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

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

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

Realities of bridge resilience in Small Island Developing States

Small Island Developing States (SIDS) are acknowledged as particularly vulnerable to extreme climate events; however, the realities for transport infrastructure and bridges are still poorly studied. Assessing bridges in this context can be challenging due to data scarcity, a lack of local standards, and uncertainty due to climate change. While bridges are designed to connect transport networks, they also carry energy, water, and communication networks, making them critical cascading failure points worthy of special attention in terms of risk assessment and resilience measures. We explore what resilience actually means for the design and management of SIDS bridge infrastructure by applying a post disaster forensics and systems approach that is not reliant on complex methods or large amounts of data. To demonstrate the practicality of our approach, we apply it to the island of Dominica, which is regularly impacted by both tropical storms and hurricanes. Our results document the extreme conditions for infrastructure and nearby settlements and the complex interrelated physical processes that occur during these events. We reflect on the implications for design approaches for bridges under these conditions and detail specific recommendations on how the resilience of existing and new bridges can be enhanced through practical measures that are achievable, even within the constraints experienced by those managing bridge infrastructure in SIDS contexts. This work adds to the growing number of studies exploring forensic disaster investigation and systems thinking, but is the first to explore bridge resilience in SIDS

H-pile driving induced vibrations: reduced-scale laboratory testing and numerical analysis

Ground vibrations due to impact pile driving operations can become a major concern when affecting nearby structures and underground utilities. In an effort to better understand the transmission and dissipation of energy into the ground during impact pile installation, reduced-scale pile driving tests were conducted in an indoor cylindrical (6.5 m diameter and 1.8 m deep) sand pit at the University of Michigan. Sensors were placed at various depths from the ground surface and distances from the driven pile to record ground motions. In addition, the model pile was equipped with the pile driving analyzer (PDA) system to accurately assess the energy transfer from hammer to pile. The pile installation process was then simulated using 3D finite element (FE) dynamic analyses. The combination of ground vibration monitoring data and records of the impact force from the PDA testing collected from the small-scale pile driving tests in a controlled laboratory environment, offer a great opportunity to validate the numerical code. The recorded ground motion measurements from the impact driving of the model pile are compared with the calculated velocity-time histories from the FE numerical simulation of the pile driving test. Both measured and calculated ground motions verify the hypothesis of the wave propagation field generated by impact driven piles, as presented by Woods (1997)

Shear strength of municipal solid waste

While the engineering profession\u27s understanding of the response of municipal solid waste (MSW) to monotonic and cyclic loadings has improved over the past two decades, several important issues remain unresolved. Characterization of the shear strength of MSW is a critical step in performing reliable static and seismic stability analyses of landfills. Landfill stability analyses can be no more reliable than the reliability of the engineer\u27s estimate of the shear strength of the waste. Furthermore, the stress-strain response of MSW needs to be considered to provide compatibility between the mobilized shear strength and the level of deformation along potential failure surfaces. Relevant studies of MSW shear strength are summarized in this state-of-knowledge chapter. Large-scale laboratory test data, which includes direct shear (DS), triaxial (TX), and simple shear (SS) test results, and back-analyses of failed and stable landfill slopes in the field are considered. Findings from a recent comprehensive study by Zekkos (2005) are emphasized. There is large variability in the shear strength of MSW reported in the literature. Obstacles to characterizing the shear strength of MSW include its age, heterogeneity and the difficulty in recovering and testing representative waste samples due to the large size of some waste constituents. Differences in testing procedures employed and in the assumptions made when interpreting the test results also contribute to the variability of the shear strength of MSW. A consistent conceptual framework to perform and to evaluate the results of the laboratory and in-situ tests performed on MSW is required. It is hoped that the recommendations provided as part of the first International Waste Mechanics Symposium will address this issue and work toward providing a common framework for advancing the profession\u27s understanding of waste properties and mechanics through developing consensus on the performance and reporting of laboratory and field testing procedures. Published data reported in the literature on the shear strength of MSW are discussed in sections on large-scale tests and back-analyzed assessments. This literature review does not provide complete descriptions of the works completed by researchers, as this information is available in detail in the referenced papers. Instead, key findings are summarized. Following the literature review, a summary of the state-of-knowledge of MSW stress-strain response and strength is presented and recommendations are made for developing a consistent framework for performing and reporting shear strength data on MSW. Currently unresolved issues are also identified. © ASCE 2008

COMPARISON OF UAV-ENABLED PHOTOGRAMMETRY-BASED 3D POINT CLOUDS AND INTERPOLATED DSMs OF SLOPING TERRAIN FOR ROCKFALL HAZARD ANALYSIS

UAVs are expected to be particularly valuable to define topography for natural slopes that may be prone to geological hazards, such as landslides or rockfalls. UAV-enabled imagery and aerial mapping can lead to fast and accurate qualitative and quantitative results for photo documentation as well as basemap 3D analysis that can be used for geotechnical stability analyses. In this contribution, the case study of a rockfall near Ponti village that was triggered during the November 17th 2015 Mw 6.5 earthquake in Lefkada, Greece is presented with a focus on feature recognition and 3D terrain model development for use in rockfall hazard analysis. A significant advantage of the UAV was the ability to identify from aerial views the rockfall trajectory along the terrain, the accuracy of which is crucial to subsequent geotechnical back-analysis. Fast static GPS control points were measured for optimizing internal and external camera parameters and model georeferencing. Emphasis is given on an assessment of the error associated with the basemap when fewer and poorly distributed ground control points are available. Results indicate that spatial distribution and image occurrences of control points throughout the mapped area and image block is essential in order to produce accurate geospatial data with minimum distortions