Study On The Effect Of Coal Mining Collapse Crack On Soil Physical And Water Characteristics In Sandy Area

In recent years,with the continuous development of energy industry,the scale of China's coal mining increasing.It triggered a large-scale collapse of landform,groundwater level decline,runoff reduction,ecological and environmental problems of soil degradation has become increasingly prominent,seriously threatened the sustainable development of the economic and social life of mine production.Shigetai Coal Mine located in Shenfu Dongsheng large coal base,coal mining subsidence cracks are widely distributed in the area,in the area of cracks has important significance on soil characteristics and the effect of spatial variability of soil water.Taking Shigetai Coal Mining Subsidence Area of shallow soil(0~60 cm)as the research object,research on soil physical and water subsidence area of different fracture characteristics under variation of soil water spatial variability were analyzed.And the principal component analysis method was used to evaluate the effect of fractures on soil properties under different forms,and the following conclusions were drawn:(1)On the whole,with the crack density and width increasing,soil bulk density,water holding capacity and fine silt content decreased gradually,and the porosity,saturated hydraulic conductivity and sand content increase gradually;at the same crack(growth significantly)on both sides,the soil particle size is coarse,porosity and saturated water rate is larger at the relatively exposed side,and the soil water holding capacity,soil bulk density is larger at the relative collapse side.(2)The crack density under different conditions,with the increase of soil depth,the crack density,field capacity,silt content,maximum moisture content increased,while the porosity,saturated hydraulic conductivity and sand content showed a decreasing trend.Under the condition of different crack width,with soil depth increasing,the saturated hydraulic conductivity decreased;and the field capacity,maximum hygroscopicity.At the crack,with the increase of the distance,soil moisture increased.The soil water content at different slope positions was: slope crest < middle < slope bottom < depression of dune.(3)Principal component analysis showed: soil moisture content on the response of ground fissure is the most intense.The effect of crack density on soil physical properties as the density increased,was first decreased and then increased;in the vertical,as with the increase of soil depth changes gradually increased.The effect of crack width on soil properties was that as with the increasing width,the influence value is gradually increasing.In the vertical direction,as with the increase of soil depth changes gradually increased.(4)Coal mining subsidence cracks has great influence on the vertical variability of the shallow soil moisture,which shows the soil moisture variation in the surface layer(0cm)and bottom(40~60 cm)layer are greater than the non-crack area,while in the middle layer(10~30 cm)is less than the non-crack area,has moderate spatial variability.The spatial variability analysis of soil water content showed that,the soil moisture content has a strong spatial correlation at the surface soil,while the deep soil moisture distributed unevenly and keep a moderate spatial relation.The range of soil moisture content in each layer(0~60 cm)was between 30 m and 50 m.And the low value of soil moisture content are located in the collapse crater of subsidence area.