WO2016020924A1

WO2016020924A1 - System for detecting underground tunnels

Info

Publication number: WO2016020924A1
Application number: PCT/IL2015/050805
Authority: WO
Inventors: Matanel LIBI
Original assignee: Libi Matanel
Priority date: 2014-08-07
Filing date: 2015-08-06
Publication date: 2016-02-11

Abstract

A system for detecting underground tunnels. The system has a multitude of transparent receiving pipes that are positioned into ground at a given pipe spacing therebetween. A light sensor, connected to a control unit, is positioned at an upper end of each of the receiving pipes. When a receiving pipe is exposed to light from an underground tunnel, the light sensor senses the existence of light and passes a received signal to the control unit, which processes the received signal and activates a warning signal.

Description

SYSTEM FOR DETECTING UNDERGROUND TUNNELS

FIELD OF THE INVENTION

The present invention relates to the field of underground detection, and more particularly to the field of detection of human made underground tunnels.

BACKGROUND OF THE INVENTION

Human made underground tunnels exist in a variety of shapes and forms. The tunnels may serve various uses, for example, cable placing, pipe placing, supply transporting, and the like. The tunnels may be of various sizes, i.e., they may be very shallow, to enable passing therethrough by crawling or by laying on a trolley that rides on tracks, they me be tall enough, to enable passing of men therethrough, standing upright or slightly bent, or, they may be large enough to enable to vehicles drive therethrough, like cars, trucks, and trains.

The tunnels may be digged in a variety of soil types, such as; sand, coarse sand, ground, gravel, clay, semi-rocky, rocky, etc.

Unfortunately, in many cases tunnels are digged and used for improper, illegal, or hostile purposes. Tunnels are digged for escaping from prisons or detention camps, and for smuggling goods or people across borders. Lately, tunnels are being digged by terrorists in order to smuggle weapons and explosives, in order to booby-trap remote sites without being exposed, and, in order to cross the border in order to kidnap civilians or soldiers or in order to commit a major sabotage event. Systems for detecting underground tunnels are known. There are many systems available in the market and they vary in their mode of operation.

Some systems send sonar waves, from the upper surface of the land in a downward direction. Typically, various transmitting sites are used. The return echo is analyzed by a central processing unit that identifies changes in the soil density. These kinds of systems are limited in the depth that can be monitored and their reading error greatly depends on the type of soil.

US Pat. No. 8,577,830 to Klar et al. discloses a non-transitory computer readable medium and a method for detection of tunnel excavation by brillouin optical time domain reflectometry using multiple underground optical fibers. The method includes: propagating a light pulse through an underground optic fiber, generating detection signals responsive to Brillion scattered light resulting from the propagating of the light pulse through the underground optic fiber. Wherein, the detection signals represent tension values at multiple locations along the underground optic fiber, and processing the detection signals to detect excavation of the underground tunnel.

The '830 patent encounters several disadvantages. First, an entire trench has to be digged along the entire protection-desired area. Second, the trench is limited in the depth that can be reached. Third, the system is practically limited in the depth that can be measured. Fourth, the system is susceptible to environmental disturbances. Fifth, the system has a high error value. Sixth, the system is very expensive to implement. Seventh, the system requires a very complex control system. Eighth, in a case where the digging of the tunnel is such that a construction supportive arc is immediately implemented during forward digging, and, therefore, no strain fluctuations are encountered in the soil above the tunnel, then, practically, the system could not detect the tunnel.

Another article by Assaf Klar and Raphael Linker discloses a feasibility study of the automated detection and localization of underground tunnel excavation using Brillouin optical time domain reflectometer.

The article teaches that cross-borders smuggling tunnels enable unmonitored movement of people, drugs and weapons and pose a very serious threat to homeland security. Recent advances in strain measurements using optical fibers allow the development of smart underground security fences that could detect the excavation of smuggling tunnels. This paper presents the first stages in the development of such a fence using Brillouin Optical Time Domain Reflectometry (BOTDR). In the simulation study, two different ground displacement models are used in order to evaluate the robustness of the system against imperfect modeling. In both cases, soil-fiber interaction is considered. Measurement errors, and surface disturbances (obtained from a field test) are also included in the calibration and validation stages of the system. The proposed detection system is based on wavelet decomposition of the BOTDR signal, followed by a neural network that is trained to recognize the tunnel signature in the wavelet coefficients. The results indicate that the proposed system is capable of detecting even a small tunnel (0.5m diameter) as deep as 20 meters.

Again, this system suffers from similar disadvantages as described with respect to the '830 patent.

Some detection systems known in the market measure small vibrations or movements of the soil. These systems are limited in the depth in which a tunnel may be detected. Furthermore, these systems are susceptible to environmental vibrations, such as traffic, engines, heavy land machinery, etc.

There are detection systems that are capable of measuring very quiet sounds, such as sounds of moles and termites. However, a disadvantage of these systems is that they are very susceptible to environmental sounds and can be easily mislead by an intentionally generated false underground sound.

It is the object of the present invention to provide a system for detecting underground tunnels that significantly reduces or overcomes the aforementioned disadvantages.

It is a further object of the present invention to provide a system for detecting underground tunnels that is not limited in the measuring depth.

It is still a further object of the present invention to provide a system for detecting underground tunnels that is easy to implement and control.

It is still yet a further object of the present invention to provide a system for detecting underground tunnels that is relatively cheap.

It is another object of the present invention to provide a system for detecting underground tunnels that is multi-functional.

It is still another object of the present invention to provide a system for detecting underground tunnels that provides multiple sensoring.

It is still yet another object of the present invention to provide a system for detecting underground tunnels with practically no errors.

It is also another object of the present invention to provide a method for detecting underground tunnels.

SUMMARY OF THE INVENTION

In accordance with the present invention there is provided a system for detecting underground tunnels, the system comprises:

a multitude of transparent receiving pipes positioned in the ground, each of the receiving pipes having a pipe upper end,

a light sensor positioned at the pipe upper end of each of the receiving pipes,

a control unit connected with each of the light sensors, wherein:

when a receiving pipe is exposed to light from an underground tunnel, the light sensor senses the existence of light and passes a received signal to the control unit, and the control unit processes the received signal and activates a warning signal.

Advantageously, the receiving pipes are positioned vertically.

Further advantageously, the receiving pipes are positioned along a detection envelope.

Typically, the receiving pipes are spaced apart a pipe spacing of less than lm.

Practically, the pipe spacing between the receiving pipes is 0.5m.

In most cases, the light sensor is a CCD sensor. Advantageously, the light sensor is capable of sensing very small luminous intensity.

If desired, the control unit monitors a multitude of receiving pipes.

In some embodiments, each of the receiving pipes is placed within a perforated leading pipe.

Advantageously, each of the receiving pipes has a pipe bottom and is provided with an illumination element, located at the pipe bottom and wired by metallic conductors to the control unit.

Typically, the illumination element constitutes a LED.

Advantageously, each of the illumination elements is periodically tested for light emitting,

the control unit is calibrated to a given luminous intensity value received during the periodical testing, and

in a case of mismatch between the given luminous intensity value and a measured luminous intensity value, the control unit activates a warning signal.

If desired, at least one of the receiving pipes is provided with a horoscope camera therein.

Further if desired, at least one of the receiving pipes is provided with an at least one additional sensing unit therein.

Typically, the additional sensing unit comprises one or more sensors from the groups of: sound sensors, motion sensors, vibration sensors.

Further typically, each of the receiving pipes is placed within a hole having a drilling diameter of 1" or 25.4mm.

Further in accordance with the present invention there is provided a process for detecting underground tunnels, the process comprising the steps of:

a. Placing a multitude of transparent receiving pipes in the ground, each of the receiving pipes having a pipe upper end.

b. Positioning a light sensor at the pipe upper end of each of the receiving pipes.

c. Connecting each of the light sensors to a control unit. d. When a receiving pipe is exposed to a light from an underground tunnel, the light sensor senses the existence of light and passes a received signal to the control unit, and the control unit processes the received signal and activates a warning signal.

Preferably, the process further comprising the steps of:

a. Providing an illumination element within a pipe bottom of each of the receiving pipes, the illumination element being connected to the control unit by means of metallic conductors.

b. Periodically testing each of the illumination elements.

c. Calibrating the control unit to a given luminous intensity value received during the periodical testing,

d. Activating a warning signal by the control unit in a case of mismatch between the given luminous intensity value and the measured luminous intensity value.

If desired, the process further comprising the step of:

1- Providing a horoscope camera within at least one of the receiving pipes.

Further if desired, the process further comprising the step of:

1- Providing at least one of the receiving pipes with an at least one

additional sensing unit therein, the sensing unit comprises one or more sensors from the groups of: sound sensors, motion sensors, vibration sensors.

Advantageously, the process further comprises the step of placing each of the receiving pipes within a perforated leading pipe. BRIEF DESCRIPTION OF THE DRAWINGS

For a better understanding of the present invention and to show how the same may be carried out in practice, reference will now be made to the accompanying drawings, in which:

Fig. 1 is a vertical cross-section of a system for detecting underground tunnels according to the present invention; Fig. 2 is a top view of the system for detecting underground tunnels of

Fig. 1;

Fig. 3 is a partial side cross-sectional view of a leading pipe within a pipe cavity;

Fig. 4 is a partial perspective view of a leading pipe formed with through holes; and

Fig. 5 is a partial perspective view of a leading pipe formed with through slots. DESCRIPTION OF PREFERRED EMBODIMENTS

Attention is first drawn to Fig. 1 that shows a system for detecting underground tunnels 10 according to the present invention. For a matter of simplicity, the system for detecting underground tunnels will hereinafter be called the "system".

In Fig. 1, since a width dimension of the system 10 (taken in the plane of the figure, perpendicularly to the depth or height dimension) is much smaller than the depth involved, the various parts of the figure are not shown in scale in order to enable better readability of the figure.

The system 10 according to the present invention is used within ground 12 practically up to depths of ground water 14. In some sites, the ground water 14 is found in a ground water depth 16 that may be between 40 meters and 60 meters. However, the system 10 may be equally implemented to depths up to 100m as well, and above.

Practically, hostile underground tunnels 40 are digged up to depths that are above the ground water 14 at a specific site, since digging deeper involves much more sophisticated equipment and much higher safety risks.

It should be noted that directional terms appearing throughout the specification and claims, e.g. "forward", "rear", "upper", "lower" etc., are used as terms of convenience to distinguish the location of various surfaces relative to each other. These terms are defined with reference to the figures, however, they are used for illustrative purposes only, and are not intended to limit the scope of the appended claims.

The system 10 comprises a receiving pipe 18 that is inserted into ground 12 up to a desired detecting depth 20. The receiving pipe 18 is transparent and may be formed from several adequate materials, such as plastic, polycarbonate, and the like. Typically, the receiving pipe 18 is formed from a single unit, is flexible, and is wound on a large reel (not shown) prior to insertion into ground 12.

An illumination element, typically a LED 22, is inserted into the receiving pipe 18 up to its pipe bottom 24. The pipe bottom 24 may have an open end or a closed end, depending on the way of application of the receiving pipe 18. The LED 22 is wired by two metallic conductors 26, such as copper wires, which protrude outwardly above an open pipe upper end 28.

The entire portion of the receiving pipe 18 that is protruding upwardly above ground level 30, namely, a pipe protruding portion 32, is enclosed within an end box 34 that is completely sealed against any penetration of light therein. Thus, the only portion of the receiving pipe 18 that is uncovered is the pipe upper end 28.

A CCD sensor 36 is installed on the pipe upper end 28. According to some embodiments, the pipe upper end 28 and the CCD sensor 36 are located within the end box 34 as well. The CCD sensor 36 is very sensitive and it signals when it senses even a very weak light or very small luminous intensity.

The CCD sensor 36, as well as the metallic conductors 26 connected to the LED 22, are connected to a control unit 38. The control unit 38 may be formed on top of the end box 34, be a part of the end box 34, or, formed separated from the end box 34. The control unit 38 monitors light signals received by the CCD sensor 36 and processes them to an alarm signal, remote alarm, visual indication, text warning message, etc.

In order to verify intactness and proper functioning of the system 10, the LED 22 is energized for a short period at pre-determined intervals. The intervals may be in seconds, minutes, hours, or days. Thus, if the system 10 is intact and proper functioning, the LED 22 will illuminate at its standard illuminating level and some of the light produced by the LED 22 will be received by the CCD sensor 36. Since the light intensity received by the CCD sensor 36 will be practically the same at every operation of the LED 22, the control unit 38 is calibrated to receive this signal as a check signal and will not classify it as a warning producing signal.

In order to form a practical system 10 that can detect underground tunnels 40 in a pre-determined detection area, a multitude of receiving pipes 18 are installed into ground 12 thus forming a continuous detection envelope 42 as shown in Fig. 2. The detection envelope 42 separates between an undetected hostile area 44 and a detected safe area 46. The receiving pipes 18 may be installed at desired inclination angles, however, for a matter of simplicity, typically the multitude of receiving pipes 18 are installed vertically.

Each receiving pipe 18 is distanced from its adjacent receiving pipes 18 by a similar horizontal pipe spacing 48. Even though it is most desired that the pipe spacing be less than lm, typically, for maximum security assurance, the pipe spacing 48 equals 0.5m. On field, when an underground tunnel 40 is being digged forwardly in a digging direction 50 and in a digging depth 52, as measured from the ground level 30 to a tunnel base 54, the underground tunnel 40 is typically digged by three methods: (a) automatically digging by means of a "mechanical mole" that excavates ground and moves it rearwardly, or, mechanically pressing the excavated ground onto the periphery of the underground tunnel. This method is seldom used for digging hostile underground tunnels, (b) manually operating power tools such as drills, and power excavation hammers and chisels. These tools may be electrical, pneumatical, or self -powered, (c) manually excavating by means of hand tools such as chisel, hammer, pick-axe, shovel, spade, etc.

In order to prevent collapsing of ceiling and walls of the underground tunnel 40, a tunnel support 56 is fixed to the tunnel ceiling 58 and to the tunnel walls 60. The tunnel support 56 is formed from; pre-cast concrete elements, on-site concrete casting, wood beams and plates, steel beams and plates, plastic beams and plates, and the like.

During excavation, a tunnel front portion 62 is always exposed and susceptible to collapsing before a tunnel support 56 is fixed to the tunnel ceiling 58 and to the tunnel wall 60.

A tunnel width 64 that enables quick and easy passing therethrough of men with personal equipment is typically of 0.6m to 1.2m. Therefore, since an average pipe spacing 48 is of 0.5m, when the tunnel front portion 62 advances by excavation in the digging direction 50, it will meet at least one receiving pipe 18 as can be clearly seen in Fig. 2.

When the receiving pipe 18 is met by the excavation tool, even without being broken or cut, at least a portion of the receiving pipe 18 is exposed to the light existing in the underground tunnel 40. At this stage, the CCD sensor 36 located at the pipe upper end 28 senses the light, and, through the control unit 38, an alarm signal is generated.

Each control unit 38 may monitor a single receiving pipe 18, or, a group of receiving pipes 18, as much is required and according to design needs.

In a case where there is absolutely no light within the underground tunnel 40, in order to pass the detection envelope 42 created by the multitude of spaced apart receiving pipes 18, the digger has to pass through at least one receiving pipe 18, and, therefore, break the metallic conductors 26 within the receiving pipe 18. Now, in the next time when the LED 22 will be tested, it will not lit since the supply voltage thereto was interrupted, by a breakage of one of the metallic conductors 26 or both, hence, the control unit will sense the fault and will initiate an alarm.

Furthermore, in a case where the excavation is done in a complete darkness, which is an un-realistic possibility, and, in a case where the excavator manages to bent aside a receiving pipe 18 without breaking any one of the metallic conductors 26, a situation that is practically impossible, in this case, a part of the light created by the LED 22 during its next check will "leak" from the receiving pipe 18, i.e., will illuminate a part of the newly exposed underground tunnel 40. Since not the entire light intensity of the LED 22 is sensed by the CCD sensor 36, the control unit 38 will read a different measure and, accordingly, will generate an alarm.

Thus, as shown and explained, the system 10 for detecting underground tunnels 40 according to the present invention is multi functional, and, efficiently and effectively prevents, through on-line detection, crossing of the detection envelope 42 by hostile forces. According to some embodiments, a horoscope camera (not shown) may be inserted within each or some of the receiving pipes 18. This feature increases the feedback that is received from a given receiving pipe 18 and gives an option to have visual indication.

If it is desired, additional sensing units may be inserted into each or some of the receiving pipes 18. The additional sensing units may include, and not limited to, sound sensors, motion sensors, and vibration sensors. Thus, the system 10 for detecting underground tunnels 40 according to the present invention is regarded as a multiple sensoring system. In order to place a receiving pipe 18 in its location, a leading pipe 66 may be drilled first according to methods known in the art to form a pipe cavity 68 as shown in Fig. 3. Typically, the drilling diameter 70 is of 1" or 25.4mm. When the soil is sandy and there are no rocks involved, it may be practical to place the leading pipe by insertion or penetration techniques known in the art. The leading pipe 66 may have a unitary construction, i.e., be formed from a single piece. Alternatively, the leading pipe 66 may be formed from discrete portions that are connected to each other. The discrete portions may be connected to each other prior to being inserted into ground, or, during the process of insertion into ground.

According to some methods, the receiving pipe 18 is inserted into the leading pipe 66 up to the desired detecting depth 20 and then the leading pipe 66 is pulled out, i.e., in an upward direction 72, thus leaving the receiving pipe 18 in the required position. Alternatively, if the ground conditions permit, the leading pipe 66 is pulled out and, immediately after, the receiving pipe 18 is inserted into the hole left by the leading pipe 66.

According to other methods, the leading pipe 66 is perforated and is formed with an array of through holes 74 or through slots 76, as shown in Figs. 4 and 5, respectively. In this case, after the leading pipe 66 got to the desired detecting depth 20, the leading pipe 66 is left in its position, and the receiving pipe 18 is inserted into the leading pipe 66. Now, in a case that a tunnel front portion 62 of a newly digged underground tunnel 40 meets the leading pipe 66, the light within the underground tunnel 40 passes through the through holes 74 or the through slots 76 into the transparent receiving pipe 18 and captured by the CCD sensor 36 as described above. Although the present invention has been described to a certain degree of particularity, it should be understood that various alterations and modifications could be made without departing from the spirit or scope of the invention as hereinafter claimed.

For example, despite the fact that it may be less practical and more expensive, the receiving pipe may me formed from glass.

Furthermore, if desired, the receiving pipe may me formed from discrete elements that are connected therebetween so as to form a continuous transparent path.

Claims

CLAIMS:

1. A system for detecting underground tunnels (10), the system comprises: a multitude of transparent receiving pipes (18) positioned in the ground (12), each of the receiving pipes having a pipe upper end (28),

a light sensor (36) positioned at the pipe upper end of each of the receiving pipes,

a control unit (38) connected with each of the light sensors, wherein: when a receiving pipe (18) is exposed to light from an underground tunnel (40), the light sensor (36) senses the existence of light and passes a received signal to the control unit (38), and the control unit processes the received signal and activates a warning signal.

2. The system (10) according to claim 1, wherein:

the receiving pipes (18) are positioned vertically.

3. The system (10) according to claim 1, wherein:

the receiving pipes (18) are positioned along a detection envelope (42).

4. The system (10) according to claim 1, wherein:

the receiving pipes (18) are spaced apart a pipe spacing (48) of less than lm.

5. The system (10) according to claim 4, wherein:

the pipe spacing (48) between the receiving pipes is 0.5m.

6. The system (10) according to claim 1, wherein:

the light sensor is a CCD sensor (36).

7. The system (10) according to claim 1, wherein:

the light sensor (36) is capable of sensing very small luminous intensity.

8. The system (10) according to claim 1, wherein:

the control unit (38) monitors a multitude of receiving pipes (18).

9. The system (10) according to claim 1, wherein:

each of the receiving pipes (18) is placed within a perforated leading pipe

(66).

10. The system (10) according to claim 1, wherein:

each of the receiving pipes (18) has a pipe bottom (24) and is provided with an illumination element (22), located at the pipe bottom and wired by metallic conductors (26) to the control unit.

11. The system (10) according to claim 10, wherein:

the illumination element constitutes a LED (22).

12. The system (10) according to claim 10, wherein:

each of the illumination elements (22) is periodically tested for light emitting,

the control unit (38) is calibrated to a given luminous intensity value received during the periodical testing, and

13. The system (10) according to claim 1, wherein:

at least one of the receiving pipes (18) is provided with a horoscope camera therein.

14. The system (10) according to claim 1, wherein:

at least one of the receiving pipes (18) is provided with an at least one additional sensing unit therein.

15. The system (10) according to claim 14, wherein:

the additional sensing unit comprises one or more sensors from the groups of: sound sensors, motion sensors, vibration sensors.

16. The system (10) according to claim 1, wherein:

each of the receiving pipes (18) is placed within a hole having a drilling diameter (70) of 1" or 25.4mm.

17. A process for detecting underground tunnels (40), the process comprising the steps of:

a. Placing a multitude of transparent receiving pipes (18) in the ground (12), each of the receiving pipes having a pipe upper end (28).

b. Positioning a light sensor (36) at the pipe upper end of each of the

receiving pipes.

c. Connecting each of the light sensors to a control unit (38).

d. When a receiving pipe (18) is exposed to a light from an underground tunnel (40), the light sensor (36) senses the existence of light and passes a received signal to the control unit, and the control unit processes the received signal and activates a warning signal.

18. The process according to claim 17, further comprising the steps of:

e. Providing an illumination element (22) within a pipe bottom (24) of each of the receiving pipes (18), the illumination element being connected to the control unit (38) by means of metallic conductors (26). f. Periodically testing each of the illumination elements.

g. Calibrating the control unit to a given luminous intensity value received during the periodical testing.

h. Activating a warning signal by the control unit in a case of mismatch between the given luminous intensity value and the measured luminous intensity value.

19. The process according to claim 18, further comprising the step of:

1- Providing a horoscope camera within at least one of the receiving pipes (18).

20. The process according to claim 18, further comprising the step of:

1- Providing at least one of the receiving pipes (18) with an at least one additional sensing unit therein, the sensing unit comprises one or more sensors from the groups of: sound sensors, motion sensors, vibration sensors.

21. The process according to claim 18, further comprising the step of:

1- Placing each of the receiving pipes (18) within a perforated leading pipe (66).