Research On Subgrade Moisture Distribution And Stiffness Of Humidity Dependence In Hot And Humid Areas

With the influence of climate, underground water and roadbed drainage conditions, the subgrade soil humidity in hot- humid area will change over time and space, impacting the Stiffness of the subgrade soil, transformation and the mechanical response of pavement structure layer under the action of load immediately. Therefore, carrying out the study of the typical subgrade soil humidity field distribution characteristics and evolvement rule in hot-humid area, formulating indoor dynamic modulus of resilience test method which according with the typical pavement structure layer under the roadbed soil mechanics characteristics in hot-humid area and inspecting the stress of the modulus of resilience and humidity dependence are very meaningful for providing reference about the modulus of pavement structure design parameter selection in hot- humid area.Aiming at the drawback that the conventional soil water characteristic curve test method can not inflict stress to test specimen and measure the volume deformation, the article carried out the study of typical load conditions soil subgrade soil water characteristic curve test at first, then proceed parameter fitting which used the Fredlund soil water characteristic curve as original model and analyzed the stress correlation of it's parameter. We got the relationship of typical subgrade soil water characteristics and upper load at last and test results provided the basis for the hydraulic parameters values of subgrade humidity field counting material.We inspected the humidity distribution and evolvement rule of subgrade soil under hot and humid environment and revealed the source and change of subgrade humidity through indoor and outdoor tests, humidity monitoring and numerical calculation method, etc. Affected by the climate and the groundwater, the moisture contents are all raised contrasting to the optimum moisture content during the construction time. The subgrade interior is humidifying fearfully and the overall saturability of clay soil subgrade humidity is more than 90% and has obvious layered sex. We also got the typical subgrade soil humidity recommended value for a long time in hot- humid area and revealed the source and change rule of subgrade humidity.In the article, we computational analyzed the subgrade soil stress state under typical pavement structure and formulated the testing program of dynamic modulus of resilience of subgrade soil indoor triaxial repeated loading which conforming to the characteristics of pavement structure layer in southern humid area in China through combining typical of fine grained soil compaction test features and balance humidity condition. We also proceed modulus of resilience of subgrade soil indoor triaxial repeated loading test experiment of different degree of compaction and moisture content based on the above-mentioned dynamic modulus of resilience of subgrade soil indoor triaxial repeated loading test scheme. It turned out that rebound modulus rely on the moisture content and stress state obviously. We adopted modulus of forecast model recommend by NCHRP1-28A to match the parameter and the correlation index is more than 93% which proved the constitutive model is reasonable. At last, we gave out recommended value of the modulus based on the long-term change rule of subgrade humidity.