an extra dense layer of soil at the tip is called anend-bearing pile.A pile supported partly by skinfriction and partly by a substratum of extra dense soil atthe tip is called a combination end-bearing andfriction pile.It is not always necessary to drive a friction pile torefusal; such a pile needs to be driven only to the depthwhere friction develops the required load-bearingcapacity.Straightening and Aligning PilesPiles should be straightened when any misalign-ment is noticed during pile driving. The accuracy ofalignment that should be sought for the finished jobdepends on various factors, but if a pile is more than afew inches out of its plumb line, an effort should be madeto true it up. The greater the penetration along the wrongalignment, the harder it is to get the pile back to plumb.One method of alignment is to use pull from a blockand tackle (fig. 12-70) with the impact of the hammerjarring the pile back into line. The straightening of steelbearing piles must include twisting of the individualpiles to bring the webs of the piles parallel to the centerline of the bent.Figure 12-70.-Realigning pile using block and tackle.Another method of alignment is to use a jet (fig. 12-71),either alone or jointly, with the block-and-tackle methodWhen all piles in a bent have been driven, they maybe pulled into proper spacing and alignment with blockand tackle and an aligning frame, as shown in figures12-72 and 12-73.Pulling FilesA pile that has met an obstruction, that has beendriven in the wrong place, that has split or broken inFigure 12-71.—Realigning pile by jetting.Figure 12-72.—Aligning frame used for timber pile bent.12-50
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