Discussion. Silent and Vibration-Free Sheet Pile Driving.

Abstract

Consulting Engineers I shall make my comments from the point of view of a customer who has used the Pilemaster.87. About 18 months ago my firm was responsible to the Ministry of Transport for the reinstatement of two short lengths of river wall at Wisbech. The design finally adopted was steel sheet piling and the Pilemaster was used to install the piles.88. Frodingham No. 4 N piles, 55 ft long were required which had to penetrate between 30 ft and 40 ft into sandy silt. The site was virtually in the town centre and there was a great mass of very old property immediately adjoining the works, some of it being listed as of historic interest. Consequently, when our thoughts turned towards using sheet piling, having regard to noise and vibration the possibility of using the Pilemaster was attractive.89. However, the site had three potentially serious obstacles. First, the adjoining lengths of the river showed ample evidence of earlier structures and we anticipated a lot of timber and stone debris in the upper layers. Secondly, whilst the River Board had been very co-operative and most helpful in allowing us to come forward into the river with our new work, they had no choice but to insist that we put our piles to the same batter as the existing piles. They could not let us have vertical piles. Thirdly, over the second length of wall, the raking piles had to follow a curved line in plan, so we were setting quite a task for sheet piling. 90.Because of these difficulties we thought that a full-scale test was desirable before committing ourselves to the Pilemaster, and in February 1967 the Ministry of Transport arranged for the purchase of a panel of eight piles to be pushed down byPilemaster. As this was completely successful, the project went forward to tender with the Pilemaster specified. 91. The job was completed without undue incident. As the Authors mentioned, we did have to resort to percussive driving on several occasions and it was very noticeable that every time the hammer came on, the Contractors' telephone began to ring with calls from a wide area around Wisbech, but these complaints stopped as soon as the hammering stopped. 92.In the first length of wall we found that the first pile in each new panel refused after about 15 ft penetration and had to be hammered. We never really established why, but two contributory reasons might have been, first, that we had female clutches leading and the outstanding clutch of the previous panel may well have become clogged; also there was a definite tendency for the piles to lean in the line of driving, so that if a panel finished with a slight lean and we attempted to keep the next one vertical, the connecting pile may well have acted as a wedge.93. In the second half of the job we arranged for male clutches to lead, and took greater care to keep the piles vertical, and the job went more expeditiously. Also we introduced a modified form of Pilemaster, so it is not possible to identify the cause of our previous difficulty nor what effected the cure. 94. The modified form of...