SUBMITTED BY:Hardik GosarMohsin Patel

IntroductionAnartificialorman-made islandis an orgroup of islandsthat has been constructed by people rather than formed by natural means.

Reasons for ConstructionThe following are the major reasons to justify the creation of Palm Islands:

Urban development.Recreation.Oil drills and exploration platforms.Luxury structures like hotels or water parks.

Design Considerations

Water depth Wave height Tidal rangeCurrentsFoundation conditionsEarthquake riskSource of materialsShipping lanesLegal aspectsEnvironmental considerations

CONSTRUCTION PROCESS

PRECAST PILES CAST IN YARDS, LOADED ONTO BARGES AND PLACED AT SITE.

PILES DRIVEN, SOIL COMPACTED, SURROUNDING BUND CREATED, ARMOUR ROCKS PLACED,CONSTRUCTION STARTS.

Ist challenge was to put sand into the sea bed. Dredgers would collect sand from the sea and dump it where break water was to be constructed. All this was done when sea was at its calmest. Finding the right sand was an enormous job in itself. Dubai has a lot of sand, as there are vast areas there. But desert sand was too fine and sand at sea was more coarser and resistant to waves. To keep that sand in place, bare loaded rubble was dropped on to it. This was to rise breakwater to a height of 4 m above sea level. This was beginning of the sea defence, without which island couldn't exist.Selection of Sand

Dredging is the maritime transportation of natural materials from one part of the water environment to another by specialised dredging vessels. In a usual dredging cycle, self-propelled ,trailing suction ,hopper dredgers, barges and other ships spend the majority of their time sailing back and forth between excavation sites and placement sites, transporting materials between the port and the borrow site; sailing between borrow sites; and sailing from sites where material has been extracted to unloading or placement sites.

Dredging

SUCTION DREDGE

The material dredged from the seafloor is placed either by the dredger itself by pumps on deck, or by pipelines or barges.

Global Positioning System(GPS)To insure that the island is in it s required place and shape, 676 Km up in the space a Private satellite was used. The shape of island is nearly curved everywhere and it required pin point accuracy to shape it as a palm tree, hence, GPS (Global Positioning System) was used while pouring sand into the sea.Mobile receivers were used as a grid reference for the island and the satellite gave coordinates of the point where sand was to be put. The dredgers would then fill the area of sea which they were commanded by the satellite.

VIBRO COMPACTION During an earthquake, water-saturated soils can lose their strength and transform into a liquid-like state. This process of liquefaction could cause the reclaimed islands to settle or sink.

Thus special provisions need to be made to prepare the sand base under the structure so that it does not compact. This is done using vibro-compaction.

Vibro Compaction is a process by which sand particles are caused to float, and then they are rearranged into a denser state. A vibration probe penetrates the soil and moves down via a combination of vibration, and jets of water or air.

The vibrations of the probe reorganizes the soil particles, compacting them. More infill (sand) is added until there is a column of compacted material.

Vibro flot is positioned over the spot to be compacted and the lower jet is fully opened.

Water is pumped at a rate faster than that at which it can drain off into the subsoil. This creates a momentary quicksand condition which permits the vibrator to settle.

Working

The vibroflot is slowly lowered to the bottom of the soil layer and then gradually withdrawn in 0.5-1.0 m stages. The length of time spent at each compaction level depends on the soil type and the required degree of compaction.

Backfilling is done simultaneously.

BREAKWATER CONSTRUCTIONBreakwater: A structure which breaks the force of the waves, it is constructed close to the island and acts as a protection against strong currents and winds. The breakwater is constructed using multiple layers of sand, a water permeable sheet, small rocks, and layers of armour rocks.The breakwater should be constructed out of rock rather than concrete to encourage the creation of an artificial reef.Two openings in the breakwater were created in order to prevent the water inside from stagnating.

BREAK WATER

PROBLEMS AND CHALLENGES FACEDEXCESSIVE COST INVOLVED IN CONSTRUCTION.

SLOW CONSTRUCTION PROCESS DUE TO LIMITED AVAILABILITY OF DREDGERS.

ENVIRONMENTAL IMPACT DUE TO REMOVAL AND PLACEMENT OF SAND. CAN BE PREVENTED THROUGH SHALLOW CUTS.

EXCESSIVE EXPOSURE TO WINDS, TIDAL FORCES AND EARTHQUAKE AND TSUNAMI LOADS HENCE SPECIAL PROVISIONS REQUIRED.