Laboratory Tests - Rock Mechanics Based on an Anisotropic Jointed Rock Model - page 445

Figure 14.24 Slake durability test (ISRM 1979b)
A representative sample comprises ten pieces of intact rock each weighing ca. 50 g. Ini-
tially the sample is oven dried at 105°C. Subsequently it is placed in the drum and im-
mersed in liquid, usually 20°C warm water. For 10 minutes of rotation of the drum, the
sample pieces are allowed to disintegrate. Then, fragments of intact rock fi ner than 2 mm
pass through the drum into the trough half fi lled with the slaking liquid. The parts of
the sample remaining within the drum are dried and weighed. This wetting and drying
cycle is repeated several times. The slake durability index I dn after n cycles is defi ned as
(14.53)
where m d0 is the dry mass of the sample before the test and m dn is the dry mass of the
sample remaining in the drum after n cycles. The slake durability index is originally
calculated after the second cycle (ISRM 1979b). In DGGT (2002a) six cycles are
recommended to be carried out.