Strength Characteristics Of Cement Stabilized Macadam Based On True Triaxial Test

Stress condition of internal cement stabilized macadam base was very complex in semi-rigid asphalt pavement structure,much of which was triaxial compressive stress state.Real stress state of cement stabilized macadam in pavement could not be reflected by present test methods such as unconfined compressive strength test,split test or flexural strength test etc.Therefore,it is necessary to study mechanical properties of cement stabilized macadam material by the use of true triaxial test equipment,especially strength characteristic.By using simple true triaxial apparatus of Changsha University of Science and Technology,compressive strength test on cement stabilized macadam had been carried out under three-direction independent load and different combination.Existence of intermediate principle stress had been proved by studying on intermediate principle stress effect of cement stabilized macadam material.Strength of cement stabilized macadam material had been obviously raised with increasing of intermediate principle stress,and effect of the stress was interval.Compressive modulus of cement stabilized macadam material increased with increasing of intermediate principle stress and hydrostatic stress under condition of triaxial compression.The hydrostatic stress had a larger influence on compressive modulus than intermediate principle stress.Regression analysis on limited meridian equations of special stress angle 0°and 60° had been made,the research result showed that deviator stress and hydrostatic stress of cement stabilized macadam material were linearly related to each other.Mohr circle and shear strength envelope of angle 60° were drawn.It was indicated that shear strength of cement stabilized macadam material envelope changed non-linearly with increasing of lateral stress and the envelope curved gradually.Failure of cement stabilized macadam material was far different from the Mohr-Coulomb criterion which had been commonly used in field of engineering material,while,it was relatively close to ? plane failure curve of twin shear strength and weighted twin shear strength.The uniaxial compressive strength decay test on cement stabilized macadam had been carried out under condition of triaxial compression.The research results showed that compressive modulus was linearly related to hydrostatic stress,and the hydrostatic stress of the material had a larger influence on residual strength ratio of it under triaxial unloading phrase.Compressive strength decay increased seriously with increasing of vertical design load,while vertical compressive strength decreased with increasing of the design load and the curve in non-linearly related after uninstalling.Residual strength ratio was linearly raised with increasing of hydrostatic under any kinds of loading,besides,the larger the hydrostatic was,the more serious the compressive strength decay was.