Civil Engineering Reference
In-Depth Information
The volume of rock blocks can be better estimated on the basis of the number of dis-
continuity sets as well as the average orientation and spacing of discontinuities. For a
rock mass with three discontinuity sets D1, D2 and D3, the block volume can be calcu-
lated as (Palmström 1995)
(13.21)
where s
Di
is the spacing of set Di and
γ
ij
is the angle between sets Di and Dj, as illustrat-
ed in Fig. 13.31. Thus, for an orthogonal discontinuity system, the block volume
is
simply
Figure 13.31
Block volume of a rock mass with three discontinuity sets according
to Palmström (1995)
The setup of discrete models requires the evaluation of block size distributions. In order
to reconstruct three-dimensional block size distributions from two-dimensional meas-
urements, stereographical methods were reported in Beyer & Rolofs (1981a), Beyer &
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