Civil Engineering Reference
In-Depth Information
(i)
massive
—few joints or very wide spacing
(ii)
blocky
—approximately equidimensional
(iii)
(iv)
columnar
—one
dimension
considerably
larger than the other two
tabular
—one dimension considerably smaller
than the other two
(v)
irregular
—wide variations of block size and
shape
(vi)
crushed
—heavily jointed to “sugar cube”
Table II.9
Block dimensions
II.2.5 Ground water
J
v
(joints/m
3
)
Description
M Seepage
•
Very large blocks
<
1.0
Water seepage through rock masses results
mainly from flow through water conduct-
ing discontinuities (“secondary” hydraulic
conductivity). In the case of certain sedimentary
Large blocks
1-3
Medium-sized blocks
3-10
Small blocks
10-30
Very small blocks
>
30
(a)
(b)
(c)
(d)
Figure II.5
Sketches of rock masses illustrating block shape: (a) blocky; (b) irregular; (c) tabular; and
(d) columnar (ISRM, 1981a).
