Stability analysis of diversion tunnels in the Qinling-Dabashan, segment,center China of the Three Gorges Water Diversion Project

The total length of the Qinling-Daba segment of the Three Gorges Water Diversion Project accounts for 80% of the total length of the project line. In order to analyze the problems of engineering geology that may happen during tunnel construction and operations, geological surveys, ground stress measurements and rock mechanical tests were made, and on that basis, simulation calculation were performed of the stress redistribution of surrounding rocks of the tunnel with the circle- straight-wall-top-arch- and horse's hoof-shaped cross sections at different depths in the northern part of the water diversion project by using the Ansys finite element software. According to the Hoek-Brown strength criterion, the rock strength/stress ratio was obtained. Furthermore, the stability of the surrounding rocks of the tunnel with different cross sections at different depths was analyzed. It is preliminarily considered that in choice of the tunnel cross section in the design of the Three Gorges Water Diversion Project we should give priority to the circle- and hoof-shaped tunnels when the tunnel depth is <1000 m and to a tunnel with a straight-wall-top-arch section when the tunnel depth is >1000 m. This research achievement provides reference for the design of deep-buried tunnels of a water diversion project.