Effects of orientation, frequency and number of sets of discontinuities on the rock permeability before and after improvement by cement grouting

Discontinuities are the most important property of rock mass that control the permeability. Effects of orientation, frequency and number of sets of discontinuities on the permeability investigated before and after improvement by grouting using cement grout in this study. Rock samples having one, two and three cross-sets of single discontinuities and three cross-sets of discontinuities with one set having four parallel discontinuities, in different groups of various orientations (angle between planes of discontinuities and horizontal direction) of 0, 30, 45, 60 and 90 degrees in total of 20 different groups that have been preparing. The permeability of 20 group samples with different orientation, frequency and number of set of discontinuities has been measured. Discontinuities of multiple groups of samples using cement grout improved and also their permeability measured. The results show that the effect of discontinuities’s orientation on permeability changes by changing the number sets and the frequency of discontinuities. In samples having three cross-sets of perpendicular discontinuities with one set having four parallel discontinuities which have been represented jointed rock mass. Permeability is mainly affected by the orientation of the set that has four parallel discontinuities. Orientation, frequency and number of sets of discontinuities cause change in permeability about 759048 times. The permeability reduces in the range of 9-99% with the improvement of samples using cement grout injection. This indicates that the orientation, frequency and number of sets of discontinuities are very effective in reducing permeability by the injection.