Offshore structures when subjected to cyclic loading will generate excess pore pressure in the underlying sediment. Depending on the sediment drainage conditions, the cyclically induced excess pore pressure will dissipate with time. The dissipation of excess pore pressure may lead to additional settlement (post cyclic shakedown) in addition to the ongoing static settlement that will occur to consolidation and creep. Despite extensive research on the behavior of carbonate sediments, and the fact that post cyclic response is a key aspect of offshore foundation design, there is little published data on the post cyclic response of these sediments. This paper presents the results of a systematic experimental study on the post cyclic behavior of carbonate sediments. The laboratory testing programme include basic classification, consolidation (CRS) and simple shear tests. The tests were performed on two different types of carbonate sediments representing different formation condition in terms of their depositional environments, physical characteristics and carbonate content. The results show that carbonate sediments when subjected to cyclic loading may result in additional volumetric strain which can not be directly predicted using the recompression parameter derived from the standard consolidation tests. Furthermore, the results show that for carbonate sediments significantly high multiplying factor (/spl alpha/) is required to fit the data using recompression index compared to non-carbonate soils available in the literature.
Shambhu S. Sharma, Hackmet Joer and Noel Boylan
Keywords: carbonate sediments, cyclic loading, settlement, shear strength, pore pressure, post cyclic shakedown
Publisher: DFI