U.S. patent application number 10/800798 was filed with the patent office on 2005-09-22 for revolutionary barrier for rockfall or the like: maintenance-free, highly efficient in dissipating kinetic energy, and fast in installation.
Invention is credited to Pan, Yucheng.
Application Number | 20050205853 10/800798 |
Document ID | / |
Family ID | 34985287 |
Filed Date | 2005-09-22 |
United States Patent
Application |
20050205853 |
Kind Code |
A1 |
Pan, Yucheng |
September 22, 2005 |
Revolutionary barrier for rockfall or the like: maintenance-free,
highly efficient in dissipating kinetic energy, and fast in
installation
Abstract
A safety net system called Pan-barrier is invented to stop
rockfall, debris flows, or the like, with three striking
advantages: completely maintenance-free, highly efficient in
dissipating and diverting kinetic energy, and very fast in
installation. The Pan-barrier uses a new type of cable braking--the
weight braking--that can be engaged repeatedly without limits or
maintenance. The Pan-barrier consists of: 1) a sheet formed by one
looped peripheral cable with mesh or net panels attached; 2) two or
more anchors holding one side of the sheet close to the ground; and
3) two or more supporting cables (tiebacks), each tied to a ground
anchor, erected by a post, and equipped with the weight braking
system, holding the top side of the sheet at a designed height, so
that the sheet is oblique to the ground. Impact objects are stopped
inside the wedge formed between the oblique sheet and the
ground.
Inventors: |
Pan, Yucheng; (Honolulu,
HI) |
Correspondence
Address: |
Yucheng Pan
Ste. 500
841 Bishop St.
Honolulu
HI
96813
US
|
Family ID: |
34985287 |
Appl. No.: |
10/800798 |
Filed: |
March 16, 2004 |
Current U.S.
Class: |
256/12.5 |
Current CPC
Class: |
E01F 7/045 20130101 |
Class at
Publication: |
256/012.5 |
International
Class: |
E01F 007/02 |
Claims
What I claim as my invention is:
1. A safety net system for restraining rockfall, debris flows, or
the like by means of a continuous barrier sheet formed by flexible
mesh panels, cable nets, ring nets, or the like, wherein for said
safety net system said sheet is installed oblique to the ground or
slope over which said sheet is suspended, so that: a wedge-shaped
or the like shaped space is formed between said sheet and said
ground, with one closed side where said sheet and said ground meet;
rockfall, debris, or the like goes into said space through the open
side(s) of said space; impacts with debris or the like occur on the
underside or facing said ground side of said sheet within said
space; said space stores stopped objects and accumulated
debris.
2. A safety net system according to claim 1, wherein said sheet is
supported by or attached to a looped frame cable stretched to
rectangular shape or the like; the lower side of said frame cable
is held down close to said ground by means of anchors or the like
while the opposite side or the top side of said frame cable is held
up by means of posts, tiebacks, supporting cables, or the like.
3. A safety net system according to claim 2, wherein said tiebacks
are erected or supported by posts, natural topographic highs, or
the like and hold up said top side of said frame cable.
4. A safety net system according to claim 2, wherein a mesh screen
or the like drape is draped from said top side of said frame
cable.
5. A safety net system according to claim 2, wherein all the
connections to said frame cable permit sliding.
6. A safety net system according to claim 1, wherein objects,
usually heavy, are attached to or are hung from supporting cables
of said sheet for tensioning and braking of said sheet in case of
impacts.
7. A weight tensioning and braking system for safety nets, impact
fences, or the like, wherein said weight tensioning and braking
system comprises one or more weights, such as metals, concretes,
logs, rocks, or the like, attached or fixed to supporting or
tieback cables of impact fences or the like to create sagging of
said supporting or tieback cables for the purpose of tensioning or
braking, or both.
8. A weight tensioning and braking system according to claim 7,
wherein said supporting or tieback cables are supported by erecting
devices like posts and are connected to said weights and flexible
barrier sheet(s) at different or opposing sides of said erecting
devices;
9. A weight tensioning and braking system according to claim 8,
wherein said weights are connected to said supporting or tieback
cables by means of strings of different lengths, said strings range
from zero length (said weights fixed on said supporting or tieback
cables directly) to lengths that allow said weights lying on
ground.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001]
1 U.S. Patent Documents 4730810 March, 1988 Rambaud 256/12.5.
4819915 April, 1989 Cargnel 256/12.5. 5186438 February, 1993 Cross
and Smith 256/13.1. 5299781 April, 1994 Barrett Heam and 256/12.5.
McMullen 5535861 July, 1996 Young 188/280. 5961099 October, 1999
Thommen Jr. 256/12.5. 6027785 February, 2000 Yoshida 428/131
6131873 October, 2000 Blazon and 248/548. Bookwater 6592103 B2
July, 2003 Sennhauser 256/12.5. Foreign Patent Documents JP9310313
December, 1997 Kenkichi E01F7/04 EP0877122 November, 1998 Laurent
E01F7/04 JP2001064917 March, 2001 Katsuo E01F7/04 JP2002302911
October, 2002 Sakae, Mitsuyoshi, E01F7/04 Kazufumi JP2002047617
February, 2002 Eiichi E01F7/04
BACKGROUND OF THE INVENTION
[0002] 1. Field of the Invention
[0003] The present invention relates to a safety net system for
restraining rock falls or the like and to devices like cable
braking systems for absorbing high impact energy in a rockfall net
or the like.
[0004] 2. Description of the Related Art
[0005] A plethora of safety nets or impact fences have been devised
to absorb kinetic energy upon impact, like U.S. Pat. No. 6,592,103
B2 Sennhauser; U.S. Pat. No. 5,961,099 Thommen Jr.; U.S. Pat. No.
4,730,810 Rambaud; U.S. Pat. No. 5,186,438 Cross and Smith; JP Pat.
No. 2002047617 Eiichi; JP Pat. No. 2001064917 Katsuo; JP Pat. No.
2002302911 Sakae, Mitsuyoshi, Kazufumi; and EP Pat. No. 0,877,122
Laurent. These safety nets or impact fences are installed in an
upright position together with upright supporting posts, generally
closely spaced, with wire mesh, cable nets, or ring nets attached
to the top and bottom of the posts, usually through top and bottom
supporting cables. These safety nets or impact fences have serious
weaknesses as described below, with brief comparison with my
current invention, the Pan-barrier.
[0006] Segmentation. The numerous upright posts segment the
conventional nets or fences into segments, each confined within two
adjacent posts. In case of an impact, the impact energy is mainly
focused on one segment, greatly reducing the capability of the
system as a whole. It is well known that putting the nets down
slope side of the posts is more effective than putting them upslope
side of the posts because of segmentation: the posts segment the
nets more effectively for the upslope configuration during an
impact. The nets behave as springs during impact, with their spring
force F proportional to their amount of extension x, namely F=kx.
Without segmentation, the amount of extension x provided by the
whole system of cables and nets is large, providing a large force F
and a large stopping distance; with segmentation, the amount of
extension x provided by one segment of cables and nets is small,
providing a small force F and a short stopping distance. The ideal
barrier would be segmentation-free or post-free, which is my
current invention--the Pan-barrier.
[0007] Short stopping distance. Because both the top and bottom of
the conventional nets or fences are attached to the upright posts,
impact objects need to be stopped within a short distance created
by the bulging of the nets or fences during impacts. Short stopping
distance results in great deceleration of impact objects, which in
turn results in great impact force on the nets or fences. The
Pan-barrier, on the other hand, provides exceedingly large stopping
distance through effective configurations.
[0008] Full load of impacts. The conventional nets or fences take
the full load of impacts because they themselves stop the impact
objects completely, with gravity working against them. The
Pan-barrier, on the other hand, diverts impacts to the ground with
gravity working for it--not against it--during impact.
[0009] Embedding and sagging. The conventional nets or fences stop
impact objects by means of bulging at the point of impact;
consequently the impact objects very likely embed in the bulge,
creating unsightly sight, reducing the effectiveness and height of
the nets or fences, and requiring maintenance or even destruction
of the nets. The Pan-barrier, on the other hand, does not have
embedding and sagging problems due to its configurations.
[0010] Accumulation of debris. With time, accumulation of debris in
front of (upslope) the conventional nets or fences not only reduces
their effective height but also provides jumping ramps for
following rockfall or the like. The Pan-barrier, on the other hand,
does not have debris accumulation problem and actually benefits
from it.
[0011] Material cost for conventional nets and fences is high as
they are designed to take the full load of impacts. As the impact
energy level goes up, the cost of materials goes up quickly. The
material cost for the Pan-barrier, on the other hand, is much lower
as it is designed to dissipate only a small fraction of the impact
energy in exceedingly large stopping distances.
[0012] Labor cost for installation and maintenance is a major cost
for conventional rockfall nets and fences. Installing posts,
usually many, their tiebacks, and attaching cables and nets onto
the posts are a major part of the installation. Maintenance to keep
the fences in proper working condition requires access to the
fences and cleaning out objects embedded in and accumulated in
front of the fences. Often it is necessary to dismantle the fences
in order to do the cleaning out after each major impact, together
with replacement of braking devices. The cost of installation and
maintenance of the Pan-barrier, which is maintenance-free and
almost post-free (only requires two or three posts), is greatly
reduced.
[0013] Nets or fences with flexible posts, like U.S. Pat. No.
5,299,781 Barrett, Hearn, and McMullen, and U.S. Pat. No. 4,819,915
Cargnel, share the same problems of segmentation, short stopping
distance, full load of impact, embedding and sagging, debris
accumulation, high material cost, and high installation and
maintenance cost. While diverting some impact load to the ground,
nets or fences with flexible posts create a large load for
themselves: centrifugal force. By confining the impact objects to a
circular motion with the posts as the rigid radius, the nets or
fences have an additional centrifugal force to counter:
F=mv.sup.2/r. As the speed v of the impact objects is generally
large, magnified by the square power, and the post length r
generally small, this additional centrifugal force F created by
flexible posts is generally very large.
[0014] Many devices or mechanisms, like cable brakes, have been
invented to increase the stretching or giving capability of the
nets or fences upon impacts, like U.S. Pat. No. 6,131,873 Blazon
and Bookwater; U.S. Pat. No. 6,027,785 Yoshida; U.S. Pat. No.
5,535,861 Young; and JP Pat. No. 9,310,313 Kenkichi. These braking
or stretching devises or mechanisms, however, cannot be used
repeatedly and need to be replaced after each major impact. My
current invention, the weight braking system, on the other hand,
can be used repeatedly without limits or loss of effectiveness and
without replacement or maintenance. Unlike the conventional cable
brakes which loosen the cable after each engagement, the weight
braking system actually tightens the cable after each
engagement.
BRIEF SUMMARY OF THE INVENTION
[0015] A new safety net system called Pan-barrier is invented to
stop rockfall, landslides, debris flows, snow avalanches, or the
like, with three striking advantages: completely maintenance-free,
highly efficient in dissipating and diverting kinetic energy, and
very fast in installation. The Pan-barrier, which uses a new type
of cable braking system--the weight braking system--that can be
used or activated repeatedly without limits or maintenance, is
greatly cheaper and greatly better than currently available
rockfall or the like barriers or safety nets. The Pan-barrier
consists of the following components: 1) one frame or peripheral
cable or wire rope with its two ends attached together by wire rope
clips or the like to form a rectangular shape or the like; 2) one
or two layers of flexible mesh (chain link, double-twisted or the
like) and one optional layer of cable nets or ring nets attached
(sewed) onto the frame cable, forming the Pan-barrier sheet; 3) two
or possibly more ground anchors holding one side of the frame cable
on or close to the ground; and 4) two or possibly more supporting
cables (tiebacks), each tied to a ground anchor, erected by a post,
and equipped with the weight braking system, holding the opposite
side of the frame cable at a designed height. The Pan-barrier sheet
is installed oblique to the ground or slope, forming a wedge space
between the sheet and the ground, with the opening facing upslope
where rock falls or the like come from. Impacts occur inside the
wedge, on the ground facing or under side of the Pan-barrier
sheet.
DETAILED DESCRIPTION OF THE INVENTION
[0016] FIG. 1 shows a schematic view of the Pan-barrier system. The
Pan-barrier consists one looped frame or peripheral cable with mesh
panels and optional cable or ring net panels sewed to it, forming
the Pan-barrier sheet; two anchors (three or more if the ground is
not leveled) to hold one side of the sheet on the ground; and two
tiebacks (three if the ground is not leveled), each with its own
anchor, post and weights, hold the opposite side of the sheet to a
designed height. The Pan-barrier sheet is installed oblique to the
ground or slope (not upright). The smaller the angle between the
Pan-barrier sheet and the ground, the more efficient the
Pan-barrier system.
[0017] FIG. 2 shows a schematic top view of the Pan-barrier
system.
[0018] FIG. 3 shows a schematic cross section view of the
Pan-barrier system and a new weight tensioning and braking system.
The weight braking system is created by attaching weights (e.g.,
metals, concretes, boulders, logs) to the tieback cable on the
opposite side of the post from the Pan-barrier sheet. The weights
create sagging in the tieback cable. The benefits of the attached
weights are four-fold. First the weights keep the system tensioned
to avoid and eliminate any sagging of the Pan-barrier sheet before
impacts. Secondly, in response to impacts, the gravity and upwards
or vertical acceleration of the weights keep the tieback cable
tensioned while the cable stretches by eliminating its sagging.
Thirdly, the forward or horizontal movement of the weights with the
tieback cable reduces the speed of impact objects. Lastly, the
gravity and downward acceleration of the weights after impacts help
to tension and eliminate embedding, if any, of the Pan-barrier
sheet. Multiple weights are attached to the tieback cable to allow
sequential activation of the weight braking system. For example, a
weight that is fixed on the tieback cable (not hung from a string)
will be activated fully and immediately after impact while a weight
hung from a string to the tieback cable will be activated a split
second later due to the horizontal component of movement of the
tieback cable (a real life analogy: if you are holding a weight
through a long string and you start to move horizontally, the
weight hardly moves at the beginning). The longer the strings, the
later the activation. Similarly, multiple weights laid on the
ground and connected to the tieback cable using different lengths
of strings can also serve the purpose of sequential activation of
the weight braking system.
[0019] Large Pan-barrier is beneficial in stopping rock falls or
the like. If the mass of a Pan-barrier system, m.sub.p (including
weights for braking and tensioning), is as large as that of an
impact boulder, m.sub.b, then the mass of the Pan-barrier itself,
without any help from anchors, reduces the speed of the impact
boulder by half according to momentum conservation,
m.sub.b*v=(m.sub.b+m.sub.p)*0.5v. Or put it simply, you do not need
to exert much force when you use a heavy object to stop a light
one. On the other hand, to use a light object to stop a heavy one
is very difficult.
[0020] The connection between the frame cable and the anchors that
hold the frame cable to the ground is through rings so that
movement or sliding is allowed. The connection between the frame
cable and the tiebacks is through thimbles or the like that allows
sliding. To prevent the tiebacks from sliding into the sheet
therefore making the top side of the frame cable shorter, a stopper
like a U bolt is fixed on the frame cable (FIG. 2). During impacts
the tiebacks tend to slide to the outside (making the top side of
the frame cable longer). The connection between the tieback cables
and the posts is through pulleys or the like that allows easy
sliding. A safety device is added to keep the tieback cables from
detaching from the pulleys. Due to the easy lateral movement of the
tieback cables, the connection between the frame cable and the two
end tieback cables, however, can be fixed (no sliding).
[0021] The Pan-barrier system is not segmented. The Pan-barrier
sheet is one sheet supported by one frame cable. As a result, the
Pan-barrier system is extremely capable of giving or stretching in
response to impacts. For example, for a 400-ft (length) Pan-barrier
sheet with impacts occurred in the middle, the giving distance
would be a whopping 20 ft if the frame cable and the mesh panels,
which are large, could be stretched by 2 feet, namely
[(400+2)/2].sup.2=(400/2).sup.2+20.sup.2. In addition, the tieback
cables, which are usually quite long and are connected directly to
the frame cable, further extend the dimension of the Pan-barrier
system as a whole. With the exceptionally large stretching
capability of the tieback cables due to the weight braking system,
the giving distance of the Pan-barrier system as a whole upon
impacts is tremendous. This extremely large giving distance extends
impact time, which in turn results in small impact force, as impact
force F=mv/t, where m is the mass of impact objects, v the speed of
impact objects before impact, and t the impact time after which the
impact objects completely stop. For example, if m=20 tons, v=50
ft/s, for an impact giving distance of 0.1 foot like between a
boulder and a concrete wall (corresponding to an impact time of
0.004 second), the average impact force F is 7777 tons; if the
impact giving distance is increased to 30 feet like between a
boulder and a Pan-barrier (corresponding to an impact time of 1.2
seconds), the average impact force F is only 26 tons.
[0022] The most efficient feature of the Pan-barrier system in
reducing impact force is the small angle between the Pan-barrier
sheet and the ground. This oblique Pan-barrier sheet mainly
restricts the upward or normal movement of impact objects while
allowing movement tangential to the slope. With the help of
gravity, the sheet reduces the upwards jumping of impact objects,
and by doing so, guides them back to the ground, where most of the
tangential momentum is absorbed. Due to the oblique angle of
impact, impact objects are never stopped by the Pan-barrier sheet
but merely slide or roll under the sheet. This sliding or rolling
further increases impact distance and reduces impact force. Because
the normal momentum is small compared to tangential momentum
(jumping height is usually only a few feet to over ten feet) and
this small momentum is absorbed within extremely large giving
distance with the help of sliding, rolling and gravity, the impact
force that the Pan-barrier sheet has to absorb is very small
compared to the conventional fences, which have to absorb the full
load of energy within very short distances, with gravity working
against, not for, them. For high mountains or slopes where impact
energy is too high for conventional fences and netting the whole
mountains is too costly, the Pan-barrier system is a perfect
solution.
[0023] Maintenance free is a tremendous advantage of the
Pan-barrier system. Because impacts are on the ground-facing or
underside of the Pan-barrier sheet, impact force only pushes the
sheet higher, not lower, and embedding of objects in the
Pan-barrier sheet is very rare. In addition, the weight braking
system also helps to prevent embedding by forcefully pulling back
the tieback cable and the sheet when the weights fall back after
impacts. The accumulation of impact objects under the sheet in the
wedge-shaped space between the sheet and ground presents no problem
at all and is actually beneficial because the accumulated objects
can effectively transfer impact energy into the ground if they are
hit by later impacts. If the anticipated volume of debris
accumulation is large, reduce the angle between the Pan-barrier
sheet and the ground to increase the volume of the wedge-shaped
space under the sheet. A small angle also increases the efficiency
of the Pan-barrier system during impacts.
[0024] Fast installation is a huge advantage of the Pan-barrier
system. For leveled ground, the Pan-barrier system only requires a
total of two posts and four anchors. The frame cable is laid on the
ground first with all the mesh and net sewing and hog ringing work
done on the ground to complete the Pan-barrier sheet. Then the
sheet is pulled into place through the posts and tensioned by using
come-along or the like and further tensioned by attaching weights
to the tieback cables. For topographically uneven ground with
ridges and valleys, a third post and tieback may be needed at the
highest point in between the two end posts to help maintain the
height of the Pan-barrier sheet. If the sheet is too high over
depressions like valleys, tiebacks without posts may be installed
to pull down the top side of the frame cable. The bottom side of
the frame cable is held by necessary but minimum number of anchors
to follow ground contour.
[0025] Material cost for the Pan-barrier system is low because it
is almost post-free and does not require high-energy level impact
cable nets or ring nets.
[0026] Possible modifications to the Pan-barrier system include
attaching extra layers of mesh or nets at the toe or bottom of the
Pan-barrier sheet where impact objects finally stop. Attaching the
top of Pan-barrier sheet to a plethora of upright posts as in
conventional impact fences while attaching the bottom of the sheet
to ground anchors located away from the posts are possible
modifications to the Pan-barrier system. Another possible
modification to the Pan-barrier system, although not recommended,
is to install a plethora of posts oblique to ground and attach the
barrier sheet to both the top and bottom of the oblique posts.
Draping a screen of mesh or the like from the top side of the frame
cable of the Pan-barrier sheet at the opening of the wedge space is
another possible modification to the Pan-barrier system. This
draped screen is to slow down objects before impact with the
Pan-barrier sheet.
* * * * *