Study On Mechanical Properties Of Supporting Structure For Granite Residual Soil Tunnels Under Complex Conditions

There were distributed granite residual soil in most area, such as Hunan, Jiangxi,Zhejiang, especially in Fujian area. Granite residual soil is easy to disintegrate when encountering water, so the stability of surrounding rock should be merit special attention in the excavation of granite residual soil tunnels. Based on the national natural science fund project of the surrounding rock disintegration characteristics and Duanxi tunnel of Sha county, Fujian province, by using the indoor similar model test and numerical simulation, to discussed the influence of the granite residual soil tunnel support structure. The main research achievements are as follows:(1) Though plenty of investigations, analysis and calculation to obtain the needed strength of Cement-gypsum, the water gypsum ratio was 0.71, the cement content was 4 percent, the retarder was 0.1 percent and the thickness was 32 millimeter, which was used to lining materials.(2) Based on similarity ratio, designed the indoor similar model test of granite residual soil tunnel construction to research the influence of tunnel lining structure with the depth, the surrounding rock with different softening and forepoling bolt strengthening on granite residual soil tunnels. The result showed that with the increasing of tunnel buried depth, surrounding rock pressure, the hance and the ground settlement were increased slowly firstly and then increased dramatically. That was to say the greater the tunnel buried depth, the greater the effect on the stability of tunnel. At the same time, with the increasing of watering, the settlement is littler and the surrounding rock is increasing under the forepoling bolt strengthening. So by using forepoling bolt to pre-supporting the structural opening of granite residual soil tunnels is feasible.(3) Combined with the section of Duanxi tunnel, the tunnel model is established based on FLAC3 D. Though presupposing the initial pore water pressure of surrounding rock under the vault 6.47 meter to discuss the mechanical properties of granite residual soil tunnels for the surrounding rock was soften. The researches showed that the excavation of surrounding rock was dangerous for the surrounding rock was soften. So the surrounding rock should be drained before being excavated.