In the past, the design of a pile in a given soil against undue settlement has entailed lengthy numerical analysis for a variety of pile geometries. Similarly the back analysis of load tests on piles has usually been accomplished by repeated analysis with differing soil stiffness profiles in order to arrive at the profile which gives best agreement with the measured results. The recent development of an approximate closed form solution for the problem of a vertically loaded pile has enabled these two processes to be considerably simplified.
The present paper takes the solution as developed and extends it to the case of piles bearing on a stiffer stratum of soil. The solution may then be used both for the design of single piles and also for the back analysis of pile tests. For given soil conditions, it is possible to draw up design charts showing how the settlement of a pile may vary with load level and pile geometry. This process is demonstrated for some typical soil conditions. For evaluating load tests, the closed form solution may be manipulated to give an immediate estimate of the average soil stiffness down the pile for the case of tests on uninstrumented piles. If additional information (such as the settlement of the pile base) is available, it is possible to obtain an estimate of the soil stiffness profile down the length of the pile without recourse to a computer. Examples of some actual pile tests are given.