Failure mechanism investigation of tunnel face subjected to high hydraulic pressure

Abstract

A huge amount of underwater ahead of tunnel face surges abruptly into the excavated cavern with respect to the high hydraulic pressure after the karst geology is penetrated. In order to avoid the construction accidents in tunneling, it is particularly important to investigate the failure mechanism of the tunnel face subjected to the high hydraulic pressure. To establish a water-surged model centered on the disturbed tunnel face, both the elastic-plastic stress and the high hydraulic pressure are considered simultaneously. Afterwards, a simplified analytical solution based on the Hoek-brown criterion is developed. An illustrative example is used to demonstrate the performance of the proposed solution. The simplified analytical solution derived in this study is validated by the numerical simulations. In addition, a series of numerical simulation are performed to investigate influencing factors of the disturbance zone range ahead of tunnel face. The results indicate the simplified analytical solution of the plastic zone ahead of tunnel face under the different supports can be applied for the stability of hydraulic tunnels, preliminarily estimate the failure zone ahead of tunnel face. The range of plastic zone ahead of tunnel face is greatly influenced by the tunneling radius, surrounding rock grade and the hydraulic pressure.