Self‐Boring Pressuremeter Tests In Soft Clay

Benoît, Jean; Clough, G. Wayne

doi:10.1061/(asce)0733-9410(1986)112:1(60)

Cited by 25 publications

(21 citation statements)

References 6 publications

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“…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: Introductionsupporting

confidence: 57%

“…This strain induces significant shear stresses before the start of the test. For the case of the self-boring pressuremeter (SBPM), the situation is improved, but either overpushing with an initial outward radial strain ε oi > 0 (Jefferies and Shuttle 1995) or overcutting with an initial inward radial strain ε oi < 0 Benoît and Clough 1986) may occur due to the installation of the pressuremeter. This will take place despite technical improvements such as the use of jetting (Benoît 1995) to increase the efficiency of the installation procedure.…”

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%

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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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Section: Introductionsupporting

confidence: 57%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Disturbance effects in pressuremeter tests in clay

Silvestri¹

2004

Can. Geotech. J.

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“…Twenty tests were carried out at Pease AFB using the cutting technique, and results from previous investigations at Hamilton AFB using cutting (Denby 1978;Benoit 1983) were used in this study. Pushin-type pressuremeter tests were also conducted at both sites for comparisons.…”

Section: Introductionmentioning

confidence: 99%

“…The ability of the SBPM to accurately measure the in situ horizontal stress is well documented (Lacasse, 1986;Benoit Can. Geotech.…”

Section: Introductionmentioning

confidence: 99%

Evaluation of jetting insertion for the self-boring pressuremeter

Benoît¹,

Atwood²,

Findlay³

et al. 1995

Can. Geotech. J.

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The primary objectives of the self-boring pressuremeter (SPBM) test are to measure, in situ, the horizontal stress and the stress-strain characteristics of soils and soft rocks. This cylindrical probe tunnels itself into the ground with a minimum disturbance. Conventionally, the advance has been performed using a cutter system housed inside a cutting shoe. Although proven effective, this method is slow and cumbersome. In response to these drawbacks, a jetting insertion method was introduced and designed to allow a faster rate of insertion using a system that is less equipment intensive and easily adapted to conventional drill rigs. To avoid similar potential inconsistencies encountered in earlier SBPM testing with the cutting method, a series of laboratory simulation tests and in situ self-boring pressuremeter tests were carried out in two soft clay deposits to assess the jetting method. The following key insertion parameters were studied: jetting nozzle type, drilling fluid velocity, jetting nozzle position, rate of advance, and jetting flushing system. The results of this study indicate that, as with the cutting method, the jetting method can be used in soft to medium clays to advance the self-boring pressuremeter with minimum disturbance.Resume : Les principaux objectifs de I'essai au pressiombtre autoforeur (PAF) sont de mesurer in situ la contrainte horizontale et les caractCristiques contrainte-dCformation des sols et des roches molles. Cette sonde cylindrique se creuse un tunnel dans le sol avec un minimum de remaniement. Dans la mCthode conventionnelle, l'avance progresse au moyen d'une trousse coupante IocalisCe dans le sabot. Quoiqu'elle ait fait ses preuves, cette mCthode est lente et encombrante. Pour Cviter ces inconvknients, I'on a introduit une mCthode d'insertion B jet consue pour permettre une vitesse d'insertion plus ClevCe et faisant appel B un systbme requCrant moins d'Cquipement et qui est facilement adaptable aux foreuses conventionnelles. Pour Cviter des inconsistances potentielles semblables B celles rencontries dans les essais antCrieurs faits au PAF avec la mCthode de tranche coupante, une sCrie d'essais de simulation en laboratoire et d'essais in situ au pressiombtre autoforeur a CtC rCalisCe dans deux dCp6ts d'argile molle pour Cvaluer la mCthode B jet. Les parambtres clCs d'insertion suivants ont CtC CtudiCs : type d'ajutage du jet, vClocitC du fluide de forage, position de l'ajutage du jet, vitesse d'avancement et systbme d'Cvacuation du fluide du jet. Les rCsultats de cette Ctude indiquent que, comme avec la mCthode B trousse coupante, la mCthode B jet peut Ctre utilisCe d a m les argiles molles B moyennement molles pour faire avancer le pressiombtre autoforeur avec un minimum de remaniement.

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Computer‐aided calibration of a soil plasticity model

Anandarajah

Agarwal

1991

Num Anal Meth Geomechanics

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A non-linear optimization technique based on the quasi-Newton approach is employed to back-calculate certain model parameters of a simple. bounding surface, soil plasticity model from in situ pressuremeter data.The theoretical response corresponding to a given set of parameters is generated by finite element analysis. A semi-analytical procedure is developed for the accurate and efficient evaluation of the gradient of objective function with respect to the model parameters of interest. The BFGS update is used to update the Hessian. Results of a series of numerical experimentation using artificial pressuremeter responses is first reported and discussed. A set of laboratory cavity expansion data is then used to calibrate the constitutive model. Associate Professor Former Graduate Student 0363-906 1/91/120835-225 1 1 .oO 0 1991

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Self‐Boring Pressuremeter Tests In Soft Clay

Cited by 25 publications

References 6 publications

Disturbance effects in pressuremeter tests in clay

Disturbance effects in pressuremeter tests in clay

Evaluation of jetting insertion for the self-boring pressuremeter

Computer‐aided calibration of a soil plasticity model

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