Simulating Shear Rate-Dependent Undrained Stress-Strain Behaviour of Natural Sedimentary Clay at Kobe Airport

Abstract

Effects of strain rate on undrained shear behaviour of seabed Holocene clay at Kobe airport site were examined in a series of triaxial compression and extension tests performed using different rate of axial straining. A comparative compression test in which the strain rate was changed in steps was also carried out. Similar tests were performed in constant-volume direct shear box (DSB) test. It was found that the undrained strength increased with increasing shear rate and increasing consolidation period. Isotach properties seemed a key to govern the undrained shear behaviour. The behaviour can be described such that the stress-strain response as well as the development of excess pore pressures was uniquely related to the axial strain rate, for which softer and more contracting response was examined when the rate of axial strain decreased, and vice versa as the axial strain rate increased. In this paper, a type of Isotach stress-strain response of the clay, together with the development of drained creep strain with time was successfully simulated by newly developed models.