An Elasto-Plastic Model for Analysis of Underwater Tunnels, Excavated in a Strain-Softening Hoek-Brown Rock Mass

In this paper, an analytical method for the analysis of underwater tunnels in axisymmetric plain strain conditions is presented. A new technique has been proposed using finite difference numerical method for calculating the distribution of pore water pressure as well as stress and strain around a circular tunnel excavated in rock mass. Behavior of the rock mass around the tunnel is considered elasto-plastic in strain-softening model. Meanwhile, the effects of increment in elastic strain within plastic zone and dilatancy angle are taken into account. Seepage flow and secondary permeability due to hydraulic-mechanical coupling have also been considered in the plastic zone.A more accurate model has been provided for calculating the distribution of pore pressure in the elastic zone by modifying the previous models. Since governing equations do not have a closed form solution, a computer program has been prepared based on the proposed model. Accuracy and applicability of this method have been investigated with an example.

Keywords:

Underwater Tunnels , Seepage , Pore Pressure Distribution , Groundwater , Strain-Softening