Land Reclamation: How to build on water- Part 2
Given the state of our growing population it is not really surprising that developers are gradually expanding into the sea or oceans. We have already stated the methods of land reclamation and the importance of breakwaters. In the second part of this article, we will talk about the ways in which the reclaimed land and the structures built upon it can become more resilient to earthquakes. We will also discuss how BIM Modeling Services can be utilized for ensuring the building constructed have strong foundational integrity.
Tackling challenges posed by Earthquakes:
Sand is laid on the floor of the ocean or the sea in order to create new islands. Here it is imperative that the right sand is chosen. Dessert sand is too fine and the ideal sand should be coarse, packs densely and should be more resistant to wave impact. Moreover, sand is unstable and takes a long time to settle before it becomes stronger to build on. Whenever earthquake occurs here, liquefaction takes places. Liquefaction refers to the process where the water-logged sediments near to the surface of the ground start shaking causing the water to move upwards and the land to sink. This was observed during the 1995 Kobe earthquake in Japan which created damage to the port and harbor facilities.
The solution is in the form of vibro-probe technique. In this method the probes drill holes into the ground across the surface. Then high pressure of air and water drives the probe deep into the ground following which the shaft vibrates this shaking the ground around it. Thus, the sand starts to sink and more sand is put until it becomes firm. This is a lengthy but a time-tested method that improves the soil’s resistance against liquefaction.
When it comes to constructing buildings on reclaimed land the AEC professionals must ensure that the buildings can withstand earthquakes. The very concept of earthquake proof design is that the structure should either be reinforced or there should be forces that can counteract the forces of the earthquake. Given the fact that there will be rare chances of skyscrapers on reclaimed land using the pendulum damping method might not be ideal. The main two ways by which buildings can be made earthquake proof is by using earthquake resistant materials and by implementing design solutions.
Structural Steel Detailing Services could be useful to add reinforcement to the structure. For instance, one method is too steel cross braces to the exterior of the building. They significantly reduce the impact of the building by transferring the force back to the ground. Moreover, earthquake resistant materials can also be used. Materials that are used in construction if they have high ductility then they allow the building to dissipate the energy. Brick and concrete can absorb very low energy which structural steel can have high ductility. Moreover, before construction seismic analysis should be conducted in order to determine the building structure’s response to the earthquake. Running simulation can also be useful in checking the effect of earthquake.
Ensuring a strong foundation
It is necessary to ensure the integrity of the foundation upon which the building is being constructed. During land reclamation projects the building might be sitting on soft or filled in soul which may cause the building to fail. Here, a detailed terrain model must be constructed in the pre-construction stage to gain an accurate understanding of the earthworks, terrain etc. DTM can be achieved through surveying, photogrammetry, Lidar technology etc. Knowing the exact site conditions and then building a BIM model upon it ensures an accurate representation which would avoid further errors.
There are also ways in which construction professionals can today deal with foundational problems. When it comes to soft sandy clays which could be the case when the land is reclaimed from swamps and marshes, the solution is to dig down a little further. When the standard trench foundation is deep the base can be supported on a firm ground that is not affected by seasonal changes. In areas where the ground is prone to periodic expansion and contraction the side of the trenches can be lined with flexible membrane so the clay can independently shrink or expand.
Moreover, the way buildings are designed also would be important. For instance, building the wider foundations can mean the load is spread over a large area. This may require steel reinforcement in order to avoid shearing. Finally, a raft foundation could also be created. A raft foundation is reinforced concrete slab under the building which floats on water allowing to spread the load of the building over a large area so that the pressure on ground is lowered.
Are there any downsides to building into the sea?
There are some concerns regarding the long-term impact of building into the sea. Since it creates tangles of structures beneath the sea it could cause problems for marine organization and destroy their habitats. It also could potentially destroy the coral reefs. Another concern is the impact of the breakwaters on the coastal cities close to the reclaimed land. On one hand the breakwater protects the new land from freak waves and storms it might also potentially redirect the storm inwards. This has in fact already been observed in the case of Eko Atlantic where the storms are being redirected to either side of the development project to the unprotected areas of Lagos.
When the scarcity of the land is becoming a major concern and building underwater is still just a pipe dream, land reclamation is perhaps the only available solution in the foreseeable future.