Movement mechanism and analogous hyperbola model of overlying strata with thick alluvium

A large number of field engineering practice indicate that the movement of thick alluvium rock strata has a large difference with that of bedrock. At present,the rock strata movement laws mainly focus on two aspects. Strata control above working face mainly researches on the fracture and movement laws of roof rocks with a certain height at one side. However,the geology and survey engineering mainly researches on the subsidence laws of surface thick allu- vium at another side. In this paper,the authors try to combine the two research areas and develop a new rock strata movement model,which can accurately reflect the true movement law of overlying strata. Based on the initial and peri- odic fracture mechanical models of bedrock,the distribution of principal stress and the fracture trace have been ob- tained. And the inverse funnel-shaped failure mechanism is the main failure mechanism of deep bedrock. The funnel- shaped movement mechanism of shallow thick alluvium has been discussed in detail based on probability integral method and shear-slip theory. Combined the two aspects of researches,the paper proposes that the movement of overly- ing strata with thick alluvium has the feature of analogous hyperbola. In addition,the analogous hyperbolic movement model is proposed to characterize the movement of overlying strata with thick alluvium. The new model can be used to predict overlying strata’s subsidence range. The Mining Discontinuous Deformation Analysis ( MDDA) has been de- veloped and applied to simulate the movement of overlying strata with thick alluvium. Numerical results indicate that the analogous hyperbolic movement laws can also be founded,which is approximately consistent with the theoretical model.