Research and Practice on Filling Technology of Fully Mechanized Coal Mining Face through Trend Abandoned Roadway

Taking the fully mechanized mining face (FMMF) through the abandoned roadway (AR) in a coal mine in Shanxi Province, China as the engineering background, the field investigation, theoretical analysis, numerical simulation and field test were comprehensively used to study the instability mechanism of the trend AR. The deformation and failure evolution of the trend AR roof were deduced into four stages: initial deformation, bending and separation deformation, fracture failure, and collapse destruction. The high span ratio proved to be the key factor affecting the stability of the trend AR, and the control principle of timely support and reduction of roof span should be followed for controlling the roof of trend AR. Comparing the traditional method through the trend AR with the perspectives of technological and economic benefits, the technology of filling and controlling the trend AR with the high water material over in the FMMF was proposed, and the effect of the filling body on the roof of the trend AR was revealed. The key parameters of the filling body were identified: the strength of the filling body is 1.0 MPa, and the water-cement ratio corresponding to the high-water material is 8:1. Based on this information, the process of the trend AR filling was designed systematically. Industrial tests show that during the FMMF through the trend AR, the roof was effectively supported by the filling body and the normal coal mining was not significantly affected, so the safe mining of coal resources was guaranteed.