the factors CSS, LST and WLD using the sensitivity analysis. Additionally, some parameters associated with the shaft stability are investigated from Daye Iron mine (China) to validate the applicability of target model, the results of which are consistent to the on-site conditions perfectly. Findings reveal that the constructed model has great potential in assessing the shaft stability, which is beneficial to eliminate the risk of shaft failure in time.

Focusing on Hualien earthquake which happened on April 18th in 2019, this research took Sentinel-1A/B SAR images as data source, extracted deformation field through DInSAR and MAI technology, analyzed deformation features based on interferogram, geological structure, distribution of aftershocks and the vertical PGA monitoring results. Our results showed that the maximum displacement of land surface subsidence near the seismic focus areas in LOS direction reached up to 3.6 cm, and the maximum displacement near the seismic focus areas in azimuth direction reached up to − 3.5 cm, both less than 4.0 cm. That was to say, the displacement in both direction caused by this earthquake was not significant in study area. And the previous research results indirectly implied that the extraction results of deformation field were reasonable near the seismic focus area. Then, based on the previous research results on geological structure, regional tectonics, reverse-type earthquake rupture and PGA, through the analysis on surface deformation field, vertical PGA results and surface cover types in the study area, we could indicate that, due to the effect of terrain on refraction and reflection of seismic wave, the impact of terrain on vertical PGA exceeded that of the epicentral distance.

In this study, an improved Knothe time function model is established via analogical reasoning from a phenomenological perspective, based on an inverse “Hohai creep model” function, in accordance with the antisymmetric relationship between the unstable creep curve and surface dynamic subsidence curve. An empirical method and fitting method are proposed to determine the parameters of the improved model based on the availability of measured field data. The accuracies of the two models are compared with monitored data from eight monitoring points in the main strike profile of the Guotun coal mine subsidence basin. The results show that the improved model can more accurately reflect the dynamic process of surface subsidence. The average relative standard deviation of the improved model is only 4.9%, which is far lower than the 23.1% associated with the Knothe model. This verifies the improved model’s accuracy and reliability. The model parameters for different monitoring stations obtained using the fitting method are similar, which shows that the model parameters are regular and can be easily applied.

In the process of coal mining, the surface subsidence under ultrathick loose layer is abnormal (subsidence coefficient greater than 1.0), which will cause great damage to the surface ecological environment. The fracture propagation and stress evolution of bedrock are of great significance to the prevention of surface subsidence. Taking the 1305 working face of a mine as the background, this paper study the process of crack propagation and stress evolution of bedrock under the influence of ultrathick loose layer by methods of on-site measurement, similar simulation, and numerical simulation. During the research process, the physical model was verified by the measured data. Then, the numerical model was verified by the crack propagation angle and subsidence of bedrock, which were obtained in a similar simulation. Based on the verified numerical model, it was obtained that after the coal seam was mined out, the bedrock above the mined-out area was mainly damaged by tension, while the strata on both sides of the crack expansion angle were mainly damaged by shear and tension. During coal seam mining, for bedrock the process of fracture expansion, subsidence, and stress evolution all could be divided into four stages. This research provides a basis for the control of surface subsidence.

This paper presents the results of a unique study conducted by the National Institute for Occupational Safety and Health (NIOSH) from 2016 to 2019 to evaluate the effects of longwall-induced subsurface deformations on shale gas well casing integrity and underground miner safety and health. At both deep-cover and shallow-cover instrumentation sites, surface subsidence measurements, subsurface in-place inclinometer measurements, and underground pillar pressure measurements were conducted as longwall panels were mined. Comparisons of the deep-cover and shallow-cover test site results with those from a similar study under medium cover reveal an interesting longwall-induced response scenario. Under shallow and medium covers, measured horizontal displacements within the abutment pillar are one order of magnitude higher than those measured under deep cover. On the other hand, measured vertical compressions under deep cover are one order of magnitude higher than those under shallow and medium covers. However, FLAC3D simulations of the casings indicate that, in all three cases, the P-110 production casings remain intact under longwall-induced deformations and compressions, which has serious implications for future mine design in areas where shale gas wells have been drilled ahead of mining.

Surface movement and deformation with faults differ significantly from that without faults, which the surface movement and deformation at the fault outcrop generally abnormally increase when a fault occurs in the overlying strata and loses stability as a result of mining. To explore the mechanism of abnormal surface subsidence induced by fault instability due to mining in the hanging wall and footwall, mechanical models for the fault slip and soil cantilevers were separately established. Moreover, based on numerical and similarity simulation experiment, the difficulty degrees of fault instability were compared and analysed during mining in hanging wall and footwall. The research results show that: (1) the abnormal surface subsidence at fault outcrop is caused by fracture of soil mass at the fault outcrop due to the cantilever effect. (2) The fault zone that can be stabilised during mining in the hanging wall is broader than that during mining in the footwall, and a fault remains stable when mining in hanging wall and the surface at fault outcrop is more likely to experience stepped subsidence when mining in the footwall. (3) Fault stability worsens with the growth of the fault dip angle when mining in hanging wall, the fault is certainly subjected to slip and instability when fault dip angle is lower than the internal friction angle of the rock mass within the fault zone and fault stability strengthens with increasing fault dip angle during mining in the footwall. (4) When mining in the footwall, the ratio of shear stress to normal stress at the fault outcrop is about five times that when mining in the hanging wall and the fault is more likely to undergo slip and instability during mining in the footwall. (5) As a natural weak plane in the rock mass, a fault exerts a blocking effect on the transfer of mining-induced stress and overburden movements.

The mining-induced strata movement and surface subsidence are closely related to the dip angle of coal seam. However, most surface subsidence prediction methods are empirical, and only suitable for nearly flat coal seam mining. In this paper, a new theoretical method is proposed to predict the strata movement boundary and surface subsidence caused by inclined coal seam mining, which considers the influence of key strata, rock quality and coal seam dip angle. The strata movement caused by inclined coal seam mining is generalized and described by three models: analogous hyperbola model (AHM), analogous hyperbola-funnel model (AHFM), and analogous funnel model (AFM). Considering the rock quality of roof and floor strata, the rock mass rating system is adopted to calculate the surface maximum subsidence and its location. Additionally, the distinct element method was used to assess the performance of the theoretical models. The numerical simulation results match well with theoretical predictions of strata movement boundary and surface subsidence. It is discovered that the appearance of surface subsidence troughs is obviously asymmetric. As the dip angle increases, the surface maximum subsidence decreases and its location is laterally displaced. When the dip angle is greater than 50°, the double subsidence troughs can be visualized clearly. Furthermore, the theoretical predictions of surface subsidence are verified by field measurements of two cases. As a result, the theoretical predictions of surface subsidence are greatly improved by comparing with the empirical method.

With an increasing number of multi-seam mining projects, the problem of strata movement caused by multi-seam mining has attracted increasing attention. Previous studies have shown that the rock failure mechanism for multi-seam mining is obviously different from single-seam mining. When a lower coal seam is being mined, two issues are apparent: the activation that the upper goaf will suffer and the difference in the break mechanism of the stratum between single-seam and multi-seam mining. The research regarding these two issues is still inadequate. In this paper, a physical model experiment was used to simulate the full longwall mining process of multiple seams. Then, the failure mechanics of the stratum and the influence of mining the lower coal seam on the activation of the upper goaf are discussed under the condition that the upper coal seam has been fully mined. The results show that a part of the fracture zone that formed by mining the upper coal seam will be converted into a caving zone when the lower coal seam is mined. In multi-seam mining, the cracks in the overlying fractured rock mass will widen and propagate upward. During the process of mining the lower coal seam, the interburden rock mass presents a typical plate bending failure, and the break location is greatly affected by the distribution of the periodic weighting in the upper coal seam mining. Multi-seam mining will cause the surface subsidence trough produced by upper coal mining to move towards the end of the mining panel. The mechanism of rock stratum movement revealed by the test has a certain practical guidance for the control of roof pressure in multi-seam mining and the subsidence of surface.

The article highlights the aspects of RSE technologies adaptation during the forward hydrogeological predictions development and for the purposes of the surface flooding zones spreading estimation within coal-mines fields, being flooded. Previously developed numerical geofiltration model allows to return filtration settings of the massif of rocks, that was broken due to coal extraction, and to identify the influence features of the mine workings flooding regime on the general hydrodynamic settings around the flooded mines. As a result of geofiltration modeling the forecast cartographic scheme of groundwater table level position at the final stage of mine workings flooding was obtained. To take into account the influence of surface subsidence over the mine workings on flooding zones distribution, the values of maximum possible vertical surface displacements over the mine workings contours were calculated, based on geological and surveying data. The relief mathematical model was developed with given expected vertical deformations using the GIS-techniques and the original DEM of the territory.The result of the radar satellites images processing is a cartographic model that demonstrates the intensity of uplift movements of the earth surface. Areas of distribution of large-amplitude movements (10-20 mm/year) were determines. As a result, an updated scheme of the forecasted flooded zones was developed.

Large-scale land creation projects involving the cutting of mountains to infill gullies for construction have been carried out in Lanzhou New District (LZND). However, there is an urgent need for comprehensive and detailed research on the spatiotemporal evolution of ground deformation in LZND. Based on Sentinel-1A SAR data, combined with the urban geological background, the ground deformation in LZND from 2017 to 2019 was analysed. Two independent, multi-temporal techniques, persistent scatterers interferometry (PS-InSAR) and the small baseline subset (SBAS-InSAR), were used to calculate the deformation time series, and the results were cross-verified. The time series-monitoring results of the SBAS and PS calculations exhibited strong consistency in LZND and verified the high reliability of the experimental results. The results showed the whole surface of the LZND from March 2017 to October 2019 maintained stability, and the deformation rate was primarily in the range of −10 to 10 mm/year. However, ground deformation in the Xicha area was evident. The maximum annual deformation rates monitored by SBAS-InSAR and PS-InSAR were −52.48 mm/year and −56.35 mm/year, respectively. The most typical deformation areas include the built-up area and the land creation area. The surface subsidence area was concentrated in the filling area. The ground deformation range of LZND kept expanding and accelerating from 2017 to 2019. Land creation, urban construction, geology and precipitation were the primary factors contributing to local severe ground deformation. The results of this study provide reference for the regional urban planning in LZND.

In order to improve the accuracy of the surface dynamic prediction model in mining areas with thick unconsolidated layers and improve Knothe time function, the influence coefficient was firstly changed into the coefficient in exponential form, and the influence coefficient of unconsolidated layer was added. Then, a subsidence basin prediction model for mining under thick unconsolidated layers was established. Next, the model was combined with the improved Knothe function, thus constructing a new mining subsidence prediction model. The new subsidence prediction model was applied in 1414 (1) working face in Huainan mining area. The results showed that the integrated model could better reflect the subsidence process, and the prediction values and the measured values agreed well.

Subsurface strata movements and deformations associated with longwall mining operations in underground coal mines could cause various disturbances to subsurface mine structures, ground water bodies, and coalbed methane reservoirs. In order to assess those disturbances correctly and to design effective and efficient mitigation measures, it is necessary to develop an accurate prediction model for subsurface strata movements and deformations. Decades of research have demonstrated that variations of stratification and lithology in the overburden have significant influence on the subsurface strata movements and deformations during ground subsidence process. The key strata theory states that the thick and hard key strata serve as the backbone of the overburden and control the movements of the thin and soft weak strata located above them. From an engineering standpoint, the overburden strata are subdivided into several individual groups by the key strata with each group consisting of a key layer at the bottom and weak layers overlying it. A new subsurface subsidence prediction model considering the key strata effects on subsurface strata movements and deformations has been proposed. In this method, elastic modulus, specific weight, tensile strength, and uniaxial compressive strength (UCS) of each layer are used to identify the key layers and to determine the needed subsurface subsidence parameters. The influence function method, proven to be accurate and versatile for surface subsidence prediction, was employed to predict the subsidence on each of the overburden layers from mining horizon progressively upward to ground surface with the assumption that the predicted subsidence on a given layer serves as the subsidence source for the layer immediately above. The enhanced subsurface subsidence prediction model has been demonstrated with an actual case to show its applicability and improvement.

Longwall extraction of coal seam disturbs the whole overburden strata, from the coal seam to the surface, and forms a subsidence basin. This paper investigated the mechanism of the overburden strata bending deformation, the alluvium mechanical parameters, and their effect on surface subsidence by the theoretical analysis and numerical simulation analysis. The dynamic processes of overburden failure and surface subsidence due to longwall mining was analyzed by a novel two-dimensional trapezoidal-area method. A “π-shaped” model was first developed to reveal that surface subsidence consists of the overburden strata bending deformation and the subsidence of the alluvium. The process and mechanism of the overburden strata bending transfer were analyzed, and two mechanical models of the strata bending deformation were established, i.e., the strata suspended bending model and the strata overhanging bending model. The maximum subsidence equation of the overburden strata bending basin was derived based on the theoretical analysis. Also, the effect of the alluvium mechanical parameters on the surface subsidence was investigated by numerical simulation analysis. The rationalities of the numerical simulation were validated by the field measurements. The results show that surface subsidence increases logarithmically during increased alluvium thickness and decreases exponentially and logarithmically during increased internal friction angles and increased cohesions, respectively.

In recent years, block caving has drawn the attention of many mine enterprises due to the admired extraction rate and lower cost, which can exploit the materials via gravity inflow. At the same time, the limitation of this advanced method cannot be underestimated easily, such as surface subsidence and boulder, usually, the latter leads to the frequent secondary blast and damage of bottom structure. Thus, it is significant and crucial to evaluate the fragmentation before the implement of this method. But, traditional fragmentation assessment model suffers from the complex process of modeling and simulation. In this study, a hybrid model consists of unascertained measurement theory and information entropy was constructed to meet the requirements of this prospective mining method. Considering the influence of various parameters on rock fragmentation at the same time, twenty-three factors (i.e., uniaxial compressive strength, modulus ratio, fracture frequency, aperture, persistence, joint orientation, roughness, infilling, weathering, in situ stresses, stress orientation, stress ratio, underground water, fine ratio, hydraulic radius, undercut height, draw column height, draw points geometry, draw rate, multiple draw interaction, air gap height, broken ore density and undercut direction) were chosen to extract the main characteristics of rock mass samples from the two different mines, namely Reserve North (Chile), Diablo Regimiento (Chile) and Kemess mine (Canada). A new membership function (logarithm curve) was added to eliminate uncertainty results from the low level of knowledge about rock mass properties. Then, information entropy was performed to quantify the impacts of individual index. A credible degree identification criterion (Rη) was also applied to review the sample attributes qualitatively. Ultimately, degree of fragmentation of the three samples was judged easily on the basis of a composite measurement vectors and Rη. The evaluation results showed that the fragmentation grades of Reserve North, Diablo Regimiento and Kemess mine, separately, were “Good”, “Medium” and “Good”. With regard to the excellent performance of this hybrid model, it can be seen as a reliable approach to describe the fragmentation potential during the ore extraction using block caving mining method.

Subway subsidence and the consequent geological hazards have become one of the major concerns especially in China’s large cities. Large spatial-scale and temporally continuous measurements of surface deformation due to subway subsidence is the basis of the intelligent management for urban transit, as well as the guarantee for the early warning of geological disasters. In this paper, we used persistent scatterer interferometric synthetic aperture radar (PS InSAR) measurements to study and characterize the deformation process resulted from subway-induced subsidence in the construction and operation periods of Suzhou subway using 24-scene high-resolution TerraSAR data (from December 2009 to April 2015) and 19-scene low-resolution Sentinel-1A SAR data (from May 2017 to February 2020). Our results indicate spatially different subsidence rates at different segments along the Suzhou subway lines 1, 2, 3, 4, 5 and 6. TerraSAR data indicate the maximum subsidence rate of −13 mm/yr, while Sentinel-1A data demonstrate the maximum subsidence rate of −20 mm/yr. The decadal-scale subway subsidence deformation is generally characterized by its multistage dynamic processes. The significant subway subsidence is mainly distributed around interchange hubs at the intersection area of railway lines. The Peck function model is used to fit the subway subsidence displacement profiles, which reveals the normal distribution characteristics of the subway surface subsidence. Based on our timeseries analysis in different time periods, the logistic cycle function is used to invert the subway subsidence timing, which reveals four first-order stages during subway subsidence: slow acceleration period, fast acceleration period, decay period and steady-state period.

Land subsidence monitoring in mining areas is one of the main applications of surface deformation monitoring, which is of great significance for safety production. Using the IPTA (Interferometric Point Target Analysis) time-series InSAR (Interferometry Synthetic Aperture Radar) method, land subsidence data of the new exploration area in the Weizhou mining area were analyzed and compared with static GPS (Global Positioning System) monitoring data from 2017 to 2020. Gray-Markov model was established by combining the gray prediction model with the Markov model to predict the surface subsidence of the mining area. The results show that (1) InSAR data has high accuracy and application potential in prediction of long-term surface deformation in mining areas; (2) The Gray-Markov model can better reflect the volatility and practicality of subsidence data in mining areas; (3) The prediction results have high accuracy, and the Gray-Markov model can serve as an effective guide for long-term surface deformation monitoring and safety management.

Surface subsidence that results from longwall mining can be large magnitude and can affect significant areas. Conventional methods for subsidence monitoring include leveling, global positioning system (GPS), and photogrammetric surveys. Remote sensing techniques including, aerial LiDAR, terrestrial laser scanning, and satellite-based Differential Interferometric Synthetic Aperture Radar (DInSAR), are also used to measure deformation associated with subsidence. DInSAR data are different than data from conventional subsidence surveys. Images capture data over large areas (hundreds of kilometers), and each pixel (data point) in an image quantifies the average displacement over an area of square meters. DInSAR data can have fairly high time resolution; imaging periods typically range from weeks to months. DInSAR data can be useful to monitor subsidence sequentially over short periods. Regularly monitoring subsidence may help define if caving is progressing normally and can establish relationships between surface deformation and longwall face advance, which has potential to help quantify possible risks to mine stability. In this study, subsidence at a longwall trona mine is monitored over short periods, typically 12 days, as the longwall face is advanced through a panel. C-band interferometric wide swath synthetic aperture radar (SAR) images from the sentinel satellites are used to quantify the subsidence. The onset of subsidence occurs close in time to the beginning of the longwall face advance, and overall, the development of subsidence closely follows the longwall face advance.

Over the past decade, Chengdu has become one of the fastest growing urban centers in China. However, the massive expansion of the infrastructure and the transportation network has resulted in surface subsidence which typically presents as a hard to detect geological hazard. As an all-day, all-weather, high-precision, and wide-range surface deformation monitoring tool, interferometric synthetic aperture radar (InSAR) technology has unique advantages with respect to monitoring long-period surface subsidence. In this article, the Sentinel satellite data from March 2018 to March 2021 for the ascending and descending orbits are used to obtain the deformation fields of Chengdu's surface in two different satellite line of sight directions using the time-series InSAR technique. The results are then used to invert the surface deformation field in the vertical direction and analyze it via the Peck and Logistic models. In addition, wavelet transform technology was used to investigate the relationship between deformation and climate. The results show that the surface deformation in Chengdu is stable, and the rate of deformation in the center of the urban area is within 5 mm/year. The main reason for the emergence of ground settlement funnels is the construction of subways and real estate development. It was also observed that the deformation of the buildings shows a clear periodic pattern, which is closely related to the seasonal rainfall and temperature in Chengdu.

Accurate prediction of surface settlements is a primary concern when deep excavations were carrying out under the water table in urban environments for the safety of the work site. The sedimentation deformation due to deep excavation of foundation pit and dewatering occurs as a result of coupling action of the two factors. The study is aimed at revealing the coupling ground response to the two factors and developing empirical correlations for estimating ground deformations. Taking a deep foundation pit of a metro station as an example, surface settlement estimations were calculated by analytical formulas and numerical models. The settlement results by analytical formulas under excavation and dewatering conditions were added linearly to the total settlements. And three-dimensional coupling numerical models were established by applying commercial software (GMS and MIDAS) to investigate the interaction impact of excavation and dewatering on the sedimentation deformation. Comparing with monitoring data, numerical simulation results match well with the monitoring data. Furthermore, an empirical surface subsidence correlation equation was developed by the polynomial fitting to illustrate the effect contribution on the total surface settlement of foundation excavation and dewatering.

Surface subsidence prediction is an important approach to evaluate the surface damages caused by backfilling mining activities, and is applied to guide the recovery of coal resources under building...

One of the important issues to study underground coal gasification (UCG) is the prediction of surface subsidence. Several parameters that influence these conditions are the thickness of cap rock, the physical and mechanical characteristics, the structure condition, the minerals composition of the rock, and external conditions. This study had been carried out simulation and modeling to determine the level of surface subsidence risk and the effect of high temperatures due to the activities. The modeling results show that the thickness of the rock above the UCG coal seam greatly affects the surface subsidence. The depth is more than 200 m and found that the SF value is 1.59 which indicates UCG reactor depth of ≥ 200 m is safe from the risk of subsidence. From the characteristic aspect of the cap rock, the claystone types which not contain kaolinite minerals are more prone to collapse than those of contain kaolinite minerals. From this models, the gasifier at 150 m depth was estimated that there will be a decline of -7.23 m, and the minimum subsidence is at 275 m about 0.1 m. The heat propagation modeling results show that at 50 m the temperature is estimated to be 213- 289°C, but if the thickness of the cap rock is > 200 m depth, the temperature is around 29-28°C.

Using abandoned salt caverns for the disposal of solid wastes is one of the most effective and safest methods to deal with potential hazards caused both by the abandoned caverns and by the solid wastes. To investigate the geomechanical behavior of abandoned salt caverns used for solid waste disposal (alkali wastes), a discrete-continuous coupled method is proposed. In the proposed method, alkali wastes (discrete materials) are simulated using the discrete element method (DEM) while the caverns are simulated using the finite difference method (FDM). This method can overcome the shortcomings of the traditional method of treating the alkali waste as continuous materials with low strength, which cannot accurately depict the interaction between the cavern and alkali waste. Using the proposed method, a 3D geomechanical model is built to investigate the long-term mechanical behaviors of the cavern and alkali waste. The results show that the alkali wastes have significant effects on reducing the cavern convergence while the cavern convergence compacts the alkali wastes. Consequently, the surface subsidence induced by the convergence of the cavern is much smaller than that of a cavern which does not contain alkali wastes. This study provides a prerequisite to evaluate the effect of filling abandoned salt caverns filled with alkali wastes and also can serve as a reference for stability analysis of gas storage salt caverns that contain insolubles.

The cross-sectional area of the tunnel, fortified with a rim, is always smaller than the excavation area in the ground. Exact methods are still very arbitrary and need to be improved. The article presents the results of calculating the internal force factors of a monolithic reinforced concrete frame of a vaulted tunnel. The data obtained in the calculation of the PC "PLAXIS-8".

Accurately estimating load distributions and ground responses around underground openings plays a significant role in the safety of the operations in underground mines. Adequately designing pillars and other support measures relies highly on the accurate assessment of the mining-induced loads, as well as the load-bearing capacities of the supports. There are various methods that can be used to approximate mining-induced loads in stratified rock masses, both empirical and numerical. In this study, the numerical modeling approach recently developed at West Virginia University, which is based on the modeling approach developed by the National Institute for Occupational Safety and Health (NIOSH), is investigated using the finite difference software FLAC3D. The model includes the longwall panels, the adjacent chain pillar systems, and the different stratigraphic layers of the overburden. Using the 3D model, changes in loading conditions and deformations on the areas of interest, induced by an approaching longwall face, can be examined. This paper details the 3D modeling of a longwall panel utilizing this approach, and the verification of the results against field observations. The studied panel was 360 m wide with a 3-entry chain pillar system and about a 160-m average overburden depth around the studied area. The overburden strata consist of alternating layers of shale, sandstone, and limestone. The FLAC3D results were compared against field measurements from the mine site. The stress change values measured in the chain pillars were comparable with the modeling results. The model also replicated the surface subsidence profile obtained from field measurements fairly well. Overall, the 3D modeling approach was found to be successful for the case study longwall panel.

Surface subsidence over coal mines in western China is serious. Collapse pits, step subsidence, surface cracks, among others occur during coal mining. Based on data of surface subsidence in western mining area, this study analyzed the control of key strata on surface subsidence. The breaking mode of the main roof with different thicknesses was discussed based on self-designed simulation test device for the initial breaking of main roof. Through physical experiments, two types of breaking models of the main roof, namely horizontal “X” type and vertical “X” type, were obtained. With the increase in the thickness of the roof, the roof was more prone to sliding instability. Based on Reissner’s thick plate theory, mechanical model of the initial breaking of the main roof was established, and the parameters such as thickness, step distance, Poisson’s ratio, and burial depth were introduced. Through theoretical analysis, the fracture critical condition and breaking mode partition of main roof were obtained. According to the characteristics of surface subsidence of shallow coal seam, the mechanism of strata movement controlled by layered hydraulic fracturing technology was analyzed in the western coal mines of China. This study provides a theoretical reference for the prevention of main roof sliding instability and the control of surface subsidence.

Taking the shield tunnel project of Guangzhou Metro Line 8 from Tongdewei Station to Shangbu Station as the research background, using the research method of finite element simulation and site monitoring, this paper analyses the influence rules of shield tunneling on ground subsidence under the condition of different hard rock height ratios. The research results show that in the process of crossing different hard rock height ratio composite stratum, as the hard rock height ratio decreases, the value of ground settlement decreases and settlement tank becomes shallow. The surface subsidence in different hard rock height ratio strata is obviously different, and the maximum difference is about 8.6 mm; The influence of the hard rock height ratio on the surface longitudinal settlement is mainly reflected in the position change of the beginning and the end of the settlement. With the increase of the hard rock height ratio, the shield construction reduces the amount of the surface longitudinal settlement and its influence range; Through the research, it is found that the hard rock height ratio in the 0-0.2 and 0.5-1 is the sensitive interval, and the settlement value in these two hard rock height ratio interval varies greatly. It is necessary to pay attention to the uneven settlement of the ground surface caused by shield construction in the sensitive hard rock height ratio interval. The research results of this paper can provide reference value for similar shield construction in upper soft and lower hard composite stratum.

Recent research has demonstrated that the Sentinel-1 constellation can be used for continuous tracking of ground deformation phenomena. In this study, the spatial–temporal subsidence characteristics in Nanning were investigated with 18 Sentinel-1A TOPS synthetic aperture radar (SAR) images acquired from 25 June 2015 to 16 December 2016 based on the small baseline subset interferometric SAR (SBAS InSAR) technique. The results showed that the annual average surface deformation rates in Nanning ranged from − 48 mm/year to 20 mm/year, and the maximum deformation was detected in the Langdong area. The SBAS-derived results were validated by Nanning continuously operating reference station (CORS) and levelling measurement data. The correlation coefficient and root-mean-square error (RMSE) between SBAS-derived and levelling-derived mean deformation rates were 0.79 and 2 mm/year, respectively. The maximum discrepancy and the RMSE amounted to 7 mm/year and 4 mm/year comparing the SBAS time-series with the CORS-measured displacement. The verification using levelling and CORS implied high reliability and precision of surface subsidence derived by SBAS InSAR. Our analysis revealed that surface subsidence in Nanning was mainly caused by large-scale urban construction, which should be paid enough attention to avoid further aggravation. With the help of the meteorological data, we also found that the subsidence in Nanning was closely related to climatic anomalies in 2015. This research work will provide important theoretical and practical reference value for urban planning and construction in Nanning.

The coal seam mining-induced characteristics of overlying strata fracture and surface subsidence are tested and numerically analyzed using the similar materials. Two mining models were conducted in a laboratory with two different rock orientations and slopes to simulate the stability conditions and driving conditions of the loess land slope of under the guides of the V-shaped law. Given a 30° dip angle of coal seam in the Model 1, the results show that the loess landslide on top of inclined rock layers is in the state of critical instability when working face advances to 100 m. Whereas, given a 30° dip angle of coal seam in the Model 2, the loess landslide on top of anti-inclined rock layers is in the state of critical instability when working face advances to 120 m. Numerical analysis using a discrete element method was performed to compare the analysis results with laboratory findings. Based on the test and numerical analysis results both indicate that the land sliding along loess land slope are most likely be triggered on inclined rock layers than anti-inclined rock layers when an underground mining activity begins to excavate.

In order to keep pace with fast urbanization and explosive growth of highway traffic volume in China, more and more super large-span tunnels are constructed or will be constructed in the coming years. It is of great significance to employ a suitable construction method for ensuring construction safety when tunnelling in a complicated geological environment. Based on the reconstruction and expansion project of Binlai in China, this paper aims at studying deformation behaviors and mechanical properties of super large-span and shallow tunnel constructed using the upper-bench CD method. The study results showed that the crown settlement of the pilot tunnel was larger than that of the rear guide tunnel, and the deformation of rock mass tended to be stable after 60 days of excavation. The structural stress changed greatly in the construction stage, the stress distribution of steel rib was mainly under compression, and the maximum compressive stress of shotcrete appeared at the tunnel vault. The supporting structure was always kept in a safe state, and its safety factor was higher than 1.5. However, the upper-bench CD method has poor performance in controlling surface subsidence and horizontal convergence. The study of this paper provides a new construction method and useful reference for similar super large-span tunnels.

When roadways are constructed above or adjacent to heavily mined regions, the ground subsidence caused by pillar collapse inflicts severe damage on these roadways. In this study, some surface subsidence events were first reviewed to present roof caving characteristics caused by pillar failure. The bearing characteristic and failure pattern of a single pillar with or without effect of discontinuity were further numerically simulated using distinct element code (3DEC). It was found that the spalling of pillar or slippage of discontinuity would damage the bearing capacity of pillar during the failure process. The stress at the pillar core could be greater than uniaxial compressive strength of the pillar. However, when a discontinuity runs through a pillar, the slippage of discontinuity would significantly degrade the bearing capacity of the pillar. In pillar support system, if any pillar unexpectedly degrades or loses its bearing capacity, the load transferred from the degraded pillar acts on neighboring pillars, and the shear force also increases at relevant positions. However, the roof cutting and surface subsidence characteristics would perform in different patterns. In some cases, surface subsides slowly; in the worst scenario, shock bump may be induced by pillar and roof collapse.

Ground subsidence caused by mining is increasing day by day, and some enormous disasters have been brought. Some scholars have carried out some results by a single factor analysis, but did not cons...

High-intensity underground mining generates considerable surface subsidence in mining areas, including ground cracks and collapse pits on roads and farmland, threatening the safety of buildings. Large-amplitude subsidence (e.g., >2 m) is usually characterized by a large phase gradient in interferograms, leading to severe phase decorrelation and unwrapping errors. Therefore, the subsidence on the surface cannot be well derived simply using conventional differential interferometric synthetic aperture radar (DInSAR) or other geodetic measurements. We propose a new method that combines both DInSAR and subpixel offset-tracking technology to improve mine subsidence monitoring over large areas. We utilize their respective advantages to extract both the spatial boundaries and the amplitude of displacements. Using high-resolution RADARSAT-2 SAR images (5 m) acquired on February 13, 2012, and November 27, 2012, in the Shendong Coalfield located at the border between Shaanxi Province and Inner Mongolia Province, China, we obtain the subcentimetre-level subsidence of the mine boundary by DInSAR and resolve the metre-level mine subsidence centre based on subpixel offset tracking. The whole subsidence field is obtained by combining and analyzing the subcentimetre-level and the metre-level subsidence. We use the probability integral method (PIM) function model to fit the boundary and central mine subsidence to reconstruct the spatial distribution of the mine subsidence. Our results show that the maximum central subsidence reaches ~4.0 m (beyond the monitoring capabilities of DInSAR), which is generally in agreement with the maximum subsidence of ~4.0-5.0 m from field investigation. We also model the boundary and the central subsidence (the final fitting coefficient is 0.978). Our findings indicate that the offset-tracking method can compensate for the deficiency of DInSAR in large-amplitude subsidence extraction, and the inclusion of the PIM technique helps reconstruct the whole subsidence field in mining areas.

This paper describes a case study of the surface subsidence induced by sublevel caving without sill pillars in the Maogong Iron Mine, China. A comprehensive analysis based on GPS monitoring and numerical simulation is proposed and used to analyze the surface subsidence characteristics and damage range. GPS monitoring results showed that the vertical displacement reached 40.3 mm at the JC5 monitoring station and was accompanied by ground crack development. According to the in situ surface subsidence monitoring data and numerical calibration model results, the corresponding critical horizontal strain and angular distortion due to the surface subsidence were estimated as 1.5 × 10−3 and 2.0 × 10−3, respectively. The numerical results showed that the center of the surface subsidence was located in the hanging wall of the orebody, which changed to its far end with increasing mining depth. In the early surface subsidence stage, macro-tension cracks developed in the hanging wall rock mass, and the slabbed rock mass then collapsed into the cave through rotation and/or translation failure. With increasing mining depth, there will be unfilled goaf in the underground, and the rock mass will gradually collapse under high mining-induced stress concentration. Accumulation of caved rocks and the bulking effect result in slow surface subsidence. Notably, surface collapse will not occur suddenly in Maogong Iron Mine, and potential secondary hazards mainly small landslides in the hillside.

An unexpected surface subsidence in Mexico City on 19 May 2015 prompted a detailed geophysical investigation of the three‐dimensional structure of a collapsed‐soil mine located in a section of the Chapultepec Park in the vicinity of an artificial lake. As revealed from past geological explorations, the subsoil at the site consists of volcano‐sedimentary materials that were quarried in the mid‐20th century; subsequently, during the construction of the park, most of those mines had been only partially rehabilitated, with a potential risk of land subsidence. Near‐surface imaging techniques based on ambient seismic noise as well as microgravimetry, electrical resistivity tomography, shallow seismic refraction methods were evaluated for their applicability to characterize the structure of the collapsed mine. Tomography images computed using ambient‐noise array data characterized the extent of the underground mine showing high‐velocity anomaly, while results from microgravimetry and electrical resistivity tomography analyses indicated the structure through weak contrasts in gravity and resistivity anomalies. Additionally, electrical resistivity tomography results also illustrated the saturated nature of the subsoil. While different methods exhibit different capabilities to constrain such a small spatial feature, the present study highlighted the scope of an integrated approach in confirming the existence of potential voids as well as to estimate soil‐subsidence hazard. In terms of operational convenience and rapid performance, the ambient noise tomography method proved to be a relatively efficient and economical reconnaissance tool for identifying 3D velocity contrasts in an urban environment.

Underground coal gasification (UCG) is a green mining technology with less interference to the environment of mining area. However, underground coal gasification also can cause surface subsidence, ...