Variability in Earthen Levee Seismic Response Due to Time-History Selection

In seismic slope stability analyses the single most important input parameter is the ground motion. Time-history selection is a challenging engineering problem since the variability in ground motion characterization is in part due to the complexity of the mechanisms that result in a seismic event taking place and the path and soil conditions from the origin of the seismic event to the location of interest. In this study, the effect of key ground motion parameters to the dynamic response of earthen levees is investigated. Specifically, the effect on the induced cyclic shear stress ratio (CSR) and/or seismically induced Newmark-type, permanent displacements (U) for prescribed sliding surfaces is discussed. Results were obtained by performing 2-D equivalent linear finite element dynamic analyses for a total of 1,000 ground motions. The mean period, Tm, of the ground motion, and the peak ground velocity, PGV, are among the parameters identified by this study as being good indices for seismic levee response. Identifying the parameters that correlate best with the variability in response will allow the formulation of time-history selection criteria for the seismic response of earthen levees

The May 25th 2011 railroad embankment failure in Ann Arbor, Michigan, as a means for teaching geotechnical engineering

A 30-m long railroad embankment failure that occurred on May 25 2011 in the city of Ann Arbor, Michigan, is presented. Emphasis is given on the field observations of the failure, the characterization of the site conditions and the seepage and slope stability analyses, all of which represent important components of the training and practice of a geotechnical engineer. The failure occurred following a record wet season that resulted in ponding water against the embankment and high enough water pressures and exit gradients that resulted in instability of the railroad embankment. Detailed background material and the methodology for using the case history in geotechnical engineering education are presented

Newmark-Type Pseudo-Three-Dimensional Back-Analysis Of Co-Seismic Landslides In Egkremnoi, Lefkada, Greece

A pseudo-three-dimensional (pseudo-3D) methodology to back-analyze coseismic landslides was developed and applied to 68 mapped landslides, which occurred over approximately 1 km2area in Egkremnoi, Greece, during the 2015 Mw6.5 Lefkada earthquake. The methodology is based on a one-dimensional (1D) Newmark-type sliding block model to assess instability and a spatial projection in 3D topography to derive landslide geometry. The strength parameters for modeled landslides that best match the landslide location, area, and volume were derived through an iterative scheme that optimizes the match using predefined matching criteria. The range of different-sized landslides produced shear strength estimates from ~10 to 300 kPa and led to the derivation of a regionally averaged strength envelope characterized by a cohesion of 6 kPa and a friction angle of 53° for the highly fractured limestones that are encountered in this area. Compared to previous full 3D slope stability analyses in this area, the friction angle using this methodology was found to be generally consistent, but the cohesion was lower. The presented methodology can provide a computationally efficient method to estimate the average shear strength of a geologic unit over large areas, especially where extensive field and laboratory tests on the materials are unavailable or difficult to conduct

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

General Report - Session 5

This General Report summarizes the papers submitted to Session 5 titled “Case Histories and Failure of Geological, Rock and Mining Engineering, including Underground Structures and Excavations, and Subsidence of Deltas, Anticipation, Characterization, Design and Construction in the Geological Complexity of Mélanges, Fault Rocks, Weathered Rocks, Boulder Colluvium, Lahars, and Similar Bimrocks (Block-in-Matrix Rocks) and Rock/Soil Mixtures.” A total of eleven papers covering the broad session themes described above were submitted. The geographic distribution of the case histories is listed in Table 1. Overall, five papers were submitted from Asia, two from Africa, two from North America, and two from Europe

Regional 3D Stability Analyses Of The Egkremnoi Coastline And Comparison With Landslides Caused By The 2015 Lefkada Earthquake

Regional three-dimensional (3D) forward modeling stability analyses are presented for the Egkremnoi coastline of Lefkada Island in Greece. The pre-earthquake 5-m resolution DEM of the region was used as input for the regional 3D model and the modeling results were evaluated for five large landslides that occurred in the area during a Mw 6.5 earthquake that occurred in 2015. The area ratio and the overlap area ratio were defined to quantitatively assess the geospatial match between predicted and mapped landslides. Parametric analyses using variable material strength and DEM resolution were subsequently conducted to assess the influence of the input on the estimates of factor of safety, geometry, and location for the predicted most critical landslide. For the cases studied here, the assumed material strength has a greater influence on the factor of safety compared with DEM resolution. However, we find that the DEM resolution has a more pronounced influence on the location and size of predicted landslides

Response of municipal solid waste to mechanical compression

The compressibility of municipal solid waste (MSW) is of engineering interest as it affects the short-term and long-term performance of landfills, as well as their expansion, closure, and postclosure development. An assessment of the field settlement behavior of MSW can be reliably executed only when the various mechanisms contributing to the settlement are properly taken into account. A comprehensive large-size experimental testing program that involved a total of 143 one-dimensional compression tests from five landfills, in Arizona, California, Michigan, and Texas of the United States as well as Greece was executed to systematically assess the compressibility characteristics of MSW subjected to a compressive load. Emphasis is given to the influence of waste structure, waste composition, unit weight, and confining stress on the compressibility parameters that are used in engineering practice, such as the constrained modulus and compression ratio, as well as long-term compression ratio due to mechanical creep only. The effect of waste composition and unit weight on the compressibility parameters is quantified. It is also found that the type of waste constituent (i.e., paper, plastic, or wood), as well as the waste’s anisotropic structure can have an effect on the compressibility characteristics of soil-waste mixtures. The proposed relationships can be used to estimate compressibility parameters of MSW at any degradation state as long as the waste composition and unit weight are known

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