Anchored Retaining Walls

7/29/2019 Anchored Retaining Walls

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Foundation Engineering

Foundation Engineering

Prof. Mesut Pervizpour

Earth Retaining StructuresFlexible Retaining Walls:

Anchored sheet pile wallsBraced excavationsSlurr wallsStability of open cuts

For NAVFAC and other online manuals

1

(including Army Corps of Eng, & FHWA)http://www.vulcanhammer.net/download/

Anchored sheetpile (H > 3m)

Anchored Sheet Pile Wall Design:

Additional support by tieback anchors (horizontal or inclined)

H Anchor e uc on n exura s resses an a era movemen o e wa

Walls can be constructed to larger heights

Reduction in required depth of embedment D

Design principles: free-end method, fixed end method, beam on elastic foundation method

Assumptions: rigid sheet pile, rotation of the wall about tie rod level, bottom

embedment ust sufficient for stabilit takin moment b tie rod location

2


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Anchored Sheet Pile Wall Design Free Earth Support Method:

Simplified Earth Pressure Distribution for Sands

The embedment is calculated by takingmoment about O

Simplified Earth PressureDistribution

The required anchorage resistance is:

= -

aapfpo

H

FzfO

z a p

a

Pa

PzcCz

p = (Kp Ka) (D zc)

D

For desi n increase calculated D b 20-50%.

Zfoften ~ H/4

3

Find force in the tie rod.Find bending moment and pile section.

Anchored Sheet Pile Wall Design Free Earth Support Method:

Simplified Earth Pressure Distribution for Granular Backfill and

The embedment is calculated by takingmoment about O

D

Simplified Earth PressureDistribution

The required anchorage resistance is:

2

aafpo zz

FzfO Sand

= a - p

a

a

Pa

eH eH: is the

weight of backfill

p = 4c - eH

PpD and surcharge

For desi n increase calculated D b 20-50%.

Clay ( = 0)

4

Find force in the tie rod.Find bending moment and pile section.


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Anchored Sheet Pile Wall Moment Reduction

Rowes moment reduction method:

For walls in sand with.

7

Anchored Sheet Pile Wall Moment Reduction


For anchored sheet pilewalls penetrating in tocohesive soils in terms ofstability number andflexibility number.

Stability number, obtain theration of Md/Mmax for

various log values (fromthe three plots).

Generate a plot of Md/Mmax

same steps as in granularsoils (described earlier).

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Example Anchored Sheet Pile Wall in Sand:Total embedment depth of the sheet pileForce in the tie rod er meter of wallSuitable piling section

about O (tie level):

9

Example Anchored Sheet Pile Wall in Sand:

Mmax = (4.1 + 1) 167.9

Total length L of the sheet pile:

L = 10 + 6.2 = 16.2m

(4.1 + 4/3) 47.1

(4.1)(4.1/2) 23.5

(4.1)2 (4.1/3) 1.45

= 369.56 KNm/m

= 997 kip in/ft

H 265.01.53'44

Forces on the wall and the location of Mmax, x belowthe water level is shown in the figure, Equilibrium, Fx = 0:

Select the pile appropriate pilesection from the following tables

IIEI 1030

10 x = 4.1m (below water)

1.45x2 + 23.54x + 47.1 167.9 = 0X2 + 16.23x 83.31 = 0


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Example Anchored Sheet Pile Wall in Sand (Cont.):

11

Momentof

SectionModulus

Area


inertia

Example: 25ksi*46.8/12=97.5

97.5/(997/12)=1.17 0.96 0.76

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observed < Mmax calculated via. Free-earthsupport method.Rowe reduce the moment, factorsconsidered in this method:1. Dr2. Relative flexibility of pile:

Flexibility no. = H4

/ EI(H is H+D)

3. Stabilit no. for cohesive soils:

Any section plotting above the

. .S = 1.25 c /eh

4. Relative height of piling , (H/ D+H)97.5/(997/12)=1.17 0.96 0.76

dense curve would besufficient for stress. PZ27 isadequate (allowable design

Dense Curve

, .

13

From Rowes Moment Reduction Curve

Details of a Typical Anchor wall

Anchored Sheet Pile Wall:

14

(Foundation Handbook-Winterkorn/Fang)


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Details of a Typical Anchor wallAnchored Sheet Pile Wall:

15

(Foundation Handbook-Winterkorn/Fang)

Sheet Pile Anchorage:

Tie-back can be supported by deadman anchor, braced piles, cast-in-place tie rod,an e ca anc ors

Wales placed horizontally in front of

sheet piling.

Deadman Anchor

Cast-in-place

Braced Piles

ea man

16Cast-in-placeanchored tie-rod Helical Anchors


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Continuous Anchor Wall


17

Resistance of Discontinuous Anchor (deadman)


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Grouted Anchors


19


Load Capacity of Deadman Anchor:

Tu = Rp - Ra

pprox ma e a owa ecapacity of a givendeadman anchor inranular soil er unit

length of deadman:

21 dKAFS

Tpa

LF = (Pp Pa) L / FS

where FS = 1.25 1.5

A = 0.6d = depth of bottom

of deadman

Or:

Pp

Pa


=Auger hole

ressure grou anc or nsoil or rock

a

Ca = (0.7 0.9) c

K = Ko if grout is placed

z1

d

20

under pressure or KaotherwiseL


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Sheet Pile Anchorage:Location of Anchor Plates

: anc or orce e erm ne rom x =Reduce it by a FSa = 2Determine dz to bottom of plate by F = 0at the deadman:

1aapz

2

az

FSFd

'

2

ap

The anchor plate must be located outside of the active slip plane (avoiding theinteraction of wall active zone and plate passive zone):

2

452

45 tantan ozo

oa ddHL

Calculate spacing of anchors s: longitudinal spacing, ha height of anchor plate.= x

ap

a

az KK

FSF

Lds

2

'2

21

,required section modulus of the wall.

Proof testing setup andinstrumentation for threadbar


ground anchor

z1

Auger holeF = cadL + dz1LK tan

d

L

a = . . c

K = Ko if grout is placed

Under pressure or Ka

22

Dunnicliff(1988)

o erw se


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Typical Steel Work Design


23(Foundation Handbook-Winterkorn/Fang)





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Anchored Retaining Walls