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Author: Mauro Giuliano Sottile Publisher: ISBN: Category : Languages : en Pages : 136
Book Description
Reliable modeling of rate-dependency in soil properties remains a major challenge for accurate solutions of many geotechnical problems. Although there are many sources of experimental data concerning rate dependent properties of clays, most pre-existing soil models have been found to have severe predictive limitations. Yuan (2016) developed a new elasto-viscoplastic model, MIT-SR, for rate-dependent behavior of clays. The model unifies the existing elasto-plastic framework from prior MIT soil models (3-D surface system and generalized hysteretic formulation) with a physically-based evolution law that attributes the macroscopic viscoplastic strain to an internal strain rate related to the prior strain rate history. MIT-SR has the capability of describing a wide range of observed time-effects within a unified framework and resolves the long-stranding dilemma regarding creep effects at field scale (i.e., Hypothesis A vs B). This thesis implements MIT-SR model to evaluate strain rate effects on two longstanding geotechnical problems: insitu soil characterization from pressuremeter tests and long-term performance of embankments on soft clays. The first part of this research presents a review of the constitutive model framework and discuss the implementation and validation in non-linear finite element analyses using a User Defined Material (UMAT) in the ABAQUSTM program. Part two consists of the investigation of how disturbances (modeled using Strain Path framework; Baligh, 1985) and strain rate effects (modeled by MIT-SR) affect the results of the Full Displacement or cone-pressuremeter (FDPM) and self-boring pressuremeters (SBPM) for Resedimented Boston Blue Clay (RBBC). The results show that that disturbances of the stress field play a vital role in the interpretation undrained shear strength. For the FDPM case, using the same expansion rate, the disturbed NC RBBC can have as low as 40% of the undrained shear strength of the undisturbed NC RBBC. In contrast, for the SBPM case, the disturbed NC RBBC tend to have a slightly higher undrained shear strength (approximately 10%) than the undisturbed NC RBBC. The third part consists of a re-analysis of a well-instrumented test embankment built on a 40m deep layer of Boston Blue Clay. Finite element analyses of embankment performance are conducted using coupled consolidation with the MIT-SR effective stress model. The results were compared with previous numerical results using MIT-E3 presented by Ladd et al. (1994). Overall, MIT-SR contributes a significant improvement in predictions of settlements, but does not significantly improve predictions of lateral spreading. The overall results suggest that the dependent creep properties play only a secondary role in the performance of this particular test embankment.
Author: Mauro Giuliano Sottile Publisher: ISBN: Category : Languages : en Pages : 136
Book Description
Reliable modeling of rate-dependency in soil properties remains a major challenge for accurate solutions of many geotechnical problems. Although there are many sources of experimental data concerning rate dependent properties of clays, most pre-existing soil models have been found to have severe predictive limitations. Yuan (2016) developed a new elasto-viscoplastic model, MIT-SR, for rate-dependent behavior of clays. The model unifies the existing elasto-plastic framework from prior MIT soil models (3-D surface system and generalized hysteretic formulation) with a physically-based evolution law that attributes the macroscopic viscoplastic strain to an internal strain rate related to the prior strain rate history. MIT-SR has the capability of describing a wide range of observed time-effects within a unified framework and resolves the long-stranding dilemma regarding creep effects at field scale (i.e., Hypothesis A vs B). This thesis implements MIT-SR model to evaluate strain rate effects on two longstanding geotechnical problems: insitu soil characterization from pressuremeter tests and long-term performance of embankments on soft clays. The first part of this research presents a review of the constitutive model framework and discuss the implementation and validation in non-linear finite element analyses using a User Defined Material (UMAT) in the ABAQUSTM program. Part two consists of the investigation of how disturbances (modeled using Strain Path framework; Baligh, 1985) and strain rate effects (modeled by MIT-SR) affect the results of the Full Displacement or cone-pressuremeter (FDPM) and self-boring pressuremeters (SBPM) for Resedimented Boston Blue Clay (RBBC). The results show that that disturbances of the stress field play a vital role in the interpretation undrained shear strength. For the FDPM case, using the same expansion rate, the disturbed NC RBBC can have as low as 40% of the undrained shear strength of the undisturbed NC RBBC. In contrast, for the SBPM case, the disturbed NC RBBC tend to have a slightly higher undrained shear strength (approximately 10%) than the undisturbed NC RBBC. The third part consists of a re-analysis of a well-instrumented test embankment built on a 40m deep layer of Boston Blue Clay. Finite element analyses of embankment performance are conducted using coupled consolidation with the MIT-SR effective stress model. The results were compared with previous numerical results using MIT-E3 presented by Ladd et al. (1994). Overall, MIT-SR contributes a significant improvement in predictions of settlements, but does not significantly improve predictions of lateral spreading. The overall results suggest that the dependent creep properties play only a secondary role in the performance of this particular test embankment.
Author: Gonzalo Rellán Publisher: ISBN: Category : Languages : en Pages : 233
Book Description
Saturated clays exhibit rate-dependent behavior (i.e. their stress-strain-strength properties are significantly affected by the applied loading rate). This is of great significance for geotechnical projects, particularly when long-term predictions of settlements of compressible soil strata are based on results of laboratory element tests on small test specimens. Ladd et al. (1977) show that scaling of laboratory consolidation tests to field scale is strongly affected by assumed creep properties of the clay, leading to competing hypotheses of field performance (Hypotheses A and B). Most pre-existing soil models are based on isochrone theory which assumes a unique relationship between effective stress-strain and strain rate - such that the scaling of creep and consolidation conforms to Hypothesis B. Recently Yuan (2016) has developed a novel elasto-viscoplastic effective stress model, MIT-SR, that is capable of accurately predicting a wide range of rate-dependent characteristics of clay. The proposed formulation is able to represent both scaling hypotheses of coupled creep and consolidation. This thesis analyzed the predictive capabilities of MIT-SR model by studying two projects: New Hamilton Partnership Levee Project (NHPL) and Marina Bay land reclamation projects, Singapore. MIT-SR materials were calibrated with laboratory and field tests only and numerical simulations of the projects were performed with the Finite Element Method (FEM). The NHPL project consisted on an 11 ft high embankment, constructed in 1996 in California, on +30ft of highly compressive San Francisco Bay Mud (SFBM). Our re-analyses included the MIT-SR calibration for SFBM and 2D FEM simulations that compare MIT-SR, Soft Soil Model and Soft Soil Creep Model predictions. The results show that MIT-SR offers superior predictions of the lateral spreading and settlement during both the construction and post-construction phases. The Marina Bay area in Singapore was reclaimed by surcharged underlying marine clays with more than 13m of granular fill between 1979 and 1985. Construction of the new Thomson Line subway through the area has measured on-going free-field settlements from the reclamation during the period 2015-208. We analyze these long-term settlements by calibrating MIT-SR parameters for Singapore marine clay and performing a series of 1 D consolidation analyses to represent variations in the soil profile across the area. The model predicts settlement rates that vary with the thickness of marine clay, principally ranging from 10 to 20mm/yr at present time. The model tends to underestimate the measured settlement rates. This may reflect underestimation of creep properties of the clays or thickness of the fill. The results from MIT-SR simulations in both projects were very encouraging and confirmed the strong predictive capabilities of the model with calibration procedures based on laboratory and site tests only. MIT-SR was able to accurately predict deformations and pore pressures in undrained, consolidation and creep stages with a unique set of parameters calibrated.
Author: David M Potts Publisher: Thomas Telford ISBN: 9780727727831 Category : Mathematics Languages : en Pages : 456
Book Description
An insight into the use of the finite method in geotechnical engineering. The first volume covers the theory and the second volume covers the applications of the subject. The work examines popular constitutive models, numerical techniques and case studies.
Author: Peter Wroth Publisher: Thomas Telford ISBN: 9780727719164 Category : Technology & Engineering Languages : en Pages : 854
Book Description
This volume contains the 49 papers which form the proceedings of the Wroth Memorial Symposium. The themes of the symposium were soil properties and their measurement, especially means of in-situ tests, prediction and performance, and design methods.
Author: Marco Dorigo Publisher: MIT Press ISBN: 9780262042192 Category : Computers Languages : en Pages : 324
Book Description
An overview of the rapidly growing field of ant colony optimization that describes theoretical findings, the major algorithms, and current applications. The complex social behaviors of ants have been much studied by science, and computer scientists are now finding that these behavior patterns can provide models for solving difficult combinatorial optimization problems. The attempt to develop algorithms inspired by one aspect of ant behavior, the ability to find what computer scientists would call shortest paths, has become the field of ant colony optimization (ACO), the most successful and widely recognized algorithmic technique based on ant behavior. This book presents an overview of this rapidly growing field, from its theoretical inception to practical applications, including descriptions of many available ACO algorithms and their uses. The book first describes the translation of observed ant behavior into working optimization algorithms. The ant colony metaheuristic is then introduced and viewed in the general context of combinatorial optimization. This is followed by a detailed description and guide to all major ACO algorithms and a report on current theoretical findings. The book surveys ACO applications now in use, including routing, assignment, scheduling, subset, machine learning, and bioinformatics problems. AntNet, an ACO algorithm designed for the network routing problem, is described in detail. The authors conclude by summarizing the progress in the field and outlining future research directions. Each chapter ends with bibliographic material, bullet points setting out important ideas covered in the chapter, and exercises. Ant Colony Optimization will be of interest to academic and industry researchers, graduate students, and practitioners who wish to learn how to implement ACO algorithms.
Author: National Research Council (U.S.). Transportation Research Board Publisher: ISBN: Category : Science Languages : en Pages : 254
Book Description
This volume brings together, from a wide range of experience, such information as may be useful in recognizing, avoiding, controlling, designing for, and correcting movement. Current geologic concepts and engineering principles and techniques are introduced, and both the analysis and control of soil and rock-slopes are addressed. New methods of stability analysis and the use of computer techniques in implementing these methods are included. Rock slope engineering and the selecting of shear-strength parameters for slope-stability analyses are covered in separate chapters.
Author: Franz Roters Publisher: John Wiley & Sons ISBN: 3527642099 Category : Technology & Engineering Languages : en Pages : 188
Book Description
Written by the leading experts in computational materials science, this handy reference concisely reviews the most important aspects of plasticity modeling: constitutive laws, phase transformations, texture methods, continuum approaches and damage mechanisms. As a result, it provides the knowledge needed to avoid failures in critical systems udner mechanical load. With its various application examples to micro- and macrostructure mechanics, this is an invaluable resource for mechanical engineers as well as for researchers wanting to improve on this method and extend its outreach.
Author: Reginald Hammah Publisher: CRC Press ISBN: 1000521052 Category : Technology & Engineering Languages : en Pages : 690
Book Description
This publication includes 82 technical papers presented at Rocscience International Conference (RIC) 2021, held online on April 20 and 21, 2021. Rocscience created this event to bring geotechnical academics, researchers and practitioners together to exchange ideas as part of celebrating 25 years of the company’s existence. The papers in these proceedings were from keynotes, panel discussions and papers, selected after careful review of over 100 technical submissions delivered at RIC 2021. The technical papers were grouped into sessions based on their subject areas. The conference aimed to stimulate discussions that could help the industry work towards overcoming geotechnical engineering limitations today. It also sought to foster creative thinking that will advance the current states of the art and practice. The keynote addresses, panel discussions and technical presentations tried to examine geotechnical problems and situations from fresh perspectives. RIC 2021 hopes that the proceedings will continue to enrich our thinking and contribute to achieving a critical mass of change in our practices and approaches. We look forward to significant improvements in our industry.
Author: National Intelligence Council Publisher: Cosimo Reports ISBN: 9781646794973 Category : Languages : en Pages : 158
Book Description
"The ongoing COVID-19 pandemic marks the most significant, singular global disruption since World War II, with health, economic, political, and security implications that will ripple for years to come." -Global Trends 2040 (2021) Global Trends 2040-A More Contested World (2021), released by the US National Intelligence Council, is the latest report in its series of reports starting in 1997 about megatrends and the world's future. This report, strongly influenced by the COVID-19 pandemic, paints a bleak picture of the future and describes a contested, fragmented and turbulent world. It specifically discusses the four main trends that will shape tomorrow's world: - Demographics-by 2040, 1.4 billion people will be added mostly in Africa and South Asia. - Economics-increased government debt and concentrated economic power will escalate problems for the poor and middleclass. - Climate-a hotter world will increase water, food, and health insecurity. - Technology-the emergence of new technologies could both solve and cause problems for human life. Students of trends, policymakers, entrepreneurs, academics, journalists and anyone eager for a glimpse into the next decades, will find this report, with colored graphs, essential reading.
Author: Mauro Giuliano Sottile
Author: Mauro Giuliano Sottile
Author: Gonzalo Rellán
Author: David M Potts
Author: Peter Wroth
Author: 
Author: Marco Dorigo
Author: National Research Council (U.S.). Transportation Research Board
Author: Franz Roters
Author: Reginald Hammah
Author: National Intelligence Council