NEWBURN BRIDGE, NORTHUMBERLAND
Minutes of the Proceedings of the Institution of Civil Engineers
IN the construction of a road-bridge over the River Tyne at Newburn the foundations for the piers involved difficulty and expenditure quite disproportionate to the whole work. This was due in the first place to the intention of the Rirer Commissioners to increase the depth of water in the higher reaches. At the present time the river-bed is 5 feet above low-water level a t Newcastle and the intention is to dredge this to 12 feet below low-water. The strata below this depth consist of silt and
... nsist of silt and fine sand of a treacherous nature; it was therefore deemed advisable to carry the cylinders down to the rock. Preliminary borings were made on the site of each of the three piers; in two cases the existence of rock was proved within a very few inches of the depth anticipated, but in the deepest pier it was 8 feet lower. Each pier consists of a pair of wrought-iron cylinders 5 feet in external diameter, # inch thick, 1 9 feet 5 inches apart, in lengths of 4 feet, jointed vertically with T-bars 6 inches by 3 inches by 4 inch, and stiffened a t opposite points, with iron of the same section. A circumferential T-bar was riveted to each length, and this in erection was bolted to the adjacent length. Sinking was commenced at the north pier ; timber guide-squares being placed vertically, about 14 feet apart. Five lengths, i.e. 20 feet, of cylinder resting on the river-bed and held in position by the squares, were first erected, and open top sinking with a "Panton digger" was tried. The success of this method was not great, largely owing to the presence of gravel, which got between the jaws and permitted the escape of the material: but chiefly owing to nestingdue to the small size of the cylinder compared with that of the digger. It is probable that some of the more recent types of digger would have given better results. Weight was applied in the shape of kentledge-blocks 8 feet long, weighing 1 ton each, placed upon cast-iron rings fitting the top of each cylinder. On three or four occasions the cylinders were baled out and digging Downloaded by [ University of Liverpool] on [15/09/16].