Laboratory Tests - Rock Mechanics Based on an Anisotropic Jointed Rock Model - page 408

Table 14.1 Typical values for effective porosity of intact rocks

type of rock effective porosity

n eff ⋅ 100 [%]
Farmer (1968) 1) Wittke (1990) 2)

igneous rocks plutonic rocks granite 0.5 - 4 0.15

gabbro 0.1 - 0.5 -

volcanic rocks rhyolite 4 - 6 -

porphyry - 2.5

andesite 10 - 15 -

basalt 0.1 - 3 0.13 / 6.6 / 7.6

diabase (dolerite) 0.1 - 0.5 -

sedimentary
rocks

clastic
sediments

greywacke - 0.12

sandstone 4 - 25 3.6 / 16

mudstone - 3.7

shale 5 - 30 -

chemical
sediments

limestone 5 - 20 0.11

dolomite 1 - 5 -

metamorphic rocks marble 0.5 - 4 -

quartzite 0.1 - 0.6 -

slate 0.1 - 1 3.3

gneiss 0.5 - 1.5 0.5

1) investigation method not specified
2) determined by mercury porosimetry

14.4 Deformability and Strength of Intact Rock

14.4.1 Uniaxial Compression Test
The uniaxial compression test, also called the “unconfined compression test”, is intended
to determine the deformability parameters and unconfined compressive strength of intact
rock. A representative sample comprises at least five cylindrical specimens with height-
to-diameter ratios of 1.5 to 2.5 prepared from drill core samples, each having a diameter of
D 30 mm and a minimum dimension of 10 times the maximum grain size (DGEG

1979a, ISRM 1979a, DGGT 2004b).
Because of the influence of the water content on the unconfined compressive strength,
particularly of soft rocks (Colback & Wiid 1965, Vutukuri et al. 1974, Lashkaripour
1998, Nickmann 2007, Plinninger et al. 2008), the conservation of the natural water
content of the sample before preparation of the specimens is of particular importance
(Sections 13.5.1 and 14.3).

≥