A shield machine excavation parameter control method based on the longitudinal displacement of the shield tunnel

Abstract

The present invention relates to a shield machine excavation parameter control method based on the longitudinal displacement of the shield tunnel. First, the theoretical calculation length is determined according to the strength growth time of the grout behind the wall and the excavation speed; secondly, the nonlinear volume-related plastic deformation of the surrounding rock during the unloading process of the surrounding rock excavation is considered, and the equivalent foundation resistance coefficient of the synergistic effect of the surrounding rock and the lining structure is calculated; then, the sliding boundary condition at the other end when the segment assembly structure is jacked is considered, and a tunnel longitudinal displacement calculation model that can consider the volume-related plastic deformation of the surrounding rock and the solidification time of the grout behind the wall is constructed; finally, the longitudinal displacement of the segment assembly structure tunnel is predicted according to the jacking force. If the predicted maximum value is less than the allowable design value, the scheme is feasible. Otherwise, it is recommended to modify the excavation scheme. The method of the present invention takes into account various influencing factors and provides a theoretical basis for the optimization of control parameters in the excavation scheme such as the excavation speed, which is more scientific and safe.

Description

Technical Field

[0001] The invention relates to a shield machine excavation parameter control method based on the longitudinal displacement of a shield tunnel, and belongs to the technical field of shield machine parameter control. Background Art

[0002] Defects such as the initial misalignment of the assembled lining structure of the shield machine segment are often caused by unreasonable excavation plan design or lax construction control in the early stage of construction. At present, there is no complete theoretical method with displacement safety as the control target to verify the rationality of the control parameters in the excavation plan, especially the rationality of the excavation speed lacks a theoretical method for optimization design. Summary of the invention

[0003] In order to solve the problems existing in the prior art, the present invention provides a method for controlling the tunneling parameters of a shield machine by taking longitudinal displacement as a control target.

[0004] In order to achieve the above object, the technical solution proposed by the present invention is: a shield machine excavation parameter control method based on the longitudinal displacement of the shield tunnel, comprising the following steps:

[0005] Step 1: Determine the calculation length according to the strength growth time of the slurry behind the wall and the excavation speed;

[0006] Step 2: Calculate the equivalent foundation resistance coefficient of the tunnel surrounding rock according to the following formula:

[0007]

[0008] Where: u0 is the unloading displacement of the excavation wall, which is calculated according to the following formula:

[0009]

[0010] A=R pc -u c ; k kr is the average volume variation coefficient; R b is the outer radius of the tunnel lining; R b0 is the tunnel excavation radius; R pc is the radius of the plastic zone of nonlinear volume change;

[0011] p i is the interaction force between lining and surrounding rock, which is calculated according to the following formula:

[0012]

[0013] R a is the inner radius of the tunnel lining, Δu0 is the displacement of the surrounding rock that has been unloaded before lining construction;

[0014] Step 3: Considering the sliding boundary condition at the other end of the shield machine segment assembly structure during jacking, a calculation model for the longitudinal displacement of the tunnel is constructed:

[0015] w=(C1e αx +C2e -αx )cosβx+(C3e αx +C4e -αx )sinβx

[0016] In the formula: C1~C4 are unknown coefficients; D is the equivalent bending stiffness, C is the equivalent shear stiffness, N is the longitudinal thrust; x is the longitudinal length; K = k r ;

[0017] Step 4: Calculate the bending moment and axial force at the jacking end according to the jacking force in the designed excavation plan, and use the tunnel longitudinal displacement calculation model described in step 3 to predict the longitudinal displacement of the tunnel within the calculation length described in step 1 according to the bending moment and axial force at the jacking end. If the maximum value of the predicted longitudinal displacement of the tunnel is less than the allowable design displacement value and less than the floating amount of the designed safety control, the plan is feasible; otherwise, adjust the shield machine excavation parameters.

[0018] A further design of the above technical solution is as follows: the calculation formula of the equivalent shear stiffness C is as follows:

[0019]

[0020] Where: G c is the shear modulus of the segment; A c is the cross-sectional area of ​​the segment lining; c is the shear coefficient of the segment; ξ is the correction coefficient of the contact relationship between the segments; n is the number of longitudinal bolts.

[0021] The calculation formula of the equivalent bending stiffness D is as follows:

[0022] D=(EI) eq =ηE c I c

[0023] Where: η is the effective bending stiffness; E c is the elastic modulus of the segment concrete; I c is the moment of inertia of the segment lining section.

[0024] The bending stiffness effective rate η is calculated by the following formula:

[0025]

[0026] Where: A cis the cross-sectional area of ​​the segment lining; l s K is the lining segment ring width; j is the elastic stiffness coefficient of all longitudinal bolts, E b is the elastic modulus of the bolt; A b is the cross-sectional area of ​​the bolt; l b is the bolt length; ψ is the neutral axis position during the longitudinal bending deformation of the tunnel.

[0027] The neutral axis position ψ of the tunnel during longitudinal bending deformation is determined according to the following formula:

[0028]

[0029] Where: r is the distance from the longitudinal bolt to the center of the segment ring section, r = R a +t / 2, R a is the inner radius of the lining, t is the lining thickness, N is the axial force, and M is the bending moment.

[0030] The axial force N and bending moment M are calculated by the following formula:

[0031] N=σ top ·A c / 2+σ bot ·A c / 2

[0032] M=σ top ·A c / 2·y c -σ bot ·A c / 2·y c

[0033] Where: y c is the eccentricity of the axial force,

[0034] The beneficial effects of the present invention are:

[0035] The present invention establishes a simplified calculation formula for equivalent shear stiffness that takes into account the effect of segment joints, constructs a calculation method for equivalent foundation resistance coefficient that takes into account the synergistic effect of surrounding rock and lining structure, and considers the time-effectiveness of the mechanical properties of the grouting slurry behind the wall during shield machine excavation construction, and proposes a theoretical calculation method for the longitudinal displacement of the segment-jointed lining structure with the other end of the excavation thrust as the sliding boundary. Combined with the idea of ​​the allowable displacement deformation of the segment-assembled lining structure, taking the longitudinal displacement as the control target, a new way is provided for scientifically verifying the control parameters of the shield machine excavation scheme, and a theoretical method is also provided for optimizing the shield machine excavation construction scheme. Since the present invention takes into account the above-mentioned multiple influencing factors, the obtained shield machine excavation parameter control scheme is more in line with reality and the results are more accurate. BRIEF DESCRIPTION OF THE DRAWINGS

[0036] Figure 1 This is a schematic diagram of the surrounding rock division of tunnel excavation in this embodiment;

[0037] Figure 2 This is a schematic diagram of shear deformation calculation for different numbers of bolts;

[0038] Figure 3 It is the analytical value diagram of lining deflection under different n;

[0039] Figure 4 This is a schematic diagram of equivalent calculation of axial force and bending moment;

[0040] Figure 5 It is a schematic diagram of axial force eccentricity;

[0041] Figure 6 Comparison of longitudinal displacement curves of segmental lining structures calculated using different calculation methods. DETAILED DESCRIPTION

[0042] The present invention is described in detail below with reference to the accompanying drawings and specific embodiments.

[0043] Example

[0044] The present embodiment provides a shield machine excavation parameter control method based on the longitudinal displacement of the shield tunnel, comprising the following steps:

[0045] Step 1: Determine the theoretical calculation length L0 according to the strength growth time of the slurry behind the wall (the corresponding time when the compressive strength of the slurry is equal to the compressive strength of the adjacent stratum and is greater than the initial setting time of the slurry behind the wall, which is less than or equal to 3 days) and the excavation speed (90m is recommended when the excavation speed is greater than 30m / day); in this embodiment, the time for calculating the longitudinal length of the shield is 3 days, the excavation speed is 20-22m / day, and the calculated length is 64m.

[0046] Step 2: Based on the geological physical and mechanical parameters and design parameters of the tunnel, the equivalent foundation resistance coefficient of the surrounding rock is calculated by considering the volume-related plastic deformation of the surrounding rock during the unloading process of the surrounding rock excavation. In this embodiment, the tunnel is simplified into a theoretical calculation model of uniform strata, and the calculated physical and mechanical parameters are shown in Tables 1 to 3 below:

[0047] Table 1 Lining parameters of Dinghuaimen Tunnel theoretical calculation

[0048]

[0049] Table 2 Bolt parameters for theoretical calculation of Dinghuaimen Tunnel

[0050]

[0051] Table 3 Table of physical and mechanical parameters of the foundation of Dinghuaimen Tunnel theoretically calculated

[0052]

[0053] The Timoshenko beam theory based on the Winkler foundation in the prior art is currently the most widely used theoretical calculation method for tunnel longitudinal displacement. Its foundation resistance coefficient k is usually calculated using the elastic mechanics method, as shown in the following formula (1):

[0054]

[0055] Where: E s is the elastic modulus of the foundation soil; v is the Poisson's ratio of the foundation soil; R b is the outer radius of the lining.

[0056] However, this method does not take into account the characteristics of surrounding rock unloading failure after tunnel excavation and the synergistic effect of surrounding rock and lining structure. In particular, the surrounding rock shows obvious nonlinear volume changes in the plastic stage of unloading (rock mass surrounding rock is also called nonlinear expansion). The elastic mechanics method cannot reflect these factors. Therefore, this embodiment introduces the foundation resistance coefficient k considering the expansion coefficient. r The simplified calculation model of the tunnel is as follows: Figure 1 As shown in the figure, the surrounding rock crushing area in the rock tunnel is also called the nonlinear expansion area; the soil tunnel is called the nonlinear volume change area (i.e. the plastic area of ​​volume change); the displacement calculation formula at the excavated tunnel wall is as follows:

[0057]

[0058] Where: A = R pc -u c ; k kr is the average volume change coefficient (i.e., expansion coefficient), and the average value in this embodiment is -0.008.

[0059]

[0060]

[0061]

[0062] Where: c′ is the cohesion of the crushing zone; is the internal friction angle of the crushing zone; p0 is the initial ground stress; p i is the interaction force between lining and surrounding rock; c is the initial cohesion of surrounding rock; is the initial internal friction angle of surrounding rock; R b0 is the tunnel excavation radius; R pcis the radius of the plastic zone of nonlinear volume change; v is the Poisson's ratio of the surrounding rock; E s is the initial elastic modulus of surrounding rock.

[0063] Lining upper reaction p i After that, the displacement calculation formula at the outer radius of the lining is as follows:

[0064]

[0065] Where: R a is the inner radius of the tunnel lining; R b is the outer radius of the tunnel lining; Vc is the Poisson's ratio of the segment concrete lining structure; Ec is the elastic modulus of the segment concrete lining structure.

[0066] Before the lining construction, the surrounding rock has produced an unloading displacement of Δu0; then according to the synergistic effect of the surrounding rock and the lining, the relationship between the displacement of the excavation wall and the displacement of the outer wall of the lining can be obtained as shown in the following formula:

[0067] ||u′0||=||u0||-||Δu0|| (4)

[0068] Where: u0 is the displacement of the excavation wall; u0' is the displacement of the lining outer wall;

[0069] According to (2), (3), and (4), we can obtain u0 and p i .

[0070] Therefore, the foundation resistance coefficient k of this embodiment considering the nonlinear volume change area of ​​the surrounding rock and the coordinated deformation of the surrounding rock and lining structure is r Calculated by the following formula:

[0071]

[0072] The foundation resistance coefficient calculated for the tunnel in this embodiment is 8.76 MPa / m.

[0073] Step three, considering the sliding boundary conditions at the other end of the shield machine segment assembly structure during jacking, a theoretical calculation model and formula for longitudinal displacement that can take into account the volume-related plastic deformation of the surrounding rock and the solidification time of the grouting liquid behind the wall are constructed.

[0074] The grouting layer behind the wall has certain viscoelastic plasticity, especially during construction. It generally takes many days to completely harden. Therefore, under the action of the thrust, the other end will have a vertical axial displacement, so the other end uses a slip boundary that is more in line with the actual situation. In order to simplify the theoretical calculation model, this embodiment uses the model simulation after half of the symmetrical loading. According to the symmetry, the middle section is equivalent to the slip boundary, that is, the deflection deformation of the longitudinal structure of the tunnel when the two ends are bent under the tunnel length of 2l is calculated, and then half of the symmetrical longitudinal structure of the tunnel is taken. At this time, the boundary condition at the far end of the structure is the slip boundary. The calculation process is as follows:

[0075] The shear equilibrium equation of the Timoshenko beam microsegment on the Winkler foundation is as follows:

[0076]

[0077] According to the above formula (6), we can get:

[0078]

[0079] The flexural equilibrium equation of the Timoshenko beam micro-segment on the Winkler foundation is as follows:

[0080]

[0081] Where: D is the equivalent bending stiffness, D = (EI) eq , E is the elastic modulus; I is the section inertia moment; C is the equivalent shear stiffness, C = (κGA) eq ; N is the longitudinal thrust; K is the structure-foundation resistance coefficient, that is, the foundation resistance coefficient k of the knife calculated in step 2 r .

[0082]

[0083]

[0084] Where: w is the deflection of the beam; φ is the rotation angle of the beam; γ is the shear angle; Q is the section shear force; G is the shear modulus; A is the cross-sectional area; κ is the shear coefficient.

[0085] According to equations (8), (9) and (10), the governing differential equation of the disturbance (i.e., the longitudinal displacement of the tunnel) of the Timoshenko beam on the Winkler foundation considering the influence of the axial force is obtained:

[0086]

[0087] The general solution of the deflection (i.e., the deformation of the tunnel lining structure along the axial direction perpendicular to the axial direction, referred to as the tunnel longitudinal displacement) control equation is obtained by solving:

[0088] w=(C1eαx +C2e -αx )cosβx+(C3e αx +C4e -αx )sinβx (12)

[0089] Where: C1~C4 are unknown coefficients, determined according to boundary conditions; x is the longitudinal length;

[0090] When both ends are bent, the beam section rotation angle is obtained according to equations (8) and (7):

[0091]

[0092] According to Timoshenko Liang And formula (13), the beam section bending moment can be obtained as:

[0093]

[0094] For a longitudinal structure that is symmetrically bent at both ends, the boundary conditions are: w| x＝0 =0,M| x＝0 =M0,w| x＝2l =0,M| x＝2l =M0, according to equations (12) and (13), the solution equations for the unknown coefficients C1~C4 can be obtained:

[0095]

[0096] K 41 =(m1cosβL-m2sinβL)e αL

[0097] K 42 =(m1cosβL-m2sinβL)e -αL

[0098] K 43 =(m1sinβL+m2cosβL)e αL

[0099] K 44 =(m1sinβL+m2cosβL)e -αL

[0100] Where: m1 = c(α 2 -β 2 )+d(α 4 -6α 2 β 2 +β 4 ), m2=2cαβ+4d(α 3β-αβ 3 ), By solving C1~C4, we can get the deflection curve function w(x), x∈[0,l] of the tunnel longitudinal structure under the sliding boundary.

[0101] Since the shear stiffness and bending stiffness of the joint connected by bolts are related to complex factors such as the number, strength, and anchoring quality of the bolts, this embodiment adopts equivalent calculation, and the equivalent calculation method is as follows:

[0102] (1) Equivalent bending stiffness D

[0103] This embodiment adopts the nonlinear equivalent bending stiffness theory considering the influence of the longitudinal axial force, as shown in formula (16):

[0104] D=(EI) eq =ηE c I c (16)

[0105]

[0106] Where: η is the effective bending stiffness, calculated according to formula (16); E c is the elastic modulus of the segment concrete; I c A is the moment of inertia of the segment lining section; c is the cross-sectional area of ​​the segment lining; l s K is the lining segment ring width; j is the elastic stiffness coefficient of all longitudinal bolts, n is the number of longitudinal bolts; E b is the elastic modulus of the bolt; A b is the cross-sectional area of ​​the bolt; l b is the bolt length; ψ is the neutral axis position of the tunnel during longitudinal bending deformation, which is determined according to the following formula:

[0107]

[0108] Where: r is the distance from the longitudinal bolt to the center of the segment ring section, r = R a +t / 2, R a is the inner radius of the lining, t is the lining thickness; N is the longitudinal thrust (i.e. axial force); M is the bending moment. , η=1.

[0109] (2) Equivalent shear stiffness C

[0110] The longitudinal shear stiffness of the segment assembly structure is mainly related to the joint effect. This embodiment adopts an equivalent method to deal with it. The equivalent shear stiffness C is mainly related to the number of bolts n, the strength of the bolts themselves, the bolt anchoring looseness and tightness effect, etc. When the bolts are regular bolts and the construction is in accordance with the specifications, the number of bolts has the greatest impact on the equivalent shear stiffness. In addition, as a whole, it is a composite structure of multiple pipe sections and multiple joint sections. Therefore, from an equivalent perspective, it is recommended to use the equivalent unit shear stiffness (i.e., the shear stiffness per unit length) for the longitudinal displacement calculation. The calculation method of the equivalent shear stiffness is established as follows:

[0111] First, the equivalent unit shear stiffness (i.e., shear stiffness per unit length) is defined: the equivalent shear stiffness corresponding to a unit displacement produced by the equivalent influence length.

[0112] According to the definition, when there are no bolts, the affected length is the length of a pipe segment, that is, the unit length L1 of a single joint. Then the shear displacement can be calculated using the following formula:

[0113]

[0114] Where: C 无螺栓 = ζk c G c A c =3.5k c G c A c ; G c is the shear modulus of the segment; A c is the cross-sectional area of ​​the segment lining. c The shear coefficient of the segment is related to the integrity of the segment structure itself, and is empirically set between 0 and 1. In this case, κ is used. c =0.53.

[0115] ξ is the correction coefficient of the contact relationship between the segments, also known as the equivalent shear stiffness correction coefficient, which is determined based on the shear test of the inter-ring joints. In the calculation of this embodiment, ξ=3.5 is taken.

[0116] For segment-assembled structural lining, when bolts are added, the shear displacement influence range will be further expanded, and the expansion range is proportional to the number of bolts, that is, the more bolts there are, the stronger the shear transmission capacity of the joint will be, and the wider the influence range will be. The equivalent length of the overall shear stiffness of the bolts is called the "equivalent influence length L of the joint". # Therefore, the calculation formula for the shear displacement of the equivalent impact length lining structure is as follows:

[0117]

[0118] ζ c It can be simplified as a function of the number of bolts n. In order to simplify the calculation, this embodiment is rewritten as the following formula:

[0119]

[0120] Therefore, the schematic diagram of equivalent unit shear stiffness calculation considering bolt effect is as follows Figure 2 :

[0121]

[0122] When the number of bolts n→0, the affected length is only one pipe segment. 无螺栓 = ζk c G c A c =3.5k c G c A c Therefore, when there are n bolts, this case uses the following formula for calculation:

[0123]

[0124] When the number of bolts reaches a certain value, the equivalent influence length exceeds the influence length of the elastic foundation beam, and adding more bolts has basically no effect. According to the trial calculation, when n>75, w max It tends to 0.02mm, that is, when the number of bolts n exceeds 75, the longitudinal joint effect tends to converge, and the joint weakening effect basically disappears at this time. The equivalent shear stiffness and other parameters calculated for different numbers of bolts are shown in Table 4.

[0125] According to the equivalent unit shear stiffness calculated in this embodiment, a fixed-end assumption model is adopted to plot the predicted longitudinal displacement analytical value curves within the tunnel calculation length of this embodiment (the calculation length is 64m obtained according to step 1) when n=1, 30, and 75. Figure 3 .

[0126] Table 4 Calculation results of lining deflection after the revised relationship between n and C0

[0127]

[0128] According to the jacking force in the designed excavation scheme, the bending moment and axial force at the jacking end are calculated using the structural mechanics method. The calculation process is as follows:

[0129] Assume that the upper semicircular ring of the lining is subjected to a uniformly distributed compressive load σ top , the lower half is affected by σ bot (Regulation σ top >σ bot ),like Figure 4 As shown, it can be converted into axial force N and bending moment M through theoretical mechanics. The calculation formula is as follows:

[0130]

[0131] Where: y c is the eccentricity of the axial force, that is, the distance from the centroid of the upper semicircular ring of the lining to the center of the circular ring, and is calculated as follows.

[0132] like Figure 5 As shown, take the infinitesimal element on the lining ring and approximate the ring as a trapezoid. The coordinates of the center of gravity of this trapezoid are Therefore, the process of solving the centroid of the upper semicircular ring of the lining is as follows:

[0133]

[0134] So c The calculation formula is:

[0135]

[0136] Step 4: Use the tunnel longitudinal displacement calculation model described in step 3 to predict the longitudinal displacement of the tunnel within the calculation length described in step 1. If the maximum predicted longitudinal displacement of the tunnel is less than the allowable design displacement value and less than the floating amount of the design safety control, the plan is feasible; otherwise, modify the excavation plan or control parameters, and adjust or control the distribution of the jacking force of the pipe segment, or adjust the jacking speed, or adjust the mechanical parameters of the grouting fluid, etc.

[0137] The allowable displacement of the tunnel segment in this case is 20 mm. The calculated parameter values ​​are shown in Table 5. The maximum displacement predicted by the existing jacking scheme is 0.437 mm. The comparison curve of the calculated values ​​of different methods is shown below. Figure 6 According to the method of this embodiment, it is judged that the displacement control of the construction scheme of the tunnel boring machine is reasonable and meets the design requirements. It is estimated that the initial maximum misalignment is less than 0.437 mm.

[0138] Table 5 Peak value of lining deflection based on different expansion effects under sliding end (theoretical)

[0139]

[0140] This embodiment realizes the theoretical prediction of the longitudinal displacement of the shield tunnel taking into account the characteristics of the grouting fluid, the plasticity related to the unloading volume of the surrounding rock, the characteristics of the segment joints, and the synergistic effect of the surrounding rock and the segment structure, providing a theoretical basis for the optimization of control parameters in the excavation scheme such as the excavation speed in a more scientific and safer way.

[0141] The technical solutions of the present invention are not limited to the above-mentioned embodiments, and all technical solutions obtained by equivalent replacement methods fall within the scope of protection required by the present invention.

Claims

1. A shield machine excavation parameter control method based on the longitudinal displacement of the shield tunnel, characterized in that: The steps include: Step 1: Determine the calculation length according to the strength growth time of the slurry behind the wall and the excavation speed; Step 2: Calculate the equivalent foundation resistance coefficient of the tunnel surrounding rock according to the following formula: Where: u0 is the unloading displacement of the excavation wall, which is calculated according to the following formula: A=R pc -u c ; k kr is the average volume variation coefficient; R b is the outer radius of the tunnel lining; R b0 is the tunnel excavation radius; R pc is the radius of the plastic zone of nonlinear volume change; p i is the interaction force between lining and surrounding rock, which is calculated according to the following formula: ||u′0||=||u0||-||Δu0||; R a is the inner radius of the tunnel lining, Δu0 is the displacement of the surrounding rock that has been unloaded before lining construction; Step 3: Considering the sliding boundary condition at the other end of the shield machine segment assembly structure during jacking, a calculation model for the longitudinal displacement of the tunnel is constructed: w=(C1e αx +C2e -αx )cosβx+(C3e αx +C4e -αx )sinβx In the formula: C1~C4 are unknown coefficients; D is the equivalent bending stiffness, C is the equivalent shear stiffness, N is the longitudinal thrust; x is the longitudinal length; K = k r ; Step 4: Calculate the bending moment and axial force at the jacking end according to the jacking force in the designed excavation scheme. Use the tunnel longitudinal displacement calculation model described in step 3 to predict the longitudinal displacement of the tunnel within the calculated length described in step 1. If the maximum value of the predicted longitudinal displacement of the tunnel is less than the allowable design displacement value and less than the floating amount of the designed safety control, the scheme is feasible. Otherwise, adjust the shield machine excavation parameters.

2. The shield machine excavation parameter control method based on the longitudinal displacement of the shield tunnel according to claim 1 is characterized in that: The calculation formula of the equivalent shear stiffness C is as follows: Where: G c is the shear modulus of the segment; A c is the cross-sectional area of ​​the segment lining; c is the shear coefficient of the segment; ξ is the correction coefficient of the contact relationship between the segments; n is the number of longitudinal bolts.

3. The shield machine excavation parameter control method based on the longitudinal displacement of the shield tunnel according to claim 2 is characterized in that: The calculation formula of the equivalent bending stiffness D is as follows: D=(EI) eq =ηE c I c Where: η is the effective bending stiffness; E c is the elastic modulus of the segment concrete; I c is the moment of inertia of the segment lining section.

4. The shield machine excavation parameter control method based on the longitudinal displacement of the shield tunnel according to claim 3 is characterized in that: The bending stiffness effective rate η is calculated by the following formula: Where: A c is the cross-sectional area of ​​the segment lining; l s K is the lining segment ring width; j is the elastic stiffness coefficient of all longitudinal bolts, E b is the elastic modulus of the bolt; A b is the cross-sectional area of ​​the bolt; l b is the bolt length; ψ is the neutral axis position during the longitudinal bending deformation of the tunnel.

5. The shield machine excavation parameter control method based on the longitudinal displacement of the shield tunnel according to claim 4 is characterized in that: The neutral axis position ψ of the tunnel during longitudinal bending deformation is determined according to the following formula: Where: r is the distance from the longitudinal bolt to the center of the segment ring section, r = R a +t / 2, R a is the inner radius of the lining, t is the lining thickness, N is the axial force, and M is the bending moment.

6. The shield machine excavation parameter control method based on the longitudinal displacement of the shield tunnel according to claim 5 is characterized in that: The axial force N and bending moment M are calculated by the following formula: N=σ top ·A c / 2+σ bot ·A c / 2 M=σ top ·A c / 2·y c -s bot ·A c / 2·y c Where: y c is the eccentricity of the axial force,

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