APPENDIX B-Continued 



AWPI Technical Guidelines 



For Pressure Treated Wood 



S3 



1970 



Bulkheads: Design and Construction— Part II 



SUMMARY 



This bulletin discusses the nine (9) procedures which 

 are required in the design for anchored bulkhead con- 

 struction. The step-by-step descriptions which include 

 some basic mtormalion are presented in detail from 

 steps la through Ig Descriptions from step 2 through 

 step 9 will be discussed in later bulletins 

 Design Steps 

 Several steps are required in the design of an 

 anchored bulkhead as follows: 



1 Determine the following basic information: (See 

 Fig 4 ) 



a Water depth required (by owner). 



b Water level variation in front of sheet piling 



(From Tide Tables.) 

 c Effects of scour (elevation of stable mudline) 

 d Ground water level behind bulkhead at time 



of low-water level in front 

 e Level of finished grade behind bulkhead 

 f Types of soil available for backfill and for 



resisting movement of lower ends of sheet 



piling: unit weights of moist and submerged 



soils (See Table 2.) 

 g Amount of vertical surcharge loads (if any) 



anticipated on ground behind bulkhead 



(determined from proposed use of site) 



2 Prepare earlh-pressure diagrams tor inner and 

 outer faces of sheet piling to obtain resultant 

 pressure diagram (See Figs. 6 and 7. Part III.) 



3 Determine depth of sheet pile penetration 



4 Determine pull in tie rods 



5 Compute bending moment in sheet piling 



6. Determine required thickness of sheet piling 



7. Determine size and spacing of tie rods 



8. Determine bending moment and required size of 

 wales. 



9 Design anchorage to resist for tie-rod pull 

 Each of these steps i? described in detail and in 

 sequence m the following paragraphs 



WATER DEPTH REQUIRED (Step la) 



The depth of water against the face of a timber bulk- 

 head must be determined before the bulkhead can 

 be designed It the bulkhead is simply a "retaining 

 wall' for shore protection of a building site, the depth 

 of water may simply be whatever naturally results 

 when tlie bulkhead is constructed along the desired 

 shoreline 



Elsewhere, in a marina for example, the depth of 

 water may depend upon the types of boats that may 

 be brought adjacent to the bulkhead The property 

 owner, or the developer of the marina, may establish 

 minimum requirements for water depth Some dredg- 

 ing may be required to achieve these depths, although, 

 generally, the least costly solution is to place the bulk- 

 head farther from shore in deeper water. 



WATER LEVEL VARIATION (Step lb) 



At coastal locations, the water level variation on the 

 exposed face of the sheet piling may be obtained from 

 tide tables published by the U S Coast and Geodetic 

 Survey and by the Navy Oceanographic Office. At 

 inland locations adjacent to lakes and rivers, seasonal 

 records of high- and low-water levels may be used. 

 These latter data are available from offices of the 

 Corps of Engineers, slate or local conservation 

 agencies, city or county engineers, and building 

 officials. 



The "design value" used for the "high-water level" 

 requires some judgment This value need not be the 

 highest water level ever recorded in the vicinity, but 

 should be a reasonably high value that, statistically, is 

 expected to occur within the design life of the 

 structure 



DEPTH OF SCOUR (Step 1c) 



The construction of a bulkhead may deflect wave 

 energy in such a way thai it erodes the bottom material 

 adjacent to the sheet piling This is most likely to occur 

 in shallow depths, especially if mean low water is less 

 than two feet It is advisable to assume that the energy 

 deflection, occurring at the time of intermediate and 

 higher tide stages, will ero0e the bottom material to 

 a depth of 2 or 3 feet below mean low water. 



Accordingly, when lacking more definitive data, 

 assume a minimum low-water depth of 2 to 3 feet 

 This will result in a requirement for slightly longer sheet 

 piling, but will prevent the failure that can occur if the 

 bottom material is eroded to the extent that the sheet 

 piling may be shoved out of place. 



WATER LEVEL IN THE BACKFILL (Step Id) 



The ground-water level in the backfill will rise and fall 

 as the tide rises and IhIIs This is caused mostly by 

 natural percolation ot -.Met through the soil, behind 

 the lower portions ol : le bulkhead wall, rather than 



©1970 AMERICAN WOOD PRESERVERS INSTITUTE 2600 Vlrfllnla Ave,. N, W, Washington, D. C, 20037 



312 



