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Longest railway tunnel bored in East Africa completed

The China Communications Construction Company (CCCC) has announced that it has bored the longest railway tunnel in East Africa.

The 4.5km single track railway tunnel is part of Phase 2A of the Standard Gauge Railway (SGR) that will operate from Nairobi to Naivasha town.

CCCC SGR project general manager An Aijun said: “With a total length of 4.5 km, the Ngong tunnel is currently the longest tunnel in East Africa and the dominant work in SGR Phase 2A.”

It is the first time the New Austrian Tunneling Method (NATM) of drilling and blasting has been used to build a tunnel in Kenya.

According to CCCC, during the excavation, the project team had to overcome water leaks, uneven pressure, shallow-depth excavation, surrounding rocks, structural fault-line, and navigate oil pipeline protection.

CCCC Kenya SGR project spokesperson Steve Zhao explained that 146 refuge holes of different sizes have been built within the tunnel to allow maintenance workers to take cover as the train approaches.

He said: “There is one large refuge hole set up every 150m in the tunnel, and one small refuge hole set up every 30m in the tunnel.”

“A 533m wide emergency rescue channel has also been built within the tunnel, to allow for vehicle access in case of emergencies.

“We have reserved space to install fans within the tunnel. Six jet fans can be installed to ensure air ventilation once the tunnel is operational,” added Zhao.

The entire Phase 2A is around 120 km is set to be completed in 2019.

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