| Subhorizontal drains installed from the ground surface or drainage wells are one of the most common landslide measures. The drainage drill hole is supported with a casing pipe, which is conventionally perforated with small holes in all direction for inflow of underground water into the casing pipe.Since before, it had been pointed out for the underground water not to flow in easily into the casing pipe, and for the collected water to flow out of the pipe to some extent.In 2007, a new type of casing pipe (that is called “Mizutooru” casing pipe for drill-hole drains; hereinafter abbreviated as MT pipe) wasdeveloped and that drastically improved the function of underground water collection and drainage. The total construction extension of the MT pipe reached 230km up to date.Comparison between MT pipes and the conventional drain pipes |
