Experimental Study On Shear Strength Of Fissured Loess

The coal resources in the loess area are rich.Shallow coal seam and thin bedrock covering layer are favorable for mining.But the loess cover layer is thick and the terrain is undulating.The underground coal mining will inevitably cause the ground collapse,which causes the integrity of the loess to be destroyed and easily lead to the loess landslide disaster.In the analysis of the loess landslides caused by underground mining,in addition to the relationship between the surface movement caused by mining and the deformation of the slope,the problem of strength deterioration caused by the fissured loess must be considered.Based on field investigation and soil test,the indoor preparation scheme of fissured loess is put forward.The shear strength law of fractured loess with different fracture density and different fracture occurrence is studied under the condition of different water content.The main results are as follows:(1)Based on the causes of the Aeolian Loess and the characteristics of the fissure of the Loess caused by coal mining,a set of indoor preparation methods for different fissure density and fissure occurrence is put forward by the methods of soaking and compacting the dust of the loess,making the crack surface of the Loess by thin steel wire.(2)Through three axis tests of loess with different fissure density,it is concluded that:In general,with the increase of fracture density,the internal friction angle decreases.Cohesion is decreasing at low moisture content(less than 12%)and decreasing first and then increased trend at 16% water content.However,cohesive force varies little with fracture density at 20% moisture content.(3)Through the three axis test of different fissure loess,it is found that the internal friction angle increases with the increase of the angle between the fracture and the shear fracture surface of intact loess,but the cohesive force has no obvious law.(4)The deformation and failure characteristics of fractured loess are influenced by the factors such as fissure density,fissure occurrence,water content and confining pressure,and the type of deformation and failure has an important influence on the strength of the fractured loess.(5)Considering the effect of cracks on the strength degradation of loess,the stability of coal mining slope declined significantly.