Laboratory Tests - Rock Mechanics Based on an Anisotropic Jointed Rock Model - page 446

Fig. 14.24 (lower) shows the results of slake durability tests on different argillaceous
rocks (Gamble 1971). It can be seen that the slake durability index of a siltstone after
five cycles is still 100% while that of a mudstone after two cycles reduces to approxi-
mately zero.
A further index test intended to assess the resistance of argillaceous rocks to disinte-
grating in water and aqueous solutions, based on alternating wetting, was conceived by
Mederer (1985). The test setup illustrated in Fig. 14.25 consists of a wire cage with a
mesh size of 0.8 mm hanging on a crank, a container filled with a slaking liquid and a
motor drive capable of rotating the crank.

Figure 14.25 Test setup for the investigation of disintegration resistance of intact rock (Mederer 1985)

Initially, a sample with a weight of approx. 100 g is placed into the wire cage. After-
wards the crank is rotated and the wire cage with the sample is immersed into the water
bath and subsequently lifted with a frequency of 72 rpm. As a consequence of alter-
nating wetting, fragments of intact rock finer than the mesh size pass through the wire
cage into the water bath. At regular time intervals the test is interrupted and the residual
mass of the sample within the wire cage is weighed. The residual mass relating to the
mass before the test as a function of time serves as a measure of disintegration resis-
tance. The results of corresponding tests on argillaceous rocks using water and brine as
slaking liquids are reported in Mederer (1985) and Pierau et al. (1993).

14.8 Abrasiveness

Abrasiveness of rock may be defined as its potential to cause wear to excavation
tools. Different types of tests have been developed to determine abrasiveness of
rock. Some of these tests have been adapted from abrasiveness testing of concrete,