The shallow strata structure and soil water content in a coal mining subsidence area detected by GPR and borehole data

Ground-penetrating radar (GPR) was used to study the surface soil structure and soil water content distribution before and after mining in a western coal mining area. The distribution of the strata detected by GPR was corrected using borehole geological records, and the accuracy of the soil water content detected by GPR was verified using the soil water content measured in the laboratory. The results of GPR detection and drilling shows that the shallow strata structure (< 10 m) in the coal mining area could be divided into three types, from top to bottom, as clay sand–clay–weathered bedrock structures, clay sand–sand layer structures and clay sand–sand–weathered bedrock structures. Coal mining exerts a great influence on the soil structure of the local shallow strata, but the soil structure generally remains unchanged after the recovery. After coal mining, the soil water content with the shallow strata decreases significantly, and the soil water content of the two detected samples decreases by an average of 0.0234 cm3/cm3 for the first and third detection dates (during the dry periods); the average rate of soil water content loss was 23.39%. The soil water content of the sand layers was more susceptible to coal mining than that in the clay layers. The results from the second and fourth GPR detection dates show that the cracks produced by coal mining have a certain water storage capacity and that the soil water content of the shallow strata mainly affected by rainfall. In addition, the vegetation distribution in the study area closely related to the distribution of the shallow stratum media and was of great significance for guiding the ecological restoration of this coal mining area.