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Szanowni Państwo, w dniu 27 stycznia 2022 r. o godzinie 15.00 (3 PM) w trybie zdalnym na platformie ZOOM.us w ramach cyklu wykładów organizowanych we współpracy z Uniwersytetem Auburn, Alabama, USA (kolejny 5 wykład) odbędzie się wykład Pana Jacka Montgomery, PhD, PE (Civil and Environmental Engineering, Auburn University, Alabama) oraz Pana Michaela Kiernana, PhD (Lecturer, General Engineering, Clemson University, South Carolina). Poniżej szczegółowe informacje na temat zakresu poruszanej tematyki i prelegentów. Planowany czas wystąpienia: 45 min. + ok. 15 min. dyskusji.

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Cyclic softening of fine-grained soils: Fourth Avenue landslide and the San Fernando dams

by

Jack Montgomery, PhD, PE¹ and Michael Kiernan, PhD²

¹ Assistant Professor, Civil and Environmental Engineering, Auburn University, Alabama
² Lecturer, General Engineering, Clemson University, South Carolina

Summary:

Cyclic softening of fine-grained soils poses a significant hazard to geotechnical infrastructure in many parts of the world. Methods to numerically evaluate the cyclic softening and subsequent localization behavior in clays in practice are less developed than techniques to model liquefaction-induced strength loss of granular soils. The PM4Silt constitutive model can model the dynamic response of low plasticity silts and clays while being relatively easy to calibrate and use in practice. This paper investigates the ability of PM4Silt to model earthquake-induced deformations caused by strain softening of mildly sensitive clays in three case histories, the Fourth Avenue landslide and the Upper and Lower San Fernando dams. The Fourth Avenue landslide in Anchorage occurred in a sensitive clay layer and was initiated by the 1964 Great Alaska Earthquake. The Upper and Lower San Fernando dams were shaken by the 1971 San Fernando earthquakes and have served as important case histories for geotechnical earthquake engineering for nearly 50 years. Liquefaction of the hydraulic fill in the upstream shell is the widely agreed primary cause of the slide at the Lower San Fernando dam, but most analyses have neglected potential cyclic softening within the cores of these dams. Results from previous studies are used to estimate stratigraphy and relevant soil properties. The model calibration procedures and results will be discussed. Simulation results using PM4Silt will be compared to the observed displacements. The effects of different model calibrations are studied as well as the influence of input motion and mesh density. The results demonstrate that PM4Silt can capture the general response of these case histories. Accurately representing the response of these materials is essential to ensuring that accurate deformation estimates are obtained for use in designing remediations or performing risk assessments.

Bio-notes:

Jack Montgomery PhD, PE is an Assistant Professor at Auburn University. His research and teaching primarily focus on engineering geophysics, geotechnical earthquake engineering, landslides, dams, and advanced site characterization. He received his bachelor's degree in Civil Engineering from California Polytechnic State University, San Luis Obispo and his master's and Ph.D. in Civil Engineering from the University of California, Davis.

Michael Kiernan, PhD is a Lecturer in the Department of General Engineering at Clemson University in South Carolina. He earned his bachelor's degree in Civil Engineering from UC Davis in 2015 and his M.S. and Ph.D. from Auburn University. He joined Clemson University in 2021. His research focuses on improving numerical methods for modeling slope stability problems involving strain softening clays subjected to seismic loading.