A Review of the Influence of Initial State Shear (K\u3csub\u3eα\u3c/sub\u3e) and Confining Stress (K\u3csub\u3eσ\u3c/sub\u3e) On Failure Mechanisms and Earthquake Liquefaction of Soils

Geotechnical engineering profession has continued to use the in situ measurement based empirical procedure to perform soil liquefaction analysis. This method was initially developed based on past earthquake performance of level ground sites. For sloping ground and larger depths or confining stress, the method requires appropriate corrections such as Kα for initial static shear and Kσ for confining stress. The recommended correction factors in the current state of practice have been presented by NCEER (National Center for Earthquake Engineering and Research). These recommendations, however, do not distinguish between the distinct shear behavior of soils on the opposite sides of the critical state line. These factors can significantly influence the results and alter the final conclusion and outcome of an analysis. This paper reviews the existing soil liquefaction research data focusing on these factors based on the critical state soil mechanics framework. It is shown that the undrained response of soils with stable yielding during both monotonic and cyclic loading can be correlated with the distance of the initial state from the critical state line. Kα and Kσ are shown to correlate well with this distance. Constant cyclic resistance ratio lines are found to lie parallel to lines of constant initial state. Furthermore, Kσ variation is found to be material specific