Damage-plasticity Coupled Model For Jointed Rock Mass To Subsidence Control And The Technology Of Goaf Stowing With Cement Materials

Mining subsidence is a complex mechanical process occurred in overburden rock. The mechanical behavior of overburden rock, such as anisotropy, nonlinearity and heterogeneity is generally associated with the existence of a great deal of cracks and their propagation. The work of this paper focuses on two aspects: 1. The mechanical model for subsidence and its application This paper establishes a damage-plasticity coupled model for rock-like material in the frame of irreversible thermodynamics. Second order damage tensor is adopted and the effect of crack-closure is taken into account. Based on the micro-mechanical analysis of representative element consisting of cracks, the orthotropic damage tensor is introduced into the Mohr Coulomb criterion through homogenization. Both the degradation of shear strength and degradation -of friction angle caused by damage are inclUded in this model. Witlr-thetheory establishediii this paper, the nunieric simulation program of FEM for mining subsidence calculation is improved and applied it to mechanical analysis of mining subsidence in some coal mine. By contrasting between the calculation results and the observation datum, it is proved that the program is dependable when applying it to. The strata movement is researched by means of physic-al simulation and FEM of this paper. Z Subsidence control technology The technology of goaf stowing with cement materials, including filling materials, cementing medium, filling system etc. are studied. The component of the filling slurry and the mechanical properties of its harden body are also experimented. China currently produces about 20 million tons coal combustion by-products annually (including fly ash, bottom ash, and wet and dry scrubber sludge) from coal-burning electric power plants. The utilization of fly ash is only about 40%. Accordingly, large volume of fly ash can be utilized as filling materials. Therefore the back-filling method in which the fly ash is the bases of filling materials has significant potential both to control mining subsidence and to manage the fly ash.