Land reclamation without using soil-fills
Yeo, Eng Swee
Date of Issue2016
School of Civil and Environmental Engineering
Singapore has been developing rapidly over the past decades. In order to sustain the fast-paced economic development and urbanisation, an increasing emphasis has been placed on land reclamation projects. Coupled with inflation and increasing cost of fill materials, conventional land reclamation methods are slowly becoming less feasible due to the increasing cost. An ideal solution is the use of non-soil fill reclamation method which will eliminate the use of such fill. Before reclamation using non-soil fill technique can be carried out, feasibility of the method is first investigated. The retaining wall structure constructed must be able to bear the lateral loading of 10 m to 20 m of seawater level. In this project, analyses are performed to first determine the embedded depth of wall and average undrained shear strength of the seabed needed for the wall to be stable. Results from the analyses were unfavorable as deflection of wall is too large. It is found that an average undrained shear strength of seabed needed for a free standing cantilever wall resisting 10 m and 20 m of seawater should not be less than 35 kPa and 75 kPa. The retaining wall also has to be embedded 20 m and 35 m in order to support 10 m and 20 m of seawater respectively. With the deployment of the struts to provide additional support to the retaining wall, it is evident that the deployment is critical in improving the stability of the retaining wall. Lowering of seawater level increases the displacement of the wall. Installing strut to provide additional lateral support for the retaining wall before seawater level are lowered completely could successfully address the problem of excessive deflection of the wall. Potential seepage problem investigated in the analysis was not as serious as expected due to the small seepage flow rate which can be easily handled by a pumping. Analysis data from the project have also suggested similar finding related to Wong and Broms (1989) studies. Embedment depth and stiffness of wall has indeed plays an important role in determining the lateral displacement of the wall. With greater embedment depth and stiffness of wall, the displacement of wall are reduced. Similar to findings from Wong and Broms (1989), the undrained shear strength of clay plays a critical role in determining the displacement of the wall. Results from the analyses in this project have helped to understand the stability of the retaining wall retaining 10 m to 20 m of seawater. This, in turn, contributes to the feasibility of the non-soil fill reclamation method. However, future investigation taking into account wave actions, constructability and cost could be conducted to further substantiate the feasibility of the proposed method.
Final Year Project (FYP)
Nanyang Technological University