Contiguous Bored Pile

Discover Contiguous bored pile techniques by Foundation Alliance

Contiguous pile walls are installed using rotary bored or CFA techniques. This type of retaining wall is constructed with spaces between adjacent reinforced concrete piles and is used on a range of engineering or building projects including but limited to road or rail underpasses, underground shafts/tanks, cut and cover tunnels/portals or basements.

Contiguous piled walls are used in dry and cohesive soils and are often the quickest and more economic method of constructing retaining walls. In certain ground conditions it may be necessary for the design to incorporate temporary props or ground anchors to provide additional lateral support to the wall.

Contiguous Bored Pile Processes

1.     Position of bored pile

Three (3) reference steel pins shall be installed equidistant at not less than 1.5m from the pile centre location pin.

2.     Installation of casing

The temporary steel casing shall be installed by rotary method using boring rig rotary drive adaptor with frequent verticality check against two plumb bobs placed orthogonally at least 10m away from the casing, or by spirit level if casing length is less than 6m.

3.     Augering of borehole

Soil auger and boring buckets shall be used to bore out soft to hard soils. When very hard soils are encountered, heavy-duty boring buckets shall be used. During the boring process, retaining fluid such as polymer will be introduced into the borehole.

4.     Installation of steel cage

The crane lifts up the steel cage and places it within the borehole.

5.     Concreting of borehole

Concrete is then poured into the borehole using tremie method to form the bored pile.

6.     Extraction of casing

The temporary casing shall be extracted using rotary method by boring rig rotary drive adaptor.

7.     Contiguous bored pile installation sequence

Boring of next pile shall be carried out after 24 hours of casting adjacent pile. Steps 2 – 6 will repeated till the entire length of the contiguous bored pile wall construction is complete

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