Selection of Method for Seismic Slope Stability Analysis

The seismic stability of natural slopes in clayey materials is a subject about which much uncertainty still exists. Therefore, selection of the method for the seismic slope stability analysis is an important part of solving the problem. In this paper the basic elements of the pseudo-static method, the sliding block method and the Ishihara\u27s method are discussed. A case history of seismic stability analysis of an Adriatic coast flysch slope has been employed to evaluate the applicability and reliability of these methods. The slope is treated as an infinite slope. Although no definitive conclusions can be drawn from a single case history study, results may be used m future evaluations of seismic stability of similar slopes in cohesive materials

Recent Advances in Seismic Design of Geosynthetically-Lined Waste Containment Facilities

Geosynthetic materials are essential elements of almost all modern landfill barrier systems. Materials such as geomembranes and geosynthetic clay liners are widely used as resistive barrier elements while geotextiles, drainage nets, and geocomposites are widely employed in modern composite barrier systems for both landfill liners and covers. The ability of these geosynthetic elements to maintain their integrity when subject to deformations due to waste settlement and seismic loading is a major uncertainty with respect to the performance of modern landfills. Over past years, advances have been made in understanding of material behavior under cyclic loading, modeling of modern landfill response to strong ground shaking, and interpretation of the analysis results. This paper presents, by reference, results of relevant recent research including advances in evaluation of dynamic material properties of municipal solid waste (MSW) and special wastes, dynamic testing of barrier system interfaces, understanding of decoupled and fully coupled response analysis, and advances in constitutive and numerical modeling relevant to better modeling of seismic response of modern landfills. Based upon the synthesis of this information, it is concluded that the commonly used decoupled approach is reasonably conservative and can be used for seismic design of modern waste containment facilities until fully coupled approach and associated evaluation and modeling of interface parameters evolve to be usable from both the practical and economic points of view

Seismic Design of Mixed and Hazardous Waste Landfills

Due to the absence of federal criteria, seismic design and performance criteria for mixed and hazardous waste landfills are generally developed on a project-specific basis, supplemented by state and project-specific standards. In developing project-specific criteria, the federal Subtitle D standards for seismic design of municipal solid waste landfills are often used as a minimum standard for mixed and hazardous waste facilities. Seismic performance standards are also usually developed on a project-specific basis, employing either a “withstand without harmful discharge” or a “withstand without damage” performance standard, depending on the certainty of continuing aftercare. Quantitative criteria established to demonstrate compliance with these performance standards should consider the inherent conservatism in the type of analysis employed to evaluate the selected performance measure. Material properties for seismic design of mixed or hazardous waste landfills are also usually developed on a project-specific basis. Material property values are often subject to considerable uncertainties about waste composition, variability in the waste composition, and waste heterogeneity. Parametric and sensitivity studies are generally used to compensate for the uncertainty in waste properties and the variability and heterogeneity of the waste. Four case histories are presented to illustrate these issues

The Role of Geotechnical Factors in Northridge Earthquake Residential Damage

On three projects, one a class action law suit and two involving readjustment of insurance claims, we evaluated the impact of the 1994 Mw 6.7 Northridge, California earthquake on over 1,600 residential properties. For each of the properties, we reviewed previous reports on the condition of the site immediately after the earthquake, undertook a site visit to observe current conditions, undertook site-specific geotechnical investigations, as appropriate, and documented our findings on the impact of long-term and earthquakerelated geotechnical factors on property damage. We have identified the following significant geotechnical factors that contribute to residential earthquake damage: (a) hillside sites; (b) cut/fill transitions; (c) expansive soils; (d) liquefied sandy soils; and (e) deep soft soils. This paper summarizes and presents our findings regarding these factors for five representative case histories of residential damage in the Northridge earthquake

Performance of Two Geosynthetics-Lined Landfills in the Northridge Earthquake

Analyses of the performance of the Chiquita Canyon and Lopez Canyon landfills in the 1994 Magnitude 6.7 Northridge earthquake illustrate deficiencies in the current state-of-practice for seismic design of geosynthetic liner systems and the promise of a new state-of-the-art method for performance-based design, and suggest necessary modifications to construction quality assurance procedures for geosynthetic liner systems. Analyses of the Chiquita Canyon landfill case history using the conventional state-of-practice Newmark Analysis approach fail to predict the tears observed at the landfill following the earthquake in the side slope liner geomembrane at two different locations. However, the state-of-the-art finite difference based method does predict failure of the geomembrane at these locations if strain concentrations due to seams and scratches in the geomembrane from patches at locations where destructive samples were recovered for construction quality assurance purposes are considered. The state-of-the-art method also predicts tension strains observed in the filter geotextile for the side slope liner at the Lopez Canyon landfill following the earthquake. The analysis for the Chiquita Canyon landfill suggests that construction quality assurance guidelines for obtaining geomembrane samples for destructive testing should be developed for avoiding critical areas where geomembrane tensile strain is likely to accumulate

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

Site Characterization, Design, and Construction for Closure of Four Hazardous Waste Landfills at a Superfund Site

Various elements related to extensive geotechnical and seismic site characterization, design, and construction for the closure of four hazardous waste landfills and their interstitial areas at a major federal Superfund site are discussed. A major challenge was the geotechnical characterization of bulk and containerized hazardous waste for the purpose of stability analyses. Design constraints included a highly seismic environment and a large design precipitation event. Design was completed in two separate phases, such that the closure design of three of the landfills was performed during and after the construction of the first. This allowed for lessons learned from the construction phase of the first landfill closure to be incorporated into the design of the final three

Nonlinear Time-Domain Analysis of a Sliding Block on a Plane

A time domain finite difference numerical model of a sliding rigid block on a plane is developed using a simple elastic-perfectly plas-tic Mohr-Coulomb interface model. The model is shown to accurately predict the slip-stick and slip-slip behavior deduced from an analytical solution for behavior of a sliding block on a horizontal plane and the results of physical model tests of a block on both hori-zontal and inclined planes subject to harmonic and non-uniform excitation provided the appropriate interface strength is employed. Back analyses of the physical model tests show that for some geosynthetic interfaces, the interface shear strength depends upon the velocity of sliding. The numerical model developed herein provides a basis for rigorous evaluation of several important problems in geotechnical earthquake engineering, including the cumulative permanent seismic deformation of landfills, embankments, slopes, and retaining walls and the stresses induced by seismic loading in geosynthetic elements of landfill liner and cover systems

Solid Waste Landfill Performance During the 1994 Northridge Earthquake

The performance of 22landfills in the Los Angeles area during the January 17, 1994 Northridge earthquake has been investigated. Observations of damage at these landfills indicate that the overall performance of solid waste landfills was encouraging. None of the surveyed landfills showed any signs of major damage. However, one geosynthetic-lined landfill experienced two tears in the geomembrane liner. Most landfills within 30 km of the zone of energy release experienced some form of cracking in the soil cover. Beyond approximately 40 km from the zone of energy release, little to no damage was observed