The existing Salang tunnel connects Kabul to Northern Provinces of Afghanistan. The tunnel was built by Soviets engineers in 1964s and it is about 2600 m long. The tunnel is located at an altitude of 3400 m so that the portals and mountains are subjected to severe environmental conditions such as freezing and thawing process. As the traffic is heavy and the present tunnel is narrow, a new tunnel is planned by the Ministry of Public Works of Afghanistan using modern tunnel excavation techniques. The existing geotechnical data and newly gathered geotechnical and environmental data are used for rock engineering assessment of the tunnel. This study describes the rock engineering assessment of the existing Salang tunnel, mainly. The authors discuss the support system of the existing tunnel according to RMQR and other rock classification systems. They also estimate the response and stability of the existing tunnel through an integrated system of tunnel design incorporating the RMQR rock classification system and discuss its implications on the planned tunnels.
The existing Salang Tunnel is a 2.6 kilometer long and it is located at the Salang Pass in the Hindukush Mountains, between the Parwan and Baghlan Provinces. It is situated at kilometer 113.9 on the national route Kabul-Mazar-e-Sharif (AH76). It is a vital link connecting Afghanistan with central Asia and Russia. The tunnel has a north- northeast/south-southeast alignment with the approximately coordinates of E 69.06225° and N 35.29765°. The north and south portals of the tunnel have elevations of 3400 m and 3360 m, respectively. The tunnel has horseshoe cross-section with an approximate inner width of 7.20 m and it is about 7 m high. It has 15 avalanche galleries on the south side and 6 on the north side.
The Salang Tunnel passes through the Hindukush Mountains. The construction of the tunnel started in 1958 and it was opened in 1964 and provided a year- round connection from the Kabul to northern parts of the country and further to Uzbekistan and Tajikistan. However, it unfortunately suffered from explosions during the civil war and it was blocked to traffic from 1993 to 1998 due to a huge blasting, which caused heavy damage in the tunnel.
