Field Tests - Rock Mechanics Based on an Anisotropic Jointed Rock Model - page 484

If β = 45°, the following is obtained:

(15.32)

(15.34c)

(15.28)

(15.36c)

In this case,

if the rock mass behavior is transversely isotropic, the numerator and denominator in
(15.33) are zero.
To determine undisturbed rock mass in deep ground, the so-called “down-hole triaxial
test” was proposed by Tani (1999) and further refi ned by Taheri & Tani (2008a) and
Taheri (2008). However, due to the comparatively small tested rock volume this testing
method is limited to rocks where the infl uence of discontinuities on deformability and
strength needs not to be accounted for.

ν 1 cannot be calculated. Since sin2 β = cos2 β = 0.5 and Δ is equal to Δ

15.6 Gallery Tests

These tests are used to determine the deformability of rock masses by subjecting an
exploration adit or a test chamber of circular cross-section and a diameter of some
2.5 - 3 m to uniformly distributed radial loading. In the so-called “radial jacking test” the
radial pressure is applied by fl at jacks. In a “hydraulic chamber test” or “water chamber
test” the radial pressure is applied by water pressure. These tests were used several dec-
ades ago for the design of pressure tunnels and shafts (Lauffer & Seeber 1961) as well as
for the design of concrete dams (Wallace et al. 1968). However, they are expensive and
time-consuming and have not been used for a long time, having been replaced by more
economic tests such as borehole expansion tests, plate loading tests and fl at jack tests.
The load measurement equipment comprises load cells, and the displacements due to
the applied load are measured at the contour of the adit and within the rock mass via
single- or multiple-point rod extensometers in several directions. Extensometers and
load cells will be described in Sections 17.4.1 and 17.6, respectively.