Effects Of Clay Mineral Content On Soil Shear Strength

As a typical soil erosion phenomenon,the study for soil shear strength of Granite collapsing hill could help us to understand the development of mechanism of Granite collapsing hill wall,it has practical significance to the management of Granite collapsing hill.According to the characteristics of soil can be divided into red soil,sandy soil layer and detritus layer.This study chose three soil layers of soil layer of typical Granite collapsing hill as the research object in Anxi County,Fujian Province.By adding clay mineral as well as setting the moisture content gradient,then took the soil samples to direct shear tests and the SEM,studying under the different condition of moisture content,the relationship between clay mineral content gradient and soil shear strength from the macroscopic and microscopic.The results showed that:(1)By observing the microstructure of soil particles under the different gradient and discussing the change rule of inner friction angle and cohesion of remolded soil.Clay minerals with negative surface can be embedded in acicular iron oxide which has aggregation structure could improve the cementation;The clay mineral effect on particle adhesion to form relatively stable aggregate structure,the coupling effect can increase external force against outside forces which can damage its destruction.Through the SEM,we can not only observe the micromorphology of clay minerals embedded in soil particles but also the condition of Clay mineral covering the surface of soil particles.It can explain and prove the conclusion that achieve from Indoor direct shear test is correct.(2)Simulation of natural conditions,setting the moisture content of 20%,the soil shear strength of red soil layer is increased with the growth of clay mineral content gradient,but under the different gradient,there has the difference between the shear strength growth.Under the gradient of 10:1,the soil shear strength of red soil layer has a significant growth,to further increase the content of clay mineral is going to level off;For the same moisture content of sand layer,the shear strength is increased with the growth of clay mineral content gradient,it also has the maximum growth at the gradient of 10:1,but the growth of shear strength of sandy soil layer is slightly smaller than red soil layer;In contrast,under the condition of moisture content of 20%,the soil shear strength of detritus soil layer of Granite collapsing hill is increased with the growth of clay mineral content gradient.Growth in different clay mineral content gradient is relatively uniform,no specific gradient as well.The influence of inner friction angle and cohesion by Clay mineral made common decide characterization of the shear strength.However,the influence degree is limited by soil nature itself,under the same gradient,Variations in the soil shear strength of each soil layer are different.(3)Consider strong rainfall and improve the moisture content gradient to 25%,30%,under the high moisture content,in order to explore how the soil shear strength of three soil layer change with the growth of clay mineral content gradient.Under the same moisture content,as the clay mineral content increased,the shear strength increase as well.To compare the influence of different moisture content on the shear strength under the same content gradient,,The results showed that:moisture content of 20%>moisture content of 25%>moisture content of 30%.The moisture content is the dominant factors influencing the shear strength of soil of Granite collapsing hill,clay mineral content increased weaken the effect of moisture content which reduce the shear strength.Under the effect of moisture content.Shear strength of each soil layer of Granite collapsing hill showed a trend of collapse,with the increase of clay mineral content gradient,the decline has been control by different degree,it has practical significance to the management of Granite collapsing hill through improve clay mineral content gradient..