Abstract

According to non-equilibrium evolution stability and control theory, over force is the internal effective driving force of unrecoverable time-dependent deformation. The distribution of over force reflects the failure position and mode of tunnel. The opposite force of over force is the optimal reinforcement force to prevent unrecoverable time-dependent deformation and provides a quantitative and accurate reinforcement design method for tunnel. The plastic complementary energy (PCE) is the norm of over force. The curve of PCE versus time provides a unified quantitative criterion of real time dynamic stability evaluation of tunnel in time-dependent deformation process under various external disturbing factors. Based on the curve of PCE versus time, the stresses of lining structure in different supporting time after excavation are studied comparatively. The results show that the stress of lining structure will be very high if supporting time is too early. The surrounding rock of tunnel will be unstable due to damage evolution if supporting time is too late. There is an optimal supporting time when the stress of lining structure will not be too high and the surrounding rock will not lose stability. The curve of PCE versus time can be used to guide reinforcement design and evaluate reinforcement effect.

1. Introduction

Time-dependent deformation will inevitably occur after excavation disturbance of tunnel surrounding rock. Under the condition of low situ-stress, the deformation can gradually converge and stabilize, but under the condition of high situ-stress, the deformation will continue to develop, forming plastic zone or even damage zone. This process can be regarded as a non-equilibrium evolution process. On the one hand, the structure will give full play to its own bearing capacity, gradually tend to a stable state, showing a trend of self-equilibrium evolution; on the other hand, the occurrence of plastic zone and damage zone leads to the deterioration of surrounding rock parameters, the structure self-supporting capacity becomes worse, tends to an unstable state, deviates from the equilibrium state. Therefore, it is necessary to find an optimal support time, which can make the surrounding rock give full play to its bearing capacity, reduce the thickness of lining structure, and avoid tunnel instability.

This content is only available via PDF.
You can access this article if you purchase or spend a download.