This paper presents a finite-element (FE) analysis of the effect of subsoil in a reinforced piled embankment and compares the findings with predictions from a theoretical method. It shows that the subsoil can carry as much as 75% arching embankment load for the present standard model (pile spacing of 2.5 m, geogrid stiffness of 6 MN/m, embankment height of 6 m, and subsoil compression index of 0.7). Also, the proportion is much larger for the lower value of pile spacing, geogrid stiffness, embankment height, and subsoil compression index. The maximum settlement of subsoil is found to be more sensitive to the pile spacing than to the geogrid stiffness. The theoretical method shows reasonable agreement with the FE results and can therefore be used to predict the effect of subsoil in reinforced piled embankments. The geogrid has a significant role in carrying the entire embankment load without the subsoil support. However, this effect may lead to intolerable geogrid strain due to relatively large set...

The reinforced piled embankment has been widely used in highway and high-speed railway because it is effective in reducing total and differential settlement. This paper presents an analytical solution for estimating the settlement of pile and soil and the distribution of skin friction and the neutral plane of the pile in the reinforced piled embankment over elastoplastic consolidated soil. The soft soils were assumed to be elastic-plastic materials with settlement calculations as determined by one-dimensional nonlinear consolidation theory. The load-transfer mechanisms accounting for soil arching and tensioned-membrane effects on the reinforcement and pile–soil interaction (skin friction along the pile), considering soil consolidation, were comprehensively investigated. The analytical solution was validated by three case studies and was shown to be a reliable method with acceptable accuracy with predictions overestimating the measurement by approximately 10%. The maximum settlement of soil was found to increase with increasing pile spacing while the soil constrained modulus decreased. The soil constrained modulus was a much more sensitive factor of influence on the maximum settlement of the soil than was the pile spacing.

A PVD-DCM method combined with prefabricated vertical drains (PVDs) and deep cement mixing (DCM) piles is presented in this paper based on the field case of Beijing–Shanghai high-speed railway in China. The field performance of soft soil foundation improved by this method is comprehensively analysed, and shows that the PVD-DCM method takes full advantages of PVDs and DCM piles, in which the DCM piles increase the bearing capacity and reduce the total settlement of the soft foundation, while PVDs accelerate the consolidation of the soil by shortening the drainage paths. A plane strain numerical simulation on the field case is then conducted, which is converted by a three-dimensional (3D) problem with equivalent properties and dimensions. The numerical simulation is found to be an effective method to predict the true behaviour of the foundation improved by the PVD-DCM method, such as the load transfer and settlement, with reasonable accuracy. The PVD-DCM method is finally assessed both by PVD method and DCM method in terms of the settlement, implying that the PVD-DCM method can provide an effectiveness of foundation improvement and create a more economical solution.

This paper develops rigorous lower-bound shakedown solutions for pavement structures subjected to Hertz loads both in plane strain and three-dimensional (3D) models. Firstly, a necessary shakedown condition is derived based on Melan’s shakedown theorem and the use of Prandtl–Reuss theory in conjunction with von Mises criterion, which gives a maximum value to the rigorous shakedown limit. Secondly, the rigorous lower-bound shakedown solution is established uses a self-equilibrated critical residual stress field with an optimisation procedure. As expected, the necessary shakedown condition gives larger values of normalised shakedown limits than that of the normalised rigorous lower-bound shakedown solution, with the maximum difference of 93%. Also observed is that the 3D model always overestimates the normalised rigorous shakedown limits of the plane strain model by approximately 8–13%, while the two models capture approximately the same trend of normalised rigorous shakedown limits varied with frictional coefficient. Finally, the parametric studies on normalised rigorous shakedown limit of pavements in terms of frictional coefficient and Poisson’s ratio are performed. It shows that the normalised rigorous shakedown limits are proportional to material yield stress but decrease markedly with raising frictional coefficient; while the effect of the Poisson’s ratio on normalised rigorous shakedown limits is marginally. In addition, the critical residual stress fields lie between two residual stress limits, which intersect beneath the surface for small μ, while tend to converge at the half-space surface when μ = 0.3, indicating that the failure mode of the pavement changes from subsurface failure to surface failure when increasing the frictional coefficient μ. As a result, the present shakedown solutions can provide reference to the design of pavements subjected to rolling and sliding loading contact.