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SUB-STRUCTURE WORKS
BASEMENT STRUCTURE
Basement structures are substructures built below ground level for purposes such as parking, utilities, or retail spaces. Their construction typically involves piling and diaphragm wall works, using either the top-down or bottom-up method.
In the top-down method, diaphragm walls are first built to retain surrounding soil. Piles are then installed as supports, and basement slabs are cast on them to provide lateral stability during excavation. Openings in the slabs allow for soil removal and machinery access. Excavation continues to the lowest level, allowing above-ground construction to proceed simultaneously.
In the bottom-up method, excavation reaches the lowest slab level first, supported by temporary earth-retaining structures. The lowest slab is cast, and retaining structures are removed as slabs are progressively cast upward to ground level.
PILE CAP
Pile cap refers to a thick layer of ready-mix concrete resting on piles that have been driven into the ground to provide a stable foundation. Pile caps usually form part of the foundation of a building, particularly for high-rise buildings or structures, or support bases for heavy equipment. The pile cap distributes the load of the building onto the piles. Steel reinforcement bars are also installed within pile caps for installation of structural columns above.
RAFT AND PAD FOUNDATION
Raft and pad foundations are types of shallow foundations, i.e. generally founding levels of less than three (3) metres from ground level. Raft and pad foundations generally serve as the foundation for low-rise buildings such as terraces, but it can also be used to form the foundation
for high-rise buildings that build on relatively solid ground.
A raft foundation extends across the entire loaded area so that loads from the entire structure are spread over a large area, in order to reduce the load bearing stress on the soil. Meanwhile, a pad foundation refers to a foundation that is intended for sustaining concentrated loads from a single point load such as structural column. It typically has a larger base than the single point load in order to spread the load from the single point load across a larger area, reducing the load bearing stress on the soil
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