Instability forecast and risk evaluation of the surrounding rock masses for deep-lying tunnel

Applying the catastrophe theory, based on observed data of surrounding rock deformation, the cusp catastrophe model of instability of deep-lying tunnels is established. The mechanical criterions of instability are educed. The analysis of an actual case shows that the research results are consistent with the surrounding rock stability of the demonstration project field. The present results can offer references for preventing instability and damage of deep-lying tunnels, taking reasonable construction measurements.