Geoscience Reference
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11 STABILITY OF EARTH-RETAINING STRUCTURES
Earth-retaining structures support vertical or near-vertical faces of a ground-
surface profile. Horizontal soil pressures and groundwater pressures will act on
these structures. To reduce groundwater pressure build-up (e.g. rain) proper
drainage facilities are required. If a retaining wall is caused to move towards the
supported soil, the horizontal pressures will increase. They are then referred to as
passive pressures. If the wall moves away from the soil, horizontal pressures
decrease, and are referred to as active pressures. If the wall does not move, the
horizontal pressures are said to be at-rest (or neutral). The stress state can be
expressed in terms of the coefficient of earth pressure, i.e. the ratio
v
'
, and one
distinguishes
K
p
for passive,
K
a
for active, and
K
0
for neutral stress states. In
Chapter 7 the expressions for
K
i
are elaborated. Only small horizontal
deformations, in the order of 0.1% to 1% of the height, are sufficient to invoke an
active or passive state. In practice, such deformations are quite possible.
h
'
/
masonry
sheetpile
gabions
L-wall
combi wall
geotextile
gravity walls embedded walls reinforced earth
Figure 11.1 Types of earth retaining structures
Four types of earth-retaining structures are considered in this chapter: gravity
walls, embedded walls, slurry walls, and reinforced earth walls. Three of them are
shown in (Fig 11.1). The stability of gravity walls depends largely on their own
weight (massive walls) or on the supporting soil weight (crib walls, L-walls, T-
walls, etc.). In principle, gravity walls are stiff, enforcing a rather uniform stress
state, either passive, active or neutral. Embedded walls consist of driven or placed
sheets or piles, which may be freestanding (cantilever wall), anchored or strutted.
In principle, embedded walls are more flexible, inducing a varying stress state,
depending on local deformation. Reinforced earth walls obtain their stability from
inserted reinforcements, such as strips, geotextile, gabions, nails, injection or
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