Environmental Engineering Reference
In-Depth Information
FIGURE 9.81
Same cut as in
Figure 9.80,
but at a
different station. Wedge failure along
dipping joints.
convex nose form at (a) and a cut made there will be stable at a much steeper angle than
at (b), where runoff is concentrated in the swale or concave form. Runoff and seepage at
(c) are less severe than at (b) but still a problem to be considered. Natural slides, ava-
lanches, and flows usually will not occur at (a), but rather at (b) and (c), with the highest
incidence at (b) (see
Figure 9.89
and
Figure 9.90)
.
Location of Cut on Slope
Cuts in level ground or bisecting a ridge perpendicular to its strike will be stable at much
steeper inclinations than cuts made along a slope, parallel to the strike (side-hill cuts). The
side-hill cut in
Figure 9.87
intercepts seepage and runoff from upslope and will be much
less stable on its upslope side than on its downslope side where seepage is directed away
from the cut. The treatment to provide stability, therefore, will be more extensive on the
upslope side than on the opposite side.
The significance of cut locations along a steeply inclined slope in mountainous terrain in
a tropical climate is illustrated in
Figure 9.88.
A cut made at location 1 will be much less sta-
ble than at location 3, and treatment will be far more costly because of differences in runoff
and seepage quantities. River erosion protection or retention of the cut slope at 1 can be
more costly than the roadway itself. Retention would not be required at 3 if a stable cut
angle were selected, but might be required at 2 together with positive seepage control.
