The researchers used a simulation experiment to study how cracks develop above a coal mining face in areas with thick sand and thin bedrock. They found that the height of the cracking zone above the mining face was 26 times the height of the coal being mined. The top overburden strata had specific angles of breakage, and the movement of the strata above the mining face was asymmetrical. The study also revealed a relationship between the speed of mining and the shape of the cracking zone.