Multifactor analysis of roof deformation and reasonable determination of the unsupported distance of a coal roadway heading face based on response surface method

This paper is aimed at the problems of multiple factors influencing the roof stability near a heading face and unreasonable values of the unsupported distance leading to a slow excavation speed. The behavior of the direct roof subsidence in the unsupported area is analyzed, and numerical simulation and the response surface method are used to study the key factors affecting the roof deformation and their interaction relations. The results indicate that roof strength is the most critical factor affecting deformation and failure, followed by soft rock thickness, unsupported distance, and support strength. The interaction analysis in Zhaozhuang Coal Mine's 33082 lane shows that it is difficult to control the roof subsidence when the unsupported distance is more than 2 m and the soft rock thickness is more than 4 m. After the unsupported distance is set to about 2 m and the support strength is increased to 0.25 MPa, the excavation speed approximately doubles, and the overall roadway is stable and controllable. By implementing field applications, the rationality of the research approach was confirmed.