Mathematical modelling of the mechanical response of earth embankments on piled foundations

Abstract

Piled foundations are largely employed as settlement reducers in the design of artificial embankments on soft soil strata. The commonly employed design methods are, however, based on simplified approaches not allowing the assessment of average and differential settlements at the top of the embankment. With this objective, the authors introduce a generalised constitutive relationship capable of accounting for irreversibilities stemming from both geometrical evolution and soil yielding. The model derives from the interpretation of the results of a campaign of three-dimensional elastic–plastic finite-difference numerical analyses describing the embankment construction process. Numerous simplifying assumptions (for instance smooth pile shaft, drained conditions) have been employed. Nevertheless, this does not compromise the theoretical value of the proposed approach. From a practical point of view, this model is a useful tool for geotechnical engineers to employ with a displacement-based design perspective.

A rheological model for georeinforced embankments based on piled foundations

“…According to di Prisco et al [8], the mechanical response of the system can be described by using the following non-dimensional variables: The numerical results (Figure 2) clearly show the role played by the pile: (i) the stresses c are much larger than f (Figure 2a); (ii) the vertical displacements at the top of the pile are negligible (Figure 2b) whereas the settlements at the top of the foundation soil follow a non-linear trend; (iii) when H is sufficiently large, differential settlements at the top of the embankment stop increasing reaching an asymptotic value (Figure 2c). On the top of the embankment (Figure 2c) the average and differential displacements are initially coincident.…”

“…According to di Prisco et al [8], the behaviour of a non-reinforced piled embankment can be described by means of a rheological model (Figure 4). To evaluate settlements at the top of the embankment, an incremental relationship between the generalized loading variable 𝐻 ̇ and the displacements at the top of the embankment 𝑈 ̇𝑡,𝑑𝑖𝑓𝑓 and 𝑈 ̇𝑡,𝑎𝑣 is used:…”

“…In order to take into account the effect of the geosynthetic layer below the embankment base, according to di Prisco et al [8] only the elastic spring 𝐶 2 𝑟 needs to be suitably modified with respect to the non-reinforced case [8]. In particular, the authors considered a spring whose stiffness (1/𝐶 2 𝑟 ) progressively increases with the non-dimensional displacements Ub,f.…”

“…In di Prisco et al [8] a new model to interpret the mechanical response of an unreinforced embankment on piled foundations was proposed. This model puts in relation the increment in the embankment height (employed as a generalized loading variable) with the increment of both average and differential settlements at the embankment top.…”

“…This model puts in relation the increment in the embankment height (employed as a generalized loading variable) with the increment of both average and differential settlements at the embankment top. In Mangraviti et al [5][6][7][8], the authors extended the model to the case of reinforced embankments by discussing the influence of geosynthetic stiffness (J).…”