Bosai Solution ID : JBP00080

Slope Stabilization Anchor Work / Water Collection Well
Construction for Landslide Prevention
Dual Tube Rotary Percussion Drilling Method by the Arrow Drill (RotaryPercussion Drill)

HazardEarthquake Tsunami Land Slide

Solution Purpose
Prevention & Mitigation Recovery

Solution Theme
Infrastructure Technology Building Technology＜ Downloaded from www.bosai-jp.org ＞

1/5

Technology Subject
Road Railways Facility for Disaster Prevention

Advantages
The Arrow Drill (Rotary Percussion Drill) having rotation, feed and percussion mechanism rapidly drills aborehole to install a work object (anchor body or water drainage pipe) in the slope stabilization anchor
work or the water collection well construction for landslide prevention.
The work object is installed securely through the outer rods remained in the borehole, which prevents
borehole wall from collapsing.

Solution Illustrated
Slope Stabilization Anchor
The slope stabilization anchor is the method tocounteract the landslide force using the tensile
strength of the anchor body rooted in the basement.
After drilling an anchor hole with the dual tube rotary
percussion drilling method, the inner rods are fully
retracted and the anchor body is installed through theouter rods. Grouting is done during the outer rods
retracting.

Water Collection Well
The water collection well is the method to slow down and/or prevent landslide activity by draining
ground water above the slip surface.
Several dewatering holes are drilled horizontally but slightly upward direction and fan-shapely in thewater collection well (the vertical shaft).

＜ Downloaded from www.bosai-jp.org ＞

2/5

After drilling a dewatering hole with the dual tube rotary percussion drilling method, the inner rods are
fully retracted and the water drainage pipes are installed through the outer rods. The outer rods are
retracted remaining the water drainage pipes in a borehole.

BackgroundThe slope disaster broken out by an earthquake and/or a concentrated heavy rain causes serious
damage in various places regardless of domestic and overseas.
According to HP of the Ministry of Land, Infrastructure, Transport and Tourism, however, there areapproximately 1.1 million spots in danger of landslide outbreak, in which the ratio of countermeasurestaken is only 23 %, therefore it is required to take prompt countermeasures.
Originally, the single tube rotary drilling method is applied for a borehole drilling, so that the collapse of
the borehole wall used to occur depending on the geological character resulting that the drilling to thepredetermined depth or the installation of the work object into the drilled borehole has difficulty
In the dual tube rotary percussion drilling method, the work object is installed safely and securely underprotection of the borehole wall by the outer rods, then it can save the time and effort of washing and/or
re-drilling.
The percussion function, furthermore, leads high drilling performance even in the strongly collapsible
strata and the hard rock or boulders zone, and then the construction time shall be reduced.

Exposition of the Solution

The dedicated drilling tools are basically composed of the inner and outer strings, and drilling is done in
the state of the dual tube strings.
From the inlet port of the cleaning swivel, the drilling water is sent into the inner rod.
With the drilling water, cuttings (slime) crushed by the inner and outer bits are removed from theborehole bottom and discharged from the cleaning swivel outlet port through the gap of the inner andouter rods.

＜ Downloaded from www.bosai-jp.org ＞

3/5

When the drilling is completed to a predetermined depth, the inner rods are fully retracted and the work
object is inserted to the borehole bottom through the outer rods.
Because the outer rods protect the borehole wall, the work object can be inserted smoothly without any
trouble such as borehole wall collapse.

Achievements of Examples
In 2012, at Tegucigalpa, the capital of Honduras Republic, “the Project for Landslide Prevention inTegucigalpa metropolitan area” founded by the Japanese Grant Aid program has been executed.
In this project, the method to install a plurality of "water collection well" with "fan-shapely arranged
water drainage holes" was adopted for the first time in the Central American region, thus the Allow Drill(Rotary Percussion Drill) has been utilized successfully and effectively.

＜ Downloaded from www.bosai-jp.org ＞

4/5

Corporate Profile
Koken Boring Machine Co., Ltd.
1F Mejiro Nakano Bldg, 2-17-22 Takada, Toshima-ku, Tokyo 171-8572, JAPAN Tel. : +81-3-6907-7515
 E-mail : abe@koken-boring.co.jp
 Website : http://www.koken-boring.co.jp/e/index.htm＜ Downloaded from www.bosai-jp.org ＞

5/5