Tunnel face support pressure calculation method and device based on dichotomy

Abstract

The present invention provides a method and device for calculating the support pressure of a tunnel face based on the dichotomy method, which can quickly and accurately obtain the support pressure of the tunnel face. The support pressure calculation method includes: Step 1. Judging the critical stable state based on the maximum unbalanced force ratio ε; changing the strength reduction calculation to not calculate the specific safety factor, but only calculate ε. When ε does not exceed the threshold value ε0, it is in a stable state; Step 2. Automatically iteratively searching for the upper and lower limits of the support pressure; for each iterative search process: apply the support pressure value of the current iterative step to the model tunnel face and perform the strength reduction calculation after the change in Step 1 to obtain the maximum unbalanced force ratio ε. When ε ≤ ε0, halve the support pressure of the next iterative step; otherwise, double the support pressure of the next iterative step; repeat the above process until the state indices of two adjacent iterative steps meet the requirements; Step 3. Iteratively converging the support pressure based on the dichotomy method to obtain the target value of the support pressure.

Description

Technical Field

[0001] The invention belongs to the technical field of tunnel engineering design, and in particular relates to a method and a device for calculating tunnel face support pressure based on a dichotomy method. Background Art

[0002] For earth tunnels or broken rock tunnels, stress release during construction may cause face collapse, affecting tunnel construction safety. In order to ensure the stability of the tunnel face during construction, a certain support pressure can be applied to the face to limit the deformation of the rock and soil on the tunnel face toward the free surface. Determining the size of the support pressure is a very important issue in the tunnel design stage. According to the design requirements, the support pressure can be the minimum support pressure or the support pressure that meets a target safety factor. During the construction stage, it is applied in the form of shield jacking equipment or face anchors to ensure tunnel construction safety.

[0003] Since the failure mechanism of the tunnel face is relatively complex, the theoretical method needs to take certain assumptions and its accuracy is questionable. Therefore, numerical calculation software is often used in actual engineering to analyze the stability of the tunnel face. On this basis, the support pressure of the tunnel face can be adjusted and the minimum support pressure of the tunnel face can be approached through continuous trial calculations.

[0004] However, the shortcomings of existing methods include:

[0005] 1) The convergence criteria are unclear and it is difficult to judge the stability;

[0006] 2) It is necessary to calculate in advance to determine the upper and lower limits of support pressure adjustment;

[0007] 3) There is no method for determining the support pressure design based on the target safety factor;

[0008] 4) The adjustment of support pressure and the numerical calculation process need to be adjusted manually, and the calculation process is cumbersome and takes a long time. Summary of the invention

[0009] The present invention is made to solve the above-mentioned problem, and aims to provide a fast and simple method and device for calculating tunnel face support pressure, which can quickly and accurately obtain the tunnel face support pressure.

[0010] In order to achieve the above purpose, the present invention adopts the following scheme:

[0011] <Method>

[0012] like Figure 1 As shown, the present invention provides a method for calculating tunnel face support pressure based on dichotomy, which is characterized by comprising the following steps:

[0013] Step 1. Determine the critical stability state based on the maximum unbalanced force ratio ∈;

[0014] According to the size of the tunnel to be calculated and the engineering requirements, the model is constructed, and the strength reduction calculation of the model is changed to not calculate the specific safety factor, but only calculate the maximum unbalanced force ratio ∈: the upper and lower limits are calculated and All are set to the target safety factor F s * , test tunnel at target safety factor F s * The stable state at this time is the maximum unbalanced force ratio ∈; correspondingly, the critical stable state judgment method is: when ∈ does not exceed the critical threshold ∈ 0 , it indicates that the calculation has converged and the tunnel face is in a stable state; otherwise, the calculation has not converged and the tunnel face is in an unstable state.

[0015] FLAC 3D The software comes with a strength reduction method, which can be used to analyze the stability of the tunnel face. The safety factor is defined as: In the formula, c and are the cohesion and internal friction angle of the sample input, c cr and They represent the critical cohesion and critical internal friction angle when the tunnel face is in the limit state respectively; according to the existing method, the strength reduction calculation requires multiple iterative calculations to approximate the strength reduction factor, which takes too long; in order to improve the calculation efficiency, as described above, the present invention only calculates the maximum unbalanced force ratio ∈ through strength reduction, without calculating the specific safety factor, and the method is to execute "solve fos bracket command, and will calculate the upper and lower limits and All are set to the target safety factor F s * , then the command becomes to test the tunnel with a safety factor of F s * The stable state at that time is calculated and ∈ is obtained; then, the stability of the tunnel face is judged by ∈.

[0016] Step 2. Automatic iterative search of upper and lower limits of support pressure (first stage: search stage);

[0017] For each iterative search process: the support pressure value of the current iteration step is The maximum unbalanced force ratio ∈ is obtained by applying the strength reduction calculation after the change in step 1 to the model tunnel face, where n is a positive integer. When ∈≤∈ 0 When the tunnel face state is marked as k n= b, b is a positive number, and the support pressure of the next iteration step is When ∈>∈ 0 When the tunnel face state is marked as k n = -b, and let the support pressure of the next iteration be Repeat the above iterative process. When the state index k of two adjacent iterative steps is n ·k n-1 =-b 2 When , it means that the upper and lower limits have been searched, and the smaller value of the two support pressures is determined as the lower limit The larger value is determined as the upper limit Go to step 3; for the first iteration of the search phase, k 0 Assign an arbitrary value whose absolute value is not b, the support pressure value Can be assigned any value;

[0018] Step 3. Iterative convergence of support pressure based on dichotomy (second stage: convergence stage);

[0019] After determining the lower limit of the support pressure iteration and upper limit After that, it enters the convergence phase iteration and takes the average value As the support pressure of the current iteration step in the convergence stage, ∈ is calculated using step 1. When ∈≤∈ 0 , let the upper limit of the next iteration be Otherwise, let the lower limit be Repeat the above process until the difference between the upper and lower limits of the support pressure is ≤ the convergence threshold ε, and take the average value of the upper and lower limits of the support pressure as the calculated support pressure target value.

[0020] Preferably, the method for calculating tunnel face support pressure based on dichotomy provided by the present invention may also have the following characteristics: when each numerical calculation is completed, the displacement field and stress field of the model have changed. Therefore, when changing the support pressure, it is necessary to re-import the numerical model before excavation, perform excavation and support again, and perform calculations. However, importing the model before excavation will restore the values ​​of all rewritten variables to the state before rewriting, making it impossible to automatically iterate. In order to solve this problem, the present invention realizes automatic iteration. In step 2, for the storage and reading and writing of iterative data: when each iterative step is calculated, the variables whose values ​​have changed are updated (for example, in the first stage, the support pressure is a variable; in the second stage, the support pressure and its upper and lower limits and All are variables), write the updated variable values ​​into a text file as a variable update file and import it into the original model, set the model to read the values ​​in the variable update file and assign them to the corresponding variables as the current values ​​of each variable in the next iteration step.

[0021] Preferably, the tunnel face support pressure calculation method based on the dichotomy method provided by the present invention may also have the following characteristics: determining whether a set of upper and lower limits have been found in step 2 by using the iterative stage index α, thereby entering step 3 to perform the iteration in the convergence stage: the iterative stage index is initially assigned a value of α = c, and during the iterative calculation process, when k n ·k n-1 =-b 2 When α=d, c and d are unequal numbers. When α=d, it means that a set of upper and lower limits have been found and we should go to step 3 to iterate in the convergence phase.

[0022] Preferably, the method for calculating tunnel face support pressure based on dichotomy provided by the present invention may also have the following characteristics: in step 2, for the first iterative search process, the upper and lower limits of the support pressure are assigned as follows:

[0023] Preferably, the tunnel face support pressure calculation method based on dichotomy provided by the present invention may also have the following characteristics: critical threshold ∈ 0 =1×10 -5 ; The convergence threshold ε corresponds to the difference between the upper and lower limits of the allowable support pressure and can be set according to project requirements. For example, setting ε = 0.2 kPa means that the convergence tolerance range is ± 0.1 kPa.

[0024] <Device>

[0025] Furthermore, the present invention also provides a device for determining tunnel face support pressure based on dichotomy, which is characterized by comprising:

[0026] Model component department, constructs tunnel model according to the size of the tunnel to be calculated and engineering requirements;

[0027] The critical stability state judgment unit makes a critical stability state judgment based on the maximum unbalanced force ratio ∈; builds a model according to the size of the tunnel to be calculated and the engineering requirements, and changes the strength reduction calculation of the model to not calculate the specific safety factor, but only calculate the maximum unbalanced force ratio ∈: the upper and lower limits of the calculation and All are set to the target safety factor F s * , test tunnel at target safety factor F s *The stable state at this time is the maximum unbalanced force ratio ∈; correspondingly, the critical stable state judgment method is: when ∈ does not exceed the critical threshold ∈ 0 When , it means that the calculation converges and the tunnel face is in a stable state; otherwise, the calculation does not converge and the tunnel face is in an unstable state;

[0028] The search part automatically iterates and searches for the upper and lower limits of the support pressure. For each iterative search process: the support pressure value of the current iteration step is The maximum unbalanced force ratio ∈ is calculated by the critical stability judgment part on the original model tunnel face, n is a positive integer, when ∈≤∈ 0 When the tunnel face state is marked as k n = b, b is a positive number, and the support pressure of the next iteration step is When ∈>∈ 0 When the tunnel face state is marked as k n = -b, and let the support pressure of the next iteration be Repeat the above iterative process. When the state index k of two adjacent iterative steps is n ·k n-1 =-b 2 When , it means that the upper and lower limits have been searched, and the smaller value of the two support pressures is determined as the lower limit The larger value is determined as the upper limit End the search; for the first iteration of the search phase, k 0 Assign an arbitrary value whose absolute value is not b, the support pressure value Can be assigned any value;

[0029] Target value determination part, support pressure iteration convergence based on dichotomy: After determining the lower limit of support pressure iteration and upper limit After that, it enters the convergence stage and takes the average value As the support pressure of the current iteration step in the convergence stage, the corresponding ∈ is calculated using the model component part. When ∈≤∈ 0 , let the upper limit of the next iteration be Otherwise, let the lower limit be Repeat the above process until the difference between the upper and lower limits of the support pressure is less than or equal to the convergence threshold ε, and take the average value of the upper and lower limits of the support pressure as the calculated support pressure target value;

[0030] The control unit is connected to the model component unit, the critical stable state judgment unit, the search unit and the target value determination unit to control their operations.

[0031] Preferably, the device for determining tunnel face support pressure based on dichotomy provided by the present invention may further include: an input display unit, which is communicatively connected to the control unit and is used to allow the user to input operation instructions and perform corresponding display.

[0032] Preferably, the device for determining the tunnel face support pressure based on the dichotomy method provided by the present invention may also have the following characteristics: the input display unit can display prompt information to instruct the user to input the size and engineering requirement information of the tunnel and to input the initial values ​​of the corresponding parameters, and can also display the tunnel model constructed by the model component unit, display the judgment criteria and judgment results of the critical stability state judgment unit, display the search situation of the search unit in a graphical form, display the iterative process and final results of the target value determination unit in a graphical form, and can mark and display the data at the corresponding position of the model diagram.

[0033] Preferably, the tunnel face support pressure determination device based on dichotomy provided by the present invention may also have the following characteristics: in the search section, for the storage and reading and writing of iterative data: when each iterative step is calculated, the variables whose values ​​have changed are updated, the updated variable values ​​are written into a text file and imported into the original model as a variable update file, and the model is set to read the values ​​in the variable update file and assign values ​​to the corresponding variables as the current values ​​of each variable when calculating the next iterative step.

[0034] Preferably, the tunnel face support pressure determination device based on the dichotomy method provided by the present invention may also have the following characteristics: the control unit searches for a set of upper and lower limits through the iterative phase index α to determine whether the unit has found the set of upper and lower limits, thereby entering the target value determination unit to perform the iteration in the convergence phase: the initial value of the iterative phase index is α = c, and during the iterative calculation process, when k n ·k n-1 =-b 2 When α=d, c and d are unequal numbers. When α=d, it means that a set of upper and lower bounds have been found and the iteration should enter the convergence stage.

[0035] Functions and Effects of the Invention

[0036] 1) The present invention does not need to calculate a specific safety factor, but uses the maximum unbalanced force ratio ∈ to automatically determine whether it has converged. This can not only effectively reduce the amount of calculation processing and effectively improve the calculation efficiency, but also obtain more accurate calculation results.

[0037] 2) The present invention can automatically determine the upper and lower limits of the support pressure, thus simplifying the analysis steps.

[0038] 3) The iteration time of the present invention is greatly shortened, and the iteration process that originally required dozens of hours can be shortened to about 1 hour. BRIEF DESCRIPTION OF THE DRAWINGS

[0039] Figure 1 It is a flow chart of a method for calculating tunnel face support pressure based on dichotomy method involved in the present invention;

[0040] Figure 2 A schematic diagram of a numerical analysis model involved in an embodiment of the present invention;

[0041] Figure 3 Schematic diagram of the support pressure and upper and lower limit iteration process involved in the first embodiment of the present invention Figure 1

[0042] Figure 4 Schematic diagram of the support pressure and upper and lower limit iteration process involved in the first embodiment of the present invention Figure 2

[0043] Figure 5 Schematic diagram of the iterative process of the support pressure and upper and lower limits involved in the second embodiment of the present invention Figure 1

[0044] Figure 6 Schematic diagram of the iterative process of the support pressure and upper and lower limits involved in the second embodiment of the present invention Figure 1 DETAILED DESCRIPTION

[0045] The following is a detailed description of the specific implementation scheme of the tunnel face support pressure calculation method and device based on the dichotomy method of the present invention in conjunction with the accompanying drawings. In the following examples, the analysis software involved is FLAC 3D The steps and methods involved are conventional methods unless otherwise specified.

[0046] <Example 1>

[0047] In the first embodiment, the model is constructed according to the size of the tunnel to be calculated and the engineering requirements: a circular tunnel with a diameter of D = 10m and a burial depth of C = 10m is selected; FLAC is used 3D The software builds numerical analysis models, such as Figure 2 As shown in the figure, due to the symmetry of the tunnel structure, only half of the numerical model is established; considering the boundary effect of 3 to 5 times, the length, width and height of the model are set to 7 times, 4 times and 5 times the diameter respectively. The side of the model is constrained in the normal direction, and the bottom of the model is constrained in the x, y and z directions. The soil is simulated using the Mohr-Coulomb model, with parameters of cohesion of 7 kPa, internal friction angle of 17°, and gravity of 18 kN / m 3, elastic modulus is 25MPa, Poisson's ratio is 0.3. The lining is simulated by elastic model, with a weight of 25kN / m 3 , the elastic modulus is 10.9×10 3 MPa.

[0048] The tunnel face support pressure calculation method based on the dichotomy method of the present invention is used to determine the support pressure that meets the safety requirements, which specifically includes the following steps:

[0049] 1) Initialize the relevant parameters, set the iteration stage index α = 1, the convergence tolerance ε = 0.2 kPa, and the initial value of the support pressure Initial value of upper and lower limits According to the project requirements, the target safety factor F s * =1.3, initial stable state index k 0 =0;

[0050] 2) Import the numerical model grid, set material parameters, initialize the ground stress, and read variable data from the text file;

[0051] 3) The support pressure σ T n = 100 kPa is evenly applied to the tunnel face for strength reduction calculation, and the maximum unbalanced force ratio ∈ is read;

[0052] 4) Determine the difference between the upper and lower limits If the iteration termination condition is not met, continue iterating;

[0053] 5) Stage index α = 1, continue the first stage iteration;

[0054] 6) Maximum unbalanced force ratio∈<1×10 -5 , the tunnel face status index is k 1 =1, the support pressure in the next iteration is changed to

[0055] 7) k 1 ·k 0 =0≠-1, continue iteration; delete the numerical model after iteration, write the variable data into a text file, re-import the original numerical model, and As the support pressure, the strength reduction calculation is carried out and the unbalanced force ratio ∈ <1×10 -5 , then k 2 =1, k 2 ·k 1 =1≠-1 is not true, continue to iterate; delete the numerical model after iteration, write the variable data into a text file, re-import the original numerical model, and As the support pressure, the strength reduction calculation is carried out and the unbalanced force ratio ∈>1×10 -5 , then k 3 =-1, k 3 ·k 2 =-1 holds true, let α = 2, and enter the second iteration stage;

[0056] 8) Since α = 2, the lower limit is Upper limit is make

[0057] 9) Repeat steps 2) to 4);

[0058] 10) Maximum unbalanced force ratio∈>1×10 -5 , change the lower limit to The upper limit remains unchanged;

[0059] 11) The support pressure in the next iteration is changed to

[0060] 12) Repeat steps 9) to 11) until the convergence condition is met. When the 11th iteration step is reached, the convergence condition is met and the target support pressure is determined to be The iterative data of the whole process are shown in Table 1. The iterative process of support pressure and upper and lower limits is shown in Figure 3 shown.

[0061] Table 1 Iteration data

[0062]

[0063]

[0064] Set the initial value of support pressure to Other parameters remain unchanged, repeat the above iteration steps, and the iteration steps for support pressure and upper and lower limits are as follows: Figure 4 As shown, the final iterative pressure is The calculation results of the two iterations are consistent, which verifies the accuracy of this method and also shows that the calculation results of this method are not affected by the initial iteration pressure value.

[0065] <Example 2>

[0066] In the second embodiment, the safety factor target value is changed to F s * =1.0, other conditions are the same as those in Example 1, and the support pressure solved is the minimum support pressure. The initial support pressures are set as and Run the iterative program to obtain the iterative results of support pressure and upper and lower limits as follows: Figure 5 and6 shown.

[0067] In both cases, the minimum support pressure is determined after 11 iterations, which are: and The slight difference between the two is due to the rounding of different upper and lower limits during the iteration process, which can be ignored compared with the size of the support pressure, further confirming the reliability and accuracy of this method.

[0068] <Example 3>

[0069] The third embodiment of the present invention provides a device for determining the tunnel face support pressure that can automatically implement the above-mentioned method of the present invention. The device includes a sample size determination unit, a sampling unit, a foundation width critical value calculation unit, a sorting unit, a sequence number determination unit, a foundation width design value determination unit, an input display unit, and a control unit.

[0070] The model component part constructs a tunnel model according to the size of the tunnel to be calculated and the engineering requirements.

[0071] The critical stability state judgment unit makes a critical stability state judgment based on the maximum unbalanced force ratio ∈; constructs a model according to the size of the tunnel to be calculated and the engineering requirements, and changes the strength reduction calculation of the model to not calculate the specific safety factor, but only calculate the maximum unbalanced force ratio ∈: the upper and lower limits of the calculation and All are set to the target safety factor F s * , test tunnel at target safety factor F s * The stable state at this time is the maximum unbalanced force ratio ∈; correspondingly, the critical stable state judgment method is: when ∈ does not exceed the critical threshold ∈ 0 , it indicates that the calculation has converged and the tunnel face is in a stable state; otherwise, the calculation has not converged and the tunnel face is in an unstable state.

[0072] The search unit automatically iterates and searches for the upper and lower limits of the support pressure. For each iterative search process: the support pressure value of the current iteration step is The maximum unbalanced force ratio ∈ is calculated by the critical stability judgment part on the original model tunnel face, n is a positive integer, when ∈≤∈ 0 When the tunnel face state is marked as k n = b, b is a positive number, and the support pressure of the next iteration step is When ∈>∈ 0 When the tunnel face state is marked as k n = -b, and let the support pressure of the next iteration be Repeat the above iterative process. When the state index k of two adjacent iterative steps is n ·kn-1 =-b 2 When , it means that the upper and lower limits have been searched, and the smaller value of the two support pressures is determined as the lower limit The larger value is determined as the upper limit End the search; for the first iteration of the search phase, k 0 Assign an arbitrary value whose absolute value is not b, the support pressure value Can be assigned any value.

[0073] In the search section, for the storage and reading and writing of iterative data: when each iterative step is completed, update the variables whose values ​​have changed, write the updated variable values ​​into a text file and import it into the original model as a variable update file, set the model to read the values ​​in the variable update file and assign them to the corresponding variables as the current values ​​of each variable when calculating the next iterative step.

[0074] The target value determination part is based on the dichotomy method to iterate the support pressure convergence: after determining the lower limit of the support pressure iteration and upper limit Then, take the average As the support pressure of the current iteration step in the second stage, the corresponding ∈ is calculated by the model component part, when ∈≤∈ 0 , let the upper limit of the next iteration be Otherwise, let the lower limit be Repeat the above process until the difference between the upper and lower limits of the support pressure is ≤ the convergence threshold ε, and take the average value of the upper and lower limits of the support pressure as the calculated support pressure target value.

[0075] The input display unit is connected to the control unit for communication, and is used to allow the user to input operation instructions and display accordingly. Specifically, the input display unit can display prompt information to instruct the user to input the size and engineering requirements of the tunnel and input the initial values ​​of the corresponding parameters; the input display unit can also display the tunnel model constructed by the model component unit, the judgment criteria and judgment results of the critical stability state judgment unit, the search situation of the search unit in a graphical form, the iterative process and final results of the target value determination unit in a graphical form, and can mark and display the data at the corresponding position of the model diagram.

[0076] The control unit is connected to the model component unit, the critical stable state judgment unit, the search unit, the target value determination unit and the input display unit to control their operations.

[0077] The above embodiments are merely examples of the technical solutions of the present invention. The method and device for calculating tunnel face support pressure based on dichotomy involved in the present invention are not limited to the contents described in the above embodiments, but are subject to the scope defined by the claims. Any modification, supplement or equivalent replacement made by technicians in the field of the present invention on the basis of this embodiment is within the scope of protection required by the claims of the present invention.

Claims

1. Calculation method of tunnel face support pressure based on dichotomy, It is characterized in that The following steps are involved: Step 1. Determine the critical stability state based on the maximum unbalanced force ratio ∈; According to the size of the tunnel to be calculated and the engineering requirements, the model is constructed, and the strength reduction calculation of the model is changed to not calculate the specific safety factor, but only calculate the maximum unbalanced force ratio ∈: the upper and lower limits are calculated and All are set to the target safety factor F s * , test tunnel at target safety factor F s * The stable state at this time is the maximum unbalanced force ratio ∈; correspondingly, the critical stable state judgment method is: when ∈ does not exceed the critical threshold ∈ 0 When , it means that the calculation converges and the tunnel face is in a stable state; otherwise, the calculation does not converge and the tunnel face is in an unstable state; Step 2. Automatically iterate and search for the upper and lower limits of support pressure; For each iterative search process: the current iteration step support pressure value The maximum unbalanced force ratio ∈ is obtained by applying the strength reduction calculation after the change in step 1 to the model tunnel face, where n is a positive integer. When ∈≤∈ 0 When the tunnel face state is marked as k n = b, b is a positive number, and the support pressure of the next iteration step is When ∈>∈ 0 When the tunnel face state is marked as k n =-b, and let the support pressure of the next iteration be Repeat the above iterative process. When the state index k of two adjacent iterative steps is n ·k n-1 =-b 2 When , it means that the upper and lower limits have been searched, and the smaller value of the two support pressures is determined as the lower limit The larger value is determined as the upper limit Go to step 3; For the first iteration of the search phase, k 0 Assign an arbitrary value whose absolute value is not b, the support pressure value Can be assigned any value; Step 3. Iterative convergence of support pressure based on dichotomy method; After determining the lower limit of the support pressure iteration and upper limit After that, it enters the convergence phase iteration and takes the average value As the support pressure of the current iteration step in the convergence stage, ∈ is calculated using step 1. When ∈≤∈ 0 , let the upper limit of the next iteration be Otherwise, let the lower limit be Repeat the above process until the difference between the upper and lower limits of the support pressure is ≤ the convergence threshold ε, and take the average value of the upper and lower limits of the support pressure as the calculated support pressure target value.

2. The method for calculating tunnel face support pressure based on dichotomy according to claim 1 is characterized in that: in, In step 2, for the storage and reading and writing of iterative data: when each iterative step is completed, update the variables whose values ​​have changed, write the updated variable values ​​into a text file as a variable update file and import it into the original model, set the model to read the values ​​in the variable update file and assign them to the corresponding variables as the current values ​​of each variable when calculating the next iterative step.

3. The method for calculating tunnel face support pressure based on dichotomy according to claim 1 is characterized in that: in, The iteration phase index α is used to determine whether a set of upper and lower limits have been found in step 2, so as to enter step 3 for the iteration of the convergence phase: the iteration phase index is initially assigned α = c. During the iterative calculation process, when k n ·k n-1 =-b 2 When α=d, c and d are unequal numbers. When α=d, it means that a set of upper and lower limits have been found and we should go to step 3 to iterate in the convergence phase.

4. The method for calculating tunnel face support pressure based on dichotomy according to claim 1 is characterized in that: in, In step 2, for the first iteration, the upper and lower limits of the support pressure are assigned as follows:

5. The method for calculating tunnel face support pressure based on dichotomy according to claim 1 is characterized in that: in, Critical threshold ∈ 0 =1×10 -5 ; The convergence threshold ε corresponds to the difference between the upper and lower limits of the allowable support pressure and can be set according to project requirements.

6. Tunnel face support pressure determination device based on dichotomy, It is characterized in that include: Model component department, constructs tunnel model according to the size of the tunnel to be calculated and engineering requirements; A critical stability state judgment unit performs critical stability state judgment based on the maximum unbalanced force ratio ∈; According to the size of the tunnel to be calculated and the engineering requirements, the model is constructed, and the strength reduction calculation of the model is changed to not calculate the specific safety factor, but only calculate the maximum unbalanced force ratio ∈: the upper and lower limits are calculated and All are set to the target safety factor F s * , test tunnel at target safety factor F s * The stable state at this time is the maximum unbalanced force ratio ∈; correspondingly, the critical stable state judgment method is: when ∈ does not exceed the critical threshold ∈ 0 When , it means that the calculation converges and the tunnel face is in a stable state; otherwise, the calculation does not converge and the tunnel face is in an unstable state; The search part automatically iterates and searches for the upper and lower limits of the support pressure. For each iterative search process: the support pressure value of the current iteration step is The maximum unbalanced force ratio ∈ is calculated by the critical stability state judgment unit on the original model tunnel face, where n is a positive integer. When ∈≤∈ 0 When the tunnel face state is marked as k n = b, b is a positive number, and the support pressure of the next iteration step is When ∈>∈ 0 When the tunnel face state is marked as k n =-b, and let the support pressure of the next iteration be Repeat the above iterative process. When the state index k of two adjacent iterative steps is n ·k n-1 =-b 2 When , it means that the upper and lower limits have been searched, and the smaller value of the two support pressures is determined as the lower limit The larger value is determined as the upper limit End the search; for the first iteration of the search phase, k 0 Assign an arbitrary value whose absolute value is not b, the support pressure value Can be assigned any value; Target value determination part, support pressure iteration convergence based on dichotomy: After determining the lower limit of support pressure iteration and upper limit Then, take the average As the support pressure of the current iteration step in the convergence stage, the corresponding ∈ is calculated using the model component part, when ∈≤∈ 0 , let the upper limit of the next iteration be Otherwise, let the lower limit be Repeat the above process until the difference between the upper and lower limits of the support pressure is less than or equal to the convergence threshold ε, and take the average value of the upper and lower limits of the support pressure as the calculated support pressure target value; The control unit is connected to the model component unit, the critical stable state judgment unit, the search unit and the target value determination unit to control their operations.

7. The device for determining tunnel face support pressure based on dichotomy according to claim 6, It is characterized in that Also includes: The input display unit is connected to the control unit for communication and is used to allow the user to input operation instructions and display them accordingly.

8. The device for determining tunnel face support pressure based on dichotomy according to claim 7 is characterized in that: in, The input display unit can display prompt information to instruct the user to input the size and engineering requirement information of the tunnel and input the initial values ​​of the corresponding parameters. It can also display the tunnel model constructed by the model component unit, display the judgment criteria and judgment results of the critical stable state judgment unit, display the search situation of the search unit in a graphical form, display the iterative process and final results of the target value determination unit in a graphical form, and can mark and display the data at the corresponding position of the model diagram.

9. The device for determining tunnel face support pressure based on dichotomy according to claim 6, characterized in that: in, In the search unit, for the storage and reading and writing of iterative data: when each iterative step is calculated, the variables whose values ​​have changed are updated, the updated variable values ​​are written into a text file and imported into the original model as a variable update file, and the model is set to read the values ​​in the variable update file and assign values ​​to the corresponding variables as the current values ​​of each variable when calculating the next iterative step.

10. The device for determining tunnel face support pressure based on dichotomy according to claim 6, characterized in that: in, The control unit determines whether the search unit has found a set of upper and lower limits through the iteration phase index α, thereby entering the target value determination unit to perform the iteration of the convergence phase: the iteration phase index is initially assigned a value of α=c. During the iterative calculation process, when k n ·k n-1 =-b 2 When α=d, c and d are unequal numbers. When α=d, it means that a set of upper and lower bounds have been found and the iteration should enter the convergence stage.

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