Geosynthetics - Geotechnical Investigation and Design Tables - page 210

- For unreinforced geotextiles, impoundment height is limited to 0.6m and post

spacing to 2m.

- For greater heights, use of plastic grid/mesh reinforcement to prevent burst

failure of geotextile.

Table 16.13 Geotextile strength for varying post spacing (adapted from
Richardson and Middlebooks, 1991).

Post spacing (m) Tension in silt fence geotextile (kN/m)

H 0.5 m H 0.6 m H 0.9 m = = =

1 5 kN/m 7 kN/m 12 kN/m

1.5 N/A 10 kN/m 18 kN/m

2 N/A 12 kN/m 25 kN/m

2.5 N/A N/A 30 kN/m

16.14 Typical geotextile strengths
•

The Geotextile strength depends on the application, with the greatest strength
required below embankments founded on compressible clays.

Table 16.14 Typical geotextile reinforcement strengths (adapted from Hausman, 1990).

Application Description Fabric wide strength, kN/m Fabric modulus, kN/m

Retaining structures Low height 10-15 35-50

Moderate height 15-20 40-50

High 20-30 60-175

Slope stabilization Close spacing 10-20 25-50

Moderate spacing 15-25 35-70

Wide spacing 25-50 40-175

Unpaved roads CBR

≤

4% 10-20 50-90

CBR 2% 15-25 90-175 ≤

CBR

≤

1% 35-50 175-525

Foundations Nominal 25-70 175-350

(Increase in bearing Moderate 40-90 350-875

capacity) Large 70-175 875-1750

Embankments over C u 10 kPa 100-200 875-1750 >

soft soils C u 5 kPa 175-250 1750-3500

>

C u 2 kPa 250-500 3500-7000

>

16.15 Geotextile overlap
•

The Geotextile overlap depends on the loading and the ground conditions.

•

A 500mm minimum overlap required in repairing damaged areas.