Environmental Engineering Reference
In-Depth Information
Ditch
Interceptor trench drain, sealed
Embankment of relatively
impervious materials
Seepage
Free-draining blanket or
traverse drains
Discharge collected at low point
and directed down slope
FIGURE 9.112
Proper drainage provisions for a side-hill fill.
potentially unstable upper soils, which are often creeping on moderately steep to steep
slopes, to a depth where stronger soils are encountered, and to place the free-draining
blanket over the entire area to be covered by the embankment. Discharge should be col-
lected at the low point of the fill and drained downslope in a manner that will provide ero-
sion protection.
Transverse drains
extending downslope and connecting with the interceptor ditches ups-
lope, parallel to the roadway, may provide adequate subfill drainage where anticipated
flows are low to moderate.
Retaining structures
may be economical on steep slopes that continue for some distance
beyond the fill if stability is uncertain (see
Figure 9.125)
.
Corrective
After the initial failure stage, subhorizontal drains may be adequate to stabilize the
embankment if closely spaced, but they should be installed during the dry season since
the use of water to drill holes during the wet season may accelerate total failure. An alter-
native is to retain the fill with an anchored curtain wall (see
Figure 9.128)
.
After total failure, the most practical solutions are either reconstruction of the embank-
ment with proper drainage, or retention with a wall.
9.4.6
Retention
Rock Slopes
Methods Summarized
The various methods of retaining hard rock slopes are illustrated in
Figure 9.113
and
described briefly below.
Concrete pedestals are used to support overhangs, where their removal is not
practical because of danger to existing construction downslope, as illustrated in
●
Rock bolts are used to reinforce jointed rock masses or slabs on a sloping surface.
●
Concrete straps and rock bolts are used to support loose or soft rock zones or to
reduce the number of bolts as shown in
Figure 9.115
and
Figure 9.120.
●
Cable anchors are used to reinforce thick rock masses.
●
Wire meshes, hung on a slope, restrict falling blocks to movement along the face
(
Figure 9.116)
.
●
Concrete impact walls are constructed along lower slopes to contain falling or
sliding blocks or deflect them away from structures (see
Figure 9.16).
●
Shotcrete
(
Figure 9.117)
is used to reinforce loose fractured rock, or to prevent
weathering or slaking of shales or other soft rocks, especially where interbedded
●
