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Title:
SECURITY BARRIER
Document Type and Number:
WIPO Patent Application WO/2013/021189
Kind Code:
A1
Abstract:
A security barrier (10) comprises a first fence (20) and a second fence (40). The first fence comprises a first series of posts (22) and the second fence comprises a second series of posts (42). The first and second fences are provided adjacent to each other with the first fence being coupled below ground level with a the second fence. A footing having first and second post sockets is also provided for receiving a first post from each of the first and second fences respectively.

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Inventors:
SHARP, Graham (Hill & Smith Limited, Springvale Business & Industrial ParkBilston, Wolverhampton WV14 0QL, GB)
BOX, Simon (Hill & Smith Limited, Springvale Business & Industrial ParkBilston, Wolverhampton WV14 0QL, GB)
Application Number:
GB2012/051904
Publication Date:
February 14, 2013
Filing Date:
August 06, 2012
Export Citation:
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Assignee:
HILL & SMITH LIMITED (Springvale Business & Industrial Park, Bilston, Wolverhampton WV14 0QL, GB)
SHARP, Graham (Hill & Smith Limited, Springvale Business & Industrial ParkBilston, Wolverhampton WV14 0QL, GB)
BOX, Simon (Hill & Smith Limited, Springvale Business & Industrial ParkBilston, Wolverhampton WV14 0QL, GB)
International Classes:
E01F15/04; E01F15/06; E04H12/22; E04H17/22
Foreign References:
DE4207104A1
EP1283304A2
GB2447783A
US4673166A
DE202007003263U1
GB2447783A
Attorney, Agent or Firm:
HACKETT, Sean (Marks & Clerk LLP, Alpha TowerSuffolk Street Queensway, Birmingham B1 1TT, GB)
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Claims:
A security barrier comprising a first fence and a second fence, the first fence comprising a first series of posts and the second fence comprising a second series of posts, the first and second fences being provided adjacent to each other with the first fence being coupled below ground level with the second fence;

wherein the barrier further comprises a footing having a first post socket for receiving a first post from the first fence and a second post socket for receiving a first post from the second fence.

The barrier of claim 1 , wherein the coupling between the first and second fences is provided between the first post socket and the second post socket.

The barrier of claim 1 or claim 2, wherein said footing is formed of concrete. The barrier of any preceding claim, wherein the first post socket and/or the second post socket is a liner provided within the footing.

The barrier of any preceding claim, wherein the first and second post sockets are of different dimensions.

The barrier of any preceding claim, further comprising connecting means for connecting the first post of the first fence with the first post of the second fence within said footing.

The barrier of claim 6, wherein the connecting means comprise one or more bolts connecting the first and second posts.

The barrier of any preceding claim, further comprising a spacing means for separating the first post socket from the second post socket within the footing.

The barrier of any preceding claim, wherein the first posts of said first and second fences are separated by a distance of between 2 and 10cm.

The barrier of any preceding claim, wherein the first posts of said first and second fences are separated by a distance of 5.5cm.

The barrier of any preceding claim, comprising a plurality of footings, each for coupling the first fence with the second fence such that, over at least a portion of the barrier, the first and second fences extend substantially in the same direction as one another.

12. The barrier of claim 1 1 wherein the first fence is an anti-personnel fence configured to prevent access from personnel and the second fence is a vehicle mitigating fence configured to withstand an impact from a vehicle.

13. The barrier of claim 12, wherein the anti-personnel fence is situated with respect to the vehicle mitigating fence such that the anti-personnel fence will be impacted first in the event of an impact by a vehicle.

14. The barrier of any preceding claim, wherein the second fence comprises a plurality of wire ropes supported on said second series of posts.

15. The barrier of claim 14, wherein one or each end of the plurality of ropes terminate in a ground terminal.

16. The barrier of claim 15, wherein the last post in said second series of posts comprises means provided on or within said post for supporting said ropes.

17. The barrier of claim 16, wherein the ropes of the second fence enter the terminal from the end post at an angle that enables the separation of the first and second fences to remain substantially constant.

Description:
Security Barrier

This invention relates to security barriers and, in particular but not exclusively, to barriers that provide an effective perimeter protection against wilful intrusion into high security installations such as airports.

A known anti-vehicle barrier is described in the Applicant's co-pending patent application number GB2447783. This document discloses a perimeter security barrier for restraining a vehicle impacting the barrier from a direction substantially

perpendicular thereto or between 25 and 90 degrees relative to the barrier. The barrier comprises a plurality of wire ropes supported by a series of posts configured to restrain heavy impacting vehicles.

High security installations such as airports, defence installations etc are, however, not only prone to attacks by vehicles but also by pedestrians wishing to gain access thereto. The anti-vehicle fence discussed above would be ineffective against intrusion by persons who could simply climb over or through the wire ropes. Specialist anti-personnel fences, comprising panels of small mesh spacing, are known in the art that are resistant to cutting and climb-over.

The present invention has been devised with the problem of how to effectively protect against breaches by both persons and vehicles.

According to the present invention, there is provided a security barrier comprising a first fence and a second fence, the first fence comprising a first series of posts and the second fence comprising a second series of posts, the first and second fences being provided adjacent to each other with the first fence being coupled below ground level with the second fence, wherein the barrier further comprises a footing having a first post socket for receiving a first post from the first fence and a second post socket for receiving a first post from the second fence.

It is an advantage that two separate fences are used for the purpose of preventing access by both vehicles and persons since this avoids providing a single dual-purpose barrier that is more complex to manufacture and expensive to repair in the event of a vehicle impact or other damage. However, coupling the fences together underground provides the further advantage of strengthening the foundations of the barrier and therefore the barrier itself. It is a further advantage in providing sockets for each fence post as, in the event of damage to one of the fences, such as by a vehicle impact, the sockets allow easier and quicker repair of the damaged fence post and therefore the barrier. Furthermore, by providing both sockets in the same footing, the strength of the barrier footing is increased relative to providing separate footings for each socket. Manufacture of the footing for the barrier is also easier with a single footing. In an embodiment, the coupling between the first and second fences is provided between the first post socket and the second post socket. By coupling the fences in this way, the energy from any impact with one of the fences is at least partially insulated from the second fence. This is advantageous as it minimises the area of the barrier damaged thus minimising the area of any breach in the fence that may require guarding.

Preferably, the footing is formed of concrete. The first and second post sockets may be of different dimensions. Alternatively, the sockets may be of the same dimensions.

One or both post sockets may comprise separate inserts - e.g. a liner, preferably of metal - provided within correspondingly sized apertures within the footing. This enables easy replacement of the sockets and/or posts in the event of damage due to an impact. Alternatively, the posts may be fixed directly within the footing etc.

The common footing provided for posts of the first and second fences provides a secure foundation and adds strength to the barrier, which may be subjected to a high energy impact from an oncoming vehicle. The common footing also helps to dissipate energy from the impact through the posts to the footing and ground thus assists in arresting the vehicle.

In an embodiment, the barrier further comprises connecting means for connecting the first post of the first fence to the first post of the second fence below ground level. The connecting means may comprise one or more bolts connecting the first and second posts and/or sockets. This further strengthens the foundation and aids energy dissipation in the event of an impact by a vehicle.

In an embodiment the first and second sockets are separated by a spacing means. Preferably, the posts are separated by a distance of between 2 and 20cm. Preferably the separation is less than 10cm. Desirably, the first and second sockets are separated by a distance of 5.0 or 5.5cm. The two fences are preferably provided as close together as possible, just leaving space therebetween to allow maintenance access - e.g. for rope tensioning or replacement/re-hanging of ropes following an impact.

Mounting the two fences close together advantageously reduces the footprint required on the land. It furthermore facilitates maintenance of the surrounding land and/or environment as maximum access is provided to the land near the barrier without the need to interfere with the barrier itself (which may be dangerous due to the threat of attack of the installation). Furthermore, if the two fences were separated further with a 'no-man's land' therebetween, it would be visually more obtrusive.

In a preferred embodiment the barrier comprises a plurality of footings, each for coupling a first fence with a second fence such that the first and second fences extend substantially in the same direction as one another.

The first fence may be an anti-personnel fence configured to prevent access from pedestrian intruders and the second fence may be a vehicle mitigating fence configured to withstand and absorb energy from an impact by a vehicle. Preferably, the anti-personnel fence is disposed with respect to the vehicle mitigating fence such that the anti-personnel fence will be impacted first by an oncoming vehicle. The vehicle mitigating fence is thus provided on the opposite side of the barrier (i.e. the side immediately adjacent the area to be protected). This arrangement helps to minimise the damage to the barrier as collapse of the anti-personnel fence into the vehicle mitigating fence has less of an effect on the vehicle mitigating fence than if the vehicle mitigating fence was disposed on the impact side of the barrier with the antipersonnel fence being provided on the installation side thereof. Mounting the two fences close together advantageously controls damage to the antipersonnel fence since, in the event of a vehicle impact, the vehicle engages with the anti-personnel fence first and then with the vehicle mitigating fence shortly thereafter. The closeness of the fences and the effectiveness of the vehicle mitigating fence in arresting the vehicle means that minimal damage to the anti-personnel fence occurs. If the anti-personnel fence were provided at a greater distance from the vehicle mitigating fence, it would be more susceptible to damage over a greater length since it is inherently not as strong or resistant to damage as the vehicle mitigating fence. If the two fences were separated at a distance approximately equal to or less than the height of the anti-personnel fence, a vehicle impacting the anti-personnel fence could force it down onto the vehicle mitigating fence such that the former acts as a ramp for a vehicle to breach the latter.

Alternatively, the vehicle mitigating fence is disposed on the impact side of the barrier with the antipersonnel fence being provided on the installation side thereof.

In an embodiment, the vehicle mitigating fence comprises a plurality of wire ropes supported by the second series of posts, and the anti-personnel fence comprises a series of meshed panels supported on the first series of posts. This advantageously allows a clear line of sight through the fence, enabling visual security checks to be performed. The vehicle mitigating fence may comprise one or more ropes woven with respect to the posts and/or one or more unwoven ropes disposed on one side of the series of posts. One or each end of the plurality of ropes of the vehicle mitigating fence may terminate in a terminal, preferably a terminal provided on or in the ground. The last post in the series of posts of the vehicle mitigating fence may comprise means on or within the post for supporting the ropes. It is preferable for the ropes to enter the terminal from the end post at an angle that enables the separation of the vehicle mitigating fence and the anti-personnel fence to remain substantially constant. That is to say, even though a terminal for receiving the ends of the ropes of the vehicle mitigating fence is provided, this does not alter the line of the anti-vehicle or antipersonnel fence and no interruption or deviation thereof is required. It is a further advantage that, in the event of an impact to the combined barrier, the damage to the anti-personnel fence is localised such as to only affect a single or a small number of panels. Panels away from the vicinity of the impact remain intact or at least in a condition to withstand further impacts. The vehicle mitigating fence also remains in place with only a small number of posts in the area local to the impact itself being bent/deformed. The combined fence thus remains operable allowing time for repairs to be made thereto whilst still providing a good degree of security.

In another aspect, a post footing for use with a security barrier is provided, as described above.

Figure 1 shows a perspective view of a security barrier according to an embodiment of the invention;

Figures 2a to 2c show front elevational views of sections of the security barrier according to an embodiment of the invention;

Figures 3a and 3b are end views of the security barrier of Figures 2a to 2c;

Figure 4a is a top plan view of an end post and terminal according to an embodiment of the invention;

Figure 4b is a top plan view of an end post and terminal according to another embodiment of the invention;

Figure 4c is a top plan view of an end post and terminal according to a further embodiment of the invention;

Figure 5a is a front perspective view of the end post of the embodiment of Figure 4a;

Figure 5b is a rear perspective view of an end post;

Figures 6 to 8 show the security barrier of Figure 1 before and after an impact by a vehicle.

Figure 1 shows a security barrier 10. The barrier 10 comprises a vehicle mitigating fence 20 for protecting an installation (not shown) against otherwise penetrative vehicular attacks. The barrier 10 further comprises an anti-personnel fence 40 designed to keep pedestrian intruders out of the installation.

The anti-vehicle fence 20, e.g. Bristorm ® manufactured by Hill & Smith Limited, is intended to restrain heavy vehicles impacting from a direction that is substantially perpendicular, or at an angle of between 25 and 90 degrees, to the line of the barrier. Breach of the barrier by a heavy goods vehicle in the order of 7500 kg inertial mass impacting the barrier at speeds of about 64-80 km/hr is prevented. The vehicle mitigating fence 20 comprises a series of posts 22 mounted in the ground. A plurality of ropes 24 are supported on the posts 22. The ropes 24 may be plastic coated, high tensile steel ropes or cables that are pre-tensioned between the posts 22. The ropes 24 may be disposed at a height of between 300 mm and 2 metres above the ground. The height position of at least some of the ropes 24 is selected to be such that the engine of an impacting vehicle will impact them. Ropes 24 may be provided at varying heights above the ground, for absorbing energy from a range of vehicles of varying sizes.

In the embodiment of Figures 1 , 2a-c, 3a and 5a-8, a pair of wire ropes 24a, 24b is provided at or approximately at the midpoint of the posts 22 (i.e. approximately halfway from the ground level to the top of the posts 22). The ropes 24a, 24b are sinuously woven with respect to the posts such that a first rope 24a of the pair passes on a first side of a first post 22, and on an opposite, second side of an adjacent post 22, and so on. The second rope 24b of the pair passes on a corresponding second side of the first post 22, and on a first side of the adjacent post, etc. An additional rope 24c is sinuously woven between the posts 22 at a vertical position lower than the rope pair 24a, 24b, and a further rope 24d is sinuously woven between the posts 22 at a vertical position higher than the rope pair 24a, 24b. These additional ropes 24c, 24d are oppositely woven with respect to each other such that one passes on a first side of one post and the other passes on the opposite, second side thereof. A further rope 24e is provided within a slot 26 in the top of the posts 22. Other configurations are envisaged, e.g. a different combination of woven and unwoven ropes, or with further woven rope pairs or additional woven or unwoven ropes.

As shown in Figures 1 , 3a and 5b, the ropes 24 are supported on the posts 22 using one or more hooks 28 e.g. formed/angled from a stainless steel bar and fixed within corresponding apertures provided within the posts 22 e.g. with bolts. The design parameters of the barrier are such that, on impact, the intermediate posts are pushed back to incline away from the impact direction by up to 40 degrees. The angle of the hook 28 is such that the ropes 24 will tend to separate from the hook 28 when the posts 22 are pushed back during impact. The intermediate posts may be inclined relative to the vertical towards the predetermined direction, that is, towards the oncoming vehicle. The inclination of the intermediate post(s) to the vertical may be between 0 and 45 degrees, preferably between 0 and 20 degrees, and more preferably 10 degrees. The barrier 10 may be provided as a perimeter security barrier - i.e. extending around and enclosing an installation, or a length thereof may be provided to e.g. span the distance between two buildings, walls or other solid structures.

Referring to Figures 4a-c and 5a-b, at an end of the vehicle mitigating fence 20, the ropes 24 pass around, or are supported by an end post 30. The end post 30 is vertical and anchored in the ground. A rope support device is provided on the end post 30. In the embodiment of Figure 5b, the rope support device is a tab 31 welded or integrally formed with the post 30. One or more apertures 31 a are provided within the tab 31 for receiving one or more ropes 24. In the embodiment shown in Figure 5b, each of the five ropes 24 pass through and are thus supported by a separate tab aperture 31 a. In alternative embodiments (not shown), the ropes may be supported by other means e.g. apertures or grooves/notches provided directly within the post 30, or hooks or provided on the post 30. The ropes 24 are anchored at each end thereof and terminate in a rope terminal

32. In the embodiments of Figures 4a, 4b, 4c and 5a, the terminal 32 is provided on or in the ground. The ground terminal 32 may be in the form of bolts or another suitable mechanical rope gripping device. The terminal 32 also holds the ropes in tension. The ropes may be tensioned after hanging on the posts 22, and the terminal 32 then acts to maintain the tension therein. A load or energy-absorbing device (not shown) may be provided between respective ends of the ropes 24 and the posts 30/terminal 32. This device may be in the form of a hot rolled channel section or hollow tube that is configured to absorb energy transmitted from the impacting vehicle by the ropes. The energy-absorption means is designed to deform under the increased tension load in the ropes during impact by a vehicle. This limits the peak rope loads to tolerable levels and restrains the ropes in order that they develop tension to resist penetration or breach of the barrier by the impacting vehicle.

In the embodiment shown in Figure 4a, the ropes pass around the end post 30 and are fed into the terminal 32 at an angle that is, generally speaking, approximately equal to or slightly greater than 90° relative to the initial direction of the fences 20, 40. The ropes 24 pass through tab apertures 31 a as described above. Figure 4a shows an example of termination of the vehicle mitigating fence 20 earlier than the anti-personnel fence 40.

Figure 4b shows an alternative embodiment wherein two runs of vehicle- mitigating fence 20, 20' are terminated using a common end post 30. The ropes 24 of a first vehicle mitigating fence 20 pass around the end post 30 as described above and terminate in a terminal 32. The ropes 24' of a second vehicle mitigating fence 20' pass around the end post 30 as described above and terminate in a second terminal 32'. The ropes 24, 24' pass through tab apertures 31 a as described above. Separate or common apertures 31 a may be provided for the ropes of each of the two fences 20, 20'. In each of the embodiments of Figures 4a and 4b, the terminals 32 are inset from the line of the barrier 10 a little such that the ropes 24 of the vehicle mitigating fence 20, 20' enter the terminals 32, 32' at an angle slightly greater than 90° relative to the original direction of the fence 20. This enables the vehicle mitigating fence 20, 20' and the anti-personnel fence 40 to be situated close together, at substantially the same separation along the length of the barrier 10 (apart from in the vicinity of where the ropes 24 pass around the end post 30 - as can be seen in Figures 4a, 4b). In the embodiments of Figures 4a and 4b, this enables the barrier 10 to be provided with a 90° change of direction. If the terminals 32, 32' were provided at 90° to the original line of the vehicle mitigating fence 20, this would necessitate a change in the line of the anti-personnel fence 20 e.g. by flaring it out around the terminals 32. Similarly, in some known wire rope barriers used for other purposes, the ropes thereof terminate in the end post itself (i.e. a ground terminal is not used) which, if incorporated in embodiments of the present invention, would also require flaring out of an adjacent anti-personnel fence. It will also be appreciated that the terminals 32, 32' could be provided at different locations in order to provide a different change of angle (i.e. other than 90°) at which lengths of vehicle mitigating fence 20, 20' are provided. Posts similar to the end posts 30 shown in Figures 4a and 5a could also be utilised in directing the ropes 24 of a single fence 20 to continue at a different angle - 90° or otherwise - e.g. as would be required if the barrier 10 is employed as a perimeter barrier.

Figure 4c shows an alternative embodiment wherein termination of two runs of vehicle mitigating fence 20, 20' is required without any change of angle. Again, the ropes 24, 24' pass through tab apertures 31 a on the post 30 and exit at an angle to terminate in respective terminals 32, 32' such that the vehicle mitigating fences 20, 20' are provided substantially in line with each other with no change of angle therebetween. This enables the vehicle mitigating fence 20, 20' to run substantially in a straight line parallel to the anti-personnel fence 40.

The fences 20, 40 are thus arranged to extend substantially in the same direction as one another and, when a change in direction is required they remain close together and continue to extend in substantially the same direction after the change in angle. The fences 20, 40 may run in a straight line, approximately parallel to one another, at least over a length thereof. Depending on the nature of the installation to be protected, the fences 20, 40 may be required to change direction at certain locations along the length thereof. The ropes 24 can be anchored at any angle relative to the original direction of a length of fence 20, or in line therewith, depending on the site topography and/or installation requirements. The fences 20, 40 may also be terminated in different locations. This provides flexibility to protect a variety of areas of land/installations.

The anti-personnel fence 40, e.g. Secureguard™ provided by Barkers Fencing, provides protection against wilful intrusion by people and is designed to mitigate against intruders climbing over and cutting through the fence. A series of posts 42 are mounted in the ground. A plurality of mesh panels 44 are secured to the posts 42 e.g. with tamper-proof bolts 45 (shown in Figure 3b). Alternatively, the anti-personnel fence may be of the chain link or palisade type. The mesh size is small (e.g. 75mm x 12.5mm produced with 4.00mm +/- 0.10mm wire). The posts 42 are taller than those 22 of the anti-vehicle fence 20, e.g. by approximately a factor of 2, such that the anti- personnel fence 40 extends vertically beyond the vehicle mitigating fence 20. The antipersonnel fence 40 is required to be tall in order to keep intruders out of the installation. The anti-personnel fence can be provided with or without strainer posts 46 e.g. as shown in Figures 4b, 4c. In an embodiment, strainer posts are used at corners and intermediate posts of the anti-personnel fence 40 where tensioned line wires are used to support the mesh (not shown). The strainer post has a "leg" bolted to the side of the post at an angle of about 45 degrees.

The vehicle mitigating fence 20 and the anti-personnel fence 40 are mounted in the ground in close proximity to one another. Typically, the minimum spacing required therebetween is determined by the diameter of the rope 24 plus space to allow access for installing/rehanging ropes etc. A typical rope diameter used is 15.7mm (excluding the plastic coating that is preferably provided on the rope). Based on this, plus a small margin for tolerances plus allowing space for fitting/maintenance access, the gap between adjacent faces on the posts 22, 42 may be within approximately 2-15cm, and preferably substantially at a separation of 5.5cm. Larger spacings e.g. 20cm or more are envisaged, but this would compromise the benefit of the barrier 10 occupying only a small footprint on the land. This spacing allows for the fitting or removal of one of the ropes 24 without the need to dismantle the entire fence 20. This is particularly important when repairing the barrier 10 following an impact.

Referring again to Figures 3a and 3b, the vehicle mitigating fence 20 and the anti-personnel fence 40 are mounted in the ground in a common footing or foundation 50. The footing 50 is provided entirely within the ground. A first channel 52 is sized to receive the lower end of post 22 of the anti-vehicle fence 20. A second channel 54 is sized to receive the lower end of post 42 of the anti-intruder fence 40. In the embodiment shown, the channel 52 for the vehicle mitigating barrier post 22 is wider and shallower than the channel 54 for the anti-personnel barrier post 42. It will, however, be appreciated that each channel 52, 54 may be of any width, depth and height to accommodate different sized posts 22, 42.

Figure 3b shows the footing 50 and details of how the ends of the posts 22, 42 are provided therein. A socket 53a is provided within the channel 52, the end of the post 22 being received therein. A similar socket 53b is provided within the channel 54 with the end of post 42 being received therein. Each socket 53a, 53b is a metal insert or sleeve corresponding in size externally to the internal dimensions of the channels 52, 54. The internal size of the socket 53a, 53b correspond to the external dimensions of the end of the posts 22, 42. The depth of the sockets 53a, 53b define the height of the posts 22, 42 of the vehicle-mitigating fence 20 and the anti-personnel fence 40 above ground and can vary from post to post and for different installations.

One or more spacer blocks 55 are provided within the footing 50 between the socket 53a for the vehicle-mitigating fence post 22 and the socket 53b for the antipersonnel fence post 42. In the embodiment shown, two spacer blocks 55 are provided, welded or otherwise secured to the anti-vehicle post socket 53a. The spacer blocks 55 can be of any size chosen to define the desired spacing between the posts 22, 42 - e.g. 5.5cm in width as discussed above. The socket 53b for the antipersonnel fence post 42 is provided with one or more apertures (corresponding to the number of spacer blocks 55 being used) through which a bolt 57 is provided. The bolt 57 couples the socket 53b of the anti-personnel fence post 42 to the socket 53a and thus to the vehicle-mitigating fence post 22. Additionally, the anti-personnel fence post 42 is provided with one or more apertures corresponding to the apertures in the socket 53b. The bolt 57 can therefore pass through the apertures of the anti-personnel fence post 42 to couple the socket 53b and the anti-personnel fence post 42. The position of the apertures in the socket 53b, anti-personnel posts 42 and thus the position of the spacer blocks 55 can be chosen relative to the socket 53a for the post 22 of the vehicle-mitigating fence 20 to control the height of the anti-personnel fence 40 above the ground. It will be appreciated that the post 42 of the anti-personnel fence 40 could be provided in a sleeve (not shown) such that one or both posts 22, 42 are mounted in a sleeve in the footing 50. The spacer block 55 could be welded or bolted (for example) to either or both sleeves.

A footplate 56 may be provided on the base of one or each of the posts 22, 42. The footplate 56 helps to secure the post 22, 42 in the footing 50, especially since the post 22, 42 may be subject to a high-energy impact from a colliding vehicle.

The two fences 20, 40 are thus coupled together underground via the coupling between the sockets 53a, 53b but remain independent of each other above ground level. Preferably, the footing 50 is a concrete footing such that the ends of the posts 22, 42 are embedded within the concrete. In order to erect the barrier 10, the coupled sockets 53a, 53b and antipersonnel fence post 42 are positioned and suspended within a hole in the ground at the desired height within the hole (defined by the predetermined height of the sockets 53a, 53b). Concrete is then poured into the hole in order to secure the sockets 53a, 53b and post 42 therein. The mesh panels 44 are then attached to the posts 42 of the anti-personnel fence, and the ropes 24 are mounted on the posts 22 of the vehicle- mitigating fence 20, terminating at the end posts 30 and terminals 32. As can be seen in Figures 2, 4a, 4b and 4c a larger common footing 60 is provided in which an end post 30 and one or more adjacent fence posts 22, 22', 42 are mounted. The common footing 60, preferably concrete, can be of any size to accommodate the required number of posts 22, 22', 42, 60. The ground terminals 32, 32' can also be mounted on/within the footing 60.

Figure 6 shows a security fence 10 according to embodiments of the invention just prior to a collision by an oncoming vehicle. The fence 10 is constructed so that an impacting vehicle will first make contact with the anti-personnel fence 40, and then with the vehicle mitigating fence 20. As discussed above, the majority of the ropes 24 of the vehicle mitigating fence 20 are provided at a height that corresponds to the front / bumper of the vehicle. An impacting vehicle makes contact with the ropes 24 which push back on the posts 22. This transmits energy to the posts 22 adjacent to the impact zone, thereby spreading the impact load along the length of the fence 20. Impact energy is also dissipated through the posts into the common footing 50 and into the ground.

Figures 7 and 8 show the security barrier 10 after an impact has occurred. It can be seen that the posts 22 of the vehicle mitigating fence 20 in the vicinity of the impact have been bent or deformed, but are still standing with at least some of the ropes 24 being maintained in position with respect to the posts 22. Away from the impact zone, the posts 22 remain upright with the ropes 24 substantially in their original positions. Although damaged, the anti-vehicle fence 20 is still capable of withstanding further impacts from vehicles along its length, and especially away from the point of impact. Directly in the vicinity of the impact the panels 44 of the anti-personnel fence 40 have been damaged. The construction of the fence 40, whereby mesh panels 44 are bolted to the posts 42, means that in the event of an impact the panels 44 in the impact area are stripped from the posts 42, shown clearly in Figure 8. Since the fence 40 more easily succumbs to damage under impact, the degree of damage away from the point of impact is less such that only one, two or three panels 44 and posts 42 may be damaged. The remainder of the fence 40 remains substantially undamaged.

It is therefore easy and inexpensive to replace damaged panels 44 and posts 42, 22 in order to return the security barrier 10 to full containment.

Embodiments of the invention employ separate anti-personnel and anti-vehicle fences, independent above ground, which advantageously provide great flexibility in that the design can be adapted to match an existing perimeter or to provide whatever level of perimeter protection is desired.