Research Trends and Results

Estimate of volume of debris on the road afterearthquake
MABUCHI Toshiaki, Senior Researcher
KANEKO Masahiro, Researcher
Earthquake Disaster Prevention Division, Research Center for Disaster Management(keywords) earthquake debris, road emergency, estimation method
1.

Introduction
For earthquakes which occur in urban areas such as
earthquakes that directly hits Tokyo area and earthquakethat directly hits Chubu area・Kinki area, it is extremely
important to immediately eliminate road obstacles foremergency routes, etc. in view of the magnitude of theimpacts on society, etc. following the earthquake. In
this research, as basic data necessary for planning in
relation to actions of road administrators after earthquake
such as elimination of road obstacles and with the objectof earthquakes which occur in urban areas, obstacles(earthquake debris and neglected vehicles) which cause
decreased function of road transportation system on
emegency routes, etc. and the extent of decreased
function were clarified and its estimation method wasstudied.
2. Organizing actual conditions of earthquake debris
occurred on main roadsActual conditions of earthquake debris occurred on themain roads by the collaping of buildings, etc. by the roadside were organized by deciphering aerial photgraphs
taken of the 1995 Hyogo-ken Nanbu Earthquake.
Information on width and length, etc. of protruded
earthquake debris on the road and the properties ofcollapsed buildings (wooden・non-wooden, low-rise・highrise), etc. were summed up as follows.
(1) Frequency of occurrence of earthquake debris on
main roads per length of road 4 (items / km) at most andcomparatively lower than narrow streets(1).
(2) There was not much difference in length of protrusion
between wooden and non-wooden.
3. Formulation of estimate equation of volume ofearthquake debris on main roads‘Building-to-land ratio’, ‘floor area ratio’ and ‘use
district’, etc. which data were relatively easily available
from city planning summary drawings, etc. used asvariables in order to estimate volume of debris. In
estimating the width of earthquake debris (a), a
coefficient of each variable was calculated by regression
analysis and (Formula-1) was set up.
a = - 3.479 + 0.621・X1 + 7.509・X2/100+ 0.607・X3/100 + X4・・・(Formula-1)
X1: number of building stories X2: building-to-landratio (%) X3: floor area ratio (%)
X4: use district: residential district: 0.585, neiborhoodbusiness district: -0.311, business district: -2.585,
semi-industrial district: 1.155, industrial district: 2.857
Height of debris (h(m)) and length of debris (L(m))

were used as a function of width of debris (a(m)) andfollowing (Formula-2 and 3) were set up by regressionanalysis using the measured values. In addition,
assuming that debris are triangular prisms, volume (V(m3)) can be obtained as (Formula-4) using width ofdebris (a), height of debris (h) and length of debris (L).
h = 0.32・a + 0.853
・・・(Formula-2)
L = 1.089・a + 7.487
・・・(Formula-3)
V = a×h×L / 2・・・(Formula-4)
4. Forecasting method of neglected vehicle quantity
In order to forecast quantity of neglected vehicles intime of earthquake disasters, the generation status wasinvestigated utilizing aerial photgraphs at the time of
Hyogo-ken Nanbu Earthquake.
Comparing thephotographs taken in the afternoon of January 17, the dayof Hyogo-ken Nanbu Earthquake with the photographs
taken in the morning of next day 18th, if there werevehicles on the same place, they were regarded asneglected vehicles and the result of discriminatedquantity of neglected vehicles was listed in the Table.
Since the earthquake occurred early in the morning, thenumber of neglected vehicles was not so many.
Table: Generation status of neglected vehicles by
aerial phtograph discriminationRoutes
National Route 2 (Directcontrol national route)
Yamate-kansen Route(main local roads)

BlocklengthNumber Number/length19.2 km52

2.7 / km12.5 km78

6.2 / km

5. Conclusion
By discrimating aerial photographs at the time of
Hyogo-ken Nanbu Earthquake, the generation status ofearthquake debris on the main roads, etc. caused bycollapsed buildings, etc. by the road side was organized
and the estimate equation was formulated. In addition,
it generated the quantity of organized neglected vehicles.
It is hoped that the above will enable to forecast volumeof debris, etc. on roads post-earthquake to some extent
will contribute to advance preparation of equipment, etc.
necessary for elimination of debris, etc.
[Reference] (1) Functional disorder of street network and its
influence focusing on ‘street blockades phenomenon’ inHanshin Awaji Earthquake, Japan Society Civil Engineering
Journal, October, 1997 Hitoshi IEDA et.al