A Pore pressure and stability model for a silty clay under repeated loading

The behaviour of saturated clays subjected to low frequency cyclic loading is of considerable importance in the design of offshore structures. Monotonie strain-controlled and low frequency (0·1 Hz) repeated load triaxial tests have been carried out on reconstituted samples of Keuper Marl, a silty clay, under undrained conditions. The strain-controlled tests were carried out at overconsolidation ratios of 1, 4, 10 and 20 and the data from these tests were used to establish the stable state boundary surface. Results from repeated load tests on samples with overconsolidation ratios of 1 and 4 were compared with this boundary surface. Previous investigations have shown that the dry side of the state boundary surface for clays, sometimes known as the Hvorslev surface, forms an empirically determined stability criterion for cyclic effective stress paths of samples of all stress histories. Normally consolidated and lightly overconsolidated soils subjected to undrained cyclic loading become heavily overconsolidat...