Study on inversion of in-situ stress of layered rockmass in deep buried tunnel

Based on the data of Gonghe tunnel in Yu-Sha express highway,different groups of in-situ stress in the tunnel site region are acquired by adjusting different coefficient combination of horizontal pressure.The in-situ stress of layered rockmass in sections of measurement is calculated by transverse isotropy elastoplastic model.By comparing the two results,the reasonable coefficient of horizontal pressure in tunnel site region is confirmed and then the magnitude and direction of in-situ stress along the tunnel axes is obtained.The research shows that the in-situ stress along the tunnel axes is related to the buried depth of tunnel and the topography,that is,the in-situ stress near the mountain is larger than that near the river.The maximum of in-situ stress,which is 19.7MPa, is mainly in the depth from 500m to(1 000m,) namely,in the section of K41+500～K43+000,and the angle with horizontal is-71.58°.The research provides some fundamental data for tunnel construction and design.