Study On The Deformation Control Criteria Of Tunnel With Soft Surrounding Rock

Up to now,the formulation of control criterion for the soft rock mass tunnel is still a difficult engineering problem. And the study of benchmark for each excavation step is till in a state of blank.The under constructed Guanggan highway through across themeizoseismal area of the Wenchuan Earthquake.And the main surrounding rock of this highway is of phyllite which has the characteristics of low strength and water softening. Several large deformation and collapse accident take place during the construction period. Takes the Dujiashan Tunnel as the background, the thesis makes a study on the deformation law of the tunnel with a surrounding rock of sandy phyllite and sericite phyllite.And a control criterion of each each excavation step is layed down. The main research contents are as follows:(1)Analysis based on the monitoring data gives a conclusion that the complex geological environment is the main reason for the large deformation and cave-in accident. But the deformation of early phase during the step by step excavation is also an important factor that leads to large deformation or collapse of the follow-up construction of surrounding rock. Therefore a control criterion excavation for step shall be formulated.(2)The comparison and analysis of monitoring data found that the tunnel buried depth, lithology of surrounding rock, cross section form all has certain influence on hole week displacement. And due to the arch effect, the growth rate of holes weeks displacemet is larger when the buried depth is less than100m. Lithology of surrounding rock also has a big impact on displacement, while the impact of The section form is relatively small.(3)By means of combining the numerical simulation and model test, deformation law of the sandy phyllite and sericite phyllite under different buried depth is studied and the results tallies with the analysis of field measured data results.(4)Based on the research of soft rock tunnel surrounding rock deformation law, and refer to the current benchmark displacement control at home and abroad, A displacement control benchmark of every excavation step according for sandy phyllite and sericite phyllite is layed down.