Liquefied strength ratio with stress densification and low stresses

Abstract

This paper presents a comparison of four assumptions or approaches for using a liquefied shear strength ratio for sandy soils in cases where there has been a large increase in effective vertical stress, e.g., structure raising or remedial measure, that is outside the effective stresses of the case histories used to develop the empirical liquefied shear strength ratio and penetration resistance correlations. Changes in penetration resistance due to an increase in effective vertical stress are used in an example to illustrate the following four assumptions for determining a liquefied shear strength ratio in such a post-liquefaction stability analysis: (1) initial effective vertical stress and initial penetration resistance; (2) initial effective vertical stress and the expected increase in penetration resistance due to the increase in effective vertical stress; (3) final effective vertical stress and initial penetration resistance, which is suggested; and (4) final effective vertical stress and final penetration resistance. This paper also presents suggestions for using a liquefied strength ratio at low effective vertical stresses, e.g., approaching the toe of a dam or embankment, in a post-liquefaction stability analysis.