In the literatures

there are two major forms of expressions of the effective stress and the pore pressure coefficient B controlling the deformation of saturated geomaterials. In order to discriminate and analyze their rationality

the relationship is investigated between the volumetric compressibility coefficients of the solid phase and the skeleton subjected to both hydrostatic pore pressure increment and net cell pressure increment under an undrained condition. Also investigated are the volumetric deformation increments of the liquid phase

the solid phase and the skeleton induced by the hydrostatic pore pressure increment and the net cell pressure increment. The problems existing in the derivation procedures of the two forms of expressions of and B are pointed out. Based on the equivalence relations of the deformations under undrained and drained conditions

new expressions for the effective stress and the pore pressure coefficient B are established.