Numerical simulation of the influence of coal mining subsidence cracks on the moisture migration law in the vadose zone

Coal mining subsidence cracks affect the moisture migration law in the vadose zone, inducing ecological and geological environmental issues in mining areas. Current research focuses on the influence of subsidence cracks on the moisture content in the vadose zone, often overlooking the impact of subsidence cracks on the direction and speed of the moisture migration. Therefore, considering the width of cracks, crack density, and soil texture types, a numerical model of moisture migration in the vadose zone of coal mining subsidence areas was established based on HYDRUS 2D, to study the law of moisture migration under the influence of coal mining subsidence cracks. The results show that when there is a single crack, the difference in moisture content is positively correlated with the crack width. The direction of soil moisture movement is diverted towards the crack, and the closer the region to the crack at the same soil depth, the greater the diversion angle. The maximum diversion angle and the size of the region where the direction of movement changes increase with the widening of the crack. The difference in average moisture movement velocity between the crack edge and the region far from the crack increases with the crack width. With an increase in crack density, the moisture content at the same soil depth decreases, and the maximum diversion angle between regions between cracks and the occurrence of diversion decreases. Under the influence of coal miming subsidece cracks, the molsture content of loam is higher than that of aeolian sandy soil, and the moisture migration speed is lower than that of aeolian sandy soil, but the soil texture type does not affect the direction of moisture migration.