Rock classification - Geotechnical Investigation and Design Tables - page 32

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This table is appropriate for field assessment. Detailed testing on rock strength
(Table 6.7) show that rock strength can vary between intact samples of SW and
FR weathered rock.

3.5 Colour
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Colour Charts are useful for core photography.

Table 3.5 Colour description.

Parameter Description

Tone Light/dark/mottled

Shade Pinkish/reddish/yellowish/brownish/greenish/bluish/greyish

Hue Pink/red/yellow/orange/brown/green/blue/purple/white/grey/black

Distribution Uniform/non - uniform (spotted/mottled/streaked/striped)

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For core photographs ensure proper lighting/no shadows and damp samples to
highlight defects and colours.

3.6 Rock structure
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The rock structure describes the frequency of discontinuity spacing and thickness
of bedding.

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The use of defects descriptors typically used in place of below individual
descriptors.

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Persistence reflects the joint continuity.

Table 3.6 Rock structure.

Rock structure Description Dimensions

Thickness of bedding Massive 2.0 m >

Thick - bedded 0.6 to 2.0 m

Mid - bedded 0.2 to 0.6 m

Thin - bedded 0.06 m to 0.2 m

Very thinly bedded/laminated 0.06 m <

Degree of fracturing/jointing Unfractured 2.0 m >

Slightly fractured 0.6 to 2.0 m

Moderately fractured 0.2 to 0.6 m

Highly fractured 0.06-0.2 m

Intensely fractured 0.06 m <

Dip of bed or fracture Flat 0 to 15 degrees

Gently dipping 15 to 45 degrees

Steeply dipping 45 to 90 degrees

Persistence Very high 20 m >

High 10-20 m

Medium 3-10 m

Low 1-3 m

Very low 1m >