U.S. patent application number 13/061588 was filed with the patent office on 2011-10-13 for method and arrangement for detection and destruction of tunnels.
This patent application is currently assigned to Avner and Yossi Civil Engineering and Projects Ltd. Invention is credited to Avner Aviram.
Application Number | 20110250021 13/061588 |
Document ID | / |
Family ID | 40585541 |
Filed Date | 2011-10-13 |
United States Patent
Application |
20110250021 |
Kind Code |
A1 |
Aviram; Avner |
October 13, 2011 |
METHOD AND ARRANGEMENT FOR DETECTION AND DESTRUCTION OF TUNNELS
Abstract
A method and arrangement for destroying tunnels. A
subterraneous, vertical shaft is excavated until a tunnel
preventing depth. After liquid is introduced to the shaft, a shaft
liner is penetrable by the introduced liquid when a tunnel is
present in the vicinity of said shaft, due to the considerably
larger pressure of the introduced liquid relative to the bearing
capacity of soil interposed between the tunnel and shaft. The
tunnel is then flooded and destroyed following passage of the
liquid through the liner. A system for detecting and destroying
tunnels in the proximity of a security-sensitive facility comprises
a hollow member anchored to the upper soil surface adjoining each
shaft, a sensor having a unique address mounted on a corresponding
hollow member for generating an electrical output when the liquid
level has been reduced more than a predetermined level, and a
computer in data communication with each of the sensors.
Inventors: |
Aviram; Avner; (Lehavim,
IL) |
Assignee: |
Avner and Yossi Civil Engineering
and Projects Ltd
Lehavim
IL
|
Family ID: |
40585541 |
Appl. No.: |
13/061588 |
Filed: |
September 1, 2008 |
PCT Filed: |
September 1, 2008 |
PCT NO: |
PCT/IL2008/001183 |
371 Date: |
June 27, 2011 |
Current U.S.
Class: |
405/258.1 |
Current CPC
Class: |
E21D 1/00 20130101 |
Class at
Publication: |
405/258.1 |
International
Class: |
E21F 15/08 20060101
E21F015/08 |
Claims
1. A method for destroying tunnels, comprising: a) excavating a
subterraneous, substantially vertical shaft until a tunnel
preventing depth; b) applying a liner onto, or adjacent to, the
inner wall/walls of said shaft; c) introducing liquid to said shaft
until said shaft is substantially filled; and d) allowing said
liquid to burst said liner when a tunnel is present in the vicinity
of said shaft, due to the considerably larger pressure of said
introduced liquid relative to the bearing capacity of soil
interposed between the tunnel and shaft, thereby flooding and
destroying the tunnel.
2. The method according to claim 1, wherein the liner is a sealing
element.
3. The method according to claim 1, wherein the liner is polymeric
material.
4. The method according to claim 1, wherein the liner is a flexible
hollow element having an open proximal end and a closed distal
end.
5. The method according to claim 4, wherein the liner is applied
adjacent to the wall/walls of the shaft by: a) placing the liner at
the proximal end of the shaft; b) introducing liquid to the shaft
while the proximal end of said liner is retained until the shaft is
substantially filled, whereby the liner expands substantially to
the inner wall/walls of the shaft after liquid is introduced into
the shaft; and c) anchoring the proximal end of said liner.
6. The method according to claim 4, wherein the liner is
rubber.
7. The method according to claim 1, wherein the introduced liquid
is water.
8. The method according to claim 1, further comprising the step of
detecting a tunnel by sensing a reduced depth of liquid in the
shaft.
9. The method according to claim 8, wherein the depth of liquid in
the shaft is sensed by anchoring a hollow member to the proximal
end of the shaft; and deploying sensing equipment in contact with
said hollow member.
10. The method according to claim 9, wherein the depth of liquid in
the shaft is sensed visually.
11. The method according to claim 10, wherein a float provided with
an upwardly extending rod is placed on the upper layer of the
introduced liquid; and a tunnel is detected by visually sensing a
reduced protrusion of the rod from the upper soil surface.
12. The method according to claim 10, wherein the protrusion of
each corresponding rod from the upper soil surface is compared,
when a plurality of shafts are employed.
13. The method according to claim 9, wherein the depth of liquid in
the shaft is sensed by a sensor.
14. The method according to claim 13, wherein the sensor is
selected from the group of limit switch, interphase sensor, and
capacitive transduction sensor.
15. The method according to claim 8, wherein the shaft is filled
with tunnel preventing material after the presence of a tunnel is
detected.
16. An arrangement for destroying tunnels, comprising: a
subterraneous, substantially vertical shaft; and a liner applied
onto, or adjacent to, the inner wall/walls of said shaft, said
liner adapted for retaining liquid introduced into said shaft,
wherein said liner is penetrable by said introduced liquid when a
tunnel is present in the vicinity of said shaft, due to the
considerably larger pressure of said introduced liquid relative to
the bearing capacity of soil interposed between the tunnel and
shaft, the tunnel being flooded and destroyed following passage of
said liquid through said liner.
17. The arrangement according to claim 16, wherein the liner is a
flexible hollow element having an open proximal end and a closed
distal end, said proximal end being anchored to an upper soil
surface and said liner being expandable within the shaft upon the
introduction of a liquid therewithin.
18. The arrangement according to claim 16, further comprising means
for detecting the presence of a tunnel.
19. The arrangement according to claim 18, wherein the means for
detecting the presence of a tunnel comprises a sensor for sensing a
reduced depth of liquid within the shaft.
20. The arrangement according to claim 19, further comprising a
hollow member which is anchored to the upper soil surface,
equipment associated with a sensor being in contact with said
hollow member.
21. The arrangement according to claim 20, wherein the sensor is a
float provided, with an upwardly extending rod which is placed on
the upper layer of the introduced liquid, a tunnel being detected
by visually sensing a reduced protrusion of the rod from the upper
soil surface.
22. The arrangement according to claim 21, wherein the shaft is
covered by a cover provided with a tube downwardly extending from
the underside thereof, for encircling the rod and retaining it in a
substantially upright position.
23. The arrangement according to claim 20, wherein the sensor is
mounted on the hollow member.
24. The arrangement according to claim 23, wherein the sensor is
selected from the group of limit switch, interphase sensor, and
capacitive transduction sensor.
25. A system for detecting and destroying tunnels in the proximity
of a security-sensitive facility, comprising: a) a plurality of
subterraneous, substantially vertical shafts excavated in the
proximity of a security-sensitive facility; b) a liner applied
onto, or adjacent to, the inner wall/walls of each of said shafts,
for retaining liquid introduced into the corresponding shaft,
wherein each of said liners is penetrable by said introduced liquid
when a tunnel is present in the vicinity of the corresponding
shaft, due to the considerably larger pressure of said introduced
liquid relative to the bearing capacity of soil interposed between
the tunnel and said shaft, the tunnel being flooded and destroyed
following passage of said liquid through said liner; c) a hollow
member insertable within, and anchored to the upper soil surface
adjoining, each shaft; d) a sensor mounted on the hollow member of
each shaft for sensing a reduced depth of liquid within the
corresponding shaft and generating an electrical output when the
liquid level has been reduced more than a predetermined level, each
sensor being assigned a unique address; and e) a computer in data
communication with each of the sensors, for displaying the address
of each sensor that generated an electrical output.
Description
FIELD OF THE INVENTION
[0001] The present invention relates to the field of detection
equipment. More particularly, the invention relates to a method and
arrangement for detecting tunnels.
BACKGROUND OF THE INVENTION
[0002] Due to the increasing number of worldwide terrorist
activities, terrorists have become more daring and imaginative in
terms of the way that they perpetrate their malicious schemes. Many
terrorists have recently dug tunnels underneath military posts,
through which arms, weapons, and even heavy machinery are smuggled
without being noticed by security personnel. By digging tunnels in
a carefully planned fashion and passing through the tunnels, some
terrorists succeed in infiltrating security-sensitive facilities
such as military posts, jails, airports, nuclear power plants and
international borders.
[0003] Many methods are known for locating tunnels, such as by
magnetic, optic and ultrasonic means. However, none of these
methods are capable of both detecting and destroying tunnels
simultaneously. A need therefore exists for detecting and
destroying tunnels simultaneously.
[0004] It is an object of the present invention to provide a method
and arrangement for simultaneous detection and destruction of newly
dug tunnels.
[0005] It is an additional object of the present invention to
provide a method and arrangement for the automatic destruction of
newly dug tunnels prior to human detection thereof.
[0006] Other objects and advantages of the invention will become
apparent as the description proceeds.
SUMMARY OF THE INVENTION
[0007] The present invention provides a method for destroying
tunnels, comprising excavating a subterraneous, substantially
vertical shaft until a tunnel preventing depth; applying a liner
onto, or adjacent to, the inner wall/walls of said shaft;
introducing liquid to said shaft until said shaft is substantially
filled; and allowing said liquid to burst said liner when a tunnel
is present in the vicinity of said shaft, due to the considerably
larger pressure of said introduced liquid relative to the bearing
capacity of soil interposed between the tunnel and shaft, thereby
flooding and destroying the tunnel.
[0008] As referred to herein, the "tunnel preventing depth" to
which a shaft is excavated means a depth underneath an upper soil
surface which will not support the digging of a tunnel due to the
low bearing capacity of the soil, e.g. gravel, at said depth, due
to the existence of groundwater at said depth, or due to the
relatively high labor-intensive or time-consuming process which is
needed for the removal of soil constituents at that depth, such as
a solid ledge of hard rock, e.g. granite, or of hardpan at a depth
of e.g. 50 m.
[0009] For most types of soil adjoining the tunnel, the liner is a
sealing element or polymeric material.
[0010] When the soil adjoining the tunnel is sand, the liner is a
flexible hollow element, such as rubber, having an open proximal
end, i.e. the end closer to the upper soil surface, and a closed
distal end, i.e. the end more distant from the upper soil surface.
The liner is applied adjacent to the wall/walls of the shaft by:
placing the liner at the proximal end of the shaft; introducing
liquid to the shaft while the proximal end of said liner is
retained until the shaft is substantially filled, whereby the liner
expands substantially to the inner wall/walls of the shaft after
liquid is introduced into the shaft; and anchoring the proximal end
of said liner.
[0011] As referred to herein, a liner is "anchored" when its
proximal end is fixedly attached to the upper soil surface. Typical
anchoring means include stakes, plaster, concrete, stones, packed
sand, and the like.
[0012] Preferably, the introduced liquid is water.
[0013] In a preferred embodiment of the invention, a tunnel is
detected by sensing a reduced depth of liquid in the shaft.
[0014] In one aspect, the depth of liquid in the shaft is sensed by
anchoring a hollow member, together with the proximal end of the
liner, if a hollow liner is employed, to the proximal end of the
shaft; and deploying sensing equipment in contact with said hollow
member.
[0015] In one aspect, the depth of liquid in the shaft is sensed
visually. A float provided. with an upwardly extending rod is
placed on the upper layer of the introduced liquid; and a tunnel is
detected by visually sensing a reduced protrusion of the rod from
the upper soil surface. When a plurality of shafts are employed,
the protrusion of each corresponding rod from the upper soil
surface is compared.
[0016] In one aspect, the depth of liquid in the shaft is sensed by
a sensor. The sensor is selected from the group of limit switch,
interphase sensor, and capacitive transduction sensor.
[0017] Following the destruction of a tunnel in the, vicinity of a
shaft by the liquid bursting the liner of the shaft and flooding
the tunnel, the soil interposed between the flooded tunnel and
shaft is in a collapsed configuration. After the presence of said
tunnel is detected, as indicated by a reduced depth of liquid in
the shaft, the shaft is preferably filled with tunnel preventing
material, such as concrete.
[0018] The present invention is also directed to an arrangement for
destroying tunnels, comprising: a subterraneous, substantially
vertical shaft; and a liner applied onto, or adjacent to, the inner
wall/walls of said shaft, said liner adapted for retaining liquid
introduced into said shaft, wherein said liner is penetrable by
said introduced liquid when a tunnel is present in the vicinity of
said shaft, due to the considerably larger pressure of said
introduced liquid relative to the bearing capacity of soil
interposed between the tunnel and shaft, the tunnel being flooded
and destroyed following passage of said liquid through said
liner.
[0019] In one aspect, the liner is a flexible hollow element having
an open proximal end and a closed distal end, said proximal end
being anchored to an upper soil surface and said liner being
expandable within the shaft, upon the introduction of a liquid
therewithin.
[0020] In a preferred embodiment of the invention, the arrangement
further comprises means for detecting the presence of a tunnel.
[0021] The means for detecting the presence of a tunnel preferably
comprises a sensor for sensing a reduced depth of liquid within the
shaft.
[0022] In one aspect, the arrangement further comprises a hollow
member which is anchored, together with the proximal end of the
liner, to the upper soil surface, equipment associated with a
sensor being in contact with said hollow member.
[0023] In one aspect, the sensor is a float provided with an
upwardly extending rod which is placed on the upper layer of the
introduced liquid, a tunnel being detected by visually sensing a
reduced protrusion of the rod from the upper soil surface. The
shaft is preferably covered by a cover provided with a tube
downwardly extending from the underside thereof, for encircling the
rod and retaining it in a substantially upright position.
[0024] In one aspect, the sensor is mounted on the hollow member.
The sensor is selected from the group of limit switch, interphase
sensor, and capacitive transduction sensor.
[0025] The present invention is also directed to a system for
detecting and destroying tunnels in the proximity of a
security-sensitive facility, comprising: [0026] a) a plurality of
subterraneous, substantially vertical shafts excavated in the
proximity of a security-sensitive facility, such as military posts,
jails, airports, nuclear power plants and international borders;
[0027] b) a liner applied onto, or adjacent to, the inner
wall/walls of each of said shafts, for retaining liquid introduced
into the corresponding shaft, wherein each of said liners is
penetrable by said introduced liquid when a tunnel is present in
the vicinity of the corresponding shaft, due to the considerably
larger pressure of said introduced liquid relative to the bearing
capacity of soil interposed between the tunnel and said shaft, the
tunnel being flooded and destroyed following passage of said liquid
through said liner; [0028] c) a hollow member insertable within,
and anchored to the upper soil surface adjoining, each shaft;
[0029] d) a sensor mounted on the hollow member of each shaft for
sensing a reduced depth of liquid within the corresponding shaft
and generating an electrical output when the liquid level has been
reduced more than a predetermined level, each sensor being assigned
a unique address; and [0030] e) a computer in data communication
with each of the sensors, for displaying the address of each sensor
that generated an electrical output.
BRIEF DESCRIPTION OF THE DRAWINGS
[0031] In the drawings:
[0032] FIG. 1 is a schematic drawing of an arrangement according to
one embodiment of the invention, showing a shaft filled with a
liquid to a first level;
[0033] FIG. 2 is a schematic drawing of the arrangement of FIG. 1,
showing the egress of liquid from the shaft when a tunnel is
detected in the presence thereof and the liquid level is reduced to
a second level;
[0034] FIG. 3 is a schematic plan view of a plurality of shafts
excavated along one row; and
[0035] FIG. 4 is a schematic plan view of a plurality of shafts
excavated in offset formation.
DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS
[0036] FIG. 1 illustrates an arrangement for detecting and
destroying tunnels according to one preferred embodiment of the
invention, which is designated by numeral 10. Arrangement 10, which
is suitable for destroying tunnels dug in sand, comprises
subterraneous, substantially vertical annular shaft 5 which is
excavated within soil body 9 to a depth corresponding to
approximately the depth of the lowest anticipated level of
groundwater 7, flexible tubelike liner 13 having a proximal open
end and a closed distal end, e.g. rubber, nylon, or any other
suitable thin plastic material having a thickness ranging between 2
microns to 1 mm, and annular member 17, the outer diameter of which
is slightly less than the inner diameter of shaft. After annular
member 17, which is made of structurally strong material such as
fiberglass, polypropylene, plastic or galvanized steel, is inserted
within shaft 5 such that it protrudes slightly from upper surface
11 of soil body 9 and the proximal end of liner 13 is interspersed
between annular member 17 and soil body 9, the proximal end of
liner 13 and the portion of annular member 17 below upper surface
11 of the soil body are anchored to the soil body by means of
concrete slab 22.
[0037] After liquid, e.g. water, is introduced into shaft 5, liner
13 expands to substantially the inner wall of the shaft. When the
upper surface of liquid body 15 which is retained within shaft 5 is
at a level of L.sub.1, float 25 connected to upwardly extending rod
27 is placed on the upper surface of liquid body 15. Cover 19 is
provided with tube 29, which extends downwardly from the underside
thereof and has an outer diameter slightly larger than the
thickness of rod 27, is lowered onto annular member 17 such that
tube 29 encircles rod 27 and retains the latter in an upright
position. The typical pressure of liquid body 15 at a predetermined
depth below L.sub.1 is on the order of 10,000 kg/m.sup.2 at a depth
of 10 m.
[0038] With reference to FIG. 2, tunnel 39, which is normally
horizontally dug, is shown to be at a depth D below upper surface
11 of the soil body. When tunnel 39 attains a characteristic
separation distance B from shaft 5, the bearing capacity of soil
between tunnel 39 and shaft 5 is reduced to such a degree, due to
its reduced thickness, that liner 13 is burst at opening O. Liquid
flows at a tremendously high flow rate from shaft 5 to tunnel 39
while permeating the interposed soil I, whereby interposed soil I
collapses and tunnel 39 is flooded and destroyed.
[0039] It will be appreciated that the flow rate of liquid flowing
through burst opening O is a function of many factors, including
the type and bearing capacity of soil interposed between the tunnel
and shaft, the depth of the tunnel, the diameter of the tunnel, and
the pressure of the liquid retained within the shaft at a depth
corresponding to the depth of the tunnel. The flow rate of the
liquid which bursts forth from opening O is at first relatively
low, and then increases exponentially while the size of the opening
increases.
[0040] Due to the egress of liquid from shaft 5, the level of
liquid body 15 is lowered to L.sub.2. Float 25 and rod 27 connected
thereto are consequently lowered as well, thereby indicating to an
operator that liquid has exited the shaft and that a tunnel is
present in the vicinity thereof. An operator generally determines
the liquid level within shaft 5 on a regular basis by visually
inspecting the height of rod 27 and informs security personnel that
a tunnel has been detected. In order to inhibit formation of a new
tunnel from the destroyed tunnel, after permeation of liquid
through the adjoining soil, security personnel may fill the shaft
with tunnel preventing material, such as concrete.
[0041] Other sensors (not shown) may be employed as well for
detecting the presence of a tunnel in the vicinity of the shaft.
One suitable sensor is a limit switch, e.g. a discrete level
switch, mounted onto the annular member that is anchored to the
upper soil surface adjoining the shaft, and the limit switch is
electrically connected to a float and cable. The operator may
determine the liquid level contained within the shaft as the float
rises and descends within the annular member. The cable is
connected to a meter or to an alarm, indicating that the liquid
level is at a maximum level, or alternatively, has lowered
significantly below the maximum level. The sensor may also be an
interphase sensor which monitors the transition between the two
phases of liquid and air, indicating to the operator when the
liquid level falls below a predetermined level.
[0042] The sensor may also be a capacitive transduction sensor,
which determines a change in height of the liquid contained within
the shaft by measuring the change in the dielectric constant
between an outer electrode and inner electrode. Such a sensor is
provided with an electrode housing mounted onto the annular member,
a liquid column inlet disposed at the bottom of the electrode
housing, a measurement circuitry card, and a cable connection. The
measurement circuitry card contained within the housing measures
the instantaneous capacitance, which is directly proportional to an
output voltage. When the output voltage falls below a predetermined
threshold, a signal such as an alarm may be generated.
[0043] If so desired, depending on the composition of the soil
adjoining the shaft, the liner may a sealing element or polymeric
material which is applied directly onto the wall or walls of the
shaft. The shaft may be circular, square, or any other convenient
shape. Similarly, the hollow member, with which a sensor is in
contact and which is anchored to the upper soil surface adjoining
the shaft, may be circular, square, or any other convenient
shape.
[0044] As shown in FIGS. 3 and 4, a plurality of shafts may be
employed, for tunnel detection in the vicinity of a
security-sensitive facility. The plurality of shafts, such as
shafts 5A-5D shown in FIG. 3, may be excavated along one row. For
example, when the inner- diameter of the shafts range from 80-100
cm, the spacing between adjacent shafts may be 100 cm. Therefore,
the maximum, separation from a tunnel to a shaft will not be more
than 20 cm, for an average tunnel diameter of 80 cm, thereby
resulting in the bursting of the liner in the shaft closest to the
tunnel. Alternatively, the plurality of shafts, such as shafts
5E-5H shown in FIG. 4, may be arranged in offset formation. For
example, when the inner diameter of shafts range from 80-100 cm,
the spacing between adjacent shafts 5E-5F of one row ranges from
28-300 cm, while the spacing between shafts 5E and 5G of two
different rows is 200 cm. If a tunnel were detected in the vicinity
of a shaft, e.g. shaft 5F, causing liquid to burst forth therefrom,
shaft 5F is filled with tunnel preventing material 31, and three
additional shafts 5I-5K are excavated in the vicinity of shaft 5F,
to prevent a malicious person from continuing the tunnel formation
by circumventing shaft 5F. If the malicious person were to
reconstruct the tunnel, which is represented by arrow 35, and
continue digging in a straight path, he would encounter shaft 5F
which is filled with tunnel preventing material. If he were
interested in the time-consuming process of removing the tunnel
preventing material in order to continue the previous direction of
the tunnel, the malicious person would approach shaft 5J and the
tunnel would be destroyed and flooded by the liquid bursting
therefrom. If the malicious person decided to change the direction
of the tunnel, as represented by arrow 36, the tunnel would be
destroyed and flooded by the liquid bursting from shaft 51 when the
end of the tunnel is separated from shaft 51 by a distance less
than the characteristic separation B (FIG. 2) which causes the
corresponding liner to burst.
[0045] An array of shafts provided with liners in accordance with
the present invention on the order of a hundred or even a thousand
shafts may be employed to detect the presence of a tunnel in the
proximity of a security-sensitive facility such as military posts,
jails, airports, nuclear power plants and international borders. A
sensor which generates an electrical output is associated with each
shaft and is assigned a unique address. The electrical output of
each sensor is in data communication with a computer at a control
center. When the liquid level contained within a shaft is lowered
more than a predetermined value, indicating the presence of a
tunnel in the vicinity of that shaft, the address of the sensor
which generated the warning signal is displayed. Security personnel
are then dispatched to the vicinity of the shaft, corresponding to
the displayed sensor address, whereupon the shaft having the
reduced liquid level is filled with tunnel preventing material.
[0046] While some embodiments of the invention have been described
by way of illustration, it will be apparent that the invention can
be carried into practice with many modifications, variations and
adaptations, and with the use of numerous equivalents or
alternative solutions that are within the scope of persons skilled
in the art, without departing from the spirit of the invention or
exceeding the scope of the claims.
* * * * *