Arching in basal reinforced piled embankments - Validation of the concentric arches model

Arching in basal reinforced piled embankments - Validation of the concentric arches model

Van der Peet, T.C.

Van Tol, A.F. (mentor)
Van Eekelen, S.J.M. (mentor)
Van Duijnen, P.G. (mentor)
Brinkgreve, R.B.J. (mentor)
Bakker, K.J. (mentor)

Civil Engineering and Geosciences

Geoscience and Engineering

Section Geo-Engineering

2014-04-25

Infrastructural projects such as roads and railway tracks are usually built on an embankment of sand or granular material. When building on soft soils, the prevention of differential settlements and resulting damage is traditionally done by including a long consolidation period in the construction process. One method to decrease construction time is to use a pile foundation beneath the embankment. If a geosynthetic reinforcement layer (GR) is used in the base of the embankment, the construction is called a basal reinforced piled embankment. Because of the friction within the fill, the piles do not only carry the weight of the soil directly on top of them, but also part of the load above the field between the piles. This effect, called arching, is increased by the use of a GR. Furthermore, the GR itself transfers additional load to the pile. Only the residual load is now carried by the soft subsoil. Thus three load parts can be defined: arching A, GR load B and subsoil support C. The better the amount of arching can be determined, the more economically can the embankment and GR be designed. This thesis uses numerical analysis to validate a new arching model, the concentric arches model by Van Eekelen et al. (2013). First, a numerical model is designed and validated using measurements done in a scaled laboratory test and measurements done in a full-scale field situation. Then, parameters in the validated numerical model are varied and the results are compared to predictions of the concentric arches model as well as two other models that are currently in use, the Hewlett and Randolph (1988) model and the Zaeske (2001) model The numerical calculations and the predictions of the concentric arches method show strong similarities, especially for higher top loads and when the influence of the fill’s friction angle is of importance. The concentric arches model performs better in this respect than the Hewlett and Randolph model and qualitatively similar to the Zaeske model. Special consideration is given to the design of low embankment, in which full arches cannot develop. This occurrence of partial arching is mainly of importance during construction. The numerical model shows that the shape of the arches changes in these cases compared to higher embankments. This is not what is assumed in the concentric arches model, which models arches of the same shape, but limited to a smaller surface than in higher embankments. Both these phenomena however have similar effect on the amount of arching, which means the concentric arches model gives very satisfactory results for low embankment heights as well.

Arching
Piled embankment
Geosynthetic reinforcement
3D Numerical modelling

http://resolver.tudelft.nl/uuid:227ae6ce-cdbc-4ceb-b651-4b21dfa893ef

Student theses

master thesis

(c) 2014 Van der Peet, T.C.