Salt-Corroded Tunnel Undergoes Major Renovation

Kajima is leading a Japanese government funded project to renovate Egypt's Ahmed Hamdi Tunnel, seriously corroded by years of salt water leakage. The rebuilt tunnel (right) is scheduled to be completed this fall.

Constructed in 1983, the 1,640m-long Ahmed Hamdi Tunnel traverses the Suez Canal at the port city of Suez and is part of the only contiguous land route from Cairo to the popular Sinai resort of Sharm el Sheikh as well as the holy city of Mecca. Just a few years after the tunnel opened, however, it was discovered that salt water leakage has caused serious corrosion to more than half of its concrete segments and reinforcement bars. The problem became so severe that salt stalactites as long as one meter were found hanging from the ceiling and more than 80 kg of salt were recovered from the tunnel lining each day. In 1992 a Japanese government-funded renovation project was launched, with Kajima serving as general contractor. The rebuilt tunnel is scheduled to be completed this fall.

The basic construction plan involved first installing 2mm-thick waterproof sheeting along the inside of the existing tunnel lining to shut out and channel leaking water to a sump pump drainage system at the base of the tunnel. A secondary reinforced concrete tunnel lining was then constructed inside the original one, with the waterproof sheeting sandwiched in between. The secondary lining was designed to be structurally independent of the existing tunnel segments, with continuous longitudinal reinforcement bars running the full length of the tunnel helping to provide resistance to any uplift caused by future expansion of the canal.

Although the tunnel was closed at night to allow full-scale construction operations, construction of a 240m-long two-lane temporary roadway permitted daytime use while construction continued underneath on the lower portion of the tunnel. The temporary roadway was moved 7.2 meters each night as work progressed. The renovation necessitated removing the existing precast concrete roadbed slabs. The 2.4-long, three-piece slab sections, each of which was secured by vertical anchor bolts, were pushed up one at a time by a traveling hydraulic jack and removed by an 18 ton forklift.

In light of the damage to the tunnel caused by high salt concentration, the salinity of the concrete used in renovation was carefully controlled. The ground at the quarries from which the aggregates were taken was tested for salt content, and additional tests were conducted on the materials at the stockyard and following mixing operations. As a result of these measures, the salt content of the concrete was held to less than 0.3 kg/m3, well below the standard 0.6 kg/m3.

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