Geosynthetics - Geotechnical Investigation and Design Tables - page 205

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The table highlights the key properties. Strength, creep, cost and resistance to
chemicals are some of the considerations.

- PET is increasingly being used for geogrids. It has an excellent resistance to

chemicals, but low resistance to high pH environments. It is inherently stable
to ultra violet light.

- PP and PE have to be stabilised to be resistant against ultra violet light.

16.4 Static puncture resistance of geotextiles
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An increased geotextile robustness required for an increase in stone sizes.

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An increased robustness is also required for the weaker subgrades.

Table 16.4 Static puncture resistance requirement (adapted from Lawson, 1994).

Subgrade strength CBR % Geotextile CBR puncture resistance (N) for maximum stone size d max

d max 100 mm d max 50 mm d max 30 mm

= = =

1 2500 2000 1500

2 1800 1500 1200

3 1200 1000 800

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Table applies for geotextiles with CBR puncture extensions ≥ 40%.

16.5 Robustness classification using the G-rating
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Drop Height) 0 . 5 . G-Rating = (Load ×

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Load (Newtons) on CBR plunger at failure.

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Drop Height (mm) required to make a hole 50mm in diameter.

Table 16.5 Robustness classification of geotextile -
G rating (Waters et al., 1983)

Classification G-Rating

Weak 600

<

Slightly robust 600-900

Moderately robust 900-1350

Robust 1350-2000

Very robust 2000-3000

Extremely robust 3000 >

- This robustness rating is used mainly in Australia. It is used to assess the

survivability during construction.

16.6 Geotextile durability for filters, drains and seals
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The construction stresses often determine the durability requirements for the
geotextile.