FLOOD03439

• County: Statewide
• Basin: Statewide
• Title: Design of Sheet Pile Walls
• Date: 3/31/1994
• Prepared By: US Army Corps of Engineers
• Floodplain - Doc Type: Educational/Technical/Reference Information

.

Chapter 4
System Loads

4-1. General

The loads governing the design of a sheet pile wall arise
primarily from the soil and waler slllTOunding the wall
and from other influences such as surface surcharges
and extemalloads applied directly 10 the piling. ClIITenl
methodologies for evaluating these loads are discusSed
in the following paragraphs.

4-2. Ealth Pressures

Earth pressures reflect the stale of stress in the soil
mass. The concepl of an earth pressure coefficien!, K.
is oflen used 10 describe !his stale of stress. The earth
pressure coeffICient is defined as the ratio of horizontal
stresses 10 the vertical stresses at any depth below the
soil surface:

Oh
K-_
o.

(4-1)

.

Earth pressures for any given soil-sllUclure syslem may
vary from an initial slale of stress referred 10 as at-res(,
K . 10 minimum limil stale referred 10 as active, K A' or
o .
10 a maximum limil stale referred 10 as pasSIve. Kp.
The magnilUde of the earth pressure exerted on the WlI11
depends, among other effects. on the physical and
strength properties of the 'soil, the inleraction at the
soil-SIrUcIure inlerface. the ground.waler conditions, &lid
the defonnations of the soil-suuclUre syslem. These
limil states are delennined by the shear strength of the
soil:

'Cf - C + ontan+

(4-2)

where

tr and o. = shear and normal stresses on a failure
plane

c and . .. shear strength panunelen of the soil.
cohesion. and angle of inlernal friction.
respeclively (Figure 4-1)

.

a. AI-reST pressures. At.rest pressure refeIS 10 a
slate of stress where there is no lateral movemenl or

EM 111(1.2.2504
31 Mar 94

strain in the soil mass. In this case, the lateral earth
pressures are the pressures thaI exi.sled in the gro~
prior 10 inslailation of a wall. ThIS stale ?f stress IS
shown in Figure 4-2 as cilde 0 on a Mohr diagram.

b. Active pressures. Active soil pressure is the mini-
mum possible value of horizontal earth pressure at any
depth. This pressure develops when the walls move or
rolate away from the soil allowing the soil 10 expand
horizonlal1y in the direction of WlI11 mov~enl. ~
stale of stress resulting in active pressures IS shown m
Figure 4.2 as circle A,

c. Passive pressures. Passive (soil) pressure is the
maximum possible horizontal pressure !hat can be devel.
oped at any depth from a wall moving or ~latin.g
Ioward the soil and lending 10 compress the SOli hon-
zonlal1y. The Slate of stress resulting in passive pres-
sures is shown in Figure 4-2 as circle P.

d. Wall movements, The amounl of movemenl
required 10 develop minimum active or maximum pas-
sive earth pressures depends on the stiffness of the soil
and the heighlof the wall. For stiff soils like dense
sands or heavily oveltOl\solidated clays. the required
movemenl is relatively small. An example is shown in
Figure 4-3 which indicales !hat a movemenl of a wall
away from the fill by 0.3 perceIll of the wall height is
sufficienllo develop minimum pressure. while a move-
menl of 2.0 perceIll of the wall heighl IOward the fill is
sufficient 10 develop the maximum pressure. For all
sands of medium or higher densily. il can be assumed
!hat the movemenl required 10 reach the minimum active
earth pressure is no more than aboul 0.4 percenl of the
wall heigh!, or aboul I inch of movemenl of a
2O-foot-high wall. The movemenl required 10 increase
the earth pressure 10 ilB maximum passive value is aboul
10 times thaI required for the minimum. aboul
4.0 percenl of the wall heighl or aboul 10 inches of
movemenl flll'" a 2O-fool-high wall. For loose sands. the
movemenl required 10 reach the minimum aclive or the
maximum passive is somewhat larger, The classical
design pocedures desaibed in !his chapler aSsume !hat
the sheeI pile walls have sufficienl flexibility 10 produce
the 1imi1 stale, active or passive earth pressures. A
melhod 10 accounl for inlennediate 10 exlreme values of
earth pressure by soil-struclure interaction analysis is
presenled in Chapter 7,

e. Wall friction and adhesion. In addition 10 the
horizonlai motion. relative vertical motion along the
wall soil inlerface may resull in vertical shearing

4-1