Laboratory Tests - Rock Mechanics Based on an Anisotropic Jointed Rock Model - page 403

14 Laboratory Tests

14.1 Introduction

Laboratory tests on intact rock specimens are carried out as a standard for each rock
mechanical investigation program. The samples can be taken from drill cores or expo-
sures at an early stage of the project or from excavated material during construction.

Petrographic parameters such as mineral content and grain structure of intact rock can
influence to a certain extent the macroscopic behavior of the rock mass (Section 14.2).
The determination of physical properties of rocks, such as water content, density and
porosity, is described in Section 14.3. The results of laboratory tests on rock specimens
with regard to deformability and strength (Section 14.4) in most cases are representative
only for the intact rock because of scale effects and due to the fact that the influence of
discontinuities on these properties cannot be investigated. However, the anisotropy of
intact rock also has an effect on the large-scale characteristics of a rock mass. Therefore
these tests should be evaluated whenever possible with respect to the rock's anisotropy.
Laboratory tests on discontinuities only allow the investigation of relatively small dis-
continuity surfaces (Section 14.5). In addition, there are difficulties in taking undis-
turbed samples.
Laboratory tests can also provide valuable information on rock properties such as swell-
ing, slake durability and disintegration resistance, when coming in contact with water,
or abrasiveness, when coming in contact with excavation tools. The determination of
these properties with the aid of laboratory tests is dealt with in the final three sections
of this chapter.
For a detailed description of laboratory testing methods the reader is referred to the
corresponding suggested methods and recommendations published by the ISRM
and the German Geotechnical Society (DGGT or formerly DGEG), respectively.
The suggested methods of the ISRM up to 2006 are also compiled in the so-called
“blue book” (ISRM 2007).

14.2 Petrographic Investigations

The results of petrographic investigations provide information on mineral content and
the structure of intact rock that allow the rock to be classified according to one of the
grain structure models described in Section 2.3.