For the Changi East Reclamation Projects in Singapore, about 140 million metres of prefabricated vertical drain (PVD) are being installed. Due to the requirement of large quantity of materials, several types of prefabricated vertical drains are being used. Quality control system was established to check on the quality of vertical drains. The methods and procedure of quality control tests of both hydraulic and mechanical parameters of prefabricated vertical drain are described in this paper. The tests results and the factors affecting the resultant parameters of PVD are discussed.
The Changi land reclamation projects in Singapore cover more than 2000 hectares area and are being carried out in four phases over 7 years. Several types and more than 140 million metres of PVD are being used for soil improvement works. These include Colbond CX 1000, Mebra MD7007 produced in Holland, Korea and Malaysia and Flexi FD767 drains. As different types and huge quantity of drains are being used, quality control of the drain materials and installation procedures become an important task. To serve this purpose, requirements for the specific properties of vertical drains are specified and a quality control system has been established to check the properties of the drains and to supervise the construction process. For vertical drains, both the hydraulic and mechanical properties were checked before installation. Laboratory vertical drain testing devices were developed to measure the discharge capacity of the drains, the permeability of the filter, the apparent opening size (AOS) of the filter, and the tensile strength of both the drain and the filter. The hydraulic properties affect the performance of PVD whereas the tensile strengths of both the drain and the filter are required to ensure the integrity of the drain after installation.