Numerical Simulation of Development Characteristics of “Two Zones” of Repeated Mining at the First Face of Shallow Mining Area

In order to explore the high development characteristics of caving zone and water flowing fractured zone (that is, the “two zones”) in the first mining face of the shallow mining area under the deep loose layer of Baodian Coal Mine, based on the comprehensive analysis of the regional geology, hydrogeology and mining conditions of the first mining face in a mining area, four engineering geological models with different bedrock heights were established, and FLAC^3D software was used to simulate the influence of only considering different bedrock heights on the height of the two zones under the same conditions. Through comparative analysis of the plastic zone, it is found that repeated mining does not increase the height of the two zones, but obviously increases the degree of influence.