DYNAMIC STUDIES ON THE BEARING CAPACITY OF PILES

A reliable means of determining pile capacity from dynamic measurements is described. The method (results show excellent agreement when compared with static measurements) which depends upon the ability to make reliable accurate measurements of force and acceleration at the pile top, is described by a capacity equation: R=(f(t*) + F(t*+2L/C) /2 + Mc /2L (V(t*) -V(t*+2Lc). This procedure has been applied to 60 piles which were also statically load tested. Depending upon the pile-soil combination, dynamic forces, commonly called damping related to the relative pile velocity can occur. For most pile types, the majority of both the static soil resistance and dynamic forces have their origin at the pile tip rather than in frictional side resistance. The computational procedure is illustrated on a sample measurement record. Aspects of pipe piles, timber piles, the time-delay approach, and the static test are discussed.