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Vibratory pile driving in water saturated sand

This application of numgeo-PFEM presents a back-analysis of a model test reported in (Vogelsang, 2017)1. The simulation reproduces vibratory pile driving in water-saturated Karlsruhe sand with an installation frequency of \(f=25\,\mathrm{Hz}\).

The model test was conducted in half of an axisymmetric test chamber with a diameter of \(d = 0.94\,\mathrm{m}\) and an acrylic glass plate at the front for visual observation. The height of the soil body was \(h = 0.81\,\mathrm{m}\) The installed pile had a diameter of \(d_{pile} = 33\,\mathrm{mm}\) and a tip angle of \(60^{\circ}\). The initial relative density of the sand was \(D_{r0} = 71\,\%\), corresponding to an initial void ratio of \(e_0 = 0.637\). Further details of the experimental setup are provided in (Vogelsang, 2017)1.

The mechanical behaviour of the Karlsruhe sand is described using the hypoplastic constitutive model (Wolffersdorff, 1996)2 with the intergranular strain extension (Niemunis and Herle, 1997)3. The material parameters were taken from (Machaček et al., 2021)4.

The back-calculated model test was carried out in half of an axisymmetric test bench with a diameter of \(d = 0.94\,\mathrm{m}\) and an acrylic glass plate at the front. The height of the soil body was \(h = 0.81\,\mathrm{m}\). The installed pile had a diameter of \(d_{pile} = 33\,\mathrm{mm}\) and a tip angle of \(60^{\circ}\). The initial relative density of the present model test was \(D_{r0} = 71\,\%\), which corresponds to an initial void ratio of \(e_0 = 0.637\). Further details on the test setup can be found in (Vogelsang, 2017)1. For the stress-strain behaviour of the Karsruhe sand the consitutive model Hypoplasticity (Machaček et al., 2021)4 with intergranular strain extenstion [] was used.

The animation below illustrates the force-driven installation process of the pile. The pulsating vertical stresses beneath the pile tip reflect the dynamic nature of the vibratory installation process. For the evaluation of the back-analysis, the simulated pile head displacement and the excess pore water pressure at the indicated measurement location are compared with the experimental observations.

For the pile head displacement, very good agreement between the simulation and experimental results is observed. For the excess pore water pressure, the general trend of the measured data is reproduced by the simulation, although the amplitude of the oscillations is underestimated. Nevertheless, considering the complexity of this dynamic hydro-mechanically coupled problem, the overall agreement can be regarded as satisfactory.

  1. Vogelsang, J. (2017) Untersuchungen zu den mechanismen der pfahlrammung. PhD thesis. Karlsruher Institut für Technologie (KIT); Karlsruher Institut für Technologie (KIT). ↩↩↩

  2. Wolffersdorff, P.-A. von (1996) "A hypoplastic relation for granular materials with a predefined limit state surface," Mechanics of Cohesive-frictional Materials, 1(3), pp. 251--271. Available at: https://doi.org/10.1002/(sici)1099-1484(199607)1:3\<251::aid-cfm13>3.0.co;2-3. ↩

  3. Niemunis, A. and Herle, I. (1997) "Hypoplastic model for cohesionless soils with elastic strain range," Mechanics of Cohesive-frictional Materials, 2(4), pp. 279--299. Available at: https://doi.org/10.1002/(sici)1099-1484(199710)2:4\<279::aid-cfm29>3.0.co;2-8. ↩

  4. Machaček, J. et al. (2021) "Investigation of three sophisticated constitutive soil models: From numerical formulations to element tests and the analysis of vibratory pile driving tests," Computers and Geotechnics, 138, p. 104276. Available at: https://doi.org/10.1016/j.compgeo.2021.104276. ↩↩