关键词: 山岭隧道, 仰坡, 地震, 动力响应, 振动台模型试验

Abstract: A large-scale shaking table model test is conducted to study the dynamic behavior of entrance slope and its interaction with lining structure of mountain tunnel under earthquake loading. Test results show that the acceleration response of tunnel entrance slope exhibits obvious amplification effect and surface effect along both vertical and axial directions. Significant nonlinear behavior is observed when the earthquake loading amplitude is larger than 0.6g; and after that, amplification factor decreases with the increase of input loading amplitude and additionally the distribution of acceleration becomes more even in the slope body. It is also found that the dynamic response along axial direction of entrance slope does not affect much by existence of tunnel structure; thus it could be evaluated by treating the entrance slope as a natural slope for simplification. On the other hand, however, the potential instability of entrance slope has much influence on the safety of tunnel structure. When the loading amplitude is relatively small, internal force induced by vertical acceleration is larger than that caused by horizontal acceleration. As the loading amplitude becomes larger, the horizontal component of earthquake plays a dominant role in affecting the lining structure. The failure surface is located at the upper part of entrance slope, especially on the shoulder. The failure process could be described as five steps: (1) earthquake excited; (2) slope shoulder cracked due to tensile failure; (3) the cracked rock of shoulder toppled and collapsed downwards; (4) the collapsed rock fell along the slope and crushed to debris; (5) rock debris accumulated at the slope toe. The experimental result provides valuable basis and guidance for analysis, calculation and design of mountain tunnel portal.

Key words: mountain tunnel, entrance slope, earthquake, dynamic response, shaking table model test