The Research On Key Construction Techniques Of Large Deformation In Soft Rock Tunnel

Along with the further advance of the western development and the implementation of the strategy of One Belt And One Road. A large number of highway tunnel, railway tunnel and underground engineering are built, a lot of long and deep tunnel are starting. Due to the mountainous area of west China, complex geological conditions, the soft surrounding rock and geological hazards areas, such as high ground stress, sudden water inrush mud, across the body,often leads to large deformation.So the key of tunnel construction is to research prevention and control measures around the large deformation.Based on the theory of research large deformation tunnel type and mechanism and the characteristics of the large deformation of Baofeng tunnel, we analyze the mechanism of large deformation of Baofeng tunnel. In order to effectively control the large deformation of the tunnel, in the process of construction, use the advanced geological prediction to analyze the geological condition in front of the constraints of tunnel and predict the large deformation of the tunnel. And according to the monitoring results in the construction process, formulate rational and effective control measures of large deformation of tunnel by the engineering analogy method. Simulate step method, the ring core method, CD method, by using finite element analysis software MIDAS/GTS and analyze the influence of three different excavation scheme to tunnel surrounding rock displacement and surrounding rock stress. Considering the complex geological conditions of Baofeng tunnel and construction safety and construction progress, recommend to take steps method in the process of tunnel construction. Two key factors of supporting schemes, length of anchor bolt and shotcrete thickness, is simulated, it is effective guidance for engineering construction.In construction process of Baofeng tunnel, according to engineering experience, use the advanced small pipe grouting and pipe roof grouting techniques to control constraints first displacement and use steel arch shelf support, grouting reinforcement to control constraints rear displacement, it is effective to control the large deformation of the tunnel. In terms of monitoring measurement, 3 d laser scanning technology is adopted to treasure mountain tunnel monitoring measurement, it is obtained certain achievements, but there is a lot of improvement.In order to control the large deformation of the tunnel, it should be investigation of engineering geology and hydrogeology condition before the tunnel excavation and carries on the advance geological forecast in construction process to identifying the type of surrounding rock and surrounding rock parameters. it predicts large deformation situation through the numerical simulation. It chooses suitable excavation method and the corresponding supporting scheme by the engineering analogy method. According to the monitoring results in construction process, it judges the rationality of the excavation method and the corresponding supporting scheme, and decides whether to change the excavation support scheme. Baofeng tunnel project practice proved the feasibility of technology, and it is economic and reasonable.