Experimental Study on the Freeze-Thaw Characteristics of Clays with Different Initial Moisture Contents and Thawing Temperatures

To reveal the effects of the thawing temperature and initial moisture content on the freeze- thaw (F-T) characteristics of clays, F-T tests were performed on clays with three initial moisture contents (25 %, 30 %, and 35 %) at two thawing temperatures (25 degrees C and 70 degrees C). Changes in water content of specimens before and after F-T and the phenomena changes at the top surface of specimens after F-T were analyzed. The relationship between the change of water content and the pot-cover effect and surface cracking were discussed. The results showed that stable temperatures at the freezing of the specimens with initial moisture contents of 30% and 35 % were 14.7 % and 79 %, respectively, both lower than that of the specimen with initial moisture contents of 25 %. With a thawing temperature of 70 degrees C, the time to reach 0 degrees C of the specimen was reduced by 35.9 % to 40.57 %, and the thaw settlement coefficient was reduced by 2.4 % to 4.75 %. When the temperature changes, the deformation of specimens also change and present certain hysteresis during F-T. The upwards net change occurred after F-T; at that time, the total water content inside the specimen decreased, the water content in the upper part of the specimen decreased, and the water content in the lower part of the specimen increased. At the same time, the pot-cover effect occurred on the top surface of the specimen, and the cracking appeared on the top surface and inside the specimen. More moisture migrated upwards to the top of the specimens and the mass of water in the specimen after F-T was less with a thawing temperature of 70 degrees C. Based on the test results, some suggestions are provided for construction of cross passages with AGF and the forced thawing method.