P-Wave Reflection Imaging of Laboratory Soil Models

An ultrasonic p-wave reflection imaging system is used to non-invasively image submerged soil models with embedded anomalies and complex geometric layer contacts. The ultrasonic transducers emit compressive waves into water that subsequently transmit into the underlying soil, and measurements of the reflections are used to construct the images. Properties of the transducers and data acquisition hardware and software are explained. A soil model consisting of embedded high- and low-impedance anomalies, dipping soil layer contacts, and an undulating concrete base layer was imaged using 500 kHz transducers. The geometric features of the model are clearly visible in the images

Application of Concave-Up P-Y Elements in Static Analysis of Piles in Laterally Spreading Ground

Concave-up p-y behavior in liquefied sand has been observed by many researchers due to the dilatant tendency of sand that is dense of its critical state being suppressed in undrained loading. However, static analysis method often scale down the concave-down p-y curves that characterize drained loading, thereby missing the potentially important influence of concave-up behavior on pile response. For lateral spreading problems, large shear strains are typically assigned to the liquefied layer, which presupposes that the liquefied sand is soft and weak. This assumption is incompatible with the strengthening, stiffening concave-up p-y material. This paper presents a static lateral spreading analysis of a pile using concave-up p-y materials to demonstrate how this incompatibility can lead to unrealistic results

Modeling Natural Hazards Engineering Data to Cyberinfrastructure

DesignSafe-CI is an end-to-end data lifecycle management, analysis, and publication cloud platform for natural hazards engineering. To facilitate ongoing data curation and sharing in a cloud environment that is intuitive to the end users, developers and curators teamed with experts in the different hazards to design data models and vocabularies that map their research workflows and domain terminology. The experimental data models - six - emphasize provenance through relationships between research processes, data and their documentation, and highlight commonalities between experiment types. They mediate between the user interface and the repository layers of the cyberinfrastructure to automate tasks such as organizing data and facilitating its description. Using data from triaxial experiments, we conducted a user evaluation of the geotechnical data model, both for its fitness to real data and for purposes of data understandability during reuse. The results of the evaluation guided testing and selection of the Fedora 4 repository backend to enhance data discovery and reuse.National Science FoundationTexas Advanced Computing Center (TACC

Analysis of Three Bridges That Exhibited Various Performance Levels in Liquefied and Laterally Spreading Ground

Three bridges supported on deep foundations that exhibited various performance levels in liquefied and laterally spreading ground are analyzed using a beam on nonlinear Winkler foundation method. The performance levels were (1) no measurable foundation deformation, (2) moderate damage, and (3) collapse. Analyses are first performed using the best available information regarding ground motions and free-field lateral spreading surface displacements. Predictions closely match observations when the inputs are well known. The cases are subsequently reanalyzed using a probabilistic forward prediction that incorporates uncertainty in the ground motion, liquefaction triggering evaluation, lateral spreading surface displacement, and structural response. Significant differences in lateral spreading displacements estimated by different methods introduced significant dispersion into predictions of structural response for cases of poor performance in which the piles moved with the spreading soil but had little influence for cases with good performance where the liquefied soil spread around a stiffpile foundation. © 2013 American Society of Civil Engineers