ENERGY-LOSSES IN PILE-DRIVING DUE TO SOIL RATE EFFECTS AND HAMMER MISALIGNMENT

The various factors which influence pile-driving are considered. In particular, these are examined to see how they contribute to the generally sceptical attitude of engineers towards dynamic pile-driving formulae, and to the continuing popularity of these formulae for designing piles. Two major factors are identified: the first relates to the omission of rate effects in dynamic formulae, while the second concerns misalignment of the hammer. Rate effects are studied using Smith's Law, while the general theory of impact in two dimensions is used to study misalignment. It is shown that misalignment produces motion of the pile at right angles to its axis, and subgrade reaction theory is used to study this. Measurements made during field trials on two hammers are reported, and when compared with the theory show good agreement.