Constant rate of displacement test on ultra-soft soil

The step-loading consolidation test with hydraulic Rowe cell on ultra-soft soil takes several weeks to obtain a complete e–log σ′v, curve. An alternative method is to conduct the test at a constant rate of strain. This test can be carried out with the hydraulic Rowe cell by pumping water into the diaphragm cell at a constant rate of volume. A series of tests were carried out at various strain rates. A method is proposed for the selection of a suitable strain rate based on the estimated compression index. The best strain rate for the soil used in this study is 0·01%/min. The various compression indices at the different log-cycles can be determined from the e–log σ′vcurve obtained from this test. The large-strain coefficient of consolidation and permeability at various times and stresses can also be obtained, because the settlement and pore pressure are measured during the test.