Land Reclamation: How to build on water- Part 1
As the population increases land becomes extremely valuable. The scarcity of land leads the developers, engineers and architects to edge further into the sea. The past few decades have seen huge islands and giant constructions build upon water. Millions of tons of materials are dumped into the water bodies in order to either create new land or restore areas affected by natural forces.
The fervor with which land reclamation projects are expanding is drastic. There are numerous examples scattered across the globe like the island state of Singapore which has added 22% onto its size or Netherlands which reclaimed large swatches of costal swamps and marshes to house its ever-growing population. The biggest and the most prominent example is perhaps the visually spectacular Palm Jumeirah islands in Dubai which has been built from an estimated 110 million cube meters of sand.
When it comes to constructing new islands on water and thereby building whole cities upon it there are various challenges. From protecting the new land from natural forces to constructing roads, underground MEP systems and buildings upon it. This requires sound knowledge of engineering as well as enhanced capabilities for better visualization, coordination, interference checking etc. BIM for infrastructure could facilitate an ease in communication, analysis and simulation, project management and asset management. In the below article we aim to discuss what is land reclamation, the methods used in it and state how Building Information Modeling can be useful for constructing upon it and keeping the inhabitants safe.
What is Land Reclamation?
Land Reclamation or land fill is a process where new land is created from water bases like sea, ocean, lakes, riverbeds, swamps etc. The very idea of land reclamation is to create new land which can be used for housing, agriculture or simply as in the case of Dubai to expand its shoreline and attract new tourists. There are two types of land reclamation; one is to convert water bodies into new usable land. The second is to restore areas that have been damaged by natural forces such as storms, erosion etc.
Methods of Land Reclamation:
There are four methods in which land reclamation processes are carried out. The method chosen depends on a variety of factors like type of land, the availability of material to be filled, foundation of soil, topography of waterbed etc.
- Dry Method: This is the simplest method of land reclamation. Here the required area is filled with large and heavy rocks or with cement. Then the land is built up to the required height by using clay or soil.
- Hydraulic Reclamation Method: In this method a bottom opening barrage carries fill material from the offshore borrow source and dumps it at the appropriate location. It is a wet method wherein the soil must have good drainage characteristics.
- Rehandling Method: Here barrages are used to transport and then dump fill materials into a temporary storage pit. The rehandling has a capacity of several million cubic meter.
- Sand Spreading Method: When there is a shallow seabed or the seabed is too soft for hydraulic filling this method can be used. A spreader can be mounted on a floating barrage and sand is discharged along the water through a pipe.
Requirements for Land Reclamation:
Given the fact that land reclamation draws a very thin line between the ocean and land there are some unique challenges that arise. The foremost challenge is faced when the land reclamation process is taking place like controlling the force of sea and ensuring safety of habitants. The second set of challenges are faced when roads, pipelines and specifically heavy buildings are being constructed on reclaimed lands. Even the project of land reclamation must be extensively and elaborately planned. That means identifying the suitable fill for the borrow area, selecting equipment and materials, collecting hydrographic data, conducting cost benefit analysis and through project monitoring. Fortunately, the modern construction methods like BIM Services, Facility Management, GEOBIM etc. all provides the construction sector the tools for streamlined and construction and maintenance.
How to dealing with Natural Forces?
When it comes to constructing on water there are various natural forces that need to be kept in mind like freak waves, earthquakes, erosion and even the one in 1000-year storm. The area constructed must be able to withstand even the worst-case scenario. Keeping this in mind there are two main things which the engineers and designers have to keep in consideration: the surrounding ocean or the sea and earthquakes.
Importance of a Breakwater:
In land reclamation projects it is essential that the land would be able to withstand the strong waves of the ocean, the oceanic storms and the rising water levels as a result of global warming. The solution here is to create a breakwater. Breakwater is a structure that is constructed for the purpose of creating an artificial harbor so that the area in between is protected from the waves. It is in simplest terms a sea wall that rises above the surface. Breakwaters have been constructed in various cases such as in the case of Palm Jumeirah. A crescent shaped breakwater was created to surround the fronds of the Palm. The breakwater rose approximately 4m above the surface of the sea and was made primarily out of sand and rocks.
Another example of the importance of breakwater is that of the one built is in Lagos’ land reclamation project. This mammoth project sees the city’s coastline expand by almost 2kms into the Atlantic Ocean. Dubbed the ‘Great wall of Lagos’ the 45-meter-wide structure risers 18 meters from the ocean floor and protects the reclaimed land. It is made up of 12 layers of rock and concrete and its visible top layer is formed with 100,00 plus x shaped concrete blocks. These concrete blocks are specially moulded using a concrete mix that would not degrade over time in an oceanic environment. Moreover, they have not been haphazardly placed but are specifically placed along X, Y and Z axis so that they can interlock with one another and create a unified structure.
To create a resilient breakwater is a complex task. There are various calculations that need to be conducted regarding the height of the waves, the wind currents etc. The location of the breakwater should be determined precisely so that it protects the inland. Finally, the construction process should be properly monitored from the supply of materials to daily progress. BIM for infrastructure could hold certain benefits as it would all to track, schedule and also run simulations. Revit Family Creation Services can also be used to model unique elements like the x shaped concrete blocks mentioned above. Moreover, BIM’s enhanced collaborative capabilities could allow all the stakeholders from engineers to scientists to project managers and investors to work together. It thus adds value throughout the planning and construction stage.
In the subsequent part of this article, we will be looking at how engineers ensure that the reclaimed land and the buildings constructed on it can withstand earthquakes. We will also talk about how Structural BIM can be used to overcome foundational challenges. Finally, we will discuss the environmental impact of land reclamation and state the way critics deal with it.