Research And Applicationon Of Engineering Geological Properties Of Overlying Strata Of The Coal Seam Beneath Unconsolidated Layers

With engineering geologic and mechanical properties of overlying strata of the coal seam beneath the unconsolidated layers as the starting point, the thesis systematically analyzes rock composition and structure, rock physical and mechanical features, rock hydraulic features of overlying strata, structure features of overlying strata, features of bedrock weathering zone and so on, and discusses rock mass structure types, impermeability and resistance capacity to fracture of overlying strata of the coal seam beneath the unconsolidated layers. It studys the restrictive function of rock mass structure of overlying strata of the coal seam beneath the unconsolidated layers on the mining effect by using the numerical simulation and the similar material simulation experiment. Combining with Xiyi distensible area of Longdong Coal Mine, it synthetically analyzes and predicts the developing characteristics of Two Zones in this area, and determines the mining upper limit, which provides the scientific basis for safety and high efficiency mining in coal mines. Main conclusions and cognition are as follows:1 .Under the same mining conditions, the mining effect of combined layered roofs by different lithology is different, which mainly shows that the distribution arch of principal stress in the hard overlying strata model is slightly bigger than in the soft overlying strata model, and the distribution arch of principal stress in the upper soft and lower hard model is smaller than in the upper hard and lower soft model, and the separating zone appears in strata of the upper hard and lower soft model, and the failure zone in the upper soft and lower hard model is smaller than in the upper hard and lower soft model. Mining effect of overlying strata is controlled by rock mass structure.2. Under the same mining conditions, the dip angle of coal seams have the greater influence on the height of Two Zones. The bigger the dip angle is, the higher the height of Two Zones develops. On mining methods, the height of Two Zones with slice mining is smaller than with full seam mining.3. The thinner thickness of overlying strata of the coal seam beneath the unconsolidated layers is, the greater influence of the weathering zone is, and the greater the decreased range of strenght of overlying strata. The plasticity deformation capacity is enhanced. The developing height of fractured zone is lower. The weathering zone have inhibiting function on development of the fractured zone.4.According to the data about the height of caving zone and fractured zone, the ralationship between physical and mechanical parameters of rock block and rock mass are obtained by the inversion method and the orthogonal experiment, which provides a new method for parameters determination of rock mass for numerical simulation.