Investigation of the Stability of Embankments on Soft Soil Deposits

In geotechnical engineering, the stability of embankments built on soft soil deposits is crucial because low shear strength, high compressibility, and high-water content in soft soils make them vulnerable to lateral spreading, settlements, and slope failures. There are several ground improvement methods that have been utilized to improve ground stability. However, it is essential to investigate the stability of the embankment that has been constructed on soft soils even if ground improvement techniques have been adopted. This research mainly focuses on investigating the stability of the embankment sections that have failed in Colombo-Katunayake Expressway project, which has already adopted stone column installation as a major ground improvement technique. This research has focused on three primary failing sections, which are K6 + 230 – 320, K7 + 890 – 980, and PK1 + 700 – 800. To investigate the stability of the failed sections of Colombo-Katunayake Expressway project, observational approach methods have been used instead of stability analysis or other numerical methods. The observational approach methods this research focuses on include the construction control diagram developed by Matsuo and Kawamura and the construction control chart developed from an instrumented trial embankment on soft ground at Tokai, Kedah, Malaysia. These observational approach methods have included fill height, lateral displacement, and vertical settlement as essential observed metrics. Additionally, certain successful portions of the CKE project have been plotted using both observational approach methods to make sure the curves produced make a truthful statement and to apply these techniques to the construction of embankments in the future. By the use of the observational approach methods, the most suitable method that can be used to identify and control the stability of the embankment has been selected. Keywords: Embankment stability, observational approach, soft soils, construction control chart.