Model experiments on piled embankments. Part I

A series of twelve 3D laboratory model tests was performed on piled embankments. In this first part of a two-part study, the measured load distribution, deformation, and strains are presented and analysed. In the second part, the measurements are compared with calculations using EBGEO (2010), and suggestions are given for improvements to this calculation model. In the test series, the vertical load parts on the piles, on the geosynthetic reinforcement (GR), and on the subsoil could be measured separately. This makes it possible to compare the test results with the separate parts of the analytical models. For the test conditions (static load, laboratory scale), smooth relationships were obtained between the net load on the fill (top load on fill minus subsoil support) and several measured parameters, such as load distribution and deformation. Consolidation of the subsoil resulted in an increasing load transferred through the GR, and also an increase of arching. The measured response to consolidation depends on the fill’s friction angle. A higher friction angle gives more arching during consolidation. Loading on the geosynthetic reinforcement is concentrated on the strips lying above and between adjacent piles (the “GR strips”). The line load on a GR strip has the distribution of an inverse triangle, although the load may be even more concentrated around the pile caps than this indicates. This follows from the measured shape of the deformed GR. A geogrid gives negligible differences in comparison with a geotextile. No difference is found between the use of a single biaxial grid layer and two uniaxial grid layers positioned directly on top of each other. Only limited differences were found between a situation with one grid layer, and one where two grid layers were used with a layer of granular material in between.