| Summary: | 碩士 === 國立雲林科技大學 === 營建工程系 === 102 === If the strength of the gravel layer is not good enough, grouting will be performed every
2-3 meters deep to prevent collapses during the gravel excavations. Therefore, a discrete
element program PFC2D (Itasca 2004) was employed to model the gravel layer on site
and, according to the geological survey of certain areas in the western Taichung City, to
simulate staged excavations.
This research was aimed to control the material parameters of parallel-bond models of
the grouting effect at the simulated excavation sites. With such simulation, we expected
a series of parameter analyses to obtain safe and cost-efficient design principles of
excavation as reference. If the excavation sites not given bond model to simulate the
grouting, the excavation sites will be fully collapse. Cross validation of parameter
analysis showed that, firstly, the parallel-bond shear stiffness (Pb_ks) had more
influence on the horizontal displacements of excavated wall than the parallel-bond
normal stiffness (Pb_kn). Secondly, the 50cm granular-bond thickness of simulated
grouting effect on the excavation sites was better than 30cm one. The maximum
horizontal displacement variation of the 50cm granular-bond thickness in the three
stages were 43%, 55% and 58% respectively, compared with the 30cm granular-bond
thickness.The maximum horizontal displacements occurred between 0 and 0.75 meters
deep, and tended to increase while approaching the surface. There were heave at the
bottom of excavation in the first two stages, while, without squeezing downward, the
3rd stage excavation had a less rugged bottom despite its wider settlement on the
ground surface.
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