h. Sheet-Pile Structures . 



(.1) Design . Bulkheads in waterfront facilities are subjected to 

 lateral pressure resulting from earth movement and the unbalanced hydrostatic 

 and seepage forces acting on opposite sides of the wall. A higher water 

 level may exist in the backfill behind the wall than in front of it as a 

 result of a receding tide, receding high water, or a heavy rainstorm. Other 

 lateral loads that may be encountered are ice thrust, wave forces, ship 

 impact, mooring pull, and earthquake forces. Because of its material 

 strength sheet pile is often used in marine construction for bulkheads. The 

 designer, after evaluating the lateral pressure and forces, must determine 

 the required depth of piling penetration, the maximum bending moments in the 

 piling, and the maximum bending stresses in the wall. An appropriate sheet- 

 pile section must be selected, taking into account yield strength and moment 

 of inertia of the selected section. Some typical steel sheet-pile profiles 

 are shown in Figure 50. A choice may be made between a cantilevered or 

 anchored wall . 



Anchored sheet-pile walls can be designed for greater height than is 

 possible with the cantilever-type design with a similar sheet-pile section. 

 For heights to about 11 meters (35 feet} (depending on soil conditions), 

 sufficient support can be obtained from anchor tie rods near the top of the 

 wall and the lateral support of the embedded part of the wall. For greater 

 heights, higher yield strength steel or multiple tie rods at lower levels 

 are required. Anchorage systems in use include deadman anchors, H-pile 

 anchors, and sheet-pile anchors. Sketches of the systems are shown in 

 Figure 51. Regardless which anchorage system is used, the anchor must be 

 located outside the potential active fracture zone behind the sheet-pile 

 wall. Passive resistance of the anchor is not possible if the ground is 

 unstable. 



A complete sheet-pile wall system may consist of the wall, wale, tie 

 rods, and the anchor. The wale is a flexible member attached to the wall 

 which distributes the horizontal reactive force from the anchor tie rods to 

 the wall section. Locating the wale on the outside of the wall where the 

 piling will bear against the wale in compression is preferred for engineering 

 purposes. However, wales are sometimes bolted onto the inside face to 

 provide a clear outside face. 



Wales are often constructed of steel structural channels conforming to 

 ASTM Standard A36 mounted with their webs back to back, and separated by 

 enough space to clear the end of tie rod between them. When the wales are 

 located on the inside face, each sheet-pile section is bolted to the wale. 

 Standard wale designs for wales located on both outside and inside faces are 

 shown in Figure 52. 



Tie rods are usually round steel bars, comforming to ASTM Standard A36, 

 that have been upset and threaded at each end so as to maintain cross- 

 sectional area in the threaded part. Usually a turnbuckle is used between 

 two tie-rod sections to allow removal of slack. Sagging of the tie rods may 

 occur because of soil settlement around them which drags them downward, 

 causing increased tension in the rods. Two methods of avoiding this con- 

 dition are: (!) use light vertical piles at 6- to 9-meter (20 to 30 foot) 

 intervals to support the rods, or (2) encasing the rods in large conduits. 



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