Intact rock:
deformability, strength
and failure
6.1 Intact rock
The two main mechanical components of a rock mass are (a) the intact
rock material, and (b) the fractures, e.g. the faults, shear zones, joints
and bedding planes. This chapter is concerned with the mechanical
properties of the unfractured rock.
Sample of
intact rockSamples of the intact rock can be obtained from surface outcrops or
from borehole cores obtained during a site investigation. Using a coring
drill bit, a cylindrical sample of the intact rock can be obtained from
boreholes as shown in Fig. 6.1.
The testing of intact rock, which has been developed from the 1960s
to the present day, has concentrated on the testing of rock cylinders
because cylindrical rock cores are produced during site investigation
drilling. The intact rock can be tested in compression, tension or shear,
or a combination of these. For rock mechanics and rock engineering, we
are interested in the deformability, strength and failure properties of rock
under different loading conditions.
A force-displacement curve obtained during the uniaxial compressive
testing of an intact rock specimen of marble is shown in Fig. 6.2 '.