Method, system, and medium for determining support pressure for a tunnel face being excavated

Abstract

The application discloses a method for determining support pressure of a tunnel face in opposite excavation, and comprises the following steps: S1, establishing an active failure mode of a soil body of the tunnel face in opposite excavation, wherein the active failure mode comprises a logarithmic spiral wedge-shaped sliding surface failure body in front of two tunnel faces and a columnar collapse body above the two tunnel faces; S2, determining a geometric relationship of the active failure mode, and obtaining a moment balance equation of the logarithmic spiral wedge-shaped sliding surface failure body and the columnar collapse body based on a limit equilibrium method; and S3, reversely deducing and calculating a critical support force P of the tunnel face in opposite excavation according to the moment balance equation. The active failure mode and the critical support force P obtained by calculation are reliable and reasonable.

Description

Technical Field

[0001] This invention relates to the field of tunnel support and safety evaluation, and in particular to a method, system and medium for determining the support pressure at the tunnel face in counter-excavation. Background Technology

[0002] In tunnel excavation, the opposing excavation method, with its high-efficiency construction advantages, has been widely used. However, when the distance between the two tunnel faces in opposing excavation is less than a certain critical value, the tunnel faces formed by the two opposing excavations will disturb each other, resulting in a double disturbance zone in front of the tunnel faces. To avoid the formation of a double disturbance zone in front of the tunnel faces in opposing excavation, relevant specifications stipulate that the minimum distance between the tunnel faces in opposing excavation should not be less than several tens of times the tunnel diameter. However, many studies have shown that the critical distance between the tunnel faces in opposing excavation specified in the specifications is too large. In the later stages of opposing excavation, the construction process is prematurely adjusted from opposing excavation to unidirectional construction, resulting in slower construction progress and excessively long construction periods. Reasonable support pressure plays an important role in the stability control of the tunnel faces in opposing excavation, but existing technologies do not provide reasonable support pressure specifically for the stability problem of the tunnel faces in opposing excavation. For the reasons mentioned above, it is urgent to provide a reasonable support pressure to address the stability issue of the tunnel face in counter-excavation, so as to ensure the stability of the tunnel face under dual disturbances.

[0003] Numerical simulation is a more efficient, economical, and repeatable method. Therefore, it is widely used in studies of tunnel surrounding rock failure and support pressure. Existing numerical simulation methods mainly include: 1) the finite element method; 2) the finite difference method; and 3) the discrete element method. Among numerical simulation methods, FLAC3D simulation software belongs to the finite difference method, which can well solve large deformation problems in soil and rock, and avoids iterative calculations, making it a highly efficient and applicable numerical simulation software. Existing technologies and research results are all based on the stability problems of the roof, surrounding rock, or tunnel face of unidirectional excavation tunnels. For example, invention patent application number 202110865062.9 discloses a method for determining the surrounding rock pressure of tunnels with unequal spans buried in deep rock strata; invention patent application number 202110865061.4 discloses a method for determining the surrounding rock pressure of tunnels with unequal spans buried in deep soil strata; invention patent application number 201810108562.6 discloses a method for determining the surrounding rock pressure of shallowly buried tunnels with small clearances in composite strata; invention patent application number 202011503860.9 discloses a method for calculating the surrounding rock pressure of shallowly buried tunnels under secondary failure modes; and invention patent application number 202111518823.X discloses a method for analyzing the stability of tunnel excavation faces under seismic load conditions. The aforementioned disclosed invention patents only address the stability of the surrounding rock and tunnel face in unidirectional excavation tunnels, disclosing some failure modes. However, they do not address the failure modes and support pressure technology for the stability of tunnel faces in counter-excavation tunnels, and are therefore not applicable to the stability research of tunnel faces in counter-excavation tunnels. This is because unidirectional excavation stability research addresses the stability of tunnel faces under single excavation disturbance conditions. It establishes tunnel face failure modes considering a single disturbance factor and further studies the minimum safe support force under corresponding conditions. Compared to unidirectional excavation, a significant problem with counter-excavation is that the tunnel face soil and rock may face dual disturbances caused by simultaneous excavation from both left and right faces. The support pressure calculation results obtained from unidirectional excavation stability research are unreliable. To avoid the potential dual disturbance effects on counter-excavation tunnel faces, existing technologies primarily increase the safety distance between counter-excavation tunnel faces. However, currently, the direct basis for increasing the safety distance between counter-excavation tunnel faces is mainly determined through field experience or semi-empirical theory. If the safety distance between the excavation faces in opposite directions, determined by existing experience or semi-empirical theory, is too large, it will prolong the construction period, increase construction costs, and reduce construction efficiency. Summary of the Invention

[0004] The technical problem to be solved by the present invention is to overcome the shortcomings of the prior art and provide a method, system and medium for determining the support pressure at the face of a tunnel in opposite excavation with reasonable and reliable calculation results.

[0005] To solve the above-mentioned technical problems, the present invention adopts the following technical solution:

[0006] A method for determining the support pressure at the tunnel face in counter-excavation includes the following steps:

[0007] S1. Establish an active failure mode for the soil at the tunnel face of opposing excavation, wherein the active failure mode includes a logarithmic spiral wedge-shaped slip surface failure body in front of the two tunnel faces and a columnar collapse body above the two tunnel faces.

[0008] S2. Determine the geometric relationship of the active failure mode, and obtain the moment balance equations of the logarithmic spiral wedge slip surface failure body and the columnar collapse body based on the limit equilibrium method;

[0009] S3. The critical support force P of the tunnel face in opposite excavation is calculated by reverse derivation based on the moment balance equation.

[0010] As a further improvement to the above technical solution:

[0011] In step S2, the torque balance equation is shown in equation (1).

[0012]

[0013] In the above formula, M WO For the gravitational moment of the logarithmic spiral wedge-shaped slip surface failure body, M σv The load σ acting on the logarithmic spiral wedge-shaped slip surface failure body from the columnar collapse body. v The torque generated, M PwO The torque M of groundwater about the rotation center O within the active failure mode range. PO M is the torque of the uniform support force P acting on the tunnel face about the center of rotation O. RO The torque of the tangential force on the logarithmic spiral wedge-shaped slip surface failure body about the rotation center O.

[0014] The critical support force P at the tunnel face of the opposing excavation is shown in equation (2):

[0015]

[0016] γ is the unit weight of soil, σ v γ is the gravity of the columnar fractured body, c is the cohesive force, and γ is the gravitational force. w The density of water,

[0017]

[0018] r0 is the initial radius of the logarithmic spiral slip surface of the logarithmic spiral wedge-shaped slip surface failure body. θ is the angle of rotation around the center of rotation O from the initial radius r0, L is the horizontal distance between the two tunnel faces, α is the angle between the initial radius r0 and the final radius, δ is the auxiliary angle for calculating the area of ​​the logarithmic spiral wedge slip surface failure, and D is the tunnel diameter. The angle between the initial radius r0 and the horizontal line.

[0019]

[0020]

[0021]

[0022]

[0023]

[0024] l OE It is the horizontal distance between the tunnel face and the rotation center O.

[0025] Preferably, M is obtained using equation (3). WO :

[0026] M WO =M WO1 +M WO2 (3)

[0027] In equation (3), the logarithmic spiral wedge-shaped slip surface failure body includes a first failure body and a second failure body, M WO1 M is the gravitational torque of the first failing body. WO2 The gravitational torque of the second destructive body;

[0028] M is obtained using equation (4) σvO :

[0029]

[0030] M is obtained using equation (5) PO :

[0031]

[0032] M is obtained using equation (6) RO :

[0033]

[0034] Using equation (7) to obtain

[0035]

[0036] In the aforementioned formula (3), The included angle β is the angle between the tangent direction of the rotational failure surface of the soil strip and the horizontal direction when the first failure body is divided into multiple soil strips.

[0037] In the above formula (4),

[0038] Preferably, equation (7) is obtained by the following steps:

[0039] A1. Based on the pore water pressure P generated on the sliding surface of the micro-soil strips in the sliding body. θ An integral equation as shown in equation (17) is established, and the pore water pressure P generated by the entire sliding surface as shown in equation (18) is derived and calculated. w equation:

[0040]

[0041]

[0042] A2. Based on the pore water pressure P w An integral equation as shown in equation (20) is established, and the pore water pressure P shown in equation (7) is derived and calculated. w The torque generated about the center of rotation O

[0043]

[0044] Preferably, after step S3, the method further includes numerical simulation analysis using numerical simulation methods to obtain numerical simulation results. The numerical simulation results are then compared with the support force P calculated in step S3. If the comparison results are within the error range, the active failure mode and critical support force P are deemed reasonable; otherwise, they are deemed unreasonable.

[0045] As a general inventive concept, the present invention provides a system for determining the support pressure at the tunnel face in counter-excavation, comprising the following modules:

[0046] The first modeling module is used to establish an active failure mode of the soil at the tunnel face of the opposing excavation. The active failure mode includes a logarithmic spiral wedge-shaped slip surface failure body in front of the two tunnel faces and a columnar collapse body above the two tunnel faces.

[0047] The second modeling module is used to determine the geometric relationships of the active failure mode and obtains the moment balance equations of the logarithmic spiral wedge slip surface failure body and the columnar collapse body based on the limit equilibrium method.

[0048] The third calculation module is used to derive and calculate the critical support force P of the tunnel face in opposite directions based on the torque balance equation.

[0049] As a general inventive concept, the present invention also provides a computer-readable medium storing a computer program programmed or configured to perform the aforementioned method for determining the support pressure at the face of a counter-excavation tunnel.

[0050] Compared with the prior art, the advantages of the present invention are as follows:

[0051] This invention constructs an active failure mode for the soil at the tunnel face in counter-excavation. This active failure mode includes a logarithmic spiral wedge-shaped slip surface failure body in front of both tunnel faces and a columnar collapse body above and in front of both tunnel faces. A theoretical model of the critical support pressure at the tunnel face under this failure mode is derived, and the critical support pressure is obtained. Numerical simulation is used to obtain the numerical simulation failure mode and critical support force of the tunnel face in counter-excavation, verifying the rationality of the theoretical model of the active failure mode in analyzing the stability of the tunnel face. The verification results show that the model is reasonable for analyzing the stability of the tunnel face considering counter-excavation, and the support pressure results are reliable while ensuring the construction period. Attached Figure Description

[0052] Figure 1 This is a diagram of the failure mode of the tunnel face in an opposing excavation, provided in an embodiment of the present invention.

[0053] Figure 2 This is a mechanical analysis diagram of the wedge-shaped rotational failure region provided in an embodiment of the present invention.

[0054] Figure 3 This is a Bishop method soil strip mechanical analysis diagram of the wedge-shaped rotational failure zone provided in an embodiment of the present invention.

[0055] Figure 4 This is a schematic diagram of the numerical model provided in an embodiment of the present invention.

[0056] Figure 5 This is a cloud map of soil displacement at the tunnel face when the distance L between the tunnel faces in opposite excavation is 60m, 50m, 40m, 30m, 20m and 10m, provided in an embodiment of the present invention.

[0057] Figure 6 This is a curve showing the change of the soil displacement along the tunnel axial direction with the distance between the tunnel faces, provided in an embodiment of the present invention.

[0058] Figure 7 This is a comparison chart of the boundary support force of the tunnel face in an opposing excavation according to an embodiment of the present invention and the numerical simulation results. Detailed Implementation

[0059] The present invention will be further described in detail below. Unless otherwise specified, the instruments or materials used in the present invention are commercially available.

[0060] Example 1:

[0061] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to embodiments. Addressing the problems existing in the prior art, this invention provides an active failure mode of the tunnel face in counter-excavation and a method for determining the support pressure. The invention will be described in detail below with reference to the accompanying drawings.

[0062] like Figure 1 As shown in the embodiment of the present invention, a method for determining the support pressure at the face of a tunnel excavated in opposite directions is provided. The steps of implementing this method include: (1) constructing the failure mode of the tunnel face in opposite directions → (2) determining the geometric relationship of the failure mode → (3) establishing the moment balance equation of the failure mode based on the limit equilibrium method → ​​(4) deriving the theoretical model of the support pressure at the face of a tunnel excavated in opposite directions → (5) verifying the failure mode and support pressure theory at the face of a tunnel excavated in opposite directions using the FLAC3D numerical simulation method. Specifically, the method includes the following steps:

[0063] S1. Establish an active failure mode for the soil at the tunnel face of opposing excavation, wherein the active failure mode includes a logarithmic spiral wedge-shaped slip surface failure body in front of the two tunnel faces and a columnar collapse body above the two tunnel faces.

[0064] Constructing a failure mode for the tunnel face in opposing excavations: This invention first establishes an active failure mode for the soil at the tunnel face in opposing excavations. Active failure occurs when the support pressure applied to the tunnel face is less than the soil pressure at the face, causing the soil within a certain range in front of the face to collapse and fail into the tunnel. Assuming the strata are homogeneous soil, the surface is completely horizontal, there is no additional load on the surface, and the influence of groundwater is considered, the failure range of the tunnel face extends to the surface. Assuming the tunnel depth is C, the tunnel diameter is D, the horizontal distance between the two tunnel faces is L, and the uniform support force applied to the tunnel faces is P, for simplicity, the stability problem of the tunnel face in opposing excavations is assumed to be a two-dimensional planar model. Considering that the entire model is symmetrical, only the left half is used as an example for explanation. As the distance between the two tunnel faces in opposing excavations continuously decreases, a wedge-shaped failure body with a logarithmic spiral slip surface forms in front of the two tunnel faces. This wedge-shaped failure body with a logarithmic spiral slip surface undergoes rotational failure around its rotation center O. Under the dual disturbance effect of opposing excavation, a dual disturbance region forms above the two tunnel faces. The outline of this dual disturbance region approximates a column, and the columnar failure body undergoes vertical downward deformation failure under its own gravity. Therefore, the active failure mode of opposing excavation tunnel faces provided by this invention includes the logarithmic spiral wedge-shaped slip surface failure body in front of the two tunnel faces and the columnar collapse body above the two tunnel faces, such as... Figure 1 As shown.

[0065] S2. Determine the geometric relationship of the active failure mode, and obtain the moment balance equations of the logarithmic spiral wedge slip surface failure body and the columnar collapse body based on the limit equilibrium method;

[0066] Based on the soil disturbance characteristics in front of the tunnel faces of two opposing excavated tunnels, it is assumed that mutual disturbance will occur when the distance between the tunnel faces is L. A wedge-shaped failure body EGF with a logarithmic spiral failure surface is established directly in front of the tunnel faces, undergoing rotational failure around the rotation center O. The soil above the tunnel faces is a columnar failure body, failing vertically downwards under its own weight. The wedge-shaped failure body EGF is subjected to its own weight W, the tunnel face support force P, and the weight σ of the columnar failure body above it. v The shear force T and normal force N on the logarithmic helix surface. The cylindrical failure body EFHI is acted upon by its own gravity σ. v Furthermore, this invention takes into account the pore water pressure P. w The impact.

[0067] The specific soil parameters and geometric parameters of the failure mode in this embodiment are shown in Table 1.

[0068] Table 1. Soil and geometric parameters of the opposing excavation tunnel.

[0069]

[0070]

[0071] Determine the geometric relationships of the failure modes: such as Figure 2 As shown, a wedge-shaped failure body (i.e., a logarithmic spiral wedge-shaped slip surface failure body) on the logarithmic spiral slip surface in front of the tunnel face undergoes rotational slip instability failure around a rotation center O along the logarithmic spiral slip surface. The wedge-shaped failure body is EGF, where EG is exactly the radius of the tunnel face. The horizontal distance between points E and F is half the distance between the two tunnel faces, i.e., L / 2. The horizontal distance from the left tunnel face to the rotation center O is l. OE .

[0072] In the constructed failure mode, the logarithmic spiral equation of the logarithmic spiral wedge-shaped slip surface failure body in front of the tunnel face can be expressed as:

[0073]

[0074] Where r is the radius of the logarithmic spiral at the rotation angle θ, and r0 is the initial radius of the logarithmic spiral slip surface. The angle between the initial radius r0 and the horizontal line is also the internal friction angle of the soil.

[0075] Based on the geometric characteristics of the constructed failure mode of the tunnel face in counter-excavation, the initial radius r0 of the logarithmic spiral slip surface and the horizontal distance l between the tunnel face and the rotation center O can be obtained. OE The expression for the distance L between the two working faces of a tunnel excavated in opposite directions is as follows:

[0076]

[0077] Where α is the angle between the initial radius and the final radius of the logarithmic spiral failure surface, and δ is the auxiliary angle for calculating the area of ​​the logarithmic spiral failure body.

[0078]

[0079]

[0080] The moment balance equation for the failure mode is established based on the limit equilibrium method: According to the limit equilibrium theory, the moment of the failure mode of the opposing excavation tunnel face provided by this invention includes the moment M of gravity of the logarithmic spiral failure body about the rotational neutrality. WO The load σ acting on the helical failure body by the columnar failure body v The generated torque M σv The torque of groundwater about the rotation center O within the failure mode range The moment M of the uniform support force P acting on the tunnel face about the center of rotation PO And the torque M of the tangential force on the logarithmic spiral failure surface of the logarithmic spiral failure body about the center of rotation O. RO The principle for calculating torque is to multiply the force acting on the breaking block by the distance from the line of action of that force to the center of rotation. According to the theory of limit equilibrium, the above torques have the following relationship:

[0081]

[0082] S3. The critical support force P of the tunnel face in opposite directions is calculated by reverse derivation based on the moment balance equation. This step is to derive the theoretical model of the support pressure of the tunnel face in opposite directions: according to step (3), the moment of each part is calculated respectively.

[0083] 1) Gravitational moment M of the rotating failure region (wedge-shaped failure body region) wO

[0084] The wedge-shaped failure body EGF consists of two parts: the EJF block and the GJF block. (These two blocks are used to simplify calculations; they are not related to the actual failure mode and are only for computational convenience.) Figure 1 The JF line in the diagram is a calculation auxiliary line.

[0085] For the GJF block, its gravitational moment is calculated using the Bishop soil strip method. First, the rotating failure block of the GJF at the working face is divided into n equally spaced micro-soil strips with very small widths. The angle between the tangent direction of the rotating failure surface of the soil strip and the horizontal direction is β.

[0086]

[0087] Therefore, the gravitational torque of the GJF block is:

[0088]

[0089] in:

[0090]

[0091] The gravitational moment of the EJF block can be directly calculated using geometric relationships, and its gravitational moment can be expressed as:

[0092]

[0093] in:

[0094]

[0095] The gravitational moment of the wedge-shaped failure body EGF is the sum of the gravitational moments of the EJF block and the GJF block, expressed as follows:

[0096] M WO =M WO1 +M WO2 (11)

[0097] 2) The gravitational moment of the columnar failure region (columnar failure body),

[0098] Based on geometric relationships, the gravity of this part is first calculated as follows:

[0099]

[0100] The torque of this part of the gravity about the center of rotation O is the weight of this part multiplied by its lever arm. Therefore, the torque of this part can be expressed as:

[0101]

[0102] 3) Supporting moment, M PO

[0103]

[0104] 4) The resisting torque M on the rotating failure surface of a rotating failure body (i.e., a wedge-shaped failure body). RO

[0105]

[0106] 5) Pore water pressure torque,

[0107] The pore water pressure generated at the micro-soil strip sliding surface in the wedge-shaped failure body is:

[0108]

[0109] The pore water pressure generated across the entire sliding surface is:

[0110]

[0111]

[0112]

[0113] The torque generated by the pore water pressure about the center of rotation O is:

[0114]

[0115]

[0116] 6) The boundary support pressure P at the tunnel face

[0117] Substituting equations (11), (13), (14), (15), and (21) into equation (5), the theoretical model of the boundary support pressure P at the tunnel face can be derived as follows:

[0118]

[0119]

[0120] S4. The FLAC3D numerical simulation software was used for simulation verification, including the establishment of the failure mode of the tunnel face in the opposite excavation and the verification of the critical support force.

[0121] This invention proposes a method for determining the support pressure at the tunnel face in counter-excavation tunnels. First, a failure mode for the tunnel face in counter-excavation is constructed, and the corresponding theoretical model of the face's critical support pressure is derived based on the limit equilibrium method. The rationality of the proposed failure mode and the theoretical model of the face's critical support pressure needs further verification. The verification process is as follows: To verify the rationality of the proposed failure mode and the correctness of the theoretical model, the results obtained from the failure mode and the theoretical model of the face support force are compared with the numerical simulation results. The numerical simulation software used is FLAC3D, and a series of numerical analyses were performed using a finite difference calculation program to calculate the ultimate support pressure at different distances from the tunnel face in counter-excavation and to determine the tunnel face failure mode.

[0122] The following simulation verification was performed using FLAC3D numerical simulation software, including the establishment of the failure mode and critical support force of the tunnel face in the opposite excavation:

[0123] The failure modes and critical support forces of a counter-excavation tunnel face at different spacings were simulated using FLAC3D numerical simulation software. The tunnel profile was formed by a single, full-section excavation in the simulation. To avoid the impact of boundary effects on simulation accuracy, the model was set sufficiently large; the established two-dimensional planar numerical model is shown below. Figure 4 The numerical simulation used a model with a length of 80m, a thickness of 1m, and a height of 50m. The mesh was divided into blocks; when the distance between the tunnel faces in opposite excavations was 60m, the entire model consisted of 16,000 elements, including 32,522 element nodes. The top of the model was a free surface, the vertical surfaces on both sides were fixed horizontally but could deform freely vertically, and the bottom of the model was completely fixed. In the simulation, it was assumed that the soil obeyed the Mohr-Coulomb failure criterion, the soil was cohesive-free, and the influence of additional loads was ignored, i.e., the cohesion c was 0. Specific parameter values ​​during the simulation are shown in Table 1. The static horizontal plane in the model was at the same height as the top of the model, and it was assumed that no seepage occurred in the tunnel surrounding rock, only at the tunnel face.

[0124] To comprehensively verify the failure modes and critical support pressures under different spacing conditions of the tunnel faces in opposing excavations, the spacing between the tunnel faces in the first simulation was 60m. In subsequent simulations, the spacing was gradually reduced by 10m each time, with a minimum of 10m. After tunnel excavation, the inner surface soil was promptly supported by applying surface stress instead of lining support. Subsequently, a support force P perpendicular to the tunnel face was applied, calculated according to γ×H×K (where K is the pressure coefficient). The initial support force of the tunnel face is applied. To obtain the critical support force of the tunnel face, the stress control method is used to gradually reduce the support force. The stress control method gradually reduces the applied support force of the tunnel face until the soil at the tunnel face still undergoes significant deformation when the applied support force remains unchanged. This state of support force can be considered the critical support force of the tunnel face. By simulating the failure of the tunnel face with spacing of 60m, 50m, 40m, 30m, 20m, and 10m, the displacement contour maps of the tunnel face can be obtained. Figure 5 .in Figure 5 (a) to Figure 5 (f) are 60m to 10m respectively.

[0125] The relationship between the tunnel face support force and the horizontal displacement of the center point of the tunnel face is shown in the figure. Figure 6 Comparing the failure mode of the tunnel face in opposing excavation provided by this invention with the displacement cloud map obtained from FLAC3D numerical simulation, it was found that when the distance between the tunnel faces is less than 30m, the failure mode provided by this invention is very close to the numerical simulation results. This indicates that the failure mode of the tunnel face in opposing excavation provided by this invention can reflect the failure characteristics when the distance between the tunnel faces in opposing excavation is small and they influence each other. Therefore, the failure mode of the tunnel face in opposing excavation provided by this invention is reasonable.

[0126] Furthermore, the theoretical model solution of the support pressure at the tunnel face in counter-excavation provided by this invention is compared with the boundary support pressure at the tunnel face determined by numerical simulation. The results are shown in […]. Figure 7 Comparative analysis revealed that when the distance between the tunnel faces in opposite excavations was 60m, 50m, 40m, 30m, 20m, and 10m, the theoretical model solution for the support pressure at the tunnel face provided by this invention was basically consistent with the boundary support pressure determined by numerical simulation. The comparative results demonstrate that the theoretical model for the support pressure at the tunnel face in opposite excavations provided by this invention is reliable.

[0127] The present invention also provides a system for determining the support pressure at the tunnel face in counter-excavation, comprising the following modules:

[0128] The first modeling module is used to establish an active failure mode of the soil at the tunnel face of the opposing excavation. The active failure mode includes a logarithmic spiral wedge-shaped slip surface failure body in front of the two tunnel faces and a columnar collapse body above the two tunnel faces.

[0129] The second modeling module is used to determine the geometric relationships of the active failure mode and obtains the moment balance equations of the logarithmic spiral wedge slip surface failure body and the columnar collapse body based on the limit equilibrium method.

[0130] The third calculation module is used to derive and calculate the critical support force P of the tunnel face in opposite excavation based on the torque balance equation.

[0131] As a general inventive concept, the present invention also provides a system for determining the support pressure at the face of a counter-excavating tunnel, including a microprocessor and a memory interconnected thereto, the microprocessor being programmed or configured to perform the steps of the method for determining the support pressure at the face of a counter-excavating tunnel.

[0132] As a general inventive concept, the present invention also provides a computer-readable medium storing a computer program programmed or configured to perform the method for determining the support pressure at the face of a counter-excavation tunnel.

[0133] Those skilled in the art will understand that embodiments of this application can be provided as methods, systems, or computer program products. Therefore, this application can take the form of a completely hardware embodiment, a completely software embodiment, or an embodiment combining software and hardware aspects. Furthermore, this application can take the form of a computer program product embodied on one or more computer-readable storage media (including, but not limited to, disk storage, CD-ROM, optical storage, etc.) containing computer-usable program code. This application is described with reference to flowchart illustrations and / or block diagrams of methods, apparatus (systems), and computer program products according to embodiments of this application. It will be understood that each block of the flowchart illustrations and / or block diagrams, and combinations of blocks in the flowchart illustrations and / or block diagrams, can be implemented by computer program instructions. These computer program instructions can be provided to a processor of a general-purpose computer, special-purpose computer, embedded processor, or other programmable data processing apparatus to produce a machine, such that the instructions, which execute via the processor of the computer or other programmable data processing apparatus, create a machine for implementing the process. Figure 1 One or more processes and / or boxes Figure 1 The computer program instructions may also be stored in a computer-readable storage medium that can direct a computer or other programmable data processing device to operate in a particular manner, such that the instructions stored in the computer-readable storage medium produce an article of manufacture including instruction means, which are implemented in a process Figure 1 One or more processes and / or boxes Figure 1 The functions specified in one or more boxes. These computer program instructions may also be loaded onto a computer or other programmable data processing apparatus to cause a series of operational steps to be performed on the computer or other programmable apparatus to produce a computer-implemented process, thereby providing instructions that execute on the computer or other programmable apparatus for implementing the process. Figure 1 One or more processes and / or boxes Figure 1The steps of the function specified in one or more boxes.

[0134] While the present invention has been disclosed above with reference to preferred embodiments, it is not intended to limit the invention. Any person skilled in the art can make many possible variations and modifications to the technical solutions of the present invention, or modify them into equivalent embodiments, without departing from the scope of the present invention. Therefore, any simple modifications, equivalent changes, and modifications made to the above embodiments based on the technical essence of the present invention, without departing from the scope of the present invention, should fall within the protection scope of the present invention.

Claims

1. A method for determining the support pressure at the tunnel face in counter-excavation, characterized in that: Includes the following steps: S1. Establish an active failure mode for the soil at the tunnel face of opposing excavation, wherein the active failure mode includes a logarithmic spiral wedge-shaped slip surface failure body in front of the two tunnel faces and a columnar collapse body above the two tunnel faces. S2. Determine the geometric relationship of the active failure mode, and obtain the moment balance equations of the logarithmic spiral wedge slip surface failure body and the columnar collapse body based on the limit equilibrium method; S3. The critical support force P at the tunnel face of the opposite excavation is calculated by reverse derivation based on the moment balance equation. In step S2, the torque balance equation is shown in equation (1). （1） In the above formula, For the gravitational moment of the logarithmic spiral wedge-shaped slip surface failure body, Loads acting on a columnar collapse body on a logarithmic spiral wedge-shaped slip surface failure body The generated torque The torque of groundwater about the rotation center O within the active failure mode range, Let P be the torque of the uniform support force P acting on the tunnel face about the center of rotation O. The torque of the tangential force on the logarithmic spiral failure surface of the logarithmic spiral wedge-shaped slip surface failure body about the rotation center O; The critical support force P at the tunnel face of the opposing excavation is shown in equation (2): （2） γ is the unit weight of soil. Let γ be the weight of the columnar failure body, c be the cohesive force, and γw be the specific weight of water. , , , , Let R be the initial radius of the logarithmic spiral slip surface of the logarithmic spiral wedge slip surface failure body. , Starting radius The angle of rotation around the center of rotation O, L is the horizontal distance between the two tunnel faces, and α is the initial radius. The angle between the endpoint and the terminal radius, δ is the auxiliary angle for calculating the area of ​​the failed body of the logarithmic spiral wedge slip surface, and D is the tunnel diameter. Starting radius The angle between the horizontal line and the horizontal line, It is the horizontal distance between the tunnel face and the rotation center O.

2. The method for determining the support pressure at the tunnel face in counter-excavation according to claim 1, characterized in that: Using equation (3) to obtain : （3） In equation (3), the logarithmic spiral wedge-shaped slip surface failure body includes a first failure body and a second failure body. The gravitational torque of the first failing body. The gravitational torque of the second destructive body; Using equation (4) to obtain : （4） Using equation (5) to obtain : （5） Using equation (6) to obtain : （6） Using equation (7) to obtain : （7）。 3. The method for determining the support pressure at the tunnel face in counter-excavation according to claim 2, characterized in that: In the aforementioned formula (3), , The included angle The angle between the tangent direction of the rotational failure surface of the soil strip and the horizontal direction when the first failure body is divided into multiple soil strips.

4. The method for determining the support pressure at the tunnel face in counter-excavation according to claim 3, characterized in that: In the aforementioned formula (4), , C This refers to the tunnel's burial depth.

5. The method for determining the support pressure at the tunnel face in counter-excavation according to claim 4, characterized in that: Equation (7) is obtained by the following steps: A1. Based on the pore water pressure generated on the sliding surface of the micro-soil strips in the sliding body. An integral equation as shown in equation (17) is established, and the pore water pressure generated by the entire sliding surface as shown in equation (18) is derived and calculated. equation: (17) (18) To the starting radius r The radius of the logarithmic spiral slip surface when 0 is at an angle θ; A2. Based on pore water pressure An integral equation as shown in equation (20) is established, and the pore water pressure as shown in equation (7) is derived and calculated. The torque generated about the center of rotation O ; (20)。 6. The method for determining the support pressure at the tunnel face in counter-excavation according to claim 5, characterized in that: After step S3, the method further includes numerical simulation analysis using numerical simulation methods to obtain numerical simulation results. The numerical simulation results are then compared with the support force P calculated in step S3. If the comparison results are within the error range, the active failure mode and critical support force P are determined to be reasonable; otherwise, they are deemed unreasonable.

7. A system for determining the support pressure at the face of a tunnel in opposite directions, used to execute the method for determining the support pressure at the face of a tunnel in opposite directions as described in any one of claims 1 to 6, characterized in that: Includes the following modules: The first modeling module is used to establish an active failure mode of the soil at the tunnel face of the opposing excavation. The active failure mode includes a logarithmic spiral wedge-shaped slip surface failure body in front of the two tunnel faces and a columnar collapse body above the two tunnel faces. The second modeling module is used to determine the geometric relationships of the active failure mode and obtains the moment balance equations of the logarithmic spiral wedge slip surface failure body and the columnar collapse body based on the limit equilibrium method. The third calculation module is used to derive and calculate the critical support force P of the tunnel face in opposite directions based on the torque balance equation.

8. A computer-readable medium, characterized in that: The computer-readable storage medium stores a computer program that is programmed or configured to perform the method for determining the support pressure at the face of an opposing excavation tunnel as described in any one of claims 1 to 6.

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