W : Weight of anchor (class) Wa : Weight of model anchor Ls : Length of shank

Sf : Length of fluke

Test result

Holding force and displacement

The measured anchor holding force F to the dragged distance of each type of anchors on sand and mud seafloor can be graphically shown。 (Figs。 6~19)

X-axis : dragged distance of anchors (m), l

Y-axis : holding force (kgf), F

Fig。 6 HALL type (sand)。

Fig。 7 HALL type (mud)。

Fig。 8 AC-14 type (sand)。

Fig。 9 AC-14 type (mud)。

Fig。 10 POOL-N type (sand)。

Fig。 11 POOL-N type (mud)。

Fig。 12 HALL type, 6000 kgf。

Fig。 13 HALL type, 9350 kgf。

Fig。 14 HALL type, 12300 kgf。

Fig。 15 AC-14 type, 4500 kgf。

Fig。 16 AC-14 type, 6975 kgf。

Fig。 18 POOL-N type, 6975 kgf。

Fig。 19 POOL-N type, 9225 kgf。

Fig。 20 Max。 holding force of model anchors。

As shown in Figs。 6~19, the holding force F increases steeply after initial penetration stage of model anchors and finally converges to its max。 holding force。 The holding force and the embedment depth on mud soil are higher than those on sand soil, respectively。 It holds in all three types of anchor。 Also, Fig。 20 shows that the max。 holding force of bigger model anchors is higher than that of the smaller ones of the

same model。

The anchor embedding capability can be represented by the max。 holding power, which is defined as the ratio of the max。 holding force to its weight on Y-axis。

As shown in Fig。 21, the max。 holding powers measured at the model test differ from each other in different types of anchor and soil。

Comparison with NCEL’s anchor holding capacity

The anchor holding capacities from the model tests are plotted on the graphs prepared by NCEL in Fig。 22, and compared with each other to accredit them。

Table 3 Anchor embedment depth (sand)。

Ds : Depth of anchor pin

Df : Depth of fluke tip

Table 4 Anchor embedment depth (mud)。

Fig。 22 Comparison with NCEL’s anchor holding capacity (NCEL 1987)。

Anchor embedment depth

In order to verify the relation between the holding capacity and the embedment motion of each anchor, final depths of the anchor pin and the fluke tip are measured after each test of anchors on both sand and mud seafloor, of which mean values are described in Tables 3~4。

Soil characteristic

The particle size distribution of sand and mud used in the test, was obtained by the sieve analysis according to KS F2309 (Figs。 23~24) and the hydrometer analysis  according to KS F2302-92 was additionally made for mud’s very small particles (Fig。 25)。

Fig。 23 Particle size distribution (sand)。

Fig。 24 Particle size distribution (mud)。

Fig。 25 Particle size distribution (mud)。

As shown in Fig。 23, the soil used in the sand  test consists most of sand (around 96%), according to USCS (Unified Soil Classification System)。

Particle size - clay : ~ 0。005 mm, silt : 0。005 ~ 0。07 mm,

sand : 0。07 ~ 2 mm, gravel : 2 mm ~

The soil used on the mud test consists of clay (25%), sand (60%), and gravel (15%), as shown in Figs。 24~25。

The wet density of each soil is measured as below。

Density(ρ) : 1779 kg/m3 (sand), 1942 kg/m3 (mud)。

ANCHOR EMBEDMENT MOTION

The embedment motion can be persified by three (3) stages as in Figs。 26~27。 (Lee et al。, 2011)