CA3188111A1 - Structure for absorbing impact energy - Google Patents

Abstract

The structure for absorbing impact energy comprises a core (15) having a first surface (10) exposed to impacts, and reinforcements which are distributed inside the core (15) and have frictional interfaces with the core material. The reinforcements comprise first reinforcements (16) that are positioned in a first reinforced region (12) adjacent to the first surface (10) and have main directions of resistance forming an angle of less than 45° with the first surface.

Description

Description Title: Structure for absorbing impact energy Technical area [0ool] The invention relates to the field of protective structures against accidental impacts of massive objects, corresponding for example to falling rocks in the mountains, or the derailment of a train.
Prior technique

[0002] In order to protect roads or buildings from accidental impacts, two types of solutions are traditionally used.

[0003] First of all, we know the protective nets which are arranged way to intercept impacting objects. These nets, generally metals, can stop impacts of up to 8 megajoules (MJ) by deforming, and have the advantage of being compact. They put however many problems. These structures cannot be solicited several times and they require significant maintenance. After having stopped a projectile, the anchor points are damaged and it is necessary to make repairs. Maintaining these structures is costly and frequent. Maintenance is also required due to corrosion nets generally laid out in the open air. This constraint is all the more more important than these structures are usually located in hard-to-reach places. On the other hand, these unattractive structures tend to degrade landscapes. In many territories, the implementation protective nets are not enough to make land constructible exposed to falling objects, the trend being to safeguard landscapes.
These requirements are important in mountainous areas where the pressure land is growing.

[0004] Finally, these nets have a heterogeneous efficiency and cannot not absorb impacts to their full extent. For example, an impact on an anchor post is not absorbed properly.

[0005] In FR 3 083 551 Ai, such a protective net is associated with a merlon-type structure made up of significant embankments allowing completely block the impacts. These structures make it possible to absorb higher energies, up to 30 megajoules, and require maintenance weak. However, they occupy a large footprint, and are not still usable in practice.

[0006] The documents WO 2019/091508 A1 and WO 2017/077313 A1 describe gabions, i.e. metal cages filled with stones or sandbags, without necessarily seeking protection against powerful impacts. If such an impact nevertheless occurs, the elements metal parts of the cage are stressed in traction. You have to rely on the weak deformability of the stony content so that the damage caused is not not too significant, but the absorption of impact energy by the structure remains quite limited.

[0007] EP 1 520 933 Al describes a technique where facing elements such as gabions are arranged on the front face of a ground structure reinforced and associated with a deformable material, such as recycled tires.
Thus, in the event of stone impacts, damaged individual elements of the facing can be replaced.
Technical problem

[0008] There is therefore a need for an impact absorbing structure durable that can have a small footprint and good integration landscape.
Summary of the invention

[0009] The invention proposes a reinforced impact absorption structure allowing the energy of the impact to be distributed laterally in such a way as to allow decrease in the thickness of the structure. If the use of reinforcements is known, they are conventionally placed in the depth of an embankment, parallel to the direction in which it is expected to be requested.
Disclosure of Invention

[0010] The subject of the invention is an impact energy comprising a embankment having a first face exposed to impacts and reinforcements distributed inside the embankment and presenting interfaces frictional with the backfill material. Reinforcements include first reinforcements placed in a first reinforced region adjacent to the first face and having main directions of resistance forming an angle less than 45 with the first face.

[0011] The structure can be of the merlon type and arranged orthogonally to a trajectory along which impacts are anticipated so that the impact against which protection is sought occurs in a direction having a strong component normal to the first face. he can also be a retaining wall arranged in such a way as to avoid the subsidence of stepped terrain in response to a large impact.

[0012] The backfill is preferably made of earth but can also include any type of material capable of absorbing energy mechanics by interacting with the reinforcements. Preferably the backfill has a certain granularity which allows it to have a favorable mechanical behavior.

[0013] In one embodiment, suitable for example in sites where powerful impacts are likely to occur along directions opposite sides, the embankment has a second face opposite the first face. THE
reinforcements may then comprise second reinforcements placed in a second reinforced region adjacent to the second face and having principal directions of resistance forming an inferior angle at 45 with the second side.

[0014] The configuration of the absorption structure allows the friction mobilized at the level of the first (or second, if necessary) reinforcements have an important contribution to the dissipation of energy of a powerful impact occurring on the first (or second) side. This friction results from the deformation of the first (or second) face due to the impact. The location of the first (or second) reinforcements within of the first (or second) reinforced region, which is adjacent to the first (or second) face, and their orientation with respect to this face allows effective dissipation without requiring a great depth of penetration inside the structure. We can thus obtain a structure absorption whose size is not too large perpendicularly to faces likely to be struck by objects of kinetic energy high. The footprint is for example less than or equal to 10 m, preferably less than or equal to 5 m, more preferably less than or equal to 3 m.

[0015] The reinforcements used are preferably reinforcements of one-dimensional type, that is, the mechanical strength they present is exercised essentially in a single direction of resistance, the mechanical resistance they present in the other directions being negligible compared to it. These are, for example, bands, not tablecloths or extended grids. The main direction of resistance of the reinforcement corresponds to the direction in which the reinforcement tends to propagate mechanical stress when stressed. It's about generally in the direction of the largest dimension of the reinforcement.

[0016] These reinforcements are arranged so that their directions main resistors are substantially parallel to each other and to the Or the face(s) of the structure. The main directions of resistance of first reinforcements may be parallel to the first face of the backfill, and the same for the second face, if applicable. It is nevertheless possible, in some cases, that their orientation deviates a little from the plan of there first face, or of the tangent plane to this one if the first face is not plane. The angle formed between these principal directions and the first face must nevertheless remain at an acute angle so that their projection on the first face is longer than their projection in the direction perpendicular to the first face, which gives a good efficiency of energy dissipation in the event of impact in the perpendicular direction.

[0017] In the case of a non-flat face, reinforcements in the extension of each other could therefore, for example, form a polygon following the shape of the face. A curved face will have preferably a large radius of curvature.
5 [0018] The arrangement of the reinforcements perpendicular to the normal of the front face, and therefore to the direction of the impact which must be absorbed energy, distributes the mechanical energy of the impact laterally in order to to reduce the thickness of the stressed structure.
[0019] In order not to weaken the embankment by creating slip planes preferences, it is interesting to avoid as much as possible having the first reinforcements at the heart of it. This is the reason why we arranges the reinforcements mainly close to the face(s) of the the structure likely to receive impacts. This does not exclude the presence of reinforcements in the heart of the embankment but these will be minority. The distribution of reinforcements is heterogeneous in the thickness of the structure. The density of reinforcements is less important in regions far from the flush faces than in the first region reinforced (or the second reinforced region) of the embankment. It is medium and one could possibly find very locally exceptions due, for example, to construction irregularities or deformation of the structure which will cause several reinforcements and therefore a local increase in the density of these reinforcements: the density of reinforcements is not necessarily continuously decreasing. Preferably, the reinforcements are spaced regularly but only in reinforced regions close to least one side of the structure. There may be regions less close to the faces of the structure in which the reinforcements are more widely spaced or even absent. These regions may, however, contain other types of reinforcements, for example reinforcements oriented according to the thickness of the structure.

[0020] The characteristics which follow can, optionally, be put implemented. They can be implemented independently of each other.
others or in combination with each other:
- the first and/or second reinforcements are arranged horizontally;
- the first side of the embankment is covered with a facing. This facing can be of any type and can both improve the mechanical properties of the structure and its landscape integration, for example when it comes to a vegetated or mineral facing;
- secondary reinforcements are arranged transversely to the first side. These secondary reinforcements may present any orientation and can, for example, make it possible to strengthen the structure with respect to the forces it supports in a static regime, in the absence of impact. One can thus imagine reinforcements in zigzag connecting the front face and the back face or reinforcements oriented perpendicular to the front face and coming connecting the first and/or second reinforcements;
- the first reinforcements include reinforcements metal, or in polymeric material or reinforcements of geogrid or geotextile type.
- at least some of the first reinforcements are arranged in successive segments along their main direction of resistance, with areas of mutual overlap between the segments, from fill material may then be between the segments sequences of a first reinforcement, in the zones of recovery.
[0021] Typically, the structure is capable of absorbing an impact having an energy greater than 2 MJ, preferably greater than 5 MJ.
These energies correspond to constraints that can classically be subject to protective barriers arranged in the mountains, for example.

[0022] The dissipation of energy by friction is favored in order to maintain the performance of the structure. The arrangement of reinforcements is therefore preferably designed to limit as much as possible the failure of the reinforcements: the plurality of reinforcements comprises reinforcements arranged in such a way as to have a ductile behavior and not fragile when the front face is stressed by an impact in one direction normal.
[0023] An example of such an arrangement consists in limiting the connections direct between the reinforcements. Two reinforcements arranged in segments successive along their main direction of resistance are for example arranged with an area of mutual overlap between them, and leaving a layer of backfill material between the reinforcements, which allows to introduce friction and soften the transmission of lateral stress in order to avoid the breakage of the reinforcements. This overlapping area mutual is a function of the stiffness of the reinforcements, the surface of friction, the resistance of the reinforcement to rupture.
[0024] The largest dimension of the reinforcements can also be critical and it is important not to use too many reinforcements large dimension in order to prevent them from breaking, always with a view to resilience allowing the structure to sustain multiple impacts without require repair.
Brief description of the drawings [0025] Other characteristics, details and advantages of the invention appear on reading the detailed description below, and on analyzing of the attached drawings, on which:
Fig. 1 [0026] [Fig. 1] is a cross-sectional side view of a structure according to one mode of carrying out the invention;
Fig. 2 [0027] [Fig. 2] is a cross-sectional side view of a structure according to another embodiment of the invention;
Fig. 3 [0028] [Fig. 3] is a cross-sectional side view of a structure according to another embodiment of the invention;
Fig. 4 [0029] [Fig. 4] is a cross-sectional side view of a structure according to another embodiment of the invention;
Fig. 5 [0030] [Fig. 5] is a sectional front view of the structure, the section being along the plane VV indicated in any one of Figures 1 to 4;
Fig. 6 [0031] [Fig. 6] is a sectional top view of a structure according to the embodiment of the invention of Figure 3;
Fig. 7 [0032] [Fig. 7] is a sectional top view of a structure according to a another embodiment of the invention;
Fig. 8 [0033] [Fig. 8] is a view similar to that of figure 6 after an impact energy.
Description of embodiments [0034] The impact energy absorbing structure described below as example takes the form of a protective barricade used to intercept falling rocks that can weigh up to several hundred tons, for example near mountain roads. Such falling rocks can carry energies greater than 6 megajoules (MJ).

[0035] This protective barricade has a first face, or front face, represented on the right in FIGS. 1 to 4 and a second face, or face rear, 20 shown at left. These faces 10, 20 can be substantially parallel as in Figures 1 and 3. The rear face 20 can 5 also be inclined relative to the front face 10, as in Figures 2 And 4.
[0036] The orientation of the rear face 20 in Figures 2 and 4 allows a better dissipation of mechanical energy in the ground but increases the footprint of the work.
10 [0037] Although the front face 10 is shown vertical in the figures to 4, it can also be inclined, in particular if it is requested to increase the stability of the work, to modify the grip on the ground or to adapt to an impact trajectory that is anticipated to be oblique. It is indeed interesting that the front face is as perpendicular as possible to the trajectory of the impact.
[0038] The embankment of the exemplary embodiment comprises earthen fill 15 delimited by the front and rear faces 10, 20, in which are arranged reinforcements 16 having frictional interfaces with the backfill material. These reinforcements 16 are for example strips regularly distributed along the vertical direction and extending horizontally, parallel to the front face 10 and to the rear face 20, in a direction perpendicular to the cutting plane of Figures 1 to 4. This orientation makes it possible to preferentially distribute the mechanical energy of a impact laterally rather than in the thickness of the protective barricade.
[0039] The reinforcements 16 are arranged in the regions of the embankment 15 which are the most stressed in the event of an impact, the energy of which must be absorbed.
In embodiments according to Figures 1 and 2, the reinforcements 16 consist of first reinforcements 16 placed in a first reinforced region 12 adjacent to the front face 10. In those of Figures 3 and 4, in addition to the first reinforced region 12, a second reinforced region 22 is provided close to the rear face 20. This second region reinforcement 22 includes second reinforcements 16. In general, the central region of the merlon will not be provided with 16 parallel reinforcements to the faces 10, 20, so as to allow deformation of the merlon in the event impact, so as not to weaken it.
5 [0040] However, secondary reinforcements 18 arranged transversely to the faces 10, 20 can also be incorporated into the backfill 15, to consolidate the whole. Secondary reinforcements 18 can in particular connecting the front and rear faces 10, 20.
[0041] The reinforcements 16 can be arranged over the entire 10 width of the merlon. Advantageously, reinforcements 16 are used arranged in successive segments along their main direction of resistor so as to partially overlap as shown in Figure 5.

Each zone 25 of mutual overlap between two reinforcements 16 successive sections includes backfill material so that the reinforcements 16 are not in contact with each other. Thus, in the event of an impact, the energy is transmitted from one segment to the next by friction and dissipated gradually while avoiding causing the reinforcements to break 16. This can allow the merlon to withstand multiple impacts consecutive without requiring repair.
[0042] Ideally, the reinforcements 16 are arranged in such a way perfectly parallel to the front and rear faces as shown in the figure 6, so as to distribute the mechanical energy as laterally as possible.
However, for logistical reasons or in order to particularly strengthen certain portions of the merlon and/or to protect certain portions thereof, the reinforcements may have a slight angle (which must remain less than 45 ) and sink somewhat into the thickness of the structure, like shown in Figure 7. It is nevertheless considered that they are substantially parallel to the front face 10 and to the rear face 20 because their orientation stay mostly lateral. The main directions of resistance of reinforcements 16 form an angle less than 45 with face 10 and/or 20 backfill 15.

[0043] Similarly, the reinforcements 16 may have a variation in height and have a slight slope. it is desirable that this slope remains low so as to distribute the energy as laterally as possible.
[0044] Figure 8 is a representation similar to Figure 6 after what received a powerful and localized impact on its front face 10 shown in bottom of the figure. It can be seen that the energy has been well dissipated laterally thanks to the reinforcements 16. The reinforcements 16 have no broken. They remain arranged in a configuration capable of damping other impacts.
The invention is not limited to the examples described above. She encompasses all the variants that a person skilled in the art may consider in the scope of the protection sought.

Claims

Claims [Claim 1] An impact energy absorbing structure, comprising:
an embankment (15) having a first face (10) exposed to impacts; And reinforcements distributed inside the embankment (15) and having frictional interfaces with the backfill material, wherein the reinforcements include first reinforcements (16) placed in a first reinforced region (12) adjacent to the first face (10) and having main directions of resistance forming an angle less than 45 with the first side.
[Claim 2] A structure according to claim 1, wherein the directions main resistance of the first reinforcements (16) are parallel to the first side of the embankment (15).
[Claim 3] Structure according to any one of the claims previous ones, in which the embankment (15) has a second face (20) opposite to there first face (10), and in which the reinforcements comprise second reinforcements (16) placed in a second reinforced region (22) adjacent to the second face (20) and having main directions of resistance forming an angle less than 45 with the second face.
[Claim 4] A structure according to claim 3, wherein the directions main strength of the second reinforcements (16) are parallel to there second side of the embankment (15).
[Claim 5] Structure according to any one of the claims above, in which the reinforcements (16) are arranged horizontally.
[Claim 6] Structure according to any one of the claims above, in which the first face (10) of the backfill (15) is covered of a facing.
[Claim 7] Structure according to any one of the claims previous ones, further comprising secondary reinforcements arranged transversely to the first face (10).

[Claim 8] Structure according to any one of the claims above, wherein the first reinforcements (16) comprise metal reinforcements.
[Claim 9] Structure according to any one of the claims above, wherein the first reinforcements (16) comprise polymer reinforcements.
[Claim 10] Structure according to any one of the claims above, in which the reinforcements (16) comprise geogrid or geotextile reinforcements.
[Claim 11] Structure according to any one of the claims preceding ones, in which at least some of the first reinforcements (16) are arranged in successive segments along their main direction of resistance, with areas (25) of mutual overlap between the segments.
[Claim 12] A structure according to claim 11, wherein material of backfill is between successive segments of a first reinforcement (16), in the zones (25) of overlap.