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13 shows the cross section of one of the pierś, P-4, consisting of 9 Steel pipę piles, each 3.5 meters in diameter and 36 meters in length. Because the excavation is to be madę at the sea bottom, under-water blasting will be necessary. For this purpose, an experi-mental under-water blasting was conducted which included such items as the effects upon fish resources.

6.50C

Fig. 13 Multi-column foundation for

Ohshima Bridge (P-4)

(courtesy of Taisei Construction Co.)

Since most of the major ports and harbors are situated on soft alluvial soils and have experienced damages due to earthquakes includ-ing the Kanto earthquake, our research efforts have been focussed on the aseismic design for breakwaters and pierś. Among the recently constructed ports which specialize in handling Petroleum, Kiire in Kyushu has one of the largest sea berths in this country. It accom-modates an oil tanker as large as 500,000 tons and is supported by Steel pipę piles ranging from 900 to 2,300 millimeters in diameter and weighing about 12,000 tons in total.

For the first time in the world the Nagasaki airport was built entirely in the sea; an island was cut and the sea reclaimed. Since the sea bed included soft compressible materials, large scalę pre-loads were placed to stabilize the foundations. Thus the airport, 156 hectares, was constructed with about 20 million cubic meters of earthwork successfully completed.

were instability and excessive settlements of embankments on soft ground, difficult earthwork involving volcanic ash soils such as Kanto loam and Shirasu, frequent landslides in the mountamous regions and problems related to the base course and subgrade for the pavement. Numerous field studies were conducted including full-scale experiments and long-term observations of the completed works. In urban areas, many elevated express-ways were constructed. Construction of grade separation works for railroads and highways are difficult because the traffic has to be maintained during construction.

There are many landslides moving at very slow rates in natural slopes or cuts in this country. The remedial measures commonly employed here to arrest such movements in-clude excavation, drainage, installation of piles and wells, and combinations of these. Bending moments developed in piles as cal-culated and measured are being reviewed for establishing a morę rational design method.

Including liquefaction of sand during earth-quakes, consolidation and shear character-istics of clays and characteristics of com-pacted soils, the results of our fundamental research on soil mechanics and foundation engineering will be reported during the con-ference.

I have very briefly introduced the history and the current State of geotechnical engineering in Japan with some examples of works completed and under construction. Methods or machines used in some instances were imported from other countries. Because of Japan's unique geology, topography, climate, culture and land use, many of the imported machines and knowhows had to be modified so as to suit our local requirements.

The same is true for our knowledge of soil mechanics and foundation engineering. Our land is mostly mountainous, the geology is complex, and there are many faults and joints in the bedrock. Even on the plains, thick deposits of extremely soft soils often prevail, and there are volcanic ashes difficult to deal with. In addition, we have frequent earthquakes, typhoons and landslides .

It is hoped that on this occasion of the Ninth International Conference on Soil Mechanics and Foundation Engineering, the participants from abroad will visit personal-ly with the Japanese participants so that we may benefit from your views and observations. We do invite you to see some of our completed works and construction sites.

Construction of many new roads and highways started just about the time when the first Shinkansen was under construction. Major geotechnical engineering problems encountered

I acknowledge with thanks the contributions of many people who have madę available slides and other data for this lecture. Thank you very much for your kind attention.

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