Robert Kayen | University of California, Berkeley (original) (raw)

Papers by Robert Kayen

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The preceding companion paper presented the updating of the seismic soil liquefaction triggering ... more The preceding companion paper presented the updating of the seismic soil liquefaction triggering relationship of Cetin et al. [1], and compared the resulting updated relationship with the earlier version. In this second paper, a detailed cross-comparison is made between three triggering relationships: (1) Seed et al. [2], as slightly updated by the NCEER Working Group (Youd et al. [3]), (2) Boulanger and Idriss [4], and (3) Cetin et al. [5]. Differences between these three triggering relationships, and the apparent causes of them are examined. Also studied are the impacts of these differences on levels of conservatism with regard to evaluation of liquefaction triggering hazard, and the resulting risks for engineering projects.

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The Next-Generation Liquefaction (NGL) project was launched to (1) substantially improve the qual... more The Next-Generation Liquefaction (NGL) project was launched to (1) substantially improve the quality, transparency, and accessibility of case history data related to ground failure; (2) provide a coordinated framework for supporting studies to augment case history data for conditions important for applications but poorly represented in empirical databases; and (3) provide an open, collaborative process for model development in which developer teams have access to common resources and share ideas and results during model development. Work to date has focused on compiling high-value case histories, developing a database template, and planning for needed supporting studies. We describe the project motivation, explain and illustrate how data resources will be compiled and organized, summarize preliminary results from ongoing data collection, describe needed supporting studies, and review project status and next steps.

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The 2016 Kumamoto earthquake with a moment magnitude of 7.0 (Japanese intensity = 7) that struck ... more The 2016 Kumamoto earthquake with a moment magnitude of 7.0 (Japanese intensity = 7) that struck on April 16 brought devastation in many areas of Kumamoto Prefecture and in parts of Oita Prefecture in Kyushu Region, Japan. The earthquake succeeds a foreshock of magnitude 6.5 (Japanese intensity = 7) on April 14. The authors conducted two surveys on the devastated areas: one during April 16-17, and the other during May 11-14. This report summarizes the damage brought to geotechnical structures by the two consecutive earthquakes within a span of twenty-eight hours. This report highlights some of the observed damage and identifies reasons for such damage. The geotechnical challenges towards mitigation of losses from such earthquakes are also suggested. International Society for Soil Mechanics and Geotechnical Engineering If the quality of the distributed file is not satisfactory for you, please access the ISSMGE website and download an electronic version. www.issmge.org Major Project An overview of the geotechnical damage brought by the 2016 Kumamoto Earthquake, Japan Volume 10, Issue 3

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Shear-wave velocity (V s) offers a means to determine the seismic resistance of soil to liquefact... more Shear-wave velocity (V s) offers a means to determine the seismic resistance of soil to liquefaction by a fundamental soil property. This paper presents the results of an 11-year international project to gather new V s site data and develop probabilistic correlations for seismic soil liquefaction occurrence. Toward that objective, shear-wave velocity test sites were identified, and measurements made for 301 new liquefaction field case histories in China, Japan, Taiwan, Greece, and the United States over a decade. The majority of these new case histories reoccupy those previously investigated by penetration testing. These new data are combined with previously published case histories to build a global catalog of 422 case histories of V s liquefaction performance. Bayesian regression and structural reliability methods facilitate a probabilistic treatment of the V s catalog for performance-based engineering applications. Where possible, uncertainties of the variables comprising both the seismic demand and the soil capacity were estimated and included in the analysis, resulting in greatly reduced overall model uncertainty relative to previous studies. The presented data set and probabilistic analysis also help resolve the ancillary issues of adjustment for soil fines content and magnitude scaling factors.

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Scientific Investigations Report 2012-5133 COVER Photograph of one of the archeological sites in ... more Scientific Investigations Report 2012-5133 COVER Photograph of one of the archeological sites in Grand Canyon National Park where topographic change was investigated. This site (AZ:B:10:0225) has both sand dunes and (in foreground) gully erosion. Inset is the resultant 5-cm gridded output map of topographic change for this site, showing erosion (warm colors) and deposition (cool colors).

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The Carquinez Bridge geotechnical arrays are operated by the California Strong Motion Instrumenta... more The Carquinez Bridge geotechnical arrays are operated by the California Strong Motion Instrumentation Program (CSMIP) and recorded a peak ground acceleration (PGA) of approximately 1.0g at ground surface during the 2014 South Napa earthquake. The recorded PGA was significantly larger than those at the nearby surface sites. This study considers surface and downhole recordings from the additional 28 earthquakes recorded at the same arrays to understand the effects of wave propagation and site response at these arrays. Several site response analyses are performed to understand soil nonlinearity using the observed ground accelerations during the 2014 South Napa sequence. Apparent shear wave velocities are calculated from downhole records, which show clear reduction as ground motion intensity increases. Empirical transfer functions (EFTs) are also calculated in which the resonance frequencies became lower during strong shaking during the 2014 South Napa main shock. The in-situ critical damping ratio appears to be frequency dependent in the soft clay deposits. Lower damping at frequencies greater than about 5 Hz may have contributed to the observed PGA at Array #1 during the main shock.

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The 2016 Central Italy earthquake sequence caused numerous landslides over a large area in the Ce... more The 2016 Central Italy earthquake sequence caused numerous landslides over a large area in the Central Apennines. As a result, the Geotechnical Extreme Events Reconnaissance Association (GEER) organized post-earthquake reconnaissance missions to collect perishable data. Given the challenging conditions following the earthquakes, the GEER team implemented a phased reconnaissance approach. This paper illustrates this approach and how it was used to document the largest and most impactful seismically induced landslides. This phased approach relied upon satellite-based interferometric damage proxy maps, preliminary published reports of observed landslides, digital imaging from small unmanned aerial vehicles (UAVs), traditional manual observations, and terrestrial laser scanning. Data collected from the reconnoitered sites were used to develop orthophotos and meshed three-dimensional digital surface models. These products can provide valuable information such as accurate measurements of landslide ground movements in complex topographic geometries or boulder runout distances from rock falls. The paper describes three significant landslide case histories developed and documented with the phased approach: Nera Valley, Village of Pescara del Tronto, and near the villages of Crognaleto and Cervaro.

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This paper presents new bi-directional elements in Newmark-type earthquake displacement modeling:... more This paper presents new bi-directional elements in Newmark-type earthquake displacement modeling: 2-D-compliance; 2-D-earthquake loading; and 2Dcomputation of displacements. Incorporating flexibility and multi-directionality into the Newmark model, compliance affects are found too greatly amplify or de-amplify displacements, relative to traditional rigid-block analyses. The multi-directional shear stress vector is always greater than the computed vector from traditional dip-slope models. Thus, traditional Newmark models always underestimate computed stresses on the failure plane, often resulting in underestimation of displacements.

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