Rubble Mound Breakwater Design Calculations

1.

2.

3. Design H = minimum of Hmax or Hb (Hmax may be H1/3 or H1/10)

4. Run-up

a. for m < 1.5

b. for m > 1.5

c.

5. Overtopping

a.

b.

c.

6. R = maximum of or

7. Design crest elevation = DHW + R

8. Armor weight:

9. Armor thickness:

10. Crest Width:

11. Base Width:

12. Armor area (per unit length):

13. Number of armor units:

14. Underlayer thickness:

15. Total volume (per unit length)

h

a

bth

a.

b.

16. Scour Depth:

17. Toe apron width: maximum of Bt = 2H or Bt = 0.4h

18. Toe stone weight

a.

b. maximum of or Ns = 1.8

c.

d. assuming quarry stone sorting is 0.75 W/W50 1.25 W50 = Wmin/0.75

19. Toe base: bt = 2Btcott

20. Toe volume (total, per unit length, 2 identical toe structures):

21. Toe-to-toe width of breakwater:

22. Bedding layer stone weight:

a.

b.

c. , where ds = scour depth (this is the minimum bedding layer thickness)

d.

e. width: Bbed = Btt + 2(5 m)

f.

23. Breakwater weight (load on soil) - In order to generalize the calculation for use with concrete armor units, the weight of the armor layer is calculated separately from the rest of the breakwater. Also, the load is separated into above and below the low water mark (h) to correct for buoyancy.

h

a

bth

a. Volume of Underlayer & core above DLW:

where

b. Volume of Armor Layer above DLW:

where

c. Volume of Underlayer & core below DLW:

where

d. Volume of Armor Layer below DLW:

where

e. Weight of layers:

i. above DLW

ii. below DLW

24. Soil Load ()

a. Base width redistributed through the bedding layer:

b. Load at top of bedding layer:

c. Load at bottom of bedding layer:

25. Allowable Bearing Capacity

a. Normally consolidated clay:

b. Layered Sand, Dense over Loose (Das, 1994)

or

c. Layered Sand, Loose over Dense (from Das, 1994)

, Hf = depth of failure surface ~ 2B

d. Layered Clay - Stronger over Weaker ( = 0), (Das, 1994)

or

e. Granular Stratum over Soft Clay (Herbich, 1991)

or

f. Allowable bearing capacity:

26. Depth of calculation in lower layer: H = 4Btt - (upper layer depth)

27. Compression Index: Cc = slope of the e-log p curve:

Empirically: Rendon-Herrero (1983)

Terzaghi & Peck (1967)

Nagaraj and Murty (1985)

28. Swell index:

29. Initial load and void ratio

a. [H from eq. (26)]

b.

30. Settlement

a. Normally consolidated soil (pc = po + p):

b. Overconsolidated soil (pc po + p):