Questions 10.1 -1 0.1 0:
anisotropy and
inhomogeneity
Q1O.I On the rock mass photograph (see Fig. QlO.l), identify ex-
ample features that indicate that the rock mass is more DIANE than
CHILE.
Q10.2 With reference to the photograph in Fig. QlO.1, explain why
inhomogeneity and anisotropy can be related.
470.3 The following data are pairs of point load strength (PL) and
uniaxial compressive strength (LICS) values for a particular rock type.
UCS (MPa) 52.4 60.7 44.6 66.6 47.6 56.3 61.5 48.2 49.6 47.2 56.7 48.4 61.5 52.9
PL (MPa) 2.51 2.87 2.14 3.04 2.31 2.64 2.90 2.21 2.25 2.18 2.55 2.23 2.75 2.55
We wish to correlate these strength values, and can do so either in
the form PL = an, + b or in the form CJ, = cPL + d. On the basis of
the best independent variable, which of these forms is appropriate?
Determine values for the appropriate constants (i.e. either a and b, or c
and d).
470.4 Imagine that a new index test for determining the tensile
strength of specimens of intact rock is under development in the Rock
Mechanics Laboratory at Imperial College. This test involves bonding a
steel rod to the surface of a specimen with high strength adhesive, and
then measuring the tensile load required to pull the rod together with
a small piece of rock away from the main block of rock. Four test con-
figurations are under consideration, and for each of these a theoretical
relation between rock strength and pull-off force has been developed.
Test results for the four configurations, together with the appropriate
theoretical relation, are given below. The first row in each table is the
load measured in the new test. The second row in each table is the tensile
strength of the rock as measured by a standard method.
Classify each configuration in terms of accuracy and precision, and
hence recommend which configuration(s) should be retained for further
development.