Study On The Initial Geo-Stress Of The Deep-lying Tunnel Region And The Stability Of Surrounding Rock

With the implementation of stratagem concerning the great development of western region and the important position of hydroelectricity exploitation, lots of hydraulic underground caverns will be built in the rugged mountainous area of Western China, the stability of which will affect whether the construction can be successful and the operational benefit of projects. Meanwhile, the stability of underground projects is connected to the initial geo-stress of the rock mass. So, whether the initial geo-stress is credible will decide the safety and reliability of the design and operation of underground projects.This paper takes the diversion tunnels project of Jinping II hydroelectric power station for example, studies and summarizes the cause and influencing factors of the initial geo-stress. Try to improve the inversion precision from these parts, which are locations of measure points, measure methods, analysis of the measured results and methods of regression, supply exact initial condition for the excavation of underground room, and major studys are as follows:First, analyze the influence of underground water to the measure of geo-stress by hydraulic fracturing method.Second, do further study on the linear regression method which is common used nowadays, especially on the influence of different simulate ways of horizontal tectonic movements, and educe corresponding conclusions. When measured results show that there are different tectonic movements in the study region, we should do regression in each part separately.Third, because of the complex mapping relation between initial geo-stress and its influencing factors, and the strong in-out ability of ANN, establish the relationship between stress and its influencing factors by BP neural network, and evaluate its merits and drawbacks. In the linear regression method, the regression coefficients have no exact physics meaning and need hypotheses that rock mass is in elastic state. Meanwhile, in the ANN method, the training samples are difficult to generate. Combining the linear regression method with ANN method can solve these problems perfectly.And the last, because of the high initial geo-stress in Jinping project region, this paper does some simple analysis of the excavation stability and its prophylactico-therapeutic measures of underground room in high initial geo-stress.