Indoor-Test Research on Improvement of Expansive Soil

Due to the strict control of the subgrade deformation of high-speed railway,the improvement of subgrade filling has become an important issue,which has been concerned by the geotechnical researchers and engineers. The expansive soil is a kind of geologic body with obvious shrinking and bulking features,and its clay content is mainly consisting of super- hydrophilic mineral,so the improvement of expansive soil is one of the significant issues in the study of expansive soil subgrade treatment. Combined with a case of railway subgrade engineering,indoor-test has been undertaken on the soil with expansibility and disintegration. The results are:( 1) With the increment of cement content,the maximum dry density of expansive soil decreases,while the optimum moisture content increases;( 2) With the increment of gravel,the maximum dry density of expansive soil increases and the optimum moisture content decreases,and the range of variation increases fast;( 3) With adding cement content to 4%,5%,6%,the free expansion rates are separately 39% 、34% 、28%. Free expansion rate of expansive soil decreases with the increment of cement content and there is no disintegration happened at all,which illustrates the increment of cement has good effect on improvement of disintegration that can basically meet the requirement of subgrade and embankment of high-speed railway.