2510109542

Fig. 7 "Steel Pipę Roof" method to construct a subway station (courtesy of Hazama Construction Co.)

Fig. 8 Sunken tunnel in Tokyo Bay (courtesy of Taisei Construction Co.)

A l Y A 2 Y A 3 Y A 4 Y A 5 Y

%

%

The bending moments obtained from these

measurements were compared with those pre-

dicted on the basis of the theoretical ana-

lysis. In Fig. 10, the solid linę indicates    A 7 Y

the bending moments calculated from the

theory and circles show those obtained from

the measured results. Reductions of the

bending moment at the joints between the

boxes indicate the effectiveness of the flex-

ible joints.    A l X

As a source of cleaner energy, LNG is becoming increasingly important in our cities. LNG is stored underground, and around an underground LNG storage tank, continuous walls are built. Because the temperaturę of LNG is about 50 degrees below zero in centigrade, the soil around it is permanently frożen.

One of the best known methods to strengthen weak foundations here is sand compaction piles. Also, loose sand is densified by the same method. Fig. 11 shows the installation by means of a special mandrel consisting of a Steel pipę with the bottom end closed and with a vibrator attached on its top. After the mandrel penetrates the weak foundation to the reąuired depth, sand is poured through the mandrel as its bottom is opened. As the mandrel is withdrawn, the sand is ejected and compacted by vibration, forming a compacted sand pile in the ground. It is possible to install sand piles with the maximum diameter of 2 meters to the maximum depth of 40 meters. These monstrous sand compaction piles are driven from large barges to stabilize soft sea bed foundations.

A 2 X A 3 X

A 4 X

A 5 X A 6 X A 7 X

Fig. 9 Records of accelerations measured during an earthquake (courtesy of Taisei Construction Co.)

Notę : X and Y indicate horizontal and vertical components, respectively.

See Fig. 8 for the locations of the seismographs Al through A7.

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