Mining-induced Surface Subsidence Research Articles

Prediction model with multi-point relationship fusion via graph convolutional network: A case study on mining-induced surface subsidence.

Accurate prediction of surface subsidence is of significance for analyzing the pattern of mining-induced surface subsidence, and for mining under buildings, railways, and water bodies. To address the problem that the existing prediction models ignore the correlation between subsidence points, resulting in large prediction errors, a Multi-point Relationship Fusion prediction model based on Graph Convolutional Networks (MRF-GCN) for mining-induced subsidence was proposed. Taking the surface subsidence in 82/83 mining area of Yuandian No. 2 Mine in Anhui Province in eastern China as an example, the surface deformation data obtained from 250 InSAR images captured by Sentinel-1A satellite from 2018 to 2022, combined with GNSS observation data, were used for modeling. The deformation pattern of each single observation point was obtained by feeding their deformation observation data into the LSTM encoder, after that, the relationship graph was created based on the correlation between points in the observation network and MRF-GCN was established. Then the prediction results came out through a nonlinear activation function of neural network. The research shows that the R2R2 value of MRF-GCN model was 0.865 0, much larger than that of Long-Short Term Memory (LSTM) and other conventional models, while mean square error (MSE) of MRF-GCN model was 1.59 899, much smaller than that of LSTM and other conventional models. Therefore, the MRF-GCN model has better prediction accuracy than other models and can be applied to predicting surface subsidence in large areas.

Parameter Acquisition Study of Mining-Induced Surface Subsidence Probability Integral Method Based on RF-AGA-ENN Model

The mining of underground coal resources can trigger geological hazards such as subsidence basins, cave-in pits, and step cracks. In China, the probability integral method (PIM), the most popular method for predicting surface movement deformation caused by coal resource mining, has a prediction accuracy that is mainly influenced by both the measurement data (i.e., quantity and quality) from ground movement observatories and the parameter inversion method. To obtain more accurate PIM parameters in the absence of observational data, we propose a combined machine learning model (RF-AGA-ENN)—random forest (RF) extracts the best combination of features as the input layer of Elman neural network (ENN); ant colony algorithm (ACO) and genetic algorithm (GA) are combined (called AGA) for the weights and thresholds of ENN optimization. The results of the study show that (1) the RF-AGA-ENN model is used to obtain PIM values with MAXRE values between 1.94% and 9.18%, AVERY values between 0.98% and 3.98%, and RMSE values between 0.0050 and 0.9632. (2) Compared with the PIM parameters obtained from BP neural network, RF-ENN, RF-ACO-ENN, and RF-GA-ENN models, the PIM parameters obtained from the RF-AGA-ENN model have better stability and accuracy. (3) According to the PIM parameters obtained by the RF-AGA-ENN model, the predicted and measured values of surface settlement at the 11111 working face have a high degree of agreement. In summary, the RF-AGA-ENN model to obtain the PIM parameters has good application value.

Normality Test for Influence Function of Mining Surface Subsidence Based on Network Observation Station

Coal is the primary energy source in China, while underground mining is the mainstream way of coal mining. By triggering surface movement and deformation, underground mining can cause damage to arable land, buildings, roads, and so on, which is detrimental to the ecological environment in the mining area. In order to assess the severity of damage caused by this to the ground buildings and ecological environment in the mining area, it is necessary to predict mining-induced surface subsidence before the mining activities are carried out. Currently, the most used prediction method is the Probability Integral Method. It is based on probabilistic theory to mathematically demonstrate that the surface downwelling caused by underground extraction conforms to normal distribution. However, there is a lack of validation with measured subsidence basin data. Since the 1960s, China has been paying increased attention to the study of mining subsidence. However, there are still few network stations built across China to monitor subsidence basin. Herein, SPSS software is applied to re-analyze these valuable historical data. By analyzing the observation results and comparing them with the calculation results as obtained by using the probability integral method, it can be found out that the surface subsidence in the center of the subsidence basin conforms to normal distribution, not the subsidence at the edge of the subsidence basin. Therefore, it is inevitable for errors to occur at the edge of the subsidence basin when the normal distribution function is used as the mining influence function to calculate the surface subsidence. This conclusion is expected to provide practical reference for the prediction of surface subsidence in coal mines, and this experience can be extended to the mining of other solid minerals.

Calculation of Subsidence due to Longwall Mining with Overburden Grouting and Its Application

This paper presents a prediction method of mining-induced surface subsidence due to longwall mining with overburden grouting, which has been proven an effective method to mitigate the overburden failure. This paper proposes a partial overburden grouting (POG) mining method based on surface subsidence basin inversion and innovative longwall panel layout to mitigate overburden failure and subsidence. A prediction model of surface subsidence with overburden grouting, namely, overburden grouting equivalent calculation model (OGECM), is proposed. In this study, an engineering design process and method of POG was established, the strike and dip excavation length and grouting quantity combined as critical indicators for determining the key parameter in surface basin control. In applications at the field grouting test, the surface subsidence characteristics of POG on the side of the opening line of longwall panel were investigated through surface observation station and estimated surface subsidence reduction ratio based on OGECM with grouting compared with those without. The field measurement validated the new subsidence calculation method. POG technology applied to subsidence control has effectiveness in controlling the surface subsidence to less engineering cost but expanding the applications.

A geometrically and locally adaptive remeshing method for finite difference modeling of mining-induced surface subsidence

Surface subsidence induced by underground mining is a typical serious geohazard. Numerical approaches such as the discrete element method (DEM) and finite difference method (FDM) have been widely used to model and analyze mining-induced surface subsidence. However, the DEM is typically computationally expensive, and is not capable of analyzing large-scale problems, while the mesh distortion may occur in the FDM modeling of largely deformed surface subsidence. To address the above problems, this paper presents a geometrically and locally adaptive remeshing method for the FDM modeling of largely deformed surface subsidence induced by underground mining. The essential ideas behind the proposed method are as follows: (i) Geometrical features of elements (i.e. the mesh quality), rather than the calculation errors, are employed as the indicator for determining whether to conduct the remeshing; and (ii) Distorted meshes with multiple attributes, rather than those with only a single attribute, are locally regenerated. In the proposed method, the distorted meshes are first adaptively determined based on the mesh quality, and then removed from the original mesh model. The tetrahedral mesh in the distorted area is first regenerated, and then the physical field variables of old mesh are transferred to the new mesh. The numerical calculation process recovers when finishing the regeneration and transformation. To verify the effectiveness of the proposed method, the surface deformation of the Yanqianshan iron mine, Liaoning Province, China, is numerically investigated by utilizing the proposed method, and compared with the numerical results of the DEM modeling. Moreover, the proposed method is applied to predicting the surface subsidence in Anjialing No. 1 Underground Mine, Shanxi Province, China.

A Vertical Joint Spacing Calculation Method for UDEC Modeling of Large-Scale Strata and Its Influence on Mining-Induced Surface Subsidence

While universal discrete element code (UDEC) is widely used for understanding the mechanism of large-scale strata movement and the effects of mining subsidence on the environment, the fundamental knowledge of how to set vertical joint spacing (VJS) in UDEC is still not fully understood. To address the knowledge gap, we first present a novel VJS calculation method, then conduct UDEC experiments, and finally compare the predictions of UDEC models with field subsidence observation. The results suggest the following: (1) when compared to the conventional VJS setting (1× to 3× bed thickness), the maximum surface subsidence (MSS) prediction via UDEC models based on our proposed VJS setting method is closer to field observation; (2) a smaller but varying VJS setting can also have the effect of a larger VJS setting; and (3) with the increase in VJS, MSS first drops, then rises, and reaches the minimum when VJS is set at approximately 7× bed thickness. This paper provides an explanation of the VJS setting in UDEC and establishes a bridge between the KS theory and VJS, which is helpful for the sustainable development of such an UDEC modeling strategy and for a better understanding of the influences of mining subsidence on the environment in mining-affected areas.

Investigating mining-induced surface subsidence and potential damages based on SBAS-InSAR monitoring and GIS techniques: a case study

Investigating mining-induced surface subsidence and potential damages based on SBAS-InSAR monitoring and GIS techniques: a case study

Cylindrical Caved Space Stability Analysis for Extension Prediction of Mining-Induced Surface Subsidence

Subsequent extension of surface subsidence after vertical caving leads to large-scale surface destruction, as well as associated geological hazards. The extension prediction for cylindrical caved space, which appears circular surface subsidence, is still an intractable issue, due to the absence of robust models. To fill such a research gap, this paper provides an analytical model for the depth and orientation where the shear failure of isotropic rocks around the caved space is firstly observed. The anisotropy of surrounding rocks is further involved to enable this model to analyze the slip failure along discontinuities in anisotropic stress state. The prediction for the extension of the surface subsidence in Xiaowanggou iron mine is conducted, and the comparison between the prediction and the observation in satellite images demonstrates the validity of the proposed model. Even though this model cannot provide a definite boundary after extension, the prediction for the orientation surface subsidence extends to contribute to mitigating the effect of geological hazards. Another contribution of this work is to provide guidance to mitigate the impact of surface subsidence on safety and environment, such as filling the interspace between large-sized caved rocks by dumping small-sized waste rocks or backfilling the caved space with waste rocks.

Strategies for surface crown pillar design using numerical modelling – A case study

The extraction of shallow ore deposits using underground mining methods rather than open pit mining is not uncommon nowadays, especially with the increased environmental constraints. Such scenario results in the creation of a surface crown pillar - the rock cover consisting of ore rocks that separate the uppermost stopes from the overlying surface. Although the problem of surface crown pillar stability has been researched for more than 30 years, the design guidelines are still limited. This is largely because of the wide variety and complexity of site-specific conditions. Thus, empirical and analytical methods are only used for preliminary design and more comprehensive methods such as numerical modelling must be adopted for the final design. This paper investigates strategies for the design of a surface crown pillar at a gold mining operation having a shallow, steeply dipping orebody that extends underneath an existing tailings storage facility. The orebody is in the vicinity of two regional faults. In this study, numerical modelling approaches are developed using the finite difference code FLAC3D 7.0. Critical factors such as in-situ stress regime, major geological structures, mining sequences, slanted surface topography and surcharge are considered. A model parametric study is carried out to investigate the effect of fault properties and horizontal stress ratios on surface crown pillar stability. Mining-induced surface subsidence is then analyzed to shed light on the anticipated maximum differential settlement and distortion developed in the tailings dam foundation as a result of the mining activities. Predicted differential settlement results could serve as another criterion for crown pillar sizing from the perspective of overlying infrastructure stability. The reactivation of two nearby faults due to mining activities is also explored. It appears that larger shear displacements occur on the fault that is parallel to the orebody strike compared to the cross fault.

Coal Mining Deformation Monitoring Using SBAS-InSAR and Offset Tracking: A Case Study of Yu County, China

Ground deformation caused by underground coal mining has a large subsidence gradient and high nonlinearity and may cause continuous destruction to the surface structure after mining. A synthetic aperture radar interferometry (InSAR) is a powerful method for measuring and reconstructing the ground displacement. In this article, a total of 19 descending orbit X-band TerraSAR-X and 16 ascending orbit C-band Sentinel-1 images were integrated to monitor the ground displacement of a coal mining area in Yu County (Hebei Province, China) using a small baseline subset (SBAS-InSAR) algorithm. We found that the SBAS-InSAR technology can obtain reliable results in regions without a high gradient deformation by combining the deformation rates derived from both the TerraSAR-X and Sentinel-1 datasets. The maximum subsidence rate was approximately 125 mm/y between 17 June 2015 and 07 January 2016. In the case of large-gradient deformation, it is indeed difficult to obtain the mining-induced surface subsidence information accurately using the conventional multitemporal (MT-InSAR) techniques owing to the limitations of the SAR wavelength. In response to this problem, a new decision-making fusion method based on SBAS-InSAR and offset tracking was developed to monitor the large-gradient settlement in mining areas. The results show that the method developed compensates for the shortcomings of the traditional MT-InSAR technologies in the field of large-gradient deformation and obtains reliable results.

Control Technology of Surface Movement Scope with Directional Hydraulic Fracturing Technology in Longwall Mining: A Case Study

Mining-induced surface subsidence causes a series of environmental hazards and social problems, including farmland destruction, waterlogging and building damage in the subsidence area. To reduce mining damages, an innovative method of controlling the surface movement scope via artificial weak planes generated by hydraulic fracturing technology was proposed in this paper. Numerical models were built to analyze the influence of weak planes with different heights and dips on the overlying strata movement. The numerical simulation results showed that the weak planes structure cut off the development of the overlying strata displacement to the surface and affected the surface movement scope. When the weak planes’ dips were bigger than the angle of critical deformation, with the increase of the weak planes’ heights (0–120 m) the advance angle of influence changed from 53.61° to 59.15°, and the advance distance of influence changed from 173.31 m to 140.27 m which decreased by 30.04 m. In applications at Sihe coal mine in China, directional hydraulic fracturing technology was used in panel 5304 to form artificial weak planes in overlying strata. The measured surface subsidence and deformation value met the numerical simulation results and the mining-induced surface movement scope reduced. Moreover, no damage occurred to the surface buildings which were predicted to be in the affected area after extraction. This technology provided a new method to protect the surface structures from damages and had great benefits for the sustainable development of coal mines.

Environmentally sustainable mining: a case study on surface subsidence control of grouting into overburden

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.

Research on probability integration parameter inversion of mining-induced surface subsidence based on quantum annealing

Probability integral method is an official prediction method for mining subsidence in China. However, how to obtain the probability integral method parameters based on the measured data is the premise of realizing the accurate prediction of the probability integral method. Simulated annealing (SA) is an effective nonlinear optimization algorithm that has recently been introduced into the mining subsidence field to obtain the parameters of the probability integration method. To solve the problems of slow convergence speed and easily falling into the local optimal solution in the method of parameters inversion in probability integral method based on SA (MPIPIMSA), the method of parameters inversion in probability integral method based on quantum annealing (MPIPIMQA) is proposed by combining the quantum fluctuation mechanism and simulated annealing theory. The simulation experimental results show that MPIPIMQA is superior to MPIPIMSA in the accuracy and stability of parameters, and MPIPIMQA has a stronger anti-interference ability for local losing observation points, random errors and gross errors in observation data. Finally, the parameters of probability integral method for the 1414(1) working face of the Guqiao Coal Mine in Huainan mining area were obtained by using MPIPIMQA, namely, q = 0.9916, tanβ = 1.9277, b = 0.4190, θ = 84.3381, Su = − 7.3715, Sd = − 14.7126, Sl = 59.0695, and Sr = 32.6381, and the fitting error is 106.8863 mm. The research results have important reference values for accurate inversion of probability integral parameters.

High-grade highways deformation and failure laws in mining area – a case in Nantun Coal Mine, China

ABSTRACTHigh-grade highways constitute an important transportation infrastructure in coal mine areas in China. The surface subsidence caused by coal mining under high-grade highways poses a serious threat to the safety of high-grade highways. It is imperative to study the influence of mining-induced surface subsidence on high-grade highways. Zouji high-grade highways connect Zoucheng city and Jining city and pass over Nantun Coal Mine. Hence, coal resource exploitation in Nantun Coal Mine negatively affects high-grade highways. The 7328 working face belongs to the upper layers of No. 3 coal of Nantun Coal Mine. A field survey of deformation monitoring points above No. 7328 working face and a field investigation of high-grade highways damage area are performed to examine the subsidence relationship between high-grade highways pavement and surface, high-grade highways deformation and failure characteristics. The results are as follows: (1) the pavement subsidence is essentially consistent with the surface subsidence. When the pavement produces an uplift, the pavement subsidence is lower than surface subsidence. (2) Due to the discontinuous deformation of uplifts and cracks, the inclination curves exhibit obvious fluctuations. (3) The pavement cracks occur in the tensile area. The generation and development of pavement cracks mainly occur prior to the working face advances under the high-grade highways. Advances in working face increases the surface movement and deformation although the cracks width exhibits only a slight change. (4) The pavement uplifts occur in the compression deformation zone. The measured uplift height is between 5 and 15 cm, the length is between 5 and 12 m and the width is between 2 and 9 m. The horizontal profile of uplift generally corresponds to a long and narrow oval. (5) Given a strong stiffness and anti-deformation ability, the kerb also experiences compression failure within 24 h, and this mainly includes folding fracture or comminuted fracture. It is expected that the results of the study can guide coal exploitation under Zouji high-grade highways and provide an experimental reference for coal exploitation under high-grade highways in other mining areas.

Prediction of mining-induced surface subsidence and ground movements at a Canadian diamond mine using an elastoplastic finite element model

A full three dimensional elastoplastic finite element model of Diavik Diamond Mine is developed to predict surface-induced ground movement due to underground blasthole stoping activities. A mesh convergence study has been conducted to reach to an optimum meshing scenario when further mesh refinements produce a negligible change in the results. This way the calculation cost and time has been managed successfully. Furthermore, sequences of the excavation/backfilling in the model are defined according to the mine production plan; however, some simplifications in the shape of the stopes have been made. Consequently, the developed finite element model simulates the complete stress-strain path through the entire excavation and backfilling simulation steps in full three dimensional space. The model is calibrated using two extensometers installed on the back of two secondary undercut drifts in one of the Kimberlite pipes. The results of the calibrated model are validated using pit surface prism monitoring system data. The average relative error between the measured data and FE model predictions is 7.95%. It is shown that the numerical predictions of the mining-induced surface subsidence, due to the blasthole stoping mining method, matched well with the Gaussian distribution. A significant increase, approximately by 44%, to the amount of the induced settlements on the surface occurred as the mining activities reaches near surface ground levels. Finally, the comparison between the predicted results of the finite element model and monitoring data showed that the predictive capacity of the numerical model is a valuable tool for stability and design analysis of underground mines.

Surface Movement Characteristics of Super Thick Coal Seam Under Repeat Mining

In this paper, taking the Tiger bench mine special thick coal seam mechanized caving mining as an engineering instance, through numerical simulation research, we systematically analyzed how thick coal seam mechanized caving mining induced surface subsidence basin magnitude and scope, and researched impacted characteristics and destructive effect of the surface deformation of large fault zone.

Surface subsidence control during bag filling mining of super high-water content material in the Handan mining area

This paper focuses on the analysis of the overburden strata control mechanisms in stopes utilising bag filling mining super high-water content material. The factors affecting the mining-induced surface subsidence were determined, and control methods were applied to improve the filling rates of the working faces. The effects of filling rate changes on overburden failure and surface subsidence were investigated quantitatively using the field data. The results indicate that high filling rates and small changes could improve surface subsidence control. When the filling rate exceeded 86%, a 1% increase in the filling rate could decrease the average surface subsidence speed and distance by 5% and 7%, respectively. According to the current geological conditions of the Handan mining area, surface subsidence was observed as 260 mm at a 92% filling rate. Thus, these surface movements and damage indicators could be used to meet the requirements of I-level building codes and adequately control surface subsidence. [Received: July 28, 2015; Accepted: January 14, 2016]

Relation between benchmark displacement velocity and seismic activity caused by underground longwall exploitation

The following paper addresses the problem of mining-induced surface subsidence by giving consideration to the aspect of displacement velocity and its relation to seismic activities recorded in the area of benchmarks. A series of geodetic measurements were carried out in order to develop an accurate description of the deformation process. The mathematical model of a benchmark displacement process was worked out to estimate the maximum deformation velocity and the time of maximum velocity occurrence. The comparison between the measured and calculated data was presented. The displacement velocity value was compared to the seismic activity recorded during the exploitation period. Four cases were thoroughly investigated as they represent types of relation between the seismic activity and the deformation velocity.

Deficiencies in 2D Simulation: A Comparative Study of 2D Versus 3D Simulation of Multi-seam Longwall Mining

The reliable prediction and management of mining-induced surface subsidence is one of the environmentally challenging issues for the coal mining industry. Because coal mining companies operate under strict environmental accountability, the absence of robust and reliable analysis tools may significantly affect the industry’s ability to gain approval and licenses when significant surface subsidence issues are involved. This issue becomes even more critical in multi-seam mining conditions, where high-stress concentration and large amounts of surface subsidence are expected to generate during multi-seam mining, hence could affect the feasibility and safety of all seams being mined. To obtain mining approval, it is, therefore, imperative to understand the geomechanical effect of mining in one seam on the mining of the underlying/overlying seams, and to accurately predict the magnitude and profile of surface subsidence. Various computer programs using empirical or numerical approaches have been developed to estimate the stresses at pillars and coal seams during multi-seam mining (Bigby et al. 2007; Ellenberger et al. 2003; Mark et al. 2007; SCT 2010; Sears and Heasley 2013). However, empirical-based models have severe limitations, which often make them inapplicable for assessing the feasibility of multi-seam mining at green field sites. Instead, numerical simulations are widely employed for this purpose. Due to the complexity of the problems and the computational times, researchers and engineers generally resort to twodimensional (2D) simulations. The present study assesses the performance of 2D and 3D numerical simulations and presents comparisons of subsidence profiles and stresses in pillars obtained during multi-seam mining. We modeled two different seams, each with four mining panels, using an in-house, 3D, finite element code called COSFLOW (Adhikary et al. 1996; Adhikary and Guo 2002). A unique feature of COSFLOW is the incorporation of Cosserat continuum theory in its formulation (Cosserat and Cosserat 1909). In the Cosserat model, interlayer interfaces (i.e., joints, bedding planes) are considered to be smeared across the mass. In other words, the effects of the interfaces are incorporated implicitly in the choice of stress–strain model formulation. The Cosserat model incorporates the bending rigidity of individual layers in its formulation, unlike other conventional implicit models. COSFLOW produced very accurate results when simulating surface subsidence due to longwall mining at Appin Colliery in New South Wales in Australia (Guo et al. 2004).

Surface subsidence prediction for the WUTONG mine using a 3-D finite difference method

WUTONG coal mine is adjacent to an auxiliary dam of the Yuecheng Reservoir. In this paper, mininginduced surface subsidence prediction is conducted by means of the finite difference method (FDM) to judge whether the extraction of the coal seam will have a negative impact on the dam. First, the initial values of the rock mass mechanical parameters are estimated using the available literature that relates intact rock and discontinuity properties to rock mass parameters. Then, based on available surface subsidence monitoring data on WUTONG’s mined areas, the main mechanical parameters of coal and rock masses are determined by a back analysis procedure that combines an experimental design technique with numerical simulations. Finally, the surface subsidence results in the mining area are numerically predicted for four different mining scenarios (S1 through S4). Scenario S3 emerged as the best choice of these four scenarios. The predictions are: (1) the maximum surface subsidence within the mining area is 2.14 m, with the maximum settlement point located in the mid-west area of the coalfield, and (2) the nearest distance from the boundary of the surface movement area to the edge of the dam foundation is 35 m. Therefore, mining the coal seam will not cause damage to the dam.