Abstract:

The stability of the block of free face during tunnel excavation and the stability of the block under the condition of structural surface with cohesive strength are very important. Hence, the cohesive force model is used to simulate the tensile strength and cohesive strength of the filled and cemented structural surfaces and the corresponding sliding and detachment behaviors. The block selected from a typical granite area in Beishan, Gansu, as well as the structural surface parameter interval obtained are used to study the stability of block by 4 schemes; meanwhile, the influences of initial ground stress and secondary ground stress induced by excavation are considered. In scheme 1, the tensile strength and cohesion strength are given by a small value so as to analyze the stability of the block under the influence of friction stress on the structural surface. In the other three schemes, the possible instability of block at different positions is considered respectively, and the stability of the block is analyzed by adjusting the tensile strength and cohesive strength of different structural surface of block. The analytical results show that: the cohesive force model can simulate the tensile strength and cohesive strength of the filled and cemented structure surfaces commendably, and can simulate the sliding and detachment behavior of the structure surface as well, which can be used as a tool for block stability analysis and calculation; in addition, the results can provide a new idea to simulate the progressive development of cemented structural surface damage with time.

Key words: tunnel, cohesive force model, cemented structural surface, tensile strength, cohesive strength, block stability