Rock strength parameters from classification and testing - Geotechnical Investigation and Design Tables - page 69

Table 6.5 UCS/Point load multiplier for weak rocks (Tomlinson, 1995; Look and Griffiths, 2004).

Rock type Weathering UCS/I s (50) Location/

ratio description

Argillite/metagreywacke DW 5 Brisbane, Queensland,Australia

8 Gold coast, Queensland,Australia

Metagreywacke DW 15 Gold coast, Queensland,Australia

Tuff DW 24 Brisbane, Queensland,Australia

SW/FR 18

Basalt DW 25 Brisbane, Queensland,Australia

Phyllite/arenite DW 9 Brisbane, Queensland,Australia

SW/FR 4

Sandstones DW 12 Brisbane, Queensland,Australia

10 Gold coast, Queensland,Australia

11 Central Queensland,Australia

Magnesian limestone 25 UCS 37 MPa average

=

Upper chalk 18 Humberside/UCS 3-8 MPa average =

Carbonate siltstone/mudstone 12 UAE/UCS 2 MPa =

Mudstone/siltstone (coal 23 UCS 23 MPa =

measures)
Tuffaceous rhyolite

10 Korea/UCS 20-70 MPa =

Tuffaceous andesite 10 Korea/UCS 40-140 MPa

=

•

A value of 10 would be recommended as a general conversion, but the values
above shown that the multiplier is dependent on rock type and is site specific.

•

Queensland has a tropical weathered profile.

6.6 Strength from Schmidt Hammer
•

There are “N'' and “L'' Type Schmidt Hammers.

•

= . +

R L 0 605 0.677 R N .

•

The value needs to be corrected for verticality.

•

Minimum of 10 values at each sample location. Use 5 highest values.

Table 6.6 Rock strength using schmidt “N'' type hammer.

Strength Low Medium High Very high Extremely high

UCS value (mpa) 6 6-20 20-60 60-200 200

< >

Schmidt Hammer

<

10 10-25 25-40 40-60

>

60

rebound value
Typical weathering XW HW MW SW FR