Analysis of the influences of fault on the distribution of stresses and displacements in the rock mas around the tunnel under seismic loading

Abstract

Construction of underground tunnels will disturb the initial state of geomechanical equilibrium and change the in-situ primary stress - strain state in the rock mass around the tunnel and can cause destructive incidents in different forms and levels. A thorough understanding of the changing process of the stress - displacement state and the forms and levels of destructive incidents that may appear in the rock mass around the tunnel is very necessary to to ensure accurate and safe design and construction of tunnels in the real in-situ conditions at the tunnel location and especially when the rock mass is subjected to earthquake. This article introduces some numerical simulation results on the seismic wave propagation process, on changes in stress and displacement states in the rock mass with small fault of an dip angle of 450, around a circular cross-section tunnel, using the discrete element method (Universal Distinct Element Code-UDEC). Three cases are simulated: a) the tunnel is located in the hangingwall rock, the fault is located 10m from the center of the tunnel on the vertical axis; b) the fault runs through the center of the tunnel and c) the tunnel is located in the footingwall rock, the fault is located 10m from the center of the tunnel on the vertical axis. The results obtained show a very clear influence of the position and location of the fault on the geomechanical changes in the rock mass around the tunnel subjected to earthquake. The simulation results can contribute to more accurate forecasting and design. The research results can also provide some theoretical concepts on stability and control of fractured rock masses when an earthquake occurs.