Experimental Study of Deformations and Failures of the Coal Wall in a Longwall Working Face

Abstract The deformations and failures of coal wall in front of a working face cause serious mining difficulties. This paper presents the results of the physical model experiments that were conducted to study the deformation and failure process of coal seam in front of a longwall working face. In order to simulate the formation process of the bearing pressure on the roof rock seam, the special loading device was designed. The stepped loadings were applied on the top side of a sample to simulate the non-uniform loading on the coal seam. The proposed integrity coefficient was used to evaluate the failures of the coal seam. Results show that in the advancing process of a working face, the coal seam undergoes a complex fracturing process and the fracturing of coal seam is closely related to the distance from the coal wall. When the coal body is quite close to the wall of a working face, different types of fracture surfaces appear. The fracture surfaces near the front face of coal wall are tensile while the fracture surfaces away from the front face of coal wall are shear and tensile or shear. These results are useful for understanding the deformation and failure of coal wall.