矿业科学学报 (Apr 2017)
Research on roof fracture criterion and moving rule of gob-side entry in shallow seam
Abstract
Based on the characteristics that horizontal pressure between rocks is too small to form masonry beam after roof fracture in shallow-buried coal seam, the retaining gob-side entry fracture structure formed by falling down cutting roof.It was established that fracture mechanical model of lower slitting and upper bending cracks bilateral cantilever beam.The cutting-top working resistance was derived as the lateral basic roof fracture extends along the cracks of the cutting seam structure.The numerical model of surrounding rock structure under two fracture states of lateral basic roof was built.The movement and deformation law under two states of fracture structure indicated:When the cutting resistance is low, the roof breaks along the coal wall inside certain depth.The pour terraced cantilever beam of arc triangle direct roofs in emptied stope, can transfer large fracture dynamic load and overlying strata movement pressure along emptied roadway surrounding rock.With the unit cutting action of high shear resistance and cutting seam, the direct roof of caving zone and low basic roof were cut to slide along the cutting seam structure.It could reduce the structure length of transferring the overburden strata load from the side of arc triangle hanging deck, and optimize the roof bearing structure and surrounding rock stress, and also could reduce the additional load bore by the support body in the roadside by implementing active control of roof fracture state.At the same time, the hulking of waste rock could fill the empty area and make the overlying rock contact point move forward, and slow down the sinking and rotational deformation force of overlying rock.In the condition of the shallow seam and thin bedrock of Halagou mine, the observation of cutting large cross-section compounded roof experiment indicated that:advanced slitting on gob-side roadway can reduce support working resistance of lateral roof and immediate roof caving step distance.It could also reduce the roof fracture dynamic load caused by rock plate breakage.The actual cutting resistance dovetailed with the theoretical calculation results.
