Ground improvement on land reclamation project-prefabricated vertical drain with pre-loading

Abstract

The presence of soft marine clay deposits makes the land reclamation become a great challenge in the field of geotechnical engineering due to the nature of high compressibility, excessive settlement characteristic and low shear strength. Ground improvement works in the ongoing Tanjung Piai Maritime Industrial Park (TPMIP) reclamation project comprise the installation of prefabricated vertical drains (PVDs) with preloading and subsequent placement of sand surcharge to improve and accelerate the consolidation of the underlying compressible soils. Therefore, the desired degree of consolidation have to be achieved or ascertained prior to the surcharge removal in such ground improvement projects. The ultimate settlement can be predicted by both empirical analysis (Terzaghi?s theory of one-dimensional consolidation) and numerical analysis (Finite Element Modelling), and subsequently compared with the field settlement monitoring results (Asaoka Method). The predicted magnitude of ultimate settlement obtained from empirical analysis is 2141 mm whereas ultimate settlement obtained from numerical analysis is 2298 mm showing that 2% and 8.5% respectively higher than ultimate settlement predicted from Asaoka?s plot. The results obtained from both empirical analysis and numerical analysis approach reflects that consolidation settlement calculation showing a good agreement on both methods. However, it was expected that the different rate of consolidation settlement is inevitable due to certain constraint in applying the soil parameters which obtained from the ground investigation works. Therefore, the actual monitoring results should reflect the actual soft ground condition and the designer can deploy theoretical calculation in consolidation settlement analysis for future works.