Research On Tunnel Collapse Mechanism And Treatment Measures In Da Shan Expressway

With the construction of infrastructure in our country, the design of expressway tunnel and the technology of construction have developed rapidly. In the construction of the tunnel,collapse is one of the great harm of geological disasters,the cost of collapse treatment increases year by year.. During the tunnel excavation, collapse is frequent happen because geological structure, construction methods. The occurrence of collapse, which seriously impact the tunnel construction safety, also caused a great economic losses. Therefore, the collapse accident mechanism, and processing method are summarized, the rapid construction safety after tunnel has great practical significance.Based on collapse during the tunnel construction of sichuan Dashan expressway for example, using geological survey, the theory analysis and numerical simulation methods to research the factors and mechanism caused by collapse, and the paper summarized the collapse treatment measures are analyzed, and the main achievement include:(1) Based on the analysis of the tunnel collapse examples, summarizes the main influence factors of da shan superhighway tunnel collapse including five aspects : Structural fracture zone,indirect effects of groundwater,water gushing tunnel bias and construction method.Meanwhile the type of collapse is summarized, and the type of tunnel collapse be classified four factors :the control factors, inducing factors, cave-ins form factors and mechanism factors classify four factors.(2) According to the collapse mechanism that former summaried with da shan expressway tunnel collapse, it is concluded that there have five kinds of mechanism : shear - slide, splay -collapsing, plasticity - extrusion, flow - collapsing and vibration - collapsing. (3) For different supporting structure by FLAC3D numerical simulation the reinforcement mechanism analysis. We can get that there have a little work on, sheet and relies on increase anchor is ineffectively improved the rock mechanics properties; In the conditions that do not take other supporting means in the premise, steel arch frame spacing shoulds not be more than 1.2 m. Based on the numerical simulation of the typical collapse,wo can conclusion that: minimum principal stress in arch perpendicular to the waist bits in vaults parts or nearing orthogonal. In addition, after excavating at various levels in a certain range of surrounding rock excavation boundary appeared in different degrees of plastic damage area. In vaults and bottom mainly by drawing sex destruction, arch waist and arch feet site shear failure to give priority to.(4) Combined with Dashan road and other related information to the treatment of the collapse, fault fracture zone, the gas, bias, water gushing under different types of collapse proposed the reasonable processing measures of different scale, and put forward reasonable of collapse treatment plan.(5) Adopted to monitor measuring technology, To prevent further deformation damage , combined with the examples, proved the feasibility and advantage of informatization construction.