Design and Installation of Suction Anchor Piles at a Soft Clay Site in the Gulf of Guinea

Abstract

Ccwwht 1995 O&hue Tec.hfm!mgyCanferewdThis papa was Pmsanbd al the 2Sth Annual OTC m I-buskx, Texas, U S A, &9 May 1G96 Thrn pap was malectad fci prewnlatmn by the OTC Program Cmnmti k4kwiw Wow cd infonmat,on con!amed !m an qMracl subin!lted by the author(s) Contents cd the paper, ac presented have nol been re.wwed by the OIMore Technobg y Conference and are s@@I M correction by tfw wthof(s). % material, qs p-enied, does MI neceuwtly Ad any postin al the Offshore Technology Conlermce w th .&kers Permms!on to c.apy IS rdncled to qn abstwl ot motmore than XX wrd8 Illustrslmrm may K4 be c++ad The ehlracl shwld co@aIn conswucws achmwladgmant C4tire and by -me paper m pfasenwd AbstractInnovative shallow suction anchor piles have been used for permanent mooring of a process and accommodation barge at an oil and gas field developed by ELF Congo in the Gulf of Guinea. The 12 mooring lines, equipped with 5m diameter and 13m high steel suction anchor piles, were successfully installed at the site in July/August 1995. The process barge is scheduled to be connected earfy 1996 for start of production. With a water depth of about 170m, the Nkossa field is the deepest in offshore Western Africa to date. The soils at the site consist of sofl normally consolidated clays, representative of deep water sites. The anchoring system design is presented, together with the description of the suction pile installation by underpressure. The monitored performance of the suction piles during installation is evaluated, including orientation and tilt at touch-down, and penetration rate during suction penetration. The installation behaviour appeared to be very smooth, and the measured penetration resistances were in perfect agreement with the predictions, thus demonstrating the reliability of the design installation method.

Shear Strength Along Inside of Suction Anchor Skirt Wall in Clay

“…When the anchor is penetrated by underpressure, however, essentially all the displaced clay is expected to move into the anchor. This assumption of soil movement is based on model test results (Renzi et al 4 , Whittle and Germaine 9 ), prototype behavior (Colliat et al 10 ), and finite element analyses (Andersen and Jostad 2 , Andersen et al 11 ).…”

Analysis of Suction Caisson Capacity in Clay

“…For typical caisson aspect ratios of 4 to 6, and loading angles of 30 degrees or greater, significant vertical movement will occur during failure. The interaction between the bearing factors, N p , and N v (for axial motion, defined as N v = F v /s u d, where F v is the axial load per unit length of the caisson shaft) followed an elliptical relationship expressed as (8) where N pmax and N vmax correspond to maximum values of N p and N v under pure lateral or axial motion (e.g values of 11.9 and π respectively for a fully rough shaft), and N po is the value of N p just as the lateral component of movement falls to zero. Flow region.…”

“…Suction caissons are now used widely in the offshore industry for anchoring systems, with applications ranging from quasihorizontal loading for catenary mooring lines (Colliat et al, 1996) to quasi-vertical loading for tension leg platforms (Andersen et al, 1993;Clukey et al, 1995). Between these two extremes, the use of suction caissons for taut wire moorings with loading angles of 30 to 50° is becoming increasingly common (Mello et al, 1998).…”

Capacity of modified suction caissons in marine sand under static horizontal loading

“…Suction caissons are also available in various water depths, especially in deep waters and have significant advantages of cost effectiveness, fast installation and reuse (Zhang et al, 2013). Consequently, suction caissons have been used widely for mooring offshore floating facilities and as foundations of offshore platforms (Colliat et al, 1997).…”