The Modification and the Application of Ground Pressure Calculation Model for the Shallow Tunnels under Seismic Scenario

Abstract

The traditional simplified model for ground pressure calculation is widely used in the anti-seismic design of shallow tunnels. However, it presents two obvious deficiencies, which are related to the block equilibrium and the additional seismic load respectively. A modified calculation model is proposed in this article by introducing the concept of slip angle, so that the deflection of potential slip planes and the distribution of ground pressure can be considered and further discussed. By combining the horizontal slice method and graphical method, a series of explicit formulas for calculating ground pressure are presented so that the vertical ground pressure, the rupture angle, and the lateral thrust can be calculated more accurately. The proposed modified model is compared with the existing model to validate the correctness of calculation results. The results show that the explicit formula of modified model could be reduced to Liu's formula when the potential slip planes are assumed to be vertical. Additionally, the sensitivity analyses on the vertical ground pressure, block volume, and distribution pattern of the lateral thrust are carefully investigated. The lateral thrusts acting on the left and right wedges distribute logarithmically and exponentially respectively, which implies that the distribution pattern is mainly affected by the direction of earthquake inertia force, while the cohesion and the friction angle merely influence the magnitude of lateral thrust to some extent.