Stress Scaling Factors for Seismic Soil Liquefaction Engineering Problems: A Performance-Based Approach

Most of the widely used seismic soil liquefaction triggering methods propose cyclic resistance ratio (CRR) values valid at the reference normal effective stress (σ′_v,0) of one atmosphere and zero static shear stress (τ_st,0) states. Then, a series of correction factors are applied on this reference CRR, for the purpose of assessing the variability due to normal effective and static shear stress states (i.e. K_σ and K_α corrections) acting on the horizontal plane. In the literature, a number of relationships suggested to be used as part of liquefaction triggering methodologies. However, the presence of a wide range of correction factors, some of which with even contradicting trends, suggests that more research needs to be performed to reduce this uncertainty. Additionally, these stress correction factors are treated as being strain-independent and are applied disjointedly to CSR or CRR. The main motivation of this on-going study is defined as to develop a strain-dependent semi-empirical framework to assess combined effects of i) σ′_v,0, ii) τ_st,0 acting on the plane, where cyclic shear stresses either produce iii) shear stress reversal or not. For this purpose, cyclic simple shear tests were performed on laboratory reconstituted sand samples. Additionally, cyclic test data were compiled from the available literature. On the basis of probabilistic assessment of this data, a unified correction scheme, which incorporates the interdependent effects of both overburden and static shear stresses along with the degree of cyclic shear stress reversal, has been developed.