EFFECT OF CYCLES OF DRYING AT HIGH TEMPERATURE AND WETTING AT AMBIENT TEMPERATURE ON VOLUME CHANGE AND ELECTRICAL RESISTIVITY BEHAVIORS OF COMPACTED LOESS

In the environment of engineering geology,high temperatures accelerate drying of the soil mass that is also subject to wetting by rainfall. Dry-wet cycles tends to cause degradation of the soil mass,which can seriously damage the infrastructure and buildings on the soil mass. Investigation of dry-wet cycling on deformation behavior of compacted loess is indispensable to evaluate the stability of basement and subgrade in the engineering practice. In the present work,we fabricated three groups of samples with one water content of 11% and three different dry densities(1.5,1.6 and 1.7 g·cm^-3). The samples were desiccated at 80 ℃,followed by wetting at an ambient temperature through immersing the samples into deionized water until a designated dry-wet cycling number. Upon cycling,electrical resistivity was measured by a digital LCR meter to characterize the structure change of the samples. Besides,the photographs of the sample surface after desiccation were taken to observe crack evolution. At the end of the cycles,constant rate of strain(CRS)was imposed on the saturated samples to determine the deformation parameters of the compacted loss. Results shows that the electrical resistivity increases due to the increase of crack ratio as the cycling numbers increase. Since the vertical stress is zero,the volume of the unsaturated compacted samples decrease as undergoing initial drying in high temperature,followed by expansion as the samples are immersed into water. Subsequently,expansion continues in the process of desiccating the samples at 80 ℃ and shrinkage then occurs after saturating the samples. Besides,as dry-wet cycling numbers increases,the elastic compressibility index increases,and the plastic compressibility index decreases and the yield pressure increases for samples with low density but the tendency is opposite for samples with high density. This study can provide a theoretical basis for post-construction settlement analysis in the engineering practice.