Last edited 12 Apr 2017

Land reclamation

Contents

[edit] Introduction

Land reclamation, also known as land fill (not to be confused with landfill), is the process of creating new land from sites such as the sea, lakes, riverbeds, and so on. The general aim of land reclamation is to increase the amount of available land that could be put to economic use, such as for agriculture, housing or industry.

Land reclamation methods have been used throughout human history. For example, large parts of Bangladesh and the Netherlands were reclaimed from swamps and marshes.

There are two types of activity that are generally referred to as land reclamation. One is usually in wetland and waterway areas that are modified to convert them into usable land, or sometimes to control mosquitoes, and so on. The other is to restore damaged land to its original state, such as to restore beaches that have been damaged by natural processes. Both activities may require additional processes such as soil remediation and restoration in order to adequately reclaim the land to the point that new uses can take place.

[edit] Methods of reclamation

There are a number of different methods that can be employed for land reclamation purposes, depending upon the type of land, the type of fill material, foundation soil, seabed topography, presence of fine material, and so on.

[edit] Dry method

Perhaps the simplest method involves filling the required area with large and heavy rocks and/or cement, then building up to the required height level using clay or other soil in a process called ‘infilling’. However, this method can be vulnerable to soil liquefaction when there is seismic activity. When granular soil has been used as the fill material, this method usually results in a loose profile of fill, and so densification of the reclaimed land may be required.

[edit] Hydraulic reclamation method

This wet method is used when fill material is obtained from an offshore borrow source, but is only suitable for granular soil which has good drainage characteristics. Typically, a bottom-opening barge carries fill material from the borrow source and dumps it at the site location. This is generally suitable for a seabed of 6-8 m depth. The production rate of reclamation using bottom-opening barges will depend on the number of barges being used as well as the distance between the borrow sources and site location.

[edit] Rehandling method

This involves the use of barges to transport and dump fill material in a temporary storage pit which may have a capacity of a several million cubic metres. The location of the rehandling pit is usually selected at a natural depression on a firm seabed or created by dredging.

[edit] Hydraulic filling method

This method is suitable for granular fill and is generally used when filling is carried out from an offshore source, either from a rehandling pit or a trailer suction hopper dredger.

Fill material is dredged from the borrow source and then pumped through a discharge pipe at the site location, usually with a mixture of fill material and water, adjusted according to the grain size. Direct pumping is possible from the borrow source to the site, sometimes for distances of up to 10 km.

This method is not suitable when the seabed is too shallow or the seabed soil is too soft.

[edit] Sand spreading method

This method is used when there is a shallow seabed or the seabed soil is too soft for hydraulic filling. A spreader is mounted on a small floating barge and sand discharged along with water through perforations in the pipe. The spreader uses a winch system and a bulldozer to move from one end of the site to the other.

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