The time of liquefaction triggering during a strong ground motion can have a large influence on the expected level of foundation and superstructure damage. To enable simple, yet accurate estimates of the triggering time, the build-up of pore pressure needs to be understood in terms of cumulative measures of ground motion intensity. This paper develops a theoretical framework and simple procedure to predict the build-up of excess pore pressure based on the principles of conservation of energy. The liquefaction resistance is first quantified in terms of cumulative absolute change in strain energy, which is shown through the evaluation of experimental cyclic simple shear tests to be insensitive to loading amplitude. A ground motion intensity measure is presented that uniquely calculates the cumulative absolute change in kinetic energy. This intensity measure is then used to provide an exact analytical solution for the cumulative absolute change in strain energy at any depth in a homogenous linear elastic soil deposit using the novel, nodal surface energy spectrum (NSES). A simple reduction to the NSES is proposed for viscous and nonlinear soil deposits, as well as a correction for changes in stiffness between layers of soil. The estimation of strain energy and build-up of pore pressure using the simple NSES method was applied to 500 randomly generated soil deposits using a range of different ground motions and validated against nonlinear total stress and nonlinear effective stress time-history analyses, with the NSES method providing a high level of accuracy. The proposed spectrum based solution provides an efficient and physically consistent procedure for the prediction of excess pore pressure build-up.

This paper investigates the key parameters that influenced the settlement of a case study building on liquefiable soil in Adapazari (Turkey) during the 1999 Kocaeli earthquake. Ground movements in Adapazari caused large devastation, largely attributed to liquefaction of low plasticity silty soil layers underneath buildings on shallow foundations. The case study soil profile was well characterized by in-situ testing as well as laboratory tests from the Adapazari area. This allowed several different estimates of the building settlement to be obtained through different methods and through a variation in upper and lower bound estimates of the soil parameters. The different methods and different soil properties resulted in a wide range of estimates from 0.004 m to 1.6 m for the building settlement, compared to the observed in-situ value of 0.9 m. Even though the results were varied, the estimation of the liquefied strength of the soil appeared to be a key parameter for the settlement of the case study building. A detailed study with the PLAXIS finite-element software and UBC3D-PLM constitutive model, provided a consistent estimate of the final settlement of 0.9 m compared to the in-situ value. However, the limitation due to the enforced 'undrained' conditions during the dynamic phase of the analyses may have resulted in an inaccurate simulation of the pore water pressure and subsequently could have influenced the estimation of settlement. The modeling of the liquefaction settlements under free-field conditions was also considerably less than the re-consolidation settlements that were obtained through simplified procedures, suggesting that the re-consolidation settlement under the foundation was not modelled accurately. The present paper focuses on the assessment of the settlements due to earthquake-induced liquefaction as part of the research being conducted within the European project LIQUEFACT.

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The seismic behaviour of a building on a liquefiable deposit is a complex interaction which involves quantifying both shaking induced damage and permanent ground deformation-related damage. In this paper the key parameters that influence both surface shaking and foundation settlements have been identified as the depth, thickness and liquefaction resistance of an equivalent liquefiable layer. These parameters can be used to develop an 'equivalent soil profile' that is analogous to the equivalent single degree-of-freedom that reduces the complexity of the dynamic response of a building into comparable and easily understood quantities. The equivalent soil profile is quantified independent of the seismic hazard, making it compatible with performance based design and assessment frameworks such that the building and soil profile can be directly assessed at different levels of seismic hazard. Several numerical studies are presented that demonstrate the influence of these key parameters on the ground surface shaking and foundation settlement. A set of criteria are proposed for classifying soil profiles into 22 different soil classes for regional loss assessment. An algorithm was developed for automatically fitting the equivalent soil profile to a cone penetration test trace and issues with the fitting are discussed. Field reconnaissance was undertaken to collect additional data to support existing datasets on the performance of buildings in Adapazari, during the 1999 Kocaeli, Turkey, earthquake (Mw = 7.4). The field case history data was used to investigate the correlation between the depth, thickness and liquefaction resistance of an equivalent liquefiable layer, on the extent of foundation permanent deformation. The case history data showed that in general a shallow, thick and weak liquefiable layer near the surface results in significant settlement but a lack of data for buildings on non-liquefiable deposits and the additional complexities involved with real buildings and soil deposits, meant that the trends observed in the idealised numerical models could not identified in the field case history data set.

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