Multi-scale modeling and disaster response analysis methods and systems for island and reef-water-related structures

Abstract

This invention discloses a multi-scale modeling and disaster response analysis method and system for island and reef-water-bound structures. The method includes: using a continuous medium model and a linear elastic constitutive model for the reef platform; using a continuous medium model and a Hardin-Drnevich constitutive model for the calcareous coral sand foundation, which is embedded into ABAQUS through a user-defined material subroutine and verified; using a structural equivalent medium model and an unstructured mesh for low-load-bearing areas of the water-bound structure, and a structural solid micro-model and a locally refined mesh for high-load-bearing areas; constructing the interface between the two types of models using a penalty function contact algorithm to form a full-scale three-dimensional model; employing explicit dynamic analysis to simulate the full coupling of seismic waves, reef body, and structure, as well as wave-foundation-structure coupling, outputting island and reef stress, displacement field, structural stress and plastic strain cloud maps, and damage evolution data, thereby achieving structural damage assessment and island and reef topographic evolution prediction. This invention, through multi-scale integrated modeling, achieves collaborative analysis of ultra-large geological bodies and fine structures, providing a reference for island and reef engineering.

Description

Technical Field

[0001] This invention belongs to the field of marine engineering technology, and more specifically, relates to a method and system for multi-scale modeling and disaster response analysis of island and reef-water-related structures. Background Technology

[0002] As unique marine geological formations, the safety and stability of surrounding water-related structures are crucial under natural disasters such as earthquakes and extreme waves. However, islands and reefs typically span kilometers, while water-related structures are typically meters in size, resulting in a significant size difference. Furthermore, the foundations of islands and reefs are often composed of calcareous coral sand, which possesses unique mechanical properties. Traditional modeling and analysis methods struggle to achieve a comprehensive simulation of the entire disaster response process across multiple scales. Therefore, a multi-scale integrated modeling and analysis method for island-reef-water-related structures under the influence of natural disasters is urgently needed.

[0003] In existing technologies, some patents relate to island and reef perimeter modeling and damage assessment. For example, patent document CN118608718A proposes a non-uniform mesh construction method, device, and medium suitable for island and reef perimeter modeling. Based on satellite imagery and aerial survey water depth data, it generates unstructured meshes and vertically non-uniform meshes near the shoreline for establishing a three-dimensional hydrodynamic model, improving the modeling accuracy of the island and reef perimeter terrain. Patent document CN119416595A discloses a method for predicting the damage level of island and reef complexes. By establishing a damage model and introducing random variables, it achieves a resilience assessment of the complexes' resistance to impact. These existing technologies provide local solutions from the perspectives of geographic modeling and damage assessment, respectively.

[0004] However, existing technologies still have significant limitations: CN118608718A focuses on mesh generation and terrain modeling under hydrodynamic conditions, failing to consider the dynamic response analysis of island-reef-structure coupled systems to natural disasters such as earthquakes and waves, and lacks constitutive descriptions for special geological materials such as calcareous coral sand; while CN119416595A involves damage assessment, its method relies on statistical models of building complexes and random sampling, failing to establish a true multi-scale physical simulation model and thus unable to simulate the continuous coupled process from seismic wave propagation to structural damage evolution. Furthermore, neither addresses the balance between computational efficiency and accuracy arising from the scale difference between kilometer-scale islands and reefs and meter-scale structures. Therefore, existing technologies cannot achieve integrated high-precision simulation and response prediction of island-reef-water-related structure systems under natural disasters. Summary of the Invention

[0005] To address the aforementioned deficiencies or improvement needs of existing technologies, this invention provides a multi-scale integrated modeling and analysis method for island / reef-water-related structures under natural disasters. First, a modified Hardin-Drnevich constitutive model suitable for calcareous coral sand is constructed and embedded into the ABAQUS finite element analysis platform via the user material subroutine VUMAT or UMAT interface. Then, a full-size integrated three-dimensional finite element model is established, encompassing natural island / reef geological bodies at the kilometer scale and artificial water-related structures at the meter scale. The structure further includes smaller material components such as steel reinforcement at the centimeter scale. Next, the integrated three-dimensional finite element model is meshed, with a global coarse mesh used for the island / reef region and a smaller mesh used for the surrounding water-related structures. The region employs locally refined meshes, with a mesh transition zone between coarse and refined meshes. Explicit dynamic analysis is used to apply seismic loads to the integrated three-dimensional finite element model, simulating the entire process of seismic wave propagation within the reef, reef deformation, and structural dynamic response. Extreme wave loads are applied to the wave-facing side of the water-embankment structure to obtain the integrated dynamic response results of the island-reef-water-embankment structure under the coupled action of seismic and wave forces. Finally, the integrated dynamic response results are output, including at least the stress and displacement fields of the island-reef, stress contour maps, plastic strain contour maps, and damage evolution processes of the water-embankment structure. Based on the integrated dynamic response results, the damage level of the water-embankment structure is determined, and the island-reef topographic evolution trend is predicted.

[0006] To achieve the above objectives, according to a first aspect of the present invention, a method for multi-scale modeling and self-disaster response analysis of island-reef-water-related structures is provided, comprising the following steps: S100: The Hardin-Drnevich constitutive model applicable to calcareous coral sand is embedded into ABAQUS through a user material subroutine to establish a unit model for simulation verification. S200: Construct a full-scale 3D model of the island and reef-water-bound structure and apply unstructured mesh, local refinement and penalty function contact algorithm to complete efficient finite element mesh generation and interface behavior simulation for complex terrain; S300: Explicit dynamic analysis is used to simulate the entire process coupling of seismic wave propagation, reef deformation, and structural response, as well as the entire process coupling of local extreme wave loading, coral sand foundation deformation, and structural response of water-bound structures. Typical islands and reefs are selected for numerical simulation. S400: Based on the overall response results of island and reef-water-bound structures under natural disasters, output the stress field and displacement field of the island and reef body, as well as the stress and plastic strain cloud map and damage evolution process of the water-bound structure. Based on this, determine the damage level of the water-bound structure and predict the evolution trend of island and reef topography. S500: Based on the overall response results of island and reef-water-related structures under the action of natural disasters, determine the damage level of water-related structures and predict the evolution trend of island and reef topography.

[0007] Further, step S100 includes: S110: Introducing the lower bound minimum shear modulus to describe the property that coral sand particles still have a certain load-bearing capacity after being broken, and establishing a modified model of the Hardin-Drnevich model; S120: User material subroutine based on the ABAQUS user subroutine module for developing a nonlinear dynamic constitutive model of coral sand foundation using the modified model; S130: A torsional shear test was conducted using hollow cylindrical specimens made of coral sand to complete the nonlinear dynamic analysis and verification of the coral sand foundation of the island reef.

[0008] Furthermore, the modified Hardin-Drnevich constitutive model described in step S110 introduces a minimum shear modulus. To describe the residual strength characteristics of calcareous coral sand under high shear strain, its shear modulus G is as follows: , in, , , For shear stress, For shear strain, For current shear strain, For threshold shear strain, The reference shear strain is used.

[0009] Furthermore, in step S130, before performing large-scale calculations, it is necessary to first verify the correctness of the coral sand user material subroutine. The verification process uses ABAQUS finite element software, and its steps include: S131: Establish the element model, divide the mesh into appropriate sizes, assign user-defined material properties to the elements, and correctly set the number of state variables and the initial parameters of the coral sand material. S132: Apply a fixed constraint to the bottom vertex of the coral sand unit and apply a small periodic horizontal displacement to the top vertex to simulate the shearing action of the coral sand unit. S133: Based on the simulation results, the force-displacement curves of the top vertex and nearby nodes of the coral sand element are derived. The trend of these curves is the same as that of the Hardin-Drnevich skeleton curve, which shows that the coral sand user material subroutine is correct.

[0010] Furthermore, in step S131, the model is discretized using C3D8R hexahedral reduced integral elements during the mesh generation.

[0011] Furthermore, S200 includes: the reef and the reclamation foundation are modeled as continuous solids and given a global coarse mesh size as the bearing and wave propagation medium; the revetment structure is partitioned according to the stress characteristics and damage sensitivity; the structure-foundation interface and the potential damage concentration area are the core stress area, where the reinforced concrete microstructure is retained and discretized to capture the nonlinear damage evolution of the structure and to divide it into progressively finer meshes; the structural extension area far from the critical stress parts is described by an equivalent continuous medium, so that this area can provide a reasonable stiffness contribution and force propagation path at the macro scale, while achieving the goal of controlling the degree of freedom scale. Through this method, an integrated calculation model that takes into account both the dynamic response of the macro model and the damage evolution of the micro components is established.

[0012] Furthermore, the specific steps for detailed modeling of the full-scale island-reef-waterway structure in step S200 include: S210: Simplified geographic coordinates of islands and reefs are extracted based on measured or remote sensing data, and a discrete point set is generated after coordinate transformation. ; S220: Import point clouds into SolidWorks and reconstruct a 3D island / reef model using surface tools. S230: Use geometric differentiation tools to simplify complex curved surfaces, and further design the geometric parameters of components such as revetments, breakwaters, and wharf pile foundations. Establish corresponding structural models, assign corresponding material properties, and precisely assemble each component to the corresponding position on the island / reef model using coordinates. This completes the rough model creation of a full-size integrated model of the island / reef-water-related structure.

[0013] Furthermore, after the rough model is completed, it is necessary to define the boundary conditions of the model and the interactions between the components, including: Apply bottom-fixed boundary conditions to the coral mountain reefs; A penalty function frictional contact algorithm is introduced to define the contact properties between the island / reef and the water-related structure, and to simulate the frictional and separation behavior of the coral sand foundation relative to the natural island / reef base, and the interface between the revetment / breakwater and the wharf structure and the coral sand foundation.

[0014] Furthermore, after the integrated model completes the assembly and interaction definition, it needs to be meshed, and the meshing adopts C3D8R hexahedral mesh. The mesh has multiple free nodes, which are used to accurately describe the motion state of the model during large deformation.

[0015] Furthermore, it also includes: dividing the coral sand foundation of the key calculation area into a transition zone and a calculation zone, wherein the grid size of the transition zone is between the global coarse grid and the calculation zone fine grid to pass the transition and improve the model calculation accuracy.

[0016] Furthermore, by designing different working conditions for the full-scale three-dimensional model of the island-reef-water-related structure, the study is conducted on the interaction and damage analysis of the island-reef-water-related structure under marine environmental disasters. The working conditions mainly include: seismic response time history analysis of the unstructured island-reef system, pure seismic response time history analysis of the integrated island-reef-water-related structure system, or seismic and wave coupled response time history analysis of the integrated island-reef-water-related structure system.

[0017] Furthermore, step S300, which involves numerical simulation studies of typical islands and reefs, specifically includes: S310: The system reviews relevant literature, obtains measured or remote sensing data of typical islands and reefs, and extracts simplified geographic coordinates of islands and reefs. S320: Using the methods in S200, a model is established, different working conditions are designed, and the interaction and damage analysis of island and reef-water-related structures under marine environmental disasters is studied. S330: By determining the first and second order frequencies of the island-reef-water structure system, the two main Rayleigh damping coefficients are solved and obtained, and a gravity analysis of the entire system is performed before seismic loading.

[0018] Furthermore, the different working conditions mainly include: seismic response time history analysis of unstructured island and reef systems, pure seismic response time history analysis of integrated island and reef-water-related structure systems, or seismic and wave coupled response time history analysis of integrated island and reef-water-related structure systems.

[0019] Furthermore, the seismic load is input using El Centro seismic waves at the reef base using time history methods; The extreme wave force load is obtained by comparing the wave pressure magnitude in existing hydrodynamic analysis results and using a reasonable approximation to replace the wave load condition under extreme working conditions.

[0020] Furthermore, in step S400, the damage evolution process is quantified by a damage index, and units with a damage index value of 0.99 are identified as failed units.

[0021] According to a second aspect of the present invention, a multi-scale integrated modeling and natural disaster response analysis system for island and reef-water-related structures is provided, comprising: The material constitutive model embedding module is used to embed the Hardin-Drnevich constitutive model applicable to calcareous coral sand into ABAQUS through a user material subroutine and perform simulation verification. The integrated 3D model building module is used to create full-size integrated 3D models including kilometer-level islands and reefs and meter-level water-related structures. It adopts a meshing strategy of global coarse mesh and local mesh refinement in the water-related structure area to balance computational accuracy and time cost. The Coupled Dynamics Analysis module is used to simulate the entire coupled process of seismic wave propagation, reef deformation, and structural response using explicit dynamic analysis. The wave load application module is used to apply extreme wave loads to the wave-facing side of the breakwater and obtain the integrated response results of the island-reef-water-related structure under extreme wave action. The response result output module is used to output the stress field and displacement field of the island and reef, the stress and plastic strain cloud map of the water-bound structure, and the damage evolution process. The safety assessment module is used to determine the damage level of the water-related structure and predict the evolution trend of the island and reef topography based on the overall response results of the island and reef-water-related structure under the action of natural disasters.

[0022] In summary, compared with the prior art, the above-described technical solutions conceived by this invention can achieve the following beneficial effects: 1. This invention adopts the skeleton curve of the Hardin-Drnevich model, introduces the lower bound minimum shear modulus, and, based on the user subroutine module of the large-scale general-purpose finite element software ABAQUS, develops a user material subroutine for the nonlinear dynamic constitutive model of coral sand foundation through a self-written program based on the Fortran language. This accurately describes the unique mechanical behavior of coral sand particles, which are loose, highly permeable, strain rate sensitive, and still have residual strength under large strain. It solves the significant deviation of the general soil constitutive model when applied to coral sand and provides a dedicated analysis tool for island and reef engineering.

[0023] 2. The integrated model of this invention features localized mesh refinement. The coral sand foundation of the artificial water-related structure area is modeled separately and then bound to the overall island / reef foundation. The coral sand foundation in the key calculation area is divided into a transition zone and a calculation zone. The mesh size of the transition zone is between the global coarse mesh and the fine mesh of the calculation zone, serving as a transitional measure. This process improves the model's calculation accuracy while ensuring smooth computation.

[0024] 3. This invention employs explicit dynamic analysis, based on a full-scale refined island-reef structure model. Typical seismic waves are input in the form of acceleration, while the hydrodynamic analysis and calculation results of revetments and breakwaters are introduced into the numerical simulation as load conditions. The extreme wave force harmonic loading and seismic time history loading are combined to analyze the evolution of the overall bearing capacity and local damage of the island-reef system under extreme cyclic loading, as well as the bearing capacity response time history curve and displacement response time history curve of the overall system.

[0025] 4. This invention not only outputs conventional cloud maps of stress, strain, and displacement, but also innovatively outputs the damage evolution process of the structure, and based on this, formulates methods for damage level determination and island / reef topographic evolution prediction. This elevates simulation analysis from simple "phenomenon reproduction" to a higher level of "safety assessment and predictive decision-making," providing direct and scientific theoretical basis and data support for disaster prevention design, safe operation and maintenance, and protection and reinforcement of island / reef engineering projects. Attached Figure Description

[0026] Figure 1 This is a flowchart of the multi-scale modeling and disaster response analysis method and system for island and reef-water-related structures according to an embodiment of the present invention; Figure 2 This is a schematic diagram of the multi-scale modeling and disaster response analysis method and system for island-reef-water-related structures according to an embodiment of the present invention; Figure 3 This is a flowchart illustrating the development process of the User Material Subroutine (UMAT) in an embodiment of the present invention. Figure 4 The Hardin-Drnevich constitutive framework curve is an embodiment of the present invention. Figure 5 This is a schematic diagram illustrating the verification results of the cyclic torsional shear test on the hollow coral sand drainage cylinder according to an embodiment of the present invention. Figure 6 This is a schematic diagram of the verification results of the User Material Subroutine (UMAT) unit of the present invention; Figure 7 This is a schematic diagram of an integrated island-reef structure model according to an embodiment of the present invention; Figure 8 This is a schematic diagram of the assembly and computational region division of the integrated island-reef-structure model according to an embodiment of the present invention; Figure 9 This is a schematic diagram of the interaction between islands and reefs and structures according to an embodiment of the present invention; Figure 10 This is a schematic diagram of island and reef-structure grid division according to an embodiment of the present invention; Figure 11 This is a seismic wave loading time history curve according to an embodiment of the present invention; Figure 12 This is a schematic diagram of load loading according to an embodiment of the present invention; Figure 13 The wave time history curve is an embodiment of the present invention; Figure 14 This is a seismic response cloud map of an unstructured island and reef system according to an embodiment of the present invention (a: island and reef stress distribution at 12.7s; b: island and reef displacement distribution at 12.7s). Figure 15The following are response cloud diagrams for the seismic and wave coupled time history analysis of the island-reef integrated system according to an embodiment of the present invention: (a: island displacement distribution at 12.7s; b: sand-filled foundation displacement distribution at 12.7s; c: revetment and sand-filled foundation displacement distribution at 12.7s; d: revetment stress distribution at 12.7s; e: revetment displacement distribution at 12.7s; f: revetment compressive damage at 50s; g: revetment tensile damage at 50s). Figure 16 The displacement response time history curves of the unstructured islands and reefs and the island-reef-structure integrated system according to an embodiment of the present invention under the coupled action of earthquake and wave. Figure 17 The time history curves of the reaction force response of the unstructured island and reef and the island-reef-structure integrated system under the coupled action of earthquake and wave are shown in the embodiments of the present invention. Detailed Implementation

[0027] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention. Furthermore, the technical features involved in the various embodiments of this invention described below can be combined with each other as long as they do not conflict with each other.

[0028] like Figure 1 and Figure 2 As shown, this embodiment of the invention provides a multi-scale integrated modeling and analysis method for island and reef-water-related structures under the influence of natural disasters, including the following steps: S100: The Hardin-Drnevich constitutive model for calcareous coral sand is embedded into ABAQUS via the User Material Subroutine (UMAT) through FORTRAN programming. Viscoelastic-plastic dynamic constitutive models for sandy media can balance computational efficiency and accuracy. Commonly used skeleton curve forms include the Hardin-Drnevich model, the Davidenkov model, and the Matasovic model. Hysteresis rules are generally constructed using the Masing criterion. Considering the loose particle structure, high permeability, and strain rate sensitivity of coral sand, and its ability to retain load-bearing capacity even under large deformations, this study focuses on the mechanical properties of calcareous coral sand. Based on the Hardin-Drnevich constitutive model theory, a customized programming approach using the FORTRAN programming language was employed to transform the model into computational logic recognizable by the finite element software ABAQUS. Subsequently, by developing a user material subroutine (VUMAT), the completed constitutive model code was embedded into the ABAQUS software. This allows it to accurately reflect the stress-strain relationship and other mechanical behaviors of calcareous coral sand under complex loads in subsequent numerical simulations, providing realistic material mechanics model support for the dynamic response analysis of islands, reefs, and water-related structures.

[0029] S200: Establish a full-size integrated 3D model including kilometer-scale islands and reefs and meter-scale water-related structures; adopt a meshing strategy of global coarse mesh and local mesh refinement in water-related structure areas to balance computational accuracy and time cost; Based on the geometric parameters of actual engineering scenarios, a full-size three-dimensional integrated finite element model was established, encompassing kilometer-scale island and reef topography and meter-scale water-related structures. This ensures the model can fully represent the spatial relationship and overall morphology of the islands and structures. In the mesh generation stage, a differentiated strategy was adopted: a global coarse mesh was used for the entire island and reef area to reduce the amount of computational data; while for the water-related structures and their surrounding key stress areas, local mesh refinement was performed to improve the computational accuracy in those areas. This combination of coarse and fine mesh generation effectively balances computational accuracy and time cost while ensuring the accuracy of the simulation results, thus improving simulation efficiency.

[0030] S300: Employs explicit dynamics to simulate the entire coupled process of seismic wave propagation, reef deformation, and structural response. The explicit dynamics method in ABAQUS was used to simulate the multiphysics coupling process under seismic loading. A typical seismic wave was selected, and the acceleration time history was applied to the bottom of the reef as a base input. The system damping coefficient was determined using a Rayleigh damping model. Before the seismic analysis, gravity initialization of equilibrium stress was performed. The ABAQUS / Explicit solver was used to perform a full-process coupled analysis of seismic wave propagation, reef deformation, and structural response, thus fully reconstructing the dynamic interaction mechanism between the island / reef and the water-related structure under seismic loading.

[0031] S400: Apply extreme wave loads to the wave-facing side of the breakwater and obtain the integrated response results of the island-reef-water-related structure under extreme wave action; In the established three-dimensional model, based on the hydrodynamic analysis results, the extreme wave load is simplified to a harmonic pressure time history with an amplitude of 0.04 MPa. This wave load is applied to the wave-facing surface of the breakwater. Combined with the applied seismic excitation, wave-seismic multi-hazard coupled loading is achieved. On this basis, the overall response results of the island and reef topography and water-related structures under extreme wave load are obtained, including the stress state and deformation characteristics of both, providing data support for subsequent damage assessment.

[0032] S500: Outputs the stress field and displacement field of islands and reefs, as well as the stress and plastic strain cloud maps and damage evolution process of water-bound structures; After the simulation is completed, time history response data of the whole domain and key local parts are extracted, including the stress field distribution and displacement field distribution of the island and reef, and stress and displacement distribution cloud maps of the reef are generated. At the same time, stress distribution cloud maps and plastic strain cloud maps of the water-crossing structure are output, as well as the damage evolution process of the structure under load. Units with damage values ​​of 0.99 are judged as failures, and the damage area and development path are displayed intuitively.

[0033] S600: Based on the overall response results of island and reef-water-related structures under the action of natural disasters, determine the damage level of water-related structures and predict the evolution trend of island and reef topography.

[0034] Based on the overall response results of island and reef-water-related structures under the aforementioned natural disasters, and according to stress, plastic strain, and damage distribution, combined with relevant engineering specifications and damage assessment standards, the degree of damage to the water-related structures is quantitatively analyzed, and the structural damage is classified into minor, moderate, and severe levels. At the same time, based on the stress and displacement variation patterns of the island and reef and the evolution trend of topographic features, the evolution direction of the island and reef topography and the possible geological disasters under subsequent natural loads are predicted, providing a decision-making basis for the design optimization and disaster prevention and mitigation of island and reef engineering.

[0035] like Figure 3 As shown, this study adopts a modified Hardin-Drnevich model, introducing a lower bound minimum shear modulus. Based on the user subroutine module of the large-scale general-purpose finite element software ABAQUS, a user material subroutine for the nonlinear dynamic constitutive model of coral sand foundation was developed using a self-written program in Fortran. By calling this subroutine in ABAQUS, the nonlinear dynamic analysis of the coral sand foundation on the island reef was verified.

[0036] To describe the nonlinear principal curve under monotonic loading conditions, Hardin and Drnevicch proposed a hyperbolic shear strain-stress equation. This study selects the Hardin-Drnevich model as the framework for the skeleton curve, and its basic form is as follows: , in, These are shear stress, shear strain, and initial shear modulus, respectively. The reference shear strain characterizes the modulus decay rate. Based on the Hardin-Drnevich skeleton curve, a viscoelastic-plastic model incorporating the hysteresis curve under Masing's rule response cyclic loading can effectively simulate the dynamic response of the foundation soil. The initial tangential shear modulus during the unloading stage is... The Hardin-Drnevich skeleton curve is magnified to form an unloading-reloading curve, as shown below: , Therefore, under constant amplitude cyclic loading, the loading / unloading reversal point is located at Combining the contents of the two formulas above, when the shear strain... Much larger At this point, the shear modulus approaches zero, which is clearly unreasonable. Therefore, a minimum shear modulus is introduced into the constitutive model of coral sand to describe the property that coral sand particles still possess a certain load-bearing capacity after breakage. The modified expression is as follows: , The shear modulus during the unloading-reloading phase can also be expressed as: , .

[0037] The parameters involved have been calibrated using hollow cylindrical cyclic torsion shear tests in relevant literature. Torsion shear tests were conducted using hollow cylindrical specimens made of coral sand, and the verification results are as follows: Figure 5 As shown, the corrected Hardin-Drnevich skeleton curve is as follows: Figure 4 As shown.

[0038] like Figure 6As shown, before performing large-scale calculations, it is necessary to verify the correctness of the coral sand user material subroutine. The verification process uses ABAQUS finite element software. An element model is established, with appropriate mesh sizes and a C3D8R hexahedral mesh selected as the mesh type. User-defined material properties are assigned to the elements, and the number of state variables and initial parameters of the coral sand material are correctly set. Fixed constraints are applied to the bottom vertices of the coral sand elements, and small periodic horizontal displacements are applied to the top vertices to simulate shear forces on the coral sand elements. The force-displacement curves for the top vertices and nearby nodes of the coral sand elements are derived from the simulation results. Their trends are the same as the Hardin-Drnevich skeleton curves, indicating that the coral sand user material subroutine is correct.

[0039] like Figures 7-9 As shown, natural islands and reefs are generally characterized by their enormous size and complex shapes, reaching the kilometer level, while large artificial water-related structures on these islands and reefs are only a few hundred meters high, with their components measuring only meters. Therefore, this study utilizes geometric partitioning tools to simplify complex curved surfaces, thereby achieving full-size modeling of islands and reefs that include their geometric shapes. Considering that the reef body is formed by the accumulation of large amounts of coral sand over many years, and its base is tightly bonded to the seabed rock, it typically does not move. Therefore, a bottom-fixed boundary condition is applied to the coral mountain reef. During the development of island and reef engineering projects, it is necessary to vibratory compaction of the loose coral sand to ensure that the coral sand foundation has sufficient bearing capacity. The compacted coral sand foundation has a tight contact with the island and reef base. Artificial water-related structures are usually located on the coral sand foundation and are tightly bonded to it. Therefore, frictional contact is adopted between the compacted coral sand foundation and the island and reef base, and between the artificial structures and the coral sand foundation. A penalty function frictional contact algorithm is introduced to define the contact properties between islands / reefs and water-related structures, and to simulate the frictional and separation behavior of the coral sand foundation relative to the natural island / reef base, and the interface between the revetment / breakwater and the wharf structure and the coral sand foundation.

[0040] This study extracts simplified geographic coordinates of islands and reefs from measured or remote sensing data, and generates discrete point sets after coordinate transformation. Point clouds are imported into SolidWorks, and a 3D island and reef model is reconstructed using NURBS surface tools, then exported in STEP format. The STEP file is imported into ABAQUS, and complex surfaces are simplified using geometric partitioning tools, thus achieving a full-size model of the island and reef containing its geometric shapes. Further, the geometric parameters of components such as breakwaters and wharf piles are designed, corresponding structural models are established, and corresponding material properties are assigned. Each component is precisely assembled to its corresponding position in the island and reef model using coordinates, completing the rough creation of a full-size integrated model of the island and reef-water-related structure.

[0041] After completing the rough model, the next step is to define the boundary conditions and interactions between components. The reef body is formed by the accumulation of large amounts of coral sand over many years, and its base is tightly bonded to the seabed rock, typically remaining stationary. Therefore, a bottom-fixed boundary condition is applied to the coral mountain reef. During the development of the reef project, the loose coral sand needs to be vibratory compacted to ensure sufficient bearing capacity of the coral sand foundation. The compacted coral sand foundation is in close contact with the reef body. Artificial water-related structures are usually located on and tightly bonded to the coral sand foundation. Therefore, frictional contact is adopted between the compacted coral sand foundation and the reef body, and between artificial structures and the coral sand foundation. A penalty function frictional contact algorithm is introduced to define the contact properties between the reef and the water-related structures, simulating the friction and separation behavior of the coral sand foundation relative to the natural reef base, and the interfaces between the breakwater and the wharf structure and the coral sand foundation.

[0042] like Figure 10 As shown, after the integrated model completes assembly and interaction definition, mesh generation is required. During mesh generation, the reef, foundation, and structure all utilize 3D eight-node reduced integral solid elements (C3D8R hexahedral meshes), while mesoscopic components such as reinforcing steel utilize 2-node 3D truss elements (T3D2). The C3D8R hexahedral mesh has 8 free nodes, accurately describing the model's motion state during large deformations, while the T3D2 truss elements accurately describe the stress behavior of the reinforcing steel. Due to the model's complexity, computational efficiency and accuracy must be comprehensively considered during mesh generation. The kilometer-scale size of the island / reef model is enormous compared to the water-bound structure. Simply prioritizing computational accuracy would result in a massive number of meshes, which current computing power struggles to handle. If the mesh size is increased, the entire water-bound structure would consist of only a few meshes, making it difficult to represent the deformation and damage state of the water-bound structure under disaster conditions. To address this issue, this study implemented local mesh refinement. The safety concerns for areas with artificial water-related structures are significantly higher than those for ordinary island and reef areas. Therefore, the coral sand foundations of these key calculation areas are modeled separately and then bound to the overall island and reef foundation. Furthermore, the coral sand foundations of these key calculation areas are divided into a transition zone and a calculation zone. The mesh size of the transition zone falls between the global coarse mesh and the fine mesh of the calculation zone, serving as a transitional layer. This approach improves the model's calculation accuracy while ensuring smooth computation.

[0043] The system consulted relevant literature, obtained typical measured or remote sensing data of islands and reefs, and extracted simplified geographic coordinates of the islands and reefs. A model was established using the methods in S200, and different working conditions were designed to study the interaction and failure analysis of island-reef-water-related structures under marine environmental disasters. The working conditions mainly included seismic response time history analysis of an unstructured island-reef system, pure seismic response time history analysis of an integrated island-reef-water-related structure system, and seismic and wave coupled response time history analysis of an integrated island-reef-water-related structure system. By determining the first and second order frequencies of the island-reef-water-related structure system, two main Rayleigh damping coefficients were solved and obtained, and a gravity analysis of the entire system was performed before seismic loading.

[0044] Rayleigh damping is a damping model widely used in finite element dynamic analysis. It assumes that the damping matrix C is a linear combination of the mass matrix M and the stiffness matrix K. , Where α is the mass-related damping coefficient; β is the stiffness-related damping coefficient. Before seismic load analysis, modal analysis, also known as frequency analysis, is performed on the integrated "island-reef-waterway structure" model that has been subjected to gravity and reached static equilibrium. From the numerous extracted frequencies, the two frequencies that contribute most to the system's dynamic response are selected, namely the first-order frequency and the second-order frequency. Based on the material properties, a reasonable damping ratio is determined. For systems composed of geotechnical materials (such as calcareous coral sand) and concrete structures, the damping ratio is typically between 2% and 5%. Rayleigh damping provides the specified damping ratio ξ precisely at the two selected frequency points (first-order frequency i and second-order frequency j), calculated as follows: , , Assuming the damping ratio is the same at both frequency points, that is The above system of equations can then be simplified to: , , Solving this system of equations simultaneously will yield the mass damping coefficient. and stiffness damping coefficient The calculation formula is as follows: , , The seismic load was input using El Centro seismic waves at the reef base, and the seismic load time history curve is shown below. Figure 11 As shown.

[0045] like Figure 12 and Figure 13As shown, for extreme wave force loads, the wave pressure magnitude in existing hydrodynamic analysis results is compared with a reasonable approximation to replace the wave load conditions under extreme conditions. To unify the load conditions, the maximum wave load pressure is determined to be 0.04 MPa, and the irregular wave force is replaced by a harmonic cyclic pressure, with cyclic pressure applied to the wave-facing surface of the revetment.

[0046] Using explicit dynamic analysis, the dynamic response of an island-reef structure under marine environmental disaster loads is simulated, extracting stress time histories, plastic strain distribution, and cumulative displacement at key locations. During the calculation, damage values ​​are coupled with the elastic modulus in the macroscopic elastoplastic constitutive model, with element yielding, softening, and failure occurring through elastic modulus degradation. The coupling relationship between damage and elastic modulus is utilized to update the elastic modulus of each element, realizing damage propagation and development. Elements with damage reaching 0.99 are considered failed elements. When studying the ultimate bearing capacity of the structure after cyclic loading, to improve computational efficiency, the damage within one cycle of wave cyclic loading is magnified by 100 times during the damage accumulation stage to simulate the structural damage after 100 cycles (assuming the weekly load and damage are consistent).

[0047] like Figure 14 As shown in the time history analysis of the seismic response of the unstructured island and reef system, when the seismic wave acceleration amplitude reaches its maximum (12.7s), the stress concentration of the unstructured island and reef mainly occurs at the edge of the reef body and the edge of the reef foundation. This indicates that under seismic action, the slope area of ​​the island and reef is prone to large deformation, leading to structural collapse and failure in this area. The displacement cloud map shows that under seismic action, the maximum displacement of the island and reef is located at the edges of both sides of the reef foundation. Compared with the reef area, the island slope is more prone to large deformation and failure during the disaster.

[0048] like Figure 15As shown in the time history analysis of the earthquake and wave coupled response of the island-reef integrated system, when the earthquake wave acceleration amplitude reaches its maximum (12.7s), the displacement cloud map shows that under earthquake action, the maximum displacement of the island-reef is located at the foundation of the reef where the revetment and other structures are located. Compared with other locations, the area where the structures on the revetment are located is more susceptible to earthquake loads and large deformations. Due to the simultaneous action of extreme wave loads, the sand-filled foundation at the bottom of the revetment slips significantly. Due to the coupling effect of strong earthquake and strong waves, a large number of cracks are generated in the weak sections of the revetment structure. The damage evolution rate increases from slow to fast, and some embedded steel bars undergo large deformations, causing large-area damage to the revetment. Therefore, when the coupling effect of strong waves and earthquake reaches 12.7s, the revetment has been severely damaged. When the earthquake loading time history reaches 50s, the contact area between the revetment and the reef is basically completely destroyed, and due to the coupling effect of strong waves and earthquake, a large crack is generated at the bottom center of the revetment under its own gravity. At this point, the stress concentration area of ​​the integrated island-reef-structure model is located at the bottom of the sand-filled foundation of the revetment, indicating that this location is the weakest area of ​​the entire system. In actual engineering, the damage caused by seismic action to the revetment and its foundation area is obvious.

[0049] like Figure 16 and Figure 17 As shown, the reaction force and displacement time history curves of the unstructured island and the integrated island-reef-structure model under the coupled action of earthquake and extreme waves were compared. The results show that in the early stage of the earthquake, the two are almost completely consistent. However, in the later stage of loading, the unstructured island and reef under the earthquake caused a certain excessive displacement, indicating that the reef foundation was in a plastic state at this time and there was plastic deformation, which prevented the overall displacement evolution from approaching zero. According to the comparison of the reaction force curves, due to the presence of the structure, the bearing capacity of the integrated island-reef-structure system under the coupled action of earthquake and extreme wave forces was weakened to a certain extent. Considering that the plastic deformation of the structure caused a certain amount of energy dissipation, and that the gradual destruction of the structure caused a certain reduction in the superload of the reef foundation, the overall system shear force decreased compared with the unstructured state.

[0050] This invention provides a cross-scale integrated analysis method for island and reef structures, capable of jointly analyzing ultra-large geological bodies and fine structures, obtaining natural disaster response results from an integrated model, and providing a reference for island and reef engineering. The cross-scale integrated calculation of island and reef structures in this invention has significant engineering practical value. This method can both perform local damage calculation and assessment of superstructures such as revetments on islands and reefs, and effectively achieve a comprehensive analysis of the load-bearing capacity and safety of the islands and reefs themselves.

[0051] Those skilled in the art will readily understand that the above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A method for multi-scale modeling and self-disaster response analysis of island / reef-water-related structures, characterized in that, Includes the following steps: S100: The Hardin-Drnevich constitutive model applicable to calcareous coral sand is embedded into ABAQUS through a user material subroutine to establish a unit model for simulation verification. S200: Construct a full-scale 3D model of the island and reef-water-bound structure and apply unstructured mesh, local refinement and penalty function contact algorithm to complete efficient finite element mesh generation and interface behavior simulation for complex terrain; S300: Explicit dynamic analysis is used to simulate the entire process coupling of seismic wave propagation, reef deformation, and structural response, as well as the entire process coupling of local extreme wave loading, coral sand foundation deformation, and structural response of water-bound structures. Typical islands and reefs are selected for numerical simulation. S400: Based on the overall response results of island and reef-water-bound structures under natural disasters, output the stress field and displacement field of the island and reef body, as well as the stress and plastic strain cloud map and damage evolution process of the water-bound structure. Based on this, determine the damage level of the water-bound structure and predict the evolution trend of island and reef topography. S500: Based on the overall response results of island and reef-water-related structures under the action of natural disasters, determine the damage level of water-related structures and predict the evolution trend of island and reef topography.

2. The method and system for multi-scale modeling and disaster response analysis of island-reef-water-related structures according to claim 1, characterized in that, Step S100 includes: S110: Introducing the lower bound minimum shear modulus to describe the property that coral sand particles still have a certain load-bearing capacity after being broken, and establishing a modified model of the Hardin-Drnevich model; S120: User material subroutine based on the ABAQUS user subroutine module for developing a nonlinear dynamic constitutive model of coral sand foundation using the modified model; S130: A torsional shear test was conducted using hollow cylindrical specimens made of coral sand to complete the nonlinear dynamic analysis and verification of the coral sand foundation of the island reef.

3. The method and system for multi-scale modeling and disaster response analysis of island-reef-water-related structures according to claim 2, characterized in that, The modified Hardin-Drnevich constitutive model described in step S110 introduces a minimum shear modulus. To describe the residual strength characteristics of calcareous coral sand under high shear strain, its shear modulus G is as follows: ， in, , , For shear stress, For shear strain, For current shear strain, For threshold shear strain, The reference shear strain is used.

4. The method and system for multi-scale modeling and disaster response analysis of island-reef-water-related structures according to claim 2, characterized in that, In step S130, before performing large-scale calculations, it is necessary to first verify the correctness of the coral sand user material subroutine. The verification process uses ABAQUS finite element software, and the steps include: S131: Establish the element model, divide the mesh into appropriate sizes, assign user-defined material properties to the elements, and correctly set the number of state variables and the initial parameters of the coral sand material. S132: Apply a fixed constraint to the bottom vertex of the coral sand unit and apply a small periodic horizontal displacement to the top vertex to simulate the shearing action of the coral sand unit. S133: Based on the simulation results, the force-displacement curves of the top vertex and nearby nodes of the coral sand element are derived. The trend of these curves is the same as that of the Hardin-Drnevich skeleton curve, which indicates that the coral sand user material subroutine is correct.

5. The method and system for multi-scale modeling and disaster response analysis of island-reef-water-related structures according to claim 4, characterized in that, In step S131, the model is discretized using C3D8R hexahedral reduced integral elements during the mesh generation.

6. The method and system for multi-scale modeling and disaster response analysis of island and reef-water-related structures according to any one of claims 1-5, characterized in that, S200 includes: the reef and the dredged foundation are modeled as continuous solids and given a global coarse mesh size, serving as the load-bearing and wave propagation medium. The revetment structure is divided into zones based on its stress characteristics and damage sensitivity. The structure-foundation interface and the area with concentrated potential damage are designated as the core stress zone, where the reinforced concrete microstructure is retained and discretized to capture the nonlinear damage evolution of the structure while also dividing it into progressively finer meshes. The structural extension zone far from the critical stress points is described using an equivalent continuous medium, enabling this region to provide a reasonable stiffness contribution and force propagation path at the macroscopic scale, while also controlling the degree of freedom. This method establishes an integrated computational model that takes into account both the dynamic response of the macroscopic model and the damage evolution of the microscopic components.

7. The method and system for multi-scale modeling and disaster response analysis of island-reef-water-related structures according to claim 6, characterized in that, Step S200, which involves detailed modeling of the full-scale island-reef-waterway structure, includes the following specific steps: S210: Simplified geographic coordinates of islands and reefs are extracted based on measured or remote sensing data, and a discrete point set is generated after coordinate transformation. ; S220: Import point clouds into SolidWorks and reconstruct a 3D island / reef model using surface tools. S230: Use geometric differentiation tools to simplify complex curved surfaces, and further design the geometric parameters of components such as revetments, breakwaters, and wharf pile foundations. Establish corresponding structural models, assign corresponding material properties, and precisely assemble each component to the corresponding position on the island / reef model using coordinates. This completes the rough model creation of a full-size integrated model of the island / reef-water-related structure.

8. The method and system for multi-scale modeling and disaster response analysis of island-reef-water-related structures according to claim 7, characterized in that, After the rough model is completed, it is necessary to define the boundary conditions of the model and the interactions between the components, including: Apply bottom-fixed boundary conditions to the coral mountain reefs; A penalty function frictional contact algorithm is introduced to define the contact properties between the island / reef and the water-related structure, and to simulate the frictional and separation behavior of the coral sand foundation relative to the natural island / reef base, and the interface between the revetment / breakwater and the wharf structure and the coral sand foundation.

9. The method and system for multi-scale modeling and disaster response analysis of island-reef-water-related structures according to claim 8, characterized in that, After the integrated model completes the assembly and interaction definition, it needs to be meshed. All meshes are generated using C3D8R hexahedral meshes. The mesh has multiple free nodes, which are used to accurately describe the motion state of the model during large deformation.

10. The method and system for multi-scale modeling and disaster response analysis of island-reef-water-related structures according to claim 9, characterized in that, Also includes: The coral sand foundation, which is the key calculation area, is divided into a transition zone and a calculation zone. The grid size of the transition zone is between the coarse grid of the global grid and the fine grid of the calculation zone, which is used to pass the transition and improve the calculation accuracy of the model.

11. The method and system for multi-scale modeling and disaster response analysis of island-reef-water-related structures according to any one of claims 1-5, characterized in that, By designing different working conditions on the full-scale three-dimensional model of the island-reef-water-related structure, this study investigates the interaction and damage analysis of the island-reef-water-related structure under marine environmental disasters. The working conditions mainly include: seismic response time history analysis of the unstructured island-reef system, pure seismic response time history analysis of the integrated island-reef-water-related structure system, or seismic and wave coupled response time history analysis of the integrated island-reef-water-related structure system.

12. The method and system for multi-scale modeling and disaster response analysis of island and reef-water-related structures according to any one of claims 1-5, characterized in that, Step S300, specifically the numerical simulation study of typical islands and reefs, includes: S310: The system reviews relevant literature, obtains measured or remote sensing data of typical islands and reefs, and extracts simplified geographic coordinates of islands and reefs. S320: Using the methods in S200, a model is established, different working conditions are designed, and the interaction and damage analysis of island and reef-water-related structures under marine environmental disasters is studied. S330: By determining the first and second order frequencies of the island-reef-water structure system, the two main Rayleigh damping coefficients are solved and obtained, and a gravity analysis of the entire system is performed before seismic loading.

13. The method and system for multi-scale modeling and disaster response analysis of island-reef-water-related structures according to claim 12, characterized in that, The different working conditions mainly include: seismic response time history analysis of unstructured island and reef systems, pure seismic response time history analysis of integrated island and reef-water-related structure systems, or seismic and wave coupled response time history analysis of integrated island and reef-water-related structure systems.

14. The method and system for multi-scale modeling and disaster response analysis of island-reef-water-related structures according to claim 13, characterized in that, The seismic load was input using El Centro seismic waves at the reef base; The extreme wave force load is obtained by comparing the wave pressure magnitude in existing hydrodynamic analysis results and using a reasonable approximation to replace the wave load condition under extreme working conditions.

15. The method and system for multi-scale modeling and disaster response analysis of island and reef-water-related structures according to any one of claims 1-5, characterized in that, In step S400, the damage evolution process is quantified by a damage index, and units with a damage index value of 0.99 are identified as failed units.

16. A multi-scale integrated modeling and natural disaster response analysis system for island / reef-water-related structures, characterized in that, include: The material constitutive model embedding module is used to embed the Hardin-Drnevich constitutive model applicable to calcareous coral sand into ABAQUS through a user material subroutine and perform simulation verification. The integrated 3D model building module is used to create full-size integrated 3D models including kilometer-level islands and reefs and meter-level water-related structures. It adopts a meshing strategy of global coarse mesh and local mesh refinement in the water-related structure area to balance computational accuracy and time cost. The coupled dynamic analysis module is used to simulate the entire process of seismic wave propagation, reef deformation, and structural response using explicit dynamic analysis. The wave load application module is used to apply extreme wave loads to the wave-facing side of the breakwater and obtain the integrated response results of the island-reef-water-related structure under extreme wave action; The response result output module is used to output the stress field and displacement field of the island and reef, the stress and plastic strain cloud map of the water-crossing structure, and the damage evolution process. The safety assessment module is used to determine the damage level of the water-related structure and predict the evolution trend of the island and reef topography based on the overall response results of the island and reef-water-related structure under the action of natural disasters.

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