A series of undrained triaxial compression tests is performed on normally-and over-conolidated saturated marine clays. The test result shows that the rate of decrease in undrained shear strength due to rebound depends exclusively on the overconsolidation ratio, and the undrained shear strength of overconsolidated clay changes linearly with the change in effective confining pressure at the state of equilibrium prior to shear process.
　A result of consolidation and rebound tests leads to the conclusion that the ratio of swelling index to compression index is uniquely related to the overconsolidation ratio for particular clay, where the swelling index is defined as the slope of straight line connecting a state point on rebound curve and the corresponding state point on consolidation curve in the e～log p diagram.
　A case record of rebound due to removal of surface loading is described, and the change in measured unconfined compression strength compares favourably with the laboratory test result.