Abstract: Rock mass in the excavation disturbed zone (EDZ) would be disturbed under the process of mining, and the mechanical properties and strength parameters will be deteriorated in EDZ. The main problem is how to make sure the deterioration laws of the mechanical properties. Taking the object of test stopes on induced caving roof which is based on the continuous mining method in the No.92 ore of the Tongkeng mine, based on the unloading rock mass mechanics theory, the calculation procedure is established to simulate and analyse the rock mass mechanical parameters under excavation unloading. Combined with FEM, the equivalent model of rock mass unloading is built; and the 6 steps of continuous unloading calculations are carried out. The deterioration laws of the mechanical properties of the roof rock mass unloading are obtained in underground continuous mining. The relation functions between unloading rock mass mechanical parameters and the unloading percentage are fitted by polynomial fitting method. The results show that, after the 6th step unloading, the calculation is non-convergence. It indicates that the roof has totally been destroyed and fallen. As to the rock mechanical parameters, it shows a gradual weakening trend, including the internal friction angle, cohesion and the modulus of elasticity. These values gradually decrease to 55%, 50% and 50% of the initial value. For Poisson's ratio, it gradually increase to 1.15 times of the initial value. It is demonstrated that the rock mass mechanical parameters are deteriorated under mining unloading. The dynamic analysis theoretical basis of mining mechanical response is provided by the relation functions of unloading rock mass mechanical parameters and the unloading percentage.

Key words: continuous mining, unloading rock mass mechanics, mechanical parameters, unloading equivalent model