Effect of strain rate on triaxial extension behavior of silty clay

Traditional methods of suction caisson foundation design only consider the soil is under either purely drained or purely undrained conditions and ignore the effects of the excess pore water pressure (EPWP). A series of triaxial extension stress path tests were conducted in this article to evaluate the effects of the loading rate on the development of EPWP and soil strength. The soil specimens were consolidated under pressures of 60, 80, and 100 kPa and then unloaded at seven different loading rates. It is found that the EPWP and soil strength are heavily influenced by the loading rate. The EPWP tends to be negative at small axial strain and then increases to be positive with the increase of axial strain. The normalized deviatoric stress versus loading rate curves are in the backbone curve. The minimum deviatoric strength happens when the normalized loading rate V-ref=5 and linearly increases with the increase of consolidation pressure with the slope of -0.715. The magnitude of the slope of the critical state line in p ' - q space is heavily influenced by the loading rate.