Pipe piles can most conveniently be extended with a splicer. This is designed with a taper for a drive fit without welding so no advance preparation is required or a slip on splice requiring welding. If water is a problem, roofing mastic swabbed around the joint probably will be adequate.
For piles where the joint is not embedded well into firm soil or where uplift is expected the splice can be supplied without a taper. It can be slipped on a pile section while horizontal and a weld made in convenient position as the pipe is rolled. This joint has substantial lateral resistance and tension value. Driving can be done on the splicer; the next section is set into it and a quick downhand weld made to complete the joint. Do not bevel pipe to be used with the splicer. It bears on a square ledge.
The circular shape of pipe makes it practical to use a tapered compression splicer without welding. These types of pipe splices do not require welding. The design incorporates a “ledge” at the center makes a “drive stopper” at the interface. Newly develop
ed foundry techniques permit casting this splicer to a water resistant connection. This no-weld splicer has been proved by thousands of connections made from a specially rolled bar with the center ledge. During the manufacturing process an accurate length is cut, rolled to a circle, flash welded, then stretched to the required size.
When attaching the no weld pipe splicer, the splice is set on a driven length and leveled by tapping with a sledge. The pile driver then picks up the next length of piling and sets it on top of now present splice. Driving continues with very little delay. These types of splices have a tapered sleeve with a stop at the center which is placed on the driven section. It is squared up with the axis of the pipe while an added section of pile is picked up. As the pile is driven the pipe ends are swaged into the tapered splicer, making a tight friction joint that resists lateral bending of the pile. For most conditions no welding is required.
Splices for pipe piles may be full-penetration butt welds. Where attachment is made after a length of pile is driven, only the lower end of the upper section should be beveled so hammer contact is on the full area of the steel. A back-up ring, with protruding knock-off pins is available to space and back up the welds.
Full penetration butt welds or fillet welds shown are commonly used for splicing pipe piles. Pipe piles can also be spliced with patented splicers similar to the one shown. This splicer is fabricated from ASTM A 36 steel and is designed with a taper for a drive fit without welding so no advance preparation is required. Unless the splicer is fillet welded to the pile, the splice will not provide full strength in bending.
In some cases a splicer has been used as a driving head on thin-wall pipe piles. For 0.188 in. (thin) wall pipe, for example, the regular tapered sleeve can be driven on with a sledge, compressing the pipe end sufficiently to hold the sleeve in place while the pile is lifted into the leads. This procedure must be used with great care, however, as a falling sleeve could be injurious. (The splicer makes an excellent driving head for thin-wall pipe – even where extension is not required). Use of a splicer as a driving head has been found in many cases to reduce crippling of the pipe under blows of the hammer.
Where full uplift resistance is needed, and for piles in free standing water, some welding at the joint may be desirable. Some splicers can be supplied without the taper. It can then be slipped on a section of pipe in the shop or on the job and welded in convenient position before it is put into the leads. Driving can be done on the splicer to bring the pile to a convenient height. As sections are added a simple downhand weld can be made in the top of the splicer with very little delay to the driver.
Protrusions on pipe, such as spiral welds or burrs should be ground smooth for about 3 in. from the end of pipe where outside flanged points or splicers are to be used as a friction connection. The pipe can be ordered with this done at the mill. Protrusions can be quickly removed on the job with a power grinder.
It has long been claimed that pipe piles driven with flat-plate closure form a conical point of compressed earth ahead of the pile which functions similarly to a cast steel point. Close observation of such piles under test indicate that in at least some cases this conical shape of earth loses its supporting value as the soil pressures around it equalize with time. This apparently has permitted settlement of piles under test and may continue.