Study on Expansion Characteristics of Expansive Soil Under Dry-wet Cycle Conditions

The characteristics and micro-mechanism of water absorption and expansion of expansive soil were discussed by carrying out no-load expansion rate, loaded expansion rate, and micro-scanning test on expansive soil in northern Xinjiang under dry-wet cycle conditions. The test results show that: (1) In the no-load expansion rate test, with the increase of time, the no-load expansion rate gradually increased and gradually stabilized in the later stage of the test. With the increase in the number of dry-wet cycles, the unloaded expansion rate gradually decreases and tends to be stable after the fifth cycle. (2) In the load expansion rate test, with the increase of time, the load expansion rate gradually increases and tends to be stable in the later stage of the test. The larger the overlying load, the smaller the load expansion rate of the expansive soil sample; with the increase in the number of dry-wet cycles, the loaded expansion rate decreases gradually, and the loaded expansion rate decreases with the increase of the number of cycles and the overlying load. (3) The results of scanning electron microscope show that the structure of expansive soil sample without cycle is relatively firm. After the dry-wet cycle, the microstructure of the expansive soil sample changes obviously, the microstructure of soil mass breaks gradually, the particle area decreases, and more tiny pores appear, which leads to the decrease of expansion rate with the increase of cycle times. The research results can provide a theoretical basis for the stability of expansive soil in northern Xinjiang.