Research On Influence Of Dry Density On Subgrade Performance

The soil-water characteristic curves in three dry densities are obtained with filter paper method; the parameters of Van Genuchten model are received by fitting test data; and the influence of dry density on soil-water characteristic curve and parameters of Van Genuchten model is analyzed. The effects of compactness and water content on resilient modulus are analyzed with laboratory test of resilient modulus; and the relationship between them is established. At last, based on hydromechanical coupling mechanism and combined with the test results, the dynamic response model of subgrade moisture and deformation under the variation of groundwater level is built; the distribution of water content and resilient modulus and the deformation of subgrade are calculated when the groundwater level rising from -6 m to -3 m. The results show that: dry density has great influence on parameters of Van Genuchten model of soil-water characteristic curve, the saturated water content linearly decreases, the residual water content and parameter n linearly increase with the increase of dry density; and the parameter a has a linear correlation with the reciprocal of air entry value; the resilient modulus decreases with the increase of water content and increases with the increase of compactness. The water content increases and resilient modulus decreases significantly caused by the rise of groundwater level; then it results in unnegligible deformation of subgrade. Under different filling compactness, the difference of deformation of subgrade caused by variation of groundwater level is obvious. Therefore, controlling compactness is an effective method to improve the performance of subgrade.