Analyses of a pile-supported embankment over soft clay: Full-scale experiment, analytical and numerical approaches

The reinforcement of soils using rigid inclusions is a technique used to reduce settlements and to ensure the stability of an embankment built over soft soils. This technique reduces construction delays and is an economical and reliable solution, which has led to its widespread use. Thus, many design methods have been developed to assess the performance of these reinforced structures. These methods are mainly based on results from small scale models and numerical analyses. The reliability of these methods must be validated under in-situ conditions. This paper presents an analytical and numerical study of full-size experiments at the Chelles test site (France). The work presented in this paper is part of the ASIRI French National Research Project. The experiment consisted of a 5-m-high embankment built over soft alluvial ground improved by rigid vertical piles. The embankment is divided into four zones that illustrate the influence of the piles and the geosynthetic reinforcements on the soil's behavior. The performance of the embankment support system is assessed by monitoring data (total stresses, horizontal and vertical displacements). Several in-situ and laboratory soil investigations were performed using two axially loaded test piles. These tests verified the geotechnical hypothesis used for the numerical model and defined the soil–pile interaction parameters. Several analytical methods and numerical models were tested to assess the arching effect. Comparisons between the experimental data and these design methods are presented in terms of stress and the settlement efficacy of the improved system. The results show that these methods overestimate the stress efficacy but that the settlement efficacy is a reliable parameter to assess the overall performance of the rigid inclusion technique.