| Summary: |
The Universitas Muhammadiyah Yogyakarta
(UMY) campus was constructed on 28 hectare which mostly
rested on a sand deposit. The ground water table was
shallow. Theoretically, the site was susceptible to liquefaction
during ground-shaking. During earthquake on May 27, 2006,
a magnitude 6.3 shocked the provinces of Yogyakarta,
among those number of seismic damages were reported. The
damages were identified because of liquefaction phenomena
during the ground vibration. Reconnaissance study after the
earthquake was found some sand boiling sites near the
Masjid and Library building. This paper presents a
liquefaction evaluation at those two building. The
liquefaction analysis based upon force equilibrium concept
can not be directly performed in this study, because there are
no accelerometers in the hazard areas in this earthquake.
Therefore, the accelerations back-calculated by liquefaction
analysis are recommended in this article. The analysis was
calculated using 475 cone penetration test (CPT) data that
collected from 18 testing sites. By using the CPT data and the
estimated cyclic stress ratio from Robertson & Campanella
(1985), the critical accelerations from 0.23 g to 0.93 g will
generate liquefactions in all depth, loose sand layers in
hazard areas. In addition, the accelerations from 0.23g to
0.54g will make 50% of top sand layer liquefied. In general,
the estimated ground acceleration of 0.36 g to 0.68 g was
sufficient to generate liquefaction at the observed hazard
area.
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