Repeated Loading on Single Piles in Sand

Nondynamic repeated load tests were conducted on single friction piles embedded in a medium dense sand. The 19-mm (0.75-in.) diam pile was instrumented to measure the distribution of axial loads along the shaft. It was found that the response of the pile to repeated loads is governed by the: (1)Type of load; (2)amplitude of load; anf (3)number of cycles of load applied. The effect of repeated loading was to bring about not only large changes in the net movement per cycle, but also a redistribution of loads between the shaft and the base. In general, the pile behavior is marked by two or three stages of relative stability or instability in terms of the net movement per cycle. The response of the pile to a small repeated load is characterized by a long and highly stable stage which, in some cases, is followed by an unstable stage.