ABSTRACT: As larger ships and floating offshore structures are, and rougher the marine environment becomes nowadays, a drag embedment type anchor of more stable performance and higher holding power is requested。 This paper describes an experimental study of the drag embedding motion and the resultant holding force of three types of drag embedment type anchor model (HALL, AC-14, SEC POOL-N, scale 1/10)。82149

KEY WORDS: Drag embedment type anchor (DEA); Embedding motion; Holding power; Embedment depth; Fluke; Failure wedge; Soil heave。

INTRODUCTION The basic understanding of the embedding motion and the holding power of drag embedment type anchors (DEA) is necessary to the development of DEA of more stable performance and higher holding power, although  the selection of anchoring system depends mostly on the traditional intuitive way of using “Equipment No。” table and most recent studies focus only on deep water mooring of floating offshore structures。

This paper describes an experimental study of the embedding motion and the resultant holding force of three types of DEA model。 Their relations are analyzed with respect to the anchor geometry and the soil characteristics。

Fig。 2 AC-14 type (H。H。P。) (KS, 2006)。

Fig。 1 HALL type (KS, 2006)。

Corresponding author: Hyun-Kyoung Shin

e-mail: hkshin@ulsan。ac。kr

Fig。 3 SEC POOL-N type (H。H。P。) (House, 2002)。

DRAG EMBEDMENT TYPE ANCHOR

DEA, which is one of effective and widely applied anchors for ships and floating offshore structures including wind turbines, accomplishes the required holding force by its embedding motion, when dragged horizontally。

Three  types  of  DEA  (HALL,  AC-14,  SEC   POOL-N,

scale 1/10) shown in Figs。 1~3 are generally applied to floating offshore structures and commercial  vessels nowadays on both hard and soft seafloor。

DRAG EMBEDMENT TEST

DEA model

Eight sets of DEA model are shown in Fig。 4 and Tables 1~2。

Fig。 4 Anchor geometry and effective area (Lee et al。, 2011)。 Table 1 Anchor geometry。

Table 2 Effective area。

TYPE W (kgf) As (mm2) Af (mm2)

HALL 6000 8058 10010

9350 12770 13852

12300 13485 16148

AC-14 4500 5619 21802

6975 7503 28320

9225 10196 34502

POOL-N 6975 6541 29836

9225 7748 35744

As : Area of shank

Af : Area of fluke

Model test

The drag embedment model test is carried out in the test tank (L✕B✕H=4000✕900✕900mm) shown in Fig。 5 with both hard (sand) and soft (mud) seafloor。 Also, anchor embedment depths and holding forces are measured by the ruler and the load cell, respectively, located on wire between the winch and the upper sheave。

Fig。 5 Test tank。

Tank : L✕B✕H (mm)= 4000✕900✕900

-Load cell : strain gauge (S-BEAM) type, 200 kgf, output 2。0±0。005 mV/V