| Expansive soils distribute widely throughout the world. The main components of expansive soil are minerals, such as montmorillonite, illite and kaolinite. Expansive soil will swell when it is wetting and will shrink when it is drying. In addition, it has the feature of repeated deformation. Expansive soil is called as disaster soil in civil engineering.Due to the characteristics of expanding and shrinking repeatedly, many kinds of engineering constructions built on the lands of expansive soils are often destroyed. The loss caused by expansive soils is up to several hundred millions in China every year. The research concentrated on the macro/meso-structural evolution of expansive soils under the change of environment, such as load and moisture. The results can be as the theoretical basis for the analysis of the deformation, strength and stability of expansive soils. It is significant for the constructions in the region of expansive soils.The samples used in the test were made up with the expansive soil, which was collected from the slope in the location of middle section of South-to-North Water Transfer Project in Taocha, Nanyang city. The samples of remolded expansive soil were initially damaged under different degree and in different location. The structural evolution and mechanical properties of the samples were investigated with CT-triaxial test. The research consists of the following three parts.First, five samples with three kinds of damage areas and two different damage positions were tested with CT-triaxial apparatus. The effects of damage area and damage location on the mechanical properties and the rule of structural evolution of damaged samples were studied under the condition of the same suction and confining pressure, which were 50kPa and 100kPa respectively.The effects of confining pressure and suction on the mechanical properties of deformation and strength of damaged samples were analysed with CT-triaxial testing system in the second part. The tests were carried out on the remolded expansive soils with the same damage area under different net confining pressure and various suction.Finally, the main influence on the strength and stability of expansive soil could be found by comparing the two kinds of effects in the two groups of tests. The influence factors that studied in the dissertation included the damage area, the damage position, the confining pressure and the suction.The following conclusions can be drawn from our research:(1) The samples with the same damage area have the similar strength properties when the suction and net confining pressure remain unchanged. However, the deformations are not consistent among these samples. (2) The deformation increases with the increasing net confining pressure when the suction remains unchanged. However, the deformation decreases when the damage location is closed to the outside of the sample. (3) When the net confining pressure is fixed and the suction pressure varies, the time taken in the testing for the deformation reaching to the maximum reduces with the suction pressure increasing. The area of the damage in the soil sample reduces gradually when the confining pressure is more than 400kPa. The value of ME increases, while the SD value decreases along the procedure of test. Under the same suction and net confining pressure, the more severely damaged the samples have, there are the more obvious change in the values of ME and SD. |
