Study On The Stress Intensification Of Cement Stabilized Gravel

The knowledge about the performance of the material is almost derived from its mechanical properties.Cement stabilized gravel is one of the pavement materials which are widely used in road base course.In order to understand and improve the pavement performance of semi-rigid base asphalt pavement,scholars have made a large number of researches for the cement stabilized gravel at home and abroad.But at present,most of these studies are focused on its technical performances,and there is little research on its constitutive behaviors.In order to understand and study the stress intensifications of cement stabilized gravel,the cement stabilized gravel raw materials that meet the requirements of specification are selected to design a mix ratio and prepare standard cylinder spcimens with a size of ?150mm×150mm by vibration method.After 28 days of curing,by using microcomputer-controlled electronic universal testing machine,the tests such as the simple loading tests at different loading rates(0.5,1,1.5,2,4 mm·min-1),the cyclic loading and unloading tests at different stress levels(3,6,8,9 MPa),the progressive loading and unloading test,creep and relaxation test are conducted to test the stress and the strain of the cement stabilized gravel and its variations with time.The variations of the strength and stiffness,the stress-strain characteristics of the loading and unloading,the creep and relaxation of cement stabilized gravel are analyzed.The basic characteristics of stress intensifications of cement stabilized gravel are summarized,and the constitutive characteristics of stress intensifications of cement stabilized gravel are studied by combining with the generalized Saint-Venant model,the stress intensifications model and the total constitutive model of cement stabilized gravel are proposed.The results of the study indicate that the mechanical parameters such as limit stress,ultimate strain and secant modulus of cement stabilized gravel have not changed regularly with the change of the loading rate,reflecting the independence of the mechanical properties of cement stabilized gravel and the loading rate,and combining with the test phenomenon that the creep and relaxation of cement stabilized gravel is also not obvious,it can be considered that the viscosity of cement stabilized gravel is very weak and can be ignored;an obvious permanent deformation was produced after the initial unloading,the stress and strain of the cyclic loading and unloading can go back and forth along the original path at different stress levels,which fully reflect the elastic-plastic properties and the stress intensifications of cement stabilized gravel;the unloading curves of cement stabilized gravel at different stress levels are basically parallel,and the average of the corresponding secant modulus is slightly larger than the compressive elastic modulus measured according to the specification,the secant modulus of the unloading curves can be applied to determine the initial elastic modulus by analyzing the generalized Saint-Venant model;the intensification model and the total constitutive model which proposed in this paper have very good effectiveness for the numerical simulation and provide an analysis method and theoretical basis for understanding the stress intensifications rule and stress-strain relation of cement stabilized gravel.