The Dimensioning of Dowels for the Stabilization of Potentially Unstable Rock Blocks on the Walls of Underground Chambers

The analysis of dowels (non pre-stressed passive reinforcements) for the stabilization of potentially unstable rock blocks due to sliding is one of the most interesting problems concerning the static of underground rock chambers. The stabilizing force produced by dowels is not in fact known a priori and it depends on the dowel–rock interaction. The parameters that influence the problem are not only the geometrical ones of the dowel, but also the mechanical characteristics of the rock and the orientation of the displacement vector of the block. A detailed study of the dowel–rock interaction has been carried out in this work. This analysis is able to lead to the evaluation of the axial and shear forces in the dowel in correspondence to the crossed discontinuity of the block. The vectorial composition of these two forces constitutes the stabilization force of the dowel. An extensive parametric analysis then made it possible to determine the great variability of the stabilization force of the dowel in function of the influential parameters of the problem. The graphics that were obtained can be considered a useful design instrument as they quickly allow the dimensioning of the dowels to be done to reach the required safety factor for the rock block.