Browsing by Author "Thilakasiri, H.S"

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Embargo
Investigation of the Stability of Embankments on Soft Soil Deposits
(SLIIT, Faculty of Engineering, 2024-10) Robinson, C.F; Thilakarathne, T.M.D; Thilakasiri, H.S
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.
Embargo
An Investigation on the Reliability of Pile Toe Defect Rectification Method used in Sri Lanka
(SLIIT, Faculty of Engineering, 2024-10) Hapugaswatte, M; Thilakarathne, T.M.D; Thilakasiri, H.S
The foundation is the vital part of any infrastructure as it will be the element that will eventually bear the superstructure load. In cases where the soil conditions are poor and structural loads are high, pile foundations are used more often. These piles should be defect free to not fail under the structural loads. So, the identification and rectification of such defects should be performed at early stages of construction. In this study, the reliability of the rectification method used for pile toe defect rectification in Sri Lanka (pile coring and grouting method) is studied. Raw data from 11 piles, found as defective through Cross-hole Sonic Logging (CSL) test, are analyzed. Six of these piles were retested after rectification using the same test while the remaining piles were retested using High Strain Dynamic (PDA) test. Out of the six piles, three showed an increase in the effective area, two still showed some defective areas and one was an incomplete test due to a blocked tube. Out of the five tested through PDA test, only one showed an acceptable β value, which is a parameter that represents the scale of the pile defects identified. Therefore, it was concluded that even though there is an overall improvement in the pile effective area, some defects could still exist within the pile that may require to be rectified and retested for integrity. It was also concluded that due to the comparatively lower accuracy of the PDA test, acceptance of a defective pile based only on this test without rectification is not acceptable. Future research suggestions were made to further refine the results of this research and to expand the scope to defects in other regions of the pile.