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The characteristics of overlying strata movement and the evolution of surface subsidence-related parameters are essential in preventing geological hazards and environmental alterations. This paper comprehensively analyses surface subsidence, overlying strata movements, and dynamic surface characteristics above the No. 24213 working face of the 1930 Coal Mine in Xinjiang, China. A numerical simulation model was established to predict the surface subsidence under a larger dip angle. Various time functions were used to determine the suitable function to predict subsidence speed. The in situ surface subsidence results showed prominent asymmetric characteristics. The tilt value was larger toward the footwall than in the opposite direction. However, the curvature evolution was not overly asymmetric and fluctuates greatly. The maximum surface subsidence value in tendency and inclination were 1800 mm and 433 mm, respectively. Moreover, the movement and advance angles were 77.4° and 66°, respectively. The numerical results were in good agreement with the on-site results; the overlying strata movement shape from underground to the surface was similar to an inclined funnel, and the stable draw angles of both sides were 41° and 82°, respectively. The logistics time function can describe the dynamic subsidence characteristics well for a representative point under large dip angle conditions. The parameters in the logistics time function were related to the rapid deformation stage duration time and initial subsidence speed. This study can offer guidance in predicting asymmetric characteristics in inclined coal seams. [ABSTRACT FROM AUTHOR]

Most prediction methods used to calculate mining-induced subsidence do not involve the formation of overburden, and therefore cannot explain the mechanism of fundamental rock strata movement. Due to the differences of the overburden's formation in different mining areas, to develop a feasible method for determining the movement of overburden is significant. This paper presents an original method for determining the movement of overburden, which is based on the key stratum theory and Mohr–Coulomb failure criteria. The mining-induced movement of overburden is described by two major theoretical models: the Analogous Funnel Model (AFM) and the Analogous Hyperbola Model (AHM). The theoretical predictions of movement boundary of overburden and surface subsidence are given in each model. The Distinct Element Method was used to assess the performance of the theoretical models using a case study of the Antaibao coal mine in Western China. The theoretical and numerical subsidence of the primary key stratum was validated by field measurements, most of which are in good agreement. The theoretical predictions of surface subsidence and the movement boundary of the overburden also match well with the numerical results during supercritical mining. The primary key stratum damages the least in the overlying strata in the Analogous Hyperbola Model. [ABSTRACT FROM AUTHOR]

This paper presents a comprehensive analysis of roof strata conditions, shield pressure, and ground surface subsidence above Panel 42105 of the Buertai Coal Mine in Inner Mongolia, China. A 3D geological model and a 2D numerical simulation model are established to examine the roof strata structures with varying strata conditions. Numerical simulation results demonstrate that the hard rock 1 and 2 roof layers are, on average, likely to break 20 m and 57 m behind the coal face, respectively. It is concluded that when the immediate roof is relatively thin, a cantilever beam is formed, whereas a Voussoir beam is formed when the immediate roof is relatively thick. The patterns of shield pressure and surface subsidence under different roof conditions are also examined. The shield working pressure under the Voussoir beam structure appears to be lower than that under the cantilever beam structure. The average horizontal distance behind the working coal face at which the maximum surface subsidence occurs is 92.1 m. On-site monitoring data are used to explain the causes of the unusual shield pressure and its relation to surface subsidence. Finally, guidelines to predict the shield pressure under similar conditions are provided. [ABSTRACT FROM AUTHOR]

The major environmental consequence of coal mining is anthropogenic land subsidence. In particular, mine subsidence can cause damage to public and private infrastructure such as railroads, roads, pipelines and buildings. What is more, it is an engineering problem which troubles engineering construction and safety. Ground surface deformation is related to the measure of mining and the deformation mechanism of overlying strata above the gob. In this paper, a physical and numerical model on the subsidence of longwall mining within a geotechnical setting is presented. The physical model is developed within the framework of physical similar law and geological model in Henan Province, China. The numerical solution is developed within continuum poromechanics and finite element setting. The law of overlying strata deformation is obtained according to physical model experiment and numerical simulation. [ABSTRACT FROM AUTHOR]

Land subsidence is a typical geological disaster that will produce many secondary disasters and negatively impact human production and life. Human engineering activities (underground mining and coal mining) are the leading causes of land subsidence. This study takes Jining, a typical land subsidence city in eastern China, as a case study to investigate the features and control of land subsidence under the combined action of groundwater extraction and coal mining. A three-dimensional numerical model of land subsidence considering groundwater extraction and coal mining is established. The evolution process of land subsidence in the study area from 2000 to 2020 under the action of groundwater extraction and coal mining was obtained through numerical simulation. Results showed that coal mining was the main cause of land subsidence compared to groundwater extraction in the study area. Different groundwater extraction schemes were proposed to try to control the land subsidence, and the land subsidence features of different schemes from 2021 to 2030 were also investigated. Results showed that the ground rebound phenomenon occurred during the first few years, and the rate and amount of ground rebound decreased over time. After that, land subsidence continued, and its rate gradually slowed. The more mining wells are shut down, the smaller the final cumulative land subsidence will be. According to the comparison of these schemes, the land subsidence is basically stable when the amount of groundwater exploitation wells is closed by 50%, which is a more reasonable and practical exploitation scheme. [ABSTRACT FROM AUTHOR]

This paper presents an investigation on the effect of grouting into multi-bed-separation to control mining-induced surface subsidence. In the overburden without obvious thick-and-hard strata for generating large-scale bed separation, overburden grouting is carried out by increasing the number of boreholes and grouting strata. The scale model test, numerical simulation, and field measurements are used to study distribution and process of bed separation and to compare the overburden failure with surface subsidence due to pre- and post-overburden grouting, with a case study of the Qi'nan Coal Mine, Anhui Province, China. The scale model test and numerical simulation results of the overburden grouting process are in close agreement with those obtained from the field measurements. Filling masses with different diffusion radii are commonly formed in the different bed separation, which are overlaid to control the surface subsidence. It is proven that overburden grouting can successfully mitigate overburden failure and subsidence without obvious hard strata and bed separations. This provides an effective and cost-efficient approach for addressing the surface subsidence and overburden deformation problems due to mining. [ABSTRACT FROM AUTHOR]

Research on land subsidence is a global topic. In recent years, the environmental problems caused by coal mining have received great attention. In particular, mining land subsidence caused damage to villages, buildings, farmland, etc., which seriously threatened the mining area's living environment and ecological environment. This study proposes a pressure-state-response concept model based on mining land subsidence to build an evaluation index system in coal mines. Based on this index system, given the uncertainty in the evaluation process, the cloud model is used to represent the index weight and comprehensive evaluation calculations, which fully consider the randomness and ambiguity in the evaluation process. The mining land subsidence of several mining areas in China was evaluated and classified into three grades (slight-medium-strong). The cloud model assessment results are compared with the result of the probability integration method and the actual situation. The assessment results of the cloud model are closer to the actual situation than the probability integration method. This shows that the established mining land subsidence evaluation method based on the cloud model in this study is reasonable and feasible. The mining width and height ratio, depth and height ratio, and coal seam dip angle affect mining land subsidence. Therefore, improving the mining method to deal with the goaf reasonably and optimizing the mining design to control the influence range of mining are essential measures to reduce mining land subsidence and protect the ecological environment of mining areas. [ABSTRACT FROM AUTHOR]

The Majiagou Bridge comprising four sub-bridges is adjacent to the Weiqiang coal mine, Yulin City, Shaanxi Province, China. The mining of the longwall panel No. 1307 may damage the Majiagou Bridge. In this study, we predicted the mining-induced bridge movements using the finite element method (FEM) to examine whether the progressive mining of the longwall panel will pose a negative impact on the Majiagou Bridge. We reconstructed detailed three-dimensional models of the four sub-bridges by considering the superstructures and substructures. The input mechanical properties of the strata are estimated by calibrating with available field monitoring data. Effect of traffic load on the bridge subsidence is also accounted. The numerical predictions are: (1) after the panel No. 1307 is mined, the maximum vertical and horizontal displacements of the four bridges are 61.2 mm and 84.8 mm respectively, which occur on the sub-bridge D that is closest to the longwall panel, (2) traffic load has much less pronounced effect on the Majiagou Bridge than that due to mining, and (3) the maximum tilt and horizontal strain of the sub-bridges are 3.42e−5 m/m and 2.19e−5 m/m, which occur on sub-bridge B and sub-bridge A, respectively. In terms of tilt, the Majiagou Bridge is safe whereas it is to be damaged in terms of horizontal movement that is more critical in causing structural damage. Therefore, we suggest that a reasonably wider protective coal pillar should be set if the panel No. 1307 is to be mined, to ensure the safety of the Majiagou Bridge. [ABSTRACT FROM AUTHOR]

Surface subsidence can cause both damage to infrastructure and a number of different environmental problems. These include surface water accumulations, loss of farmland, cracks and other damage to roads and bridges, and, in the most severe cases, the collapse of house and other buildings. Surface subsidence can be especially severe during and subsequent to coal mining. Gangue-cemented fill in goaf (GCFG) has been proposed as an effective measure to control surface subsidence during longwall coal mining. In this study, GCFG was used for an industrial-scale filling test at the 61,303 working face in the Huaheng Coal mine, China. To perform the filling test, a new GCFG storage and transport system and a system for mixing the cemented gangue were designed. The test showed that GCFG can effectively reduce the load on pillars, the amount of hydraulic pillar ram descent, and roof subsidence. This means that GCFG can effectively control the movement of the strata overlying the coal seam and therefore reduce or eliminate surface subsidence. Future research on GCFG technology should include the long-term strength and the rheological behavior of the cemented gangue. [ABSTRACT FROM AUTHOR]