The liquefaction of sands, a collapse surface approach

1985 ◽  
Vol 22 (4) ◽  
pp. 564-578 ◽  
Author(s):  
J. A. Sladen ◽  
R. D. D'Hollander ◽  
J. Krahn
Keyword(s):  
Steady State ◽  
Large Scale ◽  
Soil Mechanics ◽  
Limit Equilibrium ◽  
Three Dimensional ◽  
Beaufort Sea ◽  
Triaxial Tests ◽  
Necessary Condition ◽  
State Testing ◽  
Hydraulic Fill

Recent large-scale slides occurring during the hydraulic placement of an artificial island berm in the Beaufort Sea resulted from the liquefaction of the berm sand. Subsequent laboratory tests and back analyses have led to advancements in the understanding of the liquefaction potential of sand. Analyses of undrained triaxial tests, undertaken to measure steady state parameters, suggest that there is a "collapse surface" in three-dimensional void ratio – shear stress – normal stress space. A necessary condition for liquefaction is that the soil state lie on this surface. This collapse surface concept is fundamentally an extension of the steady state concepts proposed by others, and in many respects follows the principles of critical state soil mechanics. Replotted published tests support the concept. Parameters used to describe the position of the surface are termed collapse parameters. These can be converted into parameters analogous to Mohr–Coulomb failure parameters and can therefore be used in conventional limit equilibrium stability analyses. Utilizing these parameters overcomes limitations inherent in previously proposed undrained steady state analysis methods. These concepts also provide a basis for a rational explanation of the Beaufort Sea hydraulic fill slides. Key words: liquefaction, sand, hydraulic fill, slope stability, steady state testing.

Three-Dimensional Response of Buried Pipelines Subjected to Large Soil Deformation Effects: Part II—Effects of the Soil Restraint on the Response of Pipe/Soil Systems

2010 ◽  
Author(s):  
Abdelfettah Fredj ◽  
Aaron Dinovitzer
Keyword(s):  
Large Scale ◽  
Numerical Models ◽  
Soil Mechanics ◽  
Three Dimensional ◽  
Ground Movement ◽  
Assessment Process ◽  
Pipeline System ◽  
Integrity Assessment ◽  
Soil Systems ◽  
Large Soil

Understanding the effect of soil-pipeline interactions in the event of large ground movement is an important consideration for pipeline designer. Both experimental investigation and computational analyses play significant roles in this research. As part of this effort, a framework incorporating continuum soil mechanics and advanced finite element approach (i.e., ALE and SPH method) for modeling soil pipe interaction is developed. The overall objective is to develop, validate and apply 3D continuum modeling technique to assess the performance of pipeline system subjected to large soil displacement. The numerical models than may be used to predict the wrinkle formation and post formation behavior of the pipeline considering the effect of the soil confinement, and develop a comprehensive wrinkle integrity assessment process. This is the second paper (Part II) in a series of two papers. In the first paper a three-dimensional Continuum models using MM-ALE (Multi-material Arbitrary Eulerian Lagrangian) and SPH (smooth particle hydrodynamics) approaches are developed and run using LS-DYNA. The results are compared with published experimental data of large-scale test to verify the numerical analysis methods. In this paper (Part II) the effects of soil restraint on the response of the pipe/soil systems (e.g., pipeline Wrinkle and buckle, strain demand) are discussed.

scholarly journals Inverse-model estimates of the ocean's coupled phosphorus, silicon, and iron cycles

2017 ◽  
Author(s):  
Benoît Pasquier ◽  
Mark Holzer
Keyword(s):  
Steady State ◽  
Ocean Circulation ◽  
Large Scale ◽  
Three Dimensional ◽  
Nutrient Utilization ◽  
Global Ocean ◽  
Nutrient Concentrations ◽  
Iron Source ◽  
Fractional Contribution ◽  
Wide Range

Abstract. The ocean's nutrient cycles are important for the carbon balance of the climate system and for shaping the ocean's distribution of dissolved elements. Dissolved iron (dFe) is a key limiting micronutrient, but iron scavenging is observationally poorly constrained leading to large uncertainties in the external sources of iron and hence in the state of the marine iron cycle. Here we build a model of the ocean's coupled phosphorus, silicon, and iron cycles embedded in a data-assimilated steady-state global ocean circulation. The model includes the redissolution of scavenged iron, parameterization of subgrid topography, and small, large, and diatom phytoplankton functional classes. Phytoplankton concentrations are implicitly represented in the parameterization of biological nutrient utilization through an equilibrium logistic model. Our coupled nutrient model thus carries only three nutrient tracers whose three-dimensional steady-state distributions can be found efficiently using a Newton solver. The very efficient numerics allow us to use the model in inverse mode to objectively constrain many biogeochemical parameters by minimizing the mismatch between modelled and observed nutrient and phytoplankton concentrations. We consider a family of possible solutions corresponding to a wide range of external iron source strengths. Iron source and sink parameters cannot jointly be optimized because of local compensation between regeneration, recycling, and scavenging. All optimized solutions have a similar mismatch with the observed nutrient concentrations and very similar large-scale dFe distributions. However, the relative contributions of aeolian, sedimentary, and hydrothermal iron to the total dFe concentration differ widely depending on the sources. Both the magnitude and pattern of carbon and opal export are well constrained with global values of (10.3 ± 0.4) Pg C yr−1 and (171. ± 3.) Tmol Si yr−1. We diagnose the carbon and opal export supported by aeolian, sedimentary, and hydrothermal iron. The geographic patterns of the export supported by each iron type are well constrained across the family of solutions. Sedimentary-iron supported export is important in shelf and large-scale upwelling regions, while hydrothermal iron contributes to export mostly in the Southern Ocean. The globally integrated export supported by a given iron type varies systematically with the fractional contribution of its source to the total iron source. Aeolian iron is most efficient in supporting export in the sense that its fractional contribution to export exceeds its fractional contribution to the total source by as much as ~ 30 % for carbon and ~ 20 % for opal export. Conversely, sedimentary and hydrothermal iron are less efficient with a fractional export that is less than their fractional sources. For the same fractional contribution to the total source, hydrothermal iron is less efficient than sedimentary iron for supporting carbon export but about equally efficient for supporting opal export.

scholarly journals Is helicity relevant for large scale steady state three-dimensional turbulence ?

1978 ◽  
Vol 39 (13) ◽  
pp. 199-203 ◽  
Author(s):  
A. Pouquet ◽  
J.-D. Fournier ◽  
P.-L. Sulem
Keyword(s):  
Steady State ◽  
Large Scale ◽  
Three Dimensional

scholarly journals Steady-state Operation Area of VSC-HVDC Converter Station Connecting Renewable Energy Cluster by Isolated Network

2020 ◽  
Vol 182 ◽  
pp. 02003
Author(s):  
Wenyuan Xian ◽  
Ran Ding ◽  
Ying Qiao ◽  
Zongxiang Lu ◽  
Shangqiang Li ◽  
...  
Keyword(s):  
Renewable Energy ◽  
Steady State ◽  
Large Scale ◽  
Three Dimensional ◽  
Equivalent Model ◽  
Fast Method ◽  
Hvdc Transmission ◽  
Renewable Power ◽  
Steady State Operation ◽  
Transformer Ratio

When the large-scale renewable power island is connected to VSC-HVDC transmission system, we should figure out the steady-state operation area of VSC-HVDC converter station. Based on the equivalent model of renewable energy island, the constraints of VSC-HVDC converter station are analyzed, and a fast method for calculating steady-state operation area of converter station is presented in this paper. The influence of equivalent line impedance of renewable energy island, transformer ratio of converter station and voltage setting value of grid-connected point on steady-state operation area of converter station is analyzed. And the three-dimensional view of the steady-state operation area of the converter station under different grid-connected voltage is depicted.

scholarly journals Comparison of Three Contemporary Flow Laws in a Three-Dimensional, Time-Dependent Glacier Model

1973 ◽  
Vol 12 (66) ◽  
pp. 361-373 ◽  
Author(s):  
L. A. Rasmussen ◽  
W. J. Campbell
Keyword(s):  
Shear Stress ◽  
Steady State ◽  
Large Scale ◽  
Three Dimensional ◽  
Time Dependent ◽  
Flow Law ◽  
Glacier Flow ◽  
Basal Shear ◽  
Basal Flow ◽  
Flow Laws

A numerical model for three-dimensional, time-dependent glacier flow (Campbell and Rasmussen, 1970) treated the ice as a Newtonian viscous fluid and related its dynamics to two large-scale bulk parameters: the viscosity v determining the ice-to-ice friction, and a basal friction parameter A determining the ice-to-rock friction. The equations were solved using the relatively simple flow law of Bodvarsson (1955) in which the basal shear stress is proportional to volume transport. Recent research suggests that a more realistic basal flow law is one in which the basal shear stress to some lower power (1–3) is either proportional to the vertically averaged velocity (Glen, 1958; Nye, 1960, 1963[a], [b], [c], 1965[a], [b], [c]) or to the ratio of the vertically averaged velocity to glacier thickness (Budd and Jenssen, in press).In the present study a generalized flow law incorporating all of the above bulk basal flow laws is applied to the Campbell–Rasmussen momentum equation to form a generalized two-dimensional transport equation, which, when combined with the continuity equation, yields a numerically tractable set of equations for three-dimensional, time-dependent glacier flow. Solutions of the model are shown for steady-state flow and surge advance and recovery for a typical valley glacier bed for powers 1, 2, and 3 for each of the basal flow laws for a steady-state climate input and a given ice-to-ice viscosity parameter.

Analyse de la liquéfaction et du comportement non drainé des sables du delta de Kenamu (Projet ADFEX)

1995 ◽  
Vol 32 (1) ◽  
pp. 137-155 ◽  
Author(s):  
Réjean Couture ◽  
Jacques Locat ◽  
Jean-Marie Konrad
Keyword(s):  
Steady State ◽  
Void Ratio ◽  
Boundary Region ◽  
Triaxial Tests ◽  
Necessary Condition ◽  
Delta Front ◽  
Liquefaction Potential ◽  
Submarine Slide ◽  
Delta Sediments ◽  
Lower Limits

Jointly sponsored by France, Norway, and Canada, the ADFEX project (Artic Delta Failure Experiment) aims at triggering a full-scale submarine slide. For that purpose, a delta is destabilized by blasting to induce instantaneous liquefaction of the delta front. The selected site is the delta of Kenamu River at Melville Lake (Labrador), located approximately 40 km northeast of Goose Bay. The delta sediments are angular fine silty sands constituted mainly of quartz. A series of consolidated isotropically and undrained triaxial tests was performed on specimens of reconstituted loose sands to establish the boundaries between the contracting and dilating behaviours (steady state line or F line) and the upper and lower limits of the boundaries within the bidimensional diagram void ratio – mean effective stress. A soil state above this boundary region constitutes a necessary condition to liquefaction. The results of the triaxial tests are used to evaluate the liquefaction potential of Kenamu delta. Key words : liquefaction, sand, steady state, triaxial test, undrained, delta.

scholarly journals Observed and predicted behaviour of rail ballast under monotonic loading capturing particle breakage

2015 ◽  
Vol 52 (1) ◽  
pp. 73-86 ◽  
Author(s):  
Buddhima Indraratna ◽  
Qi Deng Sun ◽  
Sanjay Nimbalkar
Keyword(s):  
Critical State ◽  
Large Scale ◽  
Soil Mechanics ◽  
Confining Pressure ◽  
Particle Breakage ◽  
Shear Behaviour ◽  
Triaxial Tests ◽  
Triaxial Apparatus ◽  
Elastoplastic Constitutive Model ◽  
Constitutive Parameters

A substantial amount of experimental evidence suggests that the critical state envelope for ballast is nonlinear, especially at low confining pressure. To study the implications of this nonlinearity and the associated role of particle breakage, monotonically loaded drained triaxial tests were conducted using a large-scale cylindrical triaxial apparatus. A nonlinear critical state envelope is determined in the q–p′ and υ–lnp′ planes. Mathematical expressions for critical state stress ratio and specific volume are proposed to incorporate the evolution of particle breakage during monotonic shearing. In this paper, an elastoplastic constitutive model based on the critical state soil mechanics framework is presented to capture the salient aspects of stress–strain behaviour and degradation of ballast. Constitutive parameters were conveniently determined from large-scale laboratory tests. The model is able to predict the monotonic shear behaviour of ballast corroborating with the laboratory measurements. The proposed model is further validated using experimental results available from past independent studies.

scholarly journals Comparison of Three Contemporary Flow Laws in a Three-Dimensional, Time-Dependent Glacier Model

1973 ◽  
Vol 12 (66) ◽  
pp. 361-373 ◽  
Author(s):  
L. A. Rasmussen ◽  
W. J. Campbell
Keyword(s):  
Shear Stress ◽  
Steady State ◽  
Large Scale ◽  
Three Dimensional ◽  
Time Dependent ◽  
Flow Law ◽  
Glacier Flow ◽  
Basal Shear ◽  
Basal Flow ◽  
Flow Laws

A numerical model for three-dimensional, time-dependent glacier flow (Campbell and Rasmussen, 1970) treated the ice as a Newtonian viscous fluid and related its dynamics to two large-scale bulk parameters: the viscosity v determining the ice-to-ice friction, and a basal friction parameter A determining the ice-to-rock friction. The equations were solved using the relatively simple flow law of Bodvarsson (1955) in which the basal shear stress is proportional to volume transport. Recent research suggests that a more realistic basal flow law is one in which the basal shear stress to some lower power (1–3) is either proportional to the vertically averaged velocity (Glen, 1958; Nye, 1960, 1963[a], [b], [c], 1965[a], [b], [c]) or to the ratio of the vertically averaged velocity to glacier thickness (Budd and Jenssen, in press). In the present study a generalized flow law incorporating all of the above bulk basal flow laws is applied to the Campbell–Rasmussen momentum equation to form a generalized two-dimensional transport equation, which, when combined with the continuity equation, yields a numerically tractable set of equations for three-dimensional, time-dependent glacier flow. Solutions of the model are shown for steady-state flow and surge advance and recovery for a typical valley glacier bed for powers 1, 2, and 3 for each of the basal flow laws for a steady-state climate input and a given ice-to-ice viscosity parameter.

The Nerlerk berm case history: some considerations for the design of hydraulic sand fills

1991 ◽  
Vol 28 (4) ◽  
pp. 601-612 ◽  
Author(s):  
Jean-Marie Konrad
Keyword(s):  
Steady State ◽  
Large Scale ◽  
Void Ratio ◽  
Strain Softening ◽  
Back Analysis ◽  
Confining Stress ◽  
Hydraulic Fill ◽  
State Strength ◽  
Undrained Strength ◽  
Unique Relationship

Back-analyses of recent large-scale slides during the hydraulic placement of an articial sand island at the Nerlerk site (Beaufort Sea) using different methods have resulted in contradictory conclusions with respect to the state of the fill. All the interpretation methods assume a unique relationship between steady-state strength and void ratio. This assumption is, however, not verified, since steady-state strength depends also on effective confining stress. This paper presents the results of a back-analysis at the Nerlerk site using a modified concept proposed by the author which isbased on nonunique values of steady-state strength for a given sand. It is established that the density conditions at Nerlerk, on average at a relative density of about 40%, and the initial stress conditions are conducive to strain softening, with a steady-state strength corresponding to the minimum strength defined by the LF line. For Nerlerk sand,the minimum undrained strength is about 18% of the steady-state strength determined with conventional methods using high confining stresses. The Nerlerk berm failures were thus "liquefaction" slides induced most likely by progressive straining. Key words: sand, undrained, strength, steady state, hydraulic fill.

Three-Dimensional Response of Buried Pipelines Subjected to Large Soil Deformation Effects: Part I—3D Continuum Modeling Using ALE and SPH Formulations

2010 ◽  
Author(s):  
Abdelfettah Fredj ◽  
Aaron Dinovitzer
Keyword(s):  
Large Scale ◽  
Numerical Models ◽  
Soil Mechanics ◽  
Three Dimensional ◽  
Ground Movement ◽  
Assessment Process ◽  
Continuum Modeling ◽  
Integrity Assessment ◽  
Particle Hydrodynamics ◽  
Large Soil

Understanding the effect of soil-pipeline interactions in the event of large ground movement is an important consideration for the pipeline designer. Both experimental investigation and computational analyses play significant roles in soil-pipeline research. As part of this effort, a framework incorporating continuum soil mechanics and advanced finite element approach (i.e., ALE and SPH method) for modeling soil pipe interaction was constructed. The overall objective of this work is to develop, validate and apply 3D continuum modeling techniques to assess the performance of pipeline systems subjected to large soil displacements. The numerical models produced may subsequently be used to predict the wrinkle formation and post formation behavior of the pipeline considering the effect of the soil confinement. The aim is to develop a comprehensive wrinkle integrity assessment process. This is the first paper (Part I) in a series of two papers. In this paper a three-dimensional Continuum models using MM-ALE (Multi-material Arbitrary Eulerian Lagrangian) and SPH (smooth particle hydrodynamics) approaches are developed and employed using LS-DYNA. The results are compared with published experimental data of large-scale tests to verify the numerical analysis methods. In the second paper (Part II) the effects of soil restraint on the response of the pipe/soil systems (e.g., pipeline wrinkle and buckle, strain demand) are discussed.

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