Effects of Disturbance on Undrained Strengths Interpreted from Pressuremeter Tests

Aubeny, Charles; Whittle, Andrew J.; Ladd, Charles C.

doi:10.1061/(asce)1090-0241(2000)126:12(1133)

Cited by 19 publications

(13 citation statements)

References 26 publications

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“…The soil response can take place in drained conditions with dissipation of interstitial pressures or in undrained conditions (Aubeny et al 2000;Benoit 1995).…”

Section: Undrained Responsementioning

confidence: 99%

Interpretation of the pressuremeter test using numerical models based on deformation tensor equations

Sánchez

Aguado²,

Lavín

2013

Bull Eng Geol Environ

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The pressuremeter test in boreholes has proven itself as a useful tool in geotechnical explorations, especially comparing its results with those obtained from a mathematical model ruled by a soil representative constitutive equation. The numerical model shown in this paper is aimed to be the reference framework for the interpretation of this test. The model analyses variables such as: the type of response, the initial state, the drainage regime and the constitutive equations. It is a model of finite elements able to work with a mesh without deformation or one adapted to it.

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“…The soil response can take place in drained conditions with dissipation of interstitial pressures or in undrained conditions (Aubeny et al 2000;Benoit 1995).…”

Section: Undrained Responsementioning

confidence: 99%

Interpretation of the pressuremeter test using numerical models based on deformation tensor equations

Sánchez

Aguado²,

Lavín

2013

Bull Eng Geol Environ

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“…Therefore this interpretation method would inevitably lead to errors in derived soil properties (e.g. References [6][7][8][9][10][11][12][13][14] among many others). Most recently, Yu [15] has carried out a rather comprehensive review of various sources of inaccuracy due to these simplifying assumptions.…”

Section: Introductionmentioning

confidence: 99%

Analysis of pressuremeter geometry effects in clay using critical state models

Charles

Khong

2005

Num Anal Meth Geomechanics

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SUMMARYThe conventional interpretation methods of pressuremeter testing effectively approximate pressuremeter membranes as infinitely long. As a result, the effects of the two-dimensional geometry of pressuremeters are ignored, leading to an overestimation of soil shear strength by pressuremeter testing, as demonstrated in several previous studies. This paper presents results of a numerical study of two-dimensional geometry effects on self-boring pressuremeter tests in undrained clay. The results are obtained using critical state soil models with an effective stress formulation. This is in contrast to most (if not all) existing studies on pressuremeter geometry effects, which were based on perfectly plastic soil models (e.g. Yu (Cavity expansion theory and its application to the analysis of pressuremeters. DPhil Thesis, The University of Oxford, 1990), Yeung and Carter (Proc. 3rd Int. Symp. on Pressuremeters, 1990), and Houlsby and Carter (Ge´otechnique, 1993; 43 (4):567-576)). The present study suggests that the overestimation of soil strength due to the neglect of finite pressuremeter length is significantly affected by the soil model used in the calculations. It is found that for clays with a high overconsolidation ratio (OCR) the strength overestimation predicted using critical state soil models could be considerably smaller than that predicted using perfectly plastic soil models. The main conclusion of this numerical study is that care must be exercised before directly applying any numerically determined pressuremeter geometry correction factors in practice.

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“…Various reasons have been invoked to account for such discrepancies. The most important ones are thought to be strain rate, reduced probe length, and initial borehole disturbance (Prévost 1976;Eden 1980, 1985;Prapaharan et al 1989Prapaharan et al , 1990; Whittle and Aubeny 1992;Houlsby and Carter 1993;Benoît 1995;Jefferies and Shuttle 1995;Aubeny et al 2000). As for sand, Fahey and Randolph (1984) showed that determinations of the shear modulus, measured from the initial elastic part of the test, are associated with difficulties due to the disturbance and its effects on the interpretation of the test data.…”

Section: Introductionmentioning

confidence: 99%

“…It thus seems difficult in practice to start the expansion test at the ideal undisturbed state, p o h o = σ , ε oi = 0. Indirect support for such an assertion is found in the analysis of available experimental data (see, for example, Baguelin et al 1978;Lacasse et al 1981Lacasse et al , 1990Jamiolkowski et al 1985;Benoît and Clough 1986;Aubeny et al 2000), which indicate that most shear stress -strain curves determined from pressuremeter tests exhibit (i) strain-softening characteristics, and (ii) higher shear strengths than those obtained from laboratory or field vane test results, or both. Although rate-sensitive clays are expected to exhibit strain-softening characteristics (Prévost 1976), rate effects are much less important than previously thought (Prapaharan et al 1989).…”

Section: Introductionmentioning

confidence: 99%

“…Their results indicate that the error in the undrained shear strength due to initial unloading can be higher than that due to the remoulded zone. Recently, analytical studies by Whittle and Aubeny (1992) and Aubeny et al (2000) showed that disturbance induced even during ideal self-boring (i.e., where the volume of the soil extracted exactly balances the volume of the soil displaced by the device) causes a reduction in lift-off pressure and excessive derived peak shear strengths with postpeak strain softening that are incompatible with the behaviour of the intact clay. These investigators also found that the predicted effect of increasing the ratio of the diameter of the cutting shoe relative to that of the pressuremeter membrane was in qualitative agreement with field studies indicating that increasing this ratio decreases the lift-off pressure and increases the derived shear strength Eden 1980, 1985;Benoît and Clough 1986).…”

Section: Introductionmentioning

confidence: 99%

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Disturbance effects in pressuremeter tests in clay

Silvestri¹

2004

Can. Geotech. J.

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This paper analyzes the effect of borehole disturbance, caused by installation of pressuremeter probes in clays, on the derived stress-strain curves. Both overpushing-and overcutting-induced disturbances are considered. It is shown that overpushing results in underestimation of the undrained shear resistance. In general, the degree of underestimation cannot be determined. As for overcutting, the derived stress-strain curves are characterized by high peak strengths. The degree of overestimation of the undrained shear strength may reach 100% for the case of a strainhardening material. Determination of the strain that corresponds to the peak shear strength allows determination of the true stress-strain curve from the expansion test. Analysis of four well-documented case histories serves to illustrate the proposed approach.

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Effects of Disturbance on Undrained Strengths Interpreted from Pressuremeter Tests

Cited by 19 publications

References 26 publications

Interpretation of the pressuremeter test using numerical models based on deformation tensor equations

Interpretation of the pressuremeter test using numerical models based on deformation tensor equations

Analysis of pressuremeter geometry effects in clay using critical state models

Disturbance effects in pressuremeter tests in clay

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