Prediction Of Swelling Deformation Of Highway Expansive Soil Subgrade

Expansive soil is a water-sensitive material,which is mainly composed of strong hydrophilic clay mineral composition(montmorillonite and illite),with water swelling,water loss characteristics.Under the action of atmospheric dry and wet circulation,expansive soil will be significantly shrinkage and intensity attenuation,which will cause uneven deformation of expansive soil subgrade,leading to early failure of pavement,puddle and fouling.The atmosphere through the rain and evaporation and expansive soil subgrade for water heat exchange,roadbed moisture content will also change.Based on the theory of expansive soil unsaturation,this paper uses the calculation method of damp-heat coupling to obtain the relevant data of the permeability coefficient of the fill soil by the soil water characteristic curve test,and constructs the two-dimensional finite element analysis model of expansive soil subgrade To calculate the long-term evolution of the water content of the road expansive soil under the influence of atmospheric influence;to test the exponential expansion and expansion of the expansive soil in the room,to calculate the expansion coefficient calculation formula,and to revise the DGFredlund expansive soil roadbed expansion prediction formula Finally,combined with the case analysis of the project roadbed,this paper uses the prediction formula established in this paper to solve the wetting deformation of road expansive soil subgrade.The main conclusions of this paper are as follows:1.The two-dimensional finite element analysis model of water migration of expansive soil subgrade was constructed,and VADOSE/W software was used to study the humidity balance of expansive soil roadbed.The results show that the water content of expansive soil subgrade will gradually increase under the influence of atmosphere and eventually fluctuate slightly in the vicinity of equilibrium moisture content,and the equilibrium moisture content is close to the plastic limit of expansive soil,which is consistent with the field monitoring data.At the same time,the accuracy of the model and method of calculating the equilibrium water content of the subgrade established in this paper is verified.2.The governing equations,boundary conditions and the assignment of the calculated parameters are introduced in detail.The results show that the pore water pressure distribution curve of the expansive soil embankment is the same as that of the expansive soil embankment.The pore water pressure distribution curve of the expansive soil embankment is the same as that of the expansive soil embankment.Whether the volume moisture content at the corresponding date node is close to the equilibrium moisture content.3.Based on the theory of elasticity and mechanics and deformation analysis,the swelling coefficient of expansive soil is deduced and put forward.Based on the characteristic curve test and fitting result of expansive soil,the expansion coefficient is changed with the expansive soil The function of the relationship.4.The DGFredlund formula is modified and the calculation method of expansive soil subgrade wetting deformation is put forward.The expansive soil subgrade of Ningming,Guangxi is analyzed and the wetting deformation of expansive soil subgrade is obtained and compared with the field deformation monitoring data.The correctness of the formula is as follows:According to the correction formula,the amount of viscous swelling of the expansive soil subgrade decreases with the increase of the initial water content,and the initial moisture content is close to the equilibrium moisture content of the roadbed.Therefore,in the filling of expansive soil embankment,in order to reduce the amount of wet swelling should be used as far as possible the higher moisture content of the filler.