Underpinning Archives - Moretrench

Micropiles

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Micropiles can be utilized also for underpinning.  They would typically be installed immediately adjacent to the structure to be supported.  A pile cap or a temporary bracket may be mounted to the underside of the footing and may be used to transfer the load to the micropile.

Bracket Piles- Bracket piles are typically used in conjunction with earth retention work to support and/or stabilize existing foundations adjacent to a proposed excavation. The new piles are installed in pre-drilled holes alongside the exposed wall or column footings.  A bracket is mounted to the underside of the footing and attached perpendicular to the new pile to transfer the load below excavation subgrade.

Piles

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Helical Piles -Helical piles are structural underpinning elements primarily used for foundation settlement control. The piles are hydraulically screwed in the ground until the required resistance is reached to achieve pile capacity, and attached by means of a bracket to the adjacent distressed footing.

Conventional Concrete Pit Underpinning

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Conventional concrete pit underpinning is accomplished from small, wood sheeted pits constructed beneath the foundation to be supported, typically accessed via an approach pit. Following excavation to the desired level, the pit is filled with concrete to within several inches of the foundation underside. Load transfer is accomplished by dry-packing the gap with stiff mortar.

Engineers can choose from a number of above-grade underpinning techniques during the design phase of the project. Nevertheless, there are circumstances – such as when new construction abuts tight against an existing building – where the conventional concrete underpinning method is often the best or only viable option.

Overview

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Underpinning may be required to provide the additional foundation support needed to withstand increased loading, to halt ongoing settlement, to underpin existing shallow foundations prior to adjacent new construction, and for seismic retrofit.

Moretrench offers several methods of structural underpinning including the conventional concrete pit method, micropiles, soil nailing and bracket piles. Ground modification methods of underpinning may include ground freezing, and permeation and jet grouting.