A prestressed anchor rod support simulation method

Abstract

The present application relates to a kind of prestressed anchor rod support simulation method, belong to roadway surrounding rock control field, including using anchor structure unit simulating anchor rod and respectively generating surrounding rock action section anchor rod, tray action section anchor rod, tray outside section anchor rod;Surrounding rock action section anchor rod, tray action section anchor rod, tray outside section anchor rod are sequentially connected;All anchor structure unit is set material parameter;Setting anchor structure unit material parameter of ID as 1;In the range of anchor structure unit of ID as 2, generate mesh, and be named as "plate";ID is generated on the inside surface of "plate" mesh 10 demarcation surface;Setting demarcation surface material parameter of ID as 10;"plate" grid constitutive model and material parameter are set;Apply tension;Normal stress is applied to the outside surface of "plate" grid;Define and execute fish function checking, whether it has successfully applied prestress is checked using it.The present application can effectively simulate prestressed anchor rod support, and it has important significance to reveal prestressed anchor rod support action principle etc..

Description

Technical Field

[0001] This invention belongs to the field of roadway surrounding rock control, specifically relating to a simulation method for prestressed anchor bolt support. Background Technology

[0002] Prestressed rock bolt support is a commonly used technique in the field of roadway surrounding rock control, playing a crucial role in the reinforcement of surrounding rock in roadways and chambers. In prestressed rock bolt support, prestressed rock bolts need to be used in conjunction with a support plate. When the rock bolt is tensioned, the support plate is compressed and applies compressive normal stress to the surrounding rock, thereby exerting an active restraint effect on the surrounding rock and controlling its deformation.

[0003] With the rapid development of numerical simulation technology, researchers have proposed various numerical simulation methods for anchor bolt support. However, existing research generally focuses on the contact between the anchor bolt itself and the surrounding rock, neglecting the interaction between the anchor bolt, the support plate, and the surrounding rock. To address this issue, a few researchers have conducted research from the following three aspects.

[0004] The first method involves setting the cohesive force of the anchoring agent at the contact point between the outer side of the anchor bolt and the surrounding rock wall to be extremely high. This method bonds the outer side of the anchor bolt to the surrounding rock wall, thus simulating a pallet connecting the outer side of the anchor bolt to the rock wall. However, this method oversimplifies the pallet and has several drawbacks. First, by setting the anchoring agent cohesive force at a specific point to simulate a pallet, it only considers the connection between the anchor bolt and the surrounding rock at that point, failing to reflect the restraining effect of the pallet on the surrounding rock over its surface area. Second, in actual working conditions, construction workers can use pallets with different surface areas to achieve different control effects on the surrounding rock. Setting the anchoring agent cohesive force at a specific point to be extremely high fails to reflect the differences in the control effects of pallets with different surface areas on the surrounding rock.

[0005] To address the shortcomings of the first method, a second simulation approach was proposed, using shell or liner elements to simulate the pallet and connect it to the anchor bolt. However, this method also has its limitations. First, the shell or liner elements need to be attached to the mesh surface for generation. Considering the pallet's shape (e.g., circular, triangular, square) and surface area, the mesh in contact with the pallet needs to be divided into specified shapes and surface areas, increasing the difficulty of mesh generation. Second, the connection between the shell / liner elements and the anchor bolt requires that the shell / liner nodes and anchor bolt nodes be concurrent, further complicating the mesh generation process. Furthermore, in actual working conditions, the pallet may detach from the anchor bolt after being compressed by the surrounding rock, resulting in pallet slippage failure. Since the shell / liner elements and anchor bolt are rigidly connected, the pallet simulated by the shell / liner elements will not slip off the anchor bolt, which is inconsistent with reality.

[0006] To address the aforementioned shortcomings, a third simulation method was proposed. This method assumes elastic deformation of the surrounding rock and anchor bolts during prestressing; establishes a model of anchor bolt support; applies tension after removing the support plate; then reinstalls the support plate and removes the tension. However, certain limitations remain. First, the surrounding rock is an elastoplastic material. If the surrounding rock is in a loose and fractured state, plastic deformation is highly likely to occur near the support plate under high prestress conditions. Therefore, assuming elastic deformation of the surrounding rock during prestressing does not fully reflect actual working conditions. Second, in this simulation method, the compression effect of the support plate on the surrounding rock relies on the elastic recoil of the anchor bolts after tensioning and then removing the tension. In actual working conditions, the tensioning equipment acts on the support plate, followed by the tensioning of the anchor bolts. Therefore, the compression effect of the tensioning equipment on the support plate occurs during the tensioning of the anchor bolts and their elastic elongation. Thus, the simulation's reliance on the elastic recoil of the anchor bolts to compress the support plate does not align with actual working conditions. Furthermore, the simulation process requires removing the tray and applying tension before installing it again and removing the tension. In actual construction, the tray must be installed first, followed by applying tension. This is because once tension is applied to the anchor bolt, the tray, due to its small hollow opening, cannot pass through the tensioning equipment and be installed onto the surrounding rock surface. Therefore, the simulation procedure does not match the actual construction procedure. Finally, this simulation method also fails to consider the issue of tray slippage failure.

[0007] Therefore, this patent proposes a simulation method for prestressed anchor support, which is of great significance for revealing the working principle of prestressed anchor support and reflecting the mechanical relationship between the anchor, the support plate, and the surrounding rock. Summary of the Invention

[0008] The purpose of this invention is to propose a simulation method for prestressed anchor bolt support. This method overcomes the shortcomings of previous simulation methods, such as the inability to effectively simulate the rock tray, the inability to simulate rock tray slippage failure, the fact that the rock tray's squeezing effect on the surrounding rock does not originate from the elastic elongation of the anchor bolt, and the difference between the simulation process and the construction process. This method can effectively simulate prestressed anchor bolt support.

[0009] This invention employs the following technical solution to provide a simulation method for prestressed anchor bolt support, comprising: simulating the anchor bolt using anchor structure elements (cable) and generating the entire anchor bolt in three stages: the rock-acting section anchor bolt, the tray-acting section anchor bolt, and the outer tray section anchor bolt, assigning ID numbers 1, 2, and 3 respectively; sequentially connecting the rock-acting section anchor bolt, the tray-acting section anchor bolt, and the outer tray section anchor bolt using the structure node join command; setting material parameters for all anchor structure elements, including young, cross-sectional-area, yield-tension, and grout-stiffness; setting material parameters for the anchor structure element with ID 1, including grout-cohesion, grout-friction, grout-stiffness, and grout-perimeter; and within the anchor structure element with ID 2, utilizing zone... The `create` command generates a mesh named "plate" to simulate a pallet. An interface with ID 10 is generated on the inner surface of the "plate" mesh. Material parameters for the interface with ID 10 are set, including stiffness-normal, stiffness-shear, cohesion, friction, and tension. The constitutive model of the "plate" mesh is set to an isotropic elastic model, and corresponding material parameters are set, including young, poisson, and density. A tensile force F parallel to the anchor bolt extension direction is applied to the outermost node of the anchor structural element with ID 3 to simulate prestress. A normal stress σ is applied to the outer surface of the "plate" mesh. The `fish` function `checking` is defined and is required to execute automatically at each time step to check whether prestress has been successfully applied.

[0010] As a further description of the above technical solution:

[0011] The rock-supporting section anchor bolt and the tray-supporting section anchor bolt share a common point; the tray-supporting section anchor bolt and the outer section anchor bolt of the tray share a common point.

[0012] As a further description of the above technical solution:

[0013] The number of internal components of the anchor bolt in the surrounding rock action section is greater than or equal to 10; the number of internal components of the anchor bolt in the tray action section is equal to 1; and the number of internal components of the anchor bolt in the outer tray section is equal to 1.

[0014] As a further description of the above technical solution:

[0015] When setting material parameters for all anchor structural units, set grout-stiffness to 1 GPa.

[0016] As a further description of the above technical solution:

[0017] When generating the "plate" mesh using the zone create command, the three-dimensional geometry of the "plate" mesh is consistent with the simulated tray, and the thickness of the "plate" mesh is consistent with the length of the anchor structure element with ID 2.

[0018] As a further description of the above technical solution:

[0019] The inner surface of the "plate" mesh refers to the face of the "plate" mesh closest to the anchor structure unit with ID 1; the outer surface of the "plate" mesh refers to the face of the "plate" mesh closest to the anchor structure unit with ID 3.

[0020] As a further description of the above technical solution:

[0021] In the interface material parameters with ID 10, stiffness-normal and stiffness-shear are both 1 GPa; cohesion and tension are both 0; and friction is set according to the friction coefficient between the tray and the surrounding rock.

[0022] As a further description of the above technical solution:

[0023] When applying a tensile force F to the outermost node of the anchor structural unit with ID 3, the component-id of the outermost node of the anchor structural unit with ID 3 is used for positioning.

[0024] As a further description of the above technical solution:

[0025] The normal stress σ applied to the outer surface of the "plate" mesh is calculated according to the first formula.

[0026] As a further description of the above technical solution:

[0027] The logical structure of the fish function checking is as follows: Define variable n as 0; define variable pnt_structure and assign the anchor structure unit head pointer to variable pnt_structure; traverse all anchor structure units; when traversing to each anchor structure unit, determine whether the anchor structure unit ID pointed to by variable pnt_structure is equal to 3; if yes, determine whether the axial tension of the anchor structure unit pointed to by pnt_structure is greater than or equal to the tension F; if yes, calculate n according to the second formula; after traversing all anchor structure units, determine whether n is equal to the number of anchor rods installed; if yes, remove the tension F from the outer ends of all anchor rods, and set the anchor structure unit grout-cohesion with ID 2 according to the result calculated by the third formula.

[0028] As a further description of the above technical solution:

[0029] The first formula is: Where F is the tensile force applied to the outermost node of the anchor structure unit with ID 3; A is the cross-sectional area of ​​the tray; the second formula is n = n + 1, where n is a variable; the third formula is... Where τ is the shear force per unit length when the tray slips out; F s is the shear force corresponding to the tray slippage failure; l is the tray thickness.

[0030] Beneficial effects

[0031] The main beneficial effects of this invention include:

[0032] (1) Create a "plate" mesh to simulate the pallet. The mesh can be generated according to the shape of the actual pallet, such as a triangular pallet, a circular pallet, a square pallet, etc., so as to better simulate the physical pallet in actual working conditions. Compared with shell elements or lining elements, the "plate" mesh and the surrounding rock mesh are generated independently, so the "plate" mesh does not need to be generated by adhering the surrounding rock mesh. Therefore, when generating and dividing the surrounding rock mesh, there is no need to consider the size and shape of the simulated pallet, which simplifies the generation and division of the surrounding rock mesh.

[0033] (2) An interface with ID 10 was set on the inner side of the "plate" mesh to simulate the contact relationship between the tray and the surrounding rock. A friction parameter was set on the interface with ID 10 to simulate the friction relationship between the inner side of the tray and the surface of the surrounding rock. By setting different friction parameters, the friction between the inner side of the tray and the surface of the surrounding rock with different roughnesses can be simulated.

[0034] (3) For the anchor bolt in the pallet action section, the grout-cohesion parameter is used to define the interaction relationship between the anchor bolt and the pallet. Within the range of the anchor bolt in the pallet action section, the grout-cohesion parameter is calculated from the shear force corresponding to the pallet slippage failure and the pallet thickness. When the shear force between the anchor bolt and the pallet exceeds the shear force corresponding to the pallet slippage failure, the pallet can slip off the anchor bolt and fail, thereby simulating the pallet slippage failure mode.

[0035] (4) Prestressing is achieved by applying a tensile force F to the outermost node of the anchor structure unit with ID 3 and a normal stress σ to the outer surface of the "plate" mesh. The tensile force F and the normal stress σ are applied simultaneously, and the product of the normal stress σ and the cross-sectional area A of the tray is equal to the tensile force F. The two are a pair of action and reaction forces. Compared with the previous research methods, the force exerted by the tray on the surrounding rock no longer relies on the elastic recoil of the anchor rod after being stretched, which is consistent with the actual working conditions.

[0036] (5) In the simulation process, the prestressing application procedure is as follows: first, install the tray, then tension the anchor rod, and immediately apply compressive normal stress to the tray, and finally remove the tension. Compared with the previous simulation process, which involved removing the tray first, then applying tension, then installing the tray again, and finally removing the tension, the procedure used in this simulation process is consistent with the actual prestressing application procedure in engineering.

[0037] (6) The `fish` function `checking` is defined. This function automatically checks whether prestress has been successfully applied to each anchor bolt. Furthermore, after confirming successful prestressing for each anchor bolt, it automatically removes the tensile force F applied to the outermost nodes of all anchor bolts and sets the grout-cohesion parameter for all anchor bolts in the tray action section to simulate the constraint effect of tightening the nuts and the tray after prestressing application. Therefore, the `fish` function `checking` automatically completes the prestressing effect check for each anchor bolt, removes the tensile force F, and sets the grout-cohesion parameter for the tray action section after successful prestressing application, without requiring manual operation.

[0038] (7) The pallet is simulated using a "plate" mesh, which can be set to different side lengths or different surface areas when generated. Therefore, pallets of different sizes can be simulated using "plate" meshes with different side lengths or different surface areas, thereby allowing for the study or optimization of the anchoring effect of pallets of different sizes on the surrounding rock.

[0039] (8) Throughout the entire process of applying prestress, the surrounding rock is an elastic-plastic material, so there is no need to assume that the surrounding rock is an elastic material, which is more consistent with the actual situation. Attached Figure Description

[0040] The accompanying drawings, which constitute a part of this application, are used to provide a further understanding of the invention and do not constitute an undue limitation of the invention. In the drawings:

[0041] Figure 1 This is a schematic diagram of a prestressed anchor rod according to the present invention.

[0042] Figure 2 This is a schematic diagram of the square tray described in this invention.

[0043] Figure 3 This is a diagram showing the interaction between the tensile force F and the normal stress σ applied to the outer surface of the "plate" grid when applying prestress, as described in this invention.

[0044] Figure 4 This is the logical structure diagram of the fish function checking described in this invention.

[0045] Figure 5 This is the rectangular tunnel excavation model described in this invention.

[0046] In the diagram: 1. Anchor bolt in the rock-affected section; 2. Anchor bolt in the tray-affected section; 3. Anchor bolt on the outer side of the tray; 4. Tray; 5. Anchor bolt node; 6. Interface with ID 10. Detailed Implementation

[0047] like Figure 1As shown, this invention provides a simulation method for prestressed anchor bolt support, comprising: simulating the anchor bolt using anchor structure elements (cable) and generating the entire anchor bolt in three stages, namely, anchor bolt 1 in the surrounding rock action section, anchor bolt 2 in the tray action section, and anchor bolt 3 in the outer section of the tray, and assigning ID numbers 1, 2, and 3 respectively; sequentially connecting anchor bolt 1 in the surrounding rock action section, anchor bolt 2 in the tray action section, and anchor bolt 3 in the outer section of the tray using the structure node join command; setting material parameters for all anchor structure elements, including young, cross-sectional-area, yield-tension, and grout-stiffness; setting material parameters for the anchor structure element with ID 1, including grout-cohesion, grout-friction, grout-stiffness, and grout-perimeter; and within the anchor structure element with ID 2, using zone... The `create` command generates a mesh named "plate" to simulate a pallet. Interface 6 with ID 10 is generated on the inner surface of the "plate" mesh. Material parameters for interface 6 with ID 10 are set, including stiffness-normal, stiffness-shear, cohesion, friction, and tension. The constitutive model of the "plate" mesh is set to an isotropic elastic model, and corresponding material parameters are set, including young, poisson, and density. A tensile force F parallel to the anchor bolt extension direction is applied to the outermost node of the anchor structure element with ID 3 to simulate prestress. Normal stress σ is applied to the outer surface of the "plate" mesh. The `fish` function `checking` is defined and is required to execute automatically at each time step to check whether prestress has been successfully applied.

[0048] In one specific embodiment:

[0049] The rock-supporting section anchor 1 and the tray-supporting section anchor 2 share a common point; the tray-supporting section anchor 2 and the outer section anchor 3 of the tray share a common point.

[0050] In one specific embodiment:

[0051] The number of internal components of the rock-supporting section anchor 1 is greater than or equal to 10; the number of internal components of the tray-supporting section anchor 2 is equal to 1; and the number of internal components of the tray-outer section anchor 3 is equal to 1.

[0052] In one specific embodiment:

[0053] When setting material parameters for all anchor structural units, set grout-stiffness to 1 GPa.

[0054] In one specific embodiment:

[0055] When generating the "plate" mesh using the zone create command, the three-dimensional geometry of the "plate" mesh is consistent with the simulated tray, and the thickness of the "plate" mesh is consistent with the length of the anchor structure element with ID 2.

[0056] In one specific embodiment:

[0057] The inner surface of the "plate" mesh refers to the face of the "plate" mesh closest to the anchor structure unit with ID 1; the outer surface of the "plate" mesh refers to the face of the "plate" mesh closest to the anchor structure unit with ID 3.

[0058] In one specific embodiment:

[0059] In the interface material parameters of ID 10, stiffness-normal and stiffness-shear are both 1 GPa; cohesion and tension are both 0; and friction is set according to the friction coefficient between the tray and the surrounding rock.

[0060] In one specific embodiment:

[0061] When applying a tensile force F to the outermost node of the anchor structural unit with ID 3, the component-id of the outermost node of the anchor structural unit with ID 3 is used for positioning.

[0062] In one specific embodiment:

[0063] The normal stress σ applied to the outer surface of the "plate" mesh is calculated according to the first formula.

[0064] In one specific embodiment:

[0065] The logical structure of the fish function checking is as follows: Define variable n as 0; define variable pnt_structure and assign the anchor structure unit head pointer to variable pnt_structure; traverse all anchor structure units; when traversing to each anchor structure unit, determine whether the anchor structure unit ID pointed to by variable pnt_structure is equal to 3; if yes, determine whether the axial tension of the anchor structure unit pointed to by pnt_structure is greater than or equal to the tension F; if yes, calculate n according to the second formula; after traversing all anchor structure units, determine whether n is equal to the number of anchor rods installed; if yes, remove the tension F from the outer ends of all anchor rods, and set the anchor structure unit grout-cohesion with ID 2 according to the result calculated by the third formula.

[0066] In one specific embodiment:

[0067] The first formula is: Where F is the tensile force applied to the outermost node of the anchor structure unit with ID 3; A is the cross-sectional area of ​​the tray; the second formula is n = n + 1, where n is a variable; the third formula is... Where τ is the shear force per unit length when the tray slips out; F s is the shear force corresponding to the tray slippage failure; l is the tray thickness.

[0068] To verify the validity of this invention patent, a rectangular tunnel excavation model was constructed, as follows: Figure 5 As shown. The entire model is 30m wide and high, and 0.5m thick. The entire model is set as a Mohr-Coulomb model, and the material parameters are set, including Young's modulus of 12GPa, Poisson's ratio of 0.2, cohesion of 1.5MPa, internal friction angle of 28°, tensile strength of 0.8MPa, and density of 2700kg / m³. 3 The front, back, left, right, and bottom of the entire model are set to roller support boundary conditions, and the top of the model is set to a compressive stress boundary condition of 15 MPa. The gravitational acceleration of the entire model is set to 10 m / s². 2 The plumb bob is pointing downwards. Initial stress equilibrium is set, and the large deformation calculation mode is set to false. The model is automatically calculated until stress equilibrium is reached. Subsequently, a rectangular tunnel with a width of 5m and a height of 4m is excavated in the center of the entire model using the mesh deletion method.

[0069] For comparison, a traditional method was first used to simulate prestressed anchor bolt support. Anchor bolts were simulated using anchor structure elements (cable) to support the left, right, and roof of a rectangular roadway, with 4, 4, and 5 anchor bolts respectively for the left, right, and roof. Each anchor bolt was 2.71m long, with 2.5m penetrating the surrounding rock (ID 1) and 0.21m extending beyond the surrounding rock (ID 3). The structure node join command was used to connect the anchor structure elements with IDs 1 and 3. Material parameters for all anchor structure elements were set, including young = 200 GPa and cross-sectional area = 380.13 mm. 2The yield-tension is 250 kN, and the grout-stiffness is 1 GPa. Material parameters are set for the anchor structure element with ID 1, including grout-cohesion of 100 kN / m, grout-friction of 32°, grout-stiffness of 100 MPa, and grout-perimeter of 69.12 mm. The grout-cohesion parameter is set to a very large value of 1 GPa for the anchor structure element with ID 1 at the contact point with the surrounding rock surface of the rectangular tunnel, to simulate the pallet and connect the surrounding rock to the anchor bolt.

[0070] A tensile force of 100 kN was applied to the outermost nodes of all anchor structural units to simulate prestress. Calculations were performed until stress equilibrium was reached. After stress equilibrium was achieved, the volume of the plastic zone around the rectangular tunnel was determined to be 40 m³. 3 The maximum deformation of the roadway was 15.91 mm; the convergence of the roof and floor was 23.83 mm; and the convergence of the sidewalls was 24.37 mm.

[0071] Subsequently, the newly excavated rectangular tunnel was supported by prestressed anchor bolts using the present invention. The length and installation position of each anchor bolt were consistent with the conventional method described above. However, each anchor bolt was divided into three parts: anchor bolt 1, which penetrates into the surrounding rock and has a length of 2.5m and ID number 1; anchor bolt 2, which extends 0.01m outward from the surrounding rock and has a support plate and ID number 2; and anchor bolt 3, which extends outward from the support plate and has a length of 0.2m and ID number 3. The number of anchor structure unit components with IDs 1, 2, and 3 were 10, 1, and 1, respectively.

[0072] Use the `structure node join` command to connect the anchor structural elements with IDs 1, 2, and 3 at their common points. Set the material parameters for all anchor structural elements, and set the material parameters for the anchor structural element with ID 1 to the same values ​​as in the traditional method described above.

[0073] Within the anchor structural unit with ID 2, a "plate" square mesh is generated using the "zone create" command. The mesh width, height, and thickness are 150mm, 150mm, and 10mm, respectively, to simulate a square pallet. Figure 2 As shown. An interface 6 with ID 10 is generated on the inner surface of the "plate" mesh. The material parameters of interface 6 with ID 10 are set, including stiffness-normal = 1 GPa; stiffness-shear = 1 GPa; cohesion = 0; friction = 32°; tension = 0.

[0074] The "plate" mesh constitutive model is set as an isotropic elastic model, and the corresponding material parameters are set, including young = 200 GPa; poisson = 0.2; density = 7800 kg / m³. 3 A tensile force F of 100 kN, parallel to the anchor bolt extension direction, is applied to the outermost node of the anchor structural unit with ID 3 to simulate prestress. Figure 3 As shown. A normal stress σ is applied to the outer surface of the "plate" mesh, which, calculated according to the first formula, has a magnitude of 4.44 MPa. The fish function checking is defined, and its logical structure is as follows. Figure 4 As shown. The `fish` function `checking` is required to execute automatically at each time step to check whether prestress has been successfully applied. When the value of `n` in the `fish` function `checking` is equal to the number of anchor bolts installed, i.e., 13, the tension F at the outer ends of all anchor bolts is removed, and the grout-cohesion of the anchor structure element with ID 2 is set to 20MN / m.

[0075] The model was calculated until stress equilibrium was reached. After reaching stress equilibrium, the calculation results were checked and found that the volume of the plastic zone in the surrounding rock of the rectangular tunnel was 34.25 m³. 3 The results show a 14.4% decrease compared to traditional methods. The maximum tunnel deformation is 14.37 mm, a 9.7% decrease compared to traditional methods. The roof and floor convergence is 22.14 mm, a 7.1% decrease compared to traditional methods. The sidewall convergence is 20.55 mm, a 15.7% decrease compared to traditional methods. It can be seen that after simulating prestressed rock bolt support using this invention, the prestressing and support plate significantly restrain the surrounding rock. Compared to traditional methods, the volume of the plastic zone and the deformation of the surrounding rock are significantly reduced. This indicates that the simulation results of this invention better reflect the anchoring effect of prestressed rock bolts and support plates on the surrounding rock, and are more consistent with actual conditions.

[0076] Furthermore, since the "plate" mesh in this invention is generated independently using the zone create command, there are no requirements regarding the mesh size or the number of elements in the surrounding rock of the tunnel. Therefore, "plate" meshes of different sizes can be generated to simulate trays with different surface areas. In the above calculations, the "plate" mesh has a side length of 150 mm, which translates to a surface area of ​​0.0225 m². 2 To verify that the present invention can effectively simulate the control effect of different sized plates on the surrounding rock of a roadway, this case was further calculated using the present invention. During the calculation, other parameters remained unchanged, but the side length of the "plate" mesh was modified to 300mm, i.e., the surface area was 0.09m². 2 The model was calculated to stress equilibrium. Upon reaching stress equilibrium, the calculation results were examined, revealing that the volume of the plastic zone in the surrounding rock of the rectangular roadway was 26.5 m³.3 Compared to traditional methods, the deformation decreased by 33.8%. The maximum tunnel deformation was 12.42 mm, a decrease of 21.9% compared to traditional methods. The roof and floor convergence was 19.97 mm, a decrease of 16.2% compared to traditional methods. The sidewall convergence was 15.59 mm, a decrease of 36% compared to traditional methods. It can be seen that after using larger pallets to secure the surrounding rock, under prestressing, the volume of the plastic zone in the surrounding rock and the tunnel deformation further decreased. This indicates that using larger surface area pallets can better control the surrounding rock, which is consistent with the fact that using larger surface area pallets in field construction often yields better support. Therefore, this demonstrates both the effectiveness of the invention and its ability to effectively study and optimize the control effect of pallet size on the surrounding rock.

[0077] In summary, due to the adoption of the above technical solution, the beneficial effects of the present invention include:

[0078] (1) Create a "plate" mesh to simulate the pallet. The mesh can be generated according to the shape of the actual pallet, such as a triangular pallet, a circular pallet, a square pallet, etc., so as to better simulate the physical pallet in actual working conditions. Compared with shell elements or lining elements, the "plate" mesh and the surrounding rock mesh are generated independently, so the "plate" mesh does not need to be generated by adhering the surrounding rock mesh. Therefore, when generating and dividing the surrounding rock mesh, there is no need to consider the size and shape of the simulated pallet, which simplifies the generation and division of the surrounding rock mesh.

[0079] (2) An interface with ID 10 was set on the inner side of the "plate" mesh to simulate the contact relationship between the tray and the surrounding rock. A friction parameter was set on the interface with ID 10 to simulate the friction relationship between the inner side of the tray and the surface of the surrounding rock. By setting different friction parameters, the friction between the inner side of the tray and the surface of the surrounding rock with different roughnesses can be simulated.

[0080] (3) For the anchor bolt in the pallet action section, the grout-cohesion parameter is used to define the interaction relationship between the anchor bolt and the pallet. Within the range of the anchor bolt in the pallet action section, the grout-cohesion parameter is calculated from the shear force corresponding to the pallet slippage failure and the pallet thickness. When the shear force between the anchor bolt and the pallet exceeds the shear force corresponding to the pallet slippage failure, the pallet can slip off the anchor bolt and fail, thereby simulating the pallet slippage failure mode.

[0081] (4) Prestressing is achieved by applying a tensile force F to the outermost node of the anchor structure unit with ID 3 and a normal stress σ to the outer surface of the "plate" mesh. The tensile force F and the normal stress σ are applied simultaneously, and the product of the normal stress σ and the cross-sectional area A of the tray is equal to the tensile force F. The two are a pair of action and reaction forces. Compared with the previous research methods, the force exerted by the tray on the surrounding rock no longer relies on the elastic recoil of the anchor rod after being stretched, which is consistent with the actual working conditions.

[0082] (5) In the simulation process, the prestressing application procedure is as follows: first, install the tray, then tension the anchor rod, and immediately apply compressive normal stress to the tray, and finally remove the tension. Compared with the previous simulation process, which involved removing the tray first, then applying tension, then installing the tray again, and finally removing the tension, the procedure used in this simulation process is consistent with the actual prestressing application procedure in engineering.

[0083] (6) The `fish` function `checking` is defined. This function automatically checks whether prestress has been successfully applied to each anchor bolt. Furthermore, after confirming successful prestressing for each anchor bolt, it automatically removes the tensile force F applied to the outermost nodes of all anchor bolts and sets the grout-cohesion parameter for all anchor bolts in the tray action section to simulate the constraint effect of tightening the nuts and the tray after prestressing application. Therefore, the `fish` function `checking` automatically completes the prestressing effect check for each anchor bolt, removes the tensile force F, and sets the grout-cohesion parameter for the tray action section after successful prestressing application, without requiring manual operation.

[0084] (7) The pallet is simulated using a "plate" mesh, which can be set to different side lengths or different surface areas when generated. Therefore, pallets of different sizes can be simulated using "plate" meshes with different side lengths or different surface areas, thereby allowing for the study or optimization of the anchoring effect of pallets of different sizes on the surrounding rock.

[0085] (8) Throughout the entire process of applying prestress, the surrounding rock is an elastic-plastic material, so there is no need to assume that the surrounding rock is an elastic material, which is more consistent with the actual situation.

[0086] This invention is not limited to the preferred embodiments described above. Anyone can derive other forms of products under the guidance of this invention. However, regardless of any changes made in their shape or structure, any technical solution that is the same as or similar to this application falls within the protection scope of this invention.

Claims

1. A method of prestressed rock bolt support simulation, characterized by: The anchor structure unit is used to simulate the anchor rod and the whole anchor rod is generated in three times, which are the surrounding rock acting section anchor rod (1), the tray acting section anchor rod (2) and the tray outside section anchor rod (3), and the ID numbers are set as 1, 2 and 3 respectively; the structure node join command is used to connect the surrounding rock acting section anchor rod (1), the tray acting section anchor rod (2) and the tray outside section anchor rod (3) in sequence; the material parameters of all the anchor structure units are set, including young, cross-sectional-area, yield-tension and grout-stiffness; the material parameters of the anchor structure unit with ID 1 are set, including grout-cohesion, grout-friction, grout-stiffness and grout-perimeter; the mesh is generated in the range of the anchor structure unit with ID 2 by using the zone create command and is named as "plate", which is used to simulate the tray; the interface (6) with ID 10 is generated on the inner side of the "plate" mesh; the material parameters of the interface (6) with ID 10 are set, including stiffness-normal, stiffness-shear, cohesion, friction and tension; the constitutive model of the "plate" mesh is set as the isotropic elastic model and the corresponding material parameters are set, including young, poisson and density; the tension parallel to the extension direction of the anchor rod is applied to the outermost node of the anchor structure unit with ID 3 , so as to simulate the prestress; the normal stress is applied to the outer side of the "plate" mesh ; the fish function checking is defined, which is required to be automatically executed at each time step to check whether the prestress has been successfully applied; the normal stress applied to the outer side of the "plate" mesh is calculated according to the first formula ; the first formula is: , wherein is the tension applied to the outermost node of the anchor structure unit with ID 3; is the cross-sectional area of the tray.

2. The pre-stressed rock bolt support simulation method of claim 1, wherein, The surrounding rock action section anchor rod (1) and the tray action section anchor rod (2) have a common point; the tray action section anchor rod (2) and the tray outside section anchor rod (3) have a common point.

3. The pre-stressed rock bolt support simulation method of claim 1, wherein, The number of internal components of the surrounding rock action section anchor rod (1) is greater than or equal to 10; the number of internal components of the tray action section anchor rod (2) is equal to 1; and the number of internal components of the tray outside section anchor rod (3) is equal to 1.

4. The pre-stressed rock bolt support simulation method of claim 1, wherein, When setting the material parameters of all anchor structure units, the grout-stiffness is set to 1 GPa.

5. The pre-stressed rock bolt support simulation method of claim 1, wherein, When generating the "plate" grid by using the zonecreate command, the three-dimensional geometry of the "plate" grid is consistent with the tray to be simulated, and the thickness of the "plate" grid is consistent with the length of the anchor structure unit with ID 2.

6. The pre-stressed rock bolt support simulation method of claim 1, wherein, The inside surface of the "plate" grid refers to the surface of the "plate" grid close to the anchor structure unit with ID 1; and the outside surface of the "plate" grid refers to the surface of the "plate" grid close to the anchor structure unit with ID 3.

7. The pre-stressed rock bolt support simulation method of claim 1, wherein, In the material parameters of the ID 10 interface (6), the stiffness-normal and the stiffness-shear are both 1 GPa; the cohesion and the tension are both 0; and the friction is set according to the friction coefficient between the tray and the surrounding rock.

8. The pre-stressed rock bolt support simulation method of claim 1, wherein, Apply a pull force to the outermost node of the anchor structure unit with ID 3 When the component-id of the outermost node of the anchor structure unit with ID 3 is used for positioning.

9. The pre-stressed rock bolt support simulation method of claim 1, wherein, The fish function checking logic structure is as follows: defining a variable is 0; defining a variable pnt_structure and assigning the anchor structure unit header pointer to the variable pnt_structure; traversing all anchor structure units; when traversing to each anchor structure unit, judging whether the anchor structure unit ID number pointed to by the variable pnt_structure is equal to 3; if yes, judging whether the axial tension of the anchor structure unit pointed to by pnt_structure is greater than or equal to the tension ; If yes, calculate according to the second formula ; After all the anchor structure units are traversed, it is determined whether the number of installed anchor rods is equal to the number of anchor structure units If yes, the pulling force of all the outer heads of the anchor rods is removed , and the grout-cohesion of the anchor structure unit with ID 2 is set according to the calculation result of the third formula; the second formula is , wherein is a variable; the third formula is , wherein is the shear force per unit length when the tray slips off and fails; is the corresponding shear force when the tray slips off and fails; is the thickness of the tray.

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