Experimental Study And Formation Mechanisms On Soil Water Movement Of Unsaturated Zone In Coal Mining Subsidence Area Of Huainan

The unsaturated zone is a necessary way to groundwater and atmosphere,hydrosphere contact surface,is also an important part of natural water circulation system.However,in the coal mining subsidence area,the fissures caused by the subsidence process destroy the unsaturated zone soil structure,leading to the change of the soil hydraulic parameters,which affect the process of soil water movement.Therefore,it is necessary to carry out the study of water movement in unsaturated zone of coal mining subsidence area.This paper consults the domestic and foreign theory of soil water movement and subsidence mechanism analysis,taking subsidence area of PanJi NO.1 mine of Huainan city as the research object,the soil water movement and formation mechanism of unsaturated zone in coal mining subsidence area were studied by field sampling,physical simulation in laboratory and in situ field experiments.The main results are as follows:1.Determination of related parameters of field sampling,analysis showed that the subsidence fissures have an important impact on the soil water characteristic curve and unsaturated hydraulic conductivity.Compared with the non subsidence area,The slope of the soil water characteristic curve and the unsaturated hydraulic conductivity of the soil are reduced due to the subsidence.The soil is more likely to release water,and the soil water conductivity is decreased.2.Subsidence caused subsidence area of low-lying,which is easy to form the catchment area,and soil water content of the subsidence of unsaturated zone is generally higher than that of non subsidence area.And the vertical development of the fracture has not the role of transmitting water and is conducive to the effective supply of groundwater.At the same time,the water content of unsaturated zone in the subsidence area changed differently under the change of rainfall,evaporation and groundwater level.3.The results of laboratory simulation test show that the soil moisture content is reduced due to the subsidence in two-dimensional soil column experiment.In the one-dimensional soil column experiment,the design of two different types of soil under the conditions of the subsidence fissures are different,so that the performance of different infiltration capacity of the soil.Under the action of subsidence,the fissures of sandy soil are more than those in clay soil,which increases the effective supply of groundwater table under the rainfall condition,and reduces the soil water content under the evaporation condition.4.The numerical simulation analysis of unsaturated soil water movement mechanism shows that the different soil water transport mechanism makes the soil profile in the subsidence area and the non subsidence area different.Under the rainfall condition,the upper soil water content is higher than the non subsidence area,but the deep soil is the opposite.The water content of the whole section of the subsidence area is higher than that of the non subsidence area under the evaporation condition.The water content of the whole section of the subsidence area is higher than that of the non subsidence area under the evaporation condition.When the groundwater level rises,it helps to preserve the shallow soil in the subsidence area.