Tunnel rock anchor bearing arch numerical calculation method considering mechanical parameter change of surrounding rock

Abstract

The invention relates to the technical field of civil engineering, and particularly discloses a tunnel rock anchor bearing arch numerical calculation method considering mechanical parameter changes of surrounding rock, which comprises the following steps: establishing a tunnel rock anchor bearing arch numerical calculation model to carry out numerical calculation in the ith step; traversing all units in the model; extracting a corresponding stress component and a centroid coordinate of each unit and then calculating a radial stress of each unit; calculating a mechanical parameter update value of each unit; judging whether each unit participates in numerical calculation of the ith step or not; if so, endowing the unit with updated mechanical parameters, otherwise, keeping the mechanical parameters unchanged; judging whether the i-step numerical calculation of the numerical model is converged or not; if convergence occurs, the calculation process is ended, and otherwise, numerical calculation of the (i + 1) th step is carried out. According to the method, in the numerical calculation process of the tunnel rock anchor bearing arch, the change of surrounding rock mechanical parameters along with the change of surrounding rock stress is considered, reference is provided for the design of tunnel engineering supported by anchor rods, and the method has good engineering value.

Description

Technical Field

[0001] The invention relates to the technical field of civil engineering, and in particular to a numerical calculation method for a tunnel rock anchor bearing arch taking into account changes in surrounding rock mechanical parameters. Background Art

[0002] The mechanical parameters of the surrounding rock are not the same under different confining pressure conditions. Its elastic modulus, Poisson's ratio, cohesion and friction angle will change with the change of radial stress on the surrounding rock. After the tunnel is excavated, the surrounding rock stress will be redistributed, resulting in different radial stresses of the surrounding rock at different radial depths. Therefore, as the tunnel excavation proceeds, the mechanical parameters of the surrounding rock are constantly changing, rather than being a fixed value. In addition, if anchor rods are applied to the surrounding rock after the tunnel is excavated, the mechanical parameters of the surrounding rock will change further under the action of anchor rod prestress. Therefore, when carrying out the numerical analysis of the tunnel rock anchor bearing arch, the changes in mechanical parameters with the changes in radial stress and anchor rod parameters should be considered in the model. At present, domestic and foreign scholars' research on the numerical calculation of tunnel rock anchor spray bearing arches sets the mechanical parameters of the surrounding rock to constant values ​​from the beginning to the end of the calculation, which does not conform to engineering practice. Therefore, it is of great significance to construct a numerical calculation method for the tunnel rock anchor bearing arch that considers the changes in the surrounding rock mechanical parameters, so that the changes in the surrounding rock mechanical parameters with the surrounding rock stress can be considered in the numerical calculation process of the tunnel rock anchor bearing arch, which is more in line with the actual engineering practice. Summary of the invention

[0003] In order to solve the problems existing in the prior art, the present invention provides a numerical calculation method for tunnel rock anchor bearing arch taking into account the changes in the mechanical parameters of the surrounding rock, so that in the numerical calculation process of the tunnel rock anchor bearing arch, the changes in the mechanical parameters of the surrounding rock as the surrounding rock stress changes can be considered, which is more in line with the actual engineering practice, provides a reference for the design of tunnel engineering using anchor support, and solves the problems mentioned in the above background technology.

[0004] To achieve the above object, the present invention provides the following technical solution: a numerical calculation method for tunnel rock anchor bearing arch considering the change of surrounding rock mechanical parameters, comprising the following steps:

[0005] S1. Establish a numerical calculation model for the tunnel rock anchor bearing arch;

[0006] S2, carry out the i-th step numerical calculation according to the established tunnel rock anchor bearing arch numerical model;

[0007] S3, traverse all the units in the numerical model of the tunnel rock anchor bearing arch;

[0008] S4, extracting the corresponding stress components and centroid coordinates of each unit;

[0009] S5. Calculate the radial stress of each unit according to the extracted stress components and centroid coordinates of each unit;

[0010] S6. Calculate the updated value of the mechanical parameters of each unit according to the calculated radial stress of each unit and the anchor rod parameters of the tunnel rock anchor bearing arch;

[0011] S7, determining whether each unit participates in the numerical calculation of the i-th step;

[0012] S8. If the unit participates in the numerical calculation of step i, the updated mechanical parameters of the unit are assigned, otherwise the mechanical parameters of the unit remain unchanged;

[0013] S9, judging whether the numerical calculation of the numerical model step i has converged;

[0014] S10. If the numerical calculation of the numerical model in step i converges, the calculation process is terminated; otherwise, the numerical calculation of step i+1 is carried out.

[0015] Preferably, the step S1 specifically includes:

[0016] S11, establishing a corresponding geometric model according to the size of the tunnel rock anchor bearing arch numerical model, and dividing the grid according to the geometric model;

[0017] S12. Assign initial computational mechanics parameters to the model based on geological survey data and specifications;

[0018] S13. Assign boundary conditions to the numerical model of the tunnel rock anchor bearing arch and start calculation.

[0019] Preferably, the step S2 specifically includes:

[0020] S21, carry out the first step of numerical calculation based on the established tunnel rock anchor bearing arch numerical model;

[0021] S22, performing the second step of numerical calculation based on the numerical calculation result of the first step;

[0022] S23. Carry out the i-th step numerical calculation based on the result of the i-1-th step numerical calculation until the model calculation converges.

[0023] Preferably, the step S3 specifically includes:

[0024] S31, traversing all units of the tunnel rock anchor bearing arch value based on programming;

[0025] S32. Filter out the solid units whose constitutive model is the surrounding rock among all the units.

[0026] Preferably, the step S4 specifically includes:

[0027] S41, according to all the surrounding rock entity units traversed in step S3, extract the stress components of each unit, including stress in the xx direction, stress in the yy direction, stress in the zz direction, stress in the xy direction, stress in the xz direction and stress in the yz direction;

[0028] S42. According to all the surrounding rock entity units traversed in step S3, extract the id and centroid coordinates of each unit, wherein the centroid coordinates include x, y and z.

[0029] Preferably, the step S5 specifically includes:

[0030] S51: Calculate the polar coordinate angle of each unit according to the centroid coordinates of each unit extracted in step S4:

[0031] θ=F1(x,y,z) (1)

[0032] Where: F1(x) is the polar coordinate angle calculation function of the unit; x is the x coordinate value of the unit; y is the y coordinate value of the unit; z is the z coordinate value of the unit; θ is the polar coordinate angle of the unit, (rad);

[0033] S52: Calculate the radial stress of each unit according to the stress component and polar coordinate angle of each unit extracted in step S4:

[0034] σ r =F2(σ xx ,σ yy ,σ zz ,τ xy ,τ xz ,τ yz ,θ) (2)

[0035] Where: F2(x) is the radial stress calculation function of the unit; σ r is the radial stress of the unit, (Pa); σ xx is the stress of the unit along the xx direction, (Pa); σ yy is the stress of the unit along the yy direction, (Pa); σ zz is the stress of the unit along the zz direction, (Pa); τ xy is the stress of the unit along the xy direction, (Pa); τ xz is the stress of the unit along the xz direction, (Pa); τ yz is the stress of the unit along the yz direction, (Pa).

[0036] Preferably, the step S6 specifically includes:

[0037] S61, calculating the updated value of the elastic modulus of each unit according to the radial stress of each unit calculated in step S5 and the anchor rod parameters of the tunnel rock anchor bearing arch:

[0038] E update =G1(σ r ,F b ) (3)

[0039] Where: G1(x) is the calculation function of the elastic modulus and radial stress of the unit and the anchor parameters; E update Update the elastic modulus corresponding to the unit, (Pa); F b is the anchor prestress value of the tunnel rock anchor bearing arch;

[0040] S62, calculating the updated value of the Poisson's ratio of each unit according to the radial stress of each unit calculated in step S5 and the anchor rod parameters of the tunnel rock anchor bearing arch:

[0041] v update =G2(σ r ,F b ) (4)

[0042] Where: G2(x) is the calculation function of the unit's Poisson's ratio, radial stress and anchor parameters; v update Update the Poisson's ratio corresponding to the unit;

[0043] S63, calculating the updated value of the cohesion of each unit according to the radial stress of each unit calculated in step S5 and the anchor parameters of the tunnel rock anchor bearing arch:

[0044] c update =G3(σ r ,F b ) (5)

[0045] Where: G3(x) is the calculation function of the unit cohesion and radial stress as well as anchor parameters; c update Update the value of cohesion corresponding to the unit, (Pa);

[0046] S64, calculating the updated value of the friction angle of each unit according to the radial stress of each unit calculated in step S5 and the anchor rod parameters of the tunnel rock anchor bearing arch:

[0047]

[0048] Where: G4(x) is the calculation function of the friction angle and radial stress of the unit and the anchor parameters; Update the friction angle corresponding to the element, (°).

[0049] Preferably, the step S7 specifically includes:

[0050] Determine whether each unit participates in the numerical calculation of the i-th step. In FLAC 3D software, if the constitutive model of a unit is a null model, the unit does not participate in the numerical calculation of the i-th step, otherwise it participates; in ABAQUS software, if the status of a unit in the i-th step is set to "kill", the unit does not participate in the numerical calculation of the i-th step, otherwise it participates.

[0051] Preferably, the step S8 specifically includes:

[0052] S81. According to the identification results of all units in step S7, if the unit participates in the numerical calculation of step i, the updated mechanical parameters of the unit are assigned:

[0053] E i =E update (7)

[0054] v i =v update (8)

[0055] c i =c update (9)

[0056]

[0057] Where: E i is the elastic modulus value corresponding to the unit in the numerical calculation of the i-th step, (Pa); v i is the Poisson's ratio corresponding to the unit in the numerical calculation of step i; c i is the cohesion value corresponding to the unit in the numerical calculation of the i-th step, (Pa); is the friction angle value corresponding to the unit in the numerical calculation of step i, (°);

[0058] S82. According to the identification results of all units in step S7, if the unit does not participate in the numerical calculation of step i, the mechanical parameters of the unit do not change:

[0059] E i =E i-1 (11)

[0060] v i =v i-1 (12)

[0061] c i =c i-1 (13)

[0062]

[0063] Where: E i-1 is the elastic modulus value corresponding to the unit in the numerical calculation of step i-1, (Pa); v i-1is the Poisson's ratio corresponding to the unit in the numerical calculation of step i-1; c i-1 is the cohesion value corresponding to the unit in the numerical calculation of step i-1, (Pa); It is the friction angle value corresponding to the unit in the numerical calculation of the i-1th step, (°).

[0064] Preferably, the step S9 specifically includes:

[0065] Whether the numerical calculation of the numerical model in the i-th step converges. In FLAC 3D software, if the unbalanced force ratio of the model in the i-th step numerical calculation is less than 1e-5, the model calculation converges, otherwise it does not converge; in ABAQUS software, if the model calculation time of the i-th step numerical calculation reaches the set model calculation time, the model calculation converges, otherwise it does not converge.

[0066] The beneficial effects of the present invention are as follows: based on the calculation process of numerical calculation and the changing rules of surrounding rock mechanical parameters with surrounding rock stress and anchor parameters, the present invention establishes a numerical calculation method for tunnel rock anchor bearing arch that takes into account the changes in surrounding rock mechanical parameters. The calculation process of the obtained method is clear and rigorous, the calculation formula is simple and easy to understand, the calculation process is simple and efficient, and the calculation results are accurate and highly reliable. Ordinary designers can simply, quickly and accurately reproduce the research ideas and processes by using a numerical calculation method for tunnel rock anchor bearing arch that takes into account the changes in surrounding rock mechanical parameters obtained by the present invention, so that in the numerical analysis of tunnel rock anchor bearing arch, the changes in surrounding rock mechanical parameters with surrounding rock stress are considered, which is more in line with engineering practice, provides a reference for the design of tunnel engineering using anchor support, and has good engineering value. BRIEF DESCRIPTION OF THE DRAWINGS

[0067] Figure 1 The figure is a schematic flow chart of the steps of a method for numerically calculating a tunnel rock anchor bearing arch taking into account changes in the mechanical parameters of the surrounding rock in an embodiment of the present invention. DETAILED DESCRIPTION

[0068] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0069] See also Figure 1 , the present invention provides a technical solution: a numerical calculation method for the bearing arch of tunnel rock anchor considering the change of surrounding rock mechanical parameters, such as Figure 1 As shown, the following steps are included:

[0070] Step 1: Establish a numerical calculation model of the tunnel rock anchor bearing arch.

[0071] The specific steps include:

[0072] 1) Establish a corresponding geometric model according to the size of the tunnel rock anchor bearing arch numerical model, and divide the grid according to the geometric model;

[0073] 2) Assign initial computational mechanics parameters to the model based on geological survey data and specifications;

[0074] 3) Assign boundary conditions to the numerical model of the tunnel rock anchor bearing arch and start calculation.

[0075] Step 2: Carry out the i-th step numerical calculation based on the established tunnel rock anchor bearing arch numerical model.

[0076] The specific steps include:

[0077] 1) Carry out the first step of numerical calculation based on the established numerical model of tunnel rock anchor bearing arch;

[0078] 2) Carry out the second step numerical calculation based on the numerical calculation results of the first step;

[0079] 3) Carry out the numerical calculation of step i based on the numerical calculation results of step i-1 until the model calculation converges.

[0080] Step 3: Traverse all the units in the numerical model of the tunnel rock anchor bearing arch.

[0081] The specific steps include:

[0082] 1) Traverse all the units in the tunnel rock anchor bearing arch numerical value based on programming;

[0083] 2) Filter out the solid units whose constitutive model is the surrounding rock among all the units.

[0084] Step 4: Extract the corresponding stress components and centroid coordinates of each unit.

[0085] The specific steps include:

[0086] 1) According to all the surrounding rock entity units traversed in step 3, the stress components of each unit are extracted, including stress in the xx direction, stress in the yy direction, stress in the zz direction, stress in the xy direction, stress in the xz direction, and stress in the yz direction;

[0087] 2) According to all the surrounding rock entity units traversed in step 3, extract the ID and centroid coordinates of each unit, where the centroid coordinates include x, y and z.

[0088] Step 5: Calculate the radial stress of each unit based on the extracted stress components and centroid coordinates of each unit.

[0089] The specific steps include:

[0090] 1) Calculate the polar coordinate angle of each unit according to the centroid coordinates of each unit extracted in step 4:

[0091]

[0092] Where: x is the x-coordinate value of the unit; z is the z-coordinate value of the unit; θ is the polar coordinate angle of the unit, (rad);

[0093] 2) Calculate the radial stress of each unit based on the stress components and polar coordinate angles of each unit extracted in step 4:

[0094] σ r =σ xx cos 2 θ+σ zz sin 2 θ+2τ xz sinθcosθ (16)

[0095] Where: r is the radial stress of the unit, (Pa); σ xx is the stress of the unit along the xx direction, (Pa); σ zz is the stress of the unit along the zz direction, (Pa); τ xz is the stress of the unit along the xz direction, (Pa).

[0096] Step 6: Calculate the updated value of the mechanical parameters of each unit based on the calculated radial stress of each unit and the anchor parameters of the tunnel rock anchor bearing arch.

[0097] The specific steps include:

[0098] 1) Calculate the updated value of the elastic modulus of each unit based on the radial stress of each unit calculated in step 5 and the anchor parameters of the tunnel rock anchor bearing arch:

[0099]

[0100] Where: E update Update the elastic modulus corresponding to the unit, (Pa); F b A is the anchor prestress value of the tunnel rock anchor bearing arch; E and B E The undetermined coefficients for the fitting curve can be obtained by fitting the indoor triaxial test results.

[0101] 2) Calculate the updated Poisson's ratio of each unit based on the radial stress of each unit calculated in step 5 and the anchor parameters of the tunnel rock anchor bearing arch:

[0102] vupdate =v (18)

[0103] Where: v update is the updated value of Poisson’s ratio corresponding to the unit; v is the original Poisson’s ratio of the surrounding rock.

[0104] 3) Calculate the updated cohesion value of each unit based on the radial stress of each unit calculated in step 5 and the anchor parameters of the tunnel rock anchor bearing arch:

[0105]

[0106] Where: c update is the updated value of cohesion corresponding to the unit, (Pa); A c and B c The undetermined coefficients for the fitting curve can be obtained by fitting the indoor triaxial test results.

[0107] 4) Calculate the updated value of the friction angle of each unit according to the radial stress of each unit calculated in step 5 and the anchor parameters of the tunnel rock anchor bearing arch:

[0108]

[0109] Where: Update the friction angle corresponding to the unit, (°); and The undetermined coefficients for the fitting curve can be obtained by fitting the indoor triaxial test results.

[0110] Step 7: Determine whether each unit participates in the numerical calculation of the i-th step.

[0111] The specific steps include:

[0112] 1) Determine whether each unit participates in the numerical calculation of the i-th step, taking FLAC 3D software and ABAQUS software as examples, and other software are similar;

[0113] 2) Taking FLAC 3D software as an example, if the constitutive model of a unit is a null model, the unit will not participate in the numerical calculation of step i, otherwise it will participate;

[0114] 3) Taking ABAQUS software as an example, if the status of a unit is set to "kill" in the i-th step, the unit will not participate in the numerical calculation of the i-th step, otherwise it will participate.

[0115] Step 8: If the unit participates in the numerical calculation of step i, the updated mechanical parameters of the unit are assigned; otherwise, the mechanical parameters of the unit remain unchanged.

[0116] The specific steps include:

[0117] 1) According to the identification results of all units in step 7, if the unit participates in the numerical calculation of step i, the updated mechanical parameters of the unit are assigned:

[0118] E i =E update (7)

[0119] v i =v update (8)

[0120] c i =c update (9)

[0121]

[0122] Where: E i is the elastic modulus value corresponding to the unit in the numerical calculation of the i-th step, (Pa); v i is the Poisson's ratio corresponding to the unit in the numerical calculation of step i; c i is the cohesion value corresponding to the unit in the numerical calculation of the i-th step, (Pa); is the friction angle value corresponding to the unit in the numerical calculation of step i, (°);

[0123] 2) According to the identification results of all units in step 7, if the unit does not participate in the numerical calculation of step i, the mechanical parameters of the unit will not change:

[0124] E i =E i-1 (11)

[0125] v i =v i-1 (12)

[0126] c i =c i-1 (13)

[0127]

[0128] Where: E i-1 is the elastic modulus value corresponding to the unit in the numerical calculation of step i-1, (Pa); v i-1 is the Poisson's ratio corresponding to the unit in the numerical calculation of step i-1; c i-1 is the cohesion value corresponding to the unit in the numerical calculation of step i-1, (Pa); It is the friction angle value corresponding to the unit in the numerical calculation of the i-1th step, (°).

[0129] Step 9: Determine whether the numerical calculation of the i-th step of the numerical model converges.

[0130] The specific steps include:

[0131] 1) Whether the numerical calculation of the i-th step of the numerical model converges, taking FLAC 3D software and ABAQUS software as examples, and other software are similar;

[0132] 2) Taking FLAC 3D software as an example, if the unbalanced force ratio of the model calculated in the i-th step is less than 1e-5, the model calculation converges, otherwise it does not converge;

[0133] 3) Taking ABAQUS software as an example, if the model calculation time of the i-th step numerical calculation reaches the set model calculation time, the model calculation converges, otherwise it does not converge.

[0134] Step 10: If the numerical calculation of the numerical model in step i converges, the calculation process is terminated; otherwise, the numerical calculation of step i+1 is carried out.

[0135] The embodiment of the present invention is based on the calculation process of numerical calculation and the change law of surrounding rock mechanical parameters with surrounding rock stress and anchor parameters, and establishes a numerical calculation method for tunnel rock anchor bearing arch taking into account the change of surrounding rock mechanical parameters. The method can simply, quickly and accurately consider the change of surrounding rock mechanical parameters with surrounding rock stress in the numerical analysis of tunnel rock anchor bearing arch, which is more in line with engineering practice. Ordinary designers can use this method to design tunnel projects supported by anchors, which has good engineering value.

[0136] Although the present invention has been described in detail with reference to the aforementioned embodiments, it is still possible for those skilled in the art to modify the technical solutions described in the aforementioned embodiments, or to make equivalent substitutions for some of the technical features therein. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the protection scope of the present invention.

Claims

1. A numerical calculation method for tunnel rock anchor bearing arch considering the change of surrounding rock mechanical parameters, characterized in that: The steps include: S1. Establish a numerical calculation model for the tunnel rock anchor bearing arch; S2, carry out the i-th step numerical calculation according to the established tunnel rock anchor bearing arch numerical model; S3, traverse all the units in the numerical model of the tunnel rock anchor bearing arch; S4, extracting the corresponding stress components and centroid coordinates of each unit; S5. Calculate the radial stress of each unit according to the extracted stress components and centroid coordinates of each unit; S6. Calculate the updated value of the mechanical parameters of each unit according to the calculated radial stress of each unit and the anchor rod parameters of the tunnel rock anchor bearing arch; S7, determining whether each unit participates in the numerical calculation of the i-th step; S8. If the unit participates in the numerical calculation of step i, the updated mechanical parameters of the unit are assigned, otherwise the mechanical parameters of the unit remain unchanged; S9, judging whether the numerical calculation of the numerical model step i has converged; S10. If the numerical calculation of the numerical model in step i converges, the calculation process is terminated; otherwise, the numerical calculation of step i+1 is carried out.

2. A method for numerically calculating the bearing arch of a tunnel rock anchor taking into account the change of surrounding rock mechanical parameters according to claim 1, characterized in that: The step S1 specifically includes: S11, establishing a corresponding geometric model according to the size of the tunnel rock anchor bearing arch numerical model, and dividing the grid according to the geometric model; S12. Assign initial computational mechanics parameters to the model based on geological survey data and specifications; S13. Assign boundary conditions to the numerical model of the tunnel rock anchor bearing arch and start calculation.

3. The method for numerically calculating the bearing arch of a tunnel rock anchor taking into account the change of mechanical parameters of the surrounding rock according to claim 1, characterized in that: The step S2 specifically includes: S21, carry out the first step of numerical calculation based on the established tunnel rock anchor bearing arch numerical model; S22, performing the second step of numerical calculation based on the numerical calculation result of the first step; S23. Carry out the i-th step numerical calculation based on the result of the i-1-th step numerical calculation until the model calculation converges.

4. The method for numerically calculating the bearing arch of a tunnel rock anchor taking into account the change of mechanical parameters of the surrounding rock according to claim 1, characterized in that: The step S3 specifically includes: S31, traversing all units of the tunnel rock anchor bearing arch value based on programming; S32. Filter out the solid units whose constitutive model is the surrounding rock among all the units.

5. The method for numerically calculating the bearing arch of a tunnel rock anchor taking into account the change of mechanical parameters of the surrounding rock according to claim 1, characterized in that: The step S4 specifically includes: S41, according to all the surrounding rock entity units traversed in step S3, extract the stress components of each unit, including stress in the xx direction, stress in the yy direction, stress in the zz direction, stress in the xy direction, stress in the xz direction and stress in the yz direction; S42. According to all the surrounding rock entity units traversed in step S3, extract the id and centroid coordinates of each unit, wherein the centroid coordinates include x, y and z.

6. The method for numerically calculating the bearing arch of a tunnel rock anchor taking into account the change of mechanical parameters of the surrounding rock according to claim 1, characterized in that: The step S5 specifically includes: S51: Calculate the polar coordinate angle of each unit according to the centroid coordinates of each unit extracted in step S4: θ=F1(x,y,z) (1) Where: F1(x) is the polar coordinate angle calculation function of the unit; x is the x coordinate value of the unit; y is the y coordinate value of the unit; z is the z coordinate value of the unit; θ is the polar coordinate angle of the unit; S52: Calculate the radial stress of each unit according to the stress component and polar coordinate angle of each unit extracted in step S4: s r =F2(σ xx ,s yy ,s zz ,t xy ,t xz ,t yz ,i) (2) Where: F2(x) is the radial stress calculation function of the unit; σ r is the radial stress of the unit; σ xx is the stress of the unit along the xx direction; σ yy is the stress of the unit along the yy direction; σ zz is the stress of the unit along the zz direction; τ xy is the stress of the unit along the xy direction; τ xz is the stress of the unit along the xz direction; τ yz is the stress of the element along the yz direction.

7. The method for numerically calculating the bearing arch of a tunnel rock anchor taking into account the change of mechanical parameters of the surrounding rock according to claim 1, characterized in that: The step S6 specifically includes: S61, calculating the updated value of the elastic modulus of each unit according to the radial stress of each unit calculated in step S5 and the anchor rod parameters of the tunnel rock anchor bearing arch: AND update =G1(σ r ,F b ) (3) Where: G1(x) is the calculation function of the elastic modulus and radial stress of the unit and the anchor parameters; E update Update the value of the elastic modulus corresponding to the element; F b is the anchor prestress value of the tunnel rock anchor bearing arch; S62, calculating the updated value of the Poisson's ratio of each unit according to the radial stress of each unit calculated in step S5 and the anchor rod parameters of the tunnel rock anchor bearing arch: v update =G2(σ r ,F b ) (4) Where: G2(x) is the calculation function of the unit's Poisson's ratio, radial stress and anchor parameters; v update Update the Poisson's ratio corresponding to the unit; S63, calculating the updated value of the cohesion of each unit according to the radial stress of each unit calculated in step S5 and the anchor parameters of the tunnel rock anchor bearing arch: c update =G3(σ r ,F b ) (5) Where: G3(x) is the calculation function of the unit cohesion and radial stress as well as anchor parameters; c update Update the cohesion value corresponding to the unit; S64, calculating the updated value of the friction angle of each unit according to the radial stress of each unit calculated in step S5 and the anchor rod parameters of the tunnel rock anchor bearing arch: Where: G4(x) is the calculation function of the friction angle and radial stress of the unit and the anchor parameters; Update the value of the friction angle corresponding to the element.

8. The method for numerically calculating the bearing arch of a tunnel rock anchor taking into account the change of mechanical parameters of the surrounding rock according to claim 1, characterized in that: The step S7 specifically includes: determining whether each unit participates in the numerical calculation of the i-th step. In the FLAC3D software, if the constitutive model of a unit is a null model, the unit does not participate in the numerical calculation of the i-th step, otherwise it participates; in the ABAQUS software, if the state of a unit in the i-th step is set to "kill", the unit does not participate in the numerical calculation of the i-th step, otherwise it participates.

9. The method for numerically calculating the bearing arch of a tunnel rock anchor taking into account the change of mechanical parameters of the surrounding rock according to claim 1, characterized in that: The step S8 specifically includes: S81. According to the identification results of all units in step S7, if the unit participates in the numerical calculation of step i, the updated mechanical parameters of the unit are assigned: AND i =And update (7) v i =v update (8) c i =c update (9) Where: E i is the elastic modulus value corresponding to the unit in the numerical calculation of step i; v i is the Poisson's ratio corresponding to the unit in the numerical calculation of step i; c i is the cohesion value corresponding to the unit in the numerical calculation of step i; is the friction angle value corresponding to the unit in the numerical calculation of step i; S82. According to the identification results of all units in step S7, if the unit does not participate in the numerical calculation of step i, the mechanical parameters of the unit do not change: AND i =And i-1 (11) v i =v i-1 (12) c i =c i-1 (13) Where: E i-1 is the elastic modulus value corresponding to the unit in the numerical calculation of step i-1; v i-1 is the Poisson's ratio corresponding to the unit in the numerical calculation of step i-1; c i-1 is the cohesion value corresponding to the unit in the numerical calculation of step i-1; It is the friction angle value corresponding to the unit in the numerical calculation of the i-1th step.

10. The method for numerically calculating the bearing arch of a tunnel rock anchor taking into account the change of mechanical parameters of the surrounding rock according to claim 1, characterized in that: The step S9 specifically includes: whether the numerical calculation of the i-th step of the numerical model converges. In the FLAC 3D software, if the model unbalanced force ratio of the i-th step numerical calculation is less than 1e-5, the model calculation converges, otherwise it does not converge; in the ABAQUS software, if the model calculation time of the i-th step numerical calculation reaches the set model calculation time, the model calculation converges, otherwise it does not converge.

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