A Treatise On The Principles And Practice Of Dock Engineering

CONSTRUCTION WITH MONOLITHIC BLOCKS. 211 which were afterwards used for the reception of 10-inch square stone dowels, 3 to 4 feet long, to connect adjoining lengths. The ends of two small wrought-iron girders in recesses, at or near the bottom of each block, rested in the stirrup-rods, and all were withdrawn together at the close of the setting operations. The superstructure consisted of a facing of regularly coursed limestone ashlar, backed by 6 to 1 concrete, with a coping of Cornish granite. Another instance of monolithic construction, with yet smaller blocks of concrete, is to be found at Kurrachee (tig- 150). The dimensions of the blocks were 12 feet by 8 feet by 4J feet, and their weight 27 tons each. Lifting and setting were performed entirely by land carriage with the aid of a Titan, which travelled over the sections of work already executed and deposited the blocks in front of it. The depth of the foundation bed was 15 feet below the surface level of the water, and the blocks were laid in three horizontal tiers or courses to a total height of 24 feet 6 inches. The blocks were not set vertically, but with a slight backward inclination as shown in fig. 150. The sea bottom was sandy at a depth of 25 to 30 feet, and was surmounted with a rubble foundation, levelled by divers, and upon which the blocks were laid. Fig. 148. Fig. 149. Fig. 150. —Blockwork at Kurrachee. A similar method was adopted for building the quay walls at Suez. The blocks, whicli were about the same size as those at Kurrachee, were conveyed to their destination in barges. Other examples may be quoted from ports in the Mediterranean, at Marseilles and elsewhere. The French were, in fact, the pioneers of the system, when they inaugurated it at Algiers as far back as the year 1840. It is still being practised for harbour work in Algeria at the present time, and the following particulars, furnished by the courtesy of the Engineer in charge, M. Georges Boisnier, relate to a quay wall at the port of Bougie, now under construction (see fig. 151). The sea bottom is mud to a considérable depth, and in order to obtain a sufficiently broad area for the pressure, a foundation of rubble stone, 11^ feet in depth, is deposited within a trench dredged to a bottom width of 55 feet. The wall consists of five tiers of masonry blocks of varying size, only one of which is above the surface of the water. The blocks are constructed on a neighbouring quay with limestone from a local quarry. Those in the