Study On The Reasonable Thickness Of Low Embankment And Zero Filling Subgrade Bed

The low embankment and zero filling are widely used in highway design and construction because of their saving land resources and reducing project cost.Popularization and application of low embankment has become a new development concept the important direction of highway construction in our country,however,at present our country "code for design of highway subgrade(JTG D30-2015)on the rules of the road bed,without fully considering the low embankment,and the characteristics of the zero fill roadbed,roadbed of vehicle dynamic load for a long time and operation period of moisture content change insufficient consideration,often leads to low embankment and zero fill permanent deformation is too big,not only cause the road service level is reduced,but also affects the service life of road.Based on this,this paper takes guangxi road&bridge corporation and changsha university of science and technology cooperation project of "southern humid area low subgrade workspace reasonable structure scheme research" as the backing,on the basis of site investigation,first of all,use the method of numerical simulation and research,the low embankment foundation during the operating period the change of moisture content were analyzed,and then through the indoor dynamic triaxial test was obtained under the condition of equilibrium moisture content of subgrade filling critical dynamic stress and dynamic modulus of resilience,finally calculated by using elastic mechanics roadbed dynamic additional stress distribution,then the reasonable road bed thickness,and by using the finite element analysis results for validation.The main conclusions and results of the study are as follows:1)the secondary roads of guangxi baise area and low embankment and zero fill moisture content research and numerical simulation of embankment internal balance moisture content,established the roadbed the relationship between the equilibrium moisture content and low embankment subgrade height,summarizes the distribution regularity of internal equilibrium moisture content of the subgrade.2)the indoor dynamic triaxial test,which obtained the critical dynamic stress of subgrade filling and dynamic modulus of resilience,systematic analysis of the effects of moisture content of filler in the critical dynamic stress,give the hyperbolic model of stress-strain relationship of the packing material;The hyperbolic model of confining pressure,moisture content,dynamic load and elastic modulus is obtained.3)Carried out the analysis of influencing factors of vehicle dynamic load,and obtained the calculation model for calculating the additional stress of roadbed.With the help of Laplace transform,the calculation program of the dynamic additional stress at each depth of the roadbed is obtained by using the Laplace transform,and the additional stress values of the subgrade at each depth are given through the program calculation.4)The system analyzes the relationship between critical dynamic stress,dynamic additional stress,subgrade bearing capacity and soil gravity,and obtains reasonable thickness of low embankment bed.By establishing a three-dimensional finite element model,the reliability of the bed thickness in practical application is analyzed.