scholarly journals Laboratory and field determination of preconsolidation pressures at Gloucester

1983 ◽  
Vol 20 (3) ◽  
pp. 477-490 ◽  
Author(s):  
S. Leroueil ◽  
L. Samson ◽  
M. Bozozuk
Keyword(s):  
Test Site ◽  
Test Methods ◽  
Strain Rate Effects ◽  
Oedometer Test ◽  
Undisturbed Samples ◽  
Preconsolidation Pressure ◽  
Constant Rate ◽  
Rate Effects

In recent literature several special test methods have been proposed to measure the preconsolidation pressure of a compressible clay soil. Five methods, in addition to the conventional oedometer test, were applied to the marine clays from the Gloucester test site. The preconsolidation pressures measured using these laboratory tests were compared with that mobilized in situ below the centre of a test embankment. The investigation showed that the preconsolidation pressure is directly related to the rate of strain and that special techniques such as constant rate of strain, controlled gradient, single-stage loading, and anisotropic triaxial consolidation tend to overestimate the in-situ preconsolidation pressure. The conventional oedometer test using a load increment ratio of 0.5 and a reloading schedule of 24 h applied to good-quality undisturbed samples produced preconsolidation pressures that compared best with the in-situ values. Keywords: preconsolidation pressure, laboratory, in situ, strain rate effects, disturbance.

In situ estimation of the coefficient of consolidation in clays

1990 ◽  
Vol 27 (1) ◽  
pp. 58-67 ◽  
Author(s):  
Mohammed G. Kabir ◽  
Alan J. Lutenegger
Keyword(s):  
Key Words ◽  
Pore Pressure ◽  
Reference Values ◽  
Time Factors ◽  
In Situ Tests ◽  
Coefficient Of Consolidation ◽  
Oedometer Test ◽  
Undisturbed Samples ◽  
Oedometer Tests

An investigation was conducted to demonstrate the applicability of cylindrical piezocone and flat piezoblade tests for providing reliable estimates of the coefficient of consolidation in clays. Coefficients of consolidation were calculated from piezocone dissipation tests for different degrees of consolidation using theoretical time factors to provide a comparison with laboratory oedometer tests. Three techniques were developed to calculate the coefficient of consolidation from piezoblade dissipation tests. Results from in situ pore pressure dissipation tests were compared with laboratory oedometer tests performed on undisturbed samples oriented in both the vertical and horizontal directions, to provide reference values of cv and ch. The results of investigations conducted at several clay sites are presented. Key words: in situ tests, piezocone, piezoblade, coefficient of consolidation, oedometer test, clays.

Estimation of Liquefaction Potential by in Situ Methods

1995 ◽  
Vol 11 (3) ◽  
pp. 431-455 ◽  
Author(s):  
Steven D. Glaser ◽  
Riley M. Chung
Keyword(s):  
Seismic Velocity ◽  
State Of The Art ◽  
Test Methods ◽  
Estimation Methods ◽  
Penetration Test ◽  
Liquefaction Potential ◽  
Current State ◽  
Undisturbed Samples ◽  
In Situ Methods

This report examines the state-of-the-art of in situ methods of estimating liquefaction potential in sands. In situ methods are especially important since “undisturbed” samples of loose sand for laboratory testing are virtually unobtainable. Various penetration test methods are examined, such as the SPT, DMT, and the CPT and variants. These methods are completely empirical in nature, and have worked well to date. The current state-of-practice is an SPT-based method. Intrusive, seismic-based tests are also examined: the cross-hole, down-hole tests, and down-hole logger. The seismic velocity-based predictors have a stronger physical basis than the penetration test-based estimation methods, but need a larger database. A non-intrusive test, the Spectral Analysis of Surface Waves technique, seems especially suited for examining sites of large areal extent.

Interpretation of overconsolidation ratio from in situ tests in Recent clay deposits in Singapore and Malaysia

1991 ◽  
Vol 28 (2) ◽  
pp. 210-225 ◽  
Author(s):  
M. F. Chang
Keyword(s):  
Site Investigation ◽  
Test Methods ◽  
In Situ Tests ◽  
Stress History ◽  
Overconsolidation Ratio ◽  
Clay Deposits ◽  
Preconsolidation Pressure ◽  
Pressure Stress ◽  
Sample Disturbance

The stress history as indicated by the profile of overconsolidation ratio (OCR) of a soil deposit is one of the most dominant factors that influence the engineering behaviour of the soil. Its assessment, which is traditionally based on the laboratory oedometer test, is not often satisfactory. The problem arises from inevitable sample disturbance and the high cost of a detailed investigation. These difficulties can be overcome by the use of in situ tests. The field vane test, the piezocone test, and the dilatometer test are three such methods that provide indirect means for the estimation of the OCR for clay deposits. A number of empirical correlations are available for this purpose. Calibration of these correlations against results of site investigation in Singapore and Malaysian marine clays reveals the usefulness of these test methods in profiling the OCR for Recent clay deposits. Key words: clay, in situ test, overconsolidation ratio, preconsolidation pressure, stress history.

Preconsolidation pressure of Champlain clays. Part I. In-situ determination

1983 ◽  
Vol 20 (4) ◽  
pp. 782-802 ◽  
Author(s):  
P. Morin ◽  
S. Leroueil ◽  
L. Samson
Keyword(s):  
Laboratory Tests ◽  
Research Study ◽  
Simple Correlation ◽  
Eastern Canada ◽  
Existing Structures ◽  
Undisturbed Samples ◽  
Preconsolidation Pressure ◽  
Oedometer Tests

The preconsolidation pressure of sensitive clays is an important parameter for the design of foundations on these soils, which are widespread in Eastern Canada and above all in the St. Lawrence and Ottawa Valleys where Champlain clays are found. A research study was initiated in 1979 to assess whether the preconsolidation pressure values derived from laboratory tests are representative of the preconsolidation pressure effectively mobilized in situ.Several existing structures were investigated and five of them are presented with performance records taken during and after construction together with data obtained from recent soil investigations. For each case study, the in-situ preconsolidation pressure is determined from the analysis of settlement and/or pore pressure records.The preconsolidation pressure values derived from conventional oedometer tests on good quality undisturbed samples are compared with the in-situ values and a simple correlation taking into account the overconsolidation ratio of the clay is proposed. Keywords: preconsolidation pressure, in-situ, laboratory, Champlain sea clays.

An approach for the determination of the preconsolidation pressure in sensitive clays

1980 ◽  
Vol 17 (3) ◽  
pp. 446-453 ◽  
Author(s):  
S. Leroueil ◽  
J. P. LeBihan ◽  
F. Tavenas
Keyword(s):  
Pore Pressure ◽  
Theoretical Basis ◽  
Axial Stress ◽  
New Method ◽  
One Stage ◽  
Preconsolidation Pressure ◽  
Constant Rate ◽  
Constant Gradient ◽  
Oedometer Tests

The present methods for the determination of the preconsolidation pressure of clays are time consuming and expensive. A new method is proposed in which the clay is loaded in a "one-stage loading" to an axial stress in excess of the estimated preconsolidation pressure. The preconsolidation pressure is determined from the observation of the pore pressure dissipation within a few hours. The theoretical basis of this method is also used to discuss the method of interpreting constant rate of strain and constant gradient oedometer tests.

Strain rate behaviour of Saint-Jean-Vianney clay

1979 ◽  
Vol 16 (1) ◽  
pp. 34-42 ◽  
Author(s):  
Y. P. Vaid ◽  
P. K. Robertson ◽  
R. G. Campanella
Keyword(s):  
Undrained Shear Strength ◽  
Shear Tests ◽  
Creep Tests ◽  
One Dimensional ◽  
Sustained Loading ◽  
Preconsolidation Pressure ◽  
Constant Rate ◽  
Rate Effects ◽  
Undrained Strength ◽  
Rate Behaviour

Rate effects on one-dimensional compressibility and undrained shear strength of a heavily overconsolidated naturally cemented clay have been studied. It is shown that in constant rate-of-strain consolidation tests the compressibility increases and the apparent preconsolidation pressure decreases with progressive decrease in rate of strain. Also a decrease in undrained strength is shown to occur with slower rates of strain in constant rate-of-strain shear and with increased time of sustained loading in creep tests. Undrained strengths from the two types of shear tests have been correlated.

Quality of samples retrieved from great depth and its influence on consolidation properties

2002 ◽  
Vol 39 (6) ◽  
pp. 1288-1301 ◽  
Author(s):  
Hiroyuki Tanaka ◽  
Fusao Ritoh ◽  
Naoki Omukai
Keyword(s):  
Void Ratio ◽  
Volumetric Strain ◽  
Great Depth ◽  
Sampling Depth ◽  
Osaka Bay ◽  
Oedometer Test ◽  
Preconsolidation Pressure ◽  
Constant Rate ◽  
Sample Disturbance

Pleistocene sediments deposited in Osaka Bay have been extensively investigated to depths of up to 400 m. Consolidation properties, especially preconsolidation pressure, are somewhat scattered with depth. The quality of samples retrieved from great depths has been evaluated based on the indices calculated from the volumetric strain or the void ratio changes in the recompression process. The study reveals that these indices do not simply increase with an increase in sampling depth. The potential for sample disturbance during sample setting in the constant rate of strain (CRS) oedometer was also investigated. These tests have revealed that the preconsolidation pressure, as measured in the laboratory, is not influenced significantly by swelling. In addition, preconsolidation pressures indicate that the sediments are slightly overconsolidated, with a departure from normally consolidated behaviour that could be explained by cementation.Key words: sampling, preconsolidation pressure, sample disturbance, oedometer test, Pleistocene clay, great depth.

Viscous–elastic–plastic modelling of one-dimensional time-dependent behaviour of clays

1989 ◽  
Vol 26 (2) ◽  
pp. 199-209 ◽  
Author(s):  
J.-H. Yin ◽  
J. Graham
Keyword(s):  
Strain Rate ◽  
Constitutive Models ◽  
Constitutive Modelling ◽  
Time Dependent ◽  
Creep Tests ◽  
Strain Rate Effects ◽  
One Dimensional ◽  
Elastic Plastic ◽  
Constant Rate ◽  
Rate Effects

Increased attention has recently been directed towards the influence of time and strain-rate effects on the behaviour of clays in one-dimensional (1-D) laboratory consolidation. The improved understanding coming from these studies must now be incorporated into improved constitutive models that can be used for analysis of foundation settlements. This paper presents a 1-D model for stepped loading using a new concept for establishing "equivalent times" during time-dependent straining. This model is then developed into a general constitutive equation for continuous loading. The model uses three parameters, λ, κ, and ψ, that can be easily found using conventional oedometer tests.The general model has been used to develop analytical solutions for creep tests, relaxation tests, constant rate of strain (CRSN) tests, and tests with constant rate of stress (CRSS). Results from three different clays have been used to examine the validity of the model. Key words: consolidation, constitutive modelling, elastic-plastic, viscous, time, creep, strain rate, relaxation.

On the Buckley-Leverett Equation With Constant-Pressure Boundary Conditions

SPE Journal ◽  
2016 ◽  
Vol 21 (06) ◽  
pp. 2301-2307 ◽  
Author(s):  
Thormod E. Johansen ◽  
Lesley A. James ◽  
Xiaolong Liu
Keyword(s):  
Analytical Solution ◽  
Flow Rate ◽  
Constant Pressure ◽  
Analytical Determination ◽  
Constant Flow Rate ◽  
Displacement Front ◽  
Constant Rate ◽  
Volumetric Flux

Summary The classical Buckley-Leverett theory applies to 1D linear flow of two immiscible phases under the fundamental assumption that the flow rate (or total volumetric flux) is constant as a function of time. One phase is injected into the medium at a constant rate, thereby displacing the other phase. If the displacing phase is instead injected at constant pressure and the outlet pressure is also constant, the problem is still well-defined; however, the classical Buckley-Leverett theory does not apply. This is because the injected phase and the in-situ phase have different properties such as viscosities. If the boundary pressures are kept constant, the flow rate will, therefore, vary over time. The main result of this paper is to show that the solution of the displacement problem can be obtained from the constant-rate solution through an analytical determination of the flow rate as a function of time, given constant-pressure boundaries. The theory developed in this paper also provides an analytical solution for the location of the displacement front at any given time, the time for frontal breakthrough at the outlet end, and the pressure distribution as a function of time inside the medium. It is demonstrated through computed examples that the constant-flow-rate solution, in general, cannot be used to approximate the corresponding solution for constant-pressure boundaries because the variation in the flow rate is very significant. A standard numerical method has also been applied and compared with the analytical solutions, demonstrating that fine numerical-simulation grids are required for acceptable comparison with the analytical solution.

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