Study Of Deformation And Failure Mechanisms And Reinforcement Measures Of HeiShan Tunnel

Collapse is one of the most common disasters in tunnel construction, which causes construction delays, loss of life and property, make the safe operation of tunnel exists the significant security risks, therefore, it is important to study deeply the collapse mechanisms of soft broken rock tunnel and reveal the destructive process, stress and deformation of surrounding rock, which can prevent collapse disaster of other places of HeiShan tunnel and help us make the reasonable and effective reinforcement measures.HeiShan tunnel which is a tunnel of ZhangZhuo highway is as the background, the following works have mainly been done:(1) Based upon particle flow theory and PFC code, the flat-joint contact model is used to construct the numerical model of rock thick-walled hollow cylinder, which can reflect the feature of mineral grain in rock. The failure mechanism and law of rock thick-walled hollow cylinder with different inner and external pressure is investigated from meso mechanical viewpoint and some research results are shown as follows.When inner pressure is equal to zero, tensile microcracks dominate in failure process and the symmetrical V-shaped damage area within spalling fragmentation particle assmblise forms to the axis center. When inner pressure is not equal to zero, the limiting external pressure increases and shear microcracks gradually dominate in failure process with the increase of inner pressure. Meanwhile, the symmetrical V-shaped damage area in specimen degrades and failure expands toward all directions from inner rock face. Whether the inner pressure is equal to zero,the evolving curve of failure parameters such as external pressure and external volume strain can be divided into three stages.(2) By reference to the large number of documents and the ratio of the test results to determine the ratio of similar materials performed similar material model test holes to Heishan Tunnel. Test footage using two excavation, focusing on parallel spacing conditions in this surrounding rock displacement and stress in the tunnel, the rock surrounding the hole under no condition failure mode support, and coMParative analysis of the footage of the excavation around stability of rock.(3) Based the laboratory tests, after the reasonable discount and repeated pilot calculation, the micro-mechanical parameters of rock have been gotten, then using particle flow software (PFC2D) analyzed the effects on collapse processes caused by the span, flatness and surrounding rock classification.(4) Based on our previous studies on the collapse mechanism, the supporting program of soft broken rock has been optimized, and the supporting effects of optimized program have been researched by simulation and field monitoring, the result shows that the optimized program has a positive effect on ensuring the excavation stability of fault zone and preventing the collapse of the tunnel, finally, according to the construction experience of HeiShan tunnel, prevention measures of collapse have been put forward.