Abstract
Microseismic monitoring technology was used to study the real-time evolution of rock mass damage generated by a working face as it approached a fault in Dongjiahe Coal Mine. The influence of vertical zoning of overlying strata on damage at the fault was analyzed. Numerical simulation using finite element method based on meso-statistical damage theory was used to investigate the nonlinear and nonuniform failure behaviour of the rock mass near the fault. The response of the fault stress to excavation activity and the rule of fault activation were examined. The results show that the fault damage has segmental characteristics. Microcracks are first generated at the fractured zone that is divided into lower, middle, and upper sections, located 30∼70 m, 120∼180 m, and 230∼280 m above the coal seam, respectively. There was also a segmentation phenomenon in the stress response of fault. The risk of fault activation was evaluated by using the ratio of shear stress to the maximum principal stress. When the working face was 260 m and 140 m away from the fault, the activation risk at the upper-middle and lower sections began to increase, respectively. When the fault was within 60 m, the risk of fault activation was highest.
Highlights
During the process of coal mining, mining in the vicinity of a fault can lead to abnormal movement of the overlying rocks and great intensification of mechanical pressure in the vicinity of the working face. is can produce a situation of increased hazard for workers at the face
Jiang et al [1] studied the regularity of normal and shear stress variation close to the fault by using threedimensional numerical simulation. e spatial-temporal evolution of the fault stress field during the excavation process was simulated, and the activation risk at different locations along one wall of a fault was presented. rough establishing a dynamic Colombian crack stress increment model, Ji et al [2] quantitatively analyzed the excavation disturbance effect and compared the different risks of fault activation when the working face lies perpendicular versus parallel to the fault face
Wang et al [4] investigated fault activation under excavation disturbance by establishing a similar material model. e results showed that the stress first dramatically increased and slowly grew, and the displacement moderately increased. is indicated that these features could possibly be used as precursor information for the fault activation
Summary
During the process of coal mining, mining in the vicinity of a fault can lead to abnormal movement of the overlying rocks and great intensification of mechanical pressure in the vicinity of the working face. is can produce a situation of increased hazard for workers at the face. In the studies mentioned above, the numerical simulation and physical model experiment are usually applied to study the characteristics of overlying rock movement and the laws of fault activation when a working face is passing through the fault. Based on the five-belt model, this paper studies the distinctiveness of fault activity within the fracture zone and investigates the spatial-temporal evolutions of damage at different segments along the fault. Due to the long-term natural fault movement, it is difficult to capture and detect damage and fracture information of the different segments of the fault completely by conventional monitoring methods during the space-time evolution process, especially for studying the mechanical behaviour of different segmental fault in deep rock formations. Microseismic monitoring technology is used to obtain the field data of the fault surrounding rock rupture, and the fault segmentation damage area is delineated to provide references for numerical simulation.
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