1. Dr. S. NEELAMANI
Senior Research Scientist & Program Manager
Coastal Management Program
Environment & Urban Development Division
Kuwait Institute for Scientific Research
KUWAIT
Email: nsubram@kisr.edu.kw

2. Typical view of pipeline entering from land to sea

3. Coastal pipelines during laying

4. A lay barge for laying submarine pipeline

5. Main Pipeline along with smaller cluster pipes
during laying

6. Buoyancy chamber attachment on the pipeline
during laying

7. Offshore effluent pipeline deployed and ready for sinking into position
(See the concrete collars for stability)

8. Collar installation onto new offshore effluent outfall pipeline

9. Installation of collars during gradual
shore delivery of new pipeline

10. Submarine pipeline used for marine outfall

11. Submarine pipelines discharging effluents in the
marine environment

12. Typical cross section of a submarine pipeline with
different forces acting on it

13. FB
FB
FL
FL
FD FI
FD FI
e
e
s  c FW FP s  c FW FS
FO
FC
FC FC
ELEVATED PIPE LINE
13

14. FB
FB FB
FL
FL
FL
FD FI
FD FI FD FI
s  c B s  c Fp s  c Fp
Fs B FW
FW Fs Fs
FW
FC
FC
SURFACE or PARTIALLY BURIED PIPELINE
14

15. SWL SWL
FB
Sea Bed
FV
s  c FB s  c
FH FV
FH
FW
FW
FC
BURIED PIPELINE
FC
15

16. Armor rock
Beam
Sea bed
Sea bed
Pile
Ballasted pipe
Pile supported pipe
Hold down strap
Concrete saddle
Sea bed
Sea bed
Screw or
Explosive Anchor
Pipe Saddle Pipe Anchor
Stabilization methods for Exposed submarine pipeline
16

17. Sea bed
Trench wall
Natural fill
Buried pipe- Natural Fill
Jetted in pipe
Armor rock Tremie concrete
Back fill
Bedding
Bedding
Buried pipe- Armor Cover Buried pipe- Concrete Cover
Stabilization Methods for buried Submarine pipeline
17

18. L
Hi Sea Water Level
d
Sea Bed
What is the
Engineering & Minimum
Hydraulic Properties of D e safe Burial
the soil
Depth?
Challenging Question?

19. MINIMUM SAFE BURIAL DEPTH OF
SUBMARINE PIPELINE DEPENDS ON
 DESIGN WAVE CONDITION
 TYPE OF SEA BED MATERIAL
 ENVIRONMENTAL IMPACT OF FAILURE
 INITIAL COST
 MAINTENANCE COST
 ZONE
 CARGO
 RISK

23. ARABIAN
KUWAIT GULF

24. Sabiya Coastal Soil

25. Al-Koot Coastal Soil

26. Shuaiba Coastal Soil

27. Al-Khiran Coastal Soil

29. Hydrodynamic parameter Range Unit
Significant Wave Height and (5,1.0), (10,1.0), (15,1.0), (5,2.0), (m,s)
Peak Wave Period Combinations, (10,2.0), (15,2.0), (20,2.0), (5,3.0),
(Hs, Tp) (10,3.0), (15,3.0), (20,3.0)
Water depth at the test section, d 0.45 m m
Pipeline burial depth, e 0.0, 0.1, 0.2, 0.3 and 0.4 m
Pipe dia, D 0.2 m
Wave length, Lp at the test section 1.491, 3.883 and 6.089 m
corresponding to peak period, Tp
Relative depth of burial, e/D 0.0, 0.5, 1.0, 1.5 and 2.0 Unitless
Hs/d 0.111 – 0.444 Unitless
Hs/Lp 0.008 – 0.101 Unitless
d/Lp 0.074 – 0.302 Unitless
kd 0.465 – 1.897 Unitless
D/Lp 0.033 – 0.134 Unitless
kpa 0.103 – 0.422 Unitless
Ur 1.22 – 81.38 Unitless
Umax.SWL 0.121 – 0.505 m/s
Umax.Bed 0.048 – 0.435 m/s
KC 0.241 – 6.532 Unitless
Re 9652.54 – 87094.7 Unitless

30. Soil location
Soil Property Unit Sabiya Al-Koot Shuaiba Al-Khiran
D10 mm 0.380 0.250 0.410 0.250
D30 mm 0.570 0.275 0.570 0.275
D50 mm 1.450 0.295 0.950 0.310
D60 mm 1.700 0.310 1.500 0.330
Cu Unitless 4.470 1.240 3.660 1.320
Cc Unitless 0.500 0.976 0.528 0.917
Bulk density t/m3 1.560 1.550 1.621 1.792
Saturated density t/m3 1.850 1.855 1.948 2.130
Submerged density t/m3 0.811 0.815 0.815 1.090
Porosity Unitless 0.290 0.360 0.908 0.339
Hydraulic Conductivity, k mm/s 0.412 0.286 1.840 0.652
Angle of shearing resistance, Degree 31.460 32.110 32.110 27.010
Φ
Coefficient of friction, tan Φ Unitless 0.612 0.628 0.628 0.510
Passive earth pressure Unitless 3.183 3.269 3.269 2.664
coefficient of the soil, Kp
Remarks - Well Uniformly Almost well Uniformly
graded graded graded soil graded

31. Incident wave and
corresponding horizontal
wave forces on
the submarine pipe for
e/D = 0.0, 0.5, 1.0, 1.5 and 2.0
respectively
from top to bottom
(Al-Khiran soil,
Hi = 0.2 m, T = 2.0 s).

32. Fig. 6. Vertical wave forces on
the submarine pipe for
e/D = 0.0, 0.5, 1.0, 1.5 and 2.0
respectively from top to
bottom
(Al-Khiran soil,
Hi = 0.2 m, and
T = 2.0 s).

33. Effect of relative burial depth of
submarine pipeline on shoreward
force coefficients for four different soil
types (Hi/d=0.666, d/L=0.074).
Effect of relative burial depth of
submarine pipeline on seaward force
coefficients for four different soil
types (Hi/d=0.666, d/L=0.074).

34. Effect of relative burial depth of
submarine pipeline on downward
force coefficients for four different
soil types (Hi/d=0.666, d/L=0.074).
Effect of relative burial depth of
submarine pipeline on upward
force coefficients for four different
soil types (Hi/d=0.666, d/L=0.074).

35. Conclusions
 For all the four soil types, the horizontal force reduced
nonlinearly with increase in depth of burial; whereas,
the vertical force generally increases up to certain
depth of burial, mainly due to the significant change in
the magnitude as well as the phase difference between
the dynamic pressures in the vertical direction.

36. Conclusions
 Among the soils, well graded and high hydraulic
conductivity soil (Shuaiba soil with k=1.84 mm/s) is
good for half burial of the submarine pipeline, since
the least vertical force occurred for this soil. On the
other hand, uniformly graded and low hydraulic
conductivity soil (Al-Koot soil with k=0.286 mm/s)
attracts the maximum vertical force for half burial. On
the other hand, this type of soil is good for full burial
or further increase of burial, since it attracts less
vertical force when compared to the other soils.

37. Conclusions
 In general, if the hydraulic conductivity is high (order
of 1.84 mm/s), then varying the burial from e/D=0.5 to
1.0 or 1.5 does not provide any advantage from vertical
stability point of view, since the vertical forces are of
the same order from e/D=0.5 to 1.5. On the other
hand, for a soil with low hydraulic conductivity (Order
of 0.29 mm/s), changing the burial from e/D=0.5 to 1.5
could reduce the force more than 50%.

38. Conclusions
 In general, the horizontal wave force dictates the
stability of the submarine pipeline, if the pipeline is
placed on the sea floor since the highest horizontal
force occurs when the pipe is not buried.
 For buried pipeline, the horizontal force is not the
main issue for stability due to significant force
reduction. For the buried pipeline, the upward wave
force mainly dictates the stability of the pipeline.

39. Workout Example
Input conditions:
Steel Pipe; OD: 1.0 m; Wall Thickness:15 mm
Water depth: 2.25 m; Wave period: 6.7 s;
Design wave height: 1.6 m.
Soil Type: Four different marine soils discussed
in this paper
Pipe line purpose: Crude oil transport
Find:
a. Minimum safe burial depth
b. Surcharge required for stability for any
selected depth of burial

40. Minimum Minimum
Location e/D FSUplift Minimum FSHorizontal Minimum Safe e/D W for Was for Was for
as
Safe e/D Sliding Safe e/D Value FSUplift of FSHorizontal Satisfying
Value to Value to Consideri 1.5 (t/m) of Both
Sliding
Prevent Prevent ng Both 1.5 (t/m) FSUplift
Vertical Horizonta Vertical and
Pop-up l Sliding and FSHorizontal
Horizonta Sliding of
l Stability 1.5 (t/m)
0 1.04 0.02 0.42 1.10 1.10
0.5 e/D e/D 0.68
Sabiya 0.87 1.13 e/D in 0.68 0.09
between
1.0 0.94 10.96 between between 0.62 0.0 0.62
1.5 and
1.5 1.34 26.02 0.5 and 1.5 and 0.17 0.0 0.17
2.0
2.0 1.97 101.80 1.0 2.0 0.0 0.0 0.0
0 1.04 0.02 0.42 1.10 1.10
Al-Koot 0.5 0.78 e/D bit 0.71 e/D in 0.87 0.17 0.87
1.0 0.98 more 19.82 between e/D bit 0.54 0.0 0.54
1.5 1.44 than 1.5 85.08 0.5 and more 0.06 0.0 0.06
2.0 2.05 230.83 1.0 than 1.5 0.0 0.0 0.0
0 1.04 0.02 0.42 1.10 1.10
0.5 e/D e/D 0.46
Shuaiba 1.01 1.64 0.46 0.0
between
1.0 0.96 13.12 between 0.58 0.0 0.58
1.5 and e/D=0.5
1.5 1.42 31.87 1.5 and 0.08 0.0 0.08
2.0
2.0 2.07 78.25 2.0 0.0 0.0 0.0
0 1.04 0.02 0.42 1.10 1.10
Al-Khiran 0.5 0.92 1.54 0.60 0.0 0.60
1.0 1.01 e/D = 1.5 13.77 0.51 0.0 0.51
1.5 1.53 40.96 0.0 0.0 0.0
2.0 2.33 85.14 e/D=0.5 e/D = 1.5 0.0 0.0 0.0

41. Acknowledgements
 Kuwait Foundation for Advancement of Science
and Kuwait Pipe Industries and Oil Services
Company (K.S.C) for sponsoring this R&D work
 Kuwait Institute for Scientific Research for the
infrastructure and logistic support.