Monday, February 11, 2013

Timber Piles.

The oldest material used for piles is timber and it is still  in use, particularly in developing countries, today. It has proved surprisingly durable and provided care is given to the detail and treatment of the toe and head of the pile and the durability conditions it should still be used where it is economical. The toe can be subject to splintering during driving and should be tapered to a blunted point and,  if necessary, encased in steel. The head of the pile during driving may also need protection from splintering and this is usually provided by placing a driving cap or helmet over the head of the pile.

Where the top of the pile is below the lowest water level and is in permanently wet conditions, experience shows that there are few durability problems. However, when the level of the top of the pile or any part of it is in the area of a fluctuating water-table and is therefore subjected to alternate wetting and drying, this section of the pile should be treated with preservatives and water repellents and even then may still have a limited life.

If the length of the pile is found on site to be too long there is little problem in cutting off the excess length but there is a problem if the pile is found to be too short. Extending the pile involves splicing on an added length and any metal connections must be corrosion-resistant.

The choice of timber is not restricted to dense timbers such as greenheart or oak, except in conditions where the pile is subject to alternate wetting and drying such as in piles  supporting jetties in tidal conditions. In numerous structural surveys of Victorian buildings the authors’ practice has discovered, in good condition below the water-table level, timbers such as birch, larch, pine, etc.

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