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A Dynamic Duo for Holding Back Ground Water
In the realm of construction, where water intrusion poses a persistent threat to structural integrity, innovative techniques are constantly sought to fortify foundations against the relentless forces of moisture.
Among these, Rafn recently had the opportunity to utilize secant piles in tandem with a tremie concrete slab as a solution to protect against a high-water table on a new apartment construction project.
These two methods worked in tandem to create a robust and impervious structure, keeping water out during construction of the concrete elevator pits.
Secant Piles: Building a Resilient Foundation
Secant piles, also known as interlocking piles, are deep foundation elements designed to form a continuous barrier against water ingress. They are constructed by overlapping primary and secondary piles, creating a sturdy wall that prevents water from penetrating between them. The primary piles are installed first, followed by the secondary ones, which are constructed to fit precisely between the primary piles.
The construction process of secant piles involves drilling into the ground and filling the voids with high-strength concrete or grout. This creates a solid and impermeable barrier that withstands the hydrostatic pressure exerted by groundwater. Secant piles are particularly effective in challenging soil conditions and can be installed at various angles to accommodate the specific requirements of each project such as avoiding underground site utilities or critical structural elements.
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Tremie Slabs: Sealing the Foundation
Tremie slabs, also called underwater concrete slabs, serve as a protective concrete cap that prevents ground water from percolating up into the excavation.
They are constructed using the tremie method, wherein concrete is poured through a pipe to form a seamless and dense concrete slab underwater. This method ensures that the concrete is placed without segregation, resulting in a uniform and impermeable barrier.
Tremie slabs are especially beneficial in areas with high water tables or where structures are subjected to hydrostatic pressure. By creating a watertight seal between the tremie slab and the secant piles, tremie slabs prevent moisture from seeping into the work area without the need to continuously dewater the project site.
The Synergy of Secant Piles and Tremie Slabs
At our new apartment construction project, the team had to solve the constructability issue of a high-water table in conjunction with a jurisdictional constraint not allowing dewatering of any kind.
By combining secant piles with a tremie slab, a water-blocking solution was presented but there were significant hurdles to get over. The safety procedures of this work were of utmost importance and we put into place a specific safety plan for working over and around water along with numerous pre-work safety logistics meetings.
In the end, combining secant piles with concrete tremie slabs represents a formidable duo in the realm of waterproofing that provides a safe, dry, and clean work floor to build the elevator pits.
Jered Cottell
As a Project Manager, Jered is the information hub of his project which suits his desire to decrease project entropy and increase personnel productivity, all while zooming in and out to insure the big picture items are all accounted for. He is dependable and reliable, effectively working with each of the personalities that make up a project, driving everyone forward to a successful outcome.