Research On Behavior Of Compacted Expansive Soil

The expansive soils distribute the most area in our country. With development of the transportation the highway should be inevitably to through the expansive soil area. Constructing the highway in the expansive soil area how to guarantee the engineering stability and safety is the key of the engineering. The expansive soil is high swell-shrinkage special clay which mostly consists of Montmorillonite or ilite. It has some special characteristic such as much more cranny, supper concretion and expanding with wet and shrinking with dry and so on. If it is treated with the improper method, it will endanger the engineering in most extent.so it is important to research expansive soil by indoor testing.By analyzing the test data for expansive soil in the area where the YU-Zhan highway through then some problem were researched and discussed:(1) the mineral elements of compacted expansive soils were investigated from it's clay structure and chemical composition; summarizing and analyzing the swell-shrinkage theory of expansive soil and the reason why the diffuse double layers theory can explain the swell-shrinkage well; Analyzing their special engineering characteristic and their relationship of each other.(2) the swelling judgment of 4-1 clay pan were researched; The swell-shrinkage ratio formula were simplified by analyzing and selecting the index of judgment and then the linear relation between the CBR swelling ratio and the swell-shrinkage ratio were acquired.(3) the influence of initial condition parameters for compacted expansive soil was researched; The time effect of swelling were given by analyzing the test at different initial condition for compacted expansive soil. And the relation between swelling ratio and initial water content and dry density were given; then analyzing the swelling pressure in different initial condition.(4) Summarizing and analyzing the theory of the lime stabilization for expansive soils. The research performed laboratory tests of compaction test, CBR test, 50kpa swelling rate test and unconfined compression test of different curing time. Then the relationship between the strength of compacted expansive soil and the quantity of added lime were given; and for the relation between the swelling rate and the quantity of added lime.Finally, some important conclusions have been summarized and some actable suggestion for engineering has been given.