| dc.description.abstract | The objective of this research is to use small size pile (micro pile) to reduce settlement and
tilt of building in liquefiable soils. Dynamic centrifuge tests were used to simulate the
liquefaction mitigation and seismic behavior of a five-story building with footing supported by
micro-piles. The model ground is 20m thick, the shallow 5m is liquefied sand layer, and the
beneath is dense non-liquefied sand layer or mix layer. The diameter of the micro-piles is 33cm,
and the penetration depth into the non-liquefied soil layer is 2, 6 and 10 times of the micro-pile
diameter, to explore the influence of the different relative density of non-liquefied sand layer,
mix layer and penetration depth. The weigth and footing dimension of the five-story building
are designed in accordance with the common sigle five-story RC department in Taiwan.
The results show that the domain frequency of the ground is 2.0 ~ 2.4Hz and the domain
frequency of building with micro-pile structure is 1.0 ~ 1.2Hz. The tests results show that the
dissipation of excess pore water pressure in the soil layer is from building to free field and from
deep to surface of the soil layer. The test results show that the micro-piles and increase the
penetration depth has the obvious effect of restraining the settlement and the inclination of the
building after the earthquake. During the vibration, it was observed that the axial-force
instrumented piles had symmetrical reverse axial force waveform, and the lateral instrumented
piles had similar and in phase bending moment wave forms. Because the settlement of the
building less than settlement of the soil layer, the negative friction force were accumulated on
the micro-pile. But after vibration, with the dissipation of the excess pore water pressure, the
negative friction on the micro-pile will recover and re-provide bearing capacity of the building.
When the shallow soil liquefies, axial force and moment increases in the deeper part of the
micro-piles, the shallow soil loses liquefaction and the load is transferred to the deep soil.
Key word: small size pile, dynamic centrifuge test, soil liquefaction, low-rese building | en_US |