Tie rods are subject to corrosion and must, therefore, be adequately coated 

 and wrapped. 



(21 Construction . Steam hammers are commonly employed for pile 

 driving in the United States. During driving, the steam hammer, consisting 

 of a housing and the moving part called the ram rests on top of the pile. A 

 single acting steam hammer is a freely falling ram with steam pressure 

 acting on a piston to raise the ram prior to fall. In a double acting 

 hammer, steam is not only used to lift the ram but also to help drive the 

 ram downward. Double acting hammers are able to deliver blows faster than 

 single acting hammers of the same energy output because double acting 

 hammers use a shorter stroke and higher ram acceleration. Roth drop hammers 

 and diesel hammers are also available. A drop hammer consists of a heavy 

 weight or ram that is allowed to fall by gravity on top of the pile. Fall 

 height must be controlled to avoid damage to pile heads by excessive impact 

 from rams moving with high velocity. 



Excessive impact or improper cushioning during pile driving may result 

 in mashed pile heads. Vertical misalinement of the pile as a result of 

 obstructions encountered below the ground surface or of poor pile-driving 

 conditions may cause failure of pile interlocks. If excessive misalinement 

 occurs, sheet piles can become over stressed resulting in bulkhead failure. 



The method used for the construction of steel breakwaters depends on the 

 soil conditions and the height of the waves. If the waves are below 10 

 feet, and the bottom is soft to a great depth, steel sheet pile topped with 

 concrete and supported with batter piles may be used. 



Bulkheads for small -boat harbors have been constructed using sheet 

 piling of aluminum alloy 5052-H141. Coping was of 6063-T6, tie rods and 

 stiff ener bar beams of 6061-T6. Deadman anchors were constructed of 5052- 

 H141 alloy. Aluminum sheet pile is available in 3.6-meter (12 foot) lengths 

 which limit application to shallow facilities. 



c. Gabions. Gabions, compartmented rectangular containers made of 

 galvanized steel hexagonal wire mesh and filled with small stones, have been 

 used to reinforce the shoulder of seawalls constructed of rock. They have 

 also been used to construct jetties as well as revetments and seawalls to 

 control shoreline erosion. Gabion mattresses can also be used as foundations 

 or filter layers under rubble-mound structures and caisson structures. For 

 seawater use, gabions of galvanized wire should be coated with plastic to 

 reduce corrosion. The Alaska District limits use of gabions in the wave 

 zone where ice occurs due to bursting of the gabions by the ice. Also, if 

 the gabions are not rigidly filled, the rockfilling can move and abrade the 

 wire. 



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