A method for calculating the longitudinal displacement of existing shield tunnels caused by diaphragm wall construction

Abstract

The application discloses a kind of diaphragm wall construction caused existing shield tunnel longitudinal displacement calculation method, comprising: step 1, according to the stratification of diaphragm wall excavation soil body and relevant mechanical parameters obtained in geological exploration report;Step 2, according to the specific gravity and average thickness of soil body, uniformly distributed unloading is calculated;Step 3, the vertical unloading stress at the axial position of existing shield tunnel is calculated;Step 4, the longitudinal displacement w (x) of existing shield tunnel is calculated 地连墙成槽开挖过程 ;Step 5: the vertical additional stress at the axial position of existing shield tunnel is calculated;Step 6, the longitudinal displacement w (x) of existing shield tunnel is calculated 地连墙混凝土浇筑过程 ;Step 7, using superposition principle, the longitudinal displacement of existing shield tunnel is calculated.The purpose of the application is to propose a kind of diaphragm wall construction caused existing shield tunnel longitudinal displacement calculation method, can quickly determine the longitudinal displacement of existing tunnel caused by diaphragm wall construction process grooving stage and concrete pouring stage.

Description

Technical Field

[0001] This invention relates to the field of shield tunnel technology, specifically to a method for calculating the longitudinal displacement of existing shield tunnels caused by diaphragm wall construction. Background Technology

[0002] With urban development and rail transit construction, central urban areas face the challenge of commercial development around subway tunnels. To ensure the safety and normal operation of subway tunnels, it is essential to conduct research on the impact of deep foundation pits near subway tunnels. Typically, research on the impact of deep foundation pit projects on adjacent shield tunnels focuses on the excavation process, neglecting the impact of diaphragm wall construction. Diaphragm wall construction can be divided into trench excavation and concrete pouring stages. Both stages generate additional stress in the surrounding soil, potentially causing displacement of the existing tunnel and affecting its structural safety.

[0003] Therefore, the impact of diaphragm wall construction on the displacement of existing tunnels has certain engineering reference significance for assessing the safety of existing tunnels. Currently, numerical simulation is mainly used to study this issue. However, numerical analysis requires appropriate soil stress-strain relationships and relatively accurate mechanical parameters, which is not simple and easy to implement in engineering practice. Summary of the Invention

[0004] In view of the shortcomings of the prior art mentioned above, the purpose of this invention is to propose a method for calculating the longitudinal displacement of existing shield tunnels caused by diaphragm wall construction, which can quickly determine the longitudinal displacement of existing tunnels caused by the trenching stage and the concrete pouring stage of the diaphragm wall construction process.

[0005] To achieve the above objectives, the technical solution of the present invention is as follows:

[0006] A method for calculating the longitudinal displacement of an existing shield tunnel caused by diaphragm wall construction includes the following steps:

[0007] Step 1: Obtain the soil stratification and related mechanical parameters for the diaphragm wall excavation based on the geological survey report, as well as the relevant mechanical parameters of the strata where the existing shield tunnel is located;

[0008] Step 2: Calculate the uniform unloading caused by soil excavation during the trenching process of diaphragm wall construction based on the unit weight and average thickness of each layer of soil in the excavated part.

[0009] Step 3: Calculate the vertical unloading stress at the axial position of the existing shield tunnel caused by the soil excavation and unloading action during the trenching process of the diaphragm wall;

[0010] Step 4: Calculate the longitudinal displacement w(x) of the existing shield tunnel under the action of soil excavation during the trenching process of the diaphragm wall. 地连墙成槽开挖过程 ;

[0011] Step 5: Calculate the additional vertical stress at the axial position of the existing shield tunnel caused by the loading action during the concrete pouring process of the diaphragm wall;

[0012] Step 6: Calculate the longitudinal displacement w(x) of the existing shield tunnel under loading during the diaphragm wall concrete pouring process. 地连墙混凝土浇筑过程 ;

[0013] Step 7: Using the superposition principle, calculate the longitudinal displacement of the existing shield tunnel caused by the construction process of the diaphragm wall.

[0014] Furthermore, in step 1, the soil layers of the diaphragm wall excavation and the unit weight γi and average thickness hi of each soil layer are obtained based on the geological survey report; the subgrade coefficient k and Poisson's ratio v of the stratum where the existing shield tunnel is located are obtained.

[0015] Further, step 2 specifically involves: calculating and accumulating the uniformly distributed unloading p0 caused by soil excavation during the trenching process of the diaphragm wall, based on the unit weight and thickness of each soil layer. The calculation expression is shown in equation (1):

[0016]

[0017] In the formula, n is the number of soil layers, γi and hi represent the unit weight and thickness of each soil layer, respectively, and h is the excavation depth of the diaphragm wall.

[0018] Furthermore, step 3 specifically includes the following steps:

[0019] Step 3.1: Construct a two-dimensional coordinate system for the diaphragm wall with the center of the diaphragm wall as the origin, with the κ axis along the extension direction of the diaphragm wall and the λ axis along the width direction of the diaphragm wall.

[0020] Step 3.2: Take any point along the extension direction of the existing tunnel as the origin of the existing shield tunnel coordinate system, take the extension direction of the tunnel as the horizontal axis x-axis of the tunnel coordinate system, and take the direction perpendicular to the extension direction of the tunnel as the vertical axis y-axis of the tunnel coordinate system.

[0021] Step 3.3: The corresponding x and y coordinates of any point in the tunnel coordinate system xy in the diaphragm wall coordinate system κ-λ, i.e., the transformation relationship between the two coordinate axes, is shown in equation (2):

[0022]

[0023] In the formula: x and y are the coordinates of any point N in the tunnel coordinate system xy; X and Y are the corresponding abscissa and ordinate of point N in the diaphragm wall coordinate system κ-λ; d is the horizontal distance between the origins of the two coordinate systems; the angle between the line connecting the κ axis and the origin of the coordinate system is β, and the angle between the κ axis and the tunnel extension direction is α.

[0024] Step 3.4: The distance between any point N in the tunnel extension direction and the diaphragm wall can be controlled by parameters R1 and R2, as shown in equation (3):

[0025]

[0026] In the formula: R1 and R2 are the distances between any point N in the tunnel extension direction and any point at the top and bottom of the diaphragm wall, respectively;

[0027] Step 3.5: Combining equations (2) and (3), the vertical unloading stress at the axial position of the existing shield tunnel caused by soil excavation and unloading during the trenching process of the diaphragm wall is shown in equation 4:

[0028]

[0029] In the formula: p(x) is the vertical unloading stress at the axial position of the existing shield tunnel caused by soil excavation and unloading during the trenching process of the diaphragm wall; where H is the burial depth of the existing tunnel, B is the width of the diaphragm wall, and L is the extension length of the diaphragm wall.

[0030] Furthermore, step 4 specifically includes the following steps:

[0031] Step 4.1: Simplify the shield tunnel as a beam, and perform force analysis on a micro-element of the tunnel to obtain the force balance equation and bending moment balance equation of the micro-element, the expression of which is shown in equation (5):

[0032]

[0033] In the formula: Q and M are the shear force and bending moment on the cross section of the infinitesimal element, respectively; D is the tunnel diameter; p k p represents the ground reaction force of the underlying soil on the tunnel foundation. k =kw(x);

[0034] Step 4.2: The differential equation of the beam's deflection curve is shown in equation (6):

[0035]

[0036] In the formula: E and I are the elastic modulus and moment of inertia of the existing tunnel, respectively;

[0037] Step 4.3: Substituting equation (6) into equation (5) yields the differential expression for the longitudinal displacement of the existing shield tunnel under the vertical load of soil excavation during the diaphragm wall trenching process, as shown in equation (7):

[0038]

[0039] Equation (7) is a fourth-order ordinary differential equation. It is solved using Matlab and Mathematics. The resulting expression for the longitudinal displacement of the existing tunnel is w(x). 地连墙成槽开挖过程 .

[0040] Furthermore, step 5 specifically includes the following steps:

[0041] Step 5.1: During the diaphragm wall concrete pouring process, the original soil is replaced with concrete. The concrete pouring process is equivalent to a loading process, and the load is a uniformly distributed load q0 = γ. 混凝土重度 h where: γ 混凝土重度 The unit weight of concrete;

[0042] Step 5.2: The corresponding abscissa and ordinate values ​​of any point in the tunnel coordinate system xy in the diaphragm wall coordinate system κ-λ, that is, the transformation relationship between the two coordinate axes is shown in Equation (2);

[0043] Step 5.3: The distance between any point N in the tunnel extension direction and the diaphragm wall can be controlled by parameters R1 and R2, as shown in equation (3);

[0044] Step 5.4: Combining equations (2) and (3), the additional vertical stress at the axial position of the existing shield tunnel caused by the loading action during the concrete pouring process of the diaphragm wall is shown in equation (8):

[0045]

[0046] In the formula: q(x) is the vertical additional stress at the axial position of the existing shield tunnel caused by the loading action during the concrete pouring process of the diaphragm wall.

[0047] Furthermore, step 6 specifically includes the following steps:

[0048] Step 6.1: Simplify the shield tunnel as a beam, take a micro element of the tunnel for stress analysis, the expression is shown in Equation (5), replace p(x) in Equation (5) with q(x) to obtain the stress balance equation and bending moment balance equation of the micro element, as shown in Equation (9);

[0049]

[0050] Step 6.2: Obtain the differential equation of the deflection curve of the beam, as shown in equation (10);

[0051]

[0052] Step 6.3: Substituting equation (6) into equation (5) yields the differential expression for the longitudinal displacement of the existing shield tunnel under loading during the diaphragm wall concrete pouring process, as shown in equation (11):

[0053]

[0054] Equation (11) is a fourth-order ordinary differential equation. It is solved using Matlab and Mathematics. The resulting expression for the longitudinal displacement of the existing tunnel is w(x). 地连墙混凝土浇筑过程 .

[0055] Furthermore, step 7 specifically involves: using the superposition principle, superimposing the longitudinal displacement of the existing shield tunnel caused by soil excavation during the diaphragm wall trenching process with the longitudinal displacement of the existing shield tunnel caused by loading during the concrete pouring process yields the longitudinal displacement w(x) of the existing shield tunnel caused by the diaphragm wall construction process. 地连墙施工过程隧道纵向位移 The expression is shown in equation (12).

[0056] As shown:

[0057] w(x) 地连墙施工过程隧道纵向位移 =w(x) 地连墙成槽开挖过程 +w(x) 地连墙混凝土浇筑过程

[0058] (12).

[0059] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0060] (1) The method for calculating the longitudinal displacement of existing shield tunnels caused by diaphragm wall construction in this invention takes into account the fact that the impact of diaphragm wall construction on adjacent tunnels is not fully considered in deep foundation pit engineering, which may lead to tunnel displacement. Therefore, this invention divides the longitudinal displacement of shield tunnels into a series of steps. By using the soil stratification and related mechanical parameters of the diaphragm wall excavation and the relevant mechanical parameters of the strata where the existing shield tunnel is located, the uniform unloading caused by the soil excavation and unloading during the trenching process of the diaphragm wall is calculated. At the same time, a two-dimensional coordinate system of the diaphragm wall is constructed to calculate the vertical unloading stress at the axial position of the shield tunnel. The shield tunnel is simplified as a beam, and a micro-element of the tunnel is taken for stress analysis. The stress balance equation and bending moment balance equation of the micro-element are constructed. Based on the established force equilibrium equation and moment equilibrium equation of the micro-element, the longitudinal displacement of the existing shield tunnel under the action of soil excavation during the trenching process of the diaphragm wall can be calculated. At this time, the vertical additional stress at the axial position of the shield tunnel caused by the loading action during the concrete pouring process of the diaphragm wall can be calculated. Based on the established force equilibrium equation and moment equilibrium equation of the micro-element, the longitudinal displacement of the existing shield tunnel under the loading action during the concrete pouring process of the diaphragm wall can be calculated. After superimposing the longitudinal displacement of the existing shield tunnel under the action of soil excavation during the trenching process of the diaphragm wall and the longitudinal displacement of the existing shield tunnel under the loading action during the concrete pouring process of the diaphragm wall, the longitudinal displacement of the shield tunnel caused by the diaphragm wall construction process can be obtained, which is convenient for engineers to adjust construction parameters and dynamically control the longitudinal displacement of the existing tunnel.

[0061] (2) This invention divides the longitudinal displacement of the shield tunnel into two stages: the diaphragm wall excavation and trenching stage, and the concrete pouring stage. Both stages generate additional stress in the surrounding soil. The longitudinal displacement of the shield tunnel can be obtained separately during the diaphragm wall excavation and trenching stage and the concrete pouring stage, facilitating engineers to dynamically control the longitudinal displacement of the existing tunnel by adjusting construction parameters. This method is quick, easy to implement, and highly applicable; it has strong versatility for dynamically controlling and assessing the impact of surrounding construction disturbances on existing tunnels. Attached Figure Description

[0062] Figure 1 This is a schematic diagram of the method for calculating the longitudinal displacement of existing shield tunnels caused by the construction of diaphragm walls according to the present invention.

[0063] Figure 2 This is a plan view of the soil unloading process and the relative position of the existing tunnel during the trenching process of the diaphragm wall of this invention;

[0064] Figure 3 This is a plan view showing the relative position of the diaphragm wall concrete pouring process and the existing tunnel in this invention.

[0065] Figure 4 This is a calculation model diagram of the longitudinal displacement of an existing tunnel caused by soil unloading during the trenching process of the diaphragm wall of the present invention.

[0066] Figure 5 This is a calculation model diagram of the longitudinal displacement of the existing tunnel caused by the concrete pouring process of the diaphragm wall of the present invention.

[0067] Figure 6 This is a schematic diagram showing the relative position of the diaphragm wall of this invention and the existing tunnel;

[0068] Figure 7 The longitudinal displacement curves of the existing tunnel caused by the wall-forming process, the concrete pouring process, and the completion of construction are presented in this invention. Detailed Implementation

[0069] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention. Furthermore, the technical features involved in the various embodiments of this invention described below can be combined with each other as long as they do not conflict with each other. Based on the embodiments of this invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this invention.

[0070] Please see the appendix Figure 1-7 A method for calculating the longitudinal displacement of existing shield tunnels caused by diaphragm wall construction includes the following steps:

[0071] Step 1: Based on the geological survey report, obtain the unit weight γi and average thickness hi of the soil layer; obtain the subgrade coefficient k and Poisson's ratio v of the stratum where the existing shield tunnel is located. When the soil layer is silty fine sand, the unit weight γ of the soil layer is 18.0 kN / m³ according to the geological survey report. 3 The bed coefficient k is 20 MPa / m and the Poisson's ratio v is 0.25.

[0072] Step 2: Based on the unit weight and thickness of each soil layer, calculate and sum the uniformly distributed unloading p0 caused by soil excavation during the trenching process of the diaphragm wall. The calculation expression is as follows:

[0073]

[0074] In the formula, h is the excavation depth of the diaphragm wall.

[0075] Step 3: Construct a two-dimensional coordinate system for the diaphragm wall with the center of the diaphragm wall as the origin, with the κ axis along the extension direction of the diaphragm wall and the λ axis along the width direction of the diaphragm wall.

[0076] Furthermore, take any point along the existing tunnel extension direction as the origin of the existing shield tunnel coordinate system, the tunnel extension direction as the horizontal axis x-axis of the tunnel coordinate system, and the perpendicular tunnel extension direction as the vertical axis y-axis of the tunnel coordinate system.

[0077] Furthermore, the corresponding abscissa and ordinate values ​​of any point in the tunnel coordinate system xy in the diaphragm wall coordinate system κ-λ, i.e., the transformation relationship between the two coordinate axes, are shown in equation (2):

[0078]

[0079] In the formula: x and y are the coordinates of any point N in the tunnel coordinate system xy; X and Y are the corresponding abscissa and ordinate of point N in the diaphragm wall coordinate system κ-λ; d is the horizontal distance between the origins of the two coordinate systems; the angle between the line connecting the κ axis and the origin of the coordinate system is β, and the angle between the κ axis and the tunnel extension direction (i.e., the x-axis) is α; the diaphragm wall is parallel to the existing tunnel, in which case α is 0 and β is 90°.

[0080] Furthermore, the distance between any point N in the tunnel extension direction and the diaphragm wall can be controlled by parameters R1 and R2, as shown in equation (3):

[0081]

[0082] In the formula: R1 and R2 are the distances between any point N in the tunnel extension direction and any point at the top and bottom of the diaphragm wall, respectively;

[0083] Furthermore, combining equations (2) and (3), the vertical unloading stress at the axial position of the existing shield tunnel caused by the soil excavation and unloading action during the trenching process of the diaphragm wall is shown in equation 4:

[0084]

[0085] In the formula: p(x) is the vertical unloading stress at the axial position of the existing shield tunnel caused by soil excavation and unloading during the trenching process of the diaphragm wall; where H is the burial depth of the existing tunnel, B is the width of the diaphragm wall, and L is the extension length of the diaphragm wall, and H is 15m in this case.

[0086] like Figure 2-3 As shown, this invention provides a calculation model diagram for the longitudinal displacement of existing tunnels caused by soil unloading during the trenching process of diaphragm wall construction. Figure 2-3 A method for obtaining the vertical unloading stress at the axial position of an existing shield tunnel caused by soil excavation and unloading during the trenching process of diaphragm wall construction.

[0087] Step 4: Simplify the shield tunnel as an Euler beam, and perform force analysis on a micro-element of the tunnel to obtain the force balance equation and bending moment balance equation of the micro-element, the expression of which is shown in equation (5):

[0088]

[0089] In the formula: Q is the shear force on the cross section of the infinitesimal element, M is the bending moment on the cross section of the infinitesimal element; D is the tunnel diameter, which is 6.2m in this case; p k p represents the ground reaction force of the underlying soil on the tunnel foundation. k =kw(x);

[0090] Furthermore, the differential equation for the deflection curve of the beam is shown in equation (6):

[0091]

[0092] In the formula: E is the elastic modulus of the existing tunnel, and I is the moment of inertia of the existing tunnel section;

[0093] Furthermore, substituting equation (6) into equation (5) yields the differential expression for the longitudinal displacement of the existing shield tunnel under the vertical load of soil excavation during the diaphragm wall trenching process, as shown in equation (7):

[0094]

[0095] Equation (7) is a fourth-order ordinary differential equation. It is solved using Matlab and Mathematics, and the expression for the longitudinal displacement of the existing tunnel is w(x). 地连墙成槽开挖过程 .

[0096] Step 5: During the diaphragm wall concrete pouring process, the original soil is replaced with concrete. The concrete pouring process is equivalent to a loading process, and the load is a uniformly distributed load q0 = γ. 混凝土重度 h where: γ混凝土重度 Unit weight of concrete; γ 混凝土重度 24KN / m 3 .

[0097] Furthermore, the corresponding abscissa and ordinate values ​​of any point in the tunnel coordinate system xy in the diaphragm wall coordinate system κ-λ, i.e. the transformation relationship between the two coordinate axes, are shown in Equation (2).

[0098] Furthermore, the distance between any point N in the tunnel extension direction and the diaphragm wall can be controlled by parameters R1 and R2, as shown in equation (3);

[0099] Furthermore, combining equations (2) and (3), the additional vertical stress at the axial position of the existing shield tunnel caused by the loading action during the concrete pouring process of the diaphragm wall is shown in equation (8):

[0100]

[0101] In the formula: q(x) is the vertical additional stress at the axial position of the existing shield tunnel caused by the loading action during the concrete pouring process of the diaphragm wall.

[0102] like Figure 4-6 As shown, this invention provides a calculation model diagram for the longitudinal displacement of existing tunnels caused by the concrete pouring process of the diaphragm wall. Figure 4-6 It can obtain the vertical additional stress at the axial position of the existing shield tunnel caused by the loading action during the concrete pouring process of the diaphragm wall.

[0103] Step 6: Simplify the shield tunnel as a beam, take a micro element of the tunnel for stress analysis, the expression is shown in Equation (5), replace p(x) in Equation (5) with q(x) to obtain the stress balance equation and bending moment balance equation of the micro element, as shown in Equation (9);

[0104]

[0105] Furthermore, the differential equation for the deflection curve of the beam is obtained;

[0106]

[0107] Furthermore, substituting equation (6) into equation (5) yields the differential expression for the longitudinal displacement of the existing shield tunnel under loading during the diaphragm wall concrete pouring process, as shown in equation (11):

[0108]

[0109] Equation (11) is a fourth-order ordinary differential equation. It is solved using Matlab and Mathematics. The resulting expression for the longitudinal displacement of the existing tunnel is w(x). 地连墙混凝土浇筑过程 .

[0110] Step 7: By superimposing the longitudinal displacement of the existing shield tunnel caused by soil excavation during the diaphragm wall trenching process with the longitudinal displacement of the existing shield tunnel caused by loading during the concrete pouring process, the longitudinal displacement w(x) of the existing shield tunnel caused by the diaphragm wall construction process can be obtained. 地连墙施工过程隧道纵向位移 The expression is shown in equation (12):

[0111] w(x) 地连墙施工过程隧道纵向位移 =w(x) 地连墙成槽开挖过程 +w(x) 地连墙混凝土浇筑过程

[0112] (12).

[0113] like Figure 7 As shown, this invention provides longitudinal displacement curves of existing tunnels caused by the trenching process of the diaphragm wall, the concrete pouring process, and the completion of construction, respectively. Figure 7 The longitudinal displacement w(x) of the existing shield tunnel caused by the above-mentioned diaphragm wall construction process can be obtained. 地连墙施工过程隧道纵向位 shift.

[0114] In this embodiment of the invention, Matlab and [other technologies] are used for the above steps.

[0115] This invention utilizes a self-developed program written in Mathematics software. In practical applications, the method only requires obtaining the corresponding parameters and running the corresponding code to quickly determine the longitudinal displacement of existing shield tunnels caused by the diaphragm wall construction process. It requires no reliance on any simulation platform, making the method simple, efficient, and highly versatile. This invention can be applied to the calculation of longitudinal displacement in shield tunnels, and the results facilitate engineers in adjusting construction parameters to dynamically control the longitudinal displacement of existing tunnels.

[0116] This invention provides a method for calculating the longitudinal displacement of existing shield tunnels caused by diaphragm wall construction. Considering that the impact of diaphragm wall construction on adjacent tunnels is often overlooked in deep foundation pit engineering, leading to tunnel displacement, this invention divides the longitudinal displacement of the shield tunnel into a series of steps. By analyzing the stratification of the excavated soil and related mechanical parameters, as well as the relevant mechanical parameters of the existing shield tunnel's strata, the method calculates the uniformly distributed unloading caused by soil excavation during the diaphragm wall trenching process. Simultaneously, a two-dimensional coordinate system for the diaphragm wall is constructed to calculate the vertical unloading stress at the axial position of the shield tunnel. The shield tunnel is simplified as a beam, and a micro-element of the tunnel is used for stress analysis. The stress equilibrium equation and bending moment equilibrium equation of the micro-element are constructed. The established force equilibrium equations and moment equilibrium equations of the micro-element can be used to calculate the longitudinal displacement of the existing shield tunnel under the action of soil excavation during the trenching process of the diaphragm wall. At this time, the vertical additional stress at the axial position of the shield tunnel caused by the loading action during the concrete pouring process of the diaphragm wall can be calculated. Based on the established force equilibrium equations and moment equilibrium equations of the micro-element, the longitudinal displacement of the existing shield tunnel under the loading action during the concrete pouring process of the diaphragm wall can be calculated. After superimposing the longitudinal displacement of the existing shield tunnel under the action of soil excavation during the trenching process of the diaphragm wall and the longitudinal displacement of the existing shield tunnel under the loading action during the concrete pouring process of the diaphragm wall, the longitudinal displacement of the shield tunnel caused by the diaphragm wall construction process can be obtained, which is convenient for engineers to adjust construction parameters and dynamically control the longitudinal displacement of the existing tunnel.

[0117] The above description is only a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any equivalent substitutions or modifications made by those skilled in the art within the scope of the technology disclosed in the present invention, based on the technical solution and inventive concept of the present invention, should be covered within the scope of protection of the present invention.

Claims

1. A method for calculating longitudinal displacement of an existing shield tunnel caused by diaphragm wall construction, characterized by, The method comprises the following steps: Step 1: obtaining stratification of earth wall excavation soil and related mechanical parameters and stratum related mechanical parameters of the existing shield tunnel according to a geological exploration report; Step 2: calculating uniform unloading caused by soil excavation in the earth wall trenching process according to the specific gravity and average thickness of each layer of soil in the excavation part in the earth wall trenching process; Step 3: calculating vertical unloading stress at the axial position of the existing shield tunnel caused by soil excavation unloading in the earth wall trenching process; Step 4: Calculation of the longitudinal displacement of the existing shield tunnel under the action of soil excavation in the diaphragm wall trenching process w(x) 地连墙成槽开挖过程 ; Step 5: calculating vertical additional stress at the axial position of the existing shield tunnel caused by loading in the earth wall concrete pouring process; Step 6: Calculate the longitudinal displacement w(x) of the existing shield tunnel under the loading of the diaphragm wall concrete pouring process 地连墙混凝土浇筑过程 ; Step 7: calculating longitudinal displacement of the existing shield tunnel caused by the earth wall construction process by using the superposition principle; The step 3 is specifically as follows: Step 3.1: taking the center of the earth wall as the origin, a two-dimensional coordinate system of the earth wall is constructed, and the extension direction of the earth wall is taken as the κ axis and the width direction of the earth wall is taken as the λ axis; Step 3.2: taking a point in the extension direction of the existing tunnel as the origin of the tunnel coordinate system, the extension direction of the tunnel is taken as the horizontal axis x of the tunnel coordinate system, and the vertical direction of the tunnel is taken as the vertical axis y of the tunnel coordinate system; Step 3.3: the corresponding horizontal coordinate and vertical coordinate values of the coordinates of any point in the tunnel coordinate system x-y in the earth wall coordinate system κ-λ, that is, the conversion relationship of the two coordinate axes is shown in formula (2): In the formula: x, y are the coordinates of any point N in the tunnel coordinate system x-y; X, Y are the corresponding horizontal coordinate and vertical coordinate of point N in the earth wall coordinate system κ-λ; d is the horizontal distance between the origins of the two coordinate systems; the angle between the κ axis and the origin of the coordinate system is β, and the angle between the κ axis and the extension direction of the tunnel is α; Step 3.4: the distance between any point N in the extension direction of the tunnel and the earth wall can be controlled by parameters R1 and R2, and the expression is shown in formula (3): In the formula: R1 and R2 are the distances between any point N in the extension direction of the tunnel and any point on the top and bottom of the earth wall, respectively; Step 3.5: combining formula (2) and (3), the vertical unloading stress at the axial position of the existing shield tunnel caused by soil excavation unloading in the earth wall trenching process is shown in formula 4: In the formula: p(x) is the vertical unloading stress at the axial position of the existing shield tunnel caused by soil excavation unloading in the earth wall trenching process; wherein H is the buried depth of the existing tunnel, B is the width of the earth wall, and L is the extension length of the earth wall; The step 2 is specifically as follows: according to the specific gravity and thickness of each layer of soil, the uniform unloading p0 caused by soil excavation in the earth wall trenching process is calculated and accumulated, and the calculation expression is shown in formula (1): In the formula, n is the stratification number, γi and hi represent the specific gravity and thickness of each layer of soil, respectively, and h is the excavation depth of the earth wall.

2. The method of claim 1, wherein the method is characterized by: The step 1 obtains stratification of earth wall excavation soil and the specific gravity γi and average thickness hi of each layer of soil corresponding to the stratification, and obtains the base coefficient k and Poisson's ratio v of the stratum where the existing shield tunnel is located.

3. The method of claim 1, wherein the method is characterized by: The step 4 is specifically as follows: Step 4.1: the shield tunnel is simplified as a beam, and a micro-element body of the tunnel is taken for stress analysis to obtain the force balance equation and the bending moment balance equation of the micro-element body, and the expressions are shown in formula (5): where: Q and M are the shear force and bending moment on the cross section of the microelement, respectively; D is the diameter of the tunnel; p k p is the subsoil reaction force of the tunnel, and k = kw(x); Step 4.2: The deflection differential equation of the beam is shown in equation (6): Where: E and I are the elastic modulus and the cross-sectional moment of inertia of the existing tunnel, respectively; Step 4.3: The above equation (6) is substituted into equation (5) to obtain the longitudinal displacement differential expression of the existing shield tunnel under the vertical load of the soil excavation during the diaphragm wall trenching process, as shown in equation (7): Formula (7) is a fourth-order ordinary differential equation, which is solved according to Matlab and Mathematics, and the obtained tunnel longitudinal displacement expression is w(x) 地连墙成槽开挖过程 .

4. The method of claim 1, wherein the method is characterized by: The step of step 5 is specifically: Step 5.1: The original soil is replaced by concrete during the diaphragm wall concrete pouring process, and the concrete pouring process is equivalent to the loading process, and the load is uniform load q0=γ 混凝土重度 hIn the formula: γ 混凝土重度 is the concrete unit weight; Step 5.2: The corresponding horizontal and vertical coordinate values of any point in the tunnel coordinate system x-y in the diaphragm wall coordinate system κ-λ, i.e. the two coordinate axis conversion relationship is shown in equation (2); Step 5.3: The distance between any point N in the tunnel extension direction and the diaphragm wall can be controlled by parameters R1 and R2, and the expression is shown in equation (3); Step 5.4: Combined with equations (2) and (3), the vertical additional stress at the axial position of the existing shield tunnel caused by the loading during the diaphragm wall concrete pouring process is shown in equation (8): Where: q(x) is the vertical additional stress at the axial position of the existing shield tunnel caused by the loading during the diaphragm wall concrete pouring process.

5. The method of claim 4, wherein the method is characterized by: The step of step 6 is specifically: Step 6.1: The shield tunnel is simplified as a beam, and a micro-element of the tunnel is taken for stress analysis, and the expression is shown in equation (5). Replace p(x) in equation (5) with q(x) to obtain the force balance equation and the bending moment balance equation of the micro-element, as shown in equation (9); Step 6.2: The deflection differential equation of the beam is obtained, as shown in equation (10); Step 6.3: The equation (6) is substituted into equation (5) to obtain the longitudinal displacement differential expression of the existing shield tunnel under the loading during the diaphragm wall concrete pouring process, as shown in equation (11): Formula (11) is a fourth-order ordinary differential equation, which is solved according to Matlab and Mathematics, and the obtained tunnel longitudinal displacement expression is w(x) 地连墙混凝土浇筑过程 .

6. The method of claim 5, wherein the method is characterized by: The step of step 7 is specifically: by superposition principle, the longitudinal displacement of the existing shield tunnel under the action of soil excavation in the diaphragm wall trenching process and the longitudinal displacement of the existing shield tunnel caused by the loading in the concrete pouring process are superimposed, that is, the longitudinal displacement w(x) of the existing shield tunnel caused by the diaphragm wall construction process is obtained 地连墙施工过程隧道纵向位移 , and the expression is shown in formula (12): w(x) 地连墙施工过程隧道纵向位移 = w(x) 地连墙成槽开挖过程 + w(x) 地连墙混凝土浇筑过程 (12).

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