Abstract：In order to forecast the destabilization and dangerous situation of surrounding rock of weathered rock tunnel and primary support system，combining with a practical engineering of shallow-buried tunnel，according to the principle of evaluating system stability with the variable tendency of its compatibility，with measured displacement data being smoothly processed and forecasted data being generated after once accumulation again，a grey-cusp-catastrophic destabilization prediction model of surrounding rock and primary support system is established by applying scientific theory of systems engineering and grey-cusp-catastrophe theory in nonlinear science；and then，the relation between the ratio of vault settlement to the deformation convergence of side wall around tunnel and time after primary support is fitted by polynomial regression；and the destabilization time of surrounding rock-primary support system is predicted by the grey-cusp-catastrophic destabilization prediction model. Furthermore，the destabilization and dangerous situation of surrounding rock and primary support system under the condition of steady rainfall are analyzed. The research results are shown as follows. Firstly，the stability of the surrounding rock and primary support system may be judged from analyzing the variable tendency of its compatibility with the grey-cusp-catastrophic destabilization prediction model. Secondly，the critical time and time difference of system destabilization may be more accurately derived. Moreover，the destabilization process including the critical state of the system may be accurately forewarned and forecasted by the established grey-cusp-catastrophic prediction model.
