Correspondence. The Curzon Bridge at Allahabad and the Netravati Bridge at Mangalore.

Abstract

Mr. CLIFFORD BECKETT expressed the opinion that close attention should be given to the remarks made by the Author of the Paper on the Curzon bridge, that it was of the very greatest importance in designing wells for deep foundations to provide suflicient weight in the steining itself, instead of depending on artificial weight to complete the sinking. The latter course was not only very expensive in itself, but also represented money spent on work for which there was no return in the shape of added steining. The addition of artificial weight also occupied much time, and much was again lost in removing the weight after the sinking. When the bridges over the Orissa rivers were built,l the whole of the wells sunk under ordinary conditions, with certain exceptions, were filled with clean sand to within a short distance of the top of the steining. I n all cases where the wells rested on sand the settlement was so small during the erection of the superstructure as to be negligible, but in cases where the wells rested on clay settlement was observed. That was due he considered to the fact that during sinking in clay cavities were left round the curb into which the sand tended to escape, whereas in the former material the sand followed the well down and filled all cavities. When wells reited on sand, sand-filling might be used with economical results throughout the depth of the well, but in clay it was better to use a concrete plug, unless time could be given to permit of the settlement taking place. Wells were presumably used either to obtain a foundation below the limits of scour, or to obtain a foundation on better material than that available nearer the surface. I n either case protection against possible scour would be given round the wells on the surface. Should such scour extend to the level of the bottom, nothing in the shape of hearting would be of any avail to prevent the well so scoured from tilting, or to prevent loss of the whole well. If scour could not extend to the level of the bottom, and thus permit the sandfilling to escape, sand had proved in Mr. Beckett's experience as good a material as any other for filling throughout, provided time was given t o allow of its consolidation before the concrete cap was put on the well. Mr. Beckett's conclusions were :-1 W, T. C. Beckett, "The Bridges over the Orissa Rivers on the East Coast