3-D LIQUEFACTION ANALYSIS CONSIDERING A LARGE DEFORMATION

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From the field observation of liquefaction and ground deformation due to Hyogoken Nambu Earthquake, it was found that that larger deformation occurred near the quay wall. The observed data show that liquefaction analysismethod that can describe large deformation is necessary. In the present study, we have proposed a liquefaction analysis method using an elasto-viscoplastic constitutive model based on finite deformation theory. From the application of the proposed model to the behaviors of quay wall and the foundation beneath embankment it was found that the liquefaction analysis method based on the finite deformation theory is well applicable to predict the liquefaction induced deformation.So far u-p(displacement-pore water pressure) formulation has been used in the 3D- finite deformation analysis method. In the present study we introduced u-w-p(displacement-relative acceleration-pore water pressure) formulation to develop a new method. By considering a relative acceleration between so … More il and pore fluid, we can analyze more accurately liquefaction problems for the problem with higher frequency wave and higher permeability coefficient.In order to study soil-structure interaction problems in the liquefiable ground, the process of the damage to the pile foundation adjacent to quay wall on the reclaimed land during the 1995 Hyogoken Nanbu earthquake wasnumerically analyzed. Two dimensional and three dimensional effective stress analyses using a soil-pile-building model was conducted on a damaged building. The five stories building tilted toward to sea due to serious damage to the pile foundations. Sand boils and large lateral spreading due to liquefaction were observed around the building. We used an effective stress code based on two phase mixture formulation, which was incorporated with a cyclic elasto-plastic model for sand and a cyclic elasto-viscoplastic model for clay. 2-D and 3-D simulation quantitatively reproduced the observed deformation mode of damaged piles. The simulated results show that the inertia force of the building caused the damage at the top of piles and the large horizontal deformation of thereclaimed soil caused the damage at the piles in the reclaimed ground layer before liquefaction of the reclaimed layer.At present the ground surface and near-surface motions are obtained using several numerical methods whichare based on various assumptions as to the material properties and response. The necessary soil properties required for such numerical predictions are usually obtained from simple methods such as SPT and CPT at the site although soil laboratory test such as cyclic triaxial tests are done sometimes. Better soil testing methods, improvements in in-place in-situ testing of soil properties are required. At University California Davis, many students have worked on the development of the non-destructive electrical method to quantify the soil structure and to establish relationship to engineering properties and behavior. Without an accurate representation of in-situ properties which are representative of the site, it is impossible to evaluate prototype behavior. The in-situ state and constitutive model constants are necessary input parameters for numerical procedures. Our vision is to obtain initial state parameters and constitutive constants representative of site and to verify the numericalprocedures using the results of instrumented site. This approach will enable us to perform Model Base Simulation reliably to predict before the event the response ofsites to earthquakes. From the case studies of Port Island and El Centre, it is found the simulation is possible by this non-destructive characterization methods.A non-linear finite element model is used to account for soil column effects on strong motion. A three-dimensional bounding surface plasticity model with a vanishing elastic region, appropriate for non-liquefiable soils, is formulated to accommodate the effects of plastic deformation right at the onset of loading. The elasto-plastic constitutive model is cast within the framework of a finite element soil column model, and is used to re-analyze the downhole motion recorded by an array at a large scale sismic test(LSST) site in Lotung in Taiwan during the Lotung earthquake of 20 May 1986 as well as the ground motion recorded at Gilory 2 reference site during the Loma Prieta earthquake of 17 October 1989. Results of the analysis show maximum permanent shearing strains experienced by the soil column in the order of 0.15 per cent for the Lotung event and 0.8 per cent for the Loma Prieta earthquake, which correspond to modulus reduction factors of about 30 and 10 per cent respectively, implying strong non-linear response of the soil deposit at the two sites. Less