Rockfall protection system

Abstract

Rockfall protection system (1) that provides protection of an underlying support structure (40,41) from experiencing a load exceeding a predefined design load, wherein the protection system (1) comprises a combination of an impact energy absorbing layer (10), a force distribution layer (20) and one or more energy absorbing components (30), wherein the impact energy absorbing layer (10) is supported by the force distribution layer (20), the force distribution layer (20) is resting on the one or more energy absorbing components (30), the one or more energy absorbing components (30) is resting on the support structure (40); wherein the force distribution layer (20) is a stiff planar deck structure; wherein the impact energy absorbing layer (10) comprises tubes (12) with plastic deformation properties, wherein the tubes extend parallel to the planar deck structure; and wherein the one or more energy absorbing components (30) are designed to absorb energy by deformation, such that the combination of the impact energy absorbing layer (10), the force distribution layer (20) and the one or more energy absorbing components (30) provides the protection.

Description

[0001] Rockfall protection system

[0002] The present invention is directed towards a system and method for protecting travel ways such as roads, railway lines and paths from rockfall, landslides, debris flow and avalanches.

[0003] Background

[0004] Protection of public transport systems and infrastructure are today mainly performed by installation of protection nets, building galleries in concrete, tunnels or establish protective valleys as barrier. These known alternatives are either high risk solutions with respect to safety during installation and maintenance, or expensive long lead projects with significant impact on the local environment and topography.

[0005] Prior art

[0006] A prior solution using protective nets is disclosed in EP2489785B1.

[0007] WO2021 152475 discloses a rock fall protection comprising an energy absorption by deformation.

[0008] An aim of the present invention is to provide a protection system that is easy to transport and install.

[0009] A further aim is to improve safety during installation and maintenance of a protective system.

[0010] Summary of invention

[0011] The present invention provides a rockfall, avalanche and landslide protection system that provides protection of an underlying support structure from experiencing a load exceeding a predefined design load, wherein the protection system comprises a combination of an impact energy absorbing layer, a force distribution layer and one or more energy absorbing components, wherein the impact energy absorbing layer is supported by the force distribution layer, the force distribution layer is resting on the one or more energy absorbing components, the one or more energy absorbing components is resting on the support structure; wherein the force distribution layer is a stiff planar deck structure; wherein the impact energy absorbing layer comprises tubes with plastic deformation properties, wherein the tubes extend parallel to the planar deck structure; and wherein the one or more energy absorbing components are designed to absorb energy by deformation, such that the combination of the impact energy absorbing layer, the force distribution layer and the one or more energy absorbing components provides the protection.

[0012] The present invention provides a protection structure wherein the combination of the different elements in the structure and their combined reaction in case of an impact, such as a rock fall, results in protection of the underlaying area. It is the combination of elements that together provides the protection at lower costs than the prior art solutions.

[0013] The present invention protects against rockfalls. The present invention will also function to protect from avalanches and landslides as well as debris flow that falls on the top of the protection structure. The protection structure accordingly protects against objects that fall on the protection with a force vector including a vector component that is orthogonal to the layers of the protection structure.

[0014] The force distribution layer distributes forces as a function of time from the impact energy absorbing layer to the energy absorbing components. In one aspect the force distribution layer ensures energy absorption in the energy absorbing components.

[0015] In one aspect the energy absorbing components are arranged in two or more rows, where the rows are spaced a part with a distance L. The two or more rows are respectively resting on a longitudinal element of the support structure. Thus, the rockfall protections system does not need any continuously supporting structure as the force distribution layer transfers the load to the supports via the energy absorbing components. The person skilled in the art will appreciate that the that distance L can be varied and adapted to the size and characteristics of the area to be protected etc.

[0016] The impact energy absorbing layer is absorbing the energy by plastic deformation by compression of the tubes in a special design. This design gives an almost constant force during deformation and thus the energy absorption and transfer of forces to the energy absorbing components can be controlled.

[0017] In one aspect of the protection system the plastic deformation properties of the impact energy absorbing layer is designed to absorb 30-70 % of the total impact energy of a falling rock with a mass G, wherein G is 5 kg - 10 t, representing impact energy of 100-5000 kJ, alternatively 40-60 % or 45-55 % of the total impact energy of a falling rock. Initially before the rock impacts on the protection system the total impact energy is equal to the kinetic energy of the falling rock.

[0018] In a further aspect of the protection system the deformation of the one or more energy absorbing components is designed to absorb 20-70 % of the total impact energy. Additionally, in this aspect of the protection system may be such that the remaining impact energy up to 100% is partly absorbed by the support structure and the ground and partly removed in the form of kinetic energy in the rock bouncing of the protection system.

[0019] In one aspect of the protection system the geometry of the components in the impact energy absorbing layer and the one or more energy absorbing components together provides an optimal energy absorption in the protection system as well as controlled transfer of forces to the supporting structure.

[0020] Further, the system may include the possibility of changing the mass of the protection system relative to the mass of the falling rock. This may be done by adding weight elements such as sand to the protection system. This will have an effect on the dynamics in the protection system.

[0021] In another aspect of the protection system the impact energy absorbing layer and the one or more energy absorbing components are made of metal. Optionally, the impact energy absorbing layer and the one or more energy absorbing components are made of aluminium or an aluminium alloy. Alternatively, some of the elements like the force distribution layer can be made of concrete or a composite material.

[0022] In a further aspect of the protection system the impact energy absorbing layer comprises one or more impact energy absorbing elements, wherein the impact energy absorbing element comprises two flange plates with the tubes extending between the two flange plates, wherein the tubes are arranged in parallel and the tubes are each secured to each of the two flange plates by tube securing elements. This design improves the control of the transfer of forces to the energy absorbing components to an almost constant force.

[0023] In one aspect of the protection system the distance b between two parallel tubes is at least 35 % of the outer diameter d of the tubes, preferably at least 40 % and more preferably between 40-60% of the outer diameter d of the tubes.

[0024] The distance between the tubes provides for deformation of the tubes in case of an impact over the deformation threshold without the tubes interacting as a result of the increase in diameter / cross-sectional length due to deformation of the tubes.

[0025] In a further aspect the protection system is installed on a main structure and the protective system is designed to maintain the integrity of the main structure during a predicted impact. In another aspect of the protection system one or more of the energy absorbing components each comprises one or more collapsible structures that during impact over a preselected impact energy level (trigger load) collapses in a direction perpendicular to the force distribution layer. The transfer of forces to the support structure is controlled by collapsing (triggering) the energy absorbing components.

[0026] In yet another aspect the protection system is a modular system wherein each module can be separated from the main structure independently.

[0027] The present invention further provides a method for maintenance of an installed rockfall protection system, wherein the protection system comprises modular protection elements each comprising an impact energy absorbing layer, a force distribution layer and one or more energy absorbing components and the method comprises removing one modular protection element from below and installing a modular protection element from below, such that an installer is protected by the remaining protection system during installation.

[0028] The modular system and the method provide cost savings compared to traditional protection systems.

[0029] In one aspect of the protection system the force distribution layer is a structure of a preselected mass. The force distribution layer can be a hollow metal grid structure or a metal grid structure comprising with volumes designed to contain gravity increasing substances such as sand or gravel. The filing of the volumes is performed to reach the desired preselected mass.

[0030] The support structure can have many shapes and designs. The support structure behaves elastic during an impact. The support structure can further be supported by a main structure comprising pillars / columns and / or the support structure can be mounted to a rock wall, such that a protected area is formed under the support structure.

[0031] The protection system may be installed with downward sloping angle a of from 5 to 45 degrees, such as 10-30 degrees or 12-20 degrees. The downward sloping angle provides the additional effect of assisting the transport of rock / sand / snow material away from the protection system. Firstly, due to the material sliding off the top structure, the impact energy absorbing layer. Secondly, because the change in direction of the material, after a vertical impact the materials kinetic energy will have a horizontal component due to the downward sloping angle.

[0032] Herein the term “stiff’ in “stiff planar deck structure” refers to the properties during an expected impact where the stiff planar deck is not deformed permanently and the impact energy not absorbed by the impact energy absorbing layer is distributed to the energy absorbing components and the support structure with a predictable loss.

[0033] The remaining energy after deformation of the impact energy absorbing layer is transferred to the energy absorbing components, by accelerating the mass of the combined impact energy absorbing layer and the stiff planar deck structure. The stiffness of the deck ensures support and deformation of the energy absorbing components in a much larger area outside the impact location.

[0034] The response to the support structure to an impact is similar to the response of the stiff planar deck structure in that the structure is not deformed permanently by the impact of a load not exceeding the design load.

[0035] The term “aluminium” as applied herein refers to aluminium and aluminium alloys in which the main metal compound is aluminium. The aluminium metal is selected based on is mechanical properties.

[0036] Brief description of the drawings

[0037] Features of the present invention are illustrated in the enclosed figures. The figures are schematic illustrations, and the size and design of the different elements are adapted for the purpose of illustration.

[0038] Figure 1 schematically illustrates the main elements of the protective system

[0039] Figure 2 illustrates schematically a section of the protective structure installed at an angle over a road.

[0040] Figure 3 illustrates the basic element of the impact energy absorbing layer

[0041] Figure 4 illustrates how the basic elements of the impact energy absorbing layer is put together.

[0042] Figure 5a - 5d illustrates the function of the system under impact from a falling rock.

[0043] Figure 5e illustrates the principles of the energy absorbing system

[0044] Figure 6a-6b illustrates embodiments the force distribution layer

[0045] Figure 7a-7b illustrates an energy absorbing component

[0046] Figure 8a-8d illustrates a modular protection system and the exchange of one module Figure 9 illustrates an embodiment of a module for a modular protection system

[0047] Figure 10 illustrates another embodiment of a module for a modular protection system.

[0048] Figure 11 illustrates an embodiment of the protection structure.

[0049] Principal description of the invention

[0050] The present invention will now be explained in detail with reference to the enclosed Figures.

[0051] Figure 1 is a schematic illustration of a protective system 1 and the main components thereof. On top facing a falling rock is the impact energy absorbing layer 10, which rests on a force distribution layer 20. The force distribution layer 20 rests on multiple energy absorbing components 30 which are connected to an underlaying support structure 40. During impact, forces will be transferred to the energy absorbing components and thus create a change in the momentum of the system.

[0052] Figure 2 illustrates a section of the impact protection system 1 installed over a road with a declining angle a to the horizontal. The additional support structure 41 provides the applicable height distance between the impact protection system and the road. Here the protection system is also secured to the rock wall.

[0053] The inclined arrangement results in an increased sliding off of material landing on the protection structure as well as influencing the angle of material that bounces off the protection structure.

[0054] Figure 11 schematically illustrates the impact protection system of Figure 2 showing more of the longitudinal expansion of the system over a road section. Here rows of energy absorbing components 30 are arranged on support structure beams 40, 40’ with a distance L between the rows of energy absorbing components. The beams extend over the road to be protected.

[0055] Figure 3 illustrates details of the impact absorbing layer 10. Tubes 12 are arranged in parallel between two flange plates 13’, 13”. The tubes are each secured to each flange plate with tube securing elements 11 ’, 11”. The distance b between the parallel tubes is selected based on the outer diameter d of the tubes such that when the tubes are deformed and collapsed due to an impact neighbouring tube do not touch each other.

[0056] In an embodiment where the impact energy absorbing layer of Figure 3 is part of a protection structure according to Figure 2 the longitudinal direction of the tubes 12 can be arranged at the angle a, such that the tubes in the longitudinal direction span across the road, which in some situations could make the installation easier. Alternatively, the longitudinal direction of the tubes could extend parallel to the longitudinal direction of the area to be protected. Further, the longitudinal direction of the tubes could variate throughout the impact energy absorbing layer.

[0057] Figure 4 illustrates another embodiment of the impact energy absorbing layer 110 which here comprises a stack of three impact energy absorbing elements 14. The impact energy absorbing layer may comprise from 1 to 10 impact energy absorbing elements 14, or the layer may comprise 2 to 6, or 2 to 4, or 3 to 5 impact energy absorbing elements. As discussed above, when installed the longitudinal direction of the tube could extend across the longitudinal direction of the area to be protected.

[0058] Figure 5a - 5d illustrates the function of the system under impact from a falling rock. Here w is the displacement of the rock during impact and u the deformation of the energy absorbing components. The compression of the impact energy absorbing layer is then v = w — u. Figure 5b illustrates the situation before the energy absorbing components are activated, i.e. u=0. Figure 5c show the situation when the energy absorbing components are activated. Only elastic deformations are assumed in the force distribution layer 20 and is shown as the deformation p.

[0059] Figure 5a shows the system at impact of the rockfall 70, whereas Figure 5b shows the system in a deformed configuration. During impact, the rockfall 70 will get a displacement w. At the same time the distribution layer 20 will act globally as a “rigid” body and transfer forces to the supports. The deformation at the supports in the energy absorbing components 30 is denoted u.

[0060] The supporting structure, 40, shall behave elastic during an impact. The energy absorbing components 30 in the illustrated embodiment are arranged in two groups with a distance therebetween.

[0061] Figure 5e shows in principle how the energy absorbing system, 1, will work during an impact. The rockfall, 70, is assumed rigid and is represented by a mass G with an impact velocity VQ - A constant contact force P=P0is assumed between the mass of the energy absorbing layer 10 and the rockfall 70. Mass AT is the activated mass in the energy absorbing layer and the distribution layer (10+20), whereas Fois the activated forces at the energy absorbing components 30.

[0062] Based on the systems shown in Figure 5e, two dynamic equilibrium equations can be obtained

[0063] —Gw — Po= 0

[0064] —Mil + Po - Fo — 0 Further the plastic spring deformation between G and M denoted v can be expressed as v = w — u

[0065] The maximum deformation vmof the energy absorbing layer 10 can be expressed as

[0066] The total deformation umof the energy absorbing components 30 can be expressed as

[0067] In the calculation, it is assumed that the two masses G and M move with the same velocity beyond the time when v = w — u = 0

[0068] Finally, the activation of the energy absorbing components at the supports is only possible when Fo> Fo

[0069] The equations above clearly indicate the nonlinearity of the system and how the different parameters affect the response in the deck as well as in the supports. The calculated displacement of the energy absorbing layer 10 and the displacement of the energy absorbing components 30 show that the response is controlled by the mass ratio G / M as well as the ratio Fo / Fo.

[0070] Figure 6a and 6b illustrate alternative designs for the energy / force distribution layer 20,120. The structure is rigid but may be deformed elastically. As illustrated in Figure 5 the impact energy layer is deformed below the impact area whereas the force distribution layer distributes forces to a number of energy absorbing components 30 surrounding the impact area.

[0071] Figure 7a illustrates an energy absorbing component 30 comprising first end section 31, second end section 32 and a deformation element 34 arranged therebetween. The deformation element 34 is preferably made of extruded aluminium and designed to absorb impact energy by deformation when subject to an impact over a threshold called the folding load, Fo. The deformation element is designed to have a deformation pattern that is a repeating stable folding pattern, which provides the required energy absorption.

[0072] The deformation element 34 can have many shapes, it may be a hollow cylindrical element with a cross section that can be circular, rectangular, polygonal, elliptic, or any combination thereof. The deformation element 34 can be a pillar with vertical flanges where the flanges and the pilar wall is designed to fold when experiencing a force above a trigger load. Figure 7b illustrates the deformation element 35 after such an impact. The deformed energy absorbing component 38 has been deformed by the deformation u.

[0073] Fo= is the Mean-load level during deformation / folding phase. u= the deformation length designed for the component.

[0074] Energy absorption: E(J)= F0(N)* u (m)

[0075] In one embodiment the energy absorbing component is designed to have a Fo in the range of 50-500kN. Preferably the initial buckling load is minimum 1.33* Foand maximally 1.5*F0.

[0076] To ensure a constant and controlled load Fo, a trigger mechanism is introduced by design of a material property- or geometrical-imperfection in the component to control the initial buckling load. The imperfections are arranged such that the deformation starts at the top, closest to the force distribution layer.

[0077] The design of the energy absorbing component also ensures a capacity of both shear load and tension to maintain structural integrity during a rockfall.

[0078] The targeted stable load Fois achieved by design of size and number of cells in the component in combination with wall thickness and material strength of the material.

[0079] A repeating stable folding and deformation pattern is required for energy absorption in the energy absorbing components. Within other very different industries such deformation by energy absorption is known.

[0080] Figures 8a-8d schematically illustrates the side view of the possible modular structure of the protection structure and the possibility to exchange one module while the person and vehicle performing the maintenance is protected by the remaining part of the protection structure. In Figure 8a the protection structure 1 is arranged on a support structure 40 and an additional support structure 41 above a road. The protection structure is made up of protection structure modules 50. The element 55 is a damage protection structure module that needs to be exchanged. The installer 58 as well as the installer vehicle 59 are positioned below the protection structure and are protected by the protection structure during the maintenance operation.

[0081] Here the support structure 40 comprises beams extending across the road with a width sufficient to support two rows of energy absorbing components, one form each of two adjacent protection structure modules. The beams 40 are supported by column like elements 41 of the additional support structure.

[0082] Figure 8b illustrates the removed damaged protection structure module loaded onto the installer vehicle 59. The operation can be performed by a crane on the vehicle liftin of the damaged module 55. In one embodiment the modules may be fastened to the additional support structure 41 and or to the rock wall. The fastening can be by interlocking designs and / or by fasteners (not shown) that will have to be removed before the module can be removed.

[0083] Figure 8c illustrates the new protection structure module 50’ on the vehicle below the remaining part of the protection structure just prior to installation. In this way also the new module 50’ is protected prior to installation.

[0084] Figure 8d illustrates the protection structure 1 after the repair has been completed One or more components can be assembled on one base plate to form a module to ensure efficiency in installation and replacement. The new module 50’ can be lifted into place by a crane on the vehicle and secured by interlocking with the additional support and or by additional fasteners.

[0085] In a preferred embodiment wherein the protection structure modules are primarily made of aluminium, the weight of one module is limited such that a crane mounted on a vehicle can lift one module in place.

[0086] Figure 9 illustrates the components of one embodiment of the protection structure module 50. In this embodiment all the elements of the impact energy absorbing layer 10, the force distribution layer 20, and the energy absorbing components 30 are prepared as one module to be installed in one operation. A person skilled in the art will appreciate that it is also possible to divide the module up to sub-modules that can be installed in sequence. One such embodiment is illustrated on figure 10, where there is a top module 52 comprising the impact energy absorbing layer 10 and the force distribution layer 20. A base module 54 comprises the energy absorbing components 30 mounted on a base plate 60. In this embodiment the one or more energy absorbing components can be assembled on one base plate 60 to ensure efficiency in installation and replacement. Here it will also be possible to replace only a submodule or even a part of a submodule such as one energy absorbing component or one impact energy absorbing element 14, see figure 4.

[0087] The base plates can be designed for mechanical mounting to the force distribution layer.

[0088] A guiding system can be installed in the protection system to ensure minimal horizontal movements in between the submodules. This secures that the energy absorbing components 30 extend perpendicular to the force distribution layer 20 and that an impact therefore would deform the energy absorbing component as designed.

[0089] Reference numbers:

[0090]

Claims

CLAIMS1. Rockfall, avalanche and landslide protection system (1) that provides protection of an underlying support structure (40) from experiencing a load exceeding a predefined design load, wherein the protection system (1) comprises a combination of an impact energy absorbing layer (10), a force distribution layer (20) and one or more energy absorbing components (30), wherein the impact energy absorbing layer (10) is supported by the force distribution layer (20), the force distribution layer (20) is resting on the one or more energy absorbing components (30), the one or more energy absorbing components (30) is resting on the support structure (40); wherein the force distribution layer (20) is a stiff planar deck structure; wherein the impact energy absorbing layer (10) comprises tubes (12) with plastic deformation properties, wherein the tubes extend parallel to the planar deck structure; and wherein the one or more energy absorbing components (30) are designed to absorb energy by deformation, such that the combination of the impact energy absorbing layer (10), the force distribution layer (20) and the one or more energy absorbing components (30) provides the protection.

2. Protection system according to claim 1, wherein the plastic deformation properties of the impact energy absorbing layer (10) is designed to absorb from 30-70 % of the total impact energy of a falling rock with a mass G, wherein G is 5 kg - 10 t, representing impact energy of 100-5000 kJ, alternatively 40-60 % or 45-55 % of the total impact energy of a falling rock.

3. Protection system according to claim 2, wherein the deformation of the one or more energy absorbing components (30) is designed to absorb 20-70 % of the total impact energy.

4. Protection system according to claim 3, wherein the remaining impact energy up to 100% is partly absorbed by the support structure (40) and the ground and partly removed in the form of kinetic energy in the rock bouncing of the protection system.

5. Protection system according to any one of the claims 1-4, wherein the force distribution layer ensures energy absorption in the energy absorbing components.

6. Protection system according to any one of the claims 1-5, wherein the energy absorbing components (30) are arranged in two or more rows on separate support structure elements (40,40’), wherein the rows and the support structure elements are spaced a part with a distance L.

7. Protection system according to claim 6, wherein the support structure elements are beam shaped elements that extend in one direction over the area to be protected by the protection system.

8. Protection system according to any one of the claims 1-7, wherein the impact energy absorbing layer (10) and the one or more energy absorbing components (30) are made of metal.

9. Protection system according to claim 8, wherein the impact energy absorbing layer (10) and the one or more energy absorbing components (30) are made of aluminium or an aluminium alloy.

10. Protection system according to any one of claims 1-9, wherein the impact energy absorbing layer (10) comprises one or more impact energy absorbing elements (14), wherein the impact energy absorbing element (14) comprises two flange plates (13’, 13”) with the tubes (12) extending between the two flange plates (13’, 13”), wherein the tubes (12) are arranged in parallel and the tubes are each secured to each of the two flange plates (13’, 13”) by tube securing elements (11’, 11”).

11. Protection system according to claim 10, wherein the distance (b) between two parallel tubes is at least 35 % of the outer diameter (d) of the tubes (12), preferably at least 40 % and more preferably between 40-60% of the outer diameter (d) of the tubes (12).

12. Protection system according to any one of the claims 1-11, wherein the protective system is installed on a main structure (41) and the protective system is designed to maintain the integrity of the main structure during a predicted impact.

13. Protection system according to any one of the claims 1-12, wherein one energy absorbing component (30) comprises one or more collapsible structures that during impact over a preselected impact energy level collapses perpendicular to the force distribution layer (20).

14. Protection system according to any one of the claims 1-13, wherein the protection system is a modular system wherein each module can be separated from the main structure independently.

15. Method for maintenance of an installed rockfall protection system, wherein the protection system comprises modular protection elements (50) each comprising an impact energy absorbing layer (10), an force distribution layer (20), and one or more energy absorbing components (30) and the method comprises removing one modular protection element (55) from below and installing a modular protection element (50) from below, such that an installer (58,59) is protected by the remaining protection system during installation.

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