Underwater Shallow Tunnel In The Thickness Of Overburden Layer Of Security Research And Excavation Process Simulation

With the vigorous development of the Chinese construction, it springs up various river-crossing or cross-sea tunnel. And subaqueous tunnel construction will directly face selection for the safe thickness of roof at first. According to the previous experience, reasonable safe thickness of tunnel roof is not only an important economic indicator for underwater tunnel construction, but also an important factor of safety for underwater tunnel construction and operation. As the rock mass usually contains soft interlayer such as joints, crack, fault fracture zone and so on, and underwater tunnel inevitably encounter the coupling interaction between the seepage field and stress field, and because the geologic environment around subaqueous tunnel is complex and difficult to proven, thus the underwater tunnel construction is difficult and high risk. However, the research of underwater tunnel in China initiated relatively late, the systematic study on the least security coping thickness for an underwater tunnel are less, and there is no clear specification, it is still at the exploratory research stage at present. So the determination of the coping thickness for an underwater tunnel is urgently needed to be settled for current tunnel construction building. Therefore, relying on Liuyang River Underwater Tunnel of Xiang River Road in Changsha City, National Natural Science Foundation(50878213), and Changsha Science and Technology Project(K0902027-11), the disseration presents a numerical simulation study as the following:1. compare with and refer to international main experience, summarized the main empirical method, based on practical engineering of Liuyang River Underwater Tunnel, determined the reasonable security coping thickness for underwater tunnel by engineering analogy analysis.2. Combined the basic theory of fracture damage with fluid-solid coupling, the theory is applied in the three-dimensional differential procedure FLAC3D.3. Based on the proved tunnel site conditions, and consider fracture damage of joint fissure, numerical simulation analysis is made of the dynamic construction process in Liuyang River Underwater Tunnel, study on the stress and displacement variation characteristics of surrounding rock and supporting structure in different conditions, obtained influence coefficients of joint fissure by comparative analysis, and deduce the experience correction formulae.4. By FLAC3D numerical methods, and consider the fluid-structure coupling effect, the numerical simulation analysis for the tunnel construction at horizontal 17m below, combined with Japan's minimum water yield to research for seepage calculation, analyze tunnel coping thickness qualitatively.