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Unified assessment of stress scaling factors for liquefaction engineering problems

2014-01-01
Çetin, Kemal Önder
Bilge, H. Tolga
Most of the widely used seismic soil liquefaction triggering methods propose cyclic resistance ratio (CRR) values valid at a reference normal effective stress (σv,0) of one atmosphere, and a zero static shear stress (τst,0) state. Then a series of correction factors are applied to the CRR to account for the effects due to variations from the reference normal effective and static shear stresses (i.e., Kσ and Kα corrections). In the literature exists a number of stress correction factors used for seismic soil liquefaction triggering assessment. However, the presence of a wide range of them, some of which even exhibit 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 ongoing study is defined as to develop a strain-dependent semi-empirical framework to assess combined effects of i) σv,0, ii) τst,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. © 2014 American Society of Civil Engineers.