Fig。 26 Anchor embedment motion。

Fig。 27 Simplified anchor embedment motion。

1st stage : At the first stage of anchor being dragged, anchor fluke tends to rotate and to be embedded into soil by soil resistance on the tripping palm and weight of soil accumulated over the fluke。

2nd stage : As the anchor fluke rotates with embedment to its max。 angle (35° for AC-14, 42° for HALL and POOL-N),

the anchor shank is going to rotate and to be embedded to the force equilibrium state。

3rd  stage : After the force equilibrium of anchor drag force to

soil resistance is established, the anchor is dragged without further embedment, and the max。 holding  force of DEA is acquired at this stage。

ANCHOR HOLDING FORCE

Conventional marine anchor are characterized by

a。Shallow embedment due to large shank width

b。Development of soil heave due to large fluke wedge angle

c。Bi-directionally embedment due to fluke rotation

d。Holding force depends on the weight of anchor F=W·N (1)

W : Weight of anchor

N : Bearing capacity factor

Newly developed offshore anchor are characterized by

a。Deep embedment due to small shank width (plated dual shank)

b。No development of soil heave due to small fluke wedge angle (corrugated plate fluke)

c。One directional embedment due to fixed fluke论文网

d。Holding force depending on the soil weight of failure wedge in Fig。 28。 (Neubecker and Randolph, 1996 b)

F=A·ρg·d·N (2)

ρ : Density of wet soil

g : Acceleration of gravity

d : Depth of fluke

N : Bearing capacity factor

Fig。 28 Failure wedge (Vryhof, 2010)。

Development of soil heave in Fig。 29 affects the soil weight of failure wedge (Neubecker and Randolph, 1996 a)。

Fig。 29 Development of soil heave。

Based on the test results, the anchor holding force can be persified by that in each stage (Fig。 30)

F1 : Initial drag force

F2 : Final drag force of stage 1 and initial drag force of stage 2 F3 : Final drag force of stage 2 (max。 holding force)

Fig。 30 Simplified curve of drag force。 Table 5 Drag force of each stage (sand)。

Table 6 Drag force of each stage (mud)。

TYPE W (kgf) F1 (kgf) F2 F3

HALL 6000 14 19 52

9350 16 22 74

12300 19 30 86

AC-14 4500 8 12 62

6975 10 15 77

9225 13 20 96

POOL-N 6975 10 12 111

9225 12 16 114