Theme Lecture – Liquefaction of gravelly soils and the impact on critical infrastructure
A. Athanasopoulos-Zekkos, Associate Professor of Civil and Environmental Engineering, UC Berkeley, USA
Our natural and built environment continues to be threatened by grand challenges such as urbanization, climate change, as well as natural and man-made hazards. At the same time, infrastructure performance requirements are increasing, and engineering methods of the past are no longer adequate. As Civil and Environmental Engineers, we are called to enhance infrastructure resiliency of our often aging or outdated infrastructure by developing new methodologies that are supported by emerging technologies, improved constitutive models, increased computational capabilities and smart and sustainable materials.
Civil infrastructure interacts with soils, either as foundation materials or backfill, or consists of soils (e.g. dams, levees). Understanding the behavior of such materials, in particular materials such as gravelly soils, is critical in assessing the response of geotechnical systems such as flood protection systems (dams, levees), or transportation systems (bridges, ports) among others. Gravelly soils however are challenging to characterize both in the field and the laboratory due to their particle size. Recent earthquakes (Mw=7.9 2008 Wenchuan, China, Mw=6.1 2014 Cephalonia, Greece, Mw=7.8 2016 Kaikoura, New Zealand) have shown that gravelly soils can and will liquefy during earthquakes and have the potential to cause significant damage to infrastructure. To date, most research in soil liquefaction has focused on sands, as they have been observed to liquefy in the field and can be readily tested under controlled conditions in the laboratory. Results from ongoing research will be presented on evaluating the seismic and post-seismic response of gravelly soils by combining unique laboratory experiments (large-size cyclic simple shear, shear wave velocity measurements), high end numerical modeling using the Discrete Element Method, field testing (MASW and Dynamic Penetration Testing) and back-analyses of well documented case histories with the goal of developing a unified and robust approach for soil liquefaction analysis that integrates material behavior from micro (particle-to-particle) to macro-scale (infrastructure).