EXPERIMENT STUDY OF EFFECTS OF FREEZING-THAWING CYCLES ON MECHANICAL PROPERTIES OF QINGHAT-TIBET SILTY SAND
CHANG Dan1，LIU Jiankun1，LI Xu1，2，YU Qianmi1
(1. School of Civil Engineering，Beijing Jiaotong University，Beijing 100044，China；2. Qinghai Research Observation Base，Transportation Industry Laboratory of Highway Construction and Maintenance Technology in Permafrost Regions，Qinghai Research Institute of Transportation，Xining，Qinghai 810000，China)
Abstract：In order to study the effects of freezing-thawing cycles on the mechanical properties of silty sand from Qinghai-Tibet，triaxial tests were conducted with the different numbers of freezing-thawing cycles at different freezing temperatures under various confining pressures. The stress-strain behavior，the static strength，the elastic modulus，the cohesion and the angle of internal friction were measured for unfrozen samples as well as thawed ones. The testing results show that the mechanical properties of studied soil are affected considerably by the numbers of freezing-thawing cycles. The freezing temperature has little influence and showing no obvious regularity. The method of significance analysis is used to analyze the influence level of the number of freezing-thawing cycles，the freezing temperature，the confining pressure and the interactions between them. The results of significance analysis show that both the values of confining pressure and the numbers of freezing-thawing cycles had significant influence on the mechanical properties；while the influence of the freezing temperature is weak. The interactions between the confining pressure and the number of freeze-thaw cycles and the one between the freezing temperature and the number of freeze-thaw cycles both affected the mechanical properties of silty sand significantly，so as to suggest that the method of significance analysis may be used to study the influence of different factors on the properties of frozen soils.
2014, Vol. 33 
