Components of suction caisson capacity measured in axial pullout tests.pdf

Components of suction caisson capacity measured in axial pullout tests Adam M. Lukea, Alan F. Rauchb, Roy E. Olsonc,*, Elliott C. Mechamd aGroundwater Services, Inc., 2211 Norfolk, Suite 1000, Houston, TX 77098, USA bFuller Mossbarger Scott May Engineers, Inc., 1409 North Forbes Road, Lexington, KY 40511, USA cDepartment of Civil Engineering, The University of Texas at Austin, 1 University Station C1792, Austin, TX 78712, USA dFoundation Engineering, 7420 SW Hunziker Road, Suite A, Portland, OR 97223, USA Available online 15 December 2004 Abstract Suction caissons are the foundation of choice for offshore structures in deep water. Systematic study of caisson behavior is relegated to the laboratory due to the high cost of full-scale testing. Our laboratory caisson was installed in normally consolidated clay using dead weight and suction. Tensile axial capacity was measured with the top cap vented or sealed, and with the soil undrained or drained. For the common case of rapid pullout with a sealed top, the test results indicate an external side resistance factor (a) of 0.5–0.8 and a reverse end bearing factor (Nc) of 13–21. q 2004 Elsevier Ltd. All rights reserved. Keywords: Suction caissons; Offshore foundations; Pullout capacity; Tensile loading; Prototype tests; Normally consolidated soil 1. Introduction A suction caisson is a closed-top steel tube that is lowered to the seafloor, allowed to penetrate the bottom sediments under its own weight, and then pushed to full depth with differential pressure produced by pumping water out of the interior. Suction caissons are an attractive alternative for providing anchorage for offshore facilities because they can beOcean Engineering 32 (2005) 878–891/locate/oceaneng0029-8018/$ - see front matter q 2004 Elsevier Ltd. All rights reserved. doi:10.1016/j.oceaneng.2004.10.007 * Corresponding author. E-mail addresses: amluke@ (A.M. Luke), arauch@ (A.F. Rauch), olson@ (R.E. Olson), mechamec@ (E.C. Mecham). A.M. Luke et al. / Oc