4/24/212 Geotechnical aspects of the M8.8 21 Maule, Chile earthquake Scott M. Olson, PhD, PE Associate Professor University of Illinois at Urbana-Champaign 212 EERI Annual Meeting & National Earthquake Conference April 1-13, 212 Memphis, Tennessee 1 Acknowledgments Geo-engineering Extreme Event Reconnaissance (GEER) (PIs: Jon Bray, Ellen Rathje, David Frost) Chile team: Jon Bray, Terry Elderidge, David Frost, Pedro Arduino, Scott Ashford, Dominic Assimaki, Youssef Hashash, Tara Hutchinson, Laurie Johnson, Keith Kelson, Robert Kayen, Christian Ledezma, Robb Moss, George Mylonakis, Scott Olson, Kyle Rollins, Nicholas Sitar, Jonathan Stewart, Alfredo Urzua, Ramon Verdugo, Rob Witter, and Nick Zoa National Science Foundation RAPID program 2 1
4/24/212 M8.8 February 27, 21 Maule, Chile earthquake 7th largest earthquake since 19 37, residences; 4, schools; 79 hospitals; 4,2 boats damaged or destroyed 2 bridges damaged including 2 with one or more collapsed spans 1.8 million people (1/8 of population) affected by earthquake, with 8, displaced Fault rupture km long and 1 km wide ~ $3B in economic losses 1% of GDP Shaking intensities 2
4/24/212 Distribution of liquefaction effects Earthquake Moment Magnitude (M) 9. 8. 7. 6.. Distribution of liquefaction effects Ambraseys (1988) magnitude bound relation using distance to fault Haiti earthquake Epicentraldistance Haiti earthquake Distance to fault Epicentral distance for shallow to intermediate depth earthquakes (focal depth < km) Epicentral distance for intermediate to deep earthquakes (focal depth > km) Distance from fault feature for all depth earthquakes 4. 1 1 1 1 Distance to Most Distal Liquefaction Site (km) Chile earthquake Distance to fault Ambraseys (1988) magnitude bound relation using epicentral distance Chile earthquake Epicentraldistance 6 3
4/24/212 Effects of liquefaction on bridges Many bridges damaged by liquefaction and lateral spreading were located along the Bio-bio River Concepción La Mochita Llacolén Puente Viejo Bio Bio Railroad Juan Pablo II San Pedro de la Paz 7 Llacolen bridge Measured pga ~.4g (downtown Concepcion) 8 4
4/24/212 Llacolen bridge 1 1 1 1 1 1 1 1 1 1 1 1 2 2 2 2 2 2 2 2 2 2 2 2 3 3 3 3 3 3 3 3 3 3 3 3 4 4 4 4 4 4 4 4 4 4 4 4 S-6 1 1 1 1 1 1 1 1 SR-3 SR-4 SJ-2 SR-2 2 2 2 2 2 2 2 2 SJ- SJ-6 SR-1 SJ-7 3 3 3 3 S-7 3 3 3 3 4 4 4 4 4 4 4 4 9 Llacolen bridge 1
4/24/212 La Mochita bridge 11 La Mochita bridge 12 6
4/24/212 Effects of liquefaction at ports Several ports and wharfs damaged by liquefaction and lateral spreading, particularly Port of Coronel and Port of Concepcion Conversely, several ports suffered little to no damage, particularly Port of Valparaiso and Port of San Antonio 13 Port of Coronel 14 7
4/24/212 Port of Coronel 1 Port of Coronel 16 8
4/24/212 Dams & tailings facilities Overall, dams and tailings facilities performed well However, Las Palmas tailings dam suffered a massive liquefaction flow failure, killing a family of four (the facility operator) 17 Las Palmas tailings dam 18 9
4/24/212 Las Palmas tailings dam Dynamic Cone Penetration Test (DCPT) Blow Count 1 2 3 4 Tailings 2 Dynamic Cone Penetration Test (DCPT) Blow Count 1 2 3 4 Tailings (failed mass) 2 4 1 4 1 Depth below Ground Surface (ft) 6 8 1 12 14 2 3 4 Depth (m) Depth below Ground Surface (ft) 6 8 1 12 14 2 3 4 Depth (m) Natural soils? 16 16 18 18 2 6 2 6 19 Building performance Overall, well-engineered buildings performed adequately However, GEER investigated two notable sites where buildings settled and tilted as a result of liquefaction 2 1
4/24/212 Curanilahue regional hospital 21 Curanilahue regional hospital Measured pga ~.3g (downtown Curanilahue) 22 11
4/24/212 Condominio Los Presidentes in Concepcion 23 Condominio Los Presidentes in Concepcion 24 12
4/24/212 Condominio Los Presidentes in Concepcion 2 Conclusions Widespread liquefaction in alluvial deposits and artificial fill consisting of clean sands to sandy silts Bridges along Bio-bio River near Concepcion suffered significant damage, leaving no bridges fully functional Important ports closest to epicenter suffered significant liquefaction and lateral-spreading induced damage Particularly important liquefaction flow failure occurred at large tailings facility Liquefaction-induced building settlement and tilting occurred in silty soils 26 13