Deep Supported Excavation in Difficult Ground Conditions in the City of Patras, Greece — Measured vs. Predicted Behavior

The technical characteristics of a deep supported excavation project using anchored diaphragm walls and the measured (by inclinometers) behavior of the soil retaining system are presented. The measured behavior is then compared with the predicted behavior using a finite element model of the excavation. The comparison shows a good agreement in a location where the soil profile is well defined. However, differences in the magnitude of the displacements were observed when the information on the soil profile was incomplete due to the variability of the deposits on site

Earthquake science in resilient societies

Earthquake science is critical in reducing vulnerability to a broad range of seismic hazards. Evidenceâ based studies drawing from several branches of the Earth sciences and engineering can effectively mitigate losses experienced in earthquakes. Societies that invest in this research have lower fatality rates in earthquakes and can recover more rapidly. This commentary explores the scientific pathways through which earthquakeâ resilient societies are developed. We highlight recent case studies of evidenceâ based decision making and how modern research is improving the way societies respond to earthquakes.Key PointsThe level of seismic risk depends in part on societal investment in earthquake scienceMultidisciplinary investigations involving earthquake scientists and engineers greatly reduce casualties in earthquakesRecent examples highlight the utility of earthquake science in building resilient societies and the need for further research to reduce seismic riskPeer Reviewedhttps://deepblue.lib.umich.edu/bitstream/2027.42/137197/1/tect20552_am.pdfhttps://deepblue.lib.umich.edu/bitstream/2027.42/137197/2/tect20552.pd

New Orleans and Hurricane Katrina. III: The 17th Street Drainage Canal

The failure of the levee and floodwall section on the east bank of the 17th Street drainage canal was one of the most catastrophic breaches that occurred during Hurricane Katrina. It produced a breach that rapidly scoured a flow pathway below sea level, so that after the storm surge had largely subsided, floodwaters still continued to stream in through this breach for the next two and a half days. This particular failure contributed massively to the overall flooding of the Metropolitan Orleans East Bank protected basin. Slightly more than half of the loss of life, and a similar fraction of the overall damages, occurred in this heavily populated basin. There are a number of important geotechnical and geoforensic lessons associated with this failure. Accordingly, this paper is dedicated solely to investigating this single failure. Geological and geotechnical details, such as a thin layer of sensitive clay that was laid down by a previous hurricane, proper strength characterization of soils at and beyond the toe of the levee, and recognition of a water-filled gap on the inboard side of the sheet pile cutoff wall are judged to be among the most critical factors in understanding this failure. The lessons learned from this study are of importance for similar flood protection systems throughout other regions of the United States and the world

Geologic Conditions underlying the 2005 17th Street Canal Levee Failure in New Orleans

A careful program of subsurface sampling and cone penetration test soundings was employed to characterize the geologic conditions beneath the failed portion of the 17th Street Canal levee in New Orleans, where a 150 m long section of the levee and floodwall translated up to ~16 m when flood waters rose to 1-2 m of the wall\u27s crest on August 29, 2005, during Hurricane Katrina. The subsurface conditions are characterized by discrete layers of fill placed upon the historic cypress swamp, which is underlain by a deeper, prehistoric cypress swamp. These swamp deposits were consolidated beneath the levee, and in the area of the 2005 failure, the swamp materials infilled a natural depression believed to be an old slough, which dipped below the sheetpile tips for a distance of about 50 m, which corresponds to where the breach appears to have initiated. Detailed examination of the recovered soils suggest that recent hurricanes periodically inundated the swamps with saline and/or brackish water, which cause a mass dieoff of swamp vegetation and flocculation of suspended clays, due to the sudden increase in salinity. These conditions promote deposition of discontinuous clay seams beneath layers of organics, which are then covered by fresh water swamp deposits. This sequence is repeated, like a series of tree rings, throughout the swamp deposits. The cypress swamp deposits lying beneath the levee also exhibit high hydraulic conductivity. These materials contain corky wood, and recovered samples often exhibited densities less than water. Nine of the post-Katrina borings recovered intact samples of a basal rupture surface comprised of organic silty clay exhibited near zero residual shear strength after shearing 80 to 100 mm

New Orleans and Hurricane Katrina. II: The Central Region and the Lower Ninth Ward

The failure of the New Orleans regional flood protection systems, and the resultant catastrophic flooding of much of New Orleans during Hurricane Katrina, represents the most costly failure of an engineered system in U.S. history. This paper presents an overview of the principal events that unfolded in the central portion of the New Orleans metropolitan region during this hurricane, and addresses the levee failures and breaches that occurred along the east-west trending section of the shared Gulf Intracoastal Waterway/Mississippi River Gulf Outlet channel, and along the Inner Harbor Navigation Channel, that affected the New Orleans East, the St. Bernard Parish, and the Lower Ninth Ward protected basins. The emphasis in this paper is on geotechnical lessons, and also broader lessons with regard to the design, implementation, operation, and maintenance of major flood protection systems. Significant lessons learned here in the central region include: (1) the need for regional-scale flood protection systems to perform as systems, with the various components meshing well together in a mutually complementary manner; (2) the importance of considering all potential failure modes in the engineering design and evaluation of these complex systems; and (3) the problems inherent in the construction of major regional systems over extended periods of multiple decades. These are important lessons, as they are applicable to other regional flood protection systems in other areas of the United States, and throughout much of the world