Progress in the instrumentation of model piles in geotechnical centrifuge

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4. Progress in the instrumentation of model piles in geotechnical centrifuge

In centrifuge physical modelling, the small-scale model pile is both the object of the study and a sensor by itself. With the addition of appropriate instrumentation, it can be used to measure the soil's local behaviour. By considering the pile as a beam, the horizontally loaded pile can generate P-y soil reaction curves used in its design. The model piles were first instrumented with strain gauges glued to the outside shaft of the tube. A pair of strain gauges diametrically opposed on the same section measure directly the bending moment. However, these gauges must be protected by a seal that affects the roughness of the pile, a key parameter which governs the behaviour of its interface. In some cases, the gauges can be glued inside the shaft of the tube. However, in both cases, the inside of the tube, housing wires, must be close-ended. More recently, the democratisation of optical fibres has seen instrumentation evolve. Bragg grating technology allows several strain measurements to be taken on a single fibre. This fibre, glued along the length of the pile, measures the axial deformations at different depths. The fibre, emerging above the ground level, can be used to study open-ended tubes. Several examples are presented: i) piles with several slenderness ratios, ii) monopiles driving in-flight, iii) very large monopiles, and iv) piles loaded horizontally in different directions.

5th European Conference on Physical Modelling in Geotechnics (ECPMG2024)

Keynote paper