Failure and Remediation of an Embankment on Rigid Column‐Improved Soft Soil: Case Study

Abstract

The south extension line was constructed as a new part of the Xintai Expressway in Guangdong Province, China. The project required the construction of an embankment over soft soil with a thickness of up to approximately 14.0 m, and prestressed pipe pile was selected for reinforcing the soft soil foundation to increase bearing capacity and reduce settlement. Embankment sliding with a length of approximately 110 m and cracking with a length that exceeded 300 m occurred before the construction of the pavement structure. Field investigation and theoretical analysis results indicate that the safety factor of the overall stability calculated by the existing code methods is overly large, thereby resulting in large design pile spacing, low design bearing capacity provided by single pile, and excessive load shared by subsoil between piles. These results all cause the flow sliding of soft soil between the piles and the bending fracture of some piles. The revised density method can be used to check the stability of flow sliding, and the bending moment of piles should also be checked during the embankment design stage. In addition, perpendicularity deviation and poor joint quality of pile construction also contributed to the reduction of the bearing capacity of the pipe piles and the overall stability of embankment. Reconstruction of additional rigid piles and add pile after drilling holes are adopted in the sliding and cracking sections to reinforce the failed embankment, respectively. The remediation effect was validated by the measured excess pore water pressure, subgrade settlement, and horizontal displacement.

Numerical Analysis of Differential Settlement in Road Due to Widening Considering Different Reinforcement Techniques

“…The differential settlement increases with increasing groundwater level and subgrade height [27]. The differential settlement creates a soil arching effect in the embankments [28], which is higher at the edge of the slope than at the centerline [29]. Aiming at the above-mentioned issue, this research is based on the road widening project of National Highway-120 (N-120), Sindh, Pakistan.…”

Cyclic and Post-Cyclic Behaviors of Stabilized Sand-Containing Soft Soil in Coastal Areas

“…In addition, Borrelli [2] studied the land use and climate change impacts on global soil erosion by water (2015-2070) and pointed out that a 30% growth in the area of water and soil loss due to the possible exacerbation of climatic conditions may occur by 2030. As a result, a large number of infrastructures, such as expressways (e.g., Foqingcong Expressway [3] and Xintai Expressway [4]) and high-speed railways (e.g., Beijing-Shanghai high-speed railway [5] and Lian-Yan high-speed Railway [6]), have no option but to be built in soft soil regions. In addition, it is widely accepted that soft soil with the characteristics of high moisture content [7], high void ratio [8], low permeability [9], and poor bearing capacity [10] is not fit for engineering constructions such as expressways and high-speed railways.…”

Analysis of the Embankment Settlement on Soft Soil Subgrade with a Cement Mixed Pile

“…is results in great differences in the settlement, as well as the additional stress of the widened subgrade and pavement. us, soft soil foundation treatment is currently the focus of much academic interest [1][2][3]. Tan et al employed the finite element method to analyze the settlement deformation of the widening subgrade with PTC piles and compared the results with measured values [4].…”