Theoretical methods for estimating the dynamic response and predicting the performance of modern ... more Theoretical methods for estimating the dynamic response and predicting the performance of modern rockfill dams subjected to strong earthquake shaking are reviewed. The focus is on methods accounting for nonlinear material behavior, for 3-dimensional canyon geometry, and asynchronous base excitation. It is shown that both strong nonlinearities and lack of coherence in the seismic excitation tend to reduce the magnitude of the deleterious 'whip-lash' effect computed for tall dams built in rigid narrow canyons. Particular emphasis is accorded to Concrete-Faced-Rockfill dams and a case study involving an actually designed dam in a narrow canyon points to potential problems and suggests desirable modifications. In the light of theoretical results, the paper concludes with a discussion on design rules and defensive measures that would lead to robust design schemes of Earth-Core and Concrete-Faced Rockfill dams. Field verification through records of seismic response is, however, a prerequisite for the confident adoption of such measures in practice.
The Twenty-second International Offshore and Polar Engineering Conference, 2012
The paper examines the behaviour of buried steel pipelines crossing active strike-slip faults. Th... more The paper examines the behaviour of buried steel pipelines crossing active strike-slip faults. The vertical fault plane is crossed by the pipeline at an angle ranging between zero and 45 degrees, causing significant plastic deformation in the pipeline. The investigation is numerical, simulating the nonlinear response of the soil-pipeline system rigorously through nonlinear finite elements, accounting for inelastic material behaviour of the pipeline and the pipe and the soil, as well as contact and friction on the soil-pipe interface. Steel pipes with D/t ratio and material grade typical for hydrocarbon pipelines are analyzed, through an incremental application of fault displacement and appropriate pipeline performance criteria, defined within a strain-based design framework, are monitored throughout the analysis. The effects of various soil and linepipe parameters on the structural response of the pipeline are examined. The numerical results from the present investigation determine the fault displacement at which the specified performance criteria are reached, including the effects of internal pressure.
A new approach for liquefaction flow failure evaluation of earth dams is presented. The method ap... more A new approach for liquefaction flow failure evaluation of earth dams is presented. The method applies steady-state concepts, and is based on the premise that flow failure of an earth dam takes place in two consecutive stages: a first stage of pore pressure buildup, controlled by the horizontal seismic shear strains, and a second stage of unidirectional steady-state flow failure, driven by the static shear stresses, associated with the weight of the sliding mass. A simplified method of determining seismic shear strains is also presented. For the covering abstract of the conference see IRRD 287689. (Author/TRRL)
Results from simplified analytical and numerical models on vibrational characteristics of earth d... more Results from simplified analytical and numerical models on vibrational characteristics of earth dams in narrow canyons are presented. The effect of the canyon length over height ratio on the fundamental period of the dam is illustrated for five idealized canyons shapes: increasing canyon narrowness results in a decrease of the natural period. In contrast, a deformable underlying soil layer in the middle of the valley is shown to lengthen the natural period. Useful closed-form expressions for natural frequencies, displacement shapes, participation factors, and acceleration amplification functions are presented in a table. Acceleration amplification functions at midcrest are plotted versus a dimensionless frequency for various canyon shapes. A simple model of a dam in a semicylindrical canyon is used to demonstrate that flexible canyon boundaries may significantly reduce mid-crest accelerations due to energy radiation. Moreover, soil nonlinearities that develop during strong base motion may reduce drastical...
Journal of Pipeline Systems Engineering and Practice, Feb 1, 2021
AbstractPipelines transporting oil and natural gas may experience upheaval buckling due to substa... more AbstractPipelines transporting oil and natural gas may experience upheaval buckling due to substantial compressive forces induced by high temperature and pressure of the fluid content. Such upheava...
This General Report is presented in the following four sections. In the first section a brief sta... more This General Report is presented in the following four sections. In the first section a brief state-of-the art review is given related to the following topics (covered by the papers presented in this session): (i) analysis of embankment stability during earthquakes; (ii) liquefaction potential of saturated soils during earthquakes; (iii) behaviour of tailings dams and waste disposals during seismic events; and (iv) assessment of failure of natural slopes during earthquakes. In the second section a summary of each paper is presented followed by general comments. The third section presents some future trends and the final section presents some remarks and topics for discussion.
Following the January 1994 Northridge Earthquake in Southern California, the authors traveled to ... more Following the January 1994 Northridge Earthquake in Southern California, the authors traveled to Los Angeles and surveyed the earthquake damage region. Subsequently, seismologic, geologic and ground motion data were compiled and evaluated. This paper presents our observations and evaluation of: geologic and soil effects; soil-structure interaction; liquefaction; slope failures and rock slides; and ground deformations.
A mathematical solution is presented for steady-state lateral response of earth and rock fill dam... more A mathematical solution is presented for steady-state lateral response of earth and rock fill dams in canyons subjected to asynchronous excitation consisting of obliquely incident SH waves. The dam is idealized with a 2-dimensional shear wedge and the canyon is considered rectangular and consisting of flexible rock. A parametric study is undertaken to investigate the influence of (a) the angle of incidence, (b) the impedance ratio and (c) the canyon narrowness on the steady-state response, by considering in a simplifying way the effects of the dam-canyon interaction. The results demonstrate that the above factors may have a significant effect on the lateral response of the dam. For relatively flexible canyon rock, the effect of radiation damping is very important and, consequently, the assumption of rigid base may be very unrealistic. Due to interference phenomena, the response is not maximum for vertically propagating waves, but for waves incident at a certain angle. For obliquely incident waves travelling from left to the right, a gradual shift of the location of the peak response is observed from the mid-crest to the right side of the dam as the angle of incidence increases. Also, for very long dams subjected to high frequency obliquely incident waves, there is no amplification of the motion by the dam and, at a certain frequency of excitation, the presence of standing waves is indicated.
SYNOPSIS A study of the effects of dam-foundation interaction on the response of earth dams to ob... more SYNOPSIS A study of the effects of dam-foundation interaction on the response of earth dams to obliquely incident P and SV waves is presented. The numerical formulation combines the Finite Element Method and the Boundary Equation Method in a powerful hybrid technique. The FEM has been proven very efficient for finite size elastodynamics problems, but several previously suggested modifications for handling infinite domain dynamic problems seem to be either computationally expensive or have serious limitations on the geometry and excitation. The BEMis employed to solve the halfspace problem using exact Green's functions to compute the halfspace stiffness, which is then incorporated in the FEM solution. This technique proved to be exceptionally powerful as it leads to accurate and very efficient solutions. A preliminary study is undertaken to investigate the response of dams subjected to obliquely incident P and SV waves, propagating across the dam width. The results of the present rigorous study extend the conclusions from earlier studies on the effects of the dam-foundation interaction and the special variability of the ground motion. Moreover, the proposed model provides an efficient tool for dynamic analysis of earth dams and is part of a broader study of 2D and 3D dams using the hybrid formulation in both the frequency and time domains, with final objective the incorporation, in the latter case, of soil nonlinearity.
We have investigated in detail the properties of a model comet nucleus composed of'an icydust soi... more We have investigated in detail the properties of a model comet nucleus composed of'an icydust soil. The thermal properties are predicted and related to the observable phenomena seen in the many comet comae and the fly-bye images of Comet Halley. A thorough review of the literature on this subject was made and reported upon in this document.
Theoretical methods for estimating the dynamic response and predicting the performance of modern ... more Theoretical methods for estimating the dynamic response and predicting the performance of modern rockfill dams subjected to strong earthquake shaking are reviewed. The focus is on methods accounting for nonlinear material behavior, for 3-Dimensional canyon geometry, and asynchronous base excitation. It is shown that both strong nonlinearities and lack of coherence in the seismic excitation tend to reduce the magnitude of the deleterious "whip-lash" effect computed for tall dams built in rigid-wall narrow canyons. Particular emphasis is accorded to Concrete-Faced Rockfill dams and a case study involving an actually designed dam in a narrow canyon points to some potential problems and suggests some desirable modifications. In the light of theoretical results the paper concludes with a discussion on design rules and defensive measures that would lead to robust design schemes of Earth-Core and Concrete Faced Rockfill dams. Consequently, the method may not reproduce adequately the details of the response history.
Theoretical methods for estimating the dynamic response and predicting the performance of modern ... more Theoretical methods for estimating the dynamic response and predicting the performance of modern rockfill dams subjected to strong earthquake shaking are reviewed. The focus is on methods accounting for nonlinear material behavior, for 3-dimensional canyon geometry, and asynchronous base excitation. It is shown that both strong nonlinearities and lack of coherence in the seismic excitation tend to reduce the magnitude of the deleterious 'whip-lash' effect computed for tall dams built in rigid narrow canyons. Particular emphasis is accorded to Concrete-Faced-Rockfill dams and a case study involving an actually designed dam in a narrow canyon points to potential problems and suggests desirable modifications. In the light of theoretical results, the paper concludes with a discussion on design rules and defensive measures that would lead to robust design schemes of Earth-Core and Concrete-Faced Rockfill dams. Field verification through records of seismic response is, however, a prerequisite for the confident adoption of such measures in practice.
The Twenty-second International Offshore and Polar Engineering Conference, 2012
The paper examines the behaviour of buried steel pipelines crossing active strike-slip faults. Th... more The paper examines the behaviour of buried steel pipelines crossing active strike-slip faults. The vertical fault plane is crossed by the pipeline at an angle ranging between zero and 45 degrees, causing significant plastic deformation in the pipeline. The investigation is numerical, simulating the nonlinear response of the soil-pipeline system rigorously through nonlinear finite elements, accounting for inelastic material behaviour of the pipeline and the pipe and the soil, as well as contact and friction on the soil-pipe interface. Steel pipes with D/t ratio and material grade typical for hydrocarbon pipelines are analyzed, through an incremental application of fault displacement and appropriate pipeline performance criteria, defined within a strain-based design framework, are monitored throughout the analysis. The effects of various soil and linepipe parameters on the structural response of the pipeline are examined. The numerical results from the present investigation determine the fault displacement at which the specified performance criteria are reached, including the effects of internal pressure.
A new approach for liquefaction flow failure evaluation of earth dams is presented. The method ap... more A new approach for liquefaction flow failure evaluation of earth dams is presented. The method applies steady-state concepts, and is based on the premise that flow failure of an earth dam takes place in two consecutive stages: a first stage of pore pressure buildup, controlled by the horizontal seismic shear strains, and a second stage of unidirectional steady-state flow failure, driven by the static shear stresses, associated with the weight of the sliding mass. A simplified method of determining seismic shear strains is also presented. For the covering abstract of the conference see IRRD 287689. (Author/TRRL)
Results from simplified analytical and numerical models on vibrational characteristics of earth d... more Results from simplified analytical and numerical models on vibrational characteristics of earth dams in narrow canyons are presented. The effect of the canyon length over height ratio on the fundamental period of the dam is illustrated for five idealized canyons shapes: increasing canyon narrowness results in a decrease of the natural period. In contrast, a deformable underlying soil layer in the middle of the valley is shown to lengthen the natural period. Useful closed-form expressions for natural frequencies, displacement shapes, participation factors, and acceleration amplification functions are presented in a table. Acceleration amplification functions at midcrest are plotted versus a dimensionless frequency for various canyon shapes. A simple model of a dam in a semicylindrical canyon is used to demonstrate that flexible canyon boundaries may significantly reduce mid-crest accelerations due to energy radiation. Moreover, soil nonlinearities that develop during strong base motion may reduce drastical...
Journal of Pipeline Systems Engineering and Practice, Feb 1, 2021
AbstractPipelines transporting oil and natural gas may experience upheaval buckling due to substa... more AbstractPipelines transporting oil and natural gas may experience upheaval buckling due to substantial compressive forces induced by high temperature and pressure of the fluid content. Such upheava...
This General Report is presented in the following four sections. In the first section a brief sta... more This General Report is presented in the following four sections. In the first section a brief state-of-the art review is given related to the following topics (covered by the papers presented in this session): (i) analysis of embankment stability during earthquakes; (ii) liquefaction potential of saturated soils during earthquakes; (iii) behaviour of tailings dams and waste disposals during seismic events; and (iv) assessment of failure of natural slopes during earthquakes. In the second section a summary of each paper is presented followed by general comments. The third section presents some future trends and the final section presents some remarks and topics for discussion.
Following the January 1994 Northridge Earthquake in Southern California, the authors traveled to ... more Following the January 1994 Northridge Earthquake in Southern California, the authors traveled to Los Angeles and surveyed the earthquake damage region. Subsequently, seismologic, geologic and ground motion data were compiled and evaluated. This paper presents our observations and evaluation of: geologic and soil effects; soil-structure interaction; liquefaction; slope failures and rock slides; and ground deformations.
A mathematical solution is presented for steady-state lateral response of earth and rock fill dam... more A mathematical solution is presented for steady-state lateral response of earth and rock fill dams in canyons subjected to asynchronous excitation consisting of obliquely incident SH waves. The dam is idealized with a 2-dimensional shear wedge and the canyon is considered rectangular and consisting of flexible rock. A parametric study is undertaken to investigate the influence of (a) the angle of incidence, (b) the impedance ratio and (c) the canyon narrowness on the steady-state response, by considering in a simplifying way the effects of the dam-canyon interaction. The results demonstrate that the above factors may have a significant effect on the lateral response of the dam. For relatively flexible canyon rock, the effect of radiation damping is very important and, consequently, the assumption of rigid base may be very unrealistic. Due to interference phenomena, the response is not maximum for vertically propagating waves, but for waves incident at a certain angle. For obliquely incident waves travelling from left to the right, a gradual shift of the location of the peak response is observed from the mid-crest to the right side of the dam as the angle of incidence increases. Also, for very long dams subjected to high frequency obliquely incident waves, there is no amplification of the motion by the dam and, at a certain frequency of excitation, the presence of standing waves is indicated.
SYNOPSIS A study of the effects of dam-foundation interaction on the response of earth dams to ob... more SYNOPSIS A study of the effects of dam-foundation interaction on the response of earth dams to obliquely incident P and SV waves is presented. The numerical formulation combines the Finite Element Method and the Boundary Equation Method in a powerful hybrid technique. The FEM has been proven very efficient for finite size elastodynamics problems, but several previously suggested modifications for handling infinite domain dynamic problems seem to be either computationally expensive or have serious limitations on the geometry and excitation. The BEMis employed to solve the halfspace problem using exact Green's functions to compute the halfspace stiffness, which is then incorporated in the FEM solution. This technique proved to be exceptionally powerful as it leads to accurate and very efficient solutions. A preliminary study is undertaken to investigate the response of dams subjected to obliquely incident P and SV waves, propagating across the dam width. The results of the present rigorous study extend the conclusions from earlier studies on the effects of the dam-foundation interaction and the special variability of the ground motion. Moreover, the proposed model provides an efficient tool for dynamic analysis of earth dams and is part of a broader study of 2D and 3D dams using the hybrid formulation in both the frequency and time domains, with final objective the incorporation, in the latter case, of soil nonlinearity.
We have investigated in detail the properties of a model comet nucleus composed of'an icydust soi... more We have investigated in detail the properties of a model comet nucleus composed of'an icydust soil. The thermal properties are predicted and related to the observable phenomena seen in the many comet comae and the fly-bye images of Comet Halley. A thorough review of the literature on this subject was made and reported upon in this document.
Theoretical methods for estimating the dynamic response and predicting the performance of modern ... more Theoretical methods for estimating the dynamic response and predicting the performance of modern rockfill dams subjected to strong earthquake shaking are reviewed. The focus is on methods accounting for nonlinear material behavior, for 3-Dimensional canyon geometry, and asynchronous base excitation. It is shown that both strong nonlinearities and lack of coherence in the seismic excitation tend to reduce the magnitude of the deleterious "whip-lash" effect computed for tall dams built in rigid-wall narrow canyons. Particular emphasis is accorded to Concrete-Faced Rockfill dams and a case study involving an actually designed dam in a narrow canyon points to some potential problems and suggests some desirable modifications. In the light of theoretical results the paper concludes with a discussion on design rules and defensive measures that would lead to robust design schemes of Earth-Core and Concrete Faced Rockfill dams. Consequently, the method may not reproduce adequately the details of the response history.
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