| Summary: | 碩士 === 國立中央大學 === 土木工程學系 === 86 === To improve the bearing capacity of soft soils, preloading is the
one of most preferable methods. Since most soft soils have very
low permeability, dissipation of excess pore water pressure
during preloading takes time. Therefore, sand-drain-piles and
prefabricated vertical drainage (PVD) methods have been
developed to accelerate consolidation process. Essentially,
these methods shorten the length of drainage paths from the
thickness of clay layers to the spacing of drain wells.The
research of the consolidation behavior accelerated by PVD on
soft clay divides into three parts: I, The settlement analysis
of stratum driven by PVD; II, To study the properties of stratum
consolidation after PVD constructed; III, Indoor pit test.
According to the results of laboratory experiments, the
settlement of soil layers is influenced by the discharge
capacity of PVD. Smearing, well resistance, filter blinding, and
clogging are the factors influencing the function of PVD, which
decrease the permeability of soils and the discharge capacity of
PVD. The factors should have to be taken into account in the
future.Finally, the results of indoor pit test which includes
two zones－ improved zone and untreated zone-reveal that, after
setting the load on the pit the settlement of the improved zone
is larger than the untreated zone, and the pore water pressure
and the earth pressure increase rapidly at the both zones. In
the next day, the pore water pressure and earth pressure in
improved zone decrease rapidly, but not in the untreated zone.
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