Inserting a pressuremeter or dilatometer into sand inevitably results in significant alteration of the insitu state. However it has always been possible to work around this limitation by reversing the direction of loading having established a well-developed plastic condition. This stress reversal approach is already used to obtain high quality elastic parameters from unload/reload cycles. The same argument applies to the final cavity unloading. This makes it possible to derive sensible strength parameters from data where the influence of the insertion history has been minimised if not entirely erased.
The unloading behaviour of a sand is complex and is not amenable to approaches that impose a stress/strain response (for example Withers et al 1989) . The problem invites numerical methods. Manassero (1989) developed a relatively simple method appropriate for high quality cavity expansion tests. This solution can also be applied to cavity contraction data. The great advantage offered by the Manassero solution over other potentially more exact analyses such as Yu & Houlsby (1995) is the minimal number of assumptions. Very little additional information from third-party tests is required before the pressuremeter tests can be interpreted.
Results from the unloading of self-bored, pre-bored and pushed pressuremeter tests in various dilatant materials are presented in the form of stress/strain curves with peak shear stress and friction angle identified. It is apparent that the shear strain is different for these two events, the peak shear stress occurring when the mobilised friction has reduced to the constant volume condition. Differences between the three pressuremeter insertion methods for the purposes of deriving strength are small, with differences attributable to more extensive particle crushing with pushed methods.

The vertical axial performance of pile foundations is generally expressed in terms of settlements caused by unfactored load effects (work loads). In the settlement calculation, piles and piles groups are considered as isolated structural elements, neglecting their connection with other structural elements and the effect of the structural stiffness. This paper presents the results of a reliability analysis that considers the piles as part of a reinforced-concrete five-bay two-storey square building. The results are expressed in terms of the probability that differential settlements between piles supporting adjacent columns exceed the limiting values given in the National Building Code of Canada. As the relative stiffness increases, the probability that differential settlements exceed the code limiting value largely decrease, indicating that the settlement estimates common in current practice can severely overestimate the actual values experienced by the superstructures.

A variety of geotechnical projects are initiated with unsupported vertical cuts in vadose zone. In this case, it is crucial to consider the contribution of soil suction in analyzing the stability of unsupported vertical cuts. Soil-Water Characteristic Curve (SWCC) is a main tool that can be used to estimate the variation of shear strength of soil with respect to soil suction. SWCC can be obtained using different fitting models based on experimental data. In this study, a series of numerical analyses are carried out to investigate the influence of SWCCs obtained using different SWCC fit models (i.e. Brooks & Corey, van Genuchten, and Fredlund & Xing models) on the safe height of unsupported vertical cuts in sandy soil. The analysis results showed that the safe heights estimated with the van Genuchten model are most reasonable for various levels of ground water tables.

Beaucoup d’ouvrages de génie civil sont construits en zone non saturée. Contrairement aux sols saturés, la maîtrise de la résistance au cisaillement des sols non saturés reste encore un grand défi surtout au niveau des sols granulaires. Des essais triaxiaux consolidés drainés (CD) et à teneur en eau constante (CW) ont été réalisés afin d’examiner l’influence de la succion matricielle et du degré de saturation sur un sable et gravier concassé, compacté à sa teneur en eau optimale. Les résultats expérimentaux montrent que, pour la même succion de rupture, la résistance au cisaillement des essais non saturés CW s'avère supérieure à celle des essais non saturés CD. D’autres résultats tirés d’essais CD sur des éprouvettes à des degrés de saturation préparés par sorption présentent pour la même succion de rupture une résistance supérieure à celle mesurée sur des éprouvettes préparées par désorption. La résistance au cisaillement (ainsi que d’autres propriétés mécaniques) ne dépendrait donc pas seulement de la contrainte nette et de la succion à la rupture, mais aussi de l’historique du cheminement en teneur en eau du matériau. L’hystérésis observée chez la courbe de rétention d’eau du sable et gravier concassé se répercuterait donc sur sa résistance au cisaillement.

This paper is written in French but the presentation will be in English

This paper presents the behavior of 406 mm diameter, 12 m long, instrumented, driven steel piles at a construction site in Esbjerg, Denmark. One pile was uncoated and one was bitumen coated. The piles were driven through a 1.5 m thick layer of reclaimed sand underlain by original soil consisted of a 2.0 m thick layer of sand, a 3.6 m thick layer of soft soil above a thick sand layer. The instrumentation comprised distributed fiber optic cables. Due to its spatial resolution (2.6 mm), very detailed strain profiles were obtained. The distribution of strain in the piles was affected by, first, the pile installation, building up a residual force in the piles and, then, additional force, drag force due to negative skin friction developing after placing a 3 m thick fill around the piles. Due to construction activities an unplanned one-sided loading occurred inducing considerable bending and lateral force in the test piles.

Finite element analysis was performed to simulate the excavation of an unsupported deep vertical cut (depth = 9.75 m) in clay at Welland, Ontario (Kwan 1971). For this, SIGMA/W and SLOPE/W (GeoStudio 2019 R2) were used to simulate staged excavation and to estimate its stability, respectively. To maintain the consistency of obtained results with field conditions, the simulated excavation followed the same timeline as field excavation. There was good agreement between the measured post excavation pore-water pressure contours obtained from installed field instruments with those from the numerical modelling. The numerical analysis results also showed that the failure in the cut was attributed to a tension crack, which is consistent with field observations.