Experimental Study On Infulence Of Cement Content On Strength Characteristics Of Consolidated Soil

With the development of the country and the rising of the economic level,in the construction of projects,the potential safety hazards caused by the deformation of soft soil and insufficient strength are often encountered.Red clay is a kind of high plastic clay with multi-fissures,strength attenuation and sensitivity to environmental temperature changes.It has the characteristics of high water content,low natural density and large pore ratio.Sandy soil is a kind of soil with high sand content in soil particle composition.Because of its loose structure,it is easy to corrode,scour and liquefy.Red clay and sandy soil are widely distributed in Hengyang area with frequent rainfall and large rainfall.Therefore,it is often necessary to reinforce and improve the soil,improve the engineering properties of the soil,and improve the mechanical strength of the soil to meet the requirements of buildings.Taking red clay and sandy soil of a town in Hengyang as raw materials,using the technical principle of cement strengthening soft soil,and taking the influence of large amount of cement on the mechanicalstrength index of consolidated soil as the breakthrough point,the following problems are discussed through laboratory tests.The concrete contents are as follows.(1)Explain the current development and application status of cement soil in engineering.(2)Study the unconfined compressive strength of red clay and sand after cement.Discuss the influence of different cement incorporation ratio on soil compressive strength.(3)Through the direct shear test of cement-soil in laboratory,study the stress-strain curve,normal stress-shear stress curve and shear strength mechanical index of cement-soil specimens with different cement mixing ratio,and obtain the change rule of cement-soil with cement mixing ratio.At the same time,study and analyse the failure characteristics of cement-soil specimens after shear.Based on the results of laboratory tests,obtain the following main results:(1)With the increase of cement content,it increases gradually the unconfined compressive strength of cement-soil.(2)With the increase of cement content,it appears gradually the peak stress drop phenomenon on the shear stress-shear displacement curve of red clay consolidation.The shear strength index of red clay consolidation increases with the increase of cement content,but the lawof increasing cohesion is different from internal friction angle.The increasing rate of cohesion decreases with the increase of cement content,and the increasing rule of internal friction angle presents "S" type with the increase of cement content.(3)The residual strength and peak shear strength of cement-soil are improved obviously after adding cement curing agent into sand.With the increase of cement mixing ratio,the cohesion increases first.When it reaches 1:2,the cohesion growth rate tends to zero,and even decreases when it reaches 1:1.The internal friction angle increases continuously with the increase of cement mixing ratio,and the growth rate increases.(4)Through shear test of cement-soil specimens,there are three phenomena in shear process: bond failure,slope climbing effect and shear effect.The main reason for these phenomena is that the normal stress applied on the shear plane of soil is different.When the applied normal force is small,the shear surface of cement-soil will appear bond failure,slope climbing effect and other phenomena.When the applied normal force is large,the shear effect appears on the shear surface of cement-soil.