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SHEET PILE WALLSSHEET PILE WALLS
generally used for retaining shallow generally used for retaining shallow heights of soilheights of soil wharfs, key wallswharfs, key walls temporary structures for excavation temporary structures for excavation (eg. dredging)(eg. dredging)
From McCarthy, 6From McCarthy, 6thth Edition Edition
Cantilever Sheet Pile WallsCantilever Sheet Pile Walls stability depends on passive resistance stability depends on passive resistance
developed below the lower soil surfacedeveloped below the lower soil surface failure is by rotation about a point O near failure is by rotation about a point O near
bottom of wallbottom of wall
Depth of embedment, d
d
Active E.P.
O Passive E.P.
fixity
a fixing moment is provided by the extra a fixing moment is provided by the extra depth below point O to prevent rotationdepth below point O to prevent rotation
Generally, design is based on a simplified but Generally, design is based on a simplified but equivalent approach: the fixity provided equivalent approach: the fixity provided previously is replaced by a resisting force, R previously is replaced by a resisting force, R at point C which is just below point Oat point C which is just below point O
d
Active E.P.
C
Passive E.P.
R
Danish RulesDanish Rules
a factor of safety, Fa factor of safety, FPP is applied to the is applied to the passive resistance in front of the wallpassive resistance in front of the wall
take moments about C to calculate dtake moments about C to calculate d then, increase d by 20% (empirical)then, increase d by 20% (empirical) finally, check that the passive finally, check that the passive
resistance provided by the extra 20% resistance provided by the extra 20% is is >> R, where R = R, where R = PPHH
Free Earth SupportFree Earth Support
Determine the depth of embedment, d by Determine the depth of embedment, d by taking moments about A (taking moments about A (MMAA = 0, apply F = 0, apply FPP))
Find tension, T from Find tension, T from FFHH = 0 (don’t apply F = 0 (don’t apply FPP)) Constraints: failure wedges must not overlapConstraints: failure wedges must not overlap
b b >> ½½ddaa
d
Active E.P.
Passive E.P.
T
no fixity
A
tie rod
anchor wall
45° + /2
45° - /2b
da
