Based On Three-dimensional Geological Model And Rock Strain Softening Of Rock Stability Analysis

The evaluation of reliability of surrounding rock is a momentous science research in the process of tunnel construction. During excavation, the stress in rock mass will redistribute around grotto. When this kind of stress exceeds surrounding rock's strength, surrounding rock will lose its stability and destruct. This paper is in the background of an expressway tunnel, sticks to the evaluation of surrounding rock and supporting structure. Numerical simulation and monitoring are used to consider the situation of an expressway tunnel across surrounding rock embedded weak intercalated seam. The main contents and conclusions are: (1) Based on the parameter of engineering data,3D geosciences model is created by geological modeling software GoCAD. In this way, the weak intercalated seam and the undulate mountain surface are considered. And then, the 3D geosciences model is converted to a finite element analysis model on which numerical simulation can be used. The finite element model also contains the interaction between bolt and surrounding rock and strain softening of rock. (2) With the results of numerical simulation and tunnel monitoring, it is concluded that the stresses focus on the arch lumbar and arch feet, the shear failure is easy to take place at these areas; arch vault and arch bottom are the dangerous areas during process of embedded weak intercalated seam tunnel construction. When the weak intercalated seam appears at the bottom of the tunnel, it can be considered to build inverted arch in order to limit the vertical displacement, that's an effective method to control the hump; moreover, when the weak intercalated seam appears at the arch vault, the vertical displacement will be large, it's prone to collapse, and need support timely after excavation. It is easily subjected to plastic failure at arch lumbar and arch feet, but on the weak intercalated seam, the plastic area is seriously developed, failure can take place easily.(3) The subroutine of finite element analysis software ABAQUS is used to consider the strain softening of surrounding rock. The result will be more logical if the strain softening is employed in numerical simulation. The displacement and the excavation incidence are larger with strain softening than without it. But the plastic failure area of the two situations is familiar. The result without considering strain softening is partial safe.(4) The fundamental principle and the numerical calculation method of strength reduction FEM is introduced in detail. By using strength reduction technique, the safety coefficient of stability of surrounding rock is analyzed, which is judged by dramatic increase displacement and bond of plastic strain area...