The hydraulic filling method is suitable for granular fill. Generally, this method is used when filling is carried out from an offshore source, either from a rehandling pit, as explained earlier, or from a trailer suction hopper dredger. In the case of pumping from a cutter suction hopper dredger, the fill material is dredged from the borrow source with its own trailer suction dredger which is moved adjacent to the reclamation area and then pumped through the discharge pipe. Bulldozers are used to grade and spread the fill material around the discharge pipe. The discharge pipe is usually set slightly above the required finished level. Pumping is usually done with a mixture of fill material and water. The ratio of fill material to water is adjusted according to the grain size of the fill material. A large ratio of material to water would lead to wearing of the inner walls of the sand transportation pipe. On the other hand, a smaller ratio of material to water will reduce the production rate. After a certain amount of land has formed, the pipes are extended accordingly. Usually, the diameter of the sand transportation pipes is about 800 – 1000 m and 10 meters in length. Normally, wearing occurs at the bottom of the pipe, therefore, frequent rotation of the pipe after usage is necessary. Pipes that have to run above water can be floated with floaters attached to the pipes.
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