Assessment of seismic soil liquefaction triggering beneath building foundation systems: Fid-Bau Portal

Assessment of seismic soil liquefaction triggering beneath building foundation systems

Cetin, K. Onder / Unutmaz, Berna / Jeremic, Boris

Abstract Although there exist some consensus on seismic soil liquefaction assessment of free field level soil sites, estimating liquefaction triggering potential beneath foundations still stays as a controversial and difficult issue. Assessing liquefaction triggering potential under mat foundations requires the estimation of cyclic and static stresses and the state of the soil medium. As part of these studies, conventionally used normalized cyclic demand term, cyclic stress ratio, is to be estimated addressing the seismic interaction of overlying structure with foundation soils. For this purpose, three-dimensional, finite difference-based total stress analyses were performed for generic soil, structure and earthquake combinations. A simplified procedure was then developed, which produced unbiased estimates of the representative and maximum soil-structure-earthquake-induced cyclic stress ratio values, an alternative, in the preliminary design stage, or complementary in the final design stage, to 3-D dynamic response assessment of soil and structure systems. Consistent with the available literature, the descriptive (input) parameters of the proposed model were selected as soil-to-structure stiffness ratio, spectral acceleration to peak ground acceleration ratio and aspect ratio of the building. The model coefficients were estimated through maximum likelihood methodology, which was used to produce an unbiased match with the predictions of 3-D analyses and proposed simplified model. Although a satisfactory fit was achieved among CSR estimations, validation of the proposed simplified procedure, further with available laboratory shaking table and centrifuge tests was preferred. The proposed simplified procedure was shown to capture most of the amplitudes and almost all of the variational trends of CSR.

Highlights ► The effects of structures on liquefaction triggering potential are investigated. ► A simplified procedure which estimates representative and maximum CSR SSEI was proposed. ► The procedure is validated using laboratory shaking table and centrifuge tests. ► It is found that SSI does not always beneficially affect liquefaction triggering potential. ► The CSR SSEI depend on (i) σ, (ii) S A(T)/PGA, (iii) h/B, (iv) static stress field and (v) state parameters.