ANALYSIS OF GROUND WATER SEEPAGE TOWARDS TUNNELS

Tunnelling in water bearing soils affects water conditions in the surrounding ground and tends to produce seepage towards the opening. This may result in water inflows into the tunnel, face instability due to high hydraulic gradients and long term settlements induced by the dissipation of pore water pressures. The purpose of the work described in this paper is to analyze seepage towards tunnels under steady conditions by means of two-dimensional and three-dimensional finite element models. The influence of ground conditions, such as soil anisotropy and layered ground profiles on the water flows, are analyzed for permeable tunnels and lined tunnels of finite permeabilities. The paper also considers the three-dimensional flow pattern towards the face of a tunnel under construction, with emphasis on the influence of soil anisotropy as well as the presence of a grouted soil mass at the face, on seepage towards the tunnel. For the covering abstract see ITRD E108371.