The pile tip is mitered to keep it closed into the adjacent pile while driving or jetting. 

 The upper part of the pile is held against the adjacent pile with a rope sling, and a temporary 

 timber backing frame is used to keep the wall on line as the work progresses. In sandy soils, 

 jetting alone is used to seat the piles, but in loam or clayey soils, they must be driven into 

 place to avoid loose seating. The tieback system differs from that of metal or timber sheet 

 piling in that the tie rods are usually embedded in a cap beam poured around the top edge 

 of the completed wall (Fig. 53). 



Except for width of the pile, the proper dimensions for the concrete sheet piles must be 

 determined by engineering analysis in the same manner as for timber or metal sheet piles. 

 The pile width (incremental length of progression along the wall per pile) may be varied to 

 suit the placement conditions of the site. In sandy soils where jetting to grade is permissible, 

 the width of the pile is limited (in combination with the thickness and length) only by the 

 capacity of the handling equipment and certain convenience considerations. These factors 

 usually limit the width to about 4 or 5 feet. Where the piles must be driven in tight soils, the 

 width must be decreased to prevent damage in driving. In tight soils, a good practice is to 

 make the width about twice the pile thickness, and the reinforcing cage must be 

 strengthened with more looping near the top to prevent shattering of the concrete under 

 hammer impact. 



Concrete perimeter bulkheads are the most durable if properly designed and constructed. 

 In a marine environment, it is important that the ingredients of the concrete, mixing and 

 placing in the structure be carefully controlled. Chaney (1961) discusses in detail the types 

 of cements that are suitable for various conditions, the selection of aggregates, placement, 

 and resultant structural properties of the cured concrete in the structure. For ready 

 reference, the ACI Standard 211-1-74, Recommended Practice for Selecting Proportions for 

 Normal and Heavyweight Concrete, published by the American Concrete Institute is 

 reproduced in Appendix C. 



Guidance for selecting types of concrete mixes for special environments is published by 

 the California Division of Highways, Bridge Department, in a Bridge Planning and Design 

 Manual, 1969. The part on "Corrosion Protection for Concrete" is reproduced in 

 Appendix D. 



Marinas are often built in areas where the substrata have low bearing capacities, and a 

 heavy wall may settie unless adequately supported on bearing piles (Fig. 54). The tendency 

 of silty materials and soft clays to flow out from under walls or to push the entire wall 

 toward the basin under saturated conditions requires careful analysis. Proper drainage 

 through French drains or weep holes under the base of the wall and provision of batter piles 

 will usually counteract these destructive tendencies. A soils analysis will reveal the required 

 extent of such drainage requirements. All concrete construction must be designed in 



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