邊坡破壞引發土石流之機制研究（一）─總計畫暨子計畫：邊坡破壞引發土石流之機制研究—以土石流源頭為對象
Date Issued
2002
Date
2002
Author(s)
DOI
902625Z002023
Abstract
The initiation of debris flows is very
much affected by soil properties. The study
site is at the upstream of Shanher Creek,
located at Chinshan in Taipei County.
Samples were taken from the site and their
grain size distributions were determined.
However, due to limitation of specimen size
in the laboratory, simulating the field grain
size distribution by the “weight replace
method” was adopted. Tests were carried out
on the simulated samples to obtain the
mechanical properties of the soil as well as
hydraulic properties. The tests performed
include isotropically consolidated undrained
triaxial (CIU) test, triaxial permeability test,
soil-water characteristic curve, and
consolidated drained triaxial (CD) test on
unsaturated soil sample.
According to the grain size distribution
of the soil, it contains 77.1% gravels and only
5% fines. It is composed mainly of coarse
materials with non-plastic fines and is
2
classified as GP by the Unified Soil
Classification System. Because of coarse
particles, the soil has low water retention
ability as determined by the soil-water
characteristic curve test. The permeability
test shows that the permeability of the soil
decreases with increasing confining pressure,
but the difference is not significant. The CIU
test shows higher friction angles for the soils
with smaller maximum particle size. The CD
test on unsaturated samples shows that shear
strength increases with matric suction, but
levers off when the matric suction being over
75 kPa. The relationship between the shear
strength and the matric suction is nonlinear,
thus fb is not a constant.
Finally, based on the above soil
properties, heavy rainfall was very likely to
saturate quickly the surface zone of the slope
on site and caused the slope unstable or even
failed.
Subjects
slope failure
unsaturated soil
soil-water characteristic curve
shear strength
Publisher
臺北市：國立臺灣大學土木工程學系暨研究所
Type
report
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