Stress Measurements - Rock Mechanics Based on an Anisotropic Jointed Rock Model - page 511

versions of the CSRI cell and the Borre probe can be applied in depths up to 1000 m
(Ljunggren et al. 2003). When using this type of cell, drill cores and images of the bore-
hole wall are essential for selecting a suitable test location. In the section to be tested the
core should not be broken and no discontinuities should be visible at the borehole wall.
Figure 16.1 Procedure of overcoring method using a triaxial cell (Wittke 1990)
Figure 16.2 Methods for determining the elastic constants of the overcore (Wittke 1990)
In a further type of cell the strain gauge rosettes are embedded into a plastic hollow cyl-
inder that is glued onto the wall of the pilot hole. Figure 16.3 shows the earliest cell of
this category, the so-called “stress tensor tube” (STT) developed by Rocha et al. (1974).
Another frequently used cell of this type was developed at the Commonwealth Scien-
tific and Industrial Research Organization (CSIRO) in Australia (Worotnicki & Walton
1976, ISRM 1987a). The so-called CSIRO hollow inclusion (HI) cell shown in Fig.
16.4 is applicable to a depth of about 150 m (Fecker 1997). Continuous data logging is