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

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

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

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

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

Characterization of a Weak Rock Mass and Geoengineering Analyses for a Canyon Landfill in Northern California

A case history of extensive 60-m high excavations in a weak rock mass for a canyon landfill in Northern California is presented. The landfill is underlain by the Panoche Formation, a complex series of sandstones, siltstones, claystones, shales and conglomerates, thought to be dominantly turbidites, deposited as sub-sea fan deposits. As part of the design, kinematic analyses were performed, accompanied by two independent approaches used to evaluate the strength of the rock mass. One approach was based on laboratory rock core testing, while the second approach was based on the Hoek and Brown Criterion using mostly field observations. The two approaches yielded consistent results. Characterization of the rock mass indicated a pronounced improvement in the rock structure and the condition of the discontinuities with depth, resulting in an increasing Geologic Strength Index (GSI) with depth. Subsequent analyses performed using a layered Hoek and Brown Criterion allowed further steepening of rock excavations. Comparisons are also made in the results of the analyses using a layered vs. a more commonly used uniform Hoek and Brown approach. It was observed that the layered approach identified more critical, relatively shallow failure surfaces and eliminated the spurious apparently critical deep-seated rock mass failure surfaces, generated assuming a uniform rock mass

Asset Management for Retaining Walls

The work described here represents an attempt to develop a comprehensive risk management framework for the asset management of retaining wall structures. The work presented includes the development of a sensing strategy that can be used by structural inspectors to assess the coupled performance of the wall structure and the geotechnical system it supports. A reliability framework was developed using first-order reliability methods (FORM) to assess the reliability factor (β) for wall components and incorporates the consequences of failure with the estimated structural reliability factors to provide a basis for risk assessment of retaining walls. A new inspection manual was developed to reflect the instrumentation strategies and risk analyses developed

Waste-composition-dependent HBM model parameters based on degradation experiments

Municipal solid waste (MSW) is biodegradable in landfills under anaerobic conditions. The evolution of the hydro-biochemical-mechanical (HBM) processes during degradation is investigated first through experiments and subsequently via modelling. Three well-characterized MSW specimens with significantly different waste composition ranging from "waste-rich" to "soil-rich" were degraded in large-scale experimental setups that enabled simultaneous characterization of the processes with time. The closely-monitored processes are subsequently modelled using a two-stage anaerobic degradation model which is incorporated in the HBM model. This allows an assessment of model performance as a function of waste composition and derivation of waste composition-dependent model parameters. The model performed fairly well in capturing the biochemical and physical behaviour. An increase in biodegradable material in waste specimen corresponds to increase in anaerobic activity (volatile fatty acids and methanogenic biomass accumulation), higher rate of organic fraction depletion, increase in settlement and increase in methane production. However, the model is found to significantly over-predict methane production for all the specimens