314-2 Micro Tunnel Boring Technology

Description

Development of technology for boring micro tunnels of up to 1.8m diameter in bedrock over distances of 1-3 km.

Boring over distances of 1 - 3 km.
Tunnels bored without support and staging. Generally lined with sprayed concrete, however it is desirable that precast concrete sections be used in place of on-site concrete in inverted sections.
The small diameter TBM method is more economic than either the fluid transport TBM method or the blasting method for small diameter boring.
Case studies of boring tunnels over distances of 1-3 km show that use of the fluid transport TBM method reduces the construction period by half, and ensures economics of between 20% and 100%, in comparison with blasting (one-way excavation).
Tunnel diameters of 1.0 - 1.8m suitable for maximum flows of 0.5 - 2.0 m³/sec.

New Energy Foundation, Hydroelectric Power Development Center — www.nef.or.jp

Japan