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North Natomas Library
4660 Via Ingoglia
Sacramento, CA 95835
(916) 264-2700

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Wednesday, May 23, 2018, 6:30 PM - 8:30 PM PDT
Category: Emerging Professionals

Northern California Emerging Professionals Meeting

Tsunami-induced Soil Instability

By Abbas Abdollahi, AECOM

Presentation Synopsis:

Tsunami loading can cause sediment instability, which can compromise the structural integrity of coastal buildings and infrastructure. To understand the process by which a tsunami can cause sediment instability, it is necessary to understand how the pore water pressure in the soil changes during tsunami loading. Understanding how tsunami-induced excess pore water pressure gradients form is not straightforward given the loading timescale and seepage effects. Based on the changes in pore water pressure due to overlying water and seepage of infiltrating water during a tsunami, a deformation model was developed and coupled with a seepage model. The proposed seepage-deformation model is able to model the broad range of drainage conditions of a soil bed from the fully undrained condition to the fully drained condition. The coupled seepage-deformation model is formulated and implemented in MATLAB using the finite difference method. The coupled seepage-deformation model is used to perform numerical experimentation after a convergence study is performed. The numerical experimentation focuses on saturated and unsaturated soil conditions with linear and nonlinear soil constitutive models. The presented model is applied to field data collected at Kesen-numa Bay, Japan, during the 2011 Japan tsunami in combination with the beach sand of Newport, Oregon, United States. The upward and downward gradient effect on surface water flow and surface soil grain are investigated. In this study, Shields 1936 work is extended to include the importance of soil particle shape and flow gradient induced by tsunami. The results show the dependence of the tsunami-induced excess pore water pressure head gradient on the tsunami water’s weight and the compressibility of the pore water. The results show the importance of modelling the tsunami-induced deformation, the partial drainage condition, and the pore fluid condition when considering tsunami-induced pore water pressures in soil beds. The results imply that different mitigation schemes to protect coastal structures may be specified given the local beach sand conditions.

Speaker Bio:

Abbas Abdollahi is a staff engineer at AECOM Sacramento. He received a B.Sc. degree in Civil Engineering as well as a M.Sc. degree in Soil Mechanics and Foundation Engineering from Shiraz University, Shiraz, Iran. Abbas got his PhD in Civil Engineering in 2017 from Oregon State University. His research focuses on wave-induced liquefaction, earthquake-induced liquefaction, soil-wave interaction, geo-coastal engineering, geotechnical earthquake engineering, unsaturated soil mechanics, and theoretical and numerical modelling.

Suggested Donation:

Professionals $20, Students Free!


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Register by Noon May 22, 2018 
Casual dinner included. 




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