Geosynthetics October/November 2020 - 14

Reinforced embankments for the causeway for a North Wales bridge project

PROJECT:

PONT BRIWET
TR13-518 V3
PROJECT:
PONT BRIWET
DATE:
22/07/2013
TR13-518 V3
DATE:
22/07/2013
RESULTS - ANALYSIS WITH RESSA
RESULTSCH240
- ANALYSISEmbankment
WITH RESSA- access road
SECTION
SECTION CH240

Embankment - access road

Loading

Nominal value
Factor
(kPa)
Nominal
Factor
368 value
1.35
(kPa)
368
1.35
368
258
1.35
368
1.35
258
258
1.35
NA
NA
258
1.35
NA
NA
5.20 m OD
1.10 m OD
5.20 m OD
4.10m
1.10 m OD
4.25
4.10m
1.00 m
4.25 m OD
1V:2H
1.00 m
3 layers Tenax HM3 @ 300mm ; L = 20m (tbc)
61V:2H
layers Tenax TT045 @ 500mm ; L = 10 m (tbc)
3 layers
Tenax- CH240)
HM3 @ (tbc
300mm
; L = 20m (tbc)
50
m (CH190
for quantities)
6 layers Tenax TT045 @ 500mm ; L = 10 m (tbc)
50 m (CH190 - CH240) (tbc for quantities)
Temporary access road - causeway

Loading
Rig
(1)
Rig (2)
Rig (1) (1)
LR1100
Rig (2) (2)
LR1100
LR1100
(1)
LTM
1750
LR1100 (2)
LTMlevel:
1750
Top
Toe level:
Top level:
Height:
Toe level:
Water
level:
Height: surcharge
Distance:
Water
level:face:
from
slope
Distance: surcharge
Slope:
from slope face:
Reinforcement:
Slope:
Reinforcement:
Assumed
length:

4a
Assumed length:
SECTION CH380
(CH380 - CH440)
SECTION CH380
(CH380 - CH440)
Loading
Loading
Rig
(1)
Rig (2)
Rig (1) (1)
LR1100
Rig (2) (2)
LR1100
LR1100
(1)
LTM
1750
LR1100 (2)
LTMlevel:
1750
Top
Toe level:
Top level:
Height:
Toe level:
Water
level:
Height: surcharge
Distance:
Water
level:face:
from
slope
Distance: surcharge
Slope:
from slope face:
Reinforcement:
Slope:
Reinforcement:
Assumed
length:
Assumed length:

Distance to edge of emb
D = 1.00m
to edge of
Track Length Distance
FS
FSemb
D = 1.00m
(m)
Slope 1:1.5
Slope 1:2
Track
Length
FS
FS
2.95
0.96
1.03
(m)
Slope
1:1.5
Slope 1:2
0.80
1.11
2.95
0.96
1.03
4.30
1.06
0.80
1.11
0.90
1.28
4.30
1.06
NA
0.90
1.28
NA

Temporary access road - causeway

Distance to edge of emb
D = 1.00m
to edge of
Track Length Distance
FS
FSemb
D = 1.00m
(m)
Slope 1:1.5
Slope 1:2
Track
Length
FS
FS
2.95
0.97
1.02
(m)
Slope
1:1.5
Slope 1:2
0.80
1.12
2.95
0.97
1.02
4.30
1.07
0.80
1.12
0.90
1.31
4.30
1.07
NA
0.90
1.31
NA

Nominal value
Factor
(kPa)
Nominal
Factor
368 value
1.15
(kPa)
368
1.15
368
258
1.15
368
258
1.15
258
1.15
NA
NA
258
1.15
NA
NA
3.20 m OD
1.062 m OD
3.20 m OD
2.14
1.062mmOD
OD
2.36
2.14 m
1.00 m
2.36 m OD
1V:2H
1.00 m
3 layers Tenax HM3 @ 300mm ; L = 20m (tbc)
1V:2H
3 layers Tenax TT045 @ 500mm ; L = 10 m (tbc)
3 layers
Tenax- CH440)
HM3 @ (tbc
300mm
; L = 20m (tbc)
60
m (CH380
for quantities)
3 layers Tenax TT045 @ 500mm ; L = 10 m (tbc)
60 m (CH380 - CH440) (tbc for quantities)

4b

FIGURE 4a and 4b Results: Stability analysis Section CH240 (4a) and CH380 (4b)

14

fines, and the embankment fill was
designed with a locally modified Class
6N material (classifications according to
the Specifications for Highways Works,
Series 600).
*	 Reinforced fill properties:
¶	 Class 6B: Selected coarse granular
material used for starter layer,
with no fines (Particle sizes: 11.8
inches (300 mm) to 4.9 inches
(125 mm)
¶	 Class 6N: Selected well-graded
granular material to use for
embankment fill
¶	 Friction angle Φ'=40˚
¶	 Unit weight γ=129 pounds per
cubic foot (20 kN/m3)
¶	 Cohesion C'=0 psf (0 kPa)
Ground conditions in the estuary comprised deep loose sands over dense gravels
incorporating cobbles overlying rock.
*	 Foundation soil properties:
¶	 MD Sand
¶	 Friction angle Φ'=33˚
¶	 Unit weight γ=122 pounds per
cubic foot (19 kN/m3)

Reinforced embankments
Design standards
The reinforced embankments were
designed based on the limit equilibrium
analysis in accordance with BS80061:2010 for the internal stability and
Eurocode 7 (BS EN 1997-1:2004) for
the global stability. We used the method
from Rowe and Soderman (1985) to
estimate the stability of a reinforcement
embankment for bearing capacity and
the methods of reinforcement proposed
by Giroud, Holtz and Bonaparte (1985),
modified here in conjunction with the
properties of the geogrids (Figure 5).
For the working platforms, we used
the BRE470 guidance with a modified
method based on bearing capacity and
loading distribution to incorporate the
biaxial geogrids for reinforcement.

Geosynthetics | October November 2020

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Geosynthetics October/November 2020

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