Study on failure mechanism of tunnel-type anchorage using discontinuous deformation analysis method

Abstract

Tunnel-type anchorage are increasingly used in the construction of long-span suspension bridges. Numerical methods are a major means to study their bearing characteristics and failure modes. The current mainstream research method is still based on continuum mechanics, which cannot simulate the whole failure evolution process of tunnel-type anchorage-surrounding rock system. Therefore, discontinuous deformation analysis method based on discontinuous medium mechanics was used to carry out related research, comprehensively considering the influence of different rock mass quality and faults. The results show that: 1) In the case of soft rock and hard rock, the bearing capacity of the tunnel-type anchorage increases with the increase of the clamping angle, and the change in hard rock is more obvious. 2) Under the condition of soft rock, the envelope area of resistance body increases linearly with the increase of clamping angle. Because of gravity, the envelope area of the resistance body on the lower side of the tunnel-type anchorage is larger than that on the upper side. Under the four clamping angles of 2°, 4°, 6° and 8°, the envelope curves on the upper and lower sides of the tunnel-type anchorage are parallel to each other on their own sides. 3) Compared with the soft rock, the envelope areas of hard rock under the above four clamping angles are significantly increased, and the growth multiple is between 0.44 and 0.87. But in this case, the envelope area has no obvious change with the increase of clamping angle. 4) In soft rock, the envelope shape of the resistance body is a curve that is convex toward the outside of the anchorage; when it is hard rock, it tends to be a curve that is concave toward the inside of the anchorage. 5) Under the condition of hard rock, the integral deformation of surrounding rock on both sides of the tunnel-type anchorage is more obvious, which means that the load transfer range is wider and the clamping effect is more obvious. 6) The ultimate bearing capacity increases with the increase of the clamping angle, and shows a linear change trend. 7) Faults significantly weaken the bearing capacity of tunnel-type anchorage, but the impact of faults at different angles is slightly different. Finally, the whole process of deformation and failure of surrounding rock is intuitively displayed, and the load transfer mechanism can be peeped from it.