Centrifuge testing of large laterally loaded pile groups in sands

An apparatus was developed to load large pile groups (3 x 3 to 7 x 3) founded in sand in the centrifuge laterally The device consists of a hydraulic jack apparatus to install the piles, strain gauge instrumentation, and a data acquisition system. The instrumentation allowed the determination of both bending moments and shear forces at the head of each pile. Lateral load tests of 3 x 3 to 7 x pile groups were conducted in both loose and medium dense sands. Based on the test results, the pile group interaction effects were investigated. It was found that the p-y multiplier concept was valid. Also, the p-y multipliers (p specifically) are found to be independent of soil density and only a function of the pile group geometry. For this study (pile spacing was fixed at 3 diameters), they were found to be only a function of row position. Single pile tests were also completed for comparison purposes.