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.

Uniqueness of steady state and liquefaction potential

1994 ◽  
Vol 31 (1) ◽  
pp. 132-139 ◽  
Author(s):  
D. Negussey ◽  
M.S. Islam
Keyword(s):  
Steady State ◽  
Bedding Plane ◽  
Triaxial Tests ◽  
Initial State ◽  
Liquefaction Potential ◽  
Initial Anisotropy ◽  
Anisotropic Consolidation ◽  
Stress States ◽  
Undrained Loading ◽  
Loading Form

A given sand is presumed to have a unique steady-state line. The proximity of an initial state to the steady-state line is considered to be a measure of liquefaction potential. This line of reasoning and application in practice is based on data obtained predominantly from triaxial tests in compression-mode loading. In such tests, relative orientations of bedding plane and principal stress directions remain fixed while stress states along actual failure surfaces may range from active to passive. This study examines the uniqueness of the steady state relative to the mode of loading, form of consolidation, and initial anisotropy as induced by bedding orientation. A sample-preparation method was developed to form triaxial samples with different bedding orientations. Steady states of a uniform sand reached under compressional and extensional modes of triaxial undrained loading of samples with different bedding orientation are compared. Effects of isotropic and anisotropic consolidation are examined. The results indicate the steady-state line obtained for compression-mode loading is different from and does not apply for extension-mode loading. Use of a compression side steady-state line for extension-mode failure states would result in overestimation of steady-state strengths and unconservative stability evaluations. Key words : anisotropy, compression, extension, liquefaction, sand, steady state, triaxial.

A potential systematic error in laboratory testing of very loose sands

1987 ◽  
Vol 24 (3) ◽  
pp. 462-466 ◽  
Author(s):  
J. A. Sladen ◽  
G. Handford
Keyword(s):  
Steady State ◽  
Void Ratio ◽  
Flow Line ◽  
Simple Calculation ◽  
Triaxial Tests ◽  
Steady State Flow ◽  
Laboratory Procedure ◽  
State Flow ◽  
Potential Error

There is a potential error in the determination of specimen void ratio in triaxial tests on very loose sands. This error can be attributed to densification during final saturation. The result can be an error in the determination of the location of the steady state flow line in void ratio – stress space. Stress levels on the steady state flow line at a given void ratio may be in error by two orders of magnitude. If carried through to the analysis of susceptibility to liquefaction, this potential error could be extremely unconservative. Test results are presented that illustrate this potential source of error. A laboratory procedure is proposed that provides a simple calculation of final specimen void ratio and is potentially more accurate than presently used procedures. Key words: triaxial testing, sand, liquefaction, steady state.

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.

scholarly journals Selection of Cosmological Models Using QSOs

1972 ◽  
Vol 44 ◽  
pp. 471-473
Author(s):  
R. C. Roeder
Keyword(s):  
General Relativity ◽  
Steady State ◽  
Emission Line ◽  
Cosmological Models ◽  
Present Evidence ◽  
Normal Galaxy ◽  
Steady State Model ◽  
Lower Limits ◽  
Best Fit ◽  
Selection Of

It is assumed that the QSOs are at cosmological distances as indicated by their emission-line redshifts. It is further assumed, as indicated by present evidence, that none of the 21 QSOs with emission-line redshifts, ze, of 2.0 ± 0.1 (or of the 30 with ze = 2.0 ± 0.2) is screened by an intervening normal galaxy. The simplest conclusion from these data is, then, that the screening probability must be less than 0.08 (or 0.06) at ze = 2.0. This, in turn, restricts allowable cosmological models in the (σ0, q0) diagram by providing lower limits for ß0 as a function of q0. One can also rank cosmological models in order of the probability that there be no screening of the 21 (or 30) objects. In either case the steady state model ranks higher than the general relativity models found by Peach to give the best fit in the (m – z) diagram.

scholarly journals The mechanism of Klebsiella pneumoniae nitrogenase action. Pre-steady-state kinetics of H2 formation

1984 ◽  
Vol 224 (3) ◽  
pp. 877-886 ◽  
Author(s):  
D J Lowe ◽  
R N Thorneley
Keyword(s):  
Steady State ◽  
Klebsiella Pneumoniae ◽  
Necessary Condition ◽  
H2 Evolution ◽  
Mofe Protein ◽  
Fe Protein ◽  
Steady State Kinetics ◽  
Rapid Quench ◽  
Steady State Kinetic ◽  
H2 Formation

A comprehensive model for the mechanism of nitrogenase action is used to simulate pre-steady-state kinetic data for H2 evolution in the presence and in the absence of N2, obtained by using a rapid-quench technique with nitrogenase from Klebsiella pneumoniae. These simulations use independently determined rate constants that define the model in terms of the following partial reactions: component protein association and dissociation, electron transfer from Fe protein to MoFe protein coupled to the hydrolysis of MgATP, reduction of oxidized Fe protein by Na2S2O4, reversible N2 binding by H2 displacement and H2 evolution. Two rate-limiting dissociations of oxidized Fe protein from reduced MoFe protein precede H2 evolution, which occurs from the free MoFe protein. Thus Fe protein suppresses H2 evolution by binding to the MoFe protein. This is a necessary condition for efficient N2 binding to reduced MoFe protein.

Liquefaction potential evaluations: energy-based method versus stress-based method

2013 ◽  
Vol 50 (10) ◽  
pp. 1088-1099 ◽  
Author(s):  
Takaji Kokusho
Keyword(s):  
Cyclic Loading ◽  
Strain Energy ◽  
Seismic Energy ◽  
Triaxial Tests ◽  
Sand Layer ◽  
Cyclic Triaxial Tests ◽  
Liquefaction Potential ◽  
Significant Difference ◽  
Sand Deposit ◽  
Energy Dissipated

A dataset of undrained cyclic triaxial tests for liquefaction with parametrically changing relative density and fines content is reviewed and interpreted in the scope of energy. It is found that the strain amplitude or pore-pressure buildup during cyclic loading is uniquely correlated not only to the energy dissipated in soil specimens, but also to strain energy given from outside. Hence, an energy-based method (EBM) is developed in which liquefaction potential can be evaluated by comparing strain energy for liquefaction in a sand layer with upcoming seismic energy without regard to the differences in seismic motions. Comparative studies in soil models demonstrate that the effect of various input motions is intrinsically included in EBM, whereas it has to be considered by choosing proper coefficients in a conventional stress-based method (SBM). Another significant difference is that liquefaction potential tends to be higher for a shallower depth in EBM, while it is vice versa in SBM in a uniform sand deposit.

scholarly journals Experimental Investigation on Shear Strength and Liquefaction Potential of Rubber-Sand Mixtures

2019 ◽  
Vol 2019 ◽  
pp. 1-11 ◽  
Author(s):  
Zhou Enquan ◽  
Wang Qiong
Keyword(s):  
Shear Strength ◽  
Pore Water Pressure ◽  
Water Pressure ◽  
Construction Materials ◽  
Horizontal Displacement ◽  
Triaxial Tests ◽  
Hyperbolic Model ◽  
Liquefaction Potential ◽  
Direct Shear Tests ◽  
Rubber Particles

The application of scrap tires as construction materials in civil engineering is one of the most promising ways to recycle this pollutant. The objective of this study was to investigate the shear strength and liquefaction potential of saturated rubber-sand mixtures. Direct shear tests and cyclic triaxial tests were conducted on rubber-sand mixtures at various rubber contents. It was found that the addition of rubber particles to sand changed the shear stress-horizontal displacement development. The addition of rubber particles to sand improved the shear strength slightly and improved resistance to liquefaction significantly. Additionally, a hyperbolic model was proposed to describe the pore water pressure generation. This study demonstrates the effect of rubber particles on the physical properties of sand.

scholarly journals The Influence of Kaolinite - Illite toward mechanical properties of Claystone

2019 ◽  
Vol 11 (1) ◽  
pp. 440-446
Author(s):  
Supandi Supandi ◽  
Zufialdi Zakaria ◽  
Emi Sukiyah ◽  
Adjat Sudradjat
Keyword(s):  
Mechanical Properties ◽  
Physical Properties ◽  
Void Ratio ◽  
Correlation Coefficients ◽  
Physical And Mechanical Properties ◽  
Friction Angle ◽  
Engineering Properties ◽  
Rock Properties ◽  
Triaxial Tests ◽  
Mineralogical Characteristics

Abstract This study investigates the relationship between clay minerals (kaolinite and illite) and rock properties of the claystone, including both mechanical (cohesion, friction angle, stress, and strain) and physical properties (natural water content, void ratio, and wet density), belonging to Warukin Formation of Kalimantan, Indonesia. Mineralogical characteristics of these rocks were studied using petrological and X-ray diffraction techniques, whereas the mechanical and physical properties were tested by conducting uniaxial and triaxial tests. Relationship among the variables was determined using correlation coefficients. It was observed that the mineralogy of the rocks pose strong constraints on their engineering properties. The results showed that an increase in illite content decreases cohesion, friction angle, strength, and safety factor; and increases natural moisture content, void ratio, and wet density. Although illite content of these rocks was just about 10.8% of the total minerals, it has significantly contributed to the modification of physical and mechanical properties. In contrast, kaolinite did not have a significant impact; since the correlation between various parameters was significantly low (correlation coefficient was much less, <0.3). Therefore while selecting the materials for geotechnical engineering applications, illite emerges as a safer alternative to kaolinite, especially when its concentration is less than 10.8% of the total rock mass.

Observations on static and cyclic sand-liquefaction methodologies

1992 ◽  
Vol 29 (4) ◽  
pp. 650-665 ◽  
Author(s):  
E. C. McRoberts ◽  
J. A. Sladen
Keyword(s):  
Steady State ◽  
Common Ground ◽  
Input Parameter ◽  
Liquefaction Potential ◽  
Sand Liquefaction ◽  
Cyclic Mobility ◽  
State Of Practice ◽  
Traditional Approaches ◽  
Future Work ◽  
Cyclic Approach

The paper focuses on a review of elements of the liquefaction of sand. Consideration is given to both the static and cyclic approach, and the bases for many of the divergent opinions that currently exist are given. The objective of the paper is to state the arguments and to explore common ground. By considering the inconsistencies that currently exist it is hoped that future work will address issues raised. The real difficulties associated with measurement of the parameters necessary for existing design approaches are highlighted. Because of these difficulties, it is prudent to consider several methods when evaluating liquefaction potential, and practising engineers must often rely on traditional approaches. The state of practice would be improved more by research to address these difficulties than by the development of more elaborate methods of analysis, which are often not justified by the level of precision associated with input parameter measurements. Key words : liquefaction, steady-state, cyclic mobility, critical state.

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