Engineering Wonders of the World
Volume I

TSE ROTHERHITHE TUNNEL. 53 the depth of the cut-and-cover work at the Rotherhithe Tunnel this would have had to be done in any case. After the work is completed the land is again available for building. The trenches excavated for the cut-and- cover were 35 feet wide, and varied in depth of 2 feet thick brickwork in the form of a complete circle 27 feet in internal diameter. Outside the brickwork is a layer of asphalt, to keep out the water, and outside the asphalt a backing of concrete, to protect the asphalt and give additional stiffness to the tunnel. As the masonry rose, the timbers supporting DECKING OF CAISSON, NO. 1 SHAFT. from 35 to 56 feet. The sides were supported by heavy timbers, and the water which came in from the Thames ballast was conducted by pipes to sumps or wells, from which it was pumped to the surface. As soon as a length of trench was ready, the building of the tunnel began. Instead of iron, the lining is here the sides were taken out, and when the arch had been completed and covered with asphalt and concrete, the space above was filled up to ground-level with earth. Great care had to be taken with this part of the work, as in many places large and heavy buildings stood quite near the tunnel, and were liable to