Generally the size of hammer is more important factor than type of hammer. A heavy pile should be driven by a heavy hammer delivering large energy. Preferably the weight of HKjmcr should beat ^H HB1 the total weight of the pile and the deriving energy should be at Hpiie foot-pound for each pound of pile weight. Each type of hammer has its use under suitable conditions, The advantages and disadvantages of cach type are summarized below:

Single-acting hammer :

They arc advantageous when driving heavy piles in compact or hard soils; the heavy ram striking at – tow velocity produces least damage due to impact. The disadvantages arc low driving speed and large headroom requirement.

Double-acting hammer:

They are generally used to drive piles of light or moderate weight in soils of average resistance against driving. This type of hammer can drive piles at fast speed, requires less headroom and can be used to extract piles by turning them [i.e. the double-acting hammer] upside down.

Diesel hammer:

They are similar in application as double-acting hammers, but driving may become difficult in extremely soft ground.

Vibratory hammer:

They have fairly good results in silty and clayey deposits. They are used in heavy clays or soils with appreciable numbers of boulders. See above for other advantages.