Field Instrumentation Assessment of Offshore Land Reclamation Works

The Changi East Reclamation Project in the Republic of Singapore necessitated offshore land reclamation for the future airport and associated facilities. Ground improvement works in the project comprise the installation of prefabricated vertical drains and the subsequent placement of sand surcharge to accelerate the consolidation of the underlying soft marine clay. In such ground improvement projects in soft soil, the degree of improvement attained by the marine clay has to be ascertained to confirm whether the soil has achieved the required degree of consolidation to enable surcharge removal. This analysis can be carried out by means of observational methods for which continuous records of ground behavior can be monitored from the date of instrument installation. The Case Study Area conducted in the reclamation site consisted of a Vertical Drain Area and an adjacent untreated Control Area. Both areas were fully instrumented and monitored to compare the degree of consolidation of the areas close to the surcharge removal period. Instruments installed, monitored and analyzed in the Case Study Area include settlement plates, deep settlement gauges, pneumatic piezometers, electric piezometers and water stand-pipes. This paper discusses the methodology of land reclamation as well as the suitable types of field instrumentation for such projects.