Study On Pressure Mechanism And Control Of Shallow-buried And Fully-mechanized Working Face In Liangshuijing Coal Mine

Based on the 42111 coal face of Liangshuijing Coal Mine,this paper analyzed the strata behavior law and weighting mechanism in shallow coal seam with thin bedrock of Yushen mining area.Theoretical analysis,physical experiment,numerical calculation and field measurement were used in the thesis.Starting from establishing stability model of overlying strata,mechanical analysis and experimental verification of roof weighting mechanism,the thesis analysed roof caving process and stress evolution characteristics.The reasonable support resistance and rib spalling preventing-and-controlling technology were analyzed.Finally,field weighting law and support efficacy were measured.Main conclusions were as follows:(1)According to field measurement of 42111 coal face,the characteristics and distribution of support resistance were analyzed.The roof length during initial weighting and periodic weighting was studied.The shallow thin bedrock mining in Liangshuijing coal mine was initially obtained.The general characteristics of field pressure appearing in the field,that is,the initial pressure is intense,there are large and small cycles to pressure phenomenon.(2)Based on the theory of key-stratum and plate,it is determined that there are two key layers of 42111 coal face on the condition of mechanics and space.The double-key-layer structure would occur composite fracture while weighting.The weighting intensity,stress distribution and the phenomenon of rib spalling were mainly affected by the features of immeadiate roof,the thickness of interlayer and mining height.(3)Through numerical simulation,it reveals the law of fracture and migration of overlying strata and the stress evolution process of surrounding rock during the initial weighting and period weighting in 42111 coal face.As working face moving forward,immediate roof,lower key-strata and upper key-strata composite fracture occurred in turn.Due to repeated loading and plastic deformation,maximum vertical stress would be 10.34 MPa and the other side about 7.5MPa.Until fully mining,the plane of basic roof and surface would diffuse to form a" bowl-shaped” basin.In the lengthwise direction of the working face,the vertical stress in the middle of the working face is obviously larger than the two ends due to the horizontal extrusion and longitudinal deformation of the rock mass at two ends,and the shape of stress distribution curve is approximately a parabola with an opening downward.(4)Through preventing composital fracture calculation and anti-sliding method and to calculate the required hydraulic support work resistance.The selected ZY12000/20/40 D two-column cover hydraulic support could meet the requirements.The adaptability of the support shows support resistance was basically distributed within the rated range,and there is a certain degree of affluence,indicating that the suppor to play a full role.The practice of 42111 face showed that the choice of support was suitable.(5)Rib spalling of 42111 working face was mainly affected by geological factors,propulsion speed,support conditions and mining pressure.The optimizing of mining process,improving of support working conditions and prevention work during key mining stage should be done.