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The Kagoshima Airport was constructed on the Shirasu soil. An embankment, 40 meters in height, consisted of alternating layers of Shirasu and loam, on which a runway, 2,500 meters long and 45 meters wide, was safely constructed. The total earthwork reąuired amounted to 3.5 million cubic meters.

For reclaiming land for Coastal industrial areas, large-scale filling or reclaiming operations have been in progress. During reclamation for the Ohgishima Industrial Complex in Tokyo Bay, the fili materials were transported across the bay from the borrow area located some 40 kilometers away. Soils were excavated by 30-ton scrapers, transported by large belt-conveyors to the coast and then ferried by barges across Tokyo Bay.

A total of some 80 million cubic meters of soil was moved to reclaim the area, 5.15 million sąuare meters.

In order to minimize the negative skin fric-tion, Steel pipę piles coated with asphalt have been used in the reclaimed area. Such piles used in Ohgishima totalled several hundreds of thousands of tons.

In the Asian Continent, the art of dam build-ing was fairly well advanced even in the ancient periods. This art was brought to Japan about 1500 years ago. Survey techniques and mathematics were developed to build dams. It has long been known that compaction of soils increases their strength and makes them morę impervious. It was also known that the volume of the soil excavated from the borrow pit during transportation was about 1.25 times that of the in-place natural soil, and after compaction, it was reduced to 0.75 times the original volume.

One of the oldest and the most famous ones is Manno Pond in the Island of Shikoku, built first around the early eighth century. Early in the ninth century it failed, but was re-built by the famous Buddhist Kukai-Shonin. After that it has repeated failures and re-constructions a number of times. This dam speaks very eloquently of all the troubles our ancestors have had for improving the art of dam building. In 1854, this dam again failed due to an earthquake.

Some 1,800 dams have been built for agri-cultural use in this country sińce about the first century. In 1976 alone, over 200 irri-gation dams were under construction; the numbers of earth dams and rockfill dams are about the same totalling approximately 80% of those under construction. Most of the earth dams are less than 40 meters in height, but some rockfill dams are higher than 100 meters. In the next ten years, it is expect-ed that 4 billion cubic meters of water will be required mainly for irrigation purposes, and many large dams will have to be built to provide new water resources, most of them under difficult conditions. It will cali for many high rockfill dams, which in turn will promote the rapid advancement of the tech-nology involved, geotechnical engineering for dam construction in particular.

Of the river dikes, the most famous is the Manda Dike for Yodo River in Osaka, built in the fifth century. Soils were compacted by wooden poles and human steps. It is said that the famous warrior-general, Takeda Shingen, in the sixteenth century took advan-tage of his people carrying portable shrines to celebrate festivals in order to compact the embankment by letting them dance on the road on the dike.

Most of the rivers in Japan are protected by levees and dikes to cope with smali to medium floods. In the typhoon season every year, however, failures take place. To strengthen levees and dikes is one of our urgent research subjects.

Many hydropower dams are built lately with pumped storage arrangements. Among the rockfill dams under construction, the highest is Takase Dam of the Tokyo Electric Power Company. It is 176 meters high and its volume 11.4 million cubic meters.

Earthquakes are most feared in regard to the stability of dams, and various studies have been madę to improve the stability when sub-jected to strong earthquakes. In the embankment of Kisenyama Dam of the Kansai Electric Power Company, seismograms were installed.

For the first time, field dynamie experiments were conducted there using large vibrators. Subsequently some observational data were obtained during earthquakes and an extensive analysis performed on the basis of various assumptions. It has been found as a result of these studies that the natural frequencies and the modę of vibrations do not change regardless of the magnitude of the accelera-tions.

The proposed bridges connecting the Main Island of Honshu and the Island of Shikoku are one of the largest civil engineering pro-jects in this country. Most of the site investigations have been completed, and some construction works have already commenced.

In connection with the foundations, however, large scalę experiments, field studies and theoretical researches are still being performed. In terms of soil mechanics and foundation engineering, the bearing capacity of the foundations and the stability against earthquakes are particularly important. Many difficulties are anticipated with construction because the foundations will have to be placed under the sea. The largest piąte loading test conducted so far employed a piąte, 3 meters in diameter, but it did not reach failure.

Last year three load tests were conducted using a piąte, 2 meters in diameter, and they were loaded to failure. These tests and researches are useful not only for building these particular bridges but for designing and building other bridges and structures.

The bridges connecting Honshu and Shikoku will be supported mainly by caisson- foundations, but a new type of foundations called the multi-column foundations have been proposed. These foundations were in fact used for Ohshima Bridge in the Inland Sea. Fig.

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