KEEP YOUR FRIENDS CLOSE, ENEMIES CLOSER..
AND #SCREWPILES EVEN CLOSER
An advantage of using screw piles is that you can get the #screwpile very very very close to existing structures and boundary lines.
Whilst you can physically install both bored piles and driven piles close too - they are typically limited by the following key points:
(1) VIBRATION - vibration from vibro-hammers or impact-hammers can cause damage to an adjacent structure. Want to take that risk?
(2) PLANT - often the rotary drive table of fixed mast rigs prevent a smaller bored pile from getting close to the adjacent structure. Accordingly, the pile centre needs to be around 1.0-1.4m from the adjacent structure (depending on the rig size). Even if you wanted to use the drill table to screw the casing in - the drill table will prevent you from getting "super-close".
(3) BORE COLLAPSE - a screw pile has a permanent casing - so no chance of the ground collapsing. Operators for bored piles will typically predrill a pile location around 2m before placing the casing in the open bore as it can be hard to get the casing in position. The open bore could collapse and undermine the adjacent structure.
(4) NOISE - while it's not a physical reason, the neighbours in the adjacent structure will hear everything, and be none to happy. Screw piling is comparatively very quiet.
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More often than not the key to limiting a screw pile getting close to a building is:
- the size of the helix: 95% of helices are designed less than (around) 850mm diameter... so the pile centre could be 425mm (technically) from the boundary/structure. (Obviously through 600mm helix = 300mm pile centre, or 500mm helix = 250mm pile centre.)
- the ability to "steer" the pile: as can be seen in the picture the power head for a screw pile is often higher at the start and so can manoeuvre the pile into position - before it follows its course downwards.
No complaints on this #screwpiling job.
A handy tool for foundations.
REVEX PILING
#piling #geotechnicalengineering #helicalpiles
