design : -Retaining walls (الجدران الاستنادية) - steel sheet piles - sheet piles wall

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Dr Youssef Hammida

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Pilaster masonry wall

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 Steel sheeting provides resistance during installation stresses. The sheets
must be driven into the ground and they have high resistance to the force
of being driven down.
 It is extremely light weight and makes it easier to lift and handle.
 Steel sheeting is reusable and recyclable.
 There is a long life for it both above and under water. It only requires light
protection to keep it maintained.
 The pile length is easily adaptable and can be welded or bolted to make it
work.
 They have stronger joints that can withstand the force of being driven into
place.

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Steel Sheet Piling Construction Steps
 First, lay out the sheets in sections to make sure that the piles will
interlock correctly.
 Drive each sheet to the depth that has been mapped out.
 Then drive the second sheet that has the interlocks between the first
sheet and the second locked sheet.
 Repeat until the wall is completed.
 If the wall requires complex shapes use connector elements to ensure
that the integrity of the wall is maintained.
 Vibratory hammers are used for the installation of steel sheet piles.
An impact hammer is used if the soil is too dense for the vibratory
hammer.
 At sites where vibrations are not recommended the sheets are pushed
into place using hydraulics.

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Sheet Pile Walls...
Sheet pile walls are another method for construction of basements and
temporary excavations, however they are increasingly being used as
permanent structures with the correctly specified surface coating.
‫ا‬‫لخوازيق‬,‫واألوتاد‬‫الساندة‬‫الحفر‬ ‫جوانب‬ ‫سند‬ ‫وظيفتها‬ ‫ألن‬ ‫الموقع‬ ‫حفر‬ ‫قبل‬ ‫تنفيذها‬ ‫بيتم‬
‫مرور‬ ‫قبل‬ ‫الحفر‬ ‫واليتم‬82‫ساند‬ ‫خازوق‬ ‫آخر‬ ‫تنفيذ‬ ‫على‬ ‫يوم‬
‫التأسيس‬ ‫تربة‬ ‫لمنسوب‬ ‫واليصل‬ ‫الحفر‬ ‫بقيمة‬ ‫مرتبط‬ ‫طوله‬ ‫الساند‬ ‫والخازوق‬
.

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For free earth support method
, the soils at the lower part of piling is incapable of inducing effective restraint so
that it would not result in negative bending moments. In essence, the passive
pressures in front of the sheet piles are insufficient to prevent lateral deflection
and rotations at the lower end of piling. No passive resistance is developed on
the backside of the piling below the line of excavation.
For fixed earth support method
, the piling is driven deep enough so that the soil under the line of excavation
provides the required restraint against deformations and rotations. In short, the
lower end of piling is essentially fixed.

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Anchored sheet pile wall
 Anchored sheet pile wall in cohesionless soil
 Anchored sheet pile wall in cohesive soil
Design using free earth support method
1. Sheet pile is rigid, and lateral deflection is small.
2. The lateral pressure distributes according to Rankine’s or Coulomb’s theories
3. The tie back is strong, and sheet pile rotate about the tie rod anchor point at
failure
4. Bottom of sheet pile is free to move.

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The embedded depth can be determined by summarizing horizontal earth pressures and
moments about the anchor.
 Fx = 0 [1]
Mo = 0 [2]
the lateral earth pressure is a function of embedded depth. Both equations are highly
nonlinear. A trial and error method has to be used to determine the root.
For structural design, the sheet pile needs to be able to withstand maximum moment
and shear from lateral pressure. A structural analysis needs to be done to determine
maximum moment and shear.

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Anchored sheet pile wall in cohesionless soil
Design length of sheet pile
Calculating active earth pressure
The method for calculating active earth pressure is the same as that in cantilever sheet
pile wall. The lateral forces Ha1 is calculated as
Ha1= Ka h2
/2+q Ka h
The depth a can be calculated as
a = pa /  (Kp-Ka)
The lateral forces Ha2 can be calculated as
Ha2=pa*a/2
Calculating passive earth pressure
The slope from point C to E in the figure above is  (Kp-Ka). The passive earth pressure at a
depth Y below a is calculated as
Pp =  (Kp-Ka) Y

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The passive lateral force
HCEF =  (Kp-Ka) Y2
/2
Derive equation for Y from Mo = 0
Mo = Ha1*y1 + Ha2* y2 – HCEF* y3 = 0
Where
y1 = (2h/3-b)
y2 = (h+a/3-b)
y3 = (h+a+2Y/3)
The equation needs to be determined by a trial and error process.
Determine anchor force T from  Fx = 0
 Fx = Ha1+ Ha2– HCEF-T = 0
Then,
T = Ha1+ Ha2– HCEF
Design size of sheet pile
The structural is the same as cantilever sheet piles in cohesionless soil.
Maximum moment locates at a distance y below T where shear stress equals to zero.
T- Ka (y+b)2
/2=0
Solve for y, we have, y = -b+2*T/( Ka)
The maximum moment is
Mmax = T y -  Ka (y+b)3
/6
The required section modulus is S = Mmax / Fb
The sheet pile section is selected based on section modulus

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Design of tie rod and soldier beam
The sheet pile design above is based on a unit width, foot or meter. The tie back force T
calculated from sheet pile design is force per linearly width of sheet pile. The top of
sheet pile often supported with soldier beams and tie rods at certain spacing.
Assume the spacing of tie rod is s, the tension in the rod is T times s. The required area of
tie rod is
A = T s / Ft
Where Ft is allowable tensile stress of steel and is equal to 0.6Fy in AISC ASD design.
The soil beam is designed as a continuous beam that subjected to tie back force T. The
maximum moment in the soldier beam is calculated from structural analysis. The
required section modulus is equal to S = Mmax / Fb.
Design procedure
1.Calculate lateral earth pressure at bottom of excavation, pa and Ha1.
pa =  Ka H, Ha1=pa*h/2
2.Calculate the length a, and Ha2.
a = pa /  (Kp-Ka), Ha2=pa*a/2
3.Assume a trial depth Y, calculate HCEF.
HCEF =  (Kp-Ka) Y2
/3
4.Let R = Ha1*y1 + Ha2* y2 – HCEF* y3
y1 = (2h/3-b)

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y2 = (h+a/3-b)
y3 = (h+a+2Y/3)
Substitute Y into R, if R = 0, the embedded depth, D = Y + a.
If not, assume a new Y, repeat step 3 to 4.
5.Calculate the length of sheet pile, L = h+F.S.*D, FS is from 1.2 to 1.4.
6.Calculate anchored force T = Ha1+ Ha2– HCEF
7.Calculate y = -b+2*T/( Ka)
8.Calculate Mmax = T y -  Ka (y+b)3
/6
9.Calculate required section modulus S= Mmax/Fb.
10. Select sheet pile section.
11. Design tie rod
12. Design soldier beam.

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Example 3. Design anchored sheet pile in cohesionless soil.
Depth of excavation, h = 10 ft
Unit weight of soil,  = 115 lb/ft3
Internal friction angle,  = 30 degree
Allowable design stress of sheet pile = 32 ksi
Yield strength of soldier beam, Fy = 36 ksi
Location of tie rod at 2 ft below ground surface, spacing, s = 12 ft
Requirement: Design length of an anchored sheet pile, select sheet pile section, and
design tie rod
Solution:
Design length of sheet pile:
Calculate lateral earth pressure coefficients:
Ka = tan (45-/2) = 0.333
Kp = tan (45-/2) = 3
The lateral earth pressure at bottom of excavation is
pa = Ka  h = 0.333*115*10 = 383.33 psf
The active lateral force above excavation
Ha1 = pa*h/2 = 383.33*10/2 = 1917 lb/ft
The depth a = pa /  (Kp-Ka) = 383.3 / [115*(3-0.333)] =1.25 ft
The corresponding lateral force
Ha2 = pa*a/2 = 383.33*1.25/2 = 238.6 lb/ft
Assume Y = 2.85 ft
HCEF =  (Kp-Ka) Y2
/3 = 115*(3-0.333)*2.852
/3 = 830.3 lb/ft
y1 = (2h/3-b) = (2*10/3-2)=4.67 ft
y2 = (h+a/3-b) = (10+1.25/3-2)=8.42 ft

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y3 = (h+a+2Y/3) = (10+1.25+2*2.85/3) = 13.15 ft
R = Ha1*y1 + Ha2* y2 – HCEF* y3 = 1917*4.67+238.6*8.42-830.3*13.15 = 42.5 lb
R closes to zero, D = 2.85+1.25 = 4.1 ft
Length of sheet pile, L = 10 + 1.2* 4.1 = 14.9 ft Use 15 ft
Calculate anchor force,
T = Ha1+ Ha2– HCEF = 1917+238.6-830.3 = 1326 lb/ft
Calculate location of maximum moment,
y = -b+2*T/( Ka) = -2 ft + 2*1326/(115*0.333) = 6.32 ft
Mmax = T y -  Ka (y+b)3
/6 = 1326*6.32 – 115*0.333*(6.32+2)3
/6 = 4.7 kip-ft/ft
The required section modulus S= Mmax/Fb = 4.7*12/32 = 1.8 in3
/ft
Use PS28, S = 1.9 in3
/ft
Design tie rod, the required cross section area,
A = T s / (0.6*Fy) = 1.326*12/(0.6*36) = 0.442 in3
.
Use ¾” diameter tie rod, A = 0.442 in3
.
Design soldier beam:
The maximum moment of a continuous beams with 3 or more span is
M = 0.1*T s2
= 0.1*1326*122
=19.1 kip-ft
Required section modulus, S = M / (0.6*Fy) = 19.1*12/(0.6*36) = 6.4 in3
.
Use W6x15, S = 9.72 in3
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Anchored sheet pile wall in cohesive soil.
Calculating active earth pressure
Calculation of active earth pressure above excavation is the same as that of cantilever
sheet pile in cohesive soil. The free-standing height of soil is d = 2C/
The lateral earth pressure at bottom of excavation, pa =  h – 2C, where  is unit weight
of soil. The resultant force Ha=pa*h/2
Calculating passive earth pressure
For cohesive soil, friction angle,  = 0, Ka = Kp = 1. The earth pressure below excavation,
p1= p-a= 2C-(h-2C) = 4C-h
Assume the embedded depth is D, the resultant force below bottom of excavation is
HBCDF = p1*D
Derive equation for D from Mo = 0
Mo = Ha1*y1 – HBCDF* y3 = 0
Where
y1 = 2(h-d)/3-(b-d)
y3 = h-b+D/2
The equation can be determined with a trial and error process.

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Determine anchor force T from  Fx = 0
 Fx = Ha1– HBCDF-T = 0
T = Ha1+ Ha2– HCEF
Design size of sheet pile
Maximum moment locates at a distance y below T where shear stress equals to zero.
T- Ka (y+b-d)2
/2=0
Solve for y, we have, y = -b+d+2*T/( Ka)
The maximum moment is
Mmax = T y -  Ka (y+b-d)3
/6
The required section modulus is S = Mmax / Fb
The sheet pile section is selected based on section modulus
Design of tie rod and soldier beam
Design of tie rod and soldier beam is the same as that of anchored sheet pile in
cohesionless soil.
1.Calculate free standing height, d = 2C/
2.Calculate pa=(h-d)
3.Calculate Ha=pa*h/2
4.Calculate p1=4C-h,
5.Assume a value of D, and calculate HBCDF = p1*D
6.Calculate R= Ha*y1 – HBCDF* y3.
Where
y1 = 2(h-d)/3-(b-d)
y3 = h-b+D/2
If R is not close to zero, assume a new D, repeat steps 5 and 6
7.The design length of sheet pile is L=h+D*FS, FS=1.2 to 1.4.
8.Calculate anchored force T = Ha – HBCDF
9.Calculate y = -b+d+2*T/
10. Calculate Mmax = T y -  (y+b-d)3
/6
11. Calculate required section modulus S= Mmax/Fb. Select sheet pile section.

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12. Design tie rod
13. Design soldier beam.
Example 4: Design anchored sheet pile in cohesive soil.
Depth of excavation, h = 15 ft
Unit weight of soil,  = 115 lb/ft3
Cohesion of soil, C = 500 psf
Internal friction angle,  = 0 degree
Allowable design strength of sheet pile = 32 ksi
Yield strength of soldier beam, Fy = 36 ksi
Location of tie rod at 2 ft below ground surface, spacing =12 ft.
Requirement: Design length of sheet pile and select sheet pile section
Solution:
Design length of sheet pile:
The free standing height, d = 2C/ = 2*500/115 = 8.7 ft
The lateral pressure at bottom of sheet pile, pa = (h-d)=115*(10-8.7)=150 psf
Total active force, Ha=pa*h/2 = 150*10/2 = 750 lb/ft
p1=4C-h = 4*550-115*15 = 275 psf
Assume D = 11.5 ft,
HBCDF = p1*D = 3163 lb/ft
y1 = 2(h-d)/3-(b-d) =2 (15-8.7)/3-(2-8.7) = 10.9 ft
y3 = h-b+D/2 = 15-2+11.5/2 = 18.75 ft
R= Ha*y1 – HBCDF* y3 = 5438*10.9-3163*18.75 = -36 lb Close to zero
The length of sheet pile, L = 15 + 1.2*11.5 = 28.8 ft Use 29 ft
Anchored force per foot of wall, T = Ha – HBCDF = 5438 – 3163 = 2275 lb/ft

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Calculate location of maximum moment,
y = -b+d+2*T/ = -2+8.7+2*2275/115 = 13 ft
Maximum moment,
Mmax = T y -  (y+b-d)3
/6 = 2275*13 – 115*(13+2-8.7)3
/6 = 24770 lb-ft/ft
Required section modulus of sheet pile, S= Mmax/Fb = 22.47*12/32 = 8.4 in3
/ft
Use PDA 27 section modulus 10.7 in3
/ft
Design tie rod
Cross section of tie rod required, A = T*s/(0.6*Fy) = 2.275*12/(0.6*36) = 0.91 in2
.
Diameter of tie rod, d = 4*A/ = 1.08 in
Use 1-1/8” diameter tie rod.
Design soldier beam
Maximum moment in solider beam, Mmax = 0.1*T*s2
= 0.1*2275*122
= 32760 lb-ft
Required section modulus, S= Mmax/Fb= 32.76*12/(0.6*36) = 13.1 in3
.
Use W 8x18, section modulus S = 15.2 in3
.

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types of deep support systems
are commonly used in metropolitan cities.
(i) Diaphragm walls
(ii) Pile walls (Contiguous, Tangent or Secant)
(iii) Soldier pile w
ith wooden lagging walls
(iv) Sheet pile walls
(v) Composite supporting systems – that is, any of the retaining
systems
Retaining systems like
diaphragm wall, contiguous pile walls;
and soldier piles with wooden lagging
described in this article has been successfully used. Case studies of their use indicate
that adequate quality control measures and instrumentation monitoring of
these systems go a long way in ensuring their safeand economic deployment at
sit

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Contiguous Pile Walls General – Piled Retaining Systems
Abstract
Providing space for parking, public amenities,etc in multi-storey buildings at
town centres has created a need to go deep excavationsinto ground. Deep excavations
are supported by systems like conventional retaining walls, sheet pile walls,
braced walls, diaphragm walls and pile walls. This article describes various
excavation supporting systems that are in vogue essentially contiguous pile wall
and its advantages. A detailed design methodology of an excavation supporting
system is furnished in this study.
There are different types of pile walls
(Fig.4).Diameter and spacing of the piles is
decided based on soil type, ground water level and magnitude of design pressures.
Large spacing is avoided as it can result in caving of soil through gaps. In
Contiguous bored pile construction, center to center spacing of piles is kept slightly greater
thanthe pile diameter.
Secant bored pilesre formed by keeping this spacing of piles less
than the diameter.Tangen

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Fig. 4: Schematic Arrangement of Contiguous Piled Retaining System.
Contiguous piles serving as retaining walls
are popular since traditional piling equipments can be resorted for their construction. They
are considered more economical than diaphragm wall in small to medium scale excavations
due to reduction in cost of site operations. Common pile diameters adopted are 0.6, 0.8 and
1 .0m. These piles are connected with a Capping beams at the top, which assists equitable
pressure distributions in piles. These retaining piles are suitable in areas where water table is
deep or where soil permeability is low. However, some acceptable amount of water can be
collected at the base and pumped out.
ARRANGEMENT OF CONTIGUOUS PILe

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Secant Pile Walls are formedby constructing intersecting piles. Secant bored
pile walls are formed by keeping spacing ofpiles lessthan diameter.
Secant pile walls are used tobuild cut off walls for the control of
groundwater inflow and to minimizemovement in weak and wet soils.
Secant Wall constructed in the form of hard/soft or hard/firm and Secant
Wall Hard/hard wall. Secant Wall-hard- softs or hard/firm is similar
tothe contiguous bored pile wall

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Soldier Piles and Wooden Lagging supported system
The supporting system comprised soldier piles
spaced at 1.8m c/c and with a closer spacing of 1.6m c/c near the launching shaft
(Fig.8). Wooden laggings of thickness 100mm to 120mm were supported
between the soldier piles.Three levels of Struts were provided at depths 3.285,
7.285, and 10.831m below the established ground level (EGL-209.80m).
Additional level of Waler beam with pre-stressed rock anchors were provided
2m above the excavation level. Rock anchors with capacity of 86.4T,spaced at
3.6m c/c, were embedded 6m into the quartzitic bedrock to meet the bond
strength consideration

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Soldier Piles & Laggings Wooden Supporting System

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Dr Youssef Hammida