Study On Numerical Simulation Of Subgrade And Pavement Structure With Geotechnical Waterproof Reinforcement Layer

As a bad geological condition often encountered in road construction,expansive soil roadbed slope has the characteristics of small safety factor and large displacement and deformation.Under the action of load,there will be excessive settlement and local non-uniform deformation.Especially in the case of groundwater and rainfall infiltration,water immersion will cause large displacement and deformation of roadbed,and even lead to slope landslide destruction.The common treatment methods of expansive soil roadbed slope in engineering include replacement and lime-mixing modification,organic macromolecule solution modification,lime pile or lime-soil pile reinforcement,while the method of setting waterproof reinforcement layer on roadbed with geotechnical materials is relatively rare.Therefore,on the basis of existing research on expansive soil roadbed and geotechnical materials,this paper makes the following research on this method:The expansive soil samples in Baise area of Guangxi were studied in detail by basic parameter tests.The natural density,natural water content,specific gravity,particle size distribution,optimum water content,liquid-plastic limit,cohesion and internal friction angle,free expansibility and permeability under different water content were studied respectively.The results showed that the expansive soil samples were micro-expansive soil.Indoor scale model test of expansive soil roadbed is used to study the expansive soil roadbed.The stress state and displacement deformation of expansive soil roadbed under dry soil,groundwater and rainfall conditions are discussed respectively.The experimental data of deformation displacement and earth pressure are obtained.It is found that rainfall will make the roadbed model.The displacement of expansive soil roadbed is increased,and the displacement of expansive soil roadbed can be significantly reduced by adding geogrids and composite geomembrane.Therefore,it is feasible to improve expansive soil roadbed by setting waterproof reinforcement layer of geotechnical materials.The finite element software ABAQUS is used to simulate the model test of indoor roadbed,and the simulation calculation is carried out for five working conditions.It is found that the introduction of groundwater and rainfall will increase the maximumhorizontal displacement and vertical settlement of expansive soil roadbed,change the vertical stress and decrease the stability of roadbed,while the geogrid can expand in dry soil.The maximum horizontal displacement of soil roadbed decreases by 23.6%,while the composite geomembrane can reduce the rainfall infiltration and the rising height of groundwater,thus reducing the influence of groundwater and rainfall on the roadbed.Then the numerical simulation results are compared with the experimental results.It is found that the numerical simulation results show the same trend as the experimental results,and the error between them is less than 15%.Finally,the reliability of the subgrade numerical model is proved.This model is applied to the actual expansive soil roadbed and pavement structure.The stability and displacement deformation of the roadbed structure with geotechnical waterproof reinforcement layer are discussed from the modulus,location,number of layers and permeability coefficient of geotechnical materials,respectively,under the action of traffic load.The reasonable laying method of geotechnical materials is explored,which can effectively increase the expansive soil roadbed.The stability of the foundation structure reduces its horizontal deformation.The influence of rainfall conditions on the structure of subgrade and pavement is analyzed.The pavement deformation stress is evaluated by using the maximum deflection value of road surface and the maximum vertical compressive strain at the top of subgrade.It is found that rainfall will increase the pavement deformation stress by 60% and 28.7% respectively,while the composite geomembrane will decrease by 16.9% and 15%,which proves that geotechnical materials are effective in controlling stress and deformation in road structure.