Research On Permanent Deformation Prediction Of Clay Of High Liquid Limit In South Hot And Humid Areas

With the rapid economic development,the service function of the road has been put forward higher requirements with the massive increase of traffic.As the basis of pavement structure,subgrade must have sufficient strength and stability to keep good road performance.Therefore,research on deformation behavior of subgrade soil under the repeated load is particularly important.In the southern humid and hot region of China,the equilibrium moisture content of subgrade is higher.Study on the subgrade deformation behavior it can provide guidance and advice for the design of subgrade to study the deformation.Firstly,clay of high liquid limit,one of the typical soils in southern region,was elected as the research object.And a series of physical and mechanical basic tests were carried out,including particle analysis,liquid limit and plastic limit test,specific gravity test,compaction test.Secondly,according to the current researches about the permanent deformation of subgrade soils at home and abroad,the internal and external influence factors on permanent deformation were analyzed.Parameters of the repeated loading triaxial test are chosen and proved,including the moisture content,confining pressure,deviatoric stress,degree of compaction and so on.A repeated load triaxial test program which is suitable for southern humid area was proposed.Thirdly,the study of the dynamic triaxial test about the critical stress level of clay of high liquid limit was carried out.The results show that the critical stress level is between 0.4~0.6 when the moisture content is OMC~1.3OMC.The confining pressure and moisture content have significant effects on the critical failure stress.With the decreasing confining pressure or moisture content,the critical failure stress decreases.Then,the prediction equation of the critical failure stress and the moisture content and confining pressure was established.The results of the permanent deformation test prove that the confining pressure,moisture content and deviatoric stress are the key factors of permanent deformation of subgrade soils.According to existing research results,a permanent deformation prediction model of subgrade with loading times,octahedral stress,octohedral shear stress,and moisture content was put forward.At the same time,the proposed model was verified by the experimental results of other scholars.Finally,the calculation method of the permanent deformation of subgrade under the proposed pavement structure was given.