TUNNELING BENEATH CAIRO

The second phase of the Greater Cairo Metro system in Egypt included many geotechnical challenges. Thirteen kilometers of the 19-km heavy rail line were constructed underground within the water-bearing Nile Valley alluvium. The underground works included construction of cut-and-cover tunnels and stations using diaphragm walls, top-down methods, and state-of-the-art computerized injection grouting. Engineers devised an innovative new method that was successful in minimizing surface settlements for the project. In addition, the project featured the construction of special hand-mined connections to the bored tunnels, interesting tunnel boring machine entry and exit methods from underground stations, and a major building underpinning effort.