Influence of soil overburden thickness on water infiltration and evaporation characteristic in post-mine restoration

Exploitation of coal mining is an important part for economic development, but the exploitation of coal mining will bring a serious impact on the local ecological environment. Ecological restoration is an effective method to improve the ecological environment in the mining areas. The first step of ecological restoration in post-mine is  to rebuild a sustainable mine-soil system. Fine soil overburden is often used in reconstructing soil profiles to provide habitat for vegetation restoration. Fine soil overburden will change the infiltration and evaporation of soil water. However, the understanding of the infiltration and evaporation of soil water is still an ongoing challenge. In this study, four groups of clay soil thicknesses (25 cm, 20 cm, 15 cm and 10 cm) were set up to simulate the overburden fine soil in post-mine ecological restoration, to study the influence of cover fine soil thickness on soil water infiltration and evaporation. The results showed that: a) the correlation between cover clay soil thickness and wetting front migration velocity was negative, namely, the thicker the cover clay soil thickness, the slower the wetting front migration velocity, and the smaller the average infiltration velocity is. However, the amount of water holding in thick overburden clay soil was more than the thin overburden clay soil. b) The overlying clay soil would improve soil water evaporation, but it wasn’t significant(p>0.1) with the thickness. The amount of soil water evaporation was low than the amount of water infiltration in thick overburden clay soil, so, the thick overburden soil could hold more water for the vegetation utilization. c) With the progress of soil water evaporation, the rate of evaporation was decreased with the increase of clay soil cover thickness. The greater the soil cover thickness, the stronger the soil water retention capacity. From the experimental result, the thick clay soil cover could remain more water, and is more suitable for vegetation establishment in post-mining restoration.