Centrifuge Testing of Fixed-Head Laterally Loaded Battered and Plumb Pile Groups in Sand
Centrifuge tests were conducted on driven in-flight fixed-head plumb and battered 3 × 3 pile groups at three-diameter (3D) and five-diameter (5D) spacings. The piles simulated 430-mm-diameter by 13-m-long pipe piles founded in medium loose (Dr = 33%) and medium dense (Dr = 55%) sands. The battered groups were in an A frame arrangement, i.e., each pile in a given row battered the same. Results of the tests showed that fixed-head plumb groups have a 30 to 55% higher lateral resistance than free-headed piles depending on soil density and pile spacing. For the battered 3D-spaced group, the lateral resistance was greater by 20 to 50% than the fixed-head plumb response in the medium dense sand; however, in the medium loose sand, the battered and plumb fixed-head group response was very similar. The latter is attributed to the limited axial tension capacity of the piles in the medium loose sand (Dr = 33%). Increasing the dead load on a battered group to 45% of its axial capacity resulted in a 30% increase in the group´s lateral resistance. The lateral resistance of the 5D-spaced battered groups were in all cases greater than their 3D counterparts.