Assessment of Potential Tunneling Hazards for the New Railway Tunnel in Ethiopia

Abstract

The knowledge of potential tunneling hazards plays an important role in the selection of excavation method and designing a support system for underground openings. Failure of a rock mass will occur when the in-situ stress exceeds the in-situ rock mass strength. Nowadays, Ethiopia is trying to construct a newly planned railway route to connect the country’s development centers and link with ports of neighboring countries. However, this newly planned railway route will pass through the heart of highly fragile mountainous terrains and earthquake prone regions. Therefore, a study of potential Hazards for the new railway tunnel (T-07) at a particular critical section has been done by using two commercially available programs (Rocsupport and Phase2). The final Tunnel Convergence of the railway tunnel was found to be 1.11% (using Rocsupport) and 1.59% (using Phase2 finite element analysis).This discrepancy is attributed to the assumptions made in the Rocsupport software. Based on the results, a minor squeezing problem will be expected in this particular rail way tunnel section. Finally, a safe and economical reinforced concrete support type was recommended based upon the numerical analysis.