The efficiency of energy transfer during pile driving is heavily influenced by the mass ratio between the hammer and the pile. When a moving hammer strikes a stationary pile, the transfer of energy is most effective when their masses are similar. This principle underlies the reason why certain codes mandate a minimum ratio of 0.5 between the weight of the hammer and the weight of the pile.
If the hammer’s weight is significantly lower than that of the pile, a substantial portion of the impact energy is transferred back to the hammer upon impact. This rebound effect induces tension within the hammer and reduces the amount of energy transmitted to the pile, hindering its penetration into the ground.
In essence, a heavier hammer relative to the pile ensures that more energy is directed towards driving the pile deeper, resulting in a more efficient and effective pile driving process. Conversely, a lighter hammer leads to energy dissipation through rebound, compromising the overall efficiency of the operation.