Study On The Dynamic Pressure Arching Characteristics Of The Tunnel Constructed In Soft Surrounding Rock

With the large investment of highway construction and the mature of tunnel constructiontechnology in our country, both in the quantity and length of tunnel have been in the firstplace in the word. However, because of different kinds of factors such as large cross-section,complex geological conditions, improper construction, and so on, the collapse phenomenon isoccurred in the construction of tunnel inevitably. Studies have shown that the arch effect isformed after the stress of surrounding rock is redistributed in the tunnel collapse, but in themost present study the pressure arching is constant, which cannot truly reflect the forcedeformation of tunnel surrounding rock.Based on the previous studies, the mechanism and the dynamic developing law ofarching are researched in the soft surrounding rock through the method of theoretical analysis,model test and numerical simulation. Also the dynamic pressure arching which is caused bythe deformation and collapse of tunnel rock is studied deeply.The main tasks are as follows:1. The formulation of pressure arching thickness of surrounding rock is derived by usingthe method of theoretical analysis.2. Adopt model test method to measure the changes of stress around the tunnelsurrounding rock for different severe, different excavation methods and different kinds ofcollapse, process and analyze the measurement data, combined with the actual test conditionsthen the law of corresponding stress variation was given.3. Use the ANSYS software to simulate the full-face tunnel excavation and the process ofdestruction, establish a whole section of the tunnel excavation damage numerical model, andexplore the stability of tunnel under the conditions of different strength reduction coefficient.4. For roof fall and vaulted collapse of the tunnel, full-face excavation and top andbottom benching excavation, and different forms of landslides and different excavationmethods, space morphology and dynamics developing law of pressure arching were studied,and a new series of conclusions were drew during the destruction process of tunnelsurrounding rock.