Influences of spring thaw on working performance of airport soil field surface in cold region

Abstract

By considering the temperature-rising effect during spring-thawing period, the frozen soil samples with water content of 15%, 17%, 19% and 21% and compaction degrees of 90%, 95% and 98% are prepared to investigate the variation characteristics of thermal conductivity and shear strength in the soil field surface of airport lifting zone in cold region by pre-embedded temperature sensor, steady plate method and fast direct shear method. Laboratory experiments on the frozen soil samples are conducted to achieve internal temperature changes, thermal conductivity variations and fast direct shear strengths. The characteristics of thermal conductivity and mechanical properties of the frozen soil samples are obtained and the influences of the spring-thawing effect on the working performance of airport soil field were summarized. The results show that, there are significant internal temperature variations in the frozen soil samples during the process of temperature rise. The existence of frozen core makes its melting process present four stages, including rapid heating period, moderate melting variation period, accelerated melting variation period and melted period. By analyzing the thermal conductivity variation curves of twelve sets of frozen soil samples, it is found that the thermal conductivity of frozen soil samples decreases as a whole, but still fluctuates, during the temperature rising process, which is also consistent with the internal temperature field. By analyzing the results of fast direct shear tests on sixty sets of the frozen soil samples at ambient temperatures of -5, -1, 3, 7 and 11 ℃, it is proved that the shearing strength increases with the increase of compaction degree and decreases with the decrease of water content significantly during the temperature rising process.