ABSTRACT
As the number of tunnels with considerably close separation distance increases in consideration for inferior ground conditions, civil complaints, minimization of environmental impact, etc., application of the 2-arch tunnel has recently been on the rise. Most of current 2-arch tunnels are a 2 arch-1 pilot that utilizes supporting function of the central wall. 2 arch-1 pilot tunnels are, however, complex in constructing the central tunnel and inherent with issues such as waterproofing-drainage. To this end, this research aims to present an improved 2-arch tunnel design method capable of attaining safety, constructability, and economic efficiency.
