| To the tunnel of broken surrounding rock, deformation monitoring and construction process of surrounding rock deformation and mechanical characteristics are analyzed, and the analysis has the vital significance to guide tunnel safety construction. Based on Yunhu No. 2 tunnel engineering and combining with its engineering geology, through theoretical analysis, monitoring measurement and numerical simulation, the stress, displacement, deformation and supporting measures of tunnel,which is in broken surrounding rock, are studied. To the project of tunnel, surrounding rock deformation characteristics, the laws of displacement and stress for surrounding rock in the dynamic construction are analyzed. The construction technique and steel supporting parameters are optimized in this paper, which can do a reference for the similar projects. The main research work and achievements are as follows:(1) An analysis of the theory of surrounding rock stress state, and in combination with the practical situation of project, when surrounding rock under the three times of stress state, the influences on plastic zone and displacement of tunnel after excavation, which by the buried depth of the tunnel, the strength of surrounding rock and support resistance, are got.(2) By monitoring measurement, the deformation laws of vault sedimentation and level convergence of measuring line on the upper bench to tunnel are analyzed. Measuring data of monitoring measurement are analyzed by regression. The optimal regression equation is selected through comparing. The final deformations of the tunnel monitoring section are calculated.(3) Based on the data regression analysis, in combination with rules,the construction time to second lining for the tunnel monitoring section is calculated. And the time can select the 25 th day of the begin monitoring.(4) Based on the numerical simulation of dynamic construction for the Yunhu No. 2 tunnel, the distribution rules of surrounding rock deformation and the stress in the course of tunnel excavation are analyzed.(5) According to the change curves of deformation and stress to vault, measuring line on the upper bench and arch springing in the whole process of dynamic construction, the change trends are discussed. And the causes of this change are discussed. Finding for the construction with bench method, the influence of deformation and stress to surrounding rock by excavation of the upper bench is greater than by the lower bench. Comparatively speaking, the effect of deformation to arch springing by the excavation of lower bench is bigger than to vault and measuring point of upper bench.(6) Selecting different step length to numerical simulation, find that the longer the step, the greater the vault subsidence and level convergence of surrounding rock, and the greater the stress release in the process of excavation. This is not conducive to keep the tunnel stable. Relatively speaking, the step length greatly influences the level convergence of arch springing. In the actual construction, construction of short step should be chosen. Using different footage of excavation, find that the greater footage, the greater the deformation of tunnel surrounding rock. The different footage has most influence to deformation of measuring point on upper bench. The greater footage, the greater the stress release in the process of excavation. Through the contrast analysis, the project can consider to use 1.3 m or 1.5 m footage to construction. To optimize the supporting parameters for different section steel, research shows that tunnel support to broken surrounding rock should be determined by the situation of tunnel surrounding rock, and adopt the best form for support. |
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