Moistening Deformation and Microstructure Change of Undisturbed Loess Under Confined Conditions

Abstract

Under the confined conditions, the influence of water content on the deformation characteristics of loess collapsing was studied by the indoor collapsibility test. The microscopic images were analyzed microstructural changes of the soil before and after the collapsing. The result shows that: (1) the higher the moisture content, the smaller vertical deformation of the sample after immersion in water under the same immersion pressure, and the smaller collapsibility. On the contrary, when the moisture water content is small, the main form of deformation is water immersion. After the collapse deformation, the amount of compression will decrease; (2) with the increase of water content, under the joint action of pressure and water, the soil structure tends to be dense, the particle filling area becomes larger, and the pore filling area decreases, and the pores are filled with clay and fine particles, and the connectivity between pores is reduced; (3) the average pore diameter, average pore area and average pore circumference of different soil samples after immersion are gradually reduced compared with the soil sample before immersion. The area is evenly distributed in each angular region and is related to macroscopic collapse deformation.