Study on deformation law and breaking span of main roof of isolated working face based on thin plate theory

Abstract

To study the deformation and fracture laws of the main roof in three-side annular island working face, the MZ201 working face of a coal mine in Henan Province was considered as the research background, and a main roof breaking mechanics model was constructed by using the small deflection bending theory of elastic thin plate. The fracture mechanics features of the main roof of the island working face were analyzed, and the initial pressure and periodic pressure breaking span of the basic roof were obtained. The results show that the deformation of the main roof is small during the initial pressure, and the maximum roof subsidence is 360 mm in the middle rear area of the goaf. During periodic pressure, the deformation of the main roof is large, especially in the center of the roof, and the maximum roof subsidence is 807 mm. The tensile failure of rock strata first occurs from the middle of the two long sides at the first breaking. During periodic breaking, the rock strata starts to break from the center of the rock strata bottom, develops continuously along the dip direction, forks at the near end of the short side, which contributes to the “X” type breaking. Based on the tensile stress fracture criterion, the initial breaking span and periodic breaking span of main roof were obtained with 49.3 m and 27.9 m, respectively, which is closed to measured results on site.

Keywords

• elastic thin plate theory
• isolated working face
• main roof
• breaking law
• breaking span