Engineering Rock Mechanics

Question and answers: permeability^1 5 1

Finally, we illustrate these heads in the diagram below, using shading

to identify the various flow channels in the network.

From this diagram, we can see how the head values generally decrease
from the left- to the right-hand side of the network, with the water flow
always travelling in the direction from the boundary with the highest
head to the boundary with the lowest head. However, the circumstances
may not be so clear if the apertures of the fracture sets are not the same,
as the following question illustrates.

49.6 Determine the nodal heads and hence the direction and mag-

nitude of flow in each rock mass fracture segment for the same case

as Q9.5, but with different fracture apertures, as given in the matrix

below.

Note that this matrix is symmetric, and we have suppressed the
values in the lower Ieh of the matrix. The units are millimetres.