A Treatise On The Principles And Practice Of Dock Engineering

266 DOCK ENGINEERING. inserted and other preventive steps taken. Pumping was reduced to the minimum necessary for getting in a piled foundation for the side walls at the highest possible level. The holes were filled with chalk rubble and the wliole area covered with it in order to intercept the flow of silt. Bearing piles were then driven between a network of temporary timbering, connected at the top by whole timber caps and covered with a double thickness of elm planking. As regards the origin of the water in the blows, investigations seemed to indicate the existence of parallel water-courses below the bed of clay running transversely to the lock. The principal difficulty being anticipated at the inner gate platform, it was proposed to excavate the foundation in small areas, enclosed by half timber sheeting, grooved and tongued, but after a few piles had been driven some blows occurred at the surface, which was a little above dock bottom, and water came up in considérable quantities. Large holes formed, and some of the sheeting disappeared. Cast-iron pipes were driven vertically into the two principal springs, and in one of these the water reached a height of 14 feet above dock bottom. Several hundred yards of clay puddle were absorbed by one hole alone. To reach the origin of the disturbance it was clearly necessary to carry the sheeting lower down, and accordingly pitch pine piles, 14 inches square and 50 feet long, grooved and tongued, were driven so as to enclose the disturbed area and eut off the flow of water, which was effectively done and the foundations completed. The roller path stones and sills were laid on elm platforms over bearing piles. The discharge through one of the blowhole pipes was stopped, but the water continued to flow through the other until the pipe was closed at the completion of the works. New Lock at Bremerhaven. This lock (fig. 206) has an efficient length of 656 feet, or a length of 705 feet between gates. The breadtli of the entrance is 92 feet, and of the chamber 147 feet, so that the largest passenger steamers can lie there preparatory to starting and receive cargo from lighters. The depth is sufficient to accommodate ships drawing 31 feet during neap tides. An