Research on the Effect of Dip Angle on Shear Stress on Normal Fault Plane and Water Inrush in Floor Strata During Mining
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ORIGINAL PAPER
Research on the Effect of Dip Angle on Shear Stress on Normal Fault Plane and Water Inrush in Floor Strata During Mining Activities Wankui Bu . Hui Xu
Received: 10 May 2019 / Accepted: 16 March 2020 Ó Springer Nature Switzerland AG 2020
Abstract This paper presents an investigation on the characteristics of shear stress on normal fault plane by employing the mechanical model and the characteristics of water inrush from floor strata during mining activities by employing numerical model. The shear stress formula on fault plane is obtained by using the solution of a homogeneous half-plane affected by normally distributed forces in the theory of elasticity. The mechanical model shows the variation of shear stress on fault plane with different dip angle and fault reactivation is analyzed according to the shear stress. Based on these, the fracture distribution and seepage distribution on floor strata are numerically simulated by using the RFPA2D-Flow software, and the effect of dip angle on water inrush from floor strata is discussed. These results indicate that the smaller value of dip angle is easier to be reactivated and to produce connecting fractures between floor strata and normal fault comparing with the larger value of dip angle, which provide significant insights into remaining coal pillar with similar geological conditions. Keywords Normal fault Fault dip Fault reactivation Water inrush Mining activities
W. Bu (&) H. Xu College of Urban Construction, Heze University, Heze 274015, China e-mail: [email protected]
1 Introduction Fault is a tectonic fracture in the Earth’s crust. It can be classified as normal, reverse and strike-slip types according to the direction in which the relative movement of hanging wall and footwall has taken place. Prediction and prevention of fault reactivation have been major safety concerns for long-term mine safety and productivity in underground coal mines. There are very few cases of water inrushes from floor strata in America, Russia, Poland, Canada, Australia, Germany, India and the United Kingdom (Singh 1986; Vutukuri and Singh 1995). The main method for controlling water disasters in these countries is the application of various water exploration techniques and equipment. In contrast, more than 90% of water inrushes in mining engineering in China are due to water inflow from karst aquifers through coal seam floor, especially the floor with fault structure. The main technique for controlling water inrush through floor strata is to remain sufficient coal pillar against the aquifer and/or grouting of the floor strata (Gao and Shi 1999), which leads to the waste of coal resources. After nearly a century of mining activities, most coal mines in China are extracting deep coal seams, and geological structures, such as fault, play more and more important role in controlling the karst water flow into the longwall face (Miao et al. 2004; Li et al. 2002; Wu et al. 2003; Han et al. 2009; Hu et al. 2014; Gao et al. 2017
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