Civil Engineering Reference
In-Depth Information
Table II.11
Seepage quantities in filled discontinuities
Seepage
rating
Description
I
The filling materials are heavily consolidated and dry,
significant flow appears unlikely due to very low
permeability.
II
The filling materials are damp, but no free water is
present.
III
The filling materials are wet, occasional drops of water.
IV
The filling materials show signs of outwash, continuous
flow of water—estimate l
/
min.
V
The filling materials are washed out locally,
considerable water flow along out-wash
channels—estimate l
/
min and describe pressure that is
low, medium, high.
VI
The filling materials are washed out completely, very
high water pressures experienced, especially on first
exposure—estimate l
/
min and describe pressure.
Table II.12
Seepage quantities in tunnels
Rock mass (e.g. tunnel wall)
Seepage rating Description
I
Dry walls and roof, no detectable seepage.
II
Minor seepage, specify dripping discontinuities.
III
Medium inflow, specify discontinuities with continuous flow
(estimate l
/
min
/
10 m length of excavation).
IV
Major inflow, specify discontinuities with strong flows
(estimate l
/
min
/
10 m length of excavation).
V
Exceptionally high inflow, specify source of exceptional flows
(estimate l
/
min
/
10 m length of excavation).
rapidly. Descriptions of seepage quantities are
given in Table II.12.
be assessed from the points of view of sur-
face deterioration of a rock excavation, and
of overall stability.
•
A field assessment of the likely effectiveness of
surface drains, inclined drill holes, or drainage
galleries should be made in the case of major
rock slopes. This assessment will depend on
the orientation, spacing and apertures of the
relevant discontinuities.
II.3 Field mapping sheets
The
two
mapping
sheets
included
with
this
appendix
provide
a
means
of
recording
the
qualitative
geological
data
described
in
this
•
The potential influence of frost and ice on the
seepage paths through the rock mass should
be assessed. Observations of seepage from
the surface trace of discontinuities may be
misleading in freezing temperatures. The pos-
sibility of ice-blocked drainage paths should
appendix.
Sheet 1—Rockmass description sheet
describes
the rock material in terms of its color, grain
size and strength, the rock mass in terms of the
block shape, size, weathering and the number of
discontinuity sets and their spacing.
