An elasto-viscoplastic hydro-mechanical coupled analysis and its application to a cavern excavation in soft rock

In order to predict the mechanical behavior of an underground cavern, which is constructed in a soft rock ground, it is necessary to study the strain hardening-softening characteristics of soft rock as well as the dilatancy and the effects of pore pressure on the materials. Furthermore, on the large cavern excavation problem, the confining pressure and the strain rate around the cavern change during the cutting process of the cavern. In this study, an elasto-viscoplastic constitutive model is firstly improved to describe the behavior of soft rock by taking into account the effects of the confining pressure and the strain rate. Using this model, hydro-mechanical coupled analysis carried out to predict the behavior of an underground cavern before its excavation. When comparing the predicted values with such monitored values as the ground movement, the pore pressure induced in the ground, and the stress induced in the support systems, a good agreement can be seen. Thus, this analytical method is verified as being applicable to predictions of the behavior of underground caverns during construction. (author)