Static liquifaction of very loose sands: Reply

Abstract

Discussions 581 The Authors appreciate the interest by the Discussers in the presented work. Chu and Leong point out that different conclusions regarding liquefaction potential may be reached depending on the choice of void ratio used as reference for the evaluation. They suggest that a different conclusion might have been reached if a constant void after consolidation had been employed as background for the comparison of results of undrained tests. They also point out that it is the post consolidation void ratio, ec, that is used to establish the steady state behavior. Isotropic compression tests of four different initial densities of Nevada sand with 6 percent fines content at confining pressures ranging from 20 to 500 kPa are shown in Fig. DR1. The bases of comparisons of the Authors and Discussers are also shown in the figure. The Authors deduced “reverse” behavior on the basis of examining the behavior along an isotropic consolidation line (e.g., the 12 percent initial relative density line as shown in the figure). The Discussers propose using a constant void ratio line as their basis of comparison, as shown in the drawing. However, one observes that the four different isotropic compression lines in Fig. DR1 do not overlap with respect to void ratio in the confining pressure ranges that were employed in the study. Therefore, using a constant void ratio basis of comparison was not possible. However, the Authors believe that the conclusion drawn from their basis of comparison data is correct. The test specimens for each of the two series of cited tests had the same initial void ratio before isotropic compression (e.g., all tests were on the same isotropic compression line). The Authors are not aware of any reported test results on loose clean sands that show this reverse pattern of behavior when sheared from the same isotropic compression line at different confining pressures. The conventional pattern of undrained behavior of clean sands when sheared from the same isotropic compression line is shown in Fig. DR2. The schematic p′–q diagram shows effective stress paths exhibiting the three different types of behavior patterns associated with clean sands (Yamamuro and Lade 1997). They are (1) stable behavior at low confining pressures; (2) temporary instability at intermediate confining pressures; (3) instability behavior at high confining pressures. The pattern of behavior indicates an increasing contractive volumetric tendency with increasing initial confining pressure. Since they were sheared from the same isotropic consolidation line (consolidation void ratios are different), the