Evolution of Soil Arching Subjected to Dynamic Loads

Abstract

The Loess Plateau in Northwest China is located in a seismic area. Therefore, the high-filled cut-and-cover tunnels (HFCCTs) in this area are subjected to high earthquake risk. The load reduction measure of laying an expanded polystyrene (EPS) board on top of the Cut-and-Cover Tunnels (CCTs) can effectively reduce the earth pressure around the HFCCTs and lower the risk of potential failure of structures. However, due to the frequent disastrous earthquake events in the Loess Plateau area in Northwest China and the high dynamic sensitivity of the backfill soil, the seismic load may disturb the already stable backfill soil. Also, the stability of the soil arching effect and earth pressure due to load reduction under the seismic load is unknown, which may adversely affect the CCTs and, therefore, this unknown factor needs to be considered carefully in HFCCT design. Accordingly, the finite difference program, FLAC3D, was employed in this study to conduct numerical analyses of the earth pressure distribution around the CCTs and the evolution of the soil arching effect in the backfill when subjected to the seismic load. Parametric studies of seismic waves were also conducted to investigate two influential factors: the types of seismic waves and the peak ground acceleration of earthquakes. The results showed that the earth pressure around the CCTs and the soil arch evolution in the backfill were significantly affected by the seismic load. Therefore, the seismic load must be taken into account for HFCCT analysis and design in earthquake zones.