Project : Labrador Substation, Singapore
Product Used : Moment JoinTec (JT) Coupler
Country : Singapore
Project Description
Moment JoinTec (JT) Coupler is being supplied to the first large-scale underground substation in Southeast Asia. Located at Pasir Panjang, Singapore, the 230-kV electrical substation underground is being built to optimize space in land-scarce Singapore for urban growth and development.
By going underground, the Labrador substation will free up 3 hectares of prime land space (equivalent to the size of 4 football fields) for a 34-storey of commercial development. When in service, the substation will serve the electricity needs of up to 8 nearby towns.
The Solution
In order to deliver a robust, safe and yet timely construction, a peanut-shaped double cell retaining wall system each with a diameter of 95m using diaphragm walls is being built. Combined with the raft foundation, it works as both a foundation and a base slab.
To enhance the integrity and strength of the diaphragm wall, the JT Coupler has been used to connect the rebar cages vertically, allowing to achieve longer cage length (instead of the conventional lapping method). This is because lapping rebar in a heavily reinforced rebar cage can cause significant congestion, resulting in problems fixing the steel and insufficient room for the proper placement and compaction of the concrete. Hence, the use of JT Couplers significantly reduced the congestion, making the placement and compaction of the concrete easier, leading to less risk of concrete segregation due to over vibration and as a result an increase in the concrete quality.
The use of rebar couplers can reduce rebar congestion as it eliminates the requirement to lap rebar.
Furthermore, with the large rebar diameters of 32mm to 40mm is used for the diaphragm wall, rebar couplers are strongly recommended by our experts, where splitting and dowel action forces can be significant. Eurocode 2 states: “Generally large diameter bars should not be lapped. Exceptions include sections with a minimum dimension 1.0m or where the stress is not greater than 80% of the design ultimate strength” and “Splitting forces are higher and dowel action is greater with the use of large diameter bars.”
In addition, the safety advantages of rebar couplers do not come at the expense of constructability. In fact, the use of rebar couplers for this project is helping the on and off-site construction easier and faster as well as safer. The prefabricated rebar cages for the diaphragm wall can be easily connected on-site, making on-site welding of rebar unnecessary. Besides, the use of rebar couplers allows the face of concrete elements to remain smooth during construction (avoiding hazardous protruding rebars), making construction easier and faster.
The Result
In spite of confronting the challenges of the pandemic, the venture able to meet the planned timeline. Utilizing approximately 200,000 pieces of Moment JT Coupler, a mechanical splice of predominant quality and reliability; Labrador Substation, the primary large-scale underground substation is able to preserve its auxiliary integrity and vigorousness.
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