Author: Publisher: ISBN: Category : Languages : en Pages :
Book Description
Liquefaction-induced ground failure continues to be a major component of earthquake-related damages in many parts of the world. Experience from past earthquakes indicates lateral spreads and flow slides have been widespread in saturated granular soils in coastal and river areas. Movements may exceed several meters even in very gentle slopes. More interestingly, failures have occurred not only during, but also after earthquake shaking. The mechanism involved in large lateral displacements is still poorly understood. Sand deposits often comprise of low permeability sub-layers e.g., silt seams. Such layers form a hydraulic barrier to upward flow of water associated with earthquake-induced pore pressures. This impedance of flow path results in an increase of soil skeleton volume (or void ratio) beneath the barrier. The void redistribution mechanism as the focus of this study explains why residual strengths from failed case histories are generally much lower than that of laboratory data based on undrained condition. A numerical stress-flow coupled procedure based on an effective stress approach has been utilized to investigate void redistribution effects on the seismic behavior of gentle sandy slopes. This study showed that an expansion zone develops at the base of barrier layers in stratified deposits subjected to cyclic loading that can greatly reduce shear strength and results in large deformations. This mechanism can lead to a steady state condition within a thin zone beneath the barrier causing flow slide when a threshold expansion occurs in that zone. It was found that contraction and expansion, respectively at lower parts and upper parts of a liquefiable slope with a barrier layer is a characteristic feature of seismic behavior of such deposits. A key factor is the pattern of deformations localized at the barrier base, and magnitude that takes place with some delay. In this thesis, a framework for understanding the mechanism of large deformations, and a practical.
Author: National Academies of Sciences, Engineering, and Medicine Publisher: ISBN: 9780309440271 Category : Languages : en Pages : 350
Book Description
Earthquake-induced soil liquefaction (liquefaction) is a leading cause of earthquake damage worldwide. Liquefaction is often described in the literature as the phenomena of seismic generation of excess porewater pressures and consequent softening of granular soils. Many regions in the United States have been witness to liquefaction and its consequences, not just those in the west that people associate with earthquake hazards. Past damage and destruction caused by liquefaction underline the importance of accurate assessments of where liquefaction is likely and of what the consequences of liquefaction may be. Such assessments are needed to protect life and safety and to mitigate economic, environmental, and societal impacts of liquefaction in a cost-effective manner. Assessment methods exist, but methods to assess the potential for liquefaction triggering are more mature than are those to predict liquefaction consequences, and the earthquake engineering community wrestles with the differences among the various assessment methods for both liquefaction triggering and consequences. State of the Art and Practice in the Assessment of Earthquake-Induced Soil Liquefaction and Its Consequences evaluates these various methods, focusing on those developed within the past 20 years, and recommends strategies to minimize uncertainties in the short term and to develop improved methods to assess liquefaction and its consequences in the long term. This report represents a first attempt within the geotechnical earthquake engineering community to consider, in such a manner, the various methods to assess liquefaction consequences.
Author: Rolando P. Orense Publisher: CRC Press ISBN: 1138026433 Category : Technology & Engineering Languages : en Pages : 282
Book Description
Soil Liquefaction during Recent Large-Scale Earthquakes contains selected papers presented at the New Zealand – Japan Workshop on Soil Liquefaction during Recent Large-Scale Earthquakes (Auckland, New Zealand, 2-3 December 2013). The 2010-2011 Canterbury earthquakes in New Zealand and the 2011 off the Pacific Coast of Tohoku Earthquake in Japan have caused significant damage to many residential houses due to varying degrees of soil liquefaction over a very wide extent of urban areas unseen in past destructive earthquakes. While soil liquefaction occurred in naturally-sedimented soil formations in Christchurch, most of the areas which liquefied in Tokyo Bay area were reclaimed soil and artificial fill deposits, thus providing researchers with a wide range of soil deposits to characterize soil and site response to large-scale earthquake shaking. Although these earthquakes in New Zealand and Japan caused extensive damage to life and property, they also serve as an opportunity to understand better the response of soil and building foundations to such large-scale earthquake shaking. With the wealth of information obtained in the aftermath of both earthquakes, information-sharing and knowledge-exchange are vital in arriving at liquefaction-proof urban areas in both countries. Data regarding the observed damage to residential houses as well as the lessons learnt are essential for the rebuilding efforts in the coming years and in mitigating buildings located in regions with high liquefaction potential. As part of the MBIE-JSPS collaborative research programme, the Geomechanics Group of the University of Auckland and the Geotechnical Engineering Laboratory of the University of Tokyo co-hosted the workshop to bring together researchers to review the findings and observations from recent large-scale earthquakes related to soil liquefaction and discuss possible measures to mitigate future damage. Soil Liquefaction during Recent Large-Scale Earthquakes will be of great interest to researchers, academics, industry practitioners and other professionals involved in Earthquake Geotechnical Engineering, Foundation Engineering, Earthquake Engineering and Structural Dynamics.
Author: Jack Montgomery Publisher: ISBN: 9781339260419 Category : Languages : en Pages :
Book Description
An examination of several potential sources of variability in nonlinear deformation analyses (NDAs) is presented. NDAs are becoming increasingly common for evaluating the effects of liquefaction on structures, such as embankment dams. Results from NDAs may be used to develop fragility curves for risk analyses, gain insights into deformation patterns and design and evaluate remediation alternatives. The use of NDA results in practice requires confidence in both the validity and repeatability of the analyses. This dissertation presents an evaluation of several potential sources of variability associated with NDAs of liquefaction effects on embankment dams. These sources of variability include the effects of overburden stresses on liquefaction, undrained strengths of compacted soils, effects of spatial variability on deformations, and numerical modeling of void redistribution. These topics were identified in part through discussion with engineers at the California Division of Safety of Dams which has funded this study. The goal of this dissertation is to evaluate and provide guidance on the above issues with the goal of reducing unnecessary variability in NDA results in practice. This work was also part of a parallel study which validates a set of NDA procedures against the observed performances of the Lower and Upper San Fernando Dams in the 1971 San Fernando earthquake and which will be published as a report from the Center for Geotechnical Modeling by Montgomery and Boulanger. First, an updated database of laboratory test results used to define the overburden correction factor (K[subscript][sigma]) is presented. This factor is used to account for the curvature of the cyclic strength envelope with increasing consolidation stress and provides part of the basis for extrapolation of liquefaction triggering correlations to large depths and stresses, such as those encountered under large embankment dams. Laboratory test results included in previous databases are reexamined in light of current understanding of factors which can affect laboratory measurements of cyclic strengths. The updated database is used to examine potential biases in the K[subscript][sigma] relationships used in two SPT-based liquefaction triggering procedures. The first relationship was found to be conservative with respect to the data for clean sands, and to be less conservative for sands with fines contents between 7% and 35%. The second relationship was found to provide a reasonably good fit to the data for clean sands, and to be slightly unconservative for sands with fines contents between 7% and 35%. Implications for practice are discussed. A recommended procedure for determining the static undrained shear strength parameters of compacted soils within an embankment dam is presented for use in Mohr-Coulomb constitutive models. The interpretation of ICU triaxial compression tests and a current method for estimating the effects of anisotropic consolidation in limit equilibrium analysis are reviewed. A method for interpolating ACU shear strengths in an NDA based on four different measures of consolidation stress is described and illustrated using a numerical example. The effects of spatial variability in soil properties on the liquefaction-induced deformations of gently sloping ground and the foundation of an embankment dam are presented. NDA results for models having uniform properties are compared to results for models having spatially correlated Gaussian random field property distributions. Results are presented for sets of non-uniform model realizations and a set of ground motions scaled to a range of peak ground accelerations. Computed deformations for these uniform and stochastic models are used to identify representative properties (as a percentile of the stochastic distributions) for which the uniform models produce reasonable agreement with the median of the stochastic model responses. The results show that the representative (N1)60[subscript]cs value can range from the 30th to the 70th percentile depending on the mean (N1)60[subscript]cs value, consolidation stresses, initial static shear stress ratio, shaking level, input ground motion, and other factors. The use of 33rd percentile values would appear reasonably conservative for deterministic evaluations, whereas the full range may be more appropriate for use in risk evaluations if such a refinement appears warranted. Finally, results are presented from numerical simulations to examine how geologic characteristics of stratigraphic interfaces may affect the mechanism of strength loss due to void redistribution. The void redistribution mechanism is briefly reviewed, followed by a discussion of how various characteristics of the stratigraphy may play a significant role. Numerical simulations of a layered infinite slope are then used to examine how undulations in the interface between liquefiable layers and overlying low permeability layers may affect the potential for strength loss due to void redistribution. Results show the loss of strength associated with void redistribution is greatest for near-planar interfaces between liquefying sands and low permeability strata and decreases significantly as the interface becomes more irregular. Challenges encountered during these analyses and potential implications of these findings for engineering practice are discussed.
Author: Kyriazis D. Pitilakis Publisher: Springer Science & Business Media ISBN: 1402058926 Category : Technology & Engineering Languages : en Pages : 497
Book Description
This book contains the full papers on which the invited lectures of the 4th International Conference on Geotechnical Earthquake Engineering (4ICEGE) were based. The conference was held in Thessaloniki, Greece, from 25 to 28 June, 2007. The papers offer a comprehensive overview of the progress achieved in soil dynamics and geotechnical earthquake engineering, examine ongoing and unresolved issues, and discuss ideas for the future.
Author: The Organizing Committee of the 16th ICSMGE Publisher: IOS Press ISBN: 1614996563 Category : Technology & Engineering Languages : en Pages : 3742
Book Description
The 16th ICSMGE responds to the needs of the engineering and construction community, promoting dialog and exchange between academia and practice in various aspects of soil mechanics and geotechnical engineering. This is reflected in the central theme of the conference 'Geotechnology in Harmony with the Global Environment'. The proceedings of the conference are of great interest for geo-engineers and researchers in soil mechanics and geotechnical engineering. Volume 1 contains 5 plenary session lectures, the Terzaghi Oration, Heritage Lecture, and 3 papers presented in the major project session. Volumes 2, 3, and 4 contain papers with the following topics: Soil mechanics in general; Infrastructure and mobility; Environmental issues of geotechnical engineering; Enhancing natural disaster reduction systems; Professional practice and education. Volume 5 contains the report of practitioner/academic forum, 20 general reports, a summary of the sessions and workshops held during the conference.
Author: Michael Jefferies Publisher: CRC Press ISBN: 020330196X Category : Science Languages : en Pages : 625
Book Description
Soil liquefaction is a major concern in areas of the world subject to seismic activity or other repeated vibration loads. This book brings together a large body of information on the topic, and presents it within a unified and simple framework. The result is a book which will provide the practising civil engineer with a very sound understanding of
Author: PoulV. Lade Publisher: Routledge ISBN: 1351424475 Category : Technology & Engineering Languages : en Pages : 385
Book Description
The workshop aims to provide a fundamental understanding of the liquefaction process, necessary to the enhancement of liquefaction prediction. The contributions are divided into eight sections, which include: factors affecting liquefaction susceptibility and field studies of liquefaction.
Author: 
Author: National Academies of Sciences, Engineering, and Medicine
Author: Rolando P. Orense
Author: Jack Montgomery
Author: R K Anu
Author: Berna Sunman
Author: Kyriazis D. Pitilakis
Author: The Organizing Committee of the 16th ICSMGE
Author: Michael Jefferies
Author: PoulV. Lade