地震造成新山崩地質環境特性之研究─地震後新山崩之工程地質特性（Ⅰ）

The 99 peaks of the Nantou area is
comprised of the gravel formation of
Pleistocene. During the Chi-Chi Earthquake,
there were lots of landslides in the area. Lots
of former study indicate that the difference of
the shape, size, proportion and orientation of
the gravels make the properties of the gravel
material change. The major point of this
study is to comprehend the relationship
between the slope grade and the orientation
and shape. The distribution of the gravel
particles in the matrix is 85% and sand
particle is 14% of the matrix in the study area.
The soil classification was poorly-graded
gravel (GP) according to the Unified Soil
Classification System. The liquid limit of the
matrix is 26%, plastic limit is 15% and the
specific gravity of the matrix is 2.52. The
strength of the matrix ranges from 100 to 250
kg/cm 2 . The mineral of the matrix includes
quartz, kaolinite, illite and smectite. The dry
unit weight of the gravel particles in the
study area is 2.56 kg/cm 3 and water-absorptivity
is 1.14%. Slake durability index
(Id2) is 98.6 which shows the ability against
weathering of the gravels is good.
The large scale disaster of dip slope
failure had occurred in the Juo- Feng- Err-Shan
of Nantou area during 921 earthquake,
and generated a length 2100m and wide
1000m relict slip surface. And this study try
to use laboratory experiments to understand
the engineering properties of rock materials on the slip surface. The engineering
properties include 4 items: (1) physical
properties, (2) rock textures, (3) mineral
composition, and (4) mechanical properties.
The physical properties includes 4 items:
(1)water content, (2) porosity, (3)unit weight,
and (4) liquid and plastic limit. The study
discusses the relationship between these
physical properties and slake durability
properties, point-load strength and the basic
friction angle. The results demonstrate that
the point-load strength will decrease with the
water content increase, and the other physical
properties seem no relationship with
mechanical properties.