Dynamic response characteristics of a steep loess slope with a tunnel under earthquake action

With more and more the transportation tunnels that have been and will be constructed in loess areas in Northwest China with high earthquake potential, the overall stability of tunnel portal sections under earthquake action and the related aseismic countermeasures has attracted the attention of both scholars and engineers, especially for tunnels in upper slope connecting high bridges crossing rivers or valleys. To study the dynamic response characteristics and damage evolution of steep loess slopes with tunnels under earthquake action, large-scale shaking table tests and numerical simulations were performed on steep loess slopes with tunnels. In particular, three-dimensional noncontact optical measurement techniques were used to obtain the slope surface displacements. The results showed that the main deformation patterns of the studied slopes were horizontal movement and settlement when the seismic waves were input in the X and X–Z directions, respectively. However, the seismic wave from the X direction had a greater impact on the deformation of a slope than that from the X–Z direction, and the tunnel portal slopes were ultimately destroyed under the action of a large horizontal seismic acceleration. Slope failure ahead of a tunnel was divided into four stages, i.e., the elastic deformation stage, plastic deformation accumulation stage, local failure stage, and overall failure stage. The existence of the tunnel had a great influence on the peak ground acceleration (PGA) and the PGA amplification factor (PGAAF) of the surrounding soil mass. The changes in the PGD and PGA on the slope surface determined via numerical simulation were basically consistent with the experimental results.