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Abstract The macro-crack distributed in the rock mass continuously worsened after excavation，which may resulting the crack connect to each other and form macroscopic fracture in some areas，and could make the slope become unstable. The slope excavation process of each step is equivalent to the process of applying a distributed load in the excavation face and gradually reduced to zero. During the process of equivalent excavating the slope，the crack near the slope free surface within a certain range will be in the state of tension-shear stress. Based on the continuum mechanics，and combining with the damage mechanics and the fracture mechanics，the constitutive model of damage evolution are solved under the tension-shear stress state. The macroscopic bulk modulus are used to reflect the damage degree of rock，and the destruction degree are defined to represent the destroyed characterization in the actual rock mass. Based on the principle above，The calculation of fractured rock unloading damage model is programmed by using the interface of the FLAC3D. The excavation simulation of Guangxi Fengshan limestone building material mine is studied by the new model. The results of the displacement values and the plastic area under two conditions which are using and do not using the new model are calculated and analyzed. The validity of the new model are proved and the real situation in the slope are more accurately reflected. Using the destruction degree to indicate the damage of the rock mass can be more intuitively and accurately determined the rock mass stable state are proved by comparative analyzing the damage degree and the destruction degree after excavating the rock slope.
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2015, Vol. 34 
