Experimental Study On Physical And Mechanical Properties Of Unsaturated Expansive Soil In Hefei Area

Expansive soil is unsaturated soil,which is a special kind of soil.It is characterized by the expansion and shrinkage,multi fracture,super consolidation.Expansive soil is distributed all over the world,and it has different degrees of harm to all kinds of geotechnical structures.Therefore,the study on the physical and mechanical properties of unsaturated expansive soil is carried out,and the creep equation of unsaturated expansive soil is established.Blackwater Dam Park,Hefei South Station rail transfer center,Silihe bridge area expansive soil were chosen in this paper as the research object,a series of laboratory tests are carried out.Expansive soil physical index test,including moisture content test,density test,liquid plastic limit test;expansive soil swelling shrinkage test indexes,including free expansion rate test;expansion test of mechanical properties of soil,including anti uniaxial compressive strength test,uniaxial compression creep test.Through the experimental data,combined with the relevant academic materials at home and abroad as the theoretical guidance,the work of this paper is successfully completed.The contents are as follows:(1)through a large number of research: summary in Hefei expansive soil distribution,age and cause of formation;analysis of Hefei expansive soil micro structure and macro structure;exploration of expansive soil in Hefei area expansion and shrinkage mechanism and influencing factors;draw of Hefei expansive soil swelling shrinkage index distribution chart.(2)expansion test of physical and mechanical properties of soil strictly according to the soil test specification ",through a lot of experiments,the author familiar with and master the test operation steps and in the original test procedure,to free expansion rate test and the improved method are put forward,such as the sample particles are finer screening;soaking before the test,soak for at least 24 hours;stirring 3 times.Try to reduce human factors and improve the accuracy of the data.(3)according to the uniaxial compression strength test of expansive soil,explore the ultimate compressive strength of expansive soil in Hefei area,namely the limit of average compressive strength in the vicinity of 400 MPa.To understand the change trend of the residual strength of expansive soil,analysis of expansive soil stress-strain relationship,found that the expansive soil stress-strain relationship is divided into three stages: elastic stage,nonlinear and strain softening stage.(4)with expansive soil uniaxial creep test results analysis,expansion deformation characteristics and influencing factors of soil creep and explore for Hefei unsaturated expansive soil creep constitutive equation and different moisture content,in minor principal should stress,creep curve was linear change;the LORD shall force,creep curve is logarithmic change.Figure [33] Table [19] Parameter [20]...