Long-Term Interaction of Submerged Tunnels with Rheological Rock Masses & Time-Dependent Permeability

Submerged tunnels may pass through rock types and may encounter a variety of difficult geological conditions. One of these challenging conditions is confronting with highly stressed weak rock masses. The challenge pertaining to design of these tunnels is intensified when water seepage occurs into tunnel. In this condition, the rheological behavior of the rock mass causes the pressure acting on the lining to enhance over time, and consequently, the permeability coefficient of the rock mass in any point is changed over time. This paper investigates this problem, the tunnel construction process is all simulated in this study. Furthermore, based on the rock mass volumetric strain, a time-dependent variable permeability is assigned to the rock mass around the tunnel. A parametric study is conducted to evaluate the effect of rock mass rheological parameters, the internal water pressure, and the ratio of the rock mass and lining permeability on the submerged tunnel behavior. The results show that the internal water pressure extremely influences the tunnel response. Moreover, the permeability variation of the rock mass should be necessary, but unfortunately this is not feasible in most computer codes for three-dimensional numerical modeling.