Numerical simulation on the excavation damage of Jinping deep tunnels based on the SPH method

In order to systematically evaluate the damage degree in Jinping deep tunnels during excavation, an improved SPH algorithm with good Lagrangian characteristics is introduced. By modifying the derivative of the traditional SPH kernel functions, the brittle failure processes of particles are realized. The 'Fissure Searching Generating Method' (FSGM) has also been used to determine the establishment of joints and the tunnel excavation parts. Based on the Jinping tunnel engineering practices, numerical models are set up, and the damage degrees of the tunnel excavation under different buried depths, joint distances, positions and inclination angles are numerically simulated, and compared with the engineering site pictures to verify the rationality. (1) Typical "V" shaped shear failure zones are observed when no joints exist in the model, and the damage degree increases with the increasing tunnel buried depth. (2) The increase of joint-tunnel distance causes the damage degree to decrease, and the failure modes between the tunnel and the joint transform from tensile to shear failure. (3) The stability of the tunnel is less affected when the joint appears in the vault, north and south arch shoulder, but the tunnel is prone to becoming unstable when the joint appears in the north and south walls. (4) Steep and gentle dips of the joints greatly influence the excavation stability of the tunnel, while the excavation damage range becomes the smallest when the joint inclination angle is 45 degrees. (5) The improved method can be well applied to predict and evaluate surrounding rock damage in Jinping tunnels.