Geologic Hazards - Geotechnical Engineering Investigation - page 817

TABLE 9.10
Retaining Wall Characteristics

Wall Type Description Comments

Rook-filled Constructed of nondegradable, Gradation is important to maintain free-

buttress equidimensional rock fragments with at draining characteristicsmid high friction

least 50% between 30 and 100 cm angle, which combined with weight provides

and not more than 10% passing 2-in. sleve retention. Capacity limited by φ of

(Royster, (1979). approximately=40° and

space available for construction.

Gabion wall Wire baskets, about 50 cm each side, are Free-draining. Retention is obtained from

filled with broken stone about 10 to 15 cm the stone weight and its interlocking and

across. Baskets are then stacked in rows. frictional strength, Typical wall heights

are about 5 to 6 m, but capacity is limited by

φ .

Crib wall Constructed by forming interconnected Free-draining. Height of single wall is limited

boxes from timber, precast concrete, or to on amount twice the member length.

metal members and then filling the boxes Heights are increased by doubling box sections

with crushed stone or other coarse in depth. High walls arc very sensitive to

granular material. Members are usually transverse differential settlements, and the

2 m in length. weakness of cross members precludes

support of high surcharge loads.

Reinforced A compacted backfill of select fill is placed Free-draining and tolerant of different

earth walls as metal strips, called ties, are embedded in settlements, they can have high capacity and

the fill to resist tensile forces. The strips are have been constructed to heights of at least

attached to a thin outer skin of precast 18 m. Relatively large space is required for

concrete panels to retain the face. the wall.

Concrete A mass of plain concrete. Requires weep holes, free-draining draining

gravity backfill, large excavation. Can take no tensile

wall stresses and is uneconomical for high walls.

Semigravity Small amount of reinforcing steel is used Requires weep holes, free-draining backfill, and

concrete to reduce concrete volume and provide large excavation. Has been constructed to

wall capacity for greater heights. heights of 32 m (Kulhawy, 1974).

Cantilever Reinforced concrete with n stem connected Requires weep holes and free-draining backfill;

wall to the base. The weight of earth acting on smaller excavation than gravity walls but

the heel is added to the weight of the limited to heights of about 8 m because of

concrete to provide resistance. inherent weakness of the stem-base

connection.

Counterfort A cantilever wall strengthened by the Used for wall heights over 6 to 8 m.

wall addition of counterforts.

Buttress wall Similar to counterfort walls except that the As per cantilever and counterfort walls.

vertical braces are placed on the face of
the wall rather than on the backfill side.

Anchored A thin wall of reinforced concrete is tied Constructed in the slope from the top down in

reinforced- back with anchors to cause the slope and sections to provide continuous retention of

concrete wall to act as a retaining system. the slope during construction. (All other

curtain wall A variation by Tecnosolo S. A. uses precast walls require an excavation which remains

panels as shown in Figure 9.129. open while the wall is erected.) Retention

capacity is high and they have been used
to support cuts in residual soils over 25 m
in height. Drains are installed through
the wall into the slope. See also Figure 9.127
and Figure 9.128 .

Anchored Sheet piles driven or placed in an excavated Seldom used to retain slopes because of its

steel slope and tied back with anchors to tendency to deflect and corrode and its costs,

sheet-pile form a flexible wall. although it has been used successfully

wall to retain a slope toe in conjunction with other

stabilization methods ( see Figure 9.109) .

Bored piles Bored piles have been used occasion to Height is limited by pile capacity in bending.

stabilize failed slopes during initial Site access required for large drill rig unless

stages and cut slopes. holes are hand-excavated.

Root piles Three-dimensional lattice of small- Trade name “Fondedile.” A retaining structure

diameter, cast-in-place, reinforced- installed without excavation. Site access for

concrete piles, closely spaced to large equipment required.

reinforce the earth mass.