e-p curve-based structural parameter for assessing clayey soil structure disturbance

Additional void ratio and yield stress that can be easily determined by one-dimensional consolidation test are two representative parameters for the assessment of clayey soil structure. In this paper, a “structural parameter” that defined as the normalization of the integral of additional void ratio times effective vertical stress until yield stress was proposed to evaluate the disturbance induced by soil structure changes. By conducting oedometer tests on Hangzhou clay at various disturbed states, the compression index, yield stress, and structural parameter were obtained. The evolution of normalized additional void ratio during one-dimensional loading is presented to establish the soil structural indexing strategies for assessment of clay structure disturbances. Based on the laboratory investigations, a linear relationship between the normalized structural parameter and normalized yield additional void ratio was obtained. For a certain soil, specimens with the same initial void ratio but different disturbed state have a nearly constant void ratio when yielding. It is also found that soils with a higher plasticity index exhibit stronger structure and lower compressibility. In addition, quick direct shear tests were carried out to examine the undrained shear strength of soils at different disturbed states. The soil disturbance degree quantified from the undrained shear strength is found slightly higher than that from the structural parameter. This study can provide a reference for assessing the clayey soil structure.