Shield segment heterogeneous modeling crack and limit simulation method

Abstract

The invention discloses a shield segment heterogeneous modeling crack and limit simulation method. The method comprises the following steps: constructing an aggregate three-dimensional model database; generating a heterogeneous aggregate accumulation model; establishing a concrete shield segment three-dimensional model; defining a model material constitutive relation and a damage criterion; setting an equivalent field staged loading working condition and a boundary condition; grid division and nonlinear static simulation solution are carried out; and constructing a crack response monitoring and output module, and executing judgment of a structure limit state. High-precision construction and multi-stage loading simulation of a shield segment model are realized by reconstructing a concrete microstructure and steel bar arrangement information and combining a field loading force value and a boundary condition; and a nonlinear material constitutive and damage evolution criterion is introduced, the whole-process response of the crack is captured, a limit state criterion is set, and automatic identification and damage form judgment of the bending resistance limit load are completed. According to the method, a technical path capable of being popularized is provided for shield segment structure performance evaluation, ultimate bearing prediction and a crack control strategy.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of geotechnical engineering, in particular to a shield segment crack evolution and limit state simulation method based on heterogeneous material modeling. BACKGROUND

[0002] With the rapid growth of urban underground space development and the demand for shield tunnel construction under complex geological conditions, the bending resistance of shield segment structure, as an important force component of tunnel main body, is crucial to ensure the long-term stability and construction safety of tunnel structure. Especially under complex working conditions such as deep burial, high water pressure, asymmetric load or insufficient local surrounding rock support capacity, segment structure often faces large bending moment, which easily leads to crack initiation, expansion and even failure, becoming an important hidden danger restricting the service life and function of shield tunnel.

[0003] In current engineering practice, the bending resistance analysis of shield segment mostly relies on linear elastic assumption or equivalent homogeneous material modeling method, ignoring the real aggregate distribution inside concrete, spatial structure of steel bars and mesoscopic damage mechanism in the process of crack development, resulting in that the simulation results cannot truly reflect the nonlinear response and crack evolution law of the structure. In addition, although some researches introduce crack damage models, they lack benchmarking and verification with field loading tests, and the prediction accuracy of crack propagation path and bearing limit is low, which limits their application value in engineering design and quality evaluation.

[0004] On the other hand, most of the existing shield segment tests use whole ring structure loading or homogeneous beam simplified model, which is difficult to analyze the mechanical properties and weakening characteristics of standard block elements under local loading conditions, and lacks targeted research on the response law of segment crack prone areas in actual construction. Especially in the aspect of numerical modeling considering the characteristics of heterogeneous materials and real loading path, there is no mature and reliable method system.

[0005] Therefore, there is an urgent need for a shield segment heterogeneous modeling crack and limit simulation method that integrates heterogeneous modeling, real loading benchmarking and crack response analysis. SUMMARY

[0006] The present application aims to overcome the shortcomings of the prior art and provide a shield segment heterogeneous modeling crack and limit simulation method, which can truly restore the crack evolution and damage mechanism of segment in the bending process and realize high-precision simulation evaluation of the ultimate bearing capacity of the structure.

[0007] To achieve the above-mentioned purpose, the present application provides a shield segment heterogeneous modeling crack and limit simulation method, comprising the following steps:

[0008] Step 1, constructing the aggregate three-dimensional model database: collecting two-dimensional images of multiple aggregate samples, and converting the two-dimensional images of the multiple aggregate samples into aggregate three-dimensional models one by one through the voxelization method, and saving to the aggregate three-dimensional model database;

[0009] Step 2, generating a non-homogeneous aggregate accumulation model: creating a real aggregate three-dimensional accumulation model containing multiple gradations and irregularly shaped aggregates based on the multiple aggregate three-dimensional models generated in step S1;

[0010] Step 3, establishing a refined model of the concrete shield segment by using a three-dimensional modeling method, constructing the segment structure according to the design size and setting bolt holes and grouting holes, and embedding a reinforcement mesh and aggregate distribution in the model to truly reflect the internal structural characteristics of the segment;

[0011] Step 4, defining the nonlinear constitutive relationship of the concrete matrix, the elastic-plastic constitutive relationship of the steel material, and the material parameters of the non-homogeneous aggregate, respectively, and setting key output indicators such as damage variable and equivalent plastic strain for the concrete matrix material to monitor the crack initiation, propagation, and penetration behavior of the concrete during the loading process;

[0012] Step 5, setting equivalent field grading loading conditions and boundary conditions: according to the field bending resistance test conditions, applying equivalent grading loads to the segment in the model, and setting boundary constraints for the model;

[0013] Step 6, mesh division and nonlinear static simulation solution: after the loading and boundary condition settings are completed, the model is meshed, the nonlinear static analysis module is started, and the pre-set load is applied step by step;

[0014] Step 7, setting and calling the crack response monitoring and output module, and executing the limit state determination of the structure.

[0015] Further, the step 1 is specifically:

[0016] Step S1.1, image acquisition of multiple aggregate samples is performed through multi-view image acquisition and reconstruction technology, and multiple aggregate two-dimensional section images are obtained; the multiple aggregate two-dimensional section images collected are sequentially subjected to image preprocessing operations;

[0017] Step S1.2, using interlayer registration and reconstruction algorithm, the preprocessed aggregate two-dimensional images are stacked according to the set vertical interlayer spacing to generate corresponding three-dimensional voxel matrix models; the initial generated voxel number is interpolated and completed, and the surface smoothing treatment is finally obtained to obtain the aggregate three-dimensional model with real geometric characteristics;

[0018] Step S1.3, the generated aggregate three-dimensional model is classified and archived according to the particle size gradation, shape characteristics and volume information, and is uniformly stored in the aggregate three-dimensional model database.

[0019] Further, the step 2 is specifically:

[0020] Step 2.1, according to the design size of the concrete shield segment, set the generation domain of the aggregate in the discrete element software;

[0021] Step 2.2, set the porosity and aggregate grading radius range of the aggregate inside the segment, and generate circular aggregate models of different gradings in the aggregate generation domain through the particle generation algorithm;

[0022] Step 2.3, replace each circular aggregate model in the generation domain with a real aggregate three-dimensional model randomly selected from the aggregate three-dimensional model database until all circular aggregate models in the generation domain are replaced with real aggregate three-dimensional models to generate a real aggregate three-dimensional accumulation model, thereby finally obtaining a real aggregate three-dimensional accumulation model library; wherein each real aggregate three-dimensional model has the same volume as the corresponding circular aggregate model before replacement;

[0023] Step 2.4, convert the obtained real aggregate three-dimensional accumulation model library into a file format compatible with the finite element numerical analysis software to generate a convenient import analysis.

[0024] Further, the step 3 is specifically:

[0025] Step 3.1, according to the design size of the concrete shield segment, generate a three-dimensional model of the concrete shield segment ring in the finite element numerical analysis software, and generate bolt holes and grouting holes through the cutting command in Boolean operation;

[0026] Step 3.2, import the obtained real aggregate three-dimensional accumulation model into the finite element numerical analysis software and cut it to obtain a segment real aggregate three-dimensional accumulation model consistent with the shape of the concrete shield segment model;

[0027] Step 3.3, perform Boolean operation and merge the segment real aggregate three-dimensional accumulation model obtained in step 3.2 with the three-dimensional model of the concrete shield segment ring to generate a corresponding concrete shield segment containing a real aggregate three-dimensional accumulation model;

[0028] Step 3.4, add a steel mesh to the three-dimensional model of the concrete shield segment ring to finally create a concrete shield segment three-dimensional model.

[0029] Further, the step 5 is specifically: simulate the field three-point bending test, apply a vertical concentrated load at the mid-span position of the concrete shield segment three-dimensional model, divide the total load into several loading levels using the static incremental loading method, enable geometric nonlinear analysis to consider the feedback of deformation on structural stiffness, and set the boundary conditions for the concrete shield segment three-dimensional model.

[0030] Further, the step 6 is specifically: meshing for the concrete shield segment three-dimensional model, segment real aggregate three-dimensional accumulation model and steel mesh, adopting mesh strategy adapting to different geometric complexity, wherein quadrilateral or hexahedral element division is preferred in regular structure area to improve calculation efficiency; after meshing, mesh verification is executed in the finite element software to ensure reasonable element shape, no inverted and serious distortion element, providing reliable foundation for subsequent nonlinear analysis and limit state judgment.

[0031] Compared with the prior art, the present application has the following beneficial effects:

[0032] (1) The present application first introduces a heterogeneous aggregate modeling method in the simulation analysis of the shield segment bending resistance test, and constructs a concrete standard block model with microscopic structural characteristics. By using the discrete element technology, multi-graded irregular aggregates are generated, and on this basis, a three-dimensional aggregate-steel composite structure is constructed, which breaks through the limitations of traditional homogeneous material models in expressing the crack initiation and propagation process, and significantly enhances the simulation accuracy and true restoration capability of the model for local crack behavior.

[0033] (2) The present application constructs a bending simulation working condition highly consistent with the field loading condition, sets the two ends of the model as simply supported boundaries, and applies a concentrated load at the midspan position, adopts a hierarchical loading and nonlinear static solution strategy, simulates the whole process response from initial cracking, expansion to final penetration of the crack, and improves the accuracy of crack evolution prediction and the reliability of structure limit state judgment.

[0034] (3) The present application integrates crack response monitoring, damage variable extraction and limit state automatic judgment modules, can extract the crack number, width, damage evolution and stress redistribution data of the key parts of the structure in real time during the simulation process, automatically judges whether the structure reaches the failure state according to the set criteria, establishes a quantitative mapping mechanism between the simulation results and the field measured data, and provides a high-precision, replicable and generalizable technical path for the prefabrication quality evaluation, crack control strategy formulation and structure design parameter optimization of the shield segment.

[0035] In addition to the purposes, features and advantages described above, the present application has other purposes, features and advantages. The present application will be further described in detail below with reference to the accompanying drawings. BRIEF DESCRIPTION OF DRAWINGS

[0036] The accompanying drawings are included to provide a further understanding of the embodiments of the present application, and constitute a part of the specification, and are used together with the following specific embodiments to explain the embodiments of the present application, but do not constitute a limitation on the embodiments of the present application. In the drawings:

[0037] Figure 1is a flowchart of a shield segment non-homogeneous modeling crack and limit simulation method according to an embodiment of the present application;

[0038] Figure 2 is a schematic diagram of a non-homogeneous aggregate accumulation model generated in an embodiment of the present application;

[0039] Figure 3 is a schematic diagram of a concrete shield segment three-dimensional model in an embodiment of the present application;

[0040] Figure 4 is a load-displacement relationship curve graph loaded in an embodiment of the present application;

[0041] Figure 5 is a circumferential crack and inner arc surface crack position diagram of a concrete shield segment in an embodiment of the present application; wherein: (a) is a schematic diagram of a segment A ring surface crack position; (b) is a schematic diagram of a segment B ring surface crack position; (c) is a schematic diagram of a segment inner arc surface crack position. DETAILED DESCRIPTION

[0042] The present application will be described in detail below with reference to the various embodiments shown in the drawings, but it should be noted that these embodiments are not limiting to the present application, and equivalent transformations or substitutions of function, method, or structure made by those of ordinary skill in the art based on these embodiments are within the scope of protection of the present application.

[0043] Please refer to Figure 1 The present embodiment provides a shield segment non-homogeneous modeling crack and limit simulation method, which can reconstruct the internal structure characteristics of concrete at the mesoscale, truly reflect the entire process of crack initiation, expansion, and penetration, and construct the response mapping relationship between simulation and measurement, thereby providing high-precision and high-reliability technical support for shield segment structure design optimization, crack control strategy formulation, and precast quality evaluation. The simulation method specifically includes the following steps:

[0044] Step S1, constructing an aggregate three-dimensional model database: collecting two-dimensional images of multiple aggregate samples, and converting the two-dimensional images of the multiple aggregate samples into aggregate three-dimensional models one by one through a voxelization method, and saving them to the aggregate three-dimensional model database. This step specifically includes:

[0045] Step S1.1, acquiring aggregate two-dimensional cross-sectional images of the typical aggregate samples through multi-view image acquisition and reconstruction technology; and performing image preprocessing operations on the collected multiple aggregate two-dimensional cross-sectional images in sequence, including denoising filtering, gray scale normalization, image binarization, and boundary contour extraction.

[0046] Step S1.2, using interlayer registration and reconstruction algorithm, the two-dimensional image of aggregate is stacked according to the set vertical interlayer spacing, and the corresponding three-dimensional voxel matrix model is generated. In order to improve the accuracy and usability of the model, the initial generated voxel number is interpolated and completed, and the surface smoothing treatment is finally obtained. The three-dimensional model of aggregate with real geometric characteristics is obtained.

[0047] Step S1.3, the generated aggregate three-dimensional model is classified and archived according to the particle size gradation, shape characteristics and volume information, and is uniformly stored in the aggregate three-dimensional model database.

[0048] Step S2, generate a non-homogeneous aggregate accumulation model: based on the plurality of aggregate three-dimensional models generated in step S1, create a real aggregate three-dimensional accumulation model containing multi-gradation and irregular shape aggregate, as shown in Figure 2 The step is specifically:

[0049] Step S2.1, according to the size of the concrete segment in the engineering project design drawing, and determine the structure size of the standard block segment, in the discrete element software PFC, according to the specific size of the concrete segment, set the generation domain of the aggregate; wherein the generation domain of the aggregate is a cuboid region with a length of 4.5m, a width of 1.4m and a height of 1.8m.

[0050] Step S2.2, according to the target porosity and the actual gradation standard of the project, set the radius range of aggregate with different particle size, and use the space distribution method based on density control to construct the initial aggregate distribution field with multi-scale irregular particle size distribution in the standard block model.

[0051] Specifically, according to the field construction experience, the particle size distribution range of aggregate is set to 0.02m~0.15m, and is divided into three different particle size intervals according to the modeling requirements of mesoscopic simulation: small particle size (0.02m~0.04m), medium particle size (0.04m~0.08m) and large particle size (0.08m~0.15m). The overall aggregate volume fraction accounts for about 10% of the total volume of concrete, and the proportion of three types of aggregate particle size gradation is about 26.71%, 36.61% and 36.68% respectively. In order to ensure the rationality of particle size distribution in the model, the particle size in each interval is calculated by interpolation according to the gradation curve, and the particle size data conforming to the statistical characteristics are generated in the form of probability density function. In the process of particle size sampling, the passing rate change law of different intervals must be considered, so that the simulation aggregate gradation is as close as possible to the actual material sieve result.

[0052] Step S2.3, all the circular aggregates in the circular aggregate model are replaced with real aggregate three-dimensional models randomly selected from the aggregate three-dimensional model database of real geometric characteristics by using the equal volume replacement principle to ensure that the volumes of the aggregates before and after replacement are the same; wherein, a random rotation angle and a random translation amount are applied to each real aggregate unit during the generation process, so that the spatial posture and distribution of the aggregate in the generation domain are closer to the random characteristics of the actual mixture.

[0053] Step S2.4, the STL file generated in the discrete element software PFC is converted into an IGES file compatible with the finite element numerical analysis software ABAQUS by using the MATLAB software, so as to be conveniently imported into the finite element numerical analysis software ABAQUS.

[0054] Step S3, establishing a three-dimensional model of a concrete shield segment: according to the design size, a refined model of the concrete shield segment is established, the segment is provided with bolt holes and grouting holes, and the segment includes a steel mesh and real aggregates. This step is specifically:

[0055] Step S3.1, according to the design parameters of the engineering project, the geometric shape and size of the concrete shield segment are determined, and a three-dimensional model of the concrete shield segment ring is created in the finite element numerical analysis software ABAQUS, and then the cutting command in the Boolean operation is used to cut out the bolt holes and grouting holes from the three-dimensional model of the concrete shield segment ring.

[0056] Step S3.2, the real aggregate three-dimensional accumulation model with a cuboid generation domain is cut to obtain a segment real aggregate three-dimensional accumulation model consistent with the shape of the concrete shield segment, and the positions of the grouting holes and bolt holes are cut out.

[0057] Step S3.3, the generated segment real aggregate three-dimensional accumulation model and the three-dimensional model of the concrete shield segment ring are merged by using the Boolean operation to realize the random distribution of the aggregate in the concrete shield segment ring.

[0058] Step S3.4, according to the engineering project design drawing, based on the reinforcement arrangement drawing of the concrete shield segment, as shown in Figure 3 , a steel mesh is designed for the segment, and the steel mesh avoids the bolt holes and grouting holes; specifically, a three-dimensional line body with a radius of 4.1 m is created as the ring-shaped reinforcement, a three-dimensional line body with a length of 1.788 m is created as the transverse reinforcement, and a three-dimensional line body with a length of 3 m is created as the longitudinal reinforcement, and the three types of reinforcement are assembled by using the copy and move commands in the finite element numerical analysis software ABAQUS to form a steel mesh. The steel mesh is built into the segment by using the merge command of the Boolean operation.

[0059] Step S4, define the model material constitutive relation and damage criterion: the concrete adopts a damage plastic constitutive model, and the compression strength, tensile strength, elastic modulus, crack opening strain and damage evolution parameters are defined; the steel bar adopts an ideal elastic-plastic model, and is in force sharing with the concrete through embedded constraint; the large particle size aggregate adopts a linear elastic material model, and participates in the overall stiffness and stress distribution adjustment; meanwhile, key output indicators such as damage variable and equivalent plastic strain are set to monitor the crack initiation, expansion and penetration process. This step is specifically as follows:

[0060] Step S4.1, define the nonlinear constitutive relation of the concrete matrix material. The built-in concrete damage plastic model of the finite element numerical analysis software ABAQUS is used to describe the stress behavior of the concrete material, and the nonlinear response of the segment under tension and compression is simulated. The C50 concrete is used for the segment material, and the mass density, elastic modulus, Poisson's ratio, concrete damage plasticity (including concrete compression damage and concrete tensile damage) of the concrete segment are set.

[0061] Step S4.2, define the steel material constitutive relation: the steel is simulated by an ideal elastic-plastic model, and is in force sharing with the concrete through embedded constraint; the mass density, elastic modulus, Poisson's ratio, plastic parameters (yield stress and plastic strain) of the steel are set.

[0062] Step S4.3, define the material parameters of the non-homogeneous aggregate material: the large particle size aggregate adopts a linear elastic material model, and participates in the overall stiffness and stress distribution adjustment.

[0063] Step S4.4, introduce damage variables (Dt represents tensile damage variable, Dc represents compression damage variable) in the concrete material unit to describe the material stiffness degradation process. When the damage variable tends to 0, it indicates that there is no damage, and when the damage variable tends to 1, it indicates that the material loses strength; in order to accurately reflect the cracking response process of the concrete under bending working condition, a strain-based crack identification mechanism is set: when the principal tensile strain of a certain area exceeds the material ultimate tensile strain, it is considered that micro cracks occur at that position; if multiple crack areas are connected along the midspan, it is considered that the structure has penetrated cracks.

[0064] Step S5, set the equivalent field grading loading working condition and boundary condition. The specific steps are as follows:

[0065] Step S5.1, in order to simulate the actual stress state of the shield tunnel, based on the loading process set in the bending test, the concrete shield segment three-dimensional model is placed in the simply supported working condition for loading, one end of the left and right is set as hinged support, and the other end is set as vertical displacement fixed, horizontal displacement is released, and the vertical displacement and horizontal movement freedom are constrained to simulate the actual boundary conditions when the tunnel is in bending.

[0066] Step S5.2, according to the anti-bending test loading step, a vertical concentrated force is applied to the middle area of the top of the segment, and the loading is divided into seven stages, namely 0 kN, 134.2 kN, 268.4 kN, 402.6 kN, 450 kN, 500 kN, and 550 kN, simulating the whole process from the initial stress to the final failure.

[0067] Step S5.3, in order to realize multi-stage loading control, seven-step loading static general analysis steps are introduced in the finite element numerical analysis software ABAQUS, each loading step is set to a corresponding load amplitude and remains constant, which is convenient for observing the evolution characteristics of cracks at different load stages. As shown in Figure 4 , the displacement data collected in the staged loading process are arranged, and the figure shows the displacement variation law of the B4 standard block center point, load point and horizontal point under the cumulative load. With the gradual increase of external load, the internal cracks of the segment gradually initiate and expand, and finally the segment circumferential crack and inner arc crack position diagram as shown in Figure 5 is obtained; Figure 5 , (a) is the crack position diagram of the segment A ring surface (one end surface of the segment); (b) is the crack position diagram of the segment B ring surface (the other end surface of the segment); (c) is the crack position diagram of the inner arc surface of the segment. According to Figure 5 , the development of cracks at different load stages can be compared, and the evolution law of cracks can also be more intuitively observed.

[0068] Step S6, mesh division and nonlinear static simulation solution. The specific steps are as follows:

[0069] Step S6.1, the heterogeneous concrete shield segment and aggregate adopt C3D10M tetrahedral elements, the grouting layer and the stratum select C3D8R hexahedral elements, and the steel bars select T3D2 truss elements or C3D8R solid elements according to the model type. After generating the mesh, check the aspect ratio and twist degree of the elements, and ensure that the contact surface nodes are aligned.

[0070] Step 6.2, monitor the following indexes during simulation: ① the number and maximum width of the side plate and inner arc surface cracks; ② the number and position change of new cracks; ③ the generation and expansion of transverse through cracks. Combined with the damage criterion, the stress, displacement and damage factor value of the key nodes are extracted in real time to evaluate the stress response and crack expansion trend of the segment at different loading levels.

[0071] Step S6.3, after the last stage of loading is completed, the unloading working condition is applied, the number, width and length of the residual cracks are observed, the actual situation of crack closure or reservation after the segment is unloaded in the field is simulated, and it is used as one of the model verification bases.

[0072] Step S7, set and call the crack response monitoring and output module, and execute the judgment of the limit state of the structure. The specific steps are as follows:

[0073] Step S7.1, set the crack monitoring points and crack path extraction area in the finite element simulation platform, focus on the inner arc middle part, side plate root and upper and lower edge of the standard block tube piece, etc. The monitoring points can be selected as the key element center or node position, and the crack response process tracking is realized by extracting the principal tensile strain, maximum principal stress and damage variable.

[0074] Step S7.2, define the crack initiation and propagation criteria. The crack initiation criterion is that the material damage variable reaches 0.2 to generate the initial crack, and the propagation criterion is based on the continuous degradation of the crack element, the crack region through or the crack width exceeding 0.2mm to judge that the structure enters the limit working state.

[0075] Step S7.3, output the crack cloud picture, observe the crack width distribution and crack evolution history animation, and finally draw the load-crack number curve result graph, which provides the basis for subsequent crack control, structure optimization or failure mechanism research.

[0076] The above only describes the preferred embodiments of the present application and is not used to limit the present application. For those skilled in the art, the present application can have various changes and variations. Any modification, equivalent replacement, improvement, etc. within the spirit and principle of the present application shall be included in the protection scope of the present application.

Claims

1. A method for modeling cracks and limiting simulations in heterogeneous shield tunnel segments, characterized in that, Includes the following steps: Step 1: Construct a 3D aggregate model database: Collect 2D images of multiple aggregate samples, convert the 2D images of multiple aggregate samples into 3D aggregate models one by one using the voxelization method, and save them to the 3D aggregate model database. Step 2: Generate a heterogeneous aggregate packing model: Based on the multiple aggregate 3D models generated in step S1, create a real aggregate 3D packing model containing multi-gradient and irregularly shaped aggregates; Step 3: Use 3D modeling method to establish a detailed model of the concrete shield tunnel segment, construct the segment structure according to the design dimensions and set bolt holes and grouting holes, and embed steel mesh and aggregate distribution in the model; Step 4: Define the nonlinear constitutive relation of the concrete matrix, the elastoplastic constitutive relation of the reinforcing steel, and the parameters of the heterogeneous aggregate material, and set key output indicators for the concrete matrix material. Step 5: Set equivalent on-site graded loading conditions and boundary conditions: Based on the on-site bending test conditions, apply equivalent graded loading to the tunnel segments in the model and set boundary constraints for the model; Step 6: Mesh generation and nonlinear static simulation solution: After the loading and boundary conditions are set, mesh the model, start the nonlinear static analysis module, and apply the preset loads step by step. Step 7: Set up and call the crack response monitoring and output module, and execute the determination of the structural limit state.

2. The simulation method according to claim 1, characterized in that, Step 1 specifically involves: Step S1.1: Acquire images of multiple aggregate samples using multi-view image acquisition and reconstruction technology to obtain multiple two-dimensional cross-sectional images of the aggregates; perform image preprocessing operations on the acquired multiple two-dimensional cross-sectional images of the aggregates in sequence. Step S1.2: Using interlayer registration and reconstruction algorithms, the preprocessed two-dimensional aggregate image is stacked in voxels according to the set vertical interlayer spacing to generate the corresponding three-dimensional voxel matrix model; the initially generated voxels are interpolated and surface smoothed to finally obtain a three-dimensional aggregate model with real geometric features. Step S1.3: Classify and archive the generated aggregate 3D models according to particle size distribution, shape characteristics and volume information, and store them uniformly in the aggregate 3D model database.

3. The simulation method according to claim 1, characterized in that, Step 2 specifically involves: Step 2.1: Based on the design dimensions of the concrete shield tunnel segments, set the aggregate generation domain in the discrete element method software; Step 2.2: Set the porosity and aggregate gradation radius range of the aggregate inside the segment, and generate circular aggregate models with different gradations in the aggregate generation domain using the particle generation algorithm; Step 2.3: Replace each circular aggregate model in the generation domain with a real 3D aggregate model randomly selected from the aggregate 3D model database, until all circular aggregate models in the generation domain have been replaced with real 3D aggregate models to generate real 3D aggregate stacking models, thus finally obtaining a real 3D aggregate stacking model library; wherein, each real 3D aggregate model has the same volume as the corresponding circular aggregate model before replacement. Step 2.4: Convert the obtained real aggregate 3D packing model library into a file format compatible with finite element numerical analysis software to facilitate later import and analysis.

4. The simulation method according to claim 3, characterized in that, Step 3 specifically involves: Step 3.1: Based on the design dimensions of the concrete shield tunnel segments, generate a three-dimensional model of the concrete shield tunnel segment ring in the finite element numerical analysis software, and generate bolt holes and grouting holes through the cutting command in Boolean operations. Step 3.2: Import the obtained real aggregate three-dimensional stacking model into the finite element numerical analysis software and trim it to obtain a real aggregate three-dimensional stacking model of the tunnel segment that is consistent with the shape of the concrete shield tunnel segment model. Step 3.3: Perform Boolean operations to merge the three-dimensional aggregate stacking model of the tunnel segment obtained in Step 3.2 with the three-dimensional model of the concrete shield tunnel segment ring to generate the corresponding concrete shield tunnel segment containing the three-dimensional aggregate stacking model. Step 3.4: Add steel mesh to the 3D model of the concrete shield tunnel segment ring to finally create the 3D model of the concrete shield tunnel segment.

5. The simulation method according to claim 4, characterized in that, Step 5 specifically involves: simulating a three-point bending test on site, applying a vertical concentrated load at the mid-span of the three-dimensional model of the concrete shield tunnel segment, using a static incremental loading method, dividing the total loading force into several loading levels, and using geometric nonlinear analysis to consider the feedback of deformation on structural stiffness, and setting boundary conditions for the three-dimensional model of the concrete shield tunnel segment.

6. The simulation method according to claim 4, characterized in that, Step 6 specifically involves: performing mesh generation on the 3D model of the concrete shield tunnel segment, the 3D model of the actual aggregate stacking of the segment, and the steel mesh, using a meshing strategy adapted to different geometric complexities, wherein the structurally regular regions are divided using quadrilateral or hexahedral elements; after the mesh generation is completed, mesh verification is performed in the finite element software.

Images