... )Water conservancy 4)Coal mine, Civil use,Military use Metallic corrugated pipe Application fields:1.Highway and railway: culvert, passage, bridge, ... drainage pipeline4. Coal mine: minerals transporting pipeline, workers and mining machine passage, aven/shaft5. Civil use: smoke duct for power plant ... military sidewalk, air-defense passage, evacuation passageblack, white black Metallic corrugated pipe