Long distance drainage pipe
When tunnel excavation encounters fractured geology combined with the presence of high-pressure ground water, the umbrella pipe roofing system and/or face stabilization system using the longer distance drainage pipes can be applied to release the water pressure behind the tunnel excavation face. This is an effective way to prevent the tunnel from collapse. Designed to be installed by our NATMTECH single-pass drill system, the drainage pipes are connected in order to not only cover a longer distance, but also shorten the installation time.
Safety/Quality Approval
◎ 2.5” drill system – borehole diameter 90mm, drainage pipe diameter 76mm, piecewise length 3.0m
◎ 4.0” drill system – borehole diameter 125mm, drainage pipe diameter 114.3mm, piecewise length 3.05m
◎ Pipe length depends on the geology condition. However, for the sake of drill precision, L ≤ 18m is recommended.
◎ Steel pipes with grades EN S235; thickness at 5.0mm minimum for thread machining
◎ ABS pipes with thickness at 6.0mm is recommended for use as face drainage, with the consideration of cutting off afterwards
◎ Drainage hole fabrication: D10mm holes*2 and reversed 90° at every 100mm interval
◎ To prevent sands or very fine particles from being drained out with underground water, drainage pipes with slit (≤1.0mm) or filter pipes to be inserted into the outer drainage pipes afterwards are also available on request.
