SummaryStiffened deep mixed (SDM) column is a new ground improvement technique to improve soft soil, which can be used to increase bearing capacity, reduce deformation, and enhance stability of soft soil. This technique has been successfully adopted to support the highway and railway embankments over soft soils in China and other countries. However, there have been limited investigations on its consolidation under embankment loading. This paper developed an analytical solution for the consolidation of embankment over soft soil with SDM column in which core pile is equal to or shorter than outer DM column. The consolidation problem was simplified as a consolidation of composite soil considering the load shear effect of core pile. The developed solution was verified by a comparison with the results computed by three‐dimensional (3‐D) finite element analysis. A parametric study based on the derived solution was conducted to investigate influence factors—length of core pile, diameter of core pile, diameter of SDM column, modulus of DM column, and permeability coefficient of DM column—on the consolidation behavior of SDM column‐supported embankment over soft soil. The developed solution was applied to a case history of SDM column‐supported embankment, and a good agreement was found between the predictions and the field measurements.

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Cement-based lightweight materials have received much attention recently in embankment backfill applications, the boundary of which is more close to a plane strain condition. To study the influence of plane strain condition on the behavior and void structure of cement-based lightweight material under cyclic loading, this paper conducted a series of compression tests on foamed cement pastes with densities of 700 and 900 kg/m3 subjected to static and cyclic loading under plane strain conditions. The X-CT technique was adopted to obtain the three-dimensional (3-D) void structures of the specimens before and after the loading tests. The results showed that the plane strain conditions yielded specimen compression strengths 30–50% higher than the unconfined conditions. The specimen integrity endured under load levels of less than 0.5, but failed after approximately 1000 cycles under a load level of 0.8, indicating that cyclic loading could accelerate the degradation of the specimena. The void structures of the specimens showed that the void volumes were featured bfatured an unimodal distribution with unimodal positions in a range of 0.1–0.2 mm3. The unimodal position became higher with the increasing cyclic load level. Slices of the specimens after static and cyclic loading tests suggested that cyclic load could easily lead to the rupture of voids that then merge into bigger voids and the connection of voids forming cracks.

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A concrete-cored gravel (CCG) column is composed of a precast concrete pile inserted at the center of sand or gravel materials. This technique has been experimentally adopted to support the soft soils in China. However, there has been limited investigation on the consolidation characteristics of a CCG column improved foundation under embankment loading. This study develops analytical solutions for the consolidation of a composite foundation partially penetrated by the CCG columns. The rigid pile's upward and downward piercing effects were considered to improve CCG column-soil equal strain relationship. The partially penetrated consolidation problem was addressed by assuming the seepages in the unpenetrated layers to be vertical or horizontal and vertical combined. A simplified approximate method was also provided, enabling the users to quickly evaluate the consolidation process of a foundation partially penetrated by the CCG columns. The proposed solution was applied to a case history of an antiflood embankment on soft soil with partially-penetrated CCG columns, and a good agreement was found between predictions and the field measurements.