Expansion Model Test of Expansive Soil in Different Stress State

The hydroscopic expansion of expansive soil always leads to engineering safety problems. With mid-expansive soil at Nanyang, the relationship among the expansion ratio caused by total wetting of expansive soil, eventual and initial ratio of water content, and overlying loads was studied. By taking measures such as improving the controlling system of water inlet and measuring the outer body changes, tri-axial stress state expansive tests were realized, and the rules and relationships among volume expansion ratios caused by total wetting, eventual and initial ratio of water content, and averaged primary stress were studied. The experiments show that the volume expansion ratio under different stress states and eventual ratio of water content both decrease with increase in overlying pressure or averaged primary stress, which represents a relatively good linear relationship in semilogarithmic coordinates. The relationship among expansion models at different stress states and the unified expression for these models were established, on the basis of which any expansion constitutive relation of expansive soil at any water-containing ratio could be obtained. The expansion experiments are easily carried out with concise model expressions and parameters with explicit physical meanings and can also be used in numerical analysis and simplifying calculations.