Softening phenomena will occur in normally consolidated soft clay under cyclic loading because of the increase of pore pressure with progressive cycle number. However

in overconsolidated soft clay

negative pore water pressures may develop at the beginning of cyclic loading

despite the fact that softening phenomena occurs simultaneously. It is evident that this behavior is contradictory to the effective stress principle. In addition

the preceding approach to cyclic softening characteristic of cohesive soils is to establish the relation between softening index and cycle number which doesn’t encompass the pore water pressure generation that occurs simultaneously. The residual pore water pressures correlate to softening index of overconsolidated clay subjected to uniform stress-controlled triaxial loading are investigated. A cyclic softening-pore pressure model is proposed based on the tests. The model shows the influence law of cyclic softening characterstic of overconsolidation.