A reevaluation of using laboratory shear tests

1989 ◽  
Vol 26 (1) ◽  
pp. 162-164 ◽  
Author(s):  
G. Mesri
Keyword(s):  
Shear Strength ◽  
Correction Factor ◽  
Slip Surface ◽  
Undrained Shear Strength ◽  
Shear Tests ◽  
Text Data ◽  
Soft Clays ◽  
In Situ Data ◽  
Undrained Shear

The expression [Formula: see text] for the average undrained shear strength mobilized on a slip surface in the field resulted from in situ vane [Formula: see text] and oedometer [Formula: see text] data, combined with a correction factor μ obtained from the computed factor of safety of unstable embankments, footings, and excavations. It is shown here that the same expression for mobilized undrained strength of soft clays is also obtained from laboratory shear tests by taking into account anisotropy and time effects. This result is highly significant, since the laboratory undrained shear strength data, as well as the correction factor for the time effect, are completely unrelated to the in situ data that previously resulted in the expression for field mobilized undrained shear strength. Key words: mobilized undrained shear strength, in situ vane test, laboratory shear tests.

Interpretation of field vane strength of an anisotropic soil

1992 ◽  
Vol 29 (4) ◽  
pp. 627-637
Author(s):  
Vinod K. Garga ◽  
Mahbubul A. Khan
Keyword(s):  
Shear Strength ◽  
Undrained Shear Strength ◽  
Triaxial Tests ◽  
Strength Anisotropy ◽  
Shear Tests ◽  
Direct Shear Tests ◽  
State Of Stress ◽  
Anisotropic Soil ◽  
Undrained Shear

Determination of the undrained shear strength (Su) of overconsolidated soils such as the weathered clay crust overlying Leda clay is important for the design of shallow foundations and embankments. In situ vane shear tests and isotropically consolidated undrained triaxial tests have been conventionally used for this purpose. Contrasting test results from these two methods, low Su obtained from triaxial tests and high Su obtained from in situ vane shear tests, motivated further research into this problem. Strength anisotropy, due to in situ anisotropic state of stress and orientation of soil fabric during deposition, is believed to be the reason for these contrasting results. Improved testing and interpretation techniques for this type of anisotropic soil have been proposed. Weathered crusts are generally heavily over-consolidated, with K0 values greater than unity. Undrained triaxial shear tests conducted to date by various researchers are either isotropically consolidated or are anisotropically consolidated assuming K0 smaller than unity. Neither of these two methods represents the in situ state of stress of a clay crust. Therefore, in this investigation, the undisturbed samples were reconsolidated anisotropically to the in situ state of stress (K0 > 1) before shearing undrained in the triaxial test. Direct shear tests on horizontal and vertical specimens consolidated to normal stresses equal to σvo′ and σho′, respectively, were also conducted to investigate the strength anisotropy. Field vane tests have been reinterpreted in terms of this strength anisotropy. The undrained shear strength on top and bottom horizontal planes (Suh) obtained from these field vane tests within the crust provided comparable results with those from laboratory triaxial and direct shear tests which were reconsolidated to in situ stresses. Key words : in situ vane test, undrained shear strength, strength anisotropy, rate effect, anisotropic in situ state, weathered clay crust, overconsolidation.

Reply to the discussion by Mesri and Wang on “Correlations for undrained shear strength of Finnish soft clays”

2017 ◽  
Vol 54 (5) ◽  
pp. 749-753 ◽  
Author(s):  
Marco D’Ignazio ◽  
Kok-Kwang Phoon ◽  
Siew Ann Tan ◽  
Tim Länsivaara ◽  
Suzanne Lacasse
Keyword(s):  
Shear Strength ◽  
Undrained Shear Strength ◽  
Soft Clays ◽  
Undrained Shear

scholarly journals A Random Forest Model for the Prediction of Spudcan Penetration Resistance in Stiff-Over-Soft Clays

2020 ◽  
Vol 27 (4) ◽  
pp. 130-138
Author(s):  
Pan Gao ◽  
Zhihui Liu ◽  
Ji Zeng ◽  
Yiting Zhan ◽  
Fei Wang
Keyword(s):  
Shear Strength ◽  
Random Forest ◽  
Penetration Resistance ◽  
Undrained Shear Strength ◽  
Soil Parameters ◽  
Good Prediction ◽  
Resistance Profile ◽  
Soft Clays ◽  
Centrifuge Tests ◽  
Undrained Shear

AbstractPunch-through is a major threat to the jack-up unit, especially at well sites with layered stiff-over-soft clays. A model is proposed to predict the spudcan penetration resistance in stiff-over-soft clays, based on the random forest (RF) method. The RF model was trained and tested with numerical simulation results obtained through the Finite Element model, implemented with the Coupled Eulerian Lagrangian (CEL) approach. With the proposed CEL model, the effects of the stiff layer thickness, undrained shear strength ratio, and the undrained shear strength of the soft layer on the bearing characteristics, as well as the soil failure mechanism, were numerically studied. A simplified resistance profile model of penetration in stiff-over-soft clays is proposed, divided into three sections by the peak point and the transition point. The importance of soil parameters to the penetration resistance was analysed. Then, the trained RF model was tested against the test set, showing a good prediction of the numerical cases. Finally, the trained RF was validated against centrifuge tests. The RF model successfully captured the punch-through potential, and was verified using data recorded in the field, showing advantages over the SNAME guideline. It is supposed that the trained RF model should give a good prediction of the spudcan penetration resistance profile, especially if trained with more field data.

Potential improvements of design parameters by taking block samples of soft marine Norwegian clays

2007 ◽  
Vol 44 (6) ◽  
pp. 698-716 ◽  
Author(s):  
Toralv Berre ◽  
Tom Lunne ◽  
Knut H Andersen ◽  
Stein Strandvik ◽  
Morten Sjursen
Keyword(s):  
Undrained Shear Strength ◽  
Design Parameters ◽  
Shear Tests ◽  
High Quality ◽  
Soft Clays ◽  
Direct Simple Shear ◽  
Sample Disturbance ◽  
Marine Clays ◽  
Oedometer Tests

Undrained triaxial and direct simple shear tests on samples reconsolidated to the in situ effective stresses and oedometer tests have been carried out on standard piston tube and on high quality block samples from 12 deposits of soft Norwegian marine clays. Based on the results of a selected number of these tests, empirical procedures for estimating the effect of sample disturbance have been developed. These procedures can be used to show the potential increase that may be achieved in undrained shear strength and apparent preconsolidation stress by taking high quality block samples. Suggestions are also given regarding corrections for rate of loading and temperature effects; as well, examples are given regarding possible consequences for design if higher strengths are utilized.Key words: soft clays, sample disturbance, consolidation procedures, stress–strain–strength behaviour.

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