摘要(英) |
For
concept of debris-flow hazards mitigation, 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.
However, the flexible steel 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 snow-slide
or debris flow. It is seldom seen that the flexible steel system
is used to block debris flow in Taiwan. Therefore, this research
will make a further study on the flexible retaining system is an
important issue in debris-flow hazards mitigation construction.
The flexible steel net was installed in the upstream of Shan Pu
Keng River, Shanan Village, Shueili Township, Nantou County.
After flexible steel net set up, there were some typhoons which
caused heavy rainfall leading to debris flows. The flexible
steel net blocked the debris flows individually. After that,
rocks and sediments filled in the flexible steel net. In this
research, the depositions of debris flows and situations of
block of flexible steel net, as well as compare with the results
of flume tests in Lab to discuss the situations of sediments,
grain deposition rate, volume concentration reduction rate,
sediments flow rate, change of spring and change of vibration
meter, etc.
From observation of field and flume tests in Lab, it can be
found that the slope of river bed become smooth and the impact
force of debris flows decreased make debris accumulate gradually
in upriver after flexible steel net is struck again and again by
debris flows. For the volume concentration reduction rate, the
results of flume tests in Lab shows that the volume
concentration for all cases after passing the net is reduced to
below 0.2. Volume concentration, 0.012, in the sediment is
better than in the higher the volume concentration, which means
that when debris flow is in the lower the volume concentration,
the power of flow is great and more debris can pass flexible
steel net. The analytic results of spring elongation and
vibration meter illustrate that flexible steel net form function
of rock gabion after flexible steel net block debris. Due to the
retaining structure produced, which can effectively decrease
impact force of the next debris flow. Through the results of
field observation and flume tests in Lab, they can be known that
flexible steel net can effectively decrease the volume
concentration of debris flow, the amount of flow of debris flow,
the impact force and the destructive force, to reach the
destination of debris-flow hazards mitigation.
Key Word: Debris Flow, Debris-Flow Hazards Mitigation, Flexible
Steel Net |