摘要(英) |
The
destructive power of debris flow comes from a large number of
soil & sediment and rapid movement & impulse. Traditionally, the
protective equipment, which is designed based on the rigid
retaining concept of concrete structures (such as debris barrier
or reinforced concrete gravity dam), costs large sums of money.
We must pay attentions to its structure safety especially. And
the flexible retaining system has been used in Europe and U.S.
for many years. In addition to the rock-fall disaster
prevention, it also can be used in such disaster as snowslide or
debris flow. It is seldom seen that the flexible retaining
system is used to block debris flow in domestic areas.
Therefore, this research will make a further study on the
flexible retaining system.
The retaining structure adopted by this research has both
functions of a permeably flexible energy dissipation structure
and a previous rock gabion dam. As it is not full of soils and
sediments in the retaining structure, then it is the function of
flexible energy dissipation structure. As it is full of soils
and sediments in the retaining structure, then it becomes the
function of rock gabion dam naturally. In coordination with the
Program to Upgrade Industrial Technology and Enhance Human
Resources of National Science Council, we set up an on-site
debris-flow retaining structure in the upstream of Shan Pu Keng
River, Shanan Village, Shueili Township, Nantou County to assess
the effect of such debris-flow retaining structure and to shrink
its size to move to the indoor for a test of debris-flow
tank. For the indoor debris-flow test, we adopt the equal-weight
replacement to simulate the on-site gradation and to measure the
average gradient of river bed. With different debris-flow
volumes & concentrations and under different maximum grain
sizes, we study the retaining effect and the force-endured
status with such analytic items as volume concentration
reduction rate (Rv), dam-passing rate (Rp), grain deposition
rate, vibration meter and displacement meter, etc.
For the volume concentration reduction rate, the result of
indoor tank test shows that the volume concentration for all
cases after passing the dam is reduced to below 03.As the
initial volume concentration is 0.45 and 0.55, the volume
concentration reduction rate is more than 80%.For the initial
volume concentration of 0.35, then the reduction rate is
60.3%.The dam-passing rate will be reduced as increasing the
volume concentration, which is less than 40% before the dam
reaches the full level. The higher the volume concentration is,
then the better the grain deposition rate is. As the volume
concentration is 0.65, the grain deposition rate can reach
98.88%. And as the volume concentration is 0.35, the grain
deposition rate will be down to 60%. Under the strike of
debris-flow again and again, we use the displacement meter and
the vibration meter to measure the impact fore of sediments in
the auxiliary dam and in front of the dam and the acceleration
of sediments in the dam and find that they are significantly
reduced. Therefore, through the test, we can find that we can
truly make use of the characteristics of a retaining structure
to retain & deposit the debris flow. |