Kenya now boasts in having the longest railway tunnel in East Africa and second in Africa after South Africa.
China Construction Company on Monday announced the successful drilling of the 4.5km tunnel at Embulbul in Kajiado County.
This is the first of the three sections of the 7.14 km SGR tunnel expected after the completion of the second phase of the standard gauge railway running from Nairobi to Naivasha covering a total distance of 120 km.
The 4.5 Ngong tunnel is designed as a single track railway tunnel comprising of three sets: a 4.5 kilometer stretch with a buried depth of 108 meters; a 1km with a buried depth of 46 meters, and another 1.64km stretch.
Its construction adopted the New Australian Tunneling Method (NATM), of drilling and blasting to build the tunnel. This is the first time that such a method has been used on such a large scale in Kenya.
“The tunneling method is economical, efficient and has strong adaptability for different geological and groundwater conditions. What’s more, the method controls surface collapse effectively and enhances the working environment during construction.”
— CCCC SGR Head Office (@SGRHeadOffice) September 24, 2018
NATM was first developed in Austria and has been adopted globally in constructing underground passages for rail and road; dug through hills, rivers as well as other roads.
The excavation is done by drilling holes into the rock face then charging the holes with explosives, which are then blasted. Following this process, ventilation is done before the short firer re-enters.
Two more tunnels measuring 2.64km will be constructed along the 120km Naivasha- Nairobi SGR Route.