Restoration efforts of the Aso Bridge District
affected by a massive landslide
阿蘇大橋地区大規模崩壊斜面の復旧状況について

Sand control group, Kumamoto branch office, Kumamoto earthquake
counterplan office , Kyushu Regional Development Bureau, MLIT
国土交通省 九州地方整備局 熊本地震災害対策推進室 熊本分室 砂防班

Overview of the landside＜Dates of the disaster＞
1:25 a.m.April 16th 2016
※Occurrence of a quake＜Damages＞
・Public infrastructure
National Road no. 57（Aso bridge area）
National road 325 Aso Bridge
Japan Railway Houhi Line
＜Scale of landslide＞
・LengthLength of landslide approx.700m
・Width of landslide approx.200m
・Volume of earth and sandapprox. 0.5 million m3（E i（Estimationi bby aerial
i l llaser measurement
soon after the quake）

Kyushu Regional
Development
九州地方整備局
Office, MLIT

Damages by the collapse at Aso Bridge area

Kyushu Regional
Development
九州地方整備局
Office, MLIT

Direction of Oita
57

57

Direction of Kumamoto

The Kurokawa River325

Direction of Miyazaki

Kyushu Regional
Development
九州地方整備局
Office, MLIT

Status of the collapse of slope
Photographed by the Harukaze, Kyushu
regional development bureau,MLIT

Length of the collapse: approx.700m

Width :approx. 200mPhoto③

Photo① Landslide at the top
Photo②

Photo①

Photo② Top of the collapsed cliff Photo③ Cracks near the collapsed cliff

In regard to the massive collapse of the slope at Aso bridge area triggered by the Kumamoto earthquakes in 2016,
emergency construction works are underway to prevent secondary disasters that could be caused by collapse ofthe remaining large volume of sand at upper area of the slope
O
Overview
i off llandslide
d lid didisastert

Overview of the countermeasures

Tateno, Aso village, Aso County, Kumamoto Prefecture○April,16m 2016,Kumamoto earthquake○Status of damages
National road no.57,National road no.325, Ｊapanrailway Houhi line
○Major countermeasure works
Earthworks and building of mounds, Slope protection
works（Cost ：Two billions）○Start of the works: May 5th ,2016○○Due
to the cracks as well as unstable earth and sand, left
at the top of the slope, the works are undertaken by using
construction machines for automatic operation.

◆Installation of mounds against falling rocks
and collapse of unstable sand◆Removing of the unstable sand at
upper side, followed by the slope
protection works

Status of the works

Steps of the works◆Eliminating unstable sandPhotographed on Oct. 2nd◆Completed mounds
Upper side

Installation ofmonitoring system

Oita→

Developing passages forthe works←Kumamoto
B ildi
Buildingoff moundsdElimination of unstable sandSlope protection works

Status of installation
Eliminationof unstableofrocks
mounds:leftcompleted
by gullyat the end
erosionof October←KumamotoMounds

３ｍ

３ｍ
ｍ

5～9ｍ

Kyushu Regional
Development
九州地方整備局
Office, MLIT

Oita→

Kyushu Regional
Development
九州地方整備局
Office, MLIT

Operation of the unmanned machine for construction works
Operated by using four monitors for one unmanned machine

Images from thevehicle carrying
cameraOperation deskfor 14 unmannedmachines

Heavy machines
photographedfrom just in front
Monitoringg otherunmanned machine
Zooming
Monitoring camera（capable of multi angleoperation）

Camera vehicle

An overview of the unmanned construction system
Networked system for unmanned construction

Kyushu Regional
Development
九州地方整備局
Office, MLIT
Camera located at thetop

Operation roomb x cable（７００ｍ）
bl （７００ ）Opticall ffiberRadio station②

Relay station①

Area of the works

LAN cable

d station
Radio①

Relay station②

Radio station④
Radio station③

Relay station③

LAN cable

High speed wireless access system

Relay station④

Camera at theopposite side

Relay station

Operation room
Optical fiber
Cable (700m)

Area of the works

Radio Station
Highg speedpwirelessAccess system
ＬＡＮ cable

Wireless ＬＡＮArea of the works of eliminating unstable earth and sand(2) Upper border of the works

 Area of the works

Kyushu RegionalDevelopment
九州地方整備局
Office, MLIT

 Block ①-2:
① 2: Upper border is defined up to the crack of the unstable block,block

Surface layer of andosol, deposited earth and sand （d(An））, and pumicefound at the areas surrounding the collapsed points where the ground rises
A cross section
ti ffor eliminationli i ti off earth
th andd sandd
Area for eliminating sanddue to the changes identified by dynamic observation, and the significant
difference in level between the cracks behind.
 Brock ①-1,Block①-3: Basically the area cut from the lower border at
 a stable gradient of one in two, with necessary adjustment depending on
the status of the ground at the back during the works.

 Eliminating the surface layer, d(An)layer andpumice near the collapsed points at a slope of one in two

Andosol
Deposited earth & sand d(An)Andesite(An)The ground before thecollapse：Area for elimination： Cracks

Tuff bressia,volcanic bressia

Pumices that could trigger falling of rocks(1) Lower border of the works
 Lower border of elimination wasLower border of elimination

defined by measuring the collapsed
surface by UAV, and examining thestatus of pumice that could trigger
falling of stones.

Status of the works for eliminating unstable earth and sandOverview of method of construction〔Safety climber method〕

Kyushu Regional
Development
九州地方整備局
Office, MLIT

Kyushu Regional
Development
Office, MLIT

Status of the works for eliminating unstable earth and sandBefore the works

August 23rd•••

Elimination of unstable sands, stones that may trigger falling of stones
Start of works: August 31th by using three slope power shovel at height
Completed in two months and half on November 10thLower border ofthe works

Status of works (Excavator no.1）
Oct.25th

Status of works (Excavator, no.2 and No.3） Oct.25th

Status ofthe worksthkOctober 25thPowershovel no.3PPowershovel no.2

Power shovel
no.1

Kyushu Regional
Development
九州地方整備局
Office, MLIT

Elimination of unstable rocks left by gully erosion
Before the rainfall, June 17th

After the rainfall,, June 27th

①

②

④

③

Heavy rainfall on June 20th accelerated the gully erosion

Rock climbing method of construction①Unstable rock at the top ofgully② Softening of
exposed andesite bedrock③ Softening ofExposed andesite bedrock④Sedimentation of collapsed
sand in the gully