Experiences with Predetermining Pile Lengths

In the design of pile foundations there are two problems for which no adequate solutions have been found in common engineering practice. One of these problems is to estimate the required lengths and probable behavior of different types of piling when it is not feasible or economical to perform fullscale driving and loading tests previous to preparation of complete construction plans. The other is to evaluate the significance of various factors that affect the behavior of piles both during driving and under test loads: The methods described for predetermining pile lengths and bearing capacities are not offered as a final answer to all problems in the design of pile foundations, but rather are intended to complement other methods of determining the probable safety of such foundations. These methods can be used for evaluating the bearing capacity of single piles-however, determination of the probable settlements and safe loadings for large groups of piles requires other and additional analyses. Incompleteness of knowledge and imperfectness of materials impose such wide limits of accuracy on pile foundation analyses that most conclusions must, to some degree, be empirically based upon observations and performance records. Typical foundation designs employing various types of piling are presented to illustrate the methods described.