| This paper is based on the National Natural Science Foundation of China(NSFC)project"Research on the effect of dry and wet cycles on Yunnan laterite dam"(Project No.51568031).This paper is based on a study of the effects of freeze-thaw cycles and high pressures on the dams in Yunnan,which can cause deformation,cracking and damage to buildings.Taking the seasonal permafrost in Yunnan as the object of study,the study investigated the high-pressure compression consolidation characteristics and creep properties of Yunnan laterite under the action of freeze-thaw cycles,taking into account the effects of cycle number,cycle time,freezing temperature and consolidation pressure,by conducting high-pressure compression consolidation tests with a maximum consolidation pressure of 3.2MPa.The research results are of great reference value for related projects.The high-pressure e～p compression characteristics of freeze-thaw cycled laterite are clarified:the e～p curve of freeze-thaw cycled laterite shows a fast decreasing-slow decreasing trend under various influencing factors,and the corresponding consolidation pressure can be divided into three stages:low pressure,medium pressure and high pressure.As the number of cycles increases,the cycle time lengthens and the freezing temperature decreases,the compression volume and compression coefficient of laterite show fluctuating increases;the pore ratio and compression modulus show fluctuating decreases.When the consolidation pressure is low,the compression coefficient increases and the compression modulus decreases with each influencing factor,and the degree of change is greater.The opposite is true when the consolidation pressure is medium to high pressure.The compressibility of the laterite is judged by the compression coefficient in the pressure range of 0.1 to 0.2 MPa:as the number of cycles increases,the compressibility of the laterite changes from low→medium.The high-pressure e～lgp compression characteristics of freeze-thaw cycled laterite are clarified:the e～lgp curve of freeze-thaw cycled laterite shows a gentle decrease at low pressure and a rapid decrease at medium to high pressure under various influencing factors,with the inflection point of the curve corresponding to pressures in the range of 0.4 to 0.8 MPa.As the number of cycles increases,the cycle time increases and the freezing temperature decreases,the initial consolidation pressure of the laterite tends to fluctuate and decrease;the compression index tends to fluctuate and increase in the low pressure range and decrease in the medium and high pressure range.As the consolidation pressure increases,the compression index tends to increase and then decrease,with an extreme value at approximately 1.6 MPa.The high-pressure consolidation characteristics of the freeze-thaw laterite are clarified:the e～lgt_g curve of the freeze-thaw laterite is close to a straight line at low pressure under various influencing factors,and the division between primary and secondary consolidation is blurred,but the slope of the curve increases compared to that of the plain laterite,and the slope of the curve increases in the first half of the curve at medium and high pressures,with a clear change in slope in the second half,and the primary and secondary consolidation of the laterite is clearly distinguished.As the number of cycles increases,the cycle time increases and the freezing temperature decreases,the primary and secondary consolidation coefficients of laterite show a trend of increasing fluctuations at low pressure and decreasing fluctuations at high pressure.As the consolidation pressure increases,the primary consolidation coefficient of laterite tends to increase and then decrease,while the secondary consolidation coefficient tends to increase rapidly and then increase slowly.The creep characteristics of freeze-thaw cyclic laterites are clarified:the strain-time relationship curves for freeze-thaw laterites and plain laterites have a similar pattern,with instantaneous strains occurring at the moment of consolidation pressure application,followed quickly by decay creep and steady creep phases as time progresses,the difference being that freeze-thaw laterites have larger instantaneous strains at the same consolidation pressure and the total strain increases.The empirical model’s function fitting relationship is applicable to the creep description of plain laterites and is not applicable to freeze-thaw cyclic laterites with large instantaneous strains.The five-element K-K model,consisting of the generalised Kelvin model and the Kelvin model,can better describe the creep properties of freeze-thaw cyclic laterite by fitting the predicted values of the strain-time relationship to the measured values at different number of cycles,different cycle times,different freezing temperatures and different consolidation pressures,and the average correlation coefficient is high.However,there is no obvious regularity between the model parameters and the influencing factors. |
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