Fault-slip induced by longwall mining is a significant cause of indirect coal burst. This paper summarises the results of a numerical modelling study using FLAC3D, in which a longwall face approaches a fault with different fault angles of 45°, 60°, 75° and 90°. Zero-thickness interface elements, which are capable of Coulomb sliding, were built in the numerical model to simulate the fault. The paper presents detailed parametric analysis of the influence of cover depth, friction angle of the fault plane, fault angle and approaching direction. Numerical results showed that these factors have a significant influence on shear stress drop, shear slip and the magnitude of seismic energy. In terms of fault behaviour during longwall extraction, shear stress on the fault plane above the coal seam first increased and then decreased when the longwall face was approaching the fault. The maximum magnitude of seismic events occurred when the longwall face was 15 m to 40 m away from the fault. Most seismic slip occurred on the fault plane above the coal seam with minimal movement below the coal seam.

1 Introduction

Coal burst has been a major problem in underground mining for decades (Mark, 2016). There are many factors that can result in coal burst, such as deep cover depth, massive rock layers above or below the coal seam, faults and other geological problems (Ortlepp, 2005; Iannacchione & Tadolini, 2016; Zhang et al, 2017). Of these causal factors, Ortlepp (2005) stated that fault-slip is a significant factor that can produce higher potential seismic energy than the other factors. Therefore, this paper mainly focuses on seismic behaviour along a major fault when the longwall face approaches it in various geological and geotechnical conditions. Several numerical models were built using FLAC3D to conduct a detailed parametric study to evaluate impact of the fault angle, friction angle of fault and mining depth. The magnitude of seismic events induced by fault-slip in longwall mining is evaluated.

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