| Abstract: | Surface displacement caused by underground coal mining is influenced by many factors such as the depth and thickness of the coal seam and joints in overburben rocks. Extensive efforts have been devoted to the ground surface displacement. Nevertheless, the joints have not been taken into consideration for a long time. In fact, there exist numerous joints and cracks in rocks.As a result, the joints in overburden rocks have to be taken into account. The joints in rocks can be treated as initial damage theoretically. In this paper, two kinds of physical model, one containing no initial joints and anotber containing some initial joints, are employed to systematically investigate effecs of initial joints on surface subsidence. Moreover, within the framework of damage mechanics, the statistical relationships between the characteristic value for surface displacement and damage variable are obtained. |
