Abstract: It is quite common that deformation occurs when earth and rock materials are wet. Generally, initial strain method is more popular than the theory of unsaturated soil in calculating the wetting deformation. The wetting tests are usually carried out by single line method or double line method. In this paper, the wetting tests and relevant calculation methods are used to calculate the wetting deformation and related influence parameters, and a new approach in calculating wetting deformation and its influence is put forward, which mainly involves: (1) under a certain stress state, wetting deformation actually includes two components, one is induced by the ‘soft’ effect of the soil’s stiffness, the other is the ‘real’ additional deformation induced by wetting. (2) It is unsuitable to directly subtract the deformation of ‘dry soil’ from that of the ‘wet soil’ at the same stress state in the double line test. The subtraction should be calculated by using the tangent modulus under the same stress state. (3) Based on the generalized potential theory and the dual properties of stress and strain, one can transform the effect of the wetting deformation into an equivalent stress. Although this is an approximate method, it is simple and easy to quantify the wetting effect. This idea can also be used to investigate the effect of rheological deformation and the deformation caused by particle breakage and drying-wetting cycles.

Key words: wetting deformation, single line method, initial strain method, generalized potential theory