 |
 |
 |
The earthquake this time was the directly-under-city type
which struck directly a key traffic point city. It caused the destruction of
not only many structures such as houses and the suspension of vital networks
but also the collapse of the traffic network including the shinkan-sen line,
loss of functions of Kobe Port which is a representative port of Japan and the
effect of the earthquake extended on a nation-wide scale.
In consideration of the immense damage caused by the earthquake, it is extremely
important to realize further reinforcement and improvement of earthquake resistance
for the infrastructure for the traffic such as the railway and port including
the existing facilities.
Furthermore, as the port has played a great role in rehabilitation of people's
living through marine transport of emergency goods, provision of sites for temporary
housing, etc., it is also important not only to reinforce the earthquake resistance
of berths but also to improve ports as the emergency utilities bases on the
city for the purpose of increasing the function of prevention of disaster in
Japan in which many big cities have their own port.
On the other hand, in order to take measures against earthquake disaster
it is vital to establish a competent system for forecasts and warning and prediction
of earthquake and tsunami and it is necessary to strengthen such a system.
In addition, regarding the system on the part of the administration at the
time of earthquake disaster, it was strongly recognized that it is important
to reexamine the plan for disaster prevention, strengthen the systern of collection
of information and reporting and increase of vessels and helicopter for relief
activities.
(1) Studies on the earthquake resistance of railway facilities
In Japan which is one of the countries most frequently attacked by earthquakes,
more than 40 earthquakes which exceeded the 5th degree of seismic intensity
occurred along railway lines since the opening of the railway system and the
earthquakes which exerted damage to railways exceeded 20.
From the experiences in damage caused by such large-scale earthquakes as
the Niigata Earthquake (1964, Magnitude 7.5), Sea off Tokachi Earthquake (1968,
Magnitude 7.9) and Sea off Miyagi Prefecture Earthquake (1978, Magnitude 7.4),
studies on the improvement of earthquake resistance of railways such as the
earthquake-resistant structure for the railway structure on the soft ground
have developed in Japan.
Studies have been vigorously conducted on the measures for the reinforcement
of earthquake resistance of Tokaido Shinkansen line and others against the Tokai
Earthquake which is predicted to occur (Picture.4).
For example, the method of construction with enclosure by steel sheet piles
has been developed as a measure against the breaking of embankment on the weak
ground and the subsidence of the embankment behind abutments of bridges. The
results of these developments have already been adopted for Tokaido Shinkansen
line in the areas under intensified measures against earthquake disasters.
Henceforth, it has been decided that efforts be made to elucidate further
the causes of damages to structures in the Hanshin-Awaji Great Earthquake Damage,
which was a directly-under-city type and, by addition of new results of studies,
to clarify how new earth-quake resistant structures for the railway facilities
should be.
(2) Improvement of the earthquake resistance of railway facilities
Regarding the improvement of the earthquake resistance of railway facilities,
the Railway Facilities Aseimic Structure Investigation Committee announced on
July 26 the tentative measures to be taken before the establishment of new method
for earthquake-resistant design and decided to apply, with necessary amendments,
the "Special Design Specifications for Restoration of Railway Structures Damaged
by the Hanshin-Awaji Great Earthquake Disaster" to elevated bridges, open cut
tunnels, and others which are newly constructed aiming at making them fully
durable against any earthquake shnilar to this time. The committe.e also proposed
that reinforcement of resistance against earthquake be made to prevent the structure
from collapse by any earth-quake of this size for existing elevated bridges
and open cut tunnels, etc. for the shinkansen lines and the lines with great
volume of traffic and that such reinforcement works be completed approximately
within 3 years for the shinkansen lines and 5 years for other railway lines.
Based on the proposal, the plan for emergency reinforcement of earthquake
resistance of the existing railway structures for the total of 31 corporations
consisting of 3 JR companies, 21 private railway companies, 7 subway corporations
include public corporation and TRTA was drawn up on August 24 (Table
lO). Each railway company has been carrying out works for reinforcement
for earthquake resistance 56 based on this plan.
It was decided that for subways, part of expenses required for works to
reinforce earthquake resistance of center pillars of tunnels of existing railway
structure be subsidized out of the second supplementary budget for fiscal 1995.
(3) Security of safety for trains at the time of occurrence of earth-quake
Urgent Earthquake Detection and Alarm System (UrEDAS) was developed by the
Railway Technical Research Institute (Picture.
5). This is the first intelligent system in the world, in which the location
of occurrence of an earthquake and its scale is automatically detected at the
stage of its preliminary tremor (P-wave) and an alarm is issued regarding the
operation of trains within 4 seconds after the detection. This system has already
been introduced to the Sei Kan Tunnel, Honshu-Shikoku Bridge and Tokaido Shinkansen
line. It has been adopted in some parts of Sanyo Shinkansen line from 1995.
The construction of a new intelligent system in which the above system is combined
with another system called HERAS which enables to make precise decision on the
resumption of operation of trains after an earthquake and automatically predict
any places which would be damaged by the earthquake has been/developed.
(1) Studies on the earthquake resistance of port facilities
The Port and Harbor Technology Institute and others have carried out various
researches and experiments and analysis of damages caused by earthquakes in
order to design port facilities to make them earthquake-resistant structures
and engaged in collection of records of dynamics of earthquake which cause damage
and understanding the mechanism of causing damages to structures. The results
of these works have been reflected on actual practices in the form of the improvement
of the seismic coefficient method in the earthquake engineering.
In addition, the "The study on seismic stability of water front facilities
in the event of an Urban Areas against extremely large earthquake " has been
conducted as a 4-year project from fiscal 1993 to 1996 with main themes on grasp
of characteristics of directly-under-city earthquake, elucidation of dynamic
movements of structures and ground, improvement of earthquake-resistant design
for facilities at port and harbor shores.
On the basis of understanding the situation in which many port facilities
were damaged in the Hanshin-Awaji Great Earthquake Disaster, and in order to
promote urgently the study on earthquake-resistance technology against the large-scale
directly-under-city earthquake which has three-dimensional dynamics of movements,
the large-size under-water shaking table at the Port and Harbor Technology Institute
is improved to vibrate three-dimensionally out of the second supplementary budget
fcr fiscal 1995.
(2) Measures against the liquefaction In the Niigata Earthquake which took
place in 1964, the damage to structures of public works caused by liquefaction
became a big social problem. Since that time, various research and development
works on liquefaction have been widely carried out (Picture.
6).
At present, comparison method and replacement method have been adopted as
measures against the liquefaction of the background for the port structure which
is newly constructed.
(3) Improvement and reinforcement of earthquake-resistant facilities
In order to analyze the mechanism of damages to the port facilities in the
Hanshin-Awaji Great Earthquake Disaster and examine how the future earthquake-resistance
standard should be, the Ministry of Transport established on January 28 "Technical
Committee for Earthquake-proof design of Port Facilities". On April 25, in order
to engage not only in works for the reinforcement of the earthquake resistance
for individual port facilities but also in the countermeasure against any earthquake
by a port as a whole, "The Investigation committee on the measures for quake-proof
port system ". These committees issued respectively their interim and final
reports on August 29.
On receipt of these reports on the same day, the Ministry of Transport drew
up the "The measures for a quake-proof port system". In this, it is proposed
as the measures for improvement and reinforcement of earthquake-resistant design
:(i) for the earthquake resistance design of reinforced quay-walls against the
earthquake, the directly-under-city earthquake is to be added as the subject
earthquake for designing ; (ii) for the design of earthquake resistance of the
quay-wall and others, the earthquake resistance standards should be strictly
adhered to for important facilities ; and (iii) for the design of the base for
bridge piers at the water's edge of the traffic facilities at port areas such
as elevated roads, etc., it is intended to secure the earthquake resistance
of those facilities taking into consideration the movements and structure of
the front shore protection.
It has also been decided that further promotion of improvement be made for
the reinforced earthquake-resistant quay-walls which have proved to be effective
in the earthquake disaster. In addition to the improvement and reinforcement
measures for the existing general quay-walls which would be used for transport
of emergency goods, the object of the improvement and reinforcement has been
extended newly to the container terminal buildings located at the three major
harbors and the domestic terminals that can meet the international transportation.
It was also decided that the improvement and reinforcement be made for multi-purpose
wharfs used for foreign trade.
It was decided that the inspection and reinforcement for the earth-quake
resistance be made in succession for other important facilities such as elevated
dock roads at port areas in accordance with the degree of importance and urgency
of each facility. It has also been decided to promote research and development
to increase the earthquake resistance of port facilities.
(4) Improvement of Coastal protection facilities Based on the experience
of the earthquake disaster of this time, out of the first and second supplementary
budgets for fiscal 1995, the functions for prevention of disaster of facilities
for maintenance of coasts such as the reinforcement of earthquake resistance
and measures against liquefaction for dikes, etc. at Tokyo or Osaka Port have
been strengthened for the purpose of protection of rear areas at the time of
earthquake.
(1) Situation of damages to airports in the past
The impediment to operation of aircraft was caused by the earth-quake damage
to airports only twice in Japan in the past, i.e., at Niigata Airport at the
time of the Niigata Earthquake of June 16, 1964 and Okusiri Airport at the time
of the Southwestern off Hokkaido Earth-quake of July. 12, 1993.
At the Hanshin-Awaji Great Earthquake Disaster, while Osaka International
Airport is relatively close to the seismic center and stricken areas, there
were damages only to part of the terminal building and no such damages as to
cause impediment to the operation of aircraft occurred.
(2) Improvement of the earthquake resistance of facilities
The paved structure such as the runway is resistant against the earthquake
and no special consideration of the concept of earthquake is made for the design
for the pavement. However, in consideration of the graveness and seriousness
of various damages caused by the Southern Hyogo Prefecture Earthquake, "The
Committee for Improving Seismic Safety of Airport and Air Traffic service Facilities"
was established on January 28 and examinations on the ideal future feature of
the earthquake resistance of airports and aeronautical navigation aids have
been developed and an interim report was issued on August 25. In the report,
it is recommended that further improvement of the earthquake resistance of airport
and aeronautical navigation aids would be desirable for the purpose of maintaining
the safety service of aircraft at the time of earthquake disaster and contributing
to the rehabilitation and reconstruction of the stricken area utilizing the
airport as the base for emergency or substitute transport. As the urgent matters
to wrestle with, the report listed the reinforcement of earthquake resistance
of the existing facilities such as civil engineered and construction facilities.
On receipt of the report, the Ministry of Transport has decided to carry
out, as pressing measures, the reinforcement of civil engineered facilities
and reinforcement or reconstruction of buildings constructed in accordance with
old specifications. Out of the second supplementary budget for fiscal 1995,
buildings of the Tokyo and Sapporo air traffic control center have been in the
process of works for the reinforcement of earthquake resistance. At the same
time, at regional key point airports such as Fukuoka Airport, improvements of
the earthquake resistance for the aprons and runways have been carried out and
the renewal of radio apparatus is made in preparation for any earthquake disaster.
(3) Security of functions of air traffic control
The air traffic control establishes the safety distance among air-crafts
in flight and between an aircraft and any obstacles and maintains and promotes
orderly air traffic. Loss of the air traffic control greatly impairs the safety
in the air traffic. For this reason, out of the first and second supplementary
budgets for fiscal 1995, the strengthening has been carried out for each air
traffic control center and the backup system for the facilities of international
air-ground communication which have been established for the air traffic control
over the ocean in Japan's charge.
In addition, a backup system using satellites for the ground communication
circuits connecting each air traffic control center, and connecting each air
traffic control center with airports, aeronautical navigation aids, etc. has
been discussed.
|
|
|