Study On Influence Of Mining Deformation On Water Holding Capacity Of Cultivated Land

Mining deformation directly changes the internal structure of the surface soil of cultivated land,affects the basic physical properties,such as soil bulk density,moisture content and porosity,and then changes the water holding capacity.The change of the water holding capacity could lead to crop failure,which directly threatens the food security of China.In this thesis,clay and sandy soil in the coal-grain composite area of the Huang-Huai plain are taken as the research objects.By using methods of field experiment,statistical analysis and physical simulation,the influence of mining deformation on soil water holding capacity is systematically studied.The main research results are as follows:1.Through the field experiment,the changes of basic physical properties,infiltration and evaporation rate of surface soil in deformation areas were studied.The results show that mining deformation has changed the basic physical properties and water holding capacity of soil in deformation areas.Specifically,for the soil in the area suffered compression deformation,the bulk density increases significantly,the infiltration and evaporation rate decreases significantly,and the water holding capacity increases,while for the the soil in the area suffered tensile deformation,their changes are not significant.Soil bulk density is the main factor affecting water holding capacity and there is a significant positive correlation between them.2.By the physical simulation experiment,the influence of horizontal deformation on the bulk density of clay and sandy soil was studied.The results show that horizontal deformation has affected the soil bulk density of clay and sandy soil.Specifically,the compression deformation has a significant effect on bulk density and there is a positive correlation between them;the tensile deformation has a significant effect on the bulk density of clay soil and the bulk density decreases with the increase of tensile deformation,while it has no significant effect on the bulk density of sandy soil.The effect of tensile deformation on bulk density is weaker than that of compression deformation.3.By the field and physical experiments,the effects of horizontal deformation on water holding capacity of clay and sandy soil were studied.The results show that under the condition of continuous surface deformation,(1)the compression deformation changes the water holding capacity by affecting the soil bulk density and it is the main reason for the improvement of water holding capacity;(2)the influence of tensile deformation is weaker than that of compression deformation,inclined deformation and subsidence and it is not the main factor affecting water holding capacity and(3)the water holding capacity of the two soils is positively correlated with the compression deformation and negatively correlated with the tensile deformation.The influence of the tensile deformation on the water holding capacity of clay soil is greater than that of the sandy soil.4.The effects of fissures on the water holding capacity were studied by the physical simulation experiment.The results show that(1)the water holding capacity decreases due to fissures and the influence of fissures on water holding capacity increases with the increase of fissures’ scale;(2)the fissure(width is 2 cm and depth is 4 cm)has little effect on the water holding capacity of the two soils,while the water holding capacity of the two soils decreases significantly when the fissure’s width and depth increases to 6 cm and 8 cm respectively;(3)the fissure has more impact on the water holding capacity of the soil which is closer to the fissure and the influence begins to decrease as the distance from the crack increases and(4)the effect of fissures on water holding capacity of sandy soil is greater than that of clay soil.Therefore,the disturbance of the fissure,whose width is less than 2 cm,on water holding capacity could be ignored;the fissure,whose width is greater than 2 cm and less than 6 cm,has an influence range of 50 cm;for fissures with larger width,it is recommended to fill them in time.The thesis contains 47 pictures,23 tables and 110 references.