Variation of water and air in reconstruction soil profile and its response to temperature gradient in coal mine area

There are a large number of engineering projects that use coal gangue as a substrate for ecological en-vironment restoration and land reclamation in coal mine area.However,the process of coal gangue oxidation and heat release will affect the water and gas changes in reconstruction soil profile,which can affect the effects of ecological restoration.An experimental simulation system in laboratory for studying water transport and gas-heat diffusion of the reconstruction soil was designed to study the characteristics of water and air movement of recon-structed soil and its response to temperature gradient.The system could be used for constantly measuring soil content,temperature and soil CO2 concentration by laying sensors and detectors in different depth of reconstructed soil and heating the reconstruction soil at the bottom to study the influences of gradient temperature on water and air movement.The results showed that the Hydrus-1D software could better simulate the water content distribution in reconstruction soil.However,the water infiltration process had an obvious hysteresis,which leaded to water accumulate in the soil layer.The gas also showed an obvious hysteresis during the diffusion process,which accumulated in gangue layer at 80 cm.When the bottom was heated,the reconstruction soil profile will form a stable temperature gradient.Under the action of temperature gradient,water moved up from the bottom,leading to a significant decrease in the water content of the bottom layer,while the water content of other layers increased significantly in the reconstructed soil.Among them,the water content of the 60 cm layer was fastest growing at 0.057%/h.In addition,the air accumulated in the coal gangue layer and the interlayer interface,and the cumulative effect increased with the temperature gradient increase.Temperature and water content all can affect the air diffusion in the reconstruction soil,but the increase of temperature gradient will weaken the influences of water content on the air diffusion.In addition,there may be a “barrier belt” in the interlayer interface of the reconstructed soil.Thus,water and air are blocked,causing the accumulation of water in soil layer and air in coal gangue layer and interlayer interface.