Near-field dynamic simulation method and system for yielding support of tunnel

Abstract

The invention relates to the technical field of tunnel engineering, in particular to a near-field dynamics simulation method and system for tunnel yielding support, and the method comprises the steps: dispersing a lining, a steel bar and a high polymer buffer layer model into space material points, distributing different material attributes for different materials, and generating a space coordinate matrix of the material points; a virtual boundary layer serving as a displacement boundary condition applying object is arranged on the outer wall of the lining; determining neighborhoods of the material points, and forming a neighborhood matrix of all the material points; setting a displacement boundary condition according to the large deformation grade; obtaining a compression constitutive model of the high polymer buffer layer, and calculating a micro-elastic modulus; adopting a self-adaptive dynamic relaxation algorithm to construct a near-field kinetic equation to iteratively solve the bond elongation of the material point; and calculating a global damage coefficient according to a comparison result of the key elongation and the critical elongation. According to the invention, crack initiation and development can be simulated on an engineering scale model, and a protection mechanism of an interlayer high polymer buffer layer for large deformation of soft rock is disclosed.

Description

Technical Field

[0001] This invention relates to the field of tunnel engineering technology, and in particular to a near-field dynamic simulation method and system for tunnel pressure relief support. Background Technology

[0002] The "strong support and hard roof" support measures for dealing with large deformation of soft rock have little effect, while the "yielding and resistance coordination" measures (yielding support) are currently the most effective solution.

[0003] Numerical simulation is an important tool for studying large deformation disasters in geotechnical engineering. However, traditional methods such as the finite element method are based on continuum mechanics and are difficult to effectively handle discontinuous phenomena such as material fracture. On the other hand, while discontinuous numerical methods such as the discrete element method are suitable for such problems, they often face challenges of excessive computational cost and insufficient efficiency when simulating actual engineering scales.

[0004] The invention disclosed in CN120120009B, authorized by the Ministry of Science, provides a pressure-relief filling support structure and construction method for soft rock tunnels. The method includes obtaining in-situ stress data, rock mechanics data, and surrounding rock deformation data; when the surrounding rock deformation data exceeds a deformation threshold, locking the deformation area and excavation volume through model simulation; increasing the length of corresponding steps and decreasing the height of corresponding steps according to the excavation volume; installing anchor bolts to seal the surrounding rock surface; laying steel arches; pre-reserving injection holes at the top of the surrounding rock deformation area and injecting filling material to form a pressure-relief filling layer; and spraying concrete again on the surrounding rock contour surface corresponding to each step to form an initial support structure. Although this provides a practical construction method for the support structure, the simulation method has limitations. It cannot intuitively simulate the progressive failure process, is not suitable for large-scale engineering applications, and does not reveal the protective mechanism of the interlayer buffer layer. Summary of the Invention

[0005] The purpose of this invention is to address the shortcomings of existing technologies by providing a near-field dynamic simulation method and system for tunnel pressure relief support. This method simulates crack initiation and development on an engineering-scale model and reveals the protective mechanism of interlayer polymer buffer layers against large deformations in soft rock.

[0006] To achieve the above objectives, the present invention provides a near-field dynamic simulation method for tunnel bearing support, comprising:

[0007] S1: Discretize the lining, steel reinforcement and polymer buffer layer model into a finite number of spatial material points with volume and mass density, assign different material properties to different materials, and generate the spatial coordinate matrix of the material points.

[0008] S2: Set a virtual boundary layer on the outer wall of the lining as the object to which displacement boundary conditions are applied;

[0009] S3: Determine the neighborhood of each material point and form a neighborhood matrix for all material points;

[0010] S4: Set displacement boundary conditions according to the large deformation level;

[0011] S5: Obtain the compression constitutive model of the polymer buffer layer and calculate the microelastic modulus;

[0012] S6: An adaptive dynamic relaxation algorithm is used to construct the near-field dynamic equation and iteratively solve for the bond elongation of material points;

[0013] S7: Calculate the global damage coefficient based on the comparison between the bond elongation and the critical elongation.

[0014] In this invention, the progressive failure process of tunnel lining and composite lining with interlayer polymer buffer layer under large deformation of soft rock is effectively simulated. Crack initiation and development are simulated on an engineering scale model, with high computational efficiency and accuracy.

[0015] Optionally, in S1, a refined model of the circumferential main reinforcement is established for the secondary lining, the bond-slip failure of the concrete-reinforcement interface is modeled, and the critical tensile strength is calculated by the slip value corresponding to the peak stress of the bond-slip curve.

[0016] Optionally, the micromodulus of the bonds at the material points at the interface between the concrete and the reinforcing steel is the average of the micromodulus of the two materials.

[0017] Optionally, in S3, the material points within the neighborhood of the material point can be represented as:

[0018] .

[0019] Where R is the computational domain, δ is the radius, x is a material point, and x' is another material point in the neighborhood.

[0020] In this invention, the material point x exists in a region H with radius δ. x Within the neighborhood, it interacts with other matter points x' within the neighborhood; matter points outside the neighborhood do not interact with each other.

[0021] Optionally, in step S5, a uniaxial compression test is performed on the polymer buffer layer material using a testing machine. The stress-strain relationship is obtained based on the test data fitting or by referencing the classical compression constitutive model of the polymer material. The elastic modulus E of the polymer buffer layer is calculated based on the stress-strain relationship, and further, the micro-elastic modulus c is calculated according to the basic theory of two-dimensional bond-based near-field dynamics. The stress-strain relationship is:

[0022]

[0023] in, , , , , Where ρ is the material density, σ is the stress, and ε is the strain, the expression for the elastic modulus of the polymer buffer layer can be obtained as follows:

[0024]

[0025] Based on the fundamental theory of two-dimensional bond-based near-field dynamics, the expression for the microelastic modulus c can be obtained:

[0026]

[0027] Where η is the relative displacement vector between material points, and ξ is the relative position vector between material points.

[0028] Optionally, in S6, the bond elongation s is calculated using the following formula:

[0029]

[0030]

[0031]

[0032] Where t is time.

[0033] Optionally, in S6, the peri-field dynamic equations are iteratively solved using an adaptive dynamic relaxation algorithm, and the peri-field dynamic equations of the bond bases are established based on Newton's second law:

[0034]

[0035] Where ρ is the point density of the substance. Let x be the acceleration of the substance point x at time t. Let be the volume of the material point x', b(x,t) be the density of the external force acting on the material point, and f be the constitutive force function.

[0036]

[0037]

[0038] Where μ is a scalar function for determining whether a bond breaks, s is the bond elongation rate, and s0 is the critical elongation rate.

[0039] In this invention, when the bond elongation s is greater than the critical elongation s0, the bond is broken.

[0040] Optionally, in S7, the local damage function φ(x,t) is calculated by statistically analyzing the ratio of the number of broken bonds in the neighborhood of a material point to the number of intact bonds:

[0041]

[0042] The local damage function φ takes values ​​in the range [0,1], where 0 represents the intact state and 1 represents the completely damaged state.

[0043] Optionally, in S7, the global damage coefficient ψ is calculated using the following formula:

[0044]

[0045] The global damage coefficient Ψ ranges from [0,1], and φ i Let be the local damage value of the i-th material point, and N be the total number of material points included in the calculation model.

[0046] The present invention also provides a near-field dynamic simulation system for tunnel bearing support, the system comprising:

[0047] The model discretization and attribute assignment module is used to discretize the lining, steel reinforcement and polymer buffer layer models into a finite number of spatial material points with volume and mass density, assign different material properties to different materials, and generate the spatial coordinate matrix of the material points.

[0048] The virtual boundary layer setting module is used to set a virtual boundary layer of a certain thickness on the outer wall of the lining as the object to which displacement boundary conditions are applied, so as to weaken the impact of boundary effects on the core calculation region.

[0049] The neighborhood matrix construction module is used to determine the neighborhood range of each material point and form a neighborhood matrix for all material points.

[0050] The displacement boundary condition setting module is used to set the displacement magnitude based on the actual monitored surrounding rock deformation or the large deformation classification table in the specification document.

[0051] The constitutive model acquisition module is used to acquire the compressive constitutive model of the polymer buffer layer and calculate the micro-elastic modulus. This module is configured to calculate the elastic modulus based on the stress-strain relationship of the polymer material obtained through uniaxial compression tests, and further calculate the micro-elastic modulus according to the two-dimensional bond-based near-field dynamics theory.

[0052] The dynamics solution module is configured to use an adaptive dynamic relaxation algorithm, set a virtual diagonal density matrix and a virtual damping coefficient, and calculate the bond elongation of material points by iteratively solving the near-field dynamic equations;

[0053] The damage calculation module is used to determine bond damage based on the comparison between bond elongation rate and critical elongation rate, and to calculate the local damage function and global damage coefficient.

[0054] Beneficial effects:

[0055] This invention achieves effective simulation of the progressive failure process of tunnel lining and composite lining with interlayer polymer buffer layer under large deformation of soft rock. It simulates crack initiation and development on an engineering scale model, with high computational efficiency and accuracy. Attached Figure Description

[0056] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on the structures shown in these drawings without creative effort.

[0057] Figure 1 A flowchart illustrating a near-field dynamic simulation method for tunnel pressure relief support;

[0058] Figure 2 A schematic diagram of a composite lining for a tunnel;

[0059] Figure 3 A schematic diagram of a pressure-relief lining for tunnels;

[0060] Figure 4 A schematic diagram of the structure of the tunnel composite lining analysis model;

[0061] Figure 5 A schematic diagram of the structural analysis model for tunnel pressure-bearing lining;

[0062] Figure 6 A schematic diagram illustrating a simulation method for the interaction between concrete and reinforcing steel.

[0063] Figure 7 This is a schematic diagram of a typical stress-strain curve for a polymer buffer layer.

[0064] Figure 8 A schematic diagram of an analysis model provided for a specific embodiment;

[0065] Figure 9 A graph showing the variation of the global tunnel damage coefficient with tunnel convergence, provided for a specific embodiment;

[0066] Figure 10 A first deformation damage cloud map of a relief support provided for a specific embodiment;

[0067] Figure 11 A second deformation damage cloud map of a relief support provided for a specific embodiment;

[0068] Figure 12 The third deformation damage cloud map of the pressure relief support is provided for a specific embodiment.

[0069] Figure label:

[0070] 1. Initial support; 2. Secondary lining; 3. Invert arch; 4. Polymer buffer layer; 5. Displacement boundary conditions; 6. Virtual boundary layer.

[0071] The realization of the objective, functional characteristics and advantages of the present invention will be further explained in conjunction with the embodiments and with reference to the accompanying drawings. Detailed Implementation

[0072] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of the present invention, and not all of them. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0073] In the description of this invention, unless otherwise explicitly defined, terms such as "set up," "install," and "connect" should be interpreted broadly, and those skilled in the art can reasonably determine the specific meaning of the above terms in this invention in conjunction with the specific content of the technical solution.

[0074] In the description of this invention, the terms "one embodiment," "some embodiments," "illustrative embodiment," "example," "specific example," or "some examples," etc., refer to specific features, structures, materials, or characteristics described in connection with that embodiment or example, which are included in at least one embodiment or example of the invention. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples.

[0075] See Figure 1 According to an embodiment of the present invention, a near-field dynamic simulation method for tunnel pressure relief support includes: S1: discretizing the lining, steel reinforcement and polymer buffer layer model into a finite number of spatial material points with volume and mass density, assigning different material properties to different materials, and generating a spatial coordinate matrix of the material points;

[0076] S2: Set a virtual boundary layer on the outer wall of the lining as the object to which displacement boundary conditions are applied;

[0077] S3: Determine the neighborhood of each material point and form a neighborhood matrix for all material points;

[0078] S4: Set displacement boundary conditions according to the large deformation level;

[0079] S5: Obtain the compression constitutive model of the polymer buffer layer and calculate the microelastic modulus;

[0080] S6: An adaptive dynamic relaxation algorithm is used to construct the near-field dynamic equation and iteratively solve for the bond elongation of material points;

[0081] S7: Calculate the global damage coefficient based on the comparison between the bond elongation and the critical elongation.

[0082] In this invention, the progressive failure process of tunnel lining and composite lining with interlayer polymer buffer layer under large deformation of soft rock is effectively simulated. Crack initiation and development are simulated on an engineering scale model, with high computational efficiency and accuracy.

[0083] See Figures 2-5 ,in Figure 2 A schematic diagram of the composite lining structure of the tunnel is shown. Figure 3 A schematic diagram of a pressure-relief lining for tunnels is shown. Figure 4 A schematic diagram of the analytical model for a tunnel composite lining is shown. Figure 5 A schematic diagram of the analytical model for a pressure-yielding lining in a tunnel is shown. The composite lining consists of an initial support 1 and a secondary lining 2, without a polymer buffer layer 4 between them. In contrast, the pressure-yielding lining incorporates a polymer buffer layer 4 between the initial support 1 and the secondary lining 2, forming a pressure-yielding support structure. The invert arch 3 is a reverse arch structure located at the bottom of the tunnel. By forming an integral part with the secondary lining 2, it can transfer the pressure from the upper strata to the underground and resist the reaction force from the lower strata, improving the stress conditions of the upper support structure. By setting a virtual boundary layer 6 on the outer wall of the lining, the boundary effect is weakened, improving the simulation accuracy.

[0084] In some embodiments of the present invention, in S1, a refined model of the circumferential main reinforcement is established for the secondary lining, the bond-slip failure of the concrete-reinforcement interface is modeled, and the critical tensile strength is calculated by the slip value corresponding to the peak stress of the bond-slip curve.

[0085] See Figure 6 In some embodiments of the present invention, the micromodulus of the bonds at the material points at the interface between the concrete and the reinforcing steel is the average of the micromodulus of the two.

[0086] In some embodiments of the present invention, in step S3, the material points within the neighborhood of the material point can be represented as:

[0087] .

[0088] Where R is the computational domain, δ is the radius, x is a material point, and x' is another material point in the neighborhood.

[0089] In this invention, the material point x exists in a region H with radius δ. x Within the neighborhood, it interacts with other matter points x' within the neighborhood; matter points outside the neighborhood do not interact with each other.

[0090] See Figure 7 In some embodiments of the present invention, in step S5, a testing machine is used to perform a uniaxial compression test on the polymer buffer layer material. The stress-strain relationship is obtained based on the test data fitting or by referencing the classical compression constitutive model of the polymer material. The elastic modulus E of the polymer buffer layer is calculated based on the stress-strain relationship, and further, the micro-elastic modulus c is calculated according to the basic theory of two-dimensional bond-based near-field dynamics. The stress-strain relationship is as follows:

[0091]

[0092] in, , , , , Where ρ is the material density, σ is the stress, and ε is the strain, the expression for the elastic modulus of the polymer buffer layer can be obtained as follows:

[0093]

[0094] Based on the fundamental theory of two-dimensional bond-based near-field dynamics, the expression for the microelastic modulus c can be obtained:

[0095]

[0096] Where η is the relative displacement vector between material points, and ξ is the relative position vector between material points.

[0097] Specifically, the testing machine is an MTS rock hydraulic universal testing machine, which is capable of performing the uniaxial compression test of this invention.

[0098] In some embodiments of the present invention, in step S6, the bond elongation s is calculated using the following formula:

[0099]

[0100]

[0101]

[0102] Where t is time.

[0103] In some embodiments of the present invention, in step S6, the near-field dynamic equations are iteratively solved using an adaptive dynamic relaxation algorithm, and the near-field dynamic equations of the bond bases are established according to Newton's second law:

[0104]

[0105] Where ρ is the point density of the substance. Let x be the acceleration of the substance point x at time t. Let be the volume of the material point x', b(x,t) be the density of the external force acting on the material point, and f be the constitutive force function.

[0106]

[0107]

[0108] Where μ is a scalar function for determining whether a bond breaks, s is the bond elongation rate, and s0 is the critical elongation rate.

[0109] In this invention, when the bond elongation s is greater than the critical elongation s0, the bond is broken.

[0110] In some embodiments of the present invention, in S7, the local damage function φ(x,t) is calculated by statistically analyzing the ratio of the number of broken bonds in the neighborhood of a material point to the number of intact bonds:

[0111]

[0112] The local damage function φ takes values ​​in the range [0,1], where 0 represents the intact state and 1 represents the completely damaged state.

[0113] In some embodiments of the present invention, in step S7, the global damage coefficient ψ is calculated using the following formula:

[0114]

[0115] The global damage coefficient Ψ ranges from [0,1], and φ i Let be the local damage value of the i-th material point, and N be the total number of material points included in the calculation model.

[0116] Specifically, by introducing the local damage function φ and the global damage coefficient Ψ, the degree of structural damage can be quantitatively described.

[0117] According to an embodiment of the present invention, a near-field dynamic simulation system for tunnel bearing support is provided, the system comprising:

[0118] The model discretization and attribute assignment module is used to discretize the lining, steel reinforcement and polymer buffer layer models into a finite number of spatial material points with volume and mass density, assign different material properties to different materials, and generate the spatial coordinate matrix of the material points.

[0119] The virtual boundary layer setting module is used to set a virtual boundary layer of a certain thickness on the outer wall of the lining as the object to which displacement boundary conditions are applied, so as to weaken the impact of boundary effects on the core calculation region.

[0120] The neighborhood matrix construction module is used to determine the neighborhood range of each material point and form a neighborhood matrix for all material points.

[0121] The displacement boundary condition setting module is used to set the displacement magnitude based on the actual monitored surrounding rock deformation or the large deformation classification table in the specification document.

[0122] The constitutive model acquisition module is used to acquire the compressive constitutive model of the polymer buffer layer and calculate the micro-elastic modulus. This module is configured to calculate the elastic modulus based on the stress-strain relationship of the polymer material obtained through uniaxial compression tests, and further calculate the micro-elastic modulus according to the two-dimensional bond-based near-field dynamics theory.

[0123] The dynamics solution module is configured to use an adaptive dynamic relaxation algorithm, set a virtual diagonal density matrix and a virtual damping coefficient, and calculate the bond elongation of material points by iteratively solving the near-field dynamic equations;

[0124] The damage calculation module is used to determine bond damage based on the comparison between bond elongation rate and critical elongation rate, and to calculate the local damage function and global damage coefficient.

[0125] In one specific embodiment of the present invention, see [link to relevant documentation]. Figure 8 Taking a full-face hard rock tunnel boring machine as an example, the inner diameter is 3.95m, the secondary lining thickness is 30cm, and the initial support thickness is 20cm. The secondary lining uses C35 concrete with a Young's modulus of 32.5GPa, while the initial support uses C25 concrete with a Young's modulus of 25.7GPa. The elastic modulus of the reinforcing steel is 200GPa. The polymer buffer layer density is 50 / 100 / 150 kg / m³, the material point spacing is 0.05m, the virtual boundary layer consists of 3 material points, the near-field range is 3.15 times the point spacing, and the time step Δt = 2 × 10⁻⁶. -6According to the classification of large deformation in the "Railway Tunnel Design Code (TB 10003-2016)," displacement magnitudes are set, with deformation levels I and II selected, corresponding to relative deformations of 3%, 5%, and 8%. The calculated boundary displacement values ​​are 0.1335m, 0.2225m, and 0.356m, respectively. The calculation conditions are combinations of three boundary displacement conditions and four polymer buffer layer thicknesses for each polymer buffer layer density. The calculations yield the following results: Figure 9 The curve showing the global tunnel damage coefficient changing with tunnel convergence is shown; and as shown... Figures 10-12 The diagram shown is a contour map of deformation and damage in the pressure-bearing support.

[0126] in, Figure 9 The study shows the variation of the structural damage index with tunnel convergence under moderate to large deformation. Taking a polymer buffer layer with a density of 100 kg / m³ as an example, the damage index increases nonlinearly with convergence deformation, and the tunnel damage evolution process can be divided into a damage initiation stage, a rapid damage development stage, and a slow damage development stage. It can be seen that the presence of the buffer layer significantly reduces the process of lining failure.

[0127] in, Figures 10-12 The damage profile of the pressure-supported structure is shown. For conventional composite linings (with a 0 cm thick polymer buffer layer), damage to the support mainly occurs on the inner side of the secondary lining. This is because the secondary lining has higher stiffness and therefore bears most of the load generated by tunnel convergence, making it more susceptible to failure. It can also be seen that even with slight large deformations (relative deformation of 3%), structural damage to the secondary lining still occurs, indicating that conventional composite linings are insufficient to prevent large deformations. By applying a polymer buffer layer, the damage distribution of the secondary lining is significantly reduced compared to conventional composite linings, while the initial support often fails. Similarly, the density of the polymer (ranging from 50-100 kg / m³) has no significant effect on the damage characteristics of the lining. For slight large deformations, a 40 cm thick polymer buffer layer is sufficient to prevent failure of the secondary lining, while localized damage is observed in secondary linings with a 25 cm thick polymer buffer layer due to yield deformation. For severe and extremely severe large deformations, only polymer buffer layers thicker than 40 cm can prevent failure of the secondary lining. Therefore, using a polymer buffer layer can effectively reduce the overall damage index of the lining.

[0128] The above are merely preferred embodiments of the present invention and do not limit the patent scope of the present invention. Any equivalent structural transformations made using the contents of the present invention specification and drawings under the inventive concept of the present invention, or direct / indirect applications in other related technical fields, are included within the patent protection scope of the present invention.

Claims

1. A method for near-field dynamics simulation of tunnel yielding support, characterized in that, The method comprises: S1: discretize the lining, steel bar and polymer buffer layer model into a finite number of spatial particles with volume and mass density, assign different material properties to different materials, and generate a spatial coordinate matrix of the particles; S2: set a virtual boundary layer on the outer wall of the lining as an object for applying displacement boundary conditions; S3: determine the neighborhood of the particles to form a neighborhood matrix of all particles; S4: set the displacement boundary conditions according to the large deformation level; S5: obtain the compression constitutive model of the polymer buffer layer, and calculate the micro-elastic modulus; S6: use the adaptive dynamic relaxation algorithm to construct the near-field dynamics equation to iteratively solve the bond elongation of the particles; S7: calculate the global damage coefficient according to the comparison result of the bond elongation and the critical elongation.

2. The near-field dynamics simulation method of a tunnel yielding support according to claim 1, characterized in that, In S1, a fine model of the circumferential main reinforcement is established for the secondary lining, the bond-slip failure at the interface between the concrete and the steel bar is modeled, and the critical tension is calculated by the slip value corresponding to the peak stress of the bond-slip curve.

3. The method of claim 2, wherein, The micro modulus of the bond of the particles at the interface between the concrete and the steel bar is the average of the micro modulus of the two.

4. The method of claim 1, wherein, In S3, the particles in the neighborhood of the particles can be expressed as: ； Wherein, R is the calculation area, δ is the radius, x is the particle, and x' is the other particles in the neighborhood.

5. The method of claim 4, wherein, In S5, a testing machine is used to perform uniaxial compression test on the polymer buffer layer material, a stress-strain relationship is obtained based on test data fitting or by referring to a classic compression constitutive model of the polymer material, the elastic modulus E of the polymer buffer layer is calculated based on the stress-strain relationship, and further according to the basic theory of two-dimensional bond-based near-field dynamics, the micro-elastic modulus c is calculated, wherein the stress-strain relationship is: ； wherein, , , , , , p is the density of the material, s is the stress, and e is the strain, from which the expression for the elastic modulus of the polymer cushion layer is obtained: ； According to the basic theory of two-dimensional bond-based near-field dynamics, the expression of the micro-elastic modulus c can be obtained: ； Wherein, η is the relative displacement vector between the particles, and ξ is the relative position vector between the particles.

6. The method of near-field dynamics simulation of a tunnel yielding support according to claim 5, characterized in that, In S6, the bond elongation s is calculated by the following formula: ； ； ； Wherein, t is the time.

7. The method of near-field dynamics simulation of a tunnel yielding support according to claim 6, characterized in that, In S6, the near-field dynamics equation iteratively solved by the adaptive dynamic relaxation algorithm is used to establish the bond-based near-field dynamics motion equation according to Newton's second law: ； where p is the density of the material point, is the acceleration of the material point x at time t, is the volume of the material point x', b(x, t) is the external force density on the material point, and f is the constitutive force function, ； ； Wherein, μ is a scalar function for judging whether the bond is broken or not, s is the bond elongation, and s0 is the critical elongation.

8. The method of near-field dynamics simulation of a tunnel yielding support according to claim 7, characterized in that, In S7, the local damage function φ(x, t) is calculated by counting the ratio of the number of broken bonds to the number of intact bonds in the neighborhood of the particles: ； Wherein, the value range of the local damage function φ is [0, 1], 0 represents the intact state, and 1 represents the completely damaged state.

9. The method of claim 8, wherein, In S7, the global damage coefficient ψ is calculated by the following formula: ； where the global damage coefficient Ψ is in the interval [0, 1], φ i is the local damage value of the ith material point, and N is the total number of material points included in the computational model.

10. A near-field dynamics simulation system for tunnel yielding support, characterized in that, The system comprises: A model discretization and attribute allocation module for discretizing the lining, steel bar and polymer buffer layer model into a finite number of spatial particles with volume and mass density, assigning different material properties to different materials, and generating a spatial coordinate matrix of the particles; A virtual boundary layer setting module for setting a virtual boundary layer with a certain thickness on the outer wall of the lining as an object for applying displacement boundary conditions to weaken the influence of boundary effect on the core calculation area; A neighborhood matrix construction module is configured to determine the neighborhood range of each material point and form a neighborhood matrix of all material points; A displacement boundary condition setting module is configured to set the displacement size according to the actually monitored deformation of the surrounding rock or the large deformation grading table in the specification file; The constitutive model acquisition module is configured to acquire the compression constitutive model of the high polymer buffer layer and calculate the micro-elastic modulus. The module is configured to calculate the elastic modulus based on the stress-strain relationship of the high polymer material obtained through the uniaxial compression test, and further calculate the micro-elastic modulus according to the two-dimensional bond-based near-field dynamics theory; The dynamic solving module is configured to set a virtual diagonal density matrix and a virtual damping coefficient by using an adaptive dynamic relaxation algorithm, and calculate the bond elongation of the material point by iteratively solving the near-field dynamics equation; The damage calculation module is configured to judge the damage of the bond according to the comparison result of the bond elongation and the critical elongation, and calculate the local damage function and the global damage coefficient.

Images