Influence of Key Strata on the Evolution Law of Mining-Induced Stress in the Working Face under Deep and Large-Scale Mining

Abstract

When there are multiple key strata in the overburden of a deep coal seam and the surface subsidence coefficient after mining is small, this indicates that the overlying key strata fail to break completely after mining. On this occasion, stress is easily concentrated in the working face, which in turn leads to the occurrence of dynamic disasters such as rock bursts. This study adopted a comprehensive analysis method of field monitoring and numerical simulations to explore the influence of the key stratum on the evolution law of mining-induced stress in the working face. A distributed optical fiber sensor (DOFS) and a surface subsidence GNSS monitoring system were arranged inside and at the mouth of the ground observation borehole, respectively. According to the monitoring results of strain obtained from the DOFS, the height of the broken stratum inside the overlying strata was obtained and according to the monitoring results of surface subsidence, the surface subsidence coefficient was proven to be less than 0.1, indicating that the high key stratum is not broken completely, but enters a state of bending subsidence instead. In order to reveal the influence of the key stratum on the mining-induced stress of the working face, two 3DEC numerical models with and without the key stratum were established for a comparative analysis. As the numerical simulation results show, when there are multiple key strata in the overburden, the stress influence range and the stress concentration coefficient of the coal seam after mining are relatively large. The study revealed the working mechanism of rock burst accidents after large-scale mining and predicted the potential area with a rock burst risk after mining of the working face, which was verified by field investigations. The research results are of great guiding significance for the identification of the working mechanism of rock bursts in deep mining condition and for their prevention and control.

Study on the Spatiotemporal Dynamic Evolution Law of a Deep Thick Hard Roof and Coal Seam

“…These techniques are also gradually being applied to solve engineering geological problems. The mutual verification between the results of numerical simulation calculations, experimental findings, and engineering practice has expanded the scope of problem solving in engineering geology, deepened the exploration of research topics, and effectively advanced the quantitative advancement of the engineering geological discipline [24][25][26]. Therefore, during the mining process of deep, thick, and hard roof working faces, this research employs FLAC3D V4.0 numerical simulation software to simulate and examine the dynamic evolution process of the stress field, displacement field, energy field, and plastic zone of the coal seam and overlaying strata.…”

Research on Similarity Simulation Experiment of Mine Pressure Appearance in Surface Gully Working Face Based on BOTDA

“…Moreover, the monitoring instruments mostly perform point monitoring, the layout of measuring points is cumbersome, and the sensitivity is low. With the development of optical fiber sensing technology, distributed optical fiber technology based on BOTDA is widely used in similar physical model experiments for the continuous monitoring of overlying rock deformation due to their advantages of high precision, high sensitivity, high reliability, simple layout, and distributed monitoring [14][15][16]. Chai et al [17] proposed a new method to monitor the deformation of key layers of the overburden and, thus, characterize the pressure in the extraction zone using BOTDA technology.…”

“…The distributed optical fiber used in the experiment is a 2.0 mm diameter single-mode polyurethane tight sleeve optical The BOTDA monitoring system used in the experiment is the NBX-6055 Brillouin Time Domain Stress Analyzer produced by Neubrex Company, Kobe, Japan. Its monitoring parameters are set as a 5.0 cm spatial resolution, a 1.0 cm sampling interval, and 2 16 averaging times. The output probe power is 0 dBm, the output pump power is 30 dBm, and the frequency range is set from 10.60 GHz to 11.00 GHz.…”

Shaft Wall Damage to High-Depth Inclined Ore Passes under Impact Wear Behavior

“…Deep mining is a future development trend, and kilometer-deep metal mines are becoming increasingly common [1][2][3][4]. High-depth inclined ore passes (depth exceeding 100 m) are regarded as important projects for the low-cost downward transportation of deep mining and they are the key connection between the middle production levels and haulage ways in underground mines [5][6][7]. Due to the different geological environments, complex mining conditions, and improper structural parameters of ore passes (i.e., the depth and dip angle of ore passes), the impact wear effect of extracted ore blocks can cause the shaft wall to sag and wear, leading to shaft wall damage and collapse accidents.…”