Liquefaction Analysis of Sands: Some Interpretation of Seed\u27s K\u3csub\u3eα\u3c/sub\u3e (Sloping Ground) and K\u3csub\u3eσ\u3c/sub\u3e (Depth) Correction Factors Using Steady State Concept
Seed\u27s Liquefaction Assessment Chart (SLAC) correlates the corrected SPT blow count (N1)60 to the cyclic stress ratio required to cause liquefaction for free field level ground conditions. However, the cyclic stress ratio or the liquefaction resistance of a soil under sloping ground (initial static shear) and at depth (high confining pressure) would be significantly different from that derived from the SLAC. To correct the liquefaction resistance for the initial static shear and confining pressure, factors Kα and Kσ are used respectively. The factors have significant influence on the evaluation of liquefaction resistance against earthquake loading and therefore on the final outcome of the design of the structure. The corrections that are available in the state-of-the-art literature and used by the industry are empirical and inappropriate. The Kα and Kσ factors can vary profoundly depending on the initial state of the soil in the q-p-e (stress/void ratio) space and its stress path being in the dilative or contractive domain of the state boundary surface. In this paper, it is demonstrated that it is possible to correlate the correction factors Kα and Kσ to some fundamental parameters, (state parameter, ψ) that govern the strength-deformation of soils using critical/steady state principles
