Effects of Displacement Piles for Dike Reinforcement on Adjacent Buildings.

Abstract

This study presents a comprehensive numerical investigation into the use of displacement piles as a reinforcement measure for river dikes founded on soft soil, with a particular focus on geotechnical performance, macro stability, and impacts on nearby buildings. A finite element model is developed using parameters derived from a representative Dutch dike case (Bergambacht), incorporating the Hardening Soil, Soft Soil Creep and NGI-ADP-SHANSEP models to capture soil behaviour. Pile installation is simulated through the application of lateral volumetric strain, with varying pile diameters, spacings, and locations within the dike profile. The equivalent diameters used in the analysis range from 10 to 40 cm, corresponding to pile walls with diameters between 25.5 and 100 cm when the spacing equals the diameter. The pile wall location varies from the dike toe up to 21 m away, which is at the outer crest, with a varied length reaching -12 m NAP. A two-storey building on deep pile foundations is included to assess the effect of installation-induced displacements, with its location ranging from 5 to 20 m from the dike toe. Results show that positioning the pile wall within the inner slope offers the best balance between increased factor of safety, reduced required pile length, and acceptable levels of deformation. However, the installation process can generate significant horizontal displacements, particularly near the dike toe, which may compromise adjacent structures. The study finds that displacement piles are unsuitable within 10-15 m of existing buildings unless smaller pile diameters or alternative installation methods are used. Soil stiffness and installation-induced stresses also play a key role, highlighting the importance of site-specific assessments and careful design calibration using field data.