Research On The Strength Characteristics Of Loess Sulphate Saline Soil Improved With Lime

In northwest inland area widespread a kind loess sulphate saline soil mainly containing sulfate, this kind of saline soil has cold expansibility influenced remarkably by temperature and corrosivity, these features have a great harm on buildings, a large scale of engineering construction is inevitable in this kind of soil area. So, this kind of saline soil has attracted more and more scholars attention. They conducted study on mechanism and influence factors of sulphate saline soil’s engineering disease, and have achieved some results. Lime is a kind of cheap building materials which resources are very abundant, and is used to improve the engineering properties of soil, which has been recognized in engineering, and obtained a certain number of technological achievements. At present in saline soil treatment with lime, the study of influence of sulfate content, soil, water stability and lime content on strengthening effects and mechanical properties of solidified sulphate saline soil, is not enough in-depth, even very shallow. So study the influence of sulfate on strength characteristics of lime soil, has very important meaning to engineering application of foundation of loess sulphate saline soil improved with lime.Through a lot of triaxial test, this paper analyzes the influence of different factors on strength characteristics of the loess sulphate saline soil improved with lime, provides some advices and guidances for treatment of sulphate saline soil foundation with lime. Test results show that influence law of sodium sulfate content on pdmax and Wop of sulfate saline soil is not a single constant, it depends on the state of the sodium sulfate in the soil, and salt content is a major factor influencing strength index of soil improved with lime. When sulfate content is low in soil, sulfate is benefit to the improvement of lime soil’s strength, and the range of increase of the soil’s strength is about50-100kpa compared with soil whose salinity is0,but when salinity is beyond a certain range (such as0.5%-1%), the higher salinity, the worse it is for strength of lime soil (2:8lime soil), the effect of salinity on cohesion is more obvious than that of angle of internal friction. The quantity of added lime in soil can affect optimal water content and maximum dry density of soil, with the increase of the quantity of lime, the dry density gradually decreases, And the optimal water content increases strength of improved-soil changes with plasticity index, In theory the higher the soil plasticity index, the greater the proportion of clay and colloidal particles, and the higher the strength of the lime soil it will be. But the higher the soil plasticity index, the stronger the viscosity will be, therefore the soil is not easy to crush and mixing uniformity, cause the reduction of its strength and stability, so should adopt appropriate plasticity index soil as the soil ingredients in construction. The maintenance period has obvious effect on strength of improved-soil, as the curing age growing, strength of improved-soil continue to grow, the strength of the soil grows rapidly in7weeks, after then increases slowly.