Study On Hydra-thermal Coupling Of Subgrade Filler And Its Main Influence Factors In Southern China

Over-wet soil is common in highway construction in Southern China.In order to meet the strength requirements of subgrade filling and deformation index,it requires a long period of time to decrease the water content from natural to control compaction water content.In Southern China,the climate is subtropical monsoon climate,and rain falls frequently in summer.To obtain the principle of moisture content of the subgrade filler under the atmospheric effect,reducing the moisture of the wet soil scientifically through the measures of turning filler over,soil drying becomes the key step.The research is of great significance to reducing the environmental pollution,reducing the project cost and ensure the compaction quality of highway engineering.Based on the theory of interaction between soil and atmosphere and on the actual working situation,the numerical simulation method of hydra-thermal coupling is put forward.The parameters of the basic physical properties and numerical measurements of expansive soil,red clay with high liquid limit and the granite residual soil selected from Hainan and Guangdong province were obtained.Drying model test of granite residual 5oil were conducted and the results of the tests were compared with the results of the numerical simulation,which shows the simulation method and parameters used in it were verified.The numerical simulation of three soils in typical climate of South China were conducted,and the main influence factors of heat-moisture coupling were analyzed by the methods of control variable and grey relational analysis.In view of the engineering delay caused by the weather in the southern rainy season,the invention provides a rapid moisture reducing device for roadbed filler.The analysis of main influencing factors of soil moisture heat coupling of three kinds of typical South over-wet soils shows that under the same weather conditions,the stronger the water holding capacity is,more tedding time required.It requires over 4 days for expansive soil in the typical climate of South China to dry from natural water content to compacting control water content,and the main influence factor is particle size.So the control particle size of the expansive soil in scene should be in 3～5cm.High liquid limit red clay and granite residual soil require 56 hours and 40 hours to dry from natural water content to compacting control water content respectively.For the red clay with high liquid limit,the particle size is the key controlling factor,the particle size is reduced by 15%,the drying time can be shortened by 22%,and the particle size is controlled at about 3cm in the drying process.So the particle size of high liquid limit red clay in scene should be 3 cm and the thickness of the loose layer in scene should be about 25cm.For the granite residual soil,loose layer thickness is the key control factor,thickness decreases 20%,the drying time can be shortened by 10%;at the same time,there exists an optimum mixing time,namely the second hour during the tedding,when the granite residual soil tedded up and down once,the total drying time is reduced by 40%to 24 hours.So the particle size of high liquid limit red clay in scene should be about 1～2 cm and turning the soil up and down in the second hour of tedding.