Pile-supported embankments on soft soil are currently reinforced by geosynthetics. Many analytical methods have been developed to design geosynthetics, but they are simplistic and do not consider all of the complexity of the developed mechanisms. Despite all of the difficulties met when simulating the behavior of pile-supported embankments in a laboratory, it has been shown that 1 g physical modeling tests can help in understanding this behavior. A new small-scale model is developed to reproduce the behavior of a pile-supported embankment at a scale of 1/10. A study is conducted to find and qualify a foam simulating the behavior of soft soil. The first tests validate the ability of the device to simulate the behavior of a pile-supported embankment correctly. The numerical procedure could also be used to define the load distribution mechanism in geosynthetic pile-supported embankment. Accurate reproduction of stress mechanisms in pile-supported systems requires strict experimental control. Laboratory tests revealed edge and toe stress concentrations, while numerical simulations showed an inverse distribution. These results underscore the necessity of isolating the central grid and realistically modeling soft soil behavior.

A series of full-scale static loading tests on square footings supported by rigid inclusions was conducted as part of the French research project ASIRI+. The primary objective of these experiments was to evaluate the impact of a load transfer platform (LTP) between the shallow foundation and rigid inclusions on the performance of the footing and enhanced soil. To achieve this, various loading configurations were examined, including vertical loading with and without eccentricity, as well as horizontal loading, across different structural scenarios—shallow foundations on soil, shallow foundations on reinforced soil with or without a load transfer platform, and rigid inclusions. The comprehensive data obtained from these experiments contribute to a deeper understanding of the load transfer mechanisms in reinforced soil, elucidating the function of each component and facilitating the calibration of numerical models.

Rammed earth is a sustainable construction material that aligns with circular-economy principles, as soil is taken from excavation and reused to build earthen structures. Evaluating and improving compressive strength is essential to ensure structural stability. An Apollonian Packing (AP) mathematical model is applied to regulate the arrangement and size of particles to match a specified geomatric fractal dimension (Df).Compressive specimens were prepared using particle size distributions based on Apollonian Packing and compared with specimens made from naturally graded soils. Experimental results showed that specimens with Df=2.75 exhibited compressive strength approximately 18% higher than those with Df=2.5. In addition, AP specimens demonstrated improved repeatability and reduced mechanical variability. Specimens produced from three different natural soils showed similar compressive strength values for the same Df, indicating that mechanical behavior is governed primarily by particle size distribution rather than mineralogical composition under dry condition.The results were further analyzed using a machine-learning approach based on an artificial neural network multi-layer perceptron model. The model successfully captured interactions between microstructural descriptors and accurately predicted compressive strength for soil specimens, achieving a mean absolute error of 0.014 MPa.This study combines fractal-based Apollonian Packing with machine learning to enhance the strength and reliability of rammed earth structures, resulting in a transferable and soil-independent predictive framework.

This paper presents laboratory tests examining geosynthetic-reinforced pile supported-embankments over soft soil. Many tests were carried out in a 4m x 4m x 0.9m pit including 16 piles, varying the load transfer platform thickness and geosynthetic reinforcement. A comprehensive monitoring program was implemented to track the load transfer inside the granular platform and the settlement. This research is a part of the cooperative national research project ASIRI+ (2019 - 2024) which gathers about forty organizations and aims to propose dimensioning rules in the field of soil reinforcement by rigid inclusions. These experimental results investigated the understanding of complex mechanisms developed inside the load transfer platform to evaluate the efficiency of the geosynthetic. In addition, a numerical model established by the software FLAC3D was employed to simulate the experimental tests. The ability of the numerical model to account for the settlement of the granular soil surface and the stress transmitted to the top of the subgrade layer was established by comparisons with the experimental data. From this calibrated numerical model, many simulations were performed to propose an optimal solution for the reinforcement by the geosynthetic.

Building roads or platforms on weak soil is a remaining challenge. The reduction of granular material required for the subbase is more and more crucial, for cost reasons but also for a much lower impact of the earthworks on the environment. Geosynthetics have proved that they offer an effective and efficient solution. Design methods using geosynthetics have been developed for subbase stabilisation but may strongly differ depending on the model and the calibration behind. An experimental study, completed by numerical modelling has been carried out to understand better the behaviour of geosynthetic at the base of a granular layer on a weak soil.

Due to the unclear mechanisms behind tunneling-induced deformation of pile-raft foundations, there are strict global restrictions on tunneling beneath embankments of high-speed railways. This study conducted a series of two-dimensional tunneling model tests to investigate the tunneling-induced deformation characteristics and mechanisms of pile-raft foundations. Soil displacement field and pile settlement were measured using particle image velocimetry and displacement transducers. The changes in soil displacement and the flexure of the pile-raft foundation in response to varying tunnel-pile distances, ground surface loads, and tunnel volume loss were analyzed. The results indicate that the tunneling-disturbed zone can be categorized into a loosened zone and an arch zone as identified by the propagation and separation of shear bands, with significant soil settlement occurring in the loosened zone. The maximum settlement of piles in a pile-raft foundation is greater than that in greenfield due to the larger loosened zone. However, the settlement width at the ground surface in pile-raft foundations is reduced due to the blocking effect of the piles. According to the relative position between the piles and the formed arch structure, three patterns of tunneling-ground-pile systems can be identified. As the tunnel-pile distance increases, the maximum settlement of the piles decreases. Increasing surface loads hardly affects the maximum settlement value of the pile, while the tunneling-induced arch zone expands significantly. This study provides a fundamental understanding of pile settlement behavior for tunneling beneath the pile-raft foundations of high-speed railways.

Rigid inclusion (RI) is a ground improvement method that has undergone significant development in recent years. Granular load transfer platforms (LTPs) are commonly used in this technique, leading to an increase in the use of natural resources. In this context, soil treatment can be considered as an alternative solution to limit pressure on granular material resources. As part of the national ASIRI+ (soil improvement using RIs) project, two full-scale tests were conducted to test the efficiency of a treated LTP on RI (with and without a working platform). Settlement and stress sensors were installed and indicated that the load transfer was immediate with a treated LTP, unlike with a granular LTP, where they were more gradual. The results indicated that the treated LTP behaved as a rigid slab with two failure mechanisms observed: punching shear and flexural failure. Numerical simulation tests were also performed, and a parametric study was conducted to assess the effect of various parameters on the system efficiency. Stress diffusion within the treated LTP was assimilated to a truncated cone, originating from the head of the RI and forming an angle φ (friction angle of the treated LTP) with the vertical.

Currently, geosynthetics are used to reinforce pile-supported embankments in soft soils. Geosynthetics are widely used to reinforce pile-supported embankments in soft soils. Numerous studies have examined various factors affecting load distribution, including pile group arrangement, the presence of pile caps, and the type and placement of the geosynthetic layer within the Load Transfer Platform (LTP). In such foundations, the primary concern is the distribution of load among the main structural components. Based on guidelines, the load is divided into three parts: the part which is directed to piles, the part which is transmitted to geosynthetic, and the part which is entered into soft soil. The soil arching and membrane effects are two effective phenomena in the load distribution process. In this study, the experimental results showed the increase in the load transferred on piles with geosynthetic and the geosynthetic focused the load on piles through the membrane effect, as confirmed by the numerical model.

The French national project ASIRI+ (2019-2025) is the continuation of the ASIRI project (2005-2012). It aims to provide design recommendations for ground reinforced by rigid inclusions, which, in France, are typically based on the analysis of a unit cell accounting for the behavior of an infinite inclusion group. These so-called “biphasic models” provide all the necessary components for the structural design of rigid inclusions. New topics are introduced in ASIRI+ project, such as horizontal reinforcement of the granular platform using geosynthetics which permits the improvement of the performance of the load transfer platform. In this framework, this paper presents a simplified analytical method that incorporates geogrids into biphasic models. At the level of geosynthetics, which transfers the load to the tops of the inclusions, a relationship coupling the geosynthetic displacement with this load is introduced into the biphasic model equations. The results obtained using this methodology are compared to full-scale tests conducted by the laboratory GEOMAS and the CEREMA of Rouen.

Pile-supported embankments require a load transfer platform (LTP) between the piles and the embankment. Granular platforms are typically reinforced using one or more geosynthetics. As part of the French research project ASIRI+, we performed laboratory tests to evaluate the performance of different types of granular LTPs. These tests were configured to ensure accurate simulation of the behavior of soft soil reinforced with rigid inclusions on a real-world scale. Our results revealed that the load transfer efficiency of geosynthetics is maximum when they are placed directly on the pile head (+30% of stress transferred to the pile compared to the non-reinforced case), the type of geosynthetic does not affect efficiency, and geosynthetics cannot significantly reduce the settlement at the pile head level for small settlement of soft soil but play their role through membrane effect for large displacement.

In Europe, the development of the wind energy market will evolve between 2020 and 2030 towards a renewal of existing wind farms to reach the objectives set by the law on energy transition for green growth. This renewal process involves the replacement of wind turbines after their service lives by more powerful machines, which would necessitate reconstruction of new foundations to accept the loads of the larger turbine. To reduce environmental impacts and limit greenhouse gas emissions, this practice appears to be far from optimal. This paper therefore focuses on assessing the suitability of a 1g small-scale model as a tool to support an evolutionary design enabling reuse of existing foundations during repowering. As part of the FEDRE research project, the study evaluates the model’s ability to simulate foundation behavior under quasi-static loading. The broader methodology integrates field monitoring, small-scale testing, and COMSOL Multiphysics® simulations to assess the feasibility of reuse before proposing practical solutions.

Rigid inclusion (RI) is a ground improvement technique that has been significantly developed in recent years. Granular load transfer platforms (LTP) are commonly used in this technique leading to an increase in the use of natural resources. In this context, soil treatment can be considered as an alternative solution to use the in-situ soil, improve its characteristics and limit the pressure on the granular material resources. As part of the national ASIRI+ project, two full-scale tests were carried out to test the behaviour of treated LTP (with and without a working platform) on rigid inclusions. An experimental program was conducted to fully characterize the soil and find the best treatment for the LTP with consideration for the environmental and economic effects. Then, the tests were carried out in an 8m x 8m pit with 16 rigid inclusions of 30 cm diameter and 1 m height. Settlement and stress sensors were installed to monitor the load transfer mechanisms within the treated platform. The instrumentation allowed us to highlight the load transfer mechanisms within the treated LTP and the negative friction along the RI. It showed that the load transfer was immediate in the case of a treated LTP unlike in the case of a granular LTP where the load transfer mechanisms were slightly more gradual. The results indicated that the treated LTP behaved like a rigid slab with two failure mechanisms observed: punching shear (test 1: without a working platform) and bending failure (test 2: including a working platform).

In any high-rise building construction based on piles, it is essential to correctly evaluate their response when subject to high loads to avoid oversizing and consequently high costs. This work falls within the framework of the FONDASILEX project, which studies the behaviour of the pile foundations and the soil within the 'Silex2' tower project built in the Part-Dieu district in Lyon, France. This paper presents the geotechnical instrumentation executed for the foundations and the soil to enable the real-time monitoring of their behaviour. It details its conception, execution and limits. Five different types of electrical and unconventional sensors, including the fibre optic technique, which is based on reflectometry by Rayleigh scattering, were employed. This instrumentation allowed us to measure the soil settlement, the applied load at the head of the pile and the induced deformation in the concrete. The obtained measurements showed good agreement between all the sensors and were compatible with the real applied load. The results of this monitoring completed with an additional specific study to characterize the soil will be used in a future study to calibrate numerical models simulating the behaviour of high-rise building foundations.

The use of reinforcement geosynthetics to prevent localized cavity collapses is now relatively common. The communication presents a monitoring solution developed as part of the REGIC research project (Reinforcement using Intelligent Geosynthetic over Natural or Anthropogenic Cavities). It is based on an innovative bi-stiffness instrumented geosynthetic and its integrated autonomous acquisition system, specially designed for use by a non-specialist. Suitable for mitigation and management of the risk of localized collapse, it allows early detection of the development of the collapse phenomenon.

A full-scale experimental geosynthetic-reinforced piled embankment (GRPE) and its numerical back analysis are presented in this article. The site is in Virv & eacute;e (France) and is part of the new South Europe Atlantic high-speed line project. A GRPE system using geosynthetics with high tensile stiffness (>= 10,000 kN/m) was proposed as an optimized solution to replace a classical pile-supported embankment (PE). Based on full-scale tests, three-dimensional finite-element models are considered to simulate both GRPE and PE solutions. The numerical results obtained are presented in comparison with in situ measurements. Settlements, pile stresses, and the geosynthetic strains are investigated. Then, a parametric study was conducted for the GRPE system to evaluate the influences of pile net spacing, geogrid tensile stiffness, and different numbers of high to relatively low tensile stiffness geosynthetic layers on the load transfer performance. The results show that the geosynthetic number of layers has less impact for the high tensile stiffness cases on the system settlement and load transfer efficiency. The use of a double-layer geosynthetic reinforcement with high tensile stiffness enhances the overall performance of the geosynthetic-reinforced piled embankment.

The French national project ASIRI+ (2019–2024) is the extension of the ASIRI project (2005–2012) and aims to update previous recommendations for the design of soil reinforced by rigid inclusions. This project ( https://asiriplus.fr/ ) mobilized forty-three partners (practitioners and academics) to act for a better understanding of the behavior of the composite foundation that is a soft soil reinforced with vertical rigid inclusions with a load transfer platform on top of it. This load transfer platform is a very important component of the system and the efficiency of this technique depends on the quality of this platform. Two types of platforms can be installed on rigid inclusions: granular platform reinforced or not by geosynthetics and soil treated platform. Specific studies consisting of full-scale experimentations, centrifugation tests, and numerical simulations were carried out to analyze the mechanisms developed within these platforms and propose implementation rules and design methods according to the type of loading applied (static loads, traffic loads, etc.). This paper focuses on load transfer platform under static load. This paper presents an experimental study on load transfer platforms in pile-supported embankments.