Influence of Anisotropic Rock on Tunnel Stability with Consideration of Fluid-Solid Coupling

In general, rock mass is anisotropic because of presence of stratification, foliation or joints in it. In this paper we considered how the angle of anisotropy influences the stability of tunnel. By using COMSOL Multiphysics, fluid and 2D plane models are coupled to analyze stress-strain state, failure shape and water flow characteristic around tunnel for angle range from 0 degrees to 90 degrees with a interval of 15 degrees. Results show that in condition of vertical force of initial stress field larger than horizontal one, failure district is maximum for theta=40 degrees and minimum for theta=90 degrees where the strength of horizontal direction in anisotropic rock is smaller than the vertical one. In this case failure is mainly developed in roof and bottom. When the horizontal strength of anisotropic rock is larger than the vertical, results reverse. In anisotropic rock, the more the direction of larger permeability is coincident with one of source underground water acted, the more water flows into tunnel.