Static And Dynamic Behavior Of Compacted Silty Clay Subjected Freeze-thaw Cycle

The area of deep seasonally frozen region which affects the projects directlycan reach3.67×106km2, and the frozen depth is beyond1.5m. But the physical andmechanical properties of the subgrade soil would be influenced by the effect offreeze-thaw cycle, and under the heavy load with long term, the typical diseases offrost boiling, subsidence will appear, which could reduce the pavement performanceand service years. It would be cost lots of manpower and financial forreconstruction and repair. The healthy development of the local economy would berestricted.The propose of this research is to identify the process and principle of thesubgrade diseases under heavy loading in seasonally frozen region, furtherunderstand the mechanical behaviors of the compacted silly clay subjected tofreeze-thaw cycle, and provide test data for the following research. Based onunconsolidated undrained triaxial test and resonant column test, the mechanicalbehavior of compacted silty clay were researched subjected to freeze-thaw cycle,and the main conclusions as follows?(1) Water contents and temperatures of the samples were monitored during thefreeze-thaw cycle test in closed system. The freeze-thawing cycle test instrumentwas self-prepared. The change laws of time and temperature of the frozen and thawwere analysed and concerned. The weight and volume of the samples weremeasured by the methods of volume-change instrument and artificial during thefreeze-thaw cycle, the change laws of the related physical parameters wereidentified.(2) Static properties were carried out though the static triaxial test which wasstrain controlled. The influence of confining pressure, compaction, water contentand numbers of freeze-thaw cycle caused on the static properties were analysed,and the failure modes of the samples were researched at microscopic andmacroscopical scale. The relationship between the difference value of principlestress and axial strain were further analysed, and effect laws of different factorsinfluence the failure strength, tangent modulus, cohesion and internal friction angleof the compacted silty clay were confirmed. The empirical predicted formulas offailure strength, tangent modulus, cohesion and internal friction angle werepresented by the method of multiple nonlinear regression analysis.(3) Dynamic parameters were determined by the resonant column test afterfreeze-thaw cycle. The influence of confining pressure, compaction, water content and numbers of free-thaw cycle caused on the dynamic properties were analysed.And the effect law of different factors influence on the dynamic shear modulus anddamping ratio were obtained. The range of the dynamic shear strain was expandedbased on the hyperbolic model. The empirical predicted formulas of the maximusdynamic shear modulus and maximus damping ratio were presented.