| Summary: | 碩士 === 國立臺灣科技大學 === 營建工程技術學系 === 83 === Applicability of the excavated soft rock for the construction
of the downstream shell of Nanhua earth dam is studied
considering laboratory test results and its in-situ engineering
behavior. Study shows that the differences between the basic
properties of the excavated soft rock and the gravelly soil
are quite obvious. The excavated soft rock will slake when
soaked with water, but the gravelly soil will not. Because
mica, which is the major mineral composition the excavated
soil, becomes lubricative when meet with water. On the other
hand, the gravelly soil is mostly consisted of Quartz. From
the compaction tests, the compaction characteristics of the
excavated soft rock is even better than that of the gravelly
soil. Both the excavated soft rock and the gravelly soils show
almost equal shear strength according to the large-scale
triaxial tests. The in-situ engineering behavior is studied by
the field compaction test, STABR and FEADAM 84 analysis. The
results show that field dry density and permeability vary
widely because fine-grain of the excavated soil may aggregate
when mixed water. So, the upper bound of the water content at
compaction designated in the construction criteria is suggested
to be reduced by 3%. In addition, throuth mixing is required to
prevent material separatation. In reality, slaking is not
expected to occure because the excavated soil is used in the
downstream shell and is protected by the dam core and filter.
According to the results of STABR analyses, slope stability
meets the design requirement. Deformation calculated using
FEADAM 84 comparies reasionably with the measured deformation
of the downstream shell, which is relatively small. Judging
from the result of the laboratory tests and the in-situ
engineering behavior, the excavated soft rock is a suitable
material for downstream shell construction of an earth dam.
However, its suitability for upstream shell and dam core
construction needs further study.
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