Study On The Experiment Of Shear Strength And Microstructural Characteristics Of Loess Above Dongxia Coal Mine

Becaues of coal extraction,there is very serious ground subsidence above mining area of Dongxi coal mine.And the horizontal surface deformation and the vertical surface deformation caused by ground subsidence are very serious.There are a lot of ground fissure and collapse trough.Some villagers live on the top of the mining area.Landslides and other secondary disasters would threaten the villagers' life safety and their property safety.The main Quaternary sediment covers above the surface of Dongxia coal mine is loess.The coal mining subsidence area of Dongxia coal mine is this paper's research area.I use loess from the research area to do triaxial shear test designed for the undisturbed soil and the remolded soil to control content and dry density and SEM test which magnifies the undisturbed soil from 50 times to 5000 times.Then,I analyze the mechanical properties of the loess.Research indicates:(1)The content of crude clay in the loess is about 40%.The content of fine silt in the loess is about 26%.The content of crude silt in the loess is about 20%.The content of fine clay and micelle in the loess is about 14%.There is little sand grain in the loess.The cohesive forces of the loess in the natural state is 47.39 and the angle of internal friction of the loess in the natural state is 27.77.(2)The lower the position,the shear strength of the loess is smaller in vertical direction.The shear strength becomes smaller after making the undisturbed soil into the remodeled soil.(3)The shear strength and the water content are negatively correlated.The shear strength and the dry density are positively correlated.The effect of the water content on the cohesive forces is weaker than that of the dry density on the cohesive forces.The effect of water content on the angle of internal friction is stronger than that of the dry density on the angle of internal friction.(4)The loess structure is loose.The sorting of the loess particles is not good and the roundness of the loess particles is not good too.The surface of the loess particles is rough.The main relationship between particles is contact,and the secondary relationship between particles is overhead.There is a large number of intergranular pores.And there are some overhead pores and some large pores.No regularity was found in the arrangement of particles and pores.