In the Geotechnical and Structural Department, we are studying the integration
of ground and structures. There are three main research fields: economical
constructions and maintenance of port and airport facilities, improvement
of disaster prevention for port and airport facilities, and environment
conservation and effective utilization of natural resources. Research is
done with large testing facilities including an underwater shaking table,
large scale testing facility for structures, geotechnical centrifuge, and
other testing facilities.
| Economical construction and maintenance of port and airport facilities |
Most of port and airport facilities are on very soft ground and are exposed
to waves, earthquakes and the corrosive effect of seawater. There is ongoing
research into economical constructions and maintenance techniques.
| Iimprovement of disaster prevention for port and airport facilities |
Building port facilities strong enough to withstand a large earthquake
is necessary to enable the transportation of materials just after a major
earthquake. We are studying the reaction of structures during a big earthquake
as well as the mechanism of and countermeasures for liquefaction. A network
for observing strong-motion is in place.
| Eenvironmental conservation and effective utilization of natural resources |
There are many plans to construct waste landfills in port areas. Hence,
we are studying the safety management and the appropriate utilization of
waste landfills. It is important to be able to decrease consumption of
natural resources through the effective use of by-products. Therefore,
we are developing techniques to recycle by-products effectively.
The problem of soft ground has always been the major obstacle to the
construction of ports and airports in coastal areas. The construction of
the Kansai International Airport (KIA) is a good example of this problem.
The total overburden weight of the large-scale reclamation above the seabed
has an extensive effect from the Holocene clay layers to the Pleistocene
clays. The investigation into the strength characteristics and the settlement
estimation for the Pleistocene clays has been a significant technical problem.
Recent research including various laboratory tests and analyses on the
Pleistocene clays, sampled by the latest boring technique to a ground depth
of 100 to 400 meters, have begun to reveal the unique characteristics of
this area. The results of these research activities have provided fundamental
support for the design and construction management of KIA's second project
phase.
The photo shows a microscopic view of the clay from the seabed near Japan. Two diatom cells can be seen in the centre of the photo. They can affect the high compressibility of the clay layer.
|
 |
| "High Capacity Separated-type Consolidometer for the investigation
on consolidation characteristics of the Osaka Pleistocene clays" |
| Integrating design methods of ground-structure system |
For accurately evaluating various functions of port facilities such as
safety and serviceability, it is necessary to carefully consider the interaction
between structures and the ground. The effect of these interactions on
structural performance needs to be revealed by conducting various experiments
and numerical analyses. With regard to the safety of structures against
complete collapse, the variation of external forces is also taken into
account, and the probability of collapse is calculated based on reliability-based
design criteria. This investigation seeks to find a method to properly
determine the design safety factors of structures.
Figure 2 Reversed cyclic loading test on a scaled model of piled pier |
| Floating offshore structures |
In Japan, floating structures such as floating oil storage systems, floating
bridges, offshore pavilions, floating piers, and floating breakwaters have
been constructed. Floating structures are superior to fixed structures
in earthquake resistance, but then they subject to the movement of the
waves and wind. In the design of floating structures, it is therefore necessary
to predict motion and mooring forces on them during normal and stormy weather.
A numerical simulation method has been developed for this purpose in our
study. The method has been validated and fine-tuned by hydraulic model
experiments and field observations, and it has been used for the design
of various kinds of floating structures.
Floating Oil Storage System (Shirashima, Fukuoka Prefecture) |
| Construction of Airport Facilities and their Effective Maintenance &
Management |
Recently, many airports, such as Kansai International Airport and Central
Japan International Airport, are being constructed in Japan. Many of these
construction projects are carried out under severe conditions due to environmental
issues, and there are many technical problems yet to be solved. In order
to establish the safety and durability of the civil engineering facilities
for airports, assessment and maintenance methods are important problems
to be tackled.
In the case of investigation of structural conditions for airport pavements
in service, work must be carried out quickly to avoid closure of the airport
or damage to pavements. For that purpose, a Falling Weight Deflectometer
(FWD) apparatus is utilized to investigate the response of pavement to
impact strength.
Falling Weight Deflectometer (FWD) |
|