FEM Analysis Of Tensile Stress Characters Of JingYu LongGang Tunnel

With the development of our national economy construction, the scale and quantity of tunnel buildings increase significantly to a great extend. The surrounding rock stability analysis evaluation problems related with construction gradually becomes outstanding, numerous engineering practices indicate that: the tensile stress distribution characters has close relation with the safety stability of the tunnel. The existence of the tensile stress not only affects the deformation and destruction scope of the surrounding rock, but also has correlation with the crack spread. The paper emphases on the relation between the tensile stress characters of the tunnel surrounding rock and the crack rise and spread, the detailed contents is as follows: 1,Combined with reconnaissance and design data of Jinyu-Huinan railway tunnel and site qualitative, quantitative classification of the surrounding rock, FEM analysis and contract is carried on different instances before and after support. 2,Analyze the tensile stress distribution characters of different tunnel sections before support and after. 3,Research on the cracks distribution, adopt Griffith theory to calculate the angle between the crack and the main stress. 4,Respectively use Griffith criterion and K rule in fracture mechanics to evaluate the stability of the cracks. The results indicate that in the current stress level these potential cracks can not reach the critical condition. The tensile stress legion of the surrounding rock is stable. The innovation of this paper is embodied mainly in the following aspects: 1,Contract research on tensile stress characters before support and after. 2,Cite Griffith theory to search the cracks distribution regulation under planar stress, and evaluate the stability from Griffith criterion. 3,Adopt K rule in fracture mechanics to check the stability of the cracks, and judge the cracks will or not expand .