Confining Pressure-Dependency of Bulk Modulus of Sand During Liquefaction

Abstract

In the elasto-plastic constitutive model, bulk modulus is one of the most important parameters to control the change of effective stress under undrained condition. However, the experimental research on bulk modulus of sand during liquefaction has not been conducted so far. In this paper, therefore, the bulk modulus of Toyoura sand was measured directly during liquefaction using a hollow cylindrical torsional shear testing device equipped with a volumetric strain control device. This study found that the bulk modulus corrected by membrane penetration effect during liquefaction process is constant under relatively high confining pressure, and that the stress dependency of bulk modulus during liquefaction process is different from that during swelling process.

Brittle Faulting at Elevated Temperature and Vanishing Effective Stress

“…(b) Compressibility of sand with effective mean stress from Kwon et al. (2006) (black) and Zoback and Byerlee (1976) (red).…”

“…The same data are shown relative to a third, higher pressure regime (red) in the smaller inset plot in Figure 3a. Similarly, Figure 3b shows the drained compressibility of Toyoura sand, estimated from published values of bulk modulus, K, from Kwon et al (2006) at low effective mean stresses. Pore compressibility is β ϕ = 1/K, and at effective stress between 10 and 100 kPa is between 1 × 10 −2 and 2 × 10 −2 /MPa.…”

“…Although our calculations are based on experimental data of Beeler and Hickman (2015), Been et al (1991), Kwon et al (2006) and Beeler and Lockner (2004), given the diverse phenomenon and conditions of the experiments described in Sections 2, 3 and 4, the uncertain values for the parameters used for cohesion, dilatancy, and poroelasticity, and the somewhat ad hoc construction of the evolution Equation 5a for cohesion, the calculations that follow should be considered both qualitative and speculative. These are proof-of-concept, demonstrating that seismic failure is at least theoretically possible undrained at low effective stress and elevated temperature, even in the presence of shear dilatancy.…”