Instability mechanism and control method of energy-reducing for roadside support in deep gob-side roadway

The energy accumulation and sudden release of the roadside support body caused by the fracture and subsidence of the lateral main roof are one of the causes of instability and failure of surrounding rock in the deep gob-side roadway. Taking the working face with a depth of 1 000 m in the Suncun Coal Mine, Taian, shandong Province as the engineering background, the energy evolution law of the surrounding rock of the gob-side roadway under the actual engineering conditions was obtained by the UDEC discrete element numerical simulation software. Also, the influence characteristics of factors such as the width of the roadside support body, the thickness of the lateral main roof and the fracture length on the energy evolution law of gob-side roadway were obtained. Therefore, based on the arc triangular plate structure of the transverse fracture edge of the roof, the mechanical model of the lateral roof structure of the gob-side roadway was constructed, and the mechanical state of the roadside support body in different mining stages was analyzed. The dynamic instability mechanism of the roadside support body caused by the fracture and subsidence of the lateral main roof was revealed, and the energy criterion of dynamic instability N of the support body was obtained. Based on this index, the control method of energy-reduction of the stability for roadside support body was proposed, which was "reducing external impact energy + changing internal bearing capacity". When N ≥ 1, the sum of the storage energy of the elastic zone and the new increased deformation energy brought by the fracture of the lateral main roof is greater than the energy consumed by the complete crushing of the plastic zone of the roadside support body. At this time, the elastic energy accumulated in the support body is large, the self-bearing capacity of the support body is insufficient, and the support body will undergo dynamic instability, and when N<1, the support body will not occur dynamic instability. Field practice shows that the energy criterion of dynamic instability established is consistent with the actual results. After adopting the control method of energy-reduction, the maximum values of the displacement of the roof and floor and two sides were 114 and 123 mm, respectively, and the relative force of anchor cable was finally stabilized at about 50 kN. The impact failure phenomenon of the support body was basically eliminated, the stability was obviously improved, and the control effect was remarkable.