Palm Islands, Dubai – Compression of the Soil
Ground Improvement for Man-Made Island
Beginning in 2001, three man-made islands in the form of palm trees are being constructed off the coast of the Emirate of Dubai. The islands consist of Palm Jumeirah, the smallest island, Jebel Ali, and Palm Deira, the largest island. These projects are only possible due to a topographic feature: the shallow, coastal sea in the Persian Gulf reaches far into the open sea, reducing the water depth. With a planned area of 50 square kilometres (km²) Palm Deira will be 25 times larger than Monaco upon completion.
We were contracted to design and manage quality on the sand and stone base of two palm islands in Dubai. We succeeded by using depth vibrators and continued testing despite the declining quality of the bulk material.
CDM Smith was contracted to develop the geotechnical design and quality management for the compression of the banked sands for Palm Deira and the expansion of Palm Jebel Ali. A total of about 200 million cubic metres (m³) of sand and stones were necessary for depositing as well as the construction of the wave breakers. The deposited calcareous sand was transposed into vibration using depth vibrators (vibro-compaction) in order to compact the sand, so that it would later not give way. This process, which usually lasts for decades in nature, was accelerated enormously. Due to the number of land reclamation projects, the quality of the bulk material continuously declined. Under our supervision using this method, the compaction work was successfully continued in spite of the increased fine content of the soil.
In order to calculate and execute the compaction, two criteria must be met: the allowable construction of buildings and other structures as well as stability against earthquakes. The risk of liquefaction had to be eliminated during construction. For calculation and quality assurance purposes we examined the properties of the deposited shelly sand in the context of a large scale test at the site. In addition, we carried out large-scale load tests (CPT-tests) to check the actual achieved level of compacting.
