Study On Soil Property Change Caused By Mining Subsidence In Loess Mining Area

The Western Loess Plateau and its transitional zone are one of the major coal production bases in China.The Loess mining area has complicated environmental geological conditions,vertical and horizontal ravines,and the thickness of the soil layer accounts for 30-70%of the mining depth.Over the years,underground large-scale coal mining has caused serious geological disasters such as surface subsidence and ground fissure,slope collapse and landslide.The study of the changes in the characteristics of the surface loess layer caused by underground mining and overlying strata disturbance is of great significance for revealing the mechanism of mining subsidence and derived geological disasters in the Loess mining area,and promoting the disaster prevention and disaster reduction in the western mining area and the safe production of the coal mines.The surf soil layer in the Loess covered mining area has significant structural characteristics and certain collapsibility,and its physical and mechanical properties are different from the clay layers in the middle and eastern mining areas.The thick loess layer produces dynamic load effect on the overlying bedrock during the mining subsidence,which leads to the particularity of the open mining subsidence law in the Loess mining area.On the basis of the present research results of mining subsidence in the Loess mining area,the basic characteristics of the surface movement deformation in the Loess mining area are analyzed on the basis of the measured data of the mining subsidence in the typical loess gully area.Based on the experimental model of geological and mining conditions in the mining face of bingchang Yan Jia River coal mine,the FLAC numerical simulation,similar material simulation experiment and soil mechanics theory are used to study the volume deformation and the additional deformation distribution characteristics of the mining soil unit,and the shear failure mechanism of the mining yellow soil layer and the surface mining crack are analyzed.The formation mechanism of the seams is formed,and the effect of the load effect of the self weight of the loess layer on the subsidence of the bedrock mining,the mutual feed mechanism of the soil layer and the bedrock layer in the mining subsidence,and the influence of the change of the terrain slope on the surface deformation characteristics are revealed.In the mining area,the field sampling is carried out,the degree of soil disturbance is expressed by the change of soil dry density,and the physical and mechanical indexes of the loess samples with different disturbance degrees are obtained through the geotextile experiment,the relationship between the soil dry density index and the physical and mechanical parameters of the soil is established,and the mining subsidence and soil are revealed.The changes of physical and mechanical parameters caused by the deformation of the soil can provide technical support for landslide control and early warning in the Loess mining area.