LAND RECLAMATION USING PREFABRICATED VERTICAL DRAINS (PVD) IN PORT OF MOMBASA

Abstract

Land reclamation is used to describe two different activities. In the first sense, it involves modifying wetlands orwaterways to convert them into usable land, usually for the purpose of development. It can also be a process inwhich damaged land is restored to its natural state. In both cases, the term is used to refer to some sort ofprocess that is designed to fundamentally alter the characteristics of a piece of land to achieve a desired endgoal. The need for additional port capacity in Kenya has rapidly risen over the last few years due toglobalization. Due to high cost of land procurement, land reclamation has become a very promising alternativefor expanding and constructing new ports. The presence of soft marine clay poses a major challenge for portdevelopment as it requires ground improvement. The Mombasa Port Development Project in the Republic ofKenya involved the filling of approximately 6 million cubic metres of sand for the land reclamation of a totalarea of about 49 hectares. Land reclamation was carried out using fill materials obtained from dredginggranular material from the seabed at the borrow source situated near Tiwi in Kwale County. The groundimprovement technique that involved combination of prefabricated vertical drain (PVD) with preloading wassuccessfully applied in this project to improve the underlying compressible soils. The project comprises theinstallation of prefabricated vertical drains and the subsequent placement of surcharge to accelerate theconsolidation of the underlying marine clay. The objective of the research is to assess the disparity ofperformance of ground improvement and to validate the performance of the prefabricated vertical drainsystem. Several geotechnical instruments were installed to monitor the degree of consolidation at both areaswith PVD and areas without PVD as control area. This paper provides a case study of the ground improvementworks carried out with prefabricated vertical drains at the Mombasa Port Development Project will attain ahigher degree of consolidation than the control area by about 60%.