90 Piling equipment and methods
A difficulty arises in using the diesel hammer in soft clays or weak fills, since the pile
yields to the blow of the ram and the impact is not always sufficient to atomize the fuel.
Berminghammer have developed a high injection pressure, ‘smokeless’diesel hammer
which virtually eliminates the problem. The more resistant the ground, the higher the
rebound of the ram, and hence the higher the energy of the blow. This can cause damage to
precast concrete piles when driving through weak rocks containing strong bands. Although
the height of drop can be controlled by adjusting, by a rope-operated lever, the amount of
fuel injected, this control cannot cope with random hard layers met at varying depths, partic-
ularly when these are unexpected. The diesel hammer operates automatically and continu-
ously at a given height of drop unless the lever is adjusted, whereas with the single-acting
hammer every blow is controlled in height.Figure 3.15Delmag D30–20 diesel hammer on American style leaders with helmet for driving steel
H-piles.