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The load-settlement relationship for plate loading of an isolated stone column in soft clay was predicted prior to field testing. The column was constructed by vibro-replacement and, after the test, was excavated to check its dimensions. The theory used was proposed on the basis of laboratory model tests by Hughes and Withers (1974). The purpose was to verifv the theory on a field scale. A standard site investigation supplemented by Cambridge and Ménard pressuremeter tests provided basic soil parameters. The ultimate column load depends on the friction angle of the gravel used to form the column, the size of the column formed and the restraint of the clay on the uncemented gravel. To predict the load-settlement curve the essential radial stress-strain data for the clay were obtained from a Cambridge pressuremeter. The prediction is excellent if allowance is made for transfer of load from column to clay through side shear and correct column size. Accurate estimation of column diameter is the major factor influencing the calculation of ultimate load and settlement characteristics. The column improved substantially the bearing capacity of the natural soil. La relation charge-tassement pour un essai à la plaque d'une colonne en Pierre, isolée, dans l'argile molle, a été prévue avant l'essai in situ. Suite à l'essai, la colonne construite par la méthode de vibro-remplacement, a été excavée afin de vérifier ses dimensions La théorie utilisée est à la base d'essais sur modèle de laboratoire, d'après Hughes et Withers (1974). L'objectif a été de vérifier cette théorie à l'échelle du chantier. Une reconnaissance classique du terrain, complétée par des pressiomètres de Cambridge et Ménard, ont fourni les caractéristiques du sol. La charge limite de rupture d'une colonne, dépend de l'angle de frottement du gravier qui la forme, de sa taille et de la contrainte de l'argile sur le gravier non-cimenté. Afin de prévoir la courbe de charge-tassement, l'information essentielle de contrainte-déformation, a été obtenue à l'aide du pressiomètre de Cambridge. La prévision est excellente, si l'on tient compte du transfer de la charge, de la colonne à l'argile, grâce au cisaillement latéral et la taille exacte de la colonne. Une estimation précise du diamètre de la colonne, est le facteur principal pouvant influencer le calcul de la charge de rupture et du tassement. La colonne a considérablement amélioré la force portante du sol réel.

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The nonlinear subgrade reaction method is widely used for the design of laterally loaded piles. This method replaces the soil reaction with a series of independent springs. The nonlinear behavior of the soil springs is represented by P-y curves, which relate soil reaction and pile deflection at points along the pile length. Most of the existing methods for obtaining P-y curves are highly empirical. Often little account is taken of the method of pile installation. The pressuremeter offers an almost ideal in-situ modelling tool for determining directly the P-y curves for a pile. As the pressuremeter can either be driven or self-bored into the soil, the results can be used to model either a displacement or a non-displacement pile. The driven pressuremeter used in the study described in this paper was essentially a standard pressuremeter with a solid 60° cone shoe at the tip. The instrument was pushed into the soil. This paper provides a detailed description of the equipment, testing procedures, and the theory that enables the family of P-y curves for laterally loaded displacement piles to be obtained. A case study, using the driven pressuremeter results to predict and compare the performance of two full-scale field lateral pile load tests, is presented.

A 915 mm diameter steel pipe pile was driven and tested by the B.C. Ministry of Transportation and Highways as part of their foundation studies for the proposed Annacis channel crossing of the Fraser River. The pile was driven open ended to a maximum depth of 94 m. The pile was tested axially to failure when the pile tip was at depths of 67, 78, and 94 m below ground surface. Following the final axial load test, the pile was loaded laterally to a total deflection at the ground surface of 150 mm. A slope indicator casing was installed in the pile to monitor the deflected shape during lateral loading.Adjacent to the pile, a piezometer-friction cone penetration test (CPT) and a full-displacement pressuremeter profile were made. Results of the axial and lateral load tests are presented along with the data from the CPT and the full-displacement pressuremeter tests. Results of several analyses using the data from the CPT and pressuremeter tests to predict the axial and lateral performance of the pile are presented. A comparison and discussion is presented between the predicted and measured axial and lateral behaviour of the pile, for which excellent agreement was found. Key words: pile load test, cone penetration test, pressuremeter test.