Kinematics of soil arching in piled embankments

Abstract

The transfer of embankment stresses towards pile heads in piled embankments is attributed to the mechanism known as soil arching. Three-dimensional physical models of piled embankments were built to simulate this mechanism. The progressive settlement of subsoil beneath an embankment was modelled and paused at increments of displacements to allow synchrotron X-ray computed tomography to be performed on the models. Image correlation techniques were then applied to the reconstructed volumes to obtain evolving three-dimensional displacement and strain fields. The strain fields show localised (shear bands) and diffuse failure modes occurring above pile heads within the embankment fill. These failure surfaces are seen to progressively develop as the subsoil undergoes settlement. The displacement fields also show the formation of a plane of equal settlement developing at a height above the pile heads, known as the critical height. The critical height is dependent on the height at which the failure surfaces propagate into the embankment fill, and a method is proposed to calculate the maximum height of failure surfaces based on the observed kinematics. The full-field kinematics provide fundamental insight into the soil arching mechanism that develops within piled embankments.

Numerical simulation of the progressive development of soil arching in column-supported embankments

“…However, the progressive development of the arching mechanism was not the focus of either study. Badakhshan et al (2020) were able to demonstrate reasonable agreement to the experimental study reported by King et al (2019b). However, their work did not expand the understanding of soil arching, and the load-displacement curve presented was not verified against experimental data.…”

“…The nature of the shear bands observed was akin to an inverted general bearing failure (Figure 3). This analogy assisted King et al (2019b) in explaining the four phases of soil arching behaviour described by Iglesia et al (1999):…”

“…These models are unable to simulate strain softening and the associated variation in dilatancy with increasing plastic shear strains. These behaviours are often relied upon to explain the results of physical tests (King et al 2019b).…”

“…The range of experiments undertaken and available measurements from the 1g bench-scale study by King et al (2019b) are briefly summarised in Table Table 1. The high-resolution X-Ray computed tomography (CT) imaging taken during the experiment provided information regarding the soil kinematics for validation against the numerical simulations.…”

“…The empirical equations from the Iglesia et al (1999) GRC were extended to GRCSEs by King et al (2017b) and used to describe the progressive soil-arching development in GRCSEs in a field case study in Melbourne, Australia (King et al 2017a). New insight into the D r a f t kinematics of soil arching was also offered by the imaging of bench-scale column supported embankment tests by King et al (2019b). For dense sand, two shear bands were seen to develop and propagate from the edge of each column head.…”