Civil Engineering Reference
In-Depth Information
FIGURE 3.19
Sand boil in Niigata caused by liquefaction during the Niigata (Japan) earthquake of June
16, 1964. (
Photograph from the Steinbrugge Collection, EERC, University of California, Berkeley.
)
3.4.2
Settlement and Bearing Capacity Failures
When liquefaction occurs, the soil can become a liquid, and thus the shear strength of the
soil can be decreased to essentially zero. Without any shear strength, the liquefied soil will
be unable to support the foundations for buildings and bridges. For near surface liquefac-
tion, buried tanks will float to the surface and buildings will sink or fall over.
Some of the most spectacular examples of settlement and bearing capacity failures due
to liquefaction occurred during the Niigata earthquake in 1964. The Niigata earthquake of
June 16, 1964, had a magnitude of 7.5 and caused severe damage to many structures in
Niigata. The destruction was observed to be largely limited to buildings that were founded
on top of loose, saturated soil deposits. Even though numerous houses were totally
destroyed, only 28 lives were lost (Johansson 2000).
Concerning the 1964 Niigata earthquake, the National Information Service for
Earthquake Engineering (2000) states:
The Niigata Earthquake resulted in dramatic damage due to liquefaction of the sand
deposits in the low-lying areas of Niigata City. In and around this city, the soils consist of
recently reclaimed land and young sedimentary deposits having low density and shallow
ground water table. At the time of this earthquake, there were approximately 1500 reinforced
concrete buildings in Niigata City. About 310 of these buildings were damaged, of which
approximately 200 settled or tilted rigidly without appreciable damage to the superstructure. It
should be noted that the damaged concrete buildings were built on very shallow foundations or
friction piles in loose soil. Similar concrete buildings founded on piles bearing on firm strata at
a depth of 20 meters [66 ft] did not suffer damage.
Civil engineering structures, which were damaged by the Niigata Earthquake, included port
and harbor facilities, water supply systems, railroads, roads, bridges, airport, power facilities,
and agricultural facilities. The main reason for these failures was ground failure, particularly
