Earthquakes can devastate communities killing people
by destroying houses, schools, office buildings, hospitals,
bridges, and other essential structures. One of the
major causes of failure of a structure is liquefaction
of soils leading to failure of the ground and building
foundations. During an earthquake, water pressure
in a loose sand deposit may suddenly increase causing
loss of shearing resistance and the ability of the
sand to carry the loads from a building foundation.
The objective of this research is to prevent the occurrence
of liquefaction by introducing air or gas bubbles
in the saturated sand, with the expectation that the
presence of such bubbles will prevent the build up
of water pressure and hence liquefaction failure.
This research aims at demonstrating the technical
feasibility of using entrapped air in sands as a means
of mitigating the potential damages from liquefaction
during an earthquake. The research consists of experimental
and analytical studies.
A large size liquefaction box was designed and manufactured
for testing sands under earthquake motions. The shaking
table facility at Northeastern University will be
utilized to subject various sand specimen prepared
in the liquefaction box to earthquake shaking. Different
techniques will be employed to entrap gasses in the
sand specimen and the effect of the presence of the
gases on the liquefaction potential of the sands will
be investigated. In order to explore this effect,
advanced instruments and data acquisition system will
be assembled to permit measurement of some physical
characteristics of the sand specimen prepared, ground
motions and water pressures built-up in the specimen.
An important part of the research explores measuring
some physical characteristics (degree of saturation
and shear modulus) of the sand specimen using pieozoceramic
elements and disks which create and receive elastic
waves through the sand. By using information on how
the waves are changed through the sand, physical characteristics
of the specimen prepared are examined. These measurements
will allow the researchers to establish theoretical
correlations between the liquefaction resistance of
the sand and physical characteristics of the specimen
at different earthquake magnitudes. |
