A numerical simulation method for tunnel support structure considering bond-slip

Abstract

The invention discloses a numerical simulation method for a tunnel support structure considering bonding and slippage, and the method comprises the following steps: determining material parameters of concrete, steel mesh and steel arch frame in the tunnel support structure, establishing bonding and slippage constitutive models between concrete and steel mesh and between concrete and steel arch frame, constructing a finite element analysis model, inserting contact units between the concrete and steel mesh and between the concrete and steel arch frame in the finite element analysis model respectively, determining the total contact area between the contact units and the concrete in the finite element model, setting mid-span pads and boundary pads in the finite element model, constraining the degrees of freedom of the boundary pads in all directions, constraining the degrees of freedom of the mid-span pads in all directions except the vertical direction, applying a vertical displacement load to the mid-span pads, calculating a damage judgment standard value according to the damage area of ​​the contact units and the total contact area after the contact units reach a preset damage standard, and evaluating whether the tunnel is unstable according to the damage judgment standard value.

Description

Technical Field

[0001] The invention relates to the field of tunnel support, and in particular to a numerical simulation method for a tunnel support structure taking bond slip into consideration. Background Art

[0002] Tunnel lining includes single-layer lining and composite lining, and the latter is currently mostly used. However, during the construction process, it is inconvenient to construct the secondary lining and the arch top is not densely cast. Therefore, it is possible to consider using only single-layer lining, which can not only ensure construction safety but also improve economy. The tunnel single-layer lining support structure composed of steel arch frame, steel mesh and concrete mainly relies on natural bonding to transmit force to ensure that they can work together. However, the bonding force between the steel arch frame and concrete is smaller than that between the steel mesh and concrete. When subjected to the pressure of the surrounding rock, the steel arch frame, the steel mesh and the concrete will produce relative slip due to the deformation difference, and the lack of stirrups can easily cause the concrete to fall off. The coordinated bearing effect between the three is complex. The current numerical simulation does not consider the bond slip, or uses nonlinear springs to simulate the bond slip, but it is difficult and complex to model. Therefore, it has become an urgent issue to design a method that can simulate the bond slip value between the steel arch frame, steel mesh and concrete as an important basis for determining the stability of the tunnel support structure. Summary of the invention

[0003] The purpose of the present invention is to overcome the deficiencies of the prior art and to provide a numerical simulation method for a tunnel support structure taking bond-slip into consideration.

[0004] The purpose of the present invention is mainly achieved through the following technical solutions:

[0005] In a first aspect, the present application provides a method for numerical simulation of a tunnel support structure taking into account bond slip, the method comprising the following steps:

[0006] Determine the material parameters of concrete, steel mesh and steel arch in the tunnel support structure through mechanical property tests;

[0007] The bond-slip constitutive model is selected based on the bond-slip relationship between concrete and steel mesh, and the bond-slip relationship between concrete and steel arch frame;

[0008] A finite element analysis model including reinforced concrete beams is constructed according to the tunnel support structure. The relative distribution positions of the reinforced concrete beams and the concrete, steel mesh and steel arch frames in the tunnel support structure are consistent.

[0009] Assign the plastic damage model to the finite element analysis model;

[0010] Insert contact elements as bond-slip layers between concrete and steel mesh in the finite element analysis model, and insert contact elements between concrete and steel arches in the finite element analysis model;

[0011] Determine the total contact area between the contact element and the concrete in the finite element analysis model;

[0012] A mid-span pad simulated by discrete elements is set at the mid-span of the finite element analysis model, and boundary pads simulated by discrete elements are set at the left and right boundaries of the finite element analysis model;

[0013] Constrain the degrees of freedom of the boundary pads in all directions, and constrain the degrees of freedom of the mid-span pads in all directions except the vertical direction;

[0014] Apply vertical displacement load to the mid-span pad until the bond-slip effect of the contact element fails;

[0015] After the contact unit reaches the preset damage standard, the damage judgment standard value is calculated according to the damage area of ​​the contact unit and the total contact area;

[0016] The instability of the tunnel is assessed based on the damage judgment standard value.

[0017] When implementing this embodiment, firstly, the material parameters of the tunnel support structure are fully tested for mechanical properties, including the compressive strength, tensile strength, shear strength, Poisson's ratio and elastic modulus of concrete, steel mesh and steel arch. Through the test data, the bond-slip characteristics between concrete and steel mesh, concrete and steel arch are determined, and the bond-slip constitutive structure is further established through the bond-slip relationship of each material; when establishing the finite element analysis model, it is necessary to determine the geometric shape, relative position and connection method of each component in the tunnel support structure to ensure that the finite element model can accurately reflect the actual engineering structure and take into account the influence of the bond-slip effect in the structure. At the same time, the influence of nonlinear factors such as material nonlinearity, geometric nonlinearity and contact nonlinearity needs to be considered in the simulation analysis to more realistically simulate the stress and deformation characteristics of the structure under the actual load.

[0018] In the implementation of this embodiment, the bond-slip behavior in the tunnel support structure is simulated by inserting the contact unit as a bond-slip layer between the concrete and the steel mesh, and between the concrete and the steel arch frame; the contact behavior between the concrete and other support structure components is simulated by determining the total contact area of ​​the contact unit and setting appropriate contact boundary conditions; in addition, by simulating the bond-slip situation during loading, the deformation, damage and stability of the finite element analysis model under load are evaluated, providing an important basis for determining the stability of the tunnel support structure.

[0019] In a possible implementation, the degrees of freedom of the bounding pad in all directions are constrained to include:

[0020] The normal direction of the contact surface between the boundary pad and the finite element analysis model is set to hard contact, and the tangential direction is set to rough friction contact to constrain the freedom of the boundary pad in all directions.

[0021] The advantage of this solution is that the normal direction of the contact surface between the boundary pad and the finite element analysis model is set to hard contact, which means that in the absence of elastic deformation, there is no relative displacement between the left and right boundaries of the finite element model and the boundary pad. The tangential direction is set to rough friction contact, which takes into account the friction effect between the surfaces. It can more realistically simulate the contact behavior under actual boundary conditions, help to accurately reflect the interaction between the boundary pad and the model, and improve the accuracy and reliability of the simulation results.

[0022] In a possible implementation, the degrees of freedom of the mid-span pad in all directions except the vertical direction are constrained, including:

[0023] The normal direction of the contact surface between the mid-span pad and the finite element analysis model is set to hard contact, and the tangential direction is set to rough friction contact, constraining the freedom of the mid-span pad in all directions except the vertical direction.

[0024] In the implementation of this embodiment, by constraining the degrees of freedom of the mid-span pad in directions other than the vertical direction, its movement in the horizontal plane can be effectively restricted, the stability of the support model can be maintained, and preparation can be made for the subsequent simulation of applying a vertical downward displacement load to the mid-span pad.

[0025] In a possible implementation, the contact unit is a COH3D8 unit.

[0026] The advantage of this solution is that the COH3D8 unit is a unit with bond-slip contact capability. By using this unit, the bonding, sliding and fracture between different components can be simulated more accurately and effectively.

[0027] In a possible implementation, the step of applying a load along a vertical displacement to the mid-span pad until the bond-slip failure of the contact unit includes:

[0028] Apply a load in the vertical direction to the mid-span pad;

[0029] Set the maximum tensile damage judgment data value as the first judgment data, and set the damage expansion failure variable value as the second judgment data;

[0030] Determine the critical condition of the initial damage of the contact unit through the first judgment data;

[0031] Monitoring the change of the damage state of the contact unit over time through the second judgment data;

[0032] When the second judgment data is 1, the stick-slip effect of the contact unit fails.

[0033] When this embodiment is implemented, in the process of applying a vertical downward displacement load to the mid-span pad, the first judgment data is used as a basis for judging that the tensile stress on the contact unit increases from 0 to the bond-slip characteristic value stage, and the value of the second judgment data is always kept at 0 in this stage; after the tensile stress of the contact unit exceeds the preset limit stress value, the value of the second judgment data gradually increases linearly from 0 to 1. At this time, the cohesive stress of the contact unit is reduced to 0, and the contact unit cannot continue to participate in the bond-slip effect between the steel mesh, steel section and concrete due to failure.

[0034] The advantage of this solution is that by setting the first judgment data and the second judgment data, the critical conditions for the initial damage of the contact unit can be accurately determined, and the damage and destructive state of the contact unit can be monitored, which helps to more accurately simulate the process of damage evolution of the contact unit in the process of bearing load until the failure of the bonding slip effect.

[0035] In a possible implementation, determining the critical condition for initial damage of the contact unit through the first judgment data includes:

[0036] When the load is greater than 0 and less than or equal to the first judgment data, the tensile stress of the contact unit continues to increase and is in a tensile loading stage where no tensile damage occurs;

[0037] When the load is greater than the first judgment data, the contact unit enters the initial stage of stretching and damage and triggers the switch to wake up the second judgment data.

[0038] When this embodiment is implemented, when the load exceeds the first judgment data, the contact unit is triggered to enter the initial stage of tensile damage, and the subsequent monitoring of the damage expansion and destruction state is started.

[0039] The advantage of this solution is that the critical conditions for the initial damage of the contact unit can be determined through the first judgment data, so that the damage threshold of the contact unit can be accurately predicted and the initial stage of damage can be discovered in time, providing an effective method and guarantee for the performance evaluation and design of engineering structures.

[0040] In a possible implementation, monitoring the change of the damage state of the contact unit over time through the second judgment data includes:

[0041] When the second judgment data is equal to 0, the contact unit enters the initial stage of stretch damage with a stretch damage state of zero;

[0042] When the second judgment data is greater than 0 and less than 1, the contact unit is partially stretched and damaged;

[0043] When the second judgment data is equal to 1, the contact unit enters a full tensile damage state with a tensile damage state of 1, and at this time, the bonding slip effect of the contact unit fails and cannot continue to withstand stress.

[0044] The advantage of this solution is that the second judgment data monitoring can track the damage status of the contact unit in real time and provide detailed monitoring of the damage and destruction process of the contact unit. In this way, the damage of the contact unit can be discovered in time during the simulation process, providing engineers with important information on structural stability and safety.

[0045] In a possible implementation, the damage determination standard value is obtained by dividing the damage area of ​​the contact unit by the total contact area.

[0046] When this embodiment is implemented, the damaged area of ​​the contact unit is divided by the total contact area to reflect the proportion of the damaged part of the contact unit in the structure to the total contact area. When the damage judgment standard value exceeds a certain threshold, it indicates that the bonding and slip layer represented by the contact unit has been severely damaged, which may cause the support structure to become unstable.

[0047] The advantage of this scheme is that the damage judgment standard value can help evaluate the damage distribution and severity of the structure when it is subjected to external loads, and provide a quantitative indicator for determining whether the structure is unstable. BRIEF DESCRIPTION OF THE DRAWINGS

[0048] The drawings described herein are used to provide a further understanding of the embodiments of the present invention, constitute a part of this application, and do not constitute a limitation of the embodiments of the present invention. In the drawings:

[0049] Figure 1 is a flow chart of the method steps of the present invention;

[0050] Figure 2 It is a schematic diagram of a model of the present invention;

[0051] Figure 3 It is a schematic diagram of the relative positions of the steel mesh, steel arch frame and concrete inside the model of the present invention. DETAILED DESCRIPTION

[0052] In order to make the objectives, technical solutions and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with embodiments and drawings. The exemplary implementation modes of the present invention and their description are only used to explain the present invention and are not intended to limit the present invention.

[0053] Please refer to Figures 1 to 3 , a numerical simulation method for a tunnel support structure considering bond slip, the method comprising the following steps:

[0054] Determine the material parameters of concrete, steel mesh and steel arch in the tunnel support structure through mechanical property tests;

[0055] The bond-slip constitutive model is selected based on the bond-slip relationship between concrete and steel mesh, and the bond-slip relationship between concrete and steel arch frame;

[0056] A finite element analysis model including a reinforced concrete beam is constructed according to the tunnel support structure, wherein the relative distribution positions of the reinforced concrete beam and the concrete, the steel mesh and the steel arch frame in the tunnel support structure are consistent.

[0057] Assigning a plastic damage model to the finite element analysis model;

[0058] Inserting contact elements as bond-slip layers between concrete and steel mesh in the finite element analysis model, and inserting the contact elements between concrete and steel arches in the finite element analysis model;

[0059] determining a total contact area between the contact element and the concrete in the finite element analysis model;

[0060] A mid-span pad simulated by discrete elements is set at the mid-span of the finite element analysis model, and boundary pads simulated by discrete elements are set at the left and right boundaries of the finite element analysis model;

[0061] Constrain the degrees of freedom of the boundary pad in all directions, and constrain the degrees of freedom of the mid-span pad in all directions except the vertical direction;

[0062] Applying a vertical displacement load to the mid-span pad until the bond-slip effect of the contact unit fails;

[0063] After the contact unit reaches a preset damage standard, a damage determination standard value is calculated according to the damage area of ​​the contact unit and the total contact area;

[0064] Whether the tunnel is unstable is evaluated according to the damage judgment standard value.

[0065] When implementing this embodiment, firstly, the material parameters of the tunnel support structure are fully tested for mechanical properties, including the compressive strength, tensile strength, shear strength, Poisson's ratio and elastic modulus of concrete, steel mesh and steel arch frame; through the test data, the bond-slip characteristics between concrete and steel mesh, concrete and steel arch frame are determined, and the bond-slip constitutive structure is further established through the bond-slip relationship of each material; when establishing the finite element analysis model, the geometric shape, relative position and connection method of each component in the tunnel support structure need to be determined to ensure that the finite element model can accurately reflect the actual engineering structure and take into account the influence of the bond-slip effect in the structure. At the same time, the influence of nonlinear factors such as material nonlinearity, geometric nonlinearity and contact nonlinearity need to be considered in the simulation analysis to more realistically simulate the stress and deformation characteristics of the structure under the actual load.

[0066] In the implementation of this embodiment, the bond-slip behavior in the tunnel support structure is simulated by inserting the contact unit as a bond-slip layer between concrete and steel mesh, and between concrete and steel arch frame; the contact behavior between concrete and other support structure components is simulated by determining the total contact area of ​​the contact unit and setting appropriate contact boundary conditions; in addition, by simulating the bond-slip situation during loading, the deformation, damage and stability of the finite element analysis model under load are evaluated, which provides an important basis for determining the stability of the tunnel support structure.

[0067] Furthermore, the degrees of freedom constraining the boundary pad in all directions include:

[0068] The contact surface between the boundary pad and the finite element analysis model is set to hard contact in the normal direction and rough friction contact in the tangential direction, thereby constraining the freedom of the boundary pad in all directions.

[0069] The advantage of this solution is that the normal direction of the contact surface between the boundary pad and the finite element analysis model is set to hard contact, which means that in the absence of elastic deformation, there is no relative displacement between the left and right boundaries of the finite element analysis model and the boundary pad. The tangential direction is set to rough friction contact, which takes into account the friction effect between the surfaces and can more realistically simulate the contact behavior under actual boundary conditions, which helps to accurately reflect the interaction between the boundary pad and the finite element analysis model and improves the accuracy and reliability of the simulation results.

[0070] Furthermore, the degrees of freedom constraining the mid-span pad in all directions except the vertical direction include:

[0071] The contact surface between the mid-span pad and the finite element analysis model is set to hard contact in the normal direction and rough friction contact in the tangential direction, thereby constraining the freedom of the mid-span pad in all directions except the vertical direction.

[0072] In the implementation of this embodiment, by constraining the degrees of freedom of the mid-span pad in directions other than the vertical direction, its movement in the horizontal plane can be effectively restricted, the stability of the support model can be maintained, and preparation can be made for the subsequent simulation of applying a vertical downward displacement load to the mid-span pad.

[0073] Furthermore, the contact unit is a COH3D8 unit.

[0074] The advantage of this solution is that the COH3D8 unit is a unit with bonding-slip contact capability. By using this unit, the bonding, sliding and fracture between different components can be simulated more accurately and effectively.

[0075] Furthermore, the step of applying a load along a vertical displacement to the mid-span pad until the bonding and slip failure of the contact unit comprises:

[0076] Applying a load in the vertical direction to the mid-span pad;

[0077] Set the maximum tensile damage judgment data value as the first judgment data, and set the damage expansion failure variable value as the second judgment data;

[0078] Determining a critical condition for initial damage of the contact unit by using the first judgment data;

[0079] Monitoring the change of the damage state of the contact unit over time through the second judgment data;

[0080] When the second judgment data is 1, the stick-slip effect of the contact unit fails.

[0081] When this embodiment is implemented, during the process of applying a vertical downward displacement load to the mid-span pad, the first judgment data is used as a basis for judging that the tensile stress on the contact unit increases from 0 to the bond-slip characteristic value stage, and the value of the second judgment data always remains at 0 during this stage; after the tensile stress of the contact unit exceeds the preset limit stress value, the value of the second judgment data gradually increases linearly from 0 to 1, at which time the cohesive stress of the contact unit is reduced to 0, and the contact unit cannot continue to participate in the bond-slip effect between the steel mesh, steel section and concrete due to failure.

[0082] The advantage of this solution is that by setting the first judgment data and the second judgment data, the critical conditions for the initial damage of the contact unit can be accurately determined, and the damage and destructive state of the contact unit can be monitored, which helps to more accurately simulate the process of damage evolution of the contact unit in the process of bearing load until the failure of the bonding slip effect.

[0083] Furthermore, determining the critical condition of the initial damage of the contact unit through the first judgment data includes:

[0084] When the load is greater than 0 and less than or equal to the first judgment data, the tensile stress of the contact unit continues to increase and is in a tensile loading stage where no tensile damage occurs;

[0085] When the load is greater than the first judgment data, the contact unit enters the initial stage of stretching and damage and triggers the switch to wake up the second judgment data.

[0086] When this embodiment is implemented, when the load exceeds the first judgment data, the contact unit is triggered to enter the initial stage of tensile damage, and the subsequent monitoring of the damage expansion and destruction state is started.

[0087] The advantage of this solution is that the critical conditions for the initial damage of the contact unit can be determined through the first judgment data, so that the damage threshold of the contact unit can be accurately predicted and the initial stage of damage can be discovered in time, providing an effective method and guarantee for the performance evaluation and design of engineering structures.

[0088] Further, monitoring the change of the damage state of the contact unit over time through the second judgment data includes:

[0089] When the second judgment data is equal to 0, the contact unit enters the initial stage of stretch damage with a stretch damage state of zero;

[0090] When the second judgment data is greater than 0 and less than 1, the contact unit is partially stretched and damaged;

[0091] When the second judgment data is equal to 1, the contact unit enters into a full-stretch damage state of 1, and at this time, the bonding slip effect of the contact unit fails and cannot continue to bear stress.

[0092] The advantage of this solution is that the second judgment data monitoring can track the damage status of the contact unit in real time, and provide detailed monitoring of the damage and destruction process of the contact unit. In this way, the damage of the contact unit can be discovered in time during the simulation process, providing engineers with important information about structural stability and safety.

[0093] Furthermore, the damage judgment standard value is obtained by dividing the damage area of ​​the contact unit by the total contact area.

[0094] When this embodiment is implemented, the damaged area of ​​the contact unit is divided by the total contact area to reflect the proportion of the damaged part of the contact unit in the structure to the total contact area. When the damage judgment standard value exceeds a certain threshold, it indicates that the bonding and slip layer represented by the contact unit has been severely damaged, which may cause the support structure to become unstable.

[0095] The advantage of this solution is that the damage judgment standard value can help evaluate the damage distribution and severity of the structure when it is subjected to external loads, and provide a quantitative indicator for determining whether the structure is unstable.

[0096] The specific implementation methods described above further illustrate the objectives, technical solutions and beneficial effects of the present invention in detail. It should be understood that the above description is only a specific implementation method of the present invention and is not intended to limit the scope of protection of the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. A numerical simulation method for tunnel support structure considering bond slip, characterized in that: The method comprises the following steps: Determine the material parameters of concrete, steel mesh and steel arch in the tunnel support structure through mechanical property tests; The bond-slip constitutive model is selected based on the bond-slip relationship between concrete and steel mesh, and the bond-slip relationship between concrete and steel arch frame; Constructing a finite element analysis model including a reinforced concrete beam according to the tunnel support structure, wherein the reinforced concrete beam has the same relative distribution position as the concrete, the steel mesh and the steel arch frame in the tunnel support structure; Assigning a plastic damage model to the finite element analysis model; Inserting contact elements as bond-slip layers between concrete and steel mesh in the finite element analysis model, and inserting contact elements between concrete and steel arch frames in the finite element analysis model; determining a total contact area between the contact element and the concrete in the finite element analysis model; A mid-span pad simulated by discrete elements is set at the mid-span of the finite element analysis model, and boundary pads simulated by discrete elements are set at the left and right boundaries of the finite element analysis model; Constrain the degrees of freedom of the boundary pad in all directions, and constrain the degrees of freedom of the mid-span pad in all directions except the vertical direction; Applying a vertical displacement load to the mid-span pad until the bond-slip effect of the contact unit fails; After the contact unit reaches a preset damage standard, a damage determination standard value is calculated according to the damage area of ​​the contact unit and the total contact area; Whether the tunnel is unstable is evaluated according to the damage judgment standard value.

2. A method for numerical simulation of tunnel support structure considering bond slip according to claim 1, characterized in that: The degrees of freedom constraining the boundary pad in all directions include: The contact surface between the boundary pad and the finite element analysis model is set to hard contact in the normal direction and rough friction contact in the tangential direction, thereby constraining the freedom of the boundary pad in all directions.

3. A method for numerical simulation of tunnel support structure considering bond slip according to claim 1, characterized in that: The degrees of freedom constraining the mid-span pad in all directions except the vertical direction include: The contact surface between the mid-span pad and the finite element analysis model is set to hard contact in the normal direction and rough friction contact in the tangential direction, thereby constraining the freedom of the mid-span pad in all directions except the vertical direction.

4. A method for numerical simulation of tunnel support structure considering bond slip according to claim 1, characterized in that: The contact unit is a COH3D8 unit.

5. The method for numerical simulation of tunnel support structure considering bond slip according to claim 1, characterized in that: The step of applying a load along a vertical displacement to the mid-span pad until the bonding and slip failure of the contact unit comprises: Applying a load in the vertical direction to the mid-span pad; Set the maximum tensile damage judgment data value as the first judgment data, and set the damage expansion failure variable value as the second judgment data; Determine the critical condition of the initial damage of the contact unit by using the first judgment data; Monitoring the change of the damage state of the contact unit over time through the second judgment data; When the second judgment data is 1, the stick-slip effect of the contact unit fails.

6. A method for numerical simulation of tunnel support structure considering bond slip according to claim 5, characterized in that: The critical condition for the initial damage of the contact unit determined by the first judgment data includes: When the load is greater than 0 and less than or equal to the first judgment data, the tensile stress of the contact unit continues to increase and is in a tensile loading stage where no tensile damage occurs; When the load is greater than the first judgment data, the contact unit enters the initial stage of stretching and damage and triggers the switch to wake up the second judgment data.

7. A method for numerical simulation of tunnel support structure considering bond slip according to claim 5, characterized in that: Monitoring the change of the damage state of the contact unit over time through the second judgment data includes: When the second judgment data is equal to 0, the contact unit enters the initial stage of stretch damage with a stretch damage state of zero; When the second judgment data is greater than 0 and less than 1, the contact unit is partially stretched and damaged; When the second judgment data is equal to 1, the contact unit enters a full stretch damage state with a stretch damage state of 1, and at this time, the bonding slip effect of the contact unit fails and cannot continue to withstand stress.

8. The method for numerical simulation of tunnel support structure considering bond slip according to claim 1, characterized in that: The damage judgment standard value is obtained by dividing the damage area of ​​the contact unit by the total contact area.

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