1.These canals are frequently excavated through rock , and require tunnels, flumes, syphons, aqueducts and open concrete-lined channels .
这些水渠往往要凿通岩石,并需要地道、引水沟、弯管、渡漕和混凝土水道。
2.Screwed scaling plugs for syphons of drain fittings - Part 1: Plugs of copper-zinc alloy
排水弯管配件用螺纹密封塞.第1部分:铜锌合金塞