Finite element analysis and structure improvement method for gabion of ecological bank protection
By employing a finite element analysis method involving layered modeling and dynamic load application, the mechanical simulation challenge of gabion stone cages in complex riverbank environments was solved, achieving accuracy in structural stress analysis and reliability in engineering design, while balancing mechanical performance and ecological sustainability.
Patent Information
- Application Number
- CN202511712708.4
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-11-20
- Publication Date
- 2026-02-27
AI Technical Summary
Existing technologies cannot accurately simulate the mechanical properties of gabion cages in complex riverbank environments, especially their flexibility, discontinuous contact relationships, and pulsating water impact effects, resulting in a lack of quantifiable structural response analysis methods in the design.
A layered modeling method was adopted, dividing the gabion into a flexible mesh layer, a contact coupling layer, and a stone filling layer. Finite element elements and equivalent particle domain elements were used to model the layers respectively. A dynamic water impact load with time pulse characteristics was applied to the outer surface of the mesh cage, and transient finite element solution was performed to identify weak areas and make structural improvements.
It achieves accurate simulation of the stress state of gabion cages, improves the calculation accuracy of stress distribution, slip behavior and friction, provides a basis for erosion resistance design, and enhances the reliability and efficiency of engineering design through modular construction and ecological functions.
Smart Images
Figure CN121580718A_ABST
Abstract
Description
Technical Field
[0001] This invention relates to the fields of water conservancy and geotechnical engineering, and more specifically, to a finite element analysis and structural improvement method for ecological revetment gabion cages. Background Technology
[0002] Gabion cages are flexible revetment structures composed of metal mesh cages and filled stones, widely used in riverbank protection, hydraulic dams, and slope reinforcement. Because gabion cages can deform within a certain range to adapt to changes in terrain while maintaining overall stability, they possess advantages such as high permeability and good ecological adaptability. However, the mechanical properties of this structure are quite complex, and its stress process is not as continuous as that of concrete or steel structures. The interior of the gabion cage is formed by the accumulation of granular stones, and the contact, slippage, and friction between the stones constitute typical discontinuous characteristics; the outer metal mesh cage exhibits high flexibility, capable only of withstanding tensile forces but not compression. This combination of a "flexible skeleton + discrete particles" structure makes it highly nonlinear and locally inhomogeneous under external forces.
[0003] Traditional finite element analysis often employs the continuum assumption and linear material models to calculate structural stress and deformation. However, directly applying this method to gabion cages leads to calculation errors in force paths, slip behavior, and friction effects, making it difficult to accurately reflect the internal mechanical transmission laws of the structure. Furthermore, the external loads experienced by gabion cages in riverside environments are not constant static pressures but rather periodic pulsed impacts from superimposed waves, backflow, and vortices. Traditional static analysis cannot effectively capture these transient dynamic characteristics. Due to these issues, gabion cage design still largely relies on experience and on-site adjustments, lacking quantifiable structural response analysis methods. Therefore, a numerical analysis and structural improvement method that can consider flexibility, discontinuous contact relationships, and pulsed hydrodynamic impact effects is urgently needed to more accurately simulate their stress state and guide engineering design. Summary of the Invention
[0004] The technical problem to be solved by the present invention is to provide a finite element analysis and structural improvement method for ecological revetment gabion cages, so as to solve the problems mentioned in the background art.
[0005] To achieve the above objectives, the present invention adopts the following technical solution:
[0006] A finite element analysis and structural improvement method for ecological riverbank protection gabions includes the following steps:
[0007] The gabion structure is divided into a flexible mesh layer, a contact coupling layer, and a stone filling layer. The flexible mesh layer is modeled using finite element elements that only withstand tension. The stone filling layer is modeled using equivalent particle domain elements. The contact coupling layer is located between the flexible mesh layer and the stone filling layer and is used to establish the mechanical coupling relationship between the two.
[0008] Normal contact stiffness, tangential stiffness and friction coefficient parameters are set in the contact coupling layer. The top pressure, friction reaction force and slippage behavior of the stone on the wire mesh cage are described by defining nonlinear contact relationship.
[0009] Based on the non-constant impact characteristics of riverbank water flow, a dynamic water impact load with time pulse characteristics is applied to the outer surface of the flexible net cage;
[0010] Support constraints were applied to the bottom of the gabion model, and transient finite element analysis was performed to obtain the tensile stress distribution of the flexible mesh layer, the compressive stress distribution of the stone filling layer, and the frictional force and slip response of the contact coupling layer.
[0011] Based on the finite element analysis results, the high tensile stress region of the wire mesh cage, the high compression region of the stone, and the slip concentration region were identified, and targeted structural improvements and protections were carried out.
[0012] Furthermore, the finite element units of the flexible mesh cage layer are composed of rod units or membrane units that only bear tensile stress, and their nodes are connected to the corresponding nodes of the contact coupling layer.
[0013] The equivalent particle domain units of the stone filling layer are used to characterize the overall compressibility and interparticle friction characteristics of the stone accumulation by setting equivalent density, equivalent elastic modulus and Poisson's ratio.
[0014] The contact coupling layer establishes a bidirectional mechanical transmission relationship between the flexible wire mesh layer and the stone filling layer by defining node contact pairs, so that the normal contact force and the tangential friction force can interact between the two layers to achieve the coupled response of the wire mesh under tension and the stone under compression.
[0015] Furthermore, the normal contact stiffness in the contact coupling layer is used to describe the force response of the stone and the wire mesh in the contact compression direction, the tangential stiffness is used to describe the relative sliding stiffness of the contact surface along the tangential direction, and the friction coefficient is used to determine the upper limit of the friction force between the stone and the wire mesh.
[0016] When the contact displacement is in the initial micro-slip stage, the tangential reaction force increases nonlinearly with the amount of slip. When the amount of slip exceeds the set threshold, the tangential reaction force gradually tends to a stable value, so as to reflect the transformation process of the stone material to the wire mesh cage from adhesive anti-slip to frictional slip, thereby realizing the simulation of the real mechanical behavior of the contact interface.
[0017] Furthermore, the dynamic water impact load with time pulse characteristics consists of multiple continuous or intermittent short-time impact components. Each impact component has a specific peak amplitude, duration of action, and interval time, which is used to simulate the non-constant impact process of riverbank water flow under the action of eddies, waves, and backflow.
[0018] The peak amplitude of the dynamic water impact load is proportional to the square of the river flow velocity, the duration of the load is between 0.1 seconds and 2 seconds, and the interval is between 1 second and 10 seconds. By applying this pulse load to the outer surface of the flexible gabion in a time sequence, the finite element analysis can reflect the periodic impact and transient response characteristics of the water flow impact on the gabion structure.
[0019] Furthermore, the support constraints include applying fixed constraints or limiting vertical displacement to the bottom nodes of the gabion model to simulate the support relationship between the gabion and the foundation.
[0020] After the load was applied, the finite element model was analyzed using transient dynamics. The stress and displacement changes of each layer of the structure under the action of dynamic water impact load were calculated by time step integration. The tensile time history of the flexible gabion layer, the compressive stress evolution of the stone filling layer, and the response curves of friction and slip of the contact coupling layer over time were obtained to reflect the dynamic stress characteristics and structural stability of the gabion under periodic water flow impact.
[0021] Furthermore, based on the stress distribution results obtained from the finite element method, weak areas of the structure are identified: when the tensile stress value of the flexible mesh layer exceeds the set safety factor range, it is determined to be a high tensile stress area; when the compressive stress of the stone filling layer is close to the allowable compressive stress of the material, it is determined to be a high compressive stress area; when the slip displacement is concentrated or the friction force changes abruptly in the contact coupling layer, it is determined to be a slip concentration area.
[0022] Furthermore, the method also includes:
[0023] For areas with high tensile stress, tensile properties can be enhanced by increasing the diameter of the mesh wire, increasing the strength of the steel wire, or by setting reinforcement strips in local areas.
[0024] For high compression areas, compressive stress can be dispersed by selecting stones with larger particle size and higher strength or by increasing the thickness of the modules;
[0025] For areas with concentrated slippage, the interface friction can be increased by adding binding points, setting anti-slip mesh, or filling flexible pads between modules.
[0026] Furthermore, the method also includes filling the interior of the gabion with graded stones, wherein the stone size decreases progressively from bottom to top, in order to improve the packing density and drainage performance.
[0027] Furthermore, planting holes are reserved on the upper surface or side wall of the gabion, which penetrate the stone layer and are connected to the external soil for planting erosion-resistant plants with root systems, thereby achieving the synergistic function of stone stabilization and ecological greening after the revetment structure is formed.
[0028] After the revetment is built, the plant roots reinforce the stone layer by periodically maintaining and replanting the plants in the module; when the local stone has gaps due to erosion, the stone can be replenished or replaced through the reserved maintenance holes.
[0029] Furthermore, gabion stone cages are constructed using a multi-module method, formed by splicing multiple modules. The modules include modular hoisting and positioning structures, with hoisting holes or lifting rings at the four corners and pluggable positioning slots at the bottom.
[0030] During construction, pre-laid baselines and limiting devices are used to align modules, enabling adjacent modules to automatically align and form a staggered overlapping structure.
[0031] The advantages of this invention compared to existing technologies lie in its layered modeling structure—comprising a flexible mesh cage layer, a contact coupling layer, and a stone filling layer—introduced during the finite element analysis modeling stage. This overcomes the limitation of traditional continuous finite element models in reflecting the true stress behavior of discontinuous granular systems. The flexible mesh cage layer is modeled using elements that only bear tensile forces, the stone filling layer is modeled using equivalent particle domains, and the contact coupling layer is used to establish the frictional and normal contact relationship between the two, thereby achieving a realistic coupling calculation between the flexible tension and the granular compression. This method effectively solves the problems of uneven stress distribution, distorted slip behavior, and inaccurate friction calculation in traditional gabion analysis, significantly improving the realism and reliability of the stress analysis results.
[0032] This invention further incorporates the non-constant impact characteristics of riverbank flow by applying a dynamic hydrodynamic impact load with time-pulse characteristics to the outer surface of a flexible mesh cage to simulate transient impacts such as wave impact and eddy current backflow. Compared to traditional static loads, this pulsed load can capture the stress peaks and slip responses of the structure during dynamic impact, making the finite element analysis results more consistent with the actual hydrodynamic environment. The temporal evolution of tensile stress, compressive stress, and frictional slip can be obtained through transient solutions, providing data for scour-resistant design.
[0033] Furthermore, this invention proposes a structural improvement and modular construction approach based on finite element analysis results. By identifying areas of high tensile stress, high compression, and slip concentration, local reinforcement, stone optimization, and connection enhancement are implemented to achieve uniform stress distribution and improved stability. Modular hoisting and positioning structures significantly improve construction accuracy and efficiency. Through filling graded stones and planting holes, regular maintenance, and stone replenishment, continuous improvement of ecological functions and convenient maintenance of the revetment structure are achieved. The overall solution balances mechanical performance, construction efficiency, and ecological sustainability, demonstrating significant technological advancement and engineering application value. Attached Figure Description
[0034] Figure 1 This is a schematic diagram of the overall structure of the present invention;
[0035] Figure 2 This is a schematic diagram of the discretization and coupling modeling structure of the present invention;
[0036] Figure 3 This is a schematic diagram of the load and constraint application and transient output structure of the present invention;
[0037] Figure 4 This is a schematic diagram of the structural improvement and modular ecological function of the present invention. Detailed Implementation
[0038] The specific embodiments of the present invention will now be described with reference to the accompanying drawings.
[0039] In order to achieve accurate analysis and optimized design of gabion structures for ecological revetment, this invention uses finite element analysis technology to model and solve the mechanical behavior of gabions, and proposes targeted structural improvement measures based on the analysis results.
[0040] Gabion baskets are revetment structures consisting of flexible metal mesh cages filled with stones. Their mechanical behavior is complex, involving the tension of the mesh cages, the compression of the stones, and the contact friction between the two. This study aims to accurately simulate their stress characteristics.
[0041] As shown in Figures 1 and 2, the present invention divides the gabion structure into three main parts: a flexible mesh layer, a contact coupling layer, and a stone filling layer.
[0042] The flexible gabion cage layer is woven from metal wires and primarily bears tensile stress, with almost no compressive or bending forces. Therefore, finite element models designed to withstand only tensile stress are used, specifically rod or membrane elements. These elements transmit force only in the tensile direction, neglecting compressive and bending stiffness, thus reflecting the actual mechanical properties of the gabion cage material. Rod elements are suitable for simulating the axial tensile behavior of the wires, while membrane elements are suitable for describing the overall planar tensile behavior of the mesh surface. During modeling, the geometry of the gabion cage is generated based on actual design parameters, such as mesh size, wire diameter, and overall cage dimensions. For a typical gabion cage, the wire diameter is typically between 2.0 mm and 4.0 mm, and the mesh size is between 60 mm × 80 mm and 100 mm × 120 mm. Node settings correspond to the mesh intersections, ensuring that each node reflects the connection characteristics of the wires.
[0043] The stone filling layer consists of stacked stones, exhibiting particle discreteness and discontinuity. Modeling each individual stone particle directly would be computationally too intensive; therefore, equivalent particle domain elements are used for simulation. These elements characterize the overall mechanical properties of the stone stack by defining equivalent density, equivalent elastic modulus, and Poisson's ratio. The equivalent density is determined based on the stone's material and packing density, typically ranging from 1800 kg / m³ to 2500 kg / m³. The equivalent elastic modulus reflects the compressive stiffness of the stone stack, usually ranging from 50 MPa to 200 MPa, depending on the stone's strength and particle size distribution. Poisson's ratio describes the lateral deformation characteristics of the stone under compression, typically ranging from 0.2 to 0.35.
[0044] To further simulate the frictional characteristics between particles, the equivalent unit of the stone filling layer introduces an internal friction angle parameter, ranging from 30° to 45°, to reflect the shear resistance of the stone aggregate. For example, for basalt stone with a particle size of 100 mm to 300 mm, its equivalent elastic modulus can be set to 150 MPa, Poisson's ratio to 0.25, and internal friction angle to 40°, thereby accurately characterizing the compression and frictional behavior of the stone.
[0045] The contact coupling layer, located between the flexible wire mesh layer and the stone filling layer, is used to simulate the mechanical interaction between the two. The contact coupling layer establishes a bidirectional mechanical transmission relationship by defining nodal contact pairs. Each contact pair consists of a node from the wire mesh layer and a corresponding node from the stone filling layer, and the contact behavior is described by normal contact stiffness, tangential stiffness, and friction coefficient.
[0046] Normal contact stiffness is used to characterize the vertical apical pressure exerted by the stones on the wire mesh cage. It typically ranges from 1 × 10^6 N / m to 1 × 10^8 N / m, depending on the stone particle size and the stiffness of the wire mesh cage material. A higher normal stiffness can simulate the strong compressive force of the stones on the wire mesh cage.
[0047] Tangential stiffness describes the relative slip stiffness of the contact surfaces along the tangential direction, and its value ranges from 1 × 10^5 N / m to 1 × 10^7 N / m. The magnitude of tangential stiffness affects the rigidity of the slip behavior; lower tangential stiffness allows for a larger amount of slip.
[0048] The coefficient of friction determines the upper limit of friction between the stone and the wire mesh cage, typically ranging from 0.3 to 0.7, depending on the surface roughness of the wire mesh cage and the material of the stone. For example, the coefficient of friction between wire mesh and basalt stone can be set to 0.5.
[0049] The nonlinear characteristics of the contact relationship are described by a piecewise function: when the contact displacement is in the initial micro-slip stage, the tangential reaction force increases nonlinearly with the slip amount, which can be simulated using an exponential or power function model; when the slip amount exceeds a set threshold, for example, from 0.5 mm to 2 mm, the tangential reaction force tends to stabilize, equal to the product of the friction coefficient and the normal force. This nonlinear model can realistically reflect the transition process from adhesive anti-slip to frictional slip. For example, if the normal force is 1000 Newtons and the friction coefficient is 0.5, the maximum friction force is 500 Newtons, and the tangential reaction force stabilizes at this value after the slip threshold.
[0050] As shown in Figure 3, gabion cages in a riverbank environment are subjected to non-steady water flow impacts, such as wave impact, eddies, and backflow. To simulate these dynamic effects, a dynamic water impact load with time-pulse characteristics is applied to the outer surface of the flexible gabion cage. This load consists of multiple continuous or intermittent short-time impact components, each with the following characteristics:
[0051] The peak amplitude is proportional to the square of the river flow velocity, as shown in the formula: ,in Peak impact force The density of water is approximately 1000 kg / m³. For maximum flow rate, This is a proportionality coefficient, typically ranging from 0.5 to 2.0. For example, at a maximum flow velocity of 2 m / s, the peak impact force is approximately 2000 N / m².
[0052] The duration of the effect ranges from 0.1 seconds to 2 seconds, reflecting the brief impact characteristics of waves or eddies.
[0053] The interval ranges from 1 second to 10 seconds to simulate the periodic characteristics of water flow impact.
[0054] The pulsed load is applied to the nodes on the outer surface of the wire mesh cage via a time series. For example, a sinusoidal pulse function can be designed. ,in Peak amplitude, For the duration of action, For the current moment, This represents the force applied at the current moment. When the pulse is applied, the load direction is usually perpendicular to the gabion surface or in the same direction as the water flow. This load design can capture the transient impact effect of the water flow on the structure and reflect the true stress behavior of the gabion in a dynamic hydraulic environment.
[0055] To simulate the mechanical relationship between the gabion cage and the foundation, support constraints are applied to the bottom of the model. The types of constraints include:
[0056] Fixed constraints completely fix all degrees of freedom, translation, and rotation of the bottom node, and are suitable for connecting gabion cages to a rigid foundation.
[0057] Vertical displacement constraint only restricts the vertical displacement of the bottom node, allowing slight horizontal sliding, and is suitable for soft foundations or situations with some settlement.
[0058] The constraints are determined based on the actual construction environment. For example, if the gabion is placed on a concrete foundation, fixed constraints are used; if it is placed on a sandy or clay foundation, vertical displacement constraints are used, and the foundation stiffness is simulated in conjunction with the actual ground stiffness. The foundation stiffness ranges from 1×10^6 N / m to 1×10^8 N / m.
[0059] After model construction and load application, the dynamic response of the gabion cages was analyzed using transient dynamics. The solution process employed a time-step integration method, with time steps typically between 0.01 and 0.1 seconds to capture the effects of rapidly changing impact loads. The solution results include:
[0060] The tensile time history of the flexible wire mesh layer records the changes in tensile stress at each node of the mesh cage on the time axis, reflecting the peak stress and distribution pattern of the wire mesh.
[0061] The evolution of compressive stress in the stone filling layer records the change of compressive stress in the stone accumulation over time, and identifies high-compression areas.
[0062] The frictional force and slip response of the contact coupling layer are recorded, and the magnitude of the frictional force and slip displacement of the contact surface under impact load are recorded to reflect the dynamic characteristics of the interface mechanical behavior.
[0063] For example, in a typical solution, if the peak value of the dynamic water impact load is 2000 N / m² and the duration is 0.5 seconds, the maximum tensile stress in the wire mesh layer may reach 10 MPa, the maximum compressive stress in the stone layer may be 5 MPa, and the maximum slippage in the contact layer may be 1.5 mm. These data provide a basis for subsequent structural optimization.
[0064] In a further embodiment, based on the finite element analysis results, weak areas of the gabion are identified:
[0065] When the tensile stress in the wire mesh layer exceeds the safety factor range, it is identified as a high tensile stress region. The safety factor range is typically 1 / 1.5 to 1 / 2 of the material's yield strength. For example, if the yield strength of steel wire is 400 MPa, the safety threshold is 200 MPa to 267 MPa.
[0066] When the compressive stress of a rock layer approaches the material's allowable compressive stress, it is considered a high-compression zone. For example, the allowable compressive stress of basalt is 20 MPa.
[0067] When the slip displacement of the contact layer exceeds 2 mm or the friction force changes abruptly, such as rapidly decreasing from 500 Newtons to 200 Newtons, it is identified as a slip concentration area.
[0068] The identification process uses post-processing software to visualize and analyze the solution results, generating stress cloud maps, displacement cloud maps, and friction force distribution maps. For example, high tensile stress areas may appear at the top of the wire mesh cage or on the side near the impact of water flow, high compression areas are usually located in the center of the stone accumulation, and areas of concentrated slip often appear at the contact boundary between the wire mesh cage and the stone.
[0069] As shown in Figure 4, further improvements can be proposed for the identified weak areas:
[0070] Improvements can be made to areas with high tensile stress by increasing the wire diameter (e.g., from 2.7 mm to 3.4 mm), increasing the wire strength (e.g., upgrading from ordinary steel wire to high-strength steel wire, increasing the yield strength from 400 MPa to 600 MPa), or adding reinforcing strips, such as steel strips or fiber strips, to enhance tensile strength in high-stress areas. For example, adding a 100 mm wide steel strip to the top of the cage can reduce local tensile stress by approximately 20%.
[0071] In improving high-compression zones, larger-sized stones, such as granite instead of ordinary sandstone, are selected, for example, from 150 mm to 250 mm, with higher strength. Alternatively, the module thickness can be increased, for example, from 0.5 m to 0.8 m, to disperse compressive stress. For instance, increasing the stone particle size can reduce compressive stress from 5 MPa to 3 MPa.
[0072] Improvements to areas prone to slippage: Increase interfacial friction by adding binding points (e.g., 2-3 per square meter), installing anti-slip mesh (e.g., welding serrated steel strips to the inner surface of the cage), or filling the spaces between modules with flexible padding, such as polyester fiber pads 5-10 mm thick. For example, adding anti-slip mesh can increase the coefficient of friction from 0.5 to 0.7, significantly reducing slippage.
[0073] To improve the density and drainage performance of the stone filling layer, a graded stone filling method is adopted. From bottom to top, the stone particle size gradually decreases; for example, 300-400 mm stones are used at the bottom, 150-250 mm stones in the middle, and 50-100 mm stones at the top. This graded design provides structural stability through large-diameter stones, while small-diameter stones fill the gaps to increase density and improve drainage performance, reducing void formation caused by water erosion. During implementation, large-diameter stones are first laid at the bottom of the gabion, and then the filling and compaction are carried out layer by layer to ensure an overall bulk density of over 2000 kg / m³.
[0074] To achieve the ecological function of the revetment, planting holes are pre-drilled on the top surface or side walls of the gabion baskets. These holes, 50-100 mm in diameter, penetrate the stone layer and connect to the surrounding soil, facilitating the planting of roots for erosion-resistant plants such as reeds and willows. The spacing between the planting holes is 0.5-1 meter, ensuring a plant coverage rate of over 30%. After the revetment is constructed, the plants are regularly watered, fertilized, and replanted to maintain the root system's reinforcing effect on the stones. When voids appear in localized sections due to water erosion, stones are added or damaged modules are replaced through the pre-drilled maintenance holes. For example, in one revetment, planting reeds increased the stability of the stone layer by 15% and reduced the porosity by 10%.
[0075] Gabion stone cages are constructed using a multi-module splicing method, with each module typically measuring 2 meters × 1 meter × 0.5 meters. For ease of construction, lifting holes or lifting rings, 30 to 50 millimeters in diameter, are provided at the four corners of each module for convenient operation by lifting equipment. The bottom of each module has an interlocking positioning groove, 50 millimeters wide and 100 millimeters deep, ensuring precise alignment between modules. During construction, a baseline is first established, and positioning is achieved using a laser rangefinder or string line. Then, limiting devices such as steel reinforcement stakes are used to secure the module positions. Adjacent modules are joined using a staggered overlap method, with an overlap width of 100 to 200 millimeters to enhance overall stability. For example, in the construction of a 10-meter-long revetment, using five spliced modules increases construction efficiency by 30%, and controls the alignment error to within 5 millimeters.
[0076] Through the above-mentioned hierarchical modeling and dynamic analysis, this invention not only solves the limitations of traditional models in terms of the forces on discontinuous particles, but also accurately captures the transient effects of water flow pulses on the structure.
[0077] The above description is only a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any equivalent substitutions or modifications made by those skilled in the art within the scope of the technology disclosed in the present invention, based on the technical solution and inventive concept of the present invention, should be covered within the scope of protection of the present invention.
Claims
1. A finite element analysis and structural improvement method for ecological riverbank protection gabions, characterized in that, Includes the following steps: The gabion structure is divided into a flexible mesh layer, a contact coupling layer, and a stone filling layer. The flexible mesh layer is modeled using finite element elements that only withstand tension. The stone filling layer is modeled using equivalent particle domain elements. The contact coupling layer is located between the flexible mesh layer and the stone filling layer and is used to establish the mechanical coupling relationship between the two. Normal contact stiffness, tangential stiffness and friction coefficient parameters are set in the contact coupling layer. The top pressure, friction reaction force and slippage behavior of the stone on the wire mesh cage are described by defining nonlinear contact relationship. Based on the non-constant impact characteristics of riverbank water flow, a dynamic water impact load with time pulse characteristics is applied to the outer surface of the flexible net cage; Support constraints were applied to the bottom of the gabion model, and transient finite element analysis was performed to obtain the tensile stress distribution of the flexible mesh layer, the compressive stress distribution of the stone filling layer, and the frictional force and slip response of the contact coupling layer. Based on the finite element analysis results, the high tensile stress region of the wire mesh cage, the high compression region of the stone, and the slip concentration region were identified, and targeted structural improvements and protections were carried out.
2. The finite element analysis and structural improvement method for ecological revetment gabions according to claim 1, characterized in that, in, The finite element units of the flexible mesh cage layer are composed of rod units or membrane units that only bear tensile stress, and their nodes are connected to the corresponding nodes of the contact coupling layer. The equivalent particle domain units of the stone filling layer are used to characterize the overall compressibility and interparticle friction characteristics of the stone accumulation by setting equivalent density, equivalent elastic modulus and Poisson's ratio. The contact coupling layer establishes a bidirectional mechanical transmission relationship between the flexible wire mesh layer and the stone filling layer by defining node contact pairs, so that the normal contact force and the tangential friction force can interact between the two layers to achieve the coupled response of the wire mesh under tension and the stone under compression.
3. The finite element analysis and structural improvement method for ecological revetment gabions according to claim 1, characterized in that, The normal contact stiffness in the contact coupling layer is used to describe the force response of the stone and the wire mesh in the contact compression direction, the tangential stiffness is used to describe the relative sliding stiffness of the contact surface along the tangential direction, and the friction coefficient is used to determine the upper limit of the friction force between the stone and the wire mesh. When the contact displacement is in the initial micro-slipping stage, the tangential reaction force increases nonlinearly with the amount of slip. When the slip exceeds the set threshold, the tangential reaction force gradually tends to a stable value, reflecting the transformation process of the stone material to the wire mesh cage from adhesive anti-slip to frictional slip, thereby realizing the simulation of the real mechanical behavior of the contact interface.
4. The finite element analysis and structural improvement method for ecological revetment gabions according to claim 1, characterized in that, The dynamic water impact load with time pulse characteristics consists of multiple continuous or intermittent short-time impact components. Each impact component has a specific peak amplitude, duration of action, and interval time, which is used to simulate the non-constant impact process of riverbank water flow under the action of eddies, waves, and backflow. The peak amplitude of the dynamic water impact load is proportional to the square of the river flow velocity, the duration of the load is between 0.1 seconds and 2 seconds, and the interval is between 1 second and 10 seconds. By applying this pulse load to the outer surface of the flexible gabion in a time sequence, the finite element analysis can reflect the periodic impact and transient response characteristics of the water flow impact on the gabion structure.
5. The finite element analysis and structural improvement method for ecological revetment gabions according to claim 1, characterized in that, The support constraints include applying fixed constraints or limiting vertical displacement to the bottom nodes of the gabion model to simulate the support relationship between the gabion and the foundation. After the load was applied, the finite element model was analyzed using transient dynamics. The stress and displacement changes of each layer of the structure under the action of dynamic water impact load were calculated by time step integration. The tensile time history of the flexible gabion layer, the compressive stress evolution of the stone filling layer, and the response curves of friction and slip of the contact coupling layer over time were obtained to reflect the dynamic stress characteristics and structural stability of the gabion under periodic water flow impact.
6. The finite element analysis and structural improvement method for ecological revetment gabions according to claim 1, characterized in that, Weak areas in the structure are identified based on the stress distribution results obtained from the finite element method: when the tensile stress value of the flexible mesh layer exceeds the set safety factor range, it is determined to be a high tensile stress area; when the compressive stress of the stone filling layer is close to the allowable compressive stress of the material, it is determined to be a high compressive stress area; when the slip displacement is concentrated or the friction force changes abruptly in the contact coupling layer, it is determined to be a slip concentration area.
7. The finite element analysis and structural improvement method for ecological revetment gabions according to claim 1, characterized in that, The method further includes: For areas with high tensile stress, tensile properties can be enhanced by increasing the diameter of the mesh wire, increasing the strength of the steel wire, or by setting reinforcement strips in local areas. For high compression areas, compressive stress can be dispersed by selecting stones with larger particle size and higher strength or by increasing the thickness of the modules; For areas with concentrated slippage, the interface friction can be increased by adding binding points, setting anti-slip mesh, or filling flexible pads between modules.
8. The finite element analysis and structural improvement method for ecological revetment gabions according to claim 1, characterized in that, The method further includes filling the inside of the gabion with graded stones, wherein the particle size of the stones decreases gradually from bottom to top, in order to improve the packing density and drainage performance.
9. The finite element analysis and structural improvement method for ecological revetment gabion cages according to claim 1, characterized in that, Planting holes are reserved on the upper surface or side wall of the gabion. The planting holes penetrate the stone layer and are connected to the external soil. They are used to plant erosion-resistant plants with root systems, so as to achieve the synergistic function of stone stabilization and ecological greening after the revetment structure is formed. After the revetment is built, the plant roots reinforce the stone layer by periodically maintaining and replanting the plants in the module; when the local stone has gaps due to erosion, the stone can be replenished or replaced through the reserved maintenance holes.
10. The finite element analysis and structural improvement method for ecological revetment gabions according to claim 1, characterized in that, Gabion stone cages are constructed using a multi-module method, formed by splicing together multiple modules. They are equipped with modular hoisting and positioning structures, with hoisting holes or lifting rings at the four corners of the modules and pluggable positioning slots at the bottom of the modules. During construction, pre-laid baselines and limiting devices are used to align modules, enabling adjacent modules to automatically align and form a staggered overlapping structure.