Squeezing Rock - Rock Mechanics Based on an Anisotropic Jointed Rock Model - page 94

rock mass. The remaining slots are then filled with shotcrete to close the supporting
ring. This type of yielding support has been successfully installed in drifts of the
Konrad mine located in squeezing rock at a depth of some 1000 m (Fig. 4.4, Wittke
& Pierau 1995).
Figure 4.3 Supporting pressure as a function of radial displacement of the tunnel's contour
The load-bearing behavior of a slotted shotcrete membrane can be improved by
the installation of yielding elements between the shotcrete segments, which forces
a thrust into the shotcrete. This has a favorable effect with respect to the bending
of the segments (Pöttler et al. 2006). Different types of compression elements are
available (Schubert 1996, Schubert et al. 1999, Kovari 2005, Thut et al. 2006, Anag-
nostou & Cantieni 2007, Podjadtke 2009). As an example, the compression element
“Wabe” consists of several layers of pipe sections that are connected on top of each
other (Fig. 4.5). The properties of the compression element and thus the thrust that
are to be carried by the shotcrete segments can be adapted to the requirements by
means of the thickness and the number of pipe layers (Podjadtke 2009).