Mining Deformation Research Articles

Experimental and numerical investigation on a novel support system for controlling roadway deformation in underground coal mines

AbstractRoadway stability in extremely soft coal mass is a typical challenge in deep underground mines, as the most widely adopted support structure such as rock bolting, compound support system normally fails. This paper proposed a novel prereinforcement method for coal roadway, that is, jet grouting (JG) technique, to improve the quality of surrounding soft coal mass and form a stable support structure namely jet grouted coalcrete. The field and laboratory tests were conducted for evaluating the applicability of JG and the mechanical parameters of coalcrete. A numerical model was verified by comparing the calculated results with field measurements. According to the confirmed model, three typical JG support schemes were performed to assess the roadway stability after JG. The results showed that the proposed JG schemes can reduce the deformation and failure zone of the roadway and optimize the stress states around the roadway. The mechanism related to these advantages was investigated. This study provides a promising idea for supporting soft coal roadway in deep underground coal mines, which can promote the JG application in the field.

Traffic infrastructure in mining areas (selected problems)

The article discusses the issues of safety of operation of road and rail transport infrastructure objects in mining areas. In particular, the fol-lowing issues were discussed: the general characteristics of the mining deformations of the rock mass and the terrain surface, the impact of continuous and discontinuous deformations on the safety of the opera-tion of land transport infrastructure facilities and reinforcements of land transport infrastructure structures in mining areas. Examples of land transport structure reinforcements situated within the reach of mining influences are given.

Design and monitoring of CPB replacement mining RSCP: a case study in China

ABSTRACT After the previous exploitation of the coal resources below villages, a large number of Residual Strip Coal Pillars (RSCP) have been left. How to mine the RSCP without obvious secondary mining deformation on the surface has become a new direction of green mining at present. In this paper, Cemented Paste Backfill (CPB) is designed to replace mining RSCP. Considering the pumpability and strength, orthogonal test is conducted to comprehensively analyze the variation trend of different indexes under different factor levels, and a reasonable proportion is obtained to ensure the safety and rationality of mining. Through a self-designed dynamic paste filling device, the similar simulation contrast test is carried out, the characteristics of mining failure are obtained under the filling mining. Through field measurement, it is found that the compression of the filling body and the overall deformation of the roadway are relatively small, the velocity of roadway roof and floor movement slightly change. Finally, main influencing factors and the specific proportion of the roof deformation are obtained through field measurement analysis. This paper can provide the theoretical basis and practical experience for similar mining of RSCP.

Using Phase Unwrapping Methods to Apply D-InSAR in Mining Areas

Phase unwrapping is one of the key processing steps of D-InSAR (Differential Interferometric Synthetic Aperture Radar), and its accuracy has a great impact on the accuracy of interferometric deformation results. Therefore, it is necessary to choose the proper phase unwrapping method for mining deformation monitoring with different coherence by the comparative study of different phase unwrapping methods, because the coherence is different for different mining areas. In this paper, 2 data sets of different coherence Sentinel-1A data in Xuangang mining areas were processed using 3 different D-InSAR unwrapping methods: Region Growing, Minimum Cost Flow, and Delaunay MCF by SARscape software. Through statistical analysis of phase unwrapping results and comparative analysis of the difference between the theoretical deformation value and the deformation value calculated by SARscape, the Delaunay MCF unwrapping method is found to be the best to monitor low-coherence mining areas under most conditions. However, the Minimum Cost Flow method is a better choice when the coherence of mining areas is high, and smoother and more continuous phase unwrapping results can be obtained by selecting a mining area with better coherence.

Impact of Mining Subsidence on Natural Gas Pipeline Failures

The main goal of the paper is to present the influence of ground deformations, caused by mining subsidence, on natural gas pipelines. There are also presented characteristic examples of the gas pipelines failures in mining areas in Poland. Failures of buried natural gas pipelines pose a threat to people and the environment due to gas leaks. The main reasons of the leaks are corrosion of steel pipelines, mechanical damage as a result of construction works and unsealing of joints as well as expansion joints. In mining areas, the gas pipelines are influenced by ground deformations. Mining extraction induces subsidence, horizontal displacements, horizontal strains and curvatures of the subsurface ground layer where natural gas pipelines are buried. The horizontal strains are of significant importance for the considered issue. The mining-induced ground deformations cause displacements of pipelines as well as additional longitudinal tensile and compression loads. The load values depend on the soil-pipe friction coefficient, pipeline depth and pipeline section length subjected to horizontal strains. The load conditions also change in the transverse direction of pipelines. In Polish mining areas distribution gas pipelines are constructed with steel and polyethylene pipes. Transmission gas pipelines are constructed with steel pipes. The steel gas pipelines usually are equipped with built-in expansion joints to protect them and to transmit ground deformations. The polyethylene gas pipelines are flexible and are able to transmit mining ground deformations but polyethylene pipes can be used up to 1,0 MPa nominal pressure in natural gas systems. Mining extraction causes additional failures of the gas pipelines despite their above mentioned capacities. The failures occur most frequently in the steel gas pipelines, particularly in old ones. The main causes of gas leaks are wall breaks, mostly near welded areas, wall buckling and sealant damage of expansion joints. Mining deformations can also induce the buckling of polyethylene pipelines. Therefore, in mining areas additional inspections of the natural gas network are needed to detect the leaks early.

Selected Bearing Problems of Old Railway Bridges Located On Mining Areas in Poland

In this article are discussed bearing problems of old railway bridges located on mining areas in Poland. The problem is important because the old railway bridges in the areas of active mining exploitation are still in use, but often lack of money for their replacement or major reconstruction. Railway traffic is still underway after these objects, but the requirements for increasing the speed of rolling stock are bumped up. The article applies to bridge objects, which have the static scheme of the freely supported beam, which is universally used, and it is a structural solution. The article describes how mining exploitation affects bridge bearings and the conditions that bearings should fulfil on mining areas. A short review of Polish technical solutions and Polish literature information’s on bearings of railway bridges in mining areas is made, it may be valuable for people dealing with similar problems in other countries. Attention is taken to the features that differ the bridge objects from cubature structures in the context of transferring mining influences, e.g. multi-solid of bridges and elevation of their main structural part (spans) above the ground. The general principles of ensuring kinematic freedom and selection of bearings are discussed. Typical damages and threats to the safety of the rail traffic (e.g. breaking the permanent bearing, blocking the bearing, cutting the head of the pillar) triggered by mining area deformations are pointed out. Author discusses the significant influence of bearings on the resistance of railway objects to mining deformations of the area. The article also draws attention to the necessity of frequent monitoring of bearing condition due to the possibility of sudden damage. Examples of Polish experiences are given, i.e. working SHM (Structural Health Monitoring) system is described. Safe maintenance of the object on the mining area requires a combination of knowledge from the bridge manager and mine and data from automatic monitoring systems, geodetic measurements, technical condition assessments - it indicates the need for proper organization of the process associated with acquisition, use and information flows, e.g. according to standards included in the BIM method (Building Information Modelling).

Introduction for the Special Issue on Beyond the Hypes of Geospatial Big Data: Theories, Methods, Analytics, and Applications

We live in the era of ‘Big Data.’ In particular, Geospatial data, whether captured through remote sensors (e.g. satellite imagery) or generated from large-scale simulations (e.g. climate change models) have always been significantly large in size. Over the last decade however, advances in instrumentation and computation has seen the volume, variety, velocity, and veracity of this data increase exponentially. Of the 2.5 quintillion (1018) bytes of data that are generated on a daily basis across the globe, a large portion (arguably as much as 80%) is found to be geo-referenced. Therefore, this special issue is dedicated to the innovative theories, methods, analytics, and applications of geospatial big data. A total of 37 manuscripts were submitted and 10 were selected based on a robust peer-reviewed process. The 10 articles are authored by researchers from seven research institutes and universities, and reflect state of the research developments and initiatives in the collection, processing, modeling, analysis as well as applications of geospatial big data and future directions. Specifically, topics across global navigation satellite systems (GNSS), geographic information system (GIS), remote sensing (RS), land-use planning, environmental sustainability, and mining deformation monitoring are included.

Study on Coupling Relationship Between Surrounding Rock Deformation and Support Parameters in Deep Roadway

Surrounding rock in deep mine will exhibit discontinuous large deformation characteristics under high geo-stress, so the rationality of the anchor-net support parameters will directly affect the tunnel support effect. In this paper, the relationship between wall rock around tunnel in deep mine deformation and support parameters of deep roadway is studied by FLAC numerical simulation. The travelling roadway of 11501 coal face in a mine is taken as the research background. Five bolt lengths (2.4m,2.6m,2.8m,3.0m and 3.2m) and 5 kinds of the inter-row spacion of anchor rod (0.6m×0.6m, 0.65m×0.65m and 0.7m×0.7m, 0.75m × 0.75m, 0.8m × 0.8m) are designed based on the initial support scheme of the tunnel. The effect of 25 combinations of bolting support are analyzed. After,6 kinds of anchor cable length schemes (5.5m,6m,6.5m,7m,7.5m,8m) are designed for research. Finally, the coupling relationship between the support parameters of the anchor (cable) and the deformation of the surrounding rock is obtained. The research results provide reference for the scientific design of the roadway support under similar conditions.

Study of Tunnel Damage Caused by Underground Mining Deformation: Calculation, Analysis, and Reinforcement

Bayueshan tunnel (BYS) is an important construction crossing over coal mine goaf. The underground mining subsidence has led the tunnel cracked seriously in three years after it was built. In order to evaluate the coal mine influence and future stability of the tunnels, probability integral method (PIM) was used to calculate the tunnel deformation. PIM is an experience function method based on random medium theory which is used widely in China. With the parameters analyzed, the tunnels’ subsidence was calculated. The results show that it can interpret the tunnel damage well, and the maximum normal strain positions fit the damaged tunnel positions well. It proved that PIM can be used to evaluate the tunnel’s radial deformation caused by underground coal excavation. In order to maintain tunnels to keep a long‐term stability, the future deformation was calculated in case the coal excavation continues. It shows that the tunnel would be cracked again if the excavation continued. Other reasons such as the old goaf deformation and water and vehicle dynamic load are also important reasons for the tunnels’ deformation. In order to keep traffic safety, it needs to reinforce the cracked foundation under the tunnel. Then, grouting injection was proposed to reduce the old goaf deformation under the tunnels. If the fracture zone under the tunnels disturbed by the dynamic traffic load, the old goaf will face a risk of sudden collapse. So, to ensure the grouting effect, the grouting depth should be deeper than the sum of traffic load influence depth and height of coal mine caved fissure zone. The grouting scope should keep all the crack rock area under the tunnel from being disturbed by the dynamic traffic load. This design can reduce the sudden collapse risk of the goaf and reduces the vehicles’ load disturbance on the cracked rock. The researched technology provides an engineering guidance to tunnel subsidence calculation, stability evaluation, and maintenance in complex geological and engineering situations.

Joint Probability Integral Method and TCPInSAR for Monitoring Mining Time-Series Deformation

Because of the high vegetation coverage, fast deformation in certain mine areas, some SAR interferograms are seriously incoherent. When using time-series synthetic aperture radar interferometry (InSAR) to monitor the surface movement basin of the mining area, there may be a certain period of missing deformation information, making the obtained surface time-series deformation incomplete. To this end, this paper proposes a way of using the results predicted by probability integral method (PIM) to replacing the monitoring results that cannot be obtained because of the seriously incoherent SAR interferograms; then, the monitoring results of the high-coherence SAR interferograms and the results predicted by PIM are used by the improved temporarily coherent point SAR interferometry (TCPInSAR) to invert the deformation, thereby obtaining a complete mining time-series deformation. The TCPInSAR using a linear model does not reflect the complex deformation characteristics of the mining area. So this paper focus on the characteristics of deformation of study area, the original linear model is changed to a polynomial model, which improves the applicability of TCPInSAR to monitoring mine deformation. Comparison between the experimental results and levelling shows that the root mean square error (RMSE) and the maximum deviation (MD) of the results obtained by combining the PIM with the improved TCPInSAR are 14.2 mm and 43.0 mm, respectively. Compared with the results obtained by combining the PIM with the TCPInSAR (RMSE = 16.2 mm, MD = 57.5 mm) and the results of using only the TCPInSAR (RMSE = 26.5 mm, MD = 88.4 mm), the monitoring accuracy is increased by 12.3% and 46.4%, respectively.

IDENTIFICATION AND MEASUREMENT OF DEFORMATION USING SENTINEL DATA AND PSINSAR TECHNIQUE IN COALMINES OF KORBA

Abstract. Natural Resources extraction for production of goods increases the stress on land and on the environment. Coal Mines are the primary source for energy production. This process increases the continuous deformation on land by disturbing equilibrium beneath the surface. Interferometry techniques have a capability to detect the minute deformation with millimetre precision on the ground using microwave SAR data. The study area covers the largest open cast coal mines of Asia. In this study for minute deformation identification, Persistent Scatterer Interferometry Synthetic Aperture Radar (PSInSAR) technique has been used. Research focuses on the application of PSInSAR technique for terrain deformation detection using 17 SAR scene of Korba, Chhattisgarh, India acquired by the Sentinel-1 satellite of European Space Agency. This technique is capable to monitor the minute deformation in the coal mines of Korba, Chhattisgarh, India. The results predicted that the area is deformed with the velocity up to 30 mm/year in the coal mines and surroundings areas. The PSInSAR technique with the Sentinel-1 data provides the proficient tool for deformation monitoring in coal mines of Korba.

High-Resolution Three-Dimensional Displacement Retrieval of Mining Areas From a Single SAR Amplitude Pair Using the SPIKE Algorithm

High-resolution three-dimensional (3-D) displacements of mining areas are crucial to assess mining-related geohazards and understand the mining deformation mechanism. In 2018, we proposed a cost-effective and robust method for retrieving mining-induced 3-D displacements from a single SAR amplitude pair (SAP) using offset tracking (OT) procedures. Hereafter, we refer to this method as the “alternative OT-SAP” (AOT-SAP) method. A key step in the AOT-SAP method is solving the 3-D surface displacements from the AOT-SAP-constructed linear system using routine lower–upper (LU) factorization. However, if the AOT-SAP method is used to retrieve high-resolution 3-D displacements, the dimension of the linear system becomes very large (in the order millions), and a high-end supercomputer is often needed to perform the LU-based solving procedure. This significantly narrows the practical application of the AOT-SAP method, considering the limited availability of supercomputers. In this paper, owing to the banded nature of the AOT-SAP-constructed linear system, we introduce the SPIKE algorithm as an alternative to LU factorization to solve high-resolution mining-induced 3-D displacements. The SPIKE algorithm is a divide-and-conquer direct solver of a large banded system, which can parallelly or sequentially solve a large banded linear system, with a much smaller memory requirement and a shorter time cost than LU factorization. This allows us to retrieve the high-resolution 3-D mining-induced displacements with the AOT-SAP method on either a supercomputer or a standard personal computer. Finally, the accuracy of the retrieved 3-D displacements and the efficiency improvement of the SPIKE algorithm were tested using both simulation analysis and a real dataset.

Monitoring of 3D large surface deformation in coal mines through the integration of synthetic aperture radar pixel offset tracking and probability integration function model

Monitoring of 3D large surface deformation in coal mines through the integration of synthetic aperture radar pixel offset tracking and probability integration function model

Decision Fusion of D-InSAR and Pixel Offset Tracking for Coal Mining Deformation Monitoring

Ground surface subsidence is a universal phenomenon in coal mining areas which can cause serious damage to the surrounding environment. In this paper, we consider the use of differential interferometric synthetic aperture radar (D-InSAR), multi-temporal InSAR (MT-InSAR), and the pixel offset tracking technique to monitor the surface deformation of a coal mining area. In this study, we use the two-pass D-InSAR method to generate 19 interferometric image pairs from 20 TerraSAR-X SpotLight images. The results show that D-InSAR can be used to obtain high accuracy surface deformation in the mining areas where there is no high gradient deformation, and the pixel offset tracking method offers advantages in those areas where high gradient deformation is found, but its performance is not stable. This means that the unilateral use of these technologies cannot obtain reliable subsidence information in mining areas. Therefore, it is essential to find a new way to integrate the respective advantages of these different methods. In this paper, a new fusion method combining the D-InSAR result with the offset tracking result based on a spatial decorrelation distribution map is proposed to obtain the subsidence results in a mining area. To ensure the reliability of the results, a decision rule is proposed for the spatial decorrelation distribution map, which is generated manually by union analysis in ArcGIS. In the experiments, the mean absolute error of the fusion result is 0.0748 m, while that of D-InSAR is 0.1890 m, and that of offset tracking is 0.1358 m. It is therefore clear that the proposed fusion method is more reliable and more accurate than the use of individual methods, and it may be able to serve as a reference in mining subsidence monitoring.

An Alternative Method for Estimating 3-D Large Displacements of Mining Areas from a Single SAR Amplitude Pair Using Offset Tracking

Measuring 3-D mining-induced displacements is essential to understand mining deformation mechanisms and assess mining-related geohazards. In our previous work, we proposed a method for estimating 3-D mining-induced large displacements with the surface deformation along the radar line-of-sight (LOS) direction derived from a single amplitude pair (SAP) of synthetic aperture radar (SAR) using the offset tracking (OT) procedure (hereafter referred to as OT-SAP). The OT-SAP method effectively reduces the strict requirements on SAR data of the previous OT-based methods for 3-D mining-induced displacement retrieval. However, OT-SAP is not robust to errors in the LOS deformation, due to the lack of redundant observations. In this paper, we present an alternative approach (hereafter called AOT-SAP) to OT-SAP. The AOT-SAP method involves estimating the 3-D mining-induced large displacements with OT-derived 2-D deformation observations along the LOS and azimuth directions from an SAP of SAR, instead of just the LOS deformation in the OT-SAP method. Consequently, more redundant observations are incorporated in the AOT-SAP method compared with the previous OT-SAP method. The theoretical analysis and experiments based on both simulated and real data sets suggest that AOT-SAP can effectively improve the accuracies of the estimated 3-D displacements compared with the OT-SAP-estimated ones.

An InSAR-Based Temporal Probability Integral Method and its Application for Predicting Mining-Induced Dynamic Deformations and Assessing Progressive Damage to Surface Buildings

Surface deformations caused by underground mining are time-dependent and highly nonlinear, and can result in progressive damage to surface structures during underground extraction. However, the previous methods based on the interferometric synthetic aperture radar (InSAR) technique are generally incapable of accurately predicting the mining-induced dynamic deformations occurring during the entire period of underground extraction, due to the inaccurate model parameters inverted under the condition of ignoring the horizontal motions of the InSAR-derived measurements and the model errors for predicting dynamic deformations. Consequently, the risk of mining-related structural damage cannot be reliably assessed based on the deformations predicted by the previous InSAR-based methods. To overcome this limitation, we propose a novel method that combines InSAR with a new mining deformation model: the temporal probability integral method (TPIM). Theoretically, the integration of InSAR and TPIM allows the InSAR-TPIM to accurately predict mining-induced dynamic deformations occurring in the entire period of underground extraction. Furthermore, InSAR-TPIM can reliably assess mining-related progressive structural damage based on the predicted dynamic deformations. However, these advantages cannot be achieved by the previous InSAR-based methods. The Qianyingzi coal mining area of China is selected to test the proposed method. The results demonstrate that the accuracies of the predicted dynamic deformations are about 0.030 and 0.041 m in the horizontal and vertical directions, respectively, which can meet the accuracy requirements of mining-induced dynamic deformation prediction. Furthermore, the comparison between the potential structural damage predicted by the proposed method and the previous InSAR-based methods indicates that the damage risks of around 131 buildings (43.9% of the 298 buildings) are underestimated by the previous InSAR-based method.

A Case Study on Offshore Platform Deformation Monitoring by using InSAR

The Interferometric Synthetic Aperture Radar (InSAR) technique is well established technique for onshore applications such as landslide, mining, volcano, urban and dam deformation monitoring. However, the ability of the InSAR technique for the offshore application particularly on the oil platform deformation monitoring is still a pending question. Therefore, a study needs to be conducted in order to assess the feasibility of the InSAR technique for monitoring the deformation of offshore platform. In this study, an advanced InSAR technique called Stanford Method of Persistent Scatterer (StaMPS) was utilized to process a stack of TerraSAR-X data. A mask has been developed as an additional module in the StaMPS to remove the noise on the ocean and relax the assigned condition imposed on the processing parameters. The results show that the number of persistent scatterer (PS) points on the offshore platform increased from 15 to 22 points and a smoother pattern of the velocity estimation could be seen when masking was applied to identify the deformation. Furthermore, some limitations and possible solutions of the PSI technique on the offshore platform application are summarized in this paper to guide future users on this application.

Enhancement of the Walbrzych Hard Coal Mines Geographic Information System for its application in studies of mining deformations

Enhancement of the Walbrzych Hard Coal Mines Geographic Information System for its application in studies of mining deformations

Enhancement of the Walbrzych Hard Coal Mines Geographic Information System for its application in studies of mining deformations

Geographic information systems (GIS) have been increasingly used in augmenting studies of mining and post-mining areas such as surface deformation analyses, risk assessment associated with old mining sites, identification of old mining sites and other. Up-to-date and complete geodatabase is an indispensable element of any geoinformation system facilitating such geospatial analyses. In this paper the process of verification and integration of Walbrzych Hard Coal Mines geodatabase and project of enhancing the Deformation Information System for these mines with web map application of underground workings and query tools developed with free and open source software (FOSS) have been described. The interactive map allows users to interact and obtain precise information on location and characteristics of underground mining and the query tools streamline pre-processing operations necessary for geospatial analyses.

Influence of mining operations on road pavement and sewer system – selected case studies

Abstract Underground mining operations cause surface deformations which influence structures. A particular group of structures which are susceptible to the influence of mining operations are so-called “linear objects”, whose characteristic parameter is their length. Linear objects consist of, for example: roads, rails, sewers and water supply systems. Changes in the length of measurement bases (deformations) accompanying mining deformations and changes in ordinates, including the difference in subsidence (inclination), to a large extent determine the utility properties of the structures and create a significant nuisance when using them and even causing them to fail completely. It is worth emphasising that when applying proper preventive measures once continuous deformations have begun, it is possible to use the objects for a relatively long period of time. In the case of discontinuous deformations, the utility properties are significantly deteriorated, which most often leads to failures, significantly hastening the decision to conduct repair works. This article presents selected cases of the continuous influence of mining operations on a sewer system and of discontinuous deformations on a road pavement. The presented research and in situ observations may be useful in assessing, designing or re-building such structures in areas where mining operations are planned.