Constitutive relationships, which can relate stress state variables (net stress and suction) to strain state variables (void ratio and water content ratio) in swelling clay, are investigated in the present study. Additionally, the method to identify the nonlinear hydromechanical tangent moduli of swelling clay is given, in which transversely isotropic behavior of hydromechanical coupling is incorporated based on the experimental results obtained by the free swelling tests. The experimental results of the constant load swelling tests in uniaxial strain condition and free swelling tests are discussed. We find that swelling behaviors such as changes of void ratio, water content ratio, and saturation depend strongly on stress level and/or constrained conditions, and verify the predicted swelling behaviors in uniaxial stress and strain conditions by using finite element analysis.
