1. Session 15 – 16 SHEET PILE STRUCTURES
Course : S0484/Foundation Engineering
Year : 2007
Version : 1/0
Session 15 – 16 SHEET PILE STRUCTURES

2. SHEET PILE STRUCTURES
Topic:
Anchored Sheet Pile
Braced Cut

3. CALCULATION STEPS ANCHORED SHEET PILE – FREE – SAND

4. CALCULATION STEPS ANCHORED SHEET PILE – FREE – SAND
1. Determine the value of Ka and Kp
2. Calculate p1and p2 with L1 and L2 are known
3. Calculate L3
4. Calculate P as a resultant of area ACDE
5. Determine the center of pressure for the area ACDE ( z )

5. CALCULATION STEPS ANCHORED SHEET PILE – FREE – SAND
6. Calculate L4
Determination of penetration depth of sheet pile (D)
Dtheoretical = L3 + L4
Dactual = (1.3 – 1.4) Dtheoretical
Determination of anchor force
F = P – ½ [’(Kp – Ka)]L42

6. CALCULATION STEPS ANCHORED SHEET PILE – FREE – CLAY

7. CALCULATION STEPS ANCHORED SHEET PILE – FREE – CLAY
1. Determine the value of Ka and Kp
In case of saturated soft clay with internal friction angle () = 0, we got
Ka = Kp = 1
2. Calculate p1and p2 with L1 and L2 are known
3. Calculate the resultant of the area ACDE (P1) and z1 (the center of pressure for the area ACDE)

8. CALCULATION STEPS ANCHORED SHEET PILE – FREE – CLAY
4. Calculate p6
Determination of penetration depth of sheet pile (D)
p6.D2 + 2.p6.D.(L1+L2-l1) – 2.P1.(L1+L2-l1-z1) = 0
Determination of anchor force
F = P1 – p6 . D

9. CALCULATION STEPS ANCHORED SHEET PILE – FIXED – SANDJ

10. CALCULATION STEPS ANCHORED SHEET PILE – FIXED – SAND
1. Determine the value of Ka and Kp
2. Calculate p1and p2 with L1 and L2 are known
3. Calculate L3

11. CALCULATION STEPS ANCHORED SHEET PILE – FIXED – SAND
4. determine L5 from the following curve (L1 and L2 are known)

12. CALCULATION STEPS ANCHORED SHEET PILE – FIXED – SAND
5. Calculate the span of the equivalent beam as l2 + L2 + L5 = L’
6. Calculate the total load of the span, W. This is the area of the pressure diagram between O’ and I
7. Calculate the maximum moment, Mmax, as WL’/8

13. CALCULATION STEPS ANCHORED SHEET PILE – FIXED – SAND
8. Calculate P’ by taking the moment about O’, or
9. Calculate D as
10. Calculate the anchor force per unit length, F, by taking the moment about I, or
(moment of area ACDJI about O’)
(moment of area ACDJI about I)

14. BRACED CUT
Type of Braced cut

15. BRACED CUT
Type of Braced cut

16. PRESSURE ENVELOPE Cuts in Sand pa = 0.65HKa Where:  = unit weight
H = height of the cut
Ka = Rankine active pressure coefficient
= tan2(45-/2)

17. PRESSURE ENVELOPE
Cuts in Stiff Clay
pa = 0.2H to 0.4H
Which is applicable to the condition

18. PRESSURE ENVELOPE Cuts in Stiff Clay The pressure pa is the larger of
Which is applicable to the condition
Where:
 = unit weight of clay
c = undrained cohesion (=0)

19. PRESSURE ENVELOPE Limitations:
The pressure envelopes are sometimes referred to as apparent pressure envelopes. The actual pressure distribution is a function of the construction sequence and the relative flexibility of the wall.
They apply to excavations having depths greater than about 20 ft (6m)
They are based on the assumption that the water table is below the bottom of the cut
Sand is assumed to be drained with zero pore water pressure
Clay is assumed to be undrained and pore water pressure is not considered

20. PRESSURE ENVELOPE Cuts in Layered Soil Where:
H = total height of the cut
s = unit weight of sand
Hs = thickness of sand layer
Ks = a lateral earth pressure coefficient for the sand layer (1)
s = friction angle of sand
qu = unconfined compression strength of clay
n’ = a coefficient of progressive failure (ranging from 0.5 to 1.0; average value 0.75)
c = saturated unit weight of clay layer

21. PRESSURE ENVELOPE Cuts in Layered Soil Where:
c1, c2,…,cn = undrained cohesion in layers 1,2,..,n
H1, H2,…,Hn = thickness of layers 1, 2, …, n
1, 2, … n = unit weight of layers 1, 2, … , n

22. DESIGN OF VARIOUS COMPONENTS OF A BRACED CUT
Struts
Should have a minimum vertical spacing of about 9 ft (2.75 m) or more.
Actually horizontal columns subject to bending
The load carrying capacity of columns depends on the slenderness ratio.
The slenderness ratio can be reduced by providing vertical and horizontal supports at intermediate points
For wide cuts, splicing the struts may be necessary.
For braced cuts in clayey soils, the depth of the first strut below the ground surface should be less than the depth of tensile crack, zc

23. DESIGN OF VARIOUS COMPONENTS OF A BRACED CUT
Struts
General Procedures:
Draw the pressure envelope for the braced cut

24. DESIGN OF VARIOUS COMPONENTS OF A BRACED CUT
Struts
General Procedures:
2. Determine the reactions for the two simple cantilever beams (top and bottom) and all the simple beams between. In the following figure, these reactions are A, B1, B2, C1, C2 and D

25. DESIGN OF VARIOUS COMPONENTS OF A BRACED CUT
Struts
General Procedures:
The strut loads may be calculated as follows:
PA = (A)(s)
PB = (B1+B2)(s)
PC = (C1+C2)(s)
PD = (D)(s)
where:
PA, PB, PC, PD = loads to be taken by the individual struts at level A, B, C and D, respectively
A, B1, B2, C1, C2, D = reactions calculated in step 2
s = horizontal spacing of the struts
4. Knowing the strut loads at each level and intermediate bracing conditions allows selection of the proper sections from the steel construction manual.

26. DESIGN OF VARIOUS COMPONENTS OF A BRACED CUT
Sheet Piles
General Procedures:
Determine the maximum bending moment
Determine the maximum value of the maximum bending moments (Mmax) obtained in step 1.
Obtain the required section modulus of the sheet piles
Choose the sheet pile having a section modulus greater than or equal to the required section modulus

27. DESIGN OF VARIOUS COMPONENTS OF A BRACED CUT
Wales
Where A, B1, B2, C1, C2, and D are the reactions under the struts per unit length of the wall

28. EXAMPLE Refer to he braced cut shown in the following figure:
Draw the earth pressure envelope and determine the strut loads. (Note: the struts are spaced horizontally at 12 ft center to center)
Determine the sheet pile section
Determine the required section modulus of the wales at level A (all = 24 kip/in2)

29. EXAMPLE

30. EXAMPLE

31. EXAMPLE

32. EXAMPLE