We continue on with our mini series by exploring the second stage in the construction of an elevated MRT line. This involves earthworks and the process for an elevated line is vastly different from that of the more common underground lines here. Join us as we dive into the processes under this stage!
Stage 2: Earthworks
Various activities are carried out during this phase of construction with the aim of constructing the foundations for the viaduct and station piers that serve to support the line. As such, earthworks for an elevated MRT line are far more widespread than that of an underground line. Here's a list of some of the work activities one can expect to encounter.
The aim of this stage is to construction all the foundational elements of the line. Foundations are elements that help to spread the load of the above ground structures like viaducts & stations. To do so, we need to be familiar with the components that support the above ground structures:
1) Piles - these are concrete tubes that extend below the ground to anchor the structure to the ground & assist with load dispersal.
2) Pile cap - this is a flat slab that connects the pier column to the piles & helps to spread the load from the above ground structure to the piles in the ground. Its similar to how a slipper distributes your weight evenly across the ground, rather than a single point.
3) Column - the pier column is the element that bears the weight of the above ground structures and transfers it to the pile cap.
A video showing the process of constructing
a bored pile.
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| 5 February 2023 - Bored piling at Bahar Junction station, under contract J105. |
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| 5 February 2023 - Bored piling at Bahar Junction. |
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| Along Choa Chu Kang Avenue 3, under contract J102. |
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| 2023 - Bored piling along Jurong West Avenue 2, under contract J103. |
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2 October 2022 - Bored piling along Jurong West Street 64, under
contract J106. |
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| May 2022 - Bored piling at Gek Poh, under contract J107. |
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| June 2022 - Bored piling at Tengah Park, under contract J108. |
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| January 2023 - Bored piling at Pandan Reservoir, under contract J109. |
Once excavation within the hollow tube is completed, a rebar cage can be lowered in. A rebar cage is made from steel and will provide rigidity to the structure once filled with concrete in a process known as casting. This process needs to be continuous to ensure that the concrete poured in solidifies as a single mass to avoid cracking, which may occur when a pour begins and the first batch solidifies before a second batch can be poured. This ensure the quality of the pile is maintained as the structure is located underground where inspections cannot be easily carried out, unlike for pier columns which are above ground and defects easily spotted & accessed to correct.
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4 September 2022 - Rebar on site at Choa Chu Kang, under
contract J102.
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| 12 February 2023 - Rebar on site near the Pan Island Expressway, under contract J103. |
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30 October 2022 - Rebar on site along Jurong West Street 64, under
contract J106.
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| 24 April 2022 - Rebar on site at Jurong East, under contract J110. |
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Notice from contractor about continuous concrete pouring as part of pile
casting works to ensure quality. |
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| A note from the contractor on works extension to complete the pile casting. |
Once the bored piles have been cast, the process moves on to the next stage of construction where sheet piles are installed around the perimeter. This enables the top soil to be excavated, exposing the top parts of the bored piles. From here, some hacking can be done to enable the rebar cage for the pile cap to integrate with the bored piles to form an integrated structure that is capable of bearing and transferring the loads from the above ground structures.
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17 November 2022 - Sheet piles being delivered to site, under contract
J106 at Boon Lay. |
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| 2 December 2022 - Sheet piles installed after delivery, contract J106. |
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2 October 2022 - After installation, the soil is excavated to expose the top
parts of the bored piles, contract J106. |
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12 December 2022 - Following excavation, the top parts of the bored piles
are hacked to expose the rebar. This allows for the pile cap rebar to be
woven in and allows for an integrated structure to be built. Here is one
in the process at Choa Chu Kang, under contract J102. |
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2 January 2023 - After the pile cap rebar has been installed, concrete is
then poured to construct the pile cap. |
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| 2 January 2023 - Several sheet pile excavation sites at Choa Chu Kang, under contract J102. |
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9 October 2022 - A view of sheet pile excavation sites along Jurong
West Streets 75 & 81, under contract J107. |
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| 5 February 2023 - With the pile caps cast, backfilling works begin. Gek Poh, contract J107. |
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| 5 February 2023 - Backfiling underway at contract J107. |
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5 February 2023 - Sheet pile removal upon completion of soil
backfilling on top of the pile caps. |
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25 September 2021 - An excavation pit for the pile cap, however this pit omits the use of sheet
piles, instead opting to use shotcrete. The process remains similar nonetheless. Tengah near
Bukit Batok Road, under contract J108. |
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| February 2022 - The pile cap completed, the excavation pit has been backfilled. |
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| February 2022 - A close up view of the backfilled excavation pit. |
Once the pile cap has been cast, the soil is backfilled on top and the sheet piles are removed concluding the earthworks stage. The works then move on to the next stage of construction thereafter which is structural works. We'll cover this in greater detail next week so do stay tuned. In the mean time, why not drop by our Facebook page and participate in the giveaway? We've simplified the steps for your convenience and each entry allows you a chance to win at the final draw. Better yet, tell others about this series by sharing it on your social media feeds. Till next week then!
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