Effects of pipe roof supports and the tunnels excavation on the ground settlement

Tunneling is one of the challenging tasks in civil engineering because it involves a variety of decision making and engineering judgment based on prediction and experience. One of the challenges is to construct tunnel under a sensitive area with shallow overburden in which the ground settlement is inevitable. This paper discussed the interaction between twin parallel tunnels with shallow overburden and the tunnel supports parameters that provide information on ground settlement prediction using 2-D elasto-plastic finite element analysis. The objective of this study is to determine the magnitude of ground settlement induced by the interaction between a twin parallel tunnel that supported by a method called pipe roof system. The system acts as a support to protect the above ground structure during tunnel excavation with different horizontal spacing at a constant depth of 10 m. Composite 'beam' is designed to represent the pipe roof system which consists of steel pipes, grout infill and rock properties that were combined using weighted averages and an equivalent rock mass strength derivation. The result shows a different value of ground settlement at different spacing between the tunnels with and without the pipe roof system. The highest magnitude of settlement recorded for pipe roof and non-pipe roof tunnel were 6.8 × 10-3 mm and 8.1 × 10-3 respectively. The result obtained delivers a great portion of engineering justification that may help engineer to make important decisions during the planning, design and construction stages of tunnels with shallow overburden.