Study On Dynamic Modulus Parameters Of Graded Sand And Gravel

The dry climate condition in Xinjiang has formed a large area of gobi sand and gravel soil,which can be used as road filling material.The mechanical properties of graded sand and gravel are mainly nonlinear,and the stress dependence of the mechanical properties of graded sand and gravel is very significant.Therefore,the stress state of graded sand and gravel structure layer will be affected by different factors,and different load grades and load action forms will affect the stress state.The mechanical property parameters of graded sand and gravel materials will be different under different stress states,which will lead to completely different results of mechanical response of pavement structure calculated,and ultimately affect the scientific and accurate value of pavement structure design.Therefore,this paper studies the mechanical properties of graded sand and gravel through dynamic triaxial tests,and puts forward the determination method of the dynamic modulus of graded sand and gravel base and the value range of the summative dynamic modulus.Referring to the 2015 th edition of the construction technical rules of highway pavement base layer in China,natural sand and gravel or gravel soil materials are used as the recommended grading range of the base layer.Combined with the actual engineering construction technology and other factors,three gradations are determined,The upper and lower limits of gradation are continuous,and the S-type gradation is skeleton dense.The maximum dry density and optimum water content are determined by compaction test.Through indoor dynamic triaxial tests,the dynamic resilience modulus tests of gradated sand and gravel with various influencing factors were carried out.The results show that the gradation and water content will affect the dynamic modulus,dry density,deviatoric stress,confining pressure and other factors,but the influence degree of different influencing factors is different.Through the analysis of the dynamic triaxial test results,it is concluded that the increase of deviatoric stress,confining pressure,decrease of water content and increase of dry density will lead to the increase of dynamic modulus,and the causes of the increase of dynamic modulus are analyzed.The dynamic and static modulus are compared and analyzed comprehensively.Based on the analysis of the dynamic triaxial test,the most commonly used and widely accepted dynamic modulus prediction model for granules was used to make parameter fitting and comparative analysis,and the most suitable prediction model for the dynamic modulus of graded sand and gravel was determined.Based on this model,the value range of dynamic rebound modulus of graded sand and gravel base is proposed.The research results can provide some reference for the reasonable value of pavement design parameters.