###### Abstract  
Three-dimensional finite element (FE) simulations were performed to further develop the Swedish design guidelines for geogrid-reinforced timber pile-supported embankments, also known as lightly piled embankments. Lightly piled embankments are constructed mainly in areas which typically have highly compressible soils, and the method utilises untreated timber piles as its key feature. The timber piles are installed in a triangular arrangement instead of the more common square arrangement, with a centre-to-centre distance of 0.8-1.2 m. The aim of this study was to evaluate the current standard using FE modelling setups with square and triangular pile arrangements with varying centre-to-centre distances, based on a typical road foundation case. The evaluation mainly focused on comparing the embankment settlements, as well as the load and stress distribution in the embankment, the piles and the geosynthetic reinforcement. As part of the evaluation, a state-of-the-art study was done on international design guidelines and analytical models. From the FE simulations, no evident difference in mechanical behaviour was found between the triangular and square piling patterns. The maximum allowed centre-to-centre distance between piles can potentially be increased to 1.4 m, decreasing the number of piles by as much as one third. geosynthetic-reinforced pile-supported embankments; timber piles; square grid; triangular grid; arching; FEM +
Footnote †: journal: Applied  
**Citation:** [PERSON]; [PERSON] [PERSON]; [PERSON] [PERSON] Evaluating the Design Criteria for Light Embankment Piling: Timber Piles in Road and Railway  
**Foundations. Appl. Sci. 2022,** 12, 166. [[https://doi.org/10.3390/app12010166](https://doi.org/10.3390/app12010166)]([https://doi.org/10.3390/app12010166](https://doi.org/10.3390/app12010166))  
**Citation:** [PERSON]; [PERSON] [PERSON]; [PERSON] [PERSON] Evaluating the Design Criteria for Light Embankment Piling: Timber Piles in Road and Railway  
**Foundations. Appl. Sci. 2022,** 12, 166. [[https://doi.org/10.3390/app12010166](https://doi.org/10.3390/app12010166)]([https://doi.org/10.3390/app12010166](https://doi.org/10.3390/app12010166))  
explicit standard or recommendation for GRPSE with untreated timber piles. In Indonesia, there exist guidelines for thinner timber piles (8-10 cm in diameter) or bamboo piles [4]. The aims of the main project, of which the present study is part, are to clarify the mechanical behaviour of lightly piled embankments and to create a guide for optimal design for different conditions that involve road or railway embankments on soft subsoil. The focus of this project is on Swedish conditions with soft clay or silt layers on glacial till. However, similar conditions are frequently found globally, making the results of the project applicable outside of Sweden as well. A theoretical analysis of the construction was performed based on three-dimensional (3D) finite element (FE) modelling, verified by field and laboratory experiments. The aims of the present study in this paper are: (1) to find the key mechanisms of load transfer in GRPSE; (2) to make a first evaluation of the efficiency of a triangular pile arrangement in comparison with a square pile arrangement; and (3) to evaluate appropriate centre-to-centre pile spacing. To accomplish these aims, 3D FE simulations were primarily used. The numerical results from FE simulations were compared and validated against results from analytical models. A state-of-the-art study was carried out on the mechanisms of the load transfer in GRPSE, as well as the GRPSE standards and analytical models used in practice. The FE simulations done in this study were based on a lightly piled road embankment northwest of Lulea in northern Sweden, 110 km south of the Arctic Circle. The road was initially constructed in 1993 as an unreinforced embankment and was later reinforced in 2013-2014 with timber piles and GR after it suffered from large settlements (2 m at the most).