Study On Surrounding Rock Stability Of High In-Situ Stress And Large Embedded Depth Intersection Tunnel

With the developing tide of China’s constructing, it have built a increasing number of tunnels and underground chambers that many of them have to carried out while the rock is of large embedded depth and of high in-situ stress. For instance, large hydropower often constructed in project area of poor or bad mountain condition that combined effects of gravity stress and tectonic stress frequently affect stability of underground chambers rock around and structural safety. Especially as a result of requirement of underground chambers framing, it built many intersection tunnels that will farther affect construction safety that produce no common tunnel shape, reduce surrounding rock strength and significantly weaken mechanical parameters of rock around. Therefore, more in-depth research must be taken on surrounding rock deformation law, stress redistribution and stability of surrounding rock that provide reliable basis for reasonable optimization construction program, supporting structure and parameter.This thesis depend on the research project of New Construction Technology of Jinping Hydropower Station Diversion Tunnel with Deep Cover and Rich Water, background typical intersection tunnel Node4#of Jinping Hydropower Station and discuss the following issues after research probably puzzle of underground chambers with high in-situ stress:1. With Engineering practice of Jinping Hydropower Station, analyzed and evaluated geological conditions of Jinping, Geometric shape and size of tunnel section, layout and feature of intersection tunnel, construction conditions and earthquake situation. And then specific analyzed a series of questions of instability and landslides of intersection tunnel rock around, foundation as determine follow-up control measures.2. Excavation work order and supporting structure was researched that principal focus on the timbering parameters of Node4#which with frequently geological disaster, and reasonable project of blast and timbering was present.3. The whole process of simulation was taken to excavation of typical intersection Node4#of high in-situ stress of Jinping Hydropower Station, and worked out the feature and laws of the deformation and stress of each tunnels and parts, in particular, the weakest surrounding rock of acute angle position. According to this, optimized the construction program and supporting structure.4. Surrounding rock monitoring results show that stress measured values of it change in a small range during the excavation process of large profiled tunnels with high in-situ stress, stress values change in a little scale with time and stabilize at the end, each section has a small deformation, significantly reduce in7to10days. The convergence value stabilize when reduced to a certain value, occasionally appears the situation of minor recovery. It shows that the optimized excavate and support solution could better ensure the stability of surrounding rock and Structural safety of the intersection tunnels.