Methods of Driving of Sheet Pile
When Piles are being driven they have a tendency to lean in the direction of driving; this tendency must therefore be restricted by some form of guide control. There are various ways in which piles may be guided during driving but the two principal methods in popular use are:
Driving of Pile in Panels
Driving in panels is a very satisfactory method of positioning sheet piles and ensuring that the piles do not creep out of vertical. Work is commenced by pitching and driving a pair of piles to part-
penetration, care being taken to maintain correct position and verticality. A panel of piles, from six to twelve pairs, are then pitched and interlocked in position. The last pair of piles in the panel are driven and then guide waling are bolted between the first and last pair of piles to support the panel during driving. The remaining pairs of piles are then driven to their final position. The last pair of piles are left in a partly driven state to form the support of the next panel of piles.
When driving long piles it is preferable to use a light hammer for the first stage, following up with a heavy hammer for final driving. This is best achieved by using two cranes, one handling the smaller hammer, the other following behind with the heavy hammer.
Use of trestles and waling
Trestles and waling are the common alternative method of supporting sheet piles during driving. The method involves the use of very heavy trestles which have to be moved and positioned by carnage, which in turn support long heavy waling. Trestles are normally constructed in steel. Where steel piles are to be driven through water, the guide waling may be supported on temporary timber piles which form a heavy duty or light duty guide. With this second
method of support the piles are often driven in pairs directly after pitching and there is a greater possibility of vertical creep than in panel driving. A slope of more than 1 in 300 may be difficult to close, although special tapered piles may be used. This method of support is therefore suitable for soft or loose ground conditions where control of vertical is satisfactory. In addition to providing support for the driving of sheet piles, further support will be required in the form of spacer blocks to obtain a good line of piling and to control the width of each pair of piles.