Digging A Foundation

The construction of holes is one part that was lacking at the beginning of my Nova Center Blog, However is being corrected with the Maple.

Buildings need to sit on a Solid base. In Halifax, that base is bedrock, and bedrock lies close to the surface here. This means construction usually requires blasting out Bedrock. Blasting is a simple process. You drill holes with certain spacing and depth, place explosives at the bottom, set them off, then dig out the Broken Rock, repeating as required. To control Dust and Fragments, Heavy mats made of old tires are laid over the blasting area.

All the elements of the excavation. Excavators, Rock Drills and Blasting Mats.

Before excavation can proceed, care must be taken to prevent cave ins.  Temporary shoring is installed. This can be seen in the photos above as the steel H Piles, and timber lagging boards.

Drill for installing piles.

To install the H Piles, Holes are first drilled down to bedrock with a Large Drill. The H Piles are placed in the hole, and Cemented into place.


Piles Cementer into the holes

The lagging boards are  then installed into the H Pile, And fill placed on the backside.

Lagging being installed in H piles

Lagging being installed in H piles

Extra support is required in many cases, and the lagging is secured to the ground behind it via a tieback anchor. Holes are drilled at an angle into the face of the excavation.

Drilling for Tie back Anchors

Drilling for Tie back Anchors

And the Anchor inserted into the hole. A crane is often used to help guide the anchor in.

Tieback being inserted with a crane and man power

Tieback being inserted with a crane and man power

The Cable is then grouted in place with cement

Tieback anchor grouting operation.

Tieback anchor grouting operation.

And finally pulled with a Hydraulic Jack, to post-tension it. A cap is then placed on the front to secure the tieback to the lagging and H piles,  and the job is complete.

Tiebacks can also be used to anchor anything to bedrock. In the Case of the Roy Building demolition, the foundation of the Vogue Building sits higher then the bottom of the Roy Building. Tieback anchors are being drilled through the bottom of the vogue buildings foundation, to anchor it to the bedrock bellow to ensure the building does not splay out at the base once the rest of the Roy Building is removed.

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BuiltHalifax delves into architectural history and theory with a local slant. Produced by Peter Ziobrowski, it is the sister project to HalifaxShippingNews.ca