VIP free Tunnel construction in high ground stress area
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Tunnel construction in high ground stress area is prone to collapse, rockburst and other deformation and fracture phenomena. When the surrounding rock is high in category, hard in texture, dry and waterless, rockburst is prone to occur. When the surrounding rock is low in category, soft rock deformation and collapse are prone to occur. 1、 Prediction of rockburst and construction measures: (I). Prediction 1. Geological prediction: when the tunnel is deeply buried, after each excavation cycle, a geological survey will be carried out, and the geological sketch map and geological display map of the excavation working face will be drawn. Geological prediction will be carried out according to the geological survey results. 2. Field test of secondary stress field of rock mass. At the same time, the site rock point load strength test was carried out, and the rock burst and grade were predicted by using the rock uniaxial compressive strength Rb of the tunnel wall with tangential stress. (2) Construction measures: 1. Construction support and safety protection: add temporary protection facilities, install protective net and protective shed frame for main construction machinery near the excavation face in the section prone to rock burst, and provide steel helmets and bulletproof vests for construction personnel, and hang steel wire mesh on the face. According to the analysis of geological prediction and field test results, the steel fiber concrete is sprayed at the sections where rock burst may occur. The steel fiber content is about 5%, and the spraying layer thickness is 8~10cm. The light light explosion can be effectively prevented to ensure that the surface can withstand large deformation without cracking.