Research Trends and Results

Technological Support Software on Calculationof Land Liquefaction Hazard for General Users
AKASHI Tatsuo (Dr. Eng.), HeadOHASHI Masamiki, Senior Researcher
Urban Planning Division, Urban Planning Department(Key words) Liquefaction, Housing site disaster prevention, Great East Japan Earthquake
1. Development of technological support
software
In ground liquefaction, although harm to human
lives is rare, in view of health damages such as
headaches and dizziness or the like and damage tohousing properties and so on, it brings on
tremendously big costs. For this reason, the City
bureau of the Ministry of Land, Infrastructure andTourism officially announced its Technical
Guidelines in Respect to Judgment for
Liquefaction Potential in Residential Land
(hereinafter referred to as Technical Guidelines)
in April 2013.
However, in order to conduct judgment
calculations in accordance with these Technical
Guidelines, the mathematical formulas and graphs
indicated in the Architecture Foundation Design
Guidelines of the Architectural Institute of Japanand the Specifications for Highway Bridges of theJapan Road Association are very complex andrequire specialized knowledge.
In order to solve this problem, the Urban
Planning Department of the National Institure forLand and Infrastructure Management hasdeveloped technological support software called
Judgment Calculation Sheet for Liquefaction
Damage Potential of Residential Land (hereinafterreferred to as the calculation software) to simply
conduct judgment calculations with data obtained
from ground investigations. The calculation
software has been configured based on Excel, withwhich most people have a general knowledge of.

Figure: Output image of calculation software
As shown in the figure, the calculation results
are indicated by visual graphs in tandem withnumerical values to make it apparent whether or
not there is a risk of liquefaction, using a scalewith intervals of 50cm under the surface ofground (whether the FL value is smaller than 1 orlarger than 1). Moreover, the calculation results
are plot-indicated in the judgment chart shown in
the technological guidelines, and copies of output
sheets are contrived to be used for conference
data of autonomous bodies.
2. For facilitation liquefaction hazard
map
For the prevention of liquefaction damage,ensuring an environment under which everybody
can be conscious about whether his or her land
has a risk of liquefaction is important.
The number of local governments whereliquefaction risk degree maps are prepared andpublicized in one way or another is 40 prefecturaland city governments and 282 municipalities as ofApril 2012, to the extent efforts have progressed.
However, the content of efforts varies according
to the local government. In particular, in quite afew cases the original sources to judge the risks
did not utilize boring investigations but wereprepared depending on simple methods such as
visual judgment of terrain. In addition, although
the existence or nonexistence of the occurrence ofliquefaction and the scale of damage varies
according to the scale of the presumed earthquake
vibration, there is no integrated concept;
furthermore, in the current situation the color
coding for maps varies considerably.
The Technical Guidelines prescribe the input
earthquake vibration to be the medium earthquake
vibration of Level 1 (maximum acceleration 200gal, magnitude in the epicenter 7.5). Although thisis considered to be an integrated scale in thefuture, since this is not a great earthquake, it
should be considered to be the lowest limit of thelevel of the countermeasure against liquefaction.
Inasmuch as the calculation software wedeveloped currently can readily be downloaded
from the Homepage of the National Institute forLand and Infrastructure Management, we expect
it to be utilized by many local governments andcitizens and that the configuration and publicationof liquefaction risk maps will progress based on
accumulated ground investigation information.
[Reference]
Homepage of the National Institute for Land andInfrastructure Management
http://www.nilim.go.jp/lab/jbg/takuti/takuti.html