Engineering Wonders of the World
Volume I

394 ENGINEERING WONDERS OF THE WORLD. Fig. 9.—SECTIONS OF ASSOUAN DAM AT A SLUICE AND BETWEEN SLUICES. had fallen below the top level of the sudds. Th© complementary sudds across each channel above, the site of the dam—to enclose the space to be occupied later by the foundations— were then built up quickly in the still water, in time to make full use of the low Nile period for the erection of the permanent structure (Fig. 8). The material employed for these stone sudds was brought down by rail from the right bank and tipped or thrown into the river over the end of the sudd as it advanced. The sudds were closed in order, one by one, starting from the right bank. In each case, as the channel grew narrower the dammed-up water rushed through the passage with increasing velocity. In closing the sudds across the Bab-el-Sughai- yar, stones weighing 3 to 4 tons, dropped in by a crane, not only failed to lodge in the gap, but were carried away bodily by the current. As the crane could not deal with heavier stones, progress came to a standstill. But this did not baffle the resources of the con- tractors. The railway lines were brought up to the very edge of the gap, and two wagons were loaded with wire-net bags, each con- taining from two to three tons of stone, ßrmly bound down to the wagons with steel ropes. The two wagons, weighing about 25 tons each, were then pushed over the end of the line into the gap. By reason of their great weight and size they lodged in the passage, and ren- dered the complete closing of the sudd possible. The finished sudds were about 30 feet wide at the top, had sides sloping down at an angle of about 45°, and attained a maximum height of about 49 feet. To strengthen them against the next flood season their tops were rendered with cement. On the down-stream slopes the stones were pitched or packed by hand, and steel rails were built in to hold the mass to- gether. In spite of all precautions, the sudd across the centre, or shallowest, of the three channels (the Bab-el-Haroum) was breached during the flood and washed away. It was, however, quickly rebuilt when the flood had subsided. In the third year, so soon as the river had fallen below the tops of these temporary dams or sudds, complemental sudds were constructed up-stream of the site of the dam, in the four summer channels. These were composed of bags filled with heavy granitic sand, brought on to the sudd in trucks, carried forward by native labourers, and thrown in at the ad- vancing end of the work. The up-stream sudds were 16 to 26 feet wide at the top, and had a maximum height of 60 feet. On the up-stream face the interstices between the sacks were filled with sand or granite chippings, and fin- ished to a slope of 2 to 1. The sand-bag sudds completed, the critical moment came for pumping out the water be- tween these temporary dams. From investigations made in Scotland in somewhat similar granite formations Fig. 10.—METHOD OF BUILDING FOUNDATIONS OF THE ASSOUAN DAM.