Behavior of Tunnel and Neighboring Joint with and without Presence of Rock Bolt under biaxial loads; Particle Flow Code Approach

Abstract

In this paper, interaction between semi-circular space and neighboring joint with and without Presence of Rock Bolt is investigated using Particle Flow Code. For this purpose, firstly calibration of PFC was performed using both of the Brazilian experimental test and uniaxial compression test. Secondly, numerical model with dimension of 100mm *100 mm was prepared. A semi-circular space with radius of 25 mm was situated below the model. A joint with length of 40 mm was situated above the space. Joint opening was 2mm. Joint angle related to horizontal direction was 0°, 15°, 30°, 45°, 60° and 75°. Totally, 6 different configurations of semi-circular space and neighboring joint were prepared. These models tested with and without presence of vertical rock bolts by biaxial test. The Rock bolt length was 50 mm. The value of lateral force was fixed at 2 MPa. Axial force was applied to the model till final failure was occurred. The results shows that presence of rock bolts change the failure pattern of numerical model. In absence of rock bolt, two tensile wing cracks initiate from joint tip and propagate diagonally till coalescence from model boundary. Also several shear bands were initiated in the left and right sides of the tunnel. In presence of rock bolt, several shear bands were initiated in the left and right sides of the tunnel. The compressive strength with presence of rock bolt was more than that without presence of rock bolt. The failure stress has minimum value when joint angle was 45°.