Study On The Mechanical And Microstructure Properties Of Solidified Heavy Mental Contaminated Expansive Soil With The Cement

It has a wide range of expansive soil in China,along with the development of economy,the extent of the expansive soils are polluted by heavy metals become serious at some areas.Useing the cement to solidified and repaired contaminated expansive soil,it has a great significance to control environmental pollution and to use the soil again.This article select heavy mental ions(Pb²⁺,Cd²⁺)and expansive soil that from Nanyang,the consolidation agent is cement,useing the basic soils tests,the physical and mechanical properties of contaminated expansive soil are analyzed under the different amount of cement,different heavy mental content and different curing age.The change rule of micro-structure of contaminated expansive soil are analyzed by through the ray diffraction and scanning electron microscope.The main research contents and conclude are as follows:Through the tests of physical property,the change rule of physical properties of the consolidated contaminated expansive soils are analyzed.The research show that the dry density is increased,liquid plastic limit is decreased after adding heavy mental to expansive soil,and the dry density increased continued with the concentration increase of heavy mental.After adding cement,the dry density decreased and liquid plastic limit are increased with the content of cement,the liquid plastic limit and cement contend increase linearly,and it improved obviously of the swell-shrink characteristics;After unconfined compressive strength and direct shear tests,It can be obtained that strength decreased obviously after the heavy mental adding to the expansive soil,and the cohesion,friction angle are decreased with the concentration of heavy mental increase.After adding the cement,the mechanical properties of contaminated expansive soil improved obviously,the strength and the cohesion,friction angle are increased with the cement content and curing age increase.The rate of change is different,the increase rate before 9%of cement content is great,the increase rate after9%of cement content is small,but it is risen continued;Through the scanning electron microscope and XRD tests,the structure of the clay mineral of the expansive soils polluted by heavy mental has been changed,along with the concentration increase of heavy mental(Pb²⁺、Cd²⁺),the particle of soil become loose and pores become larger.After adding cement,the surface of the expansive soil formed gelling substance,the pores between the soil particles are filled with the hydration product,pores become smaller,pores are gradually decreasing,the particles become compact,the strength of soil increased;The change rule of micro-structure is consistent with that of macro-structure.