Known impact absorbing structures are usually provided as solid edifices that are positioned around objects that are to be protected from the effects of an impact such as blast. These structures are often provided as a solid wall (or walls) that forms a physical barrier between the object and the source of potential damage. The body of the structure absorbs the impact, which often results in at least part of the structure being damaged. Other impact/blast absorbing structures that could be used may be provided as semi-rigid walls formed from containers filled with, for example, water or even gabion walls having rocks contained within a metal cage. These semi-rigid walls again provide a physical barrier against the shock of an impact but there is a degree of give in the wall to allow it to move when met by shockwaves resulting from the impact.

However, for all these known arrangements, the impact absorbing structures are in the form of barriers that is designed to physically absorb shocks rather than providing a structure having the facility whereby the shock of an impact can be dissipated or channelled in a direction whereby less harm could occur to a structure, for example, should the protective structure be breached.

According to the present invention, there is provided an impact absorbing structure comprising a structure having at least one surface including inlet apertures in said surface, the apertures leading to channels within the structure,

such that shock waves reaching said apertures pass along said channels, thereby directing the movement of said shock waves through at least part of said structure.

Preferably the impact absorbing structure is provided as a solid body having one or more apertures on one surface of the structure which lead to channels running through said structure to corresponding aperture (s) on a second surface of said structure. Such an arrangement allows blast to be directed right through the body of the blast absorbing structure. However, it is envisaged that the channels may only pass part way through the structure such that the shock of the impact is contained within the body of the structure but in a controlled manner.

Further, the impact absorbing structure may be a semi rigid structure, for example a reinforced water-containing sac, which has reinforced areas to protect against damage by an impact but which has channels through its body to channel the effect of the impact. A water-filled structure could be filled on site.

It is envisaged that the individual impact absorbing structures may have projections on one or more surfaces, which can be positioned in corresponding apertures in a surface of an adjacent structure.

Preferably, an aperture in a surface of an impact absorbing structure is in the form of a slot. By having a slot arrangement, this allows'for movement of adjacent impact absorbing structures relative to one another when impact occurs by allowing a projection on one structure to slide along the slot of a second structure from one position to another.

Further, it may be that the channels within the body of the structures may

have or include a filler, for example a foam material or other impact absorbing material which can assist in damping down the effect of shock waves passing through the impact absorbing structure. Further, the filler may include flame retardant materials to avoid the risk of flammable material or indeed ignited material or flames passing through the structure and possibly damaging material or persons to be protected.

The channels within the impact absorbing structure may be in the form of linear channels passing through the structure. However, irregular shaped channels may be used, for example curved or channels that have a series of directional changes. By having irregular channelling of shock waves, the effect of an impact can be further reduced due to such waves impacting on surfaces within the channels, which helps absorb shock waves gradually as they pass through the structure and thereafter direct the shock waves e. g. upwardly.

In a further embodiment of the invention, one or more impact absorbing structures are positioned adjacent other impact absorbing structures to build a wall of said structures.

It is envisaged that the wall comprises a plurality of impact absorbing structures positioned one on top of the other such that a side of the wall away from the possible impact is in a stepped arrangement with the base of the wall being wider than the top of the wall.

The stepped arrangement may be provided by there being more impact absorbing structures at the base of the wall, or alternatively the impact absorbing structures at the base of the wall are wider than those at the top of the wall. If several impact absorbing structures are positioned adjacent one another to form

one layer or course of the wall, the structures are positioned such that apertures in adjacent walls line up so that a channel is formed to run between a series of impact absorbing structures.

Preferably, when a wall having a stepped arrangement of impact absorbing structures is formed, the upper surface of one or more exposed steps of the wall reveals an aperture through which shock waves from an impact may exit the impact absorbing structures. It is preferred that the aperture through which the shock waves exit the impact absorbing structure or wall made from such structures lead from a common channel fed from a series of channels passing through said structure. The channels feeding the common channel are preferably from one layer of the wall but it is envisaged that channels may lead from one layer to another to feed a common channel.

It is further envisaged that individual blocks may have slots whereby rods or plates may be inserted in the blast protection structure so that channels within an individual block can be closed so that the direction of blast through a block . may be varied.

It is also preferred that individual impact absorbing structures or parts of a wall formed from such structures have areas of reinforcing material such as carbon fibre protective layers.

Another embodiment of the invention is directed to a method of building an impact absorbing wall whereby impact absorbing structures are built to form a wall, at least one side of which is stepped, with the wall being assembled such that channels running through the wall direct blast from a first side of the wall closest to the impact to a second side of the wall away from the blast, with the

second side of the wall being built in a stepped arrangement such that apertures on an upper surface of the step are revealed so that shock waves being channelled through the wall can escape through said apertures upwardly and away from the wall and from the structure to be protected.

In a preferred arrangement, the wall is built at an incline, with the wall being inclined towards the direction of impact/blast.

An embodiment of the invention will now be described, by way of example only, with reference to the accompanying drawings, in which: Figure 1 shows the front view of an impact absorbing wall structure formed of a series of blocks according to an embodiment of the invention, Figure 2 shows a side view of the wall structure of Figure 1 resting on an inclined surface, Figure 3 shows a side view of an individual impact absorbing structure having studs to allow attachment to adjacent impact absorbing structures, Figure 4 shows a plan view of an impact absorbing structure with slots for receiving the studs of Figure 3, Figure 5 shows a further embodiment of the invention with a wall of impact absorbing structures that can contain and/or deflect the shock of impact within the body of the wall and resting on an inclined surface, Figure 6 shows a plan view of channels within an impact absorbing structure used to build a wall as shown in figure 5, Figure 7 shows a plan view of various channel formations that can be used for the invention, and Figure 8 shows a schematic view of the effect that a wall formed of impact

absorbing structures according to the invention has on the control of shock waves from an explosion.

A wall incorporating a number of impact absorbing structures according to the invention is generally shown as 1 in Figure 1. Individual impact absorbing block structures 2 can have any number of apertures 3 on a surface or side, although preferably there is an even number of apertures on a surface to provide even control of the shock of an impact. As shown in the drawing, typically some structures 2 having eight apertures 3 are positioned next to larger structures 2 having sixteen apertures 3 so that they can be built up as would be done for building a standard wall of bricks.

As shown in Figure 2 the wall 1 can be built at an incline on e. g. a concrete pad or base 4 with the wall being tilted slightly towards the area of potential impact. The front 5 of the wall 1 faces the initial impact, while the rear 6 of the wall 1 is provided as a stepped structure.

Each layer of each block structure 2 of the rear 6 of the wall 1 ends in a step and the upper surface of each step has an aperture 6.

Each block structure 2 of the wall 1 has two apertured channels 7a and 7b passing through it. Although two channels 7a, 7b are shown, a single channel may be present or more than two channels. The channels 7a, 7b feed into a common outlet channel 7c at right angles thereto, which leads to a respective outlet aperture 8. The aperture (s) 8 allow shock waves that have passed from the front of the wall 5 towards the rear of the wall 6 via the channels 7a, 7b and 7c, to be directed upwardly out from the body of the wall. The channels 7a and 7b are arranged such that the shock waves will pass along the length of a layer

of the wall and then will be turned upwards by channel 7c. By having this controlled direction to the blast, the force of the blast can be released from the wall upwardly and away from any structures, which are in proximity to the rear 6 of the structure.

As shown in Figure 2, a single impact absorbing block structure forms one layer of the wall 1, the length of the structure 2 dictating whether it is placed at the bottom or top of the wall but a single layer may be made of a series of smaller impact absorbing structures 2 which are bolted one to the other, end on end, so that channels in individual blocks are connected in order for blast to be directed through the series of blocks until it reaches an aperture in proximity to the rear of the wall.

Individual impact absorbing structures 2 can be secured to one another.

This may be by way of pins (not shown) holding individual blocks to one another or one or more anchor bolts 9 may be used. Such bolts will pass through substantially all of the impact absorbing structures to provide a common anchor point for the structure, with the anchor bolt or bolts in turn, being bolted or secured in foundations for the wall or bed rock under the wall.

As shown in Figures 3 and 4, the individual blast absorbing structures 2, (which may also be referred to as blocks) may be fitted one to another with either a slot and stud arrangement where studs 10 in one structure 2 are fitted into slots 11 of an adjacent structure 2. The studs 10 are on the underside of a structure 2, while slots 11 are on the upper surface of the adjacent structure 2. In addition the anchoring bolts 9 passing through the layers forming the whole structure maintain some rigidity, especially if the wall 1 is at an incline. It is

preferred that slots 11 are used because these allow for a degree of movement of the studs 10 within the wall 1 when an impact occurs. It is preferable to provide a wall 1 with a degree of give rather than providing a solid edifice, which may fracture under certain conditions.

Figure 5 shows an alternative embodiment of the invention, where rather that having outlet apertures 8 in an upper wall of each block structure 2, the channels 7a and 7b pass substantially through the block structures 2 and then terminate. The channels 7a, 7b and especially the ends of the channels in proximity to the rear of the wall 5 may have an impact absorbing filler to provide extra damping and control of blast.

The top most block structure 2 may include at the rear end thereof a lip 12 and may not include studs 10 slideable in the slots 11 in the block structure to immediately there below such that this particular block structure 2 can be made a greater length than the one immediately beneath, thereby to be more effective in mitigating against the effects of a blast.

As shown in Figure 6, again the slot and stud arrangement is used to secure adjacent structures to one another and/or to allow them to slide with respect to each other. The slot and stud arrangement is relied upon more in this embodiment to control blast in conjunction with the channels 7a and 7b because rather than releasing shockwaves through apertures 8 as in Figures 2 and 3, the wall takes the force of the impact but controls the force by allowing energy to be dissipated through the channels 7a and 7b as well as allowing movement of the block structures 2 forming the wall 1 by the stot 11 and pin/stud 10 arrangement.

Such an arrangement is especially useful where there may be a risk of fire so

that there is a reduced risk of flames being channelled through the wall.

Figure 7 shows the various types of channels A, B, C, D and E that may be used within the body of an individual impact absorbing structure or a wall made of series of such structures. A shaped channels pass directly through an individual impact absorbing structure. As shown by B, the channels may fall short of passing through the entire length of a impact absorbing structure. As shown by C, the channels, rather than extending along the entire length of the impact absorbing structure, may meet to form a"U"shape at the end of the structure 2. This U shaped end forms a baffle, which acts to reduce the effect of blast. In the case of shape D, the channels curve either across one another, with the channels remaining separate but forming convoluted channels to reduce the energy of the shock waves within the structure. Alternatively, the channels meet at various points so that shock waves meet and turbulence would be formed where the channels meet which can be used to control blast shock. A similar principle is shown by shape E, where rather then the shock waves being released from the structure, they are contained by the use of a looped channels arrangement.

Figure 8 shows a schematic view of the way that shock waves move when blast impact occurs. Shock waves radiate out from the point of blast and impact upon the front face 5 of a wall 1 formed of impact absorbing structures 2 of the invention. In this arrangement, both the front wall 5 and the rear wall 6 are stepped. The shock waves impacting on the wall pass through apertures on the front 5 of the wall 1 and are directed along chann@ls 7a, 7b and 7c. The channel 7c leads to outlet aperture 8 on the upper surface of a step forming a layer of the

wall. The shock waves are directed upwards from the wall by way of the placing of the apertures 8 so that the blast is directed away from individuals or the object that is being protected.

It is envisaged that various parameters of the wall may be adapted in accordance with the potential blast threat that may be encountered. For example, the height of the wall may be modified or the depth (width) of the wall may be varied for example if a greater impact is expected. The weight of the material making up the impact absorbing structure may be varied, for example if concrete blocks are used, then there may be layers within the blocks of a heavier material at the base of the blocks to maintain a low centre of gravity for each block, or possibly parts of the blocks may be covered with a protective material such as Kevlar (g) to provide further protection against impact/blast.

Further, depending on the dynamics of the expected blast and the shockwave produced, the angle of the wall and how it leans towards the blast may be varied or alternatively, the wall may even be substantially upright. Also, the types of inlet apertures and the types of channels running through the wall may be selected according to the type of impact expected to be encountered. For example, one or two large apertures may be used for certain types of blast or alternatively, the wall could have a front surface covered with a series of much smaller apertures with possibly the channels within the wall getting wider as the channel passes through the wall so that the blast is dissipated with different types of dynamics depending upon the type of blast produced. Further, although the impact absorbing structures of the invention are particularly suited to impacts resulting from blast from explosions, it is also envisaged that the structures could

be used to control impacts from, for example, ammunition or solid objects that have been propelled or driven at a wall formed of such structures.

It is to be understood that the above detailed description is an embodiment of the invention and is provided by way of example only. Various details of the invention may be modified without departure from the true spirit and scope of the invention.