GEOGRID BOND LENGTH

By Date

14.12.01

Checked Date

References

References/ Results

HA 68/94: Design Methods for the Reinforcement of Highway Slopes by Reinforced SoilTable 1, Tensar

1. Reinforcement Rupture Strength56.32 kN/m 40RE

1.06 Gravel and crushed rock <125mm, Table 2a Tensar1.00 Section 3.6 Tensar1.26 Section 3.6 Tensar

= 42.17 kN/mMaximum tensile force that can be sustained in the long term by geogrid

2. Pull Out Resistance

Design soil parameters = 38.00.0 kPa

Factor of Safety = 1.5= 27.5= 0.0 kPa

0.521

0.9= 1.8

20.09.8

H= 2.9 m1.9 m

Depth to water table = 1.0 m

Height, H

Results

Average depth of tensar layer, from upper to lower layer, see enclosed sketchOverburden above tensar grid

42.17 kN/m

For Tensar grid 40RE

Grid 1 1.70 27.1 1.66Grid 2 2.00 30.2 1.49Grid 3 2.30 33.2 1.35 Grid 1 1.66Grid 4 2.60 36.3 1.24 Grid 2 1.49

Grid 3 1.35Design bond length is length of geogrid required to fully mobilise strength. Grid 4 1.24

Tensar: The Design of Reinforced Soil Structures using Tensar Geogrid, March 1996 for partial factors

Mechanical damage factor during installation

Pc = Creep Limited Strength at 10oC for

fd =

fe = Environmental factor,

chemical & biological effects

fm =

Pdes

= Pc/ (f

d.f

e.f

m)

Factor to cover variabilities and uncertainties in strength

Pdes

= p. L

e.('

n tan'

des +c'

des)

'crit

= o

c'crit

=

f'des

= tan-1(tan'crit

/FoS) o

c'des

= c'crit

/FoStan'

des =

Le = Minimum length of geogrid beyond slip surface to mobilise full strength of Tensar,

Pdes

. This is confirmed by Slope/W

Le = P

des /(

p.('

n tan'

des +c'

des))

Wherep = 2.

=

Coefficient of interaction, P13 Tensar

soil = kN/m3

water

= kN/m3Density of embankment soil

Hw =

:. For use in Slope/W anchor load =h

x =

hx, m

x, kN/m3 L

e, m

Minimum length of tensar beyond slip to mobilise full design strength of tensar

Minimum length for full bond

Grid 1

Grid 2

Grid 3

h1

WT

h2

h3

Slip Surface

Height of water table, H

w

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