Experimental Research On Stabilized Expansive Soil And Analysis Of Swelling-shrinkage Deformation Of Foundation

The expansive soil is a kind of special regional soil, which distributes widely in china. As the heavy construction of expressway, the problem of expansive soil in the roadbed filling and slope stability are more and more outstanding.The study of the characteristics of expansive soil becomes more and more important.In this thesis, the effect of lime content on characteristics of lime stabilized expansive soil, characteristics of CTMAB stabilized expansive soil and swelling-shrinkage calculation methods of expansive foundation are studied with theoretical and experimental methods.The main points are shown as foliowings:Firstly, the main properties of expansive soil and the mechanism of expansive soil stabilized by lime are summarized. It is illustrated that lime stabilized soil is suitable to fill roadbed instead of natural expansive soil by series of experiments on expansive soil obtained from Huaian region. At the same time, the relationship of compaction curve, maximum dry densities, optimum water content and lime content are researched through the compaction tests. The free swelling ratio, liquid limit, plastic limit, swelling ratio without vertical pressure, swelling force subjected to the lime content are investigated by experiment.The relationship of swelling ratio and vertical pressure at different degree of compaction are investigated in this thesis.The devices for detecting water content are buried at different depth of roadbed for studing the effect of the seasonal rain and the level of groundwater on water content of the earth-fill. The charicteristics of water stability for natural and lime stabilized soil are investigated with wetting-drying cycling tests. The results show that the water stability of lime stabilized expansive soil is much higher than natural expansive soil.Lime can be used as the ameliorater to the filling of expressway embankment, but it can not be used as a stabilized agent for natural expansive soil in slope. In this thesis, CTMAB is used as a stabilized agent to improve the natural expansive soil in slope and the mechanism of CTMAB stabilized soil is primarily illustrated. The free swelling ratio, swelling force and wetting-drying cycle of CTMAB stabilized soil have been studied by experiments.The photos of expansive soil and CTMAB stabilized soil samples after wetting-drying cycle tests has been compared. The results show that CTMAB can be used to stablized expansive soil in natural slopes.Finally, the calculation methods on swelling-shrinkage deformation of expansive soil used in recent years have been summarized and the conditions of swelling-shrinkage deformation have also been analyzed in this thesis. Experimental methods have been used to estimate swelling-shrinkage deformation of foundation as the change of moisture content. At the same time, testing of swelling force has been conducted on different moisture content, and the critical height of road embankment has been obtained from swelling force tests for expansive foundation when it satisfies no expansive deformation.