Minutes of Proceedings of the Institution of Civil Engineers Volume 122 (Paperback)

This historic book may have numerous typos and missing text. Purchasers can download a free scanned copy of the original book (without typos) from the publisher. Not indexed. Not illustrated. 1895 Excerpt: ... inches up-stream from its true position, and afterwards moved down by wedging. If placed out of position down stream its adjustment is difficult. To prevent the cylindrical column from being forced upwards by air-pressure, and to insure its descent as the sinking proceeds, it is loaded until it overcomes skinfriction and other resistance, whilst yet thoroughly under control so that it may be readily hung up when necessary. If the loading is insufficient, the column may be lifted with an increase of airpressure or may fail to descend as the excavation below it is performed, in which event an inrush of drift may occur if the ground is loose. Under favourable conditions concrete loading is sufficient, but where more weight is necessary, rails or other available materials are placed on staging attached to the air-lock bed-plate. In applying the concrete loading which forms part of the permanent filling, a feature called the "bell" is first formed. This is done by setting up an internal frame of " bell-irons," conlisting of 2-inch by -inch rods bolted to the flange of the cuttingring joint, sloping upwards at an angle of 60 towards and bolted to an angle-bar ring 2 inches by inch and 18 inches in diameter, placed horizontally in the middle of the cylinder. Tapering lagging-boards 1 inch thick are then laid over the sloping iron frame which connects the flange of the cylinder with the ring, and upon the lagging concrete is laid. A length of tube, 18 inches in diameter, made of 3-inch by 1-inch timber staves, 6 feet long, bound with light hoop-iron, is then set up above the central ring, and is kept concentric with the cylinder. The annular space between the tube and the cylinder is filled with concrete, another similar length of ...