Scale-Model Experiments on Stress Changes with Longwall Coal Mining.

Two types of scale-model experiments were conducted to investigate the strata mechanics around the face with longwall face advance.For this study, three-dimensional 1/200 scale models with one and two longwall faces were fabricated to represent the typical longwall panels in the central district at-660 m sea level of Taiheiyo Coal Mine.During these scale-model experiments, the changes of vertical stress with face advance and the plofile of collapsed layers above coal seam was observed.Also the data obtained from the experiments were compared with the data from in-situ measurement at Taiheiyo Coal Mine.Results were as follows:The relative distribution of the peak abutment stress in longwall face was obtained.When the face advances equal to the longwall length, it is expected that the peak abutment stess becomes the largest at the center of the face line.Moreover, the peak position of the abutment stress exists within about 50 meters behind the face.It seems that a vertical section of the collapsed area in the goaf will be approximated by a trapezoidal shape.The coal pillar formed between adjacent two longwall panels suffers from the double large stress changes with the face approaching and passing.