Influence of Fault on the Surrounding Rock Stability for a Mining Tunnel: Distance and Tectonic Stress

Stability of surrounding rock mass and safety of supporting system in mining tunnel are always dominated by fault near excavation limit. The influence degree of the fault varies significantly under different fault distances to mining tunnel and initial stresses condition. In this paper, a series of numerical experiments are conducted to study the displacement, stress, and plastic region in surrounding rock mass. The stress characteristics in sprayed concrete layer are analyzed to study the influence of the fault distance on excavation limit and the initial stress in ground. The fault distance is defined geometrically by a mutual perpendicular line between the excavation limit and fault line nearest to the mining tunnel to quantify the influence. In order to simulate fault specialty reasonably, an interface model based on the theory of cohesive joint element is proposed in the numerical experiment model. Some other disciplinary and quantificational regularities about the influence of the fault distance and tectonic stress are summarized based on the numerical results. The results show that there is a critical distance to judge whether a fault has a prominent influence to mining tunnel. The critical distance depends on the quality of mining tunnel surrounding rock mass, initial stress, and the degree of excavation limit curvature. With the increase of lateral stress coefficient, the vertical displacement at crown decreases, but the horizontal displacement increases in the both right and left sidewalls.

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