Expansive Soil, Add Water, Deformation And Strength Properties And Structural Changes In The Microscopic Analysis

Based on laborary study with triaxial shear tests, direct shear tests, compression tests, and expansiveness tests of the expansive soil in An'kang area, Shanxi Province, P.R. China, the influence of structural behavior on expansibility, shearing strength and compression is discussed. The variable regularities of water-absorbing deformation and shear strength with initial water content, initial dry density and upper pressure are summarized as well as the quantitative correlations of them are described. The contributions of these factors and their reciprocal actions affecting deformation and strength are ascertained by the way of orthogonal test interpretation. The effective ways of reducing expansiveness, collapsibility and that of enhancing strength of expansive soil are proposed. The formulas calculating the deformation and strength are summarized respectively on the factors of initial water content, initial dry density and upper pressure.Real-time CT scanning observations reflecting the expansiveness and strength variation are carried on. The structural changes during the course of consolidation, shear failure, swelling and water saturated shear failure are analysed by means of CT images. A damage increment A is defined to express the magnitude of damage. Furthermore, the variation regularities of A under different stress conditions are shown to reveal the mechanism of damage process of expansive soil.