Study On The Method Of Stability Analysis Of Underwater Tunnel Face Which Crosses The Fault Fracture Zone

With the rapid development of China’s transportation infrastructure construction, all kinds of underwater tunnels crossing the river or sea emerge in a large amount. And the underwater tunnel construction inevitably meet that the tunnel goes through the fault fracture zone. The stability of surrounding rock is poor, because of the fault fracture zone’s surrounding rock is broken and connect with river. It is a difficult and high risk construction, which is very easy to generate tunnel face sloping and sudden water inflowing in the construction of underwater tunnel which goes through the fault fracture zone. Therefore, it has great significance to ensure the construction safety of the underwater tunnel goes through the fault fracture zone by researching on the stability of the the underwater tunnel face, determining the reinforcement measures concretely.This paper relies on the research projects of Natural Science Foundation of China and China Railway Tunnel Group, and takes the Xiangjiang tunnel of Yingpan Road in Changsha city as the engineering background, adopts theoretical derivation and numerical analysis to analyze the stability of tunnel face. Four major tasks are given as follow:(1) Analyzed the stability of underwater tunnel face which goes through the fault fracture zone by the method of theoretical derivation, derived the calculation expression of tunnel face’s stability coefficient under the action of groundwater permeation, which bases on Janssen’s Silo theory and Horm’s analytical model of the stability of tunnel face.(2) Established the model of reinforcement ring elastic foundation beam and derived the computational expressions of the foundation reinforcement ring by the control differential equation of Pasternak’s foundation beam and the deflection equation of grouting circle. Then established the calculation method of underwater stability coefficient in the condition of grouting strengthening.(3) Calculated the tunnel face’s stability of the Xiangjiang tunnel of Yingpan Road goes through F1and F3fault fracture zone by the derived calculation formulas, which under the situation of not-advanced grouting strengthening and advanced grouting strengthening. And then analyzed the safety of the construction. And determined the proper thickness of reinforcement ring.(4) By the method of numerical analysis to analyze the stability of Xiangjiang tunnel face. Then, verified the accuracy of the theory by comparing numerical result to the theoretical result.(5) The methods of analysis this paper puts forward can be used for analyzing the stability of the underwater tunnel face in construction.