Geology Reference
In-Depth Information
Figure 6.26
Retaining
structures and catch
nets to stop natural
terrain landslides
impacting new
road, Lantau
Island, Hong Kong.
provide the earliest viable mitigation approach, without requiring
access to the slope.
Catch nets or fences can be positioned on-slope or in the toe zone of
the slope, depending on energy requirements and site restrictions. An
example is shown in
Figure 6.26.
Where energies computed from
rockfall analyses are too high for toe zone protection alone to maintain
risk levels below prescribed criteria for highway or rail users, on-slope
energy protection fences become a necessity to reduce total energy
impact at road level. Where the road (or railway) passes under areas
prone to continuous rockfall, an avalanche shelter is commonly used
(
Figure 6.27
).
6.6.5.3 Mesh
Wire mesh is commonly used to restrict ravelling-type rock failure and
can be
fixed at many anchorage points or can simply hang down the
fixed with anchors at the top and weighted with scaffold bars
or similar at the toe. Mesh (varying from chain-link, triple twist,
hex-mesh to ring-net, in increasing order of energy capacity) can be
placed by a variety of techniques, ranging from climber-controlled
unrolling of the mesh to the use of helicopters.
face,
Deep drainage can be very effective in preventing the development of
adverse water pressures, and this is often a combination of surface
protection and channelling of water away from the slope and inclined
drains drilled into the slope. Regular patterns of long horizontal drain
