The outer drainage field of the open-pit coal mine in arid area reconstructs the mechanism of action of the upper layer of the gas-laden belt

In the open-pit mining waste dumps in arid areas, the soil structure is loose and contains a large number of rocks and boulders. The soil pores are large, the permeability is strong, and the water retention capacity is poor, making it difficult to effectively supply water to plant roots. To improve the efficiency of water absorption and utilization by plants, a proposal was made to reconstruct the soil aerated zone of the waste dump and use soil capillary action to supply water to plant roots. Soil compaction is an important factor affecting soil capillary action. To study the influence of soil compaction on capillary action, the maximum dry density and optimal water content of the waste dump soil were determined, and three groups of different compaction test schemes were formulated, which were 90%, 93% and 96%, respectively. Physical tests were used to monitor the height and speed of capillary water rise under different compaction degrees. Based on unsaturated soil dynamics and capillary test principles, a model of soil capillary water rise was established, and a numerical model with the same physical simulation scheme was established using comsol software to verify the height and speed of capillary water rise under physical simulation. Indoor planting experiments were conducted with different compaction schemes to explore the optimal soil compaction degree for plant growth under capillary water action. The results showed that there were significant differences in the rate of capillary water rise under different compaction degrees, and the compaction degree was negatively correlated with the rate of capillary water rise. The numerical simulation had good consistency with the measured values, and the height of capillary water rise was inversely proportional to the compaction degree for the same time. When the soil compaction degree was 93%, the plant growth and survival rate were optimal.