Stiffness compatibility test structure and test method for actively unloading crushed stone reinforced structures

Abstract

This invention pertains to the field of tunnel structure testing technology, specifically a stiffness coordination testing structure and method for actively unloading gravel-reinforced structures. It includes two supports, on which a gabion cage is mounted. Several tension rod assemblies are installed on the gabion cage, each with a strain gauge connected to a static strain gauge. Two I-beams are positioned on the upper surface of the gabion cage. A reaction frame is located on the experimental platform, with jacks positioned between the reaction frame and the I-beams on the upper surface of the two I-beams. A non-contact full-field strain measurement system is also installed on the experimental platform to measure the displacement data of the lower edge of the gabion cage. This method can simulate the working state of an actively unloading gravel-reinforced structure in a tunnel indoors, realistically reproducing the stress and unloading mechanisms of such structures and reflecting the overall stiffness evolution characteristics.

Description

Technical Field

[0001] This invention relates to the field of tunnel structure testing technology, and in particular to a stiffness coordination testing structure and method for an actively unloading crushed stone reinforcement structure. Background Technology

[0002] During tunnel excavation, the stress release caused by unloading the surrounding rock can lead to deformation and crack development of the surrounding rock, resulting in the lining structure being in a complex stress environment for a long time. In order to reduce the impact of concentrated surrounding rock pressure on the tunnel support structure, the engineering community has gradually proposed and applied active unloading structures.

[0003] However, existing active unloading structures are rarely used in tunnel engineering. In particular, the crushed stone filling structure similar to gabion stone cages has not been fully studied, and its unloading mechanism and overall structural stiffness characteristics lack systematic experimental verification.

[0004] On the other hand, existing research often focuses on the stress characteristics of local components, with less research on measuring the overall stiffness of the structure and its variation during loading. This, to some extent, restricts the promotion and optimization design of related structures in tunnel engineering.

[0005] Therefore, there is an urgent need for a stiffness coordination test structure and test method for actively unloading crushed stone reinforcement structures, so as to truly reflect the overall stiffness evolution characteristics of actively unloading crushed stone reinforcement structures, thereby providing a scientific basis for the rational design and application of such structures in tunnel engineering. Summary of the Invention

[0006] This invention aims to solve the above-mentioned problems, thereby providing a stiffness coordination test structure and test method for actively unloading crushed stone reinforcement structures. It can simulate the working state of actively unloading crushed stone reinforcement structures in tunnels indoors, and can realistically reproduce the stress and unloading mechanism of actively unloading crushed stone reinforcement structures in tunnels under indoor conditions. It can truly reflect the overall stiffness evolution characteristics of actively unloading crushed stone reinforcement structures, thereby providing a scientific basis for the rational design and application of such structures in tunnel engineering.

[0007] The technical solution adopted by the present invention to solve the aforementioned problem is as follows:

[0008] A stiffness coordination test structure for an actively unloading crushed stone reinforcement structure is set on an experimental platform. It includes two identical supports placed parallel to each other on the platform. A gabion cage is mounted on both supports. Several tension rod assemblies are installed on the gabion cage between the two supports, penetrating vertically through the cage and spaced apart along its length. At least one strain gauge is installed on each tension rod assembly, located inside the gabion cage. A static strain gauge is connected to the strain gauge. Two I-beams are symmetrically arranged on the upper surface of the gabion cage, with the length dividing line of the gabion cage as the centerline. A reaction frame is positioned directly above the two I-beams on the experimental platform. Jacks are installed on the upper surface of the two I-beams, located between the reaction frame and the I-beams. A non-contact full-field strain measurement system for measuring the displacement data of the lower edge of the gabion cage is set on the experimental platform.

[0009] Preferably, the length of the gabion is greater than the distance between the two supports, and both ends of the gabion extend beyond the supports.

[0010] Preferably, the gabion includes a metal mesh cage, which is hollow inside and filled with crushed stone.

[0011] Preferably, the crushed stone is stacked in layers along the height direction inside the metal mesh cage.

[0012] Preferably, the tie rod assembly includes a tie rod that extends vertically through the gabion cage, with both ends of the tie rod extending outward from the gabion cage. Each end of the tie rod is threaded with a fastening nut, and the two fastening nuts work together to fix the tie rod to the gabion cage.

[0013] Preferably, two strain gauges are provided on the outer surface of each tie rod, the two strain gauges are spaced apart along the length of the tie rod, the two strain gauges are located inside the gabion cage, and the two strain gauges are connected to a static strain gauge.

[0014] Preferably, when the gabion is subjected to a load applied by two jacks, the overall stiffness of the gabion is obtained by simultaneously acquiring the displacement data measured by the non-contact full-field strain measurement system and the axial force measured by the static strain gauge on the tie rod, and by combining the deflection calculation formula of a simply supported beam.

[0015] Preferably, when the gabion is subjected to a load applied by two jacks, the overall stiffness of the gabion changes with the change in the fastening force applied to the gabion by the tie rod assembly.

[0016] Preferably, the overall stiffness of the gabion and the fastening force applied to the gabion by the tie rod assembly vary with the load on the gabion.

[0017] A test method for the stiffness compatibility of an actively unloading crushed stone reinforced structure includes the following steps:

[0018] S1. Place two supports on the experimental platform according to the length of the gabion cage, place the gabion cage on the two supports, and install several tie rod assemblies on the gabion cage between the two supports, so that the tie rod assemblies are spaced apart and pass through the gabion cage along the length of the gabion cage. Then, apply a fastening force to each tie rod assembly in sequence according to the test specifications.

[0019] S2. Before fixing the tie rod assembly on the gabion cage, strain gauges are attached to the tie rods. After the tie rod assembly is fixed on the gabion cage, the strain gauges are connected to the static strain gauge.

[0020] S3. Place the non-contact full-field strain measurement system on the experimental platform and adjust the non-contact full-field strain measurement system according to the position of the lower edge of the gabion cage so that the position of the non-contact full-field strain measurement system corresponds to the position of the lower edge of the gabion cage.

[0021] S4. Then place two I-beams on the upper surface of the gabion cage, with the two I-beams symmetrically arranged with the length dividing line of the gabion cage as the center line. Then place the reaction frame on the experimental platform and place two jacks between the reaction frame and the two I-beams.

[0022] S5. When the reaction frame, two jacks and two I-beams work together to apply load to the gabion, the static strain gauge and the non-contact full-field strain measurement system simultaneously collect the axial force of the tie rod under the load and the displacement data of the lower edge of the gabion.

[0023] S6. When the displacement data of the lower edge of the gabion cage and the axial force of the tie rod under load are obtained, the displacement of the lower edge of the gabion cage is: Where P is the total applied load, a is the distance from the support point to the adjacent loading point, L is the support span, E is the elastic modulus, I is the moment of inertia of the section, and δ is the displacement of the lower edge. Therefore, the elastic modulus is: Thus, the overall stiffness of the gabion is calculated.

[0024] The present invention, which adopts the above technical solution, has the following prominent features compared with the prior art:

[0025] This invention can simulate the stiffness change characteristics of an actively unloading crushed stone reinforcement structure in a tunnel during the unloading process indoors. It can simulate the working state of the actively unloading crushed stone reinforcement structure in a tunnel, and use loading experiments to realize the stress during the unloading process and thus study the stiffness change law. This improves the scientificity and reliability of tunnel support structure design and optimization. It can realistically reproduce the stress and unloading mechanism of the actively unloading crushed stone reinforcement structure in a tunnel under indoor conditions, and can truly reflect the overall stiffness evolution characteristics of the actively unloading crushed stone reinforcement structure. It has the advantages of simple structure, convenient operation, and intuitive parameter monitoring, which significantly improves the scientificity, authenticity and credibility of the test results, thus providing a scientific basis for the rational design and application of such structures in tunnel engineering. Attached Figure Description

[0026] Figure 1 This is a schematic diagram of the main view structure of the present invention;

[0027] Figure 2 This is a schematic diagram of the facade structure of the present invention;

[0028] Figure 3 This is a schematic diagram of the main view of the tie rod structure of the present invention;

[0029] Figure 4 This is a schematic diagram of the testing process of the present invention. Figure 1 ;

[0030] Figure 5 This is a schematic diagram of the testing process of the present invention. Figure 2 ;

[0031] Figure 6 This is a schematic diagram of the testing process of the present invention. Figure 3 ;

[0032] Figure 7 This is a schematic diagram of the testing process of the present invention. Figure 4 ;

[0033] In the diagram: 1. Support; 2. Metal mesh cage; 3. Crushed stone; 4. Tie rod; 5. Fastening nut; 6. I-beam; 7. Strain gauge; 8. Jack; 9. Gabion; 10. Tie rod assembly. Detailed Implementation

[0034] The following description of the embodiments will help the public better understand the present invention. However, the specific embodiments provided by the applicant should not and should not be regarded as a limitation on the technical solution of the present invention. Any changes to the definition of components or technical features and / or formal but not substantive changes to the overall structure should be regarded as the scope of protection defined by the technical solution of the present invention.

[0035] See Figures 1 to 7 As shown, the technical solution of the present invention is as follows:

[0036] A stiffness coordination test structure for an actively unloading crushed stone reinforcement structure is set on an experimental platform. It includes two identical supports 1, both steel supports 1, with both upper and lower surfaces being planar. The two supports 1 are placed on the experimental platform at an interval, parallel to each other. A gabion cage 9 is placed on both supports 1, the length of which is greater than the distance between the two supports 1, and both ends of the gabion cage 9 extend beyond the supports 1. Several tie rod assemblies 10 are installed on the gabion cage 9 located between the two supports 1, penetrating vertically through the gabion cage 9, and arranged sequentially along the length of the gabion cage 9. The structure is designed with a tie rod assembly 10 as the main force transmission component. The tie rod 4 extends vertically through the gabion cage 9, with both ends extending outwards from the gabion cage 9. Threads are provided on both ends of the tie rod 4, and fastening nuts 5 are threadedly connected to each end. The two fastening nuts 5 work together to fix the tie rod 4 to the gabion cage 9. The tie rod 4 is made of HRB400 steel bar, A18mm diameter, 160mm long threaded steel bar, while the fastening nuts 5 are M18 diameter, 20mm long. The tie rod assembly 10 reinforces the gabion cage 9 into a beam by adjusting the tightening force of the nuts. Additionally, the bolts apply a tightening force, i.e., prestress, which controls the stiffness of the gabion cage 9. A relationship between different prestresses and elastic moduli was established. Two strain gauges 7 were attached to the outer surface of each tie rod 4 of the tie rod assembly 10. The two strain gauges 7 were spaced apart along the length of the tie rod 4 and were located inside the gabion cage 9. Both strain gauges 7 were connected to a static strain gauge, thereby measuring the axial force (i.e., prestress) of the tie rod 4 under load through the cooperation of the static strain gauge and the strain gauges 7. Two I-beams 6 were placed on the upper surface of the gabion cage 9, symmetrically arranged with the length boundary line of the gabion cage 9 as the centerline. A reaction frame was placed on the experimental platform, located directly above the two I-beams 6. Jacks 8 are placed on the upper surface of gabion 9, positioned between the reaction frame and the I-beam 6. The reaction frame, two jacks 8, and two I-beams 6 work together to apply load to the gabion 9, causing the crushed stone 3 and the tie rods to undergo a stress response. This simulates the working state of the actively unloading crushed stone reinforcement structure under load. Furthermore, the load applied to the gabion 9 can be varied to provide different unloading states, simulating structural stiffness coordination. This reproduces the impact of varying unloading levels on structural stiffness coordination characteristics in actual tunnel engineering. A non-contact full-field strain measurement system is placed on the experimental platform, corresponding to the lower edge of the gabion 9, to measure the displacement data of the lower edge of the gabion 9.Therefore, the displacement data of the lower edge of the gabion cage 9 obtained by measurement is used to calculate the overall stiffness of the structure, realizing non-contact measurement of structural deformation, obtaining the stress-displacement curve of the structure, and ensuring the accuracy and reliability of data acquisition. Furthermore, the above structural setup is used to simulate the stiffness variation characteristics of the actively unloading crushed stone reinforcement structure 3 in the tunnel.

[0037] The gabion 9 includes a metal mesh cage 2, which is welded from high-strength metal wire and has sufficient overall rigidity. The metal mesh cage 2 is 600mm long, 100mm wide, and 100mm high. The interior of the metal mesh cage 2 is hollow and filled with crushed stone 3. The crushed stone 3 is stacked in layers along the height direction inside the metal mesh cage 2. The crushed stone 3 is filled in layers during the filling process, and each layer of crushed stone 3 is lightly vibrated after placement to avoid excessive local gaps that would affect the uniformity of stress distribution. The particle size of the crushed stone 3 is controlled within a specified range, such as 20-40 mm, to ensure good compressibility and permeability, which can release some external forces in the early stages of loading and reduce stress concentration. The metal mesh cage 2 plays a role in stabilizing the crushed stone 3, ensuring the integrity of the overall structure of the gabion 9 and its controllable deformation performance. The above-mentioned structural settings of the gabion 9 are designed to achieve an active unloading function.

[0038] When the gabion 9 is subjected to the load applied by the two jacks 8, the displacement data measured by the non-contact full-field strain measurement system and the axial force measured by the static strain gauge on the tie rod 4 are obtained simultaneously. Combined with the deflection calculation formula of a simply supported beam, the overall stiffness of the gabion 9 is obtained. This reveals the stiffness coordination characteristics of the actively unloaded crushed stone 3 reinforced structure, and further analyzes the stiffness coordination characteristics of the actively unloaded crushed stone 3 reinforced structure. In addition, by calculating the stiffness of the entire structure, the bearing capacity and coordination performance of the structure under different loads and prestressing can be determined.

[0039] When the gabion 9 is subjected to the load applied by the two jacks 8, the overall stiffness of the gabion 9 changes with the change of the fastening force applied to the gabion 9 by the tie rod assembly 10; while adjusting the fastening force of the fastening nut 5 on the tie rod assembly 10, the change of the axial force in the tie rod 4, that is, the change of the prestress in the whole structure, can establish the relationship between different prestresses and elastic moduli.

[0040] The overall stiffness of the gabion 9 and the fastening force applied to the gabion 9 by the tie rod assembly 10 vary with the load on the gabion 9; in order to simulate different prestressing and unloading states, and thus reproduce the influence of surrounding rock pressure release on structural stiffness in actual tunnel engineering.

[0041] It should be noted that: the experimental platform, reaction frame, static strain gauge, and non-contact full-field strain measurement system are not shown in the attached drawings; both I-beams 6 are integrally formed of steel; the width of the gabion 9 is consistent with the width of the two supports 1 and the width of the two I-beams 6; in addition, the specifications and tonnage of the two jacks 8 and the specifications of the reaction frame all change with the load applied to the gabion 9.

[0042] Furthermore, the static strain gauge adopts the CM1J model, which features a digital keypad for easier selection of measurement points and setting of strain gauge sensitivity. It also utilizes a dedicated mathematical model to directly display force and displacement values, providing a simple and easy-to-use method for various measurements. Built-in non-volatile memory allows for 99 levels of data storage and playback, facilitating fieldwork. Connecting to a computer via an RS232 interface enables data acquisition, analysis, and processing.

[0043] In addition, the non-contact full-field strain measurement system adopts the PMLAB DIC-3D non-contact three-dimensional strain optical measurement system and Digital Image Correlation technology, which is an algorithm that compares images by correlating points. This method can calculate the surface displacement and strain distribution of an object. The entire measurement process only requires one or two image acquisition devices to capture images of the object before and after deformation. After calculation, the 3D full-field strain data distribution can be clearly seen. Unlike strain gauge 7, which requires a lot of time for surface smoothing and pasting, and can only measure strain data in a certain direction at a single point. Unlike the fringe interferometry method, which has strict environmental requirements, the DIC method obtains 3D data across the entire field. The PMLABDIC-3D non-contact three-dimensional strain optical measurement system is mainly used for non-contact full-field measurement of the three-dimensional coordinates, displacement, and strain of objects. Based on the principle of binocular stereo vision, the system acquires images of the object surface through dual cameras, reconstructs the three-dimensional morphology using digital image correlation algorithms, and analyzes the deformation field. It can detect parameters such as the displacement distribution and principal strain direction of materials under static and dynamic loading states. It supports data interaction with engineering software such as LabVIEW and ANSYS and is suitable for mechanical property testing scenarios such as metals and composite materials.

[0044] A test method for the stiffness compatibility of an actively unloading crushed stone reinforced structure includes the following steps:

[0045] S1. Place two supports 1 on the experimental platform according to the length of the gabion cage 9, place the gabion cage 9 on the two supports 1, and install several tie rod assemblies 10 on the gabion cage 9 between the two supports 1, so that the tie rod assemblies 10 are spaced apart and pass through the gabion cage 9 along the length direction of the gabion cage 9. Then, apply fastening force, i.e. prestress, to each tie rod assembly 10 in sequence according to the test specifications.

[0046] S2. Before the tie rod assembly 10 is fixed on the gabion 9, strain gauges 7 are attached to the tie rod 4. After the tie rod assembly 10 is fixed on the gabion 9, the strain gauges 7 are connected to the static strain gauge.

[0047] S3. Place the non-contact full-field strain measurement system on the experimental platform and adjust the non-contact full-field strain measurement system according to the position of the lower edge of the gabion 9 so that the position of the non-contact full-field strain measurement system corresponds to the position of the lower edge of the gabion 9, thereby calibrating the displacement of the lower edge of the gabion 9.

[0048] S4. Then place two I-beams 6 on the upper surface of the gabion cage 9, and set the two I-beams 6 symmetrically with the length dividing line of the gabion cage 9 as the center line. Then place the reaction frame on the experimental platform and place the two jacks 8 between the reaction frame and the two I-beams 6 respectively.

[0049] S5. When the reaction frame, two jacks 8 and two I-beams 6 work together to apply load to the gabion 9, the static strain gauge and the non-contact full-field strain measurement system simultaneously collect the axial force of the tie rod under the load and the displacement data of the lower edge of the gabion 9. Then, the load applied to the gabion 9 is increased, and the deflection of the gabion 9 is measured. Subsequently, the tie rod assembly 10 is adjusted to reduce the fastening force, i.e., the prestress, applied by the tie rod assembly 10 to the gabion 9. At this time, the overall stiffness of the gabion 9 decreases and the deflection increases. Thus, the relationship between the fastening force and the overall stiffness of the gabion 9 can be analyzed. In addition, the relationship between the structural stiffness and the prestress and the load can also be analyzed by reducing the load.

[0050] S6. When the displacement data of the lower edge of gabion cage 9 and the axial force of tie rod 4 under load are obtained, the displacement of the lower edge of gabion cage 9 is: Where P is the total applied load, each of the two I-beams is loaded with a load of P / 2, a is the distance from the support point to the adjacent loading point, L is the support span, E is the modulus of elasticity, I is the moment of inertia of the section, and δ is the displacement of the lower edge. Therefore, the modulus of elasticity is: The overall stiffness of gabion 9 was calculated; the stiffness E was back-calculated using the theory of simply supported beams, and the relationship between stiffness and prestress was analyzed; the curves of structural stiffness with the axial force of steel bars (i.e., prestress) and external loads were plotted, and the stiffness coordination law was analyzed, providing a basis for the design of actively unloading structures in actual engineering.

[0051] This invention can simulate the stiffness change characteristics of an actively unloading crushed stone 3-reinforced structure in a tunnel during the unloading process indoors. It can simulate the working state of the actively unloading crushed stone 3-reinforced structure in a tunnel, and use loading experiments to realize the stress during the unloading process and thus study the stiffness change law. This improves the scientificity and reliability of tunnel support structure design and optimization. It can realistically reproduce the stress and unloading mechanism of the actively unloading crushed stone 3-reinforced structure in a tunnel under indoor conditions, and can truly reflect the overall stiffness evolution characteristics of the actively unloading crushed stone 3-reinforced structure. It has the advantages of simple structure, convenient operation, and intuitive parameter monitoring, which significantly improves the scientificity, authenticity and credibility of the test results, thus providing a scientific basis for the rational design and application of such structures in tunnel engineering.

[0052] The above description is merely a preferred embodiment of the present invention and is not intended to limit the scope of the present invention. All equivalent changes made based on the description and drawings of the present invention are included within the scope of the present invention.

Claims

1. A stiffness coordination test structure of a proactively unloading type of a rockfall reinforcement structure, which is provided on an experimental platform, characterized in that: The two supports are arranged on the experimental platform in parallel with each other and are spaced apart, and the gabion is arranged on the two supports. A plurality of tension link assemblies are arranged on the gabion between the two supports, and the plurality of tension link assemblies are arranged in sequence and spaced apart along the length direction of the gabion and penetrate the gabion in the up-down direction. At least one strain gauge is arranged on each tension link assembly and located in the gabion. A static strain gauge is connected to the strain gauge. Two I-beams are arranged on the upper surface of the gabion and are symmetrically arranged with the length dividing line of the gabion as the center line. A counterforce frame is arranged on the experimental platform above the two I-beams. Jacks are arranged on the upper surfaces of the two I-beams and are located between the counterforce frame and the I-beams. A non-contact full-field strain measurement system is arranged on the experimental platform to measure the displacement data of the lower edge of the gabion.

2. The stiffness-consistent test structure for a self-unloading stone column reinforcement structure according to claim 1, characterized by: The length of the gabion is greater than the distance between the two supports, and the two ends of the gabion extend out of the supports.

3. The stiffness-consistent test structure for a self-unloading stone column reinforcement structure according to claim 1, characterized by: The gabion comprises a metal mesh cage box, which is hollow inside and filled with gravel.

4. The stiffness-consistent test structure for a self-unloading stone column reinforcement structure according to claim 3, characterized in that: The gravel is stacked in layers in the height direction in the metal mesh cage box.

5. The stiffness-consistent test structure for a self-unloading stone column reinforcement structure according to claim 1, wherein: The tension link assembly comprises a tension link, which penetrates the gabion in the up-down direction and extends out of the gabion at two ends. A fastening nut is threadedly connected to each end of the tension link. The two fastening nuts cooperate to fix the tension link on the gabion.

6. The stiffness-consistent test structure for a self-unloading stone column reinforcement structure according to claim 5, wherein: Two strain gauges are arranged on the outer surface of the tension link and are spaced apart along the length direction of the tension link. The two strain gauges are located in the interior of the gabion and are connected to a static strain gauge.

7. The stiffness-consistent test structure for a self-unloading stone column reinforcement structure of claim 1, wherein: When the gabion is subjected to the load applied by the two jacks, the displacement data of the gabion measured by the non-contact full-field strain measurement system and the axial force of the tension link measured by the static strain gauge are synchronously acquired. The overall stiffness of the gabion is obtained by combining the deflection calculation formula of the simply supported beam.

8. The stiffness-consistent test structure for a self-unloading stone column reinforcement structure of claim 1, wherein: When the gabion is subjected to the load applied by the two jacks, the overall stiffness of the gabion changes with the change of the fastening force of the tension link assembly on the gabion.

9. The stiffness-consistent test structure for a self-unloading stone column reinforcement structure of claim 1, wherein: The overall stiffness of the gabion and the fastening force of the tension link assembly on the gabion change with the change of the load on the gabion.

10. A test method for testing a stiffness coordination structure of an active unloading type rockfall reinforcement structure according to any one of claims 1-9, characterized in that: The method comprises the following steps: S1. Two supports are arranged on the experimental platform according to the length of the gabion. The gabion is arranged on the two supports. A plurality of tension link assemblies are arranged on the gabion between the two supports, and the plurality of tension link assemblies are arranged in sequence and spaced apart along the length direction of the gabion and penetrate the gabion in the up-down direction. Then, the fastening force of each tension link assembly is applied according to the test specification. S2. Before the tension link assembly is fixed on the gabion, a strain gauge is pasted on the tension link. After the tension link assembly is fixed on the gabion, the strain gauge is connected to a static strain gauge. S3, place the non-contact full-field strain measurement system on the experimental platform, and adjust the non-contact full-field strain measurement system according to the position of the lower edge of the gabion, so that the non-contact full-field strain measurement system corresponds to the position of the lower edge of the gabion; S4, then place two I-beams on the upper surface of the gabion, and the two I-beams are symmetrically arranged with the length division line of the gabion as the center line, then place the counterforce frame on the experimental platform, and place the two jacks corresponding to the counterforce frame and the two I-beams; S5, when the counterforce frame, the two jacks and the two I-beams jointly apply load to the gabion, the static strain gauge and the non-contact full-field strain measurement system synchronously collect the axial force of the tension link under the action of the load and the displacement data of the lower edge of the gabion. S6、When the displacement data of the lower edge of gabion and the axial force of the pull rod under the action of load are obtained, the displacement of the lower edge of the gabion is: wherein P is the total load applied, a is the distance from the support point to the adjacent loading point, L is the support span, E is the elastic modulus, I is the cross-sectional moment of inertia, and δ is the displacement of the lower edge, and the elastic modulus is: and the overall stiffness of the gabion is calculated.

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