Fracture distribution and deformation characteristics of overlying strata in an abandoned gob under single coal seam

After a coal mine is closed, a large amount of gas resources remain in the abandoned gob. The cavities and fracture of the overlying strata in the abandoned gob are the main places for gas storage and flow. The fracture distribution and deformation characteristic of the overlying strata have significant effect on the gas migration of the abandoned gob. The mining similarity simulation test device of a plane stress was used to study the fracture distribution and deformation characteristic of overlying strata in an abandoned gob. Results show that the caved strata of the abandoned gob formed a trapezoidal distribution, and the caving range decreased gradually as distance from the coal seam increased. The caved strata on two sides were dominated by horizontal fractures, whereas the caved strata in the middle were compacted. Large numbers of cavities and vertical and horizontal fractures were observed near the start and end mining positions. The development degree, quantity, and connectivity of the fractures near the end mining position were larger than those of the fractures in the start mining position. The caved strata on two sides moved toward the middle of the abandoned gob and showed tensile deformation. The caved strata in the middle moved downward and showed compression deformation. The subsidence, horizontal movement and deformation, inclination, and curvature of overlying strata decreased gradually as distance from the coal seam increased.