A 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 semi-elliptical collapse body above and in front of the two tunnel faces; S2, obtaining a moment balance equation of the logarithmic spiral wedge-shaped sliding surface failure body and the semi-elliptical collapse body based on a limit equilibrium method; and S3, reversely deducing 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] The present application relates to the field of tunnel support and safety evaluation, and particularly relates to a method and system for determining support pressure of a tunnel face of opposite excavation and a medium. BACKGROUND

[0002] In the process of tunnel excavation, the opposite excavation method with high efficient construction has been widely applied. However, when the distance between the two tunnel faces of opposite excavation is less than a certain critical value, the two tunnel faces of opposite excavation will disturb each other, resulting in a double disturbance zone in front of the tunnel faces. In order to avoid the formation of a double disturbance zone in front of the tunnel faces of opposite excavation, the relevant specifications stipulate that the minimum distance between the two tunnel faces of opposite excavation should not be less than several tens of times of the diameter of the tunnel. However, many research results show that the critical distance between the two tunnel faces of opposite excavation stipulated by the specifications is too large. In the later stage of the opposite excavation tunnel, the opposite excavation construction technology is adjusted to a one-way construction technology too early, resulting in a slow construction progress and a long construction period. A reasonable support pressure plays an important role in the stability control of the tunnel face of opposite excavation, but the existing technology does not provide a reasonable support pressure for the stability problem of the tunnel face of opposite excavation. Based on the above reasons, it is urgent to give a reasonable support pressure for the stability problem of the tunnel face of opposite excavation, to ensure the stability of the tunnel face of opposite excavation under the action of double disturbance.

[0003] Numerical simulation is a more efficient, economical and repeatable method. Therefore, it is widely used in the study of tunnel surrounding rock damage and support pressure. The existing numerical simulation methods mainly include: 1) finite element method; 2) finite difference method; 3) discrete element method. Among the numerical simulation methods, the FLAC3D simulation software belongs to the finite difference method, which can well solve the problem of large deformation of rock and soil, and avoid iterative calculation, and is a high-efficiency and applicable numerical simulation software. The existing technologies and research results are all based on the stability of the tunnel roof, surrounding rock or working face in one-way excavation, such as the invention patent with the application number 202110865062.9 discloses a method for determining the surrounding rock pressure of a deep-buried unequal-span tunnel in rock stratum; the invention patent with the application number 202110865061.4 discloses a method for determining the surrounding rock pressure of a deep-buried unequal-span tunnel in soil stratum; the invention patent with the application number 201810108562.6 discloses a method for determining the surrounding rock pressure of a shallow-buried small-clearance tunnel in composite stratum; the invention patent with the application number 202011503860.9 discloses a method for calculating the surrounding rock pressure of a shallow-buried tunnel under secondary damage mode; and the invention patent with the application number 202111518823.X discloses a method for analyzing the stability of a tunnel excavation face under seismic load. The above-mentioned invention patents only aim at the stability of the tunnel surrounding rock and working face in one-way excavation, disclose some damage modes, but are not directed to the damage mode and support pressure of the working face in counter-excavation tunnel, and are not applicable to the stability research of the working face in counter-excavation tunnel. The reason is that the stability research in one-way excavation is directed to the stability of the tunnel working face under single excavation disturbance, and is based on the establishment of the tunnel working face damage mode under single disturbance factor and the further research on the minimum safety support force under the corresponding condition. Compared with one-way excavation, the significant problem of counter-excavation is that the working face of rock and soil may face double disturbance caused by the simultaneous excavation of the left and right working faces. The support pressure calculation result obtained by the stability research in one-way excavation is not reliable. In order to avoid the influence of the double disturbance on the working face in counter-excavation, the existing technology mainly avoids the influence of double disturbance by increasing the safety distance between the working faces in counter-excavation. However, the direct basis for increasing the safety distance between the working faces in counter-excavation at present is mainly determined by field experience or semi-empirical theory. The safety distance between the working faces in counter-excavation determined according to the existing experience or semi-empirical theory is too large, which prolongs the construction period, increases the construction cost and reduces the construction efficiency. SUMMARY

[0004] The technical problem to be solved by the present application is to overcome the shortcomings of the prior art and provide a counter-excavation tunnel working face support pressure determination method, system and medium with reasonable and reliable support pressure calculation result.

[0005] To solve the above technical problems, the present application adopts the following technical solutions:

[0006] A method for determining the support pressure of a tunnel face in opposite excavation, comprising the following steps:

[0007] S1, establishing an active failure mode of the soil mass of the tunnel face in opposite excavation, the active failure mode comprising a logarithmic spiral wedge-shaped sliding surface failure body in front of the two tunnel faces and a semi-elliptical collapse body above the two tunnel faces;

[0008] S2, determining the geometric relationship of the active failure mode, and obtaining the moment balance equation of the logarithmic spiral wedge-shaped sliding surface failure body and the semi-elliptical collapse body based on the limit equilibrium method:

[0009] S3, reversely deducing and calculating the critical support force P of the tunnel face in opposite excavation according to the moment balance equation.

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

[0011] Preferably, in the step S2, the moment balance equation is shown as formula (1):

[0012]

[0013] Wherein, M wO is the gravity moment of the gravity of the logarithmic spiral wedge-shaped sliding surface failure body in front of the two tunnel faces to the rotation center O point, is the uniform load σ v of the gravity of the semi-elliptical collapse body above the two tunnel faces to the rotation center O point, M PO is the support moment of the uniform support force P of the tunnel face to the rotation center O point, M RO is the impedance moment on the logarithmic spiral sliding surface of the logarithmic spiral wedge-shaped sliding surface failure body.

[0014] Preferably, the critical support force P of the tunnel face in opposite excavation is shown as formula (2):

[0015]

[0016] In the above formula, γ is the unit weight of the soil mass, σ v is the distributed force of the gravity of the semi-elliptical collapse body above the two tunnel faces to the logarithmic spiral wedge-shaped sliding surface failure body, c is the cohesion, r0 is the starting radius of the sliding surface of the logarithmic spiral wedge-shaped sliding surface failure body, θ is the angle of the starting radius r0 rotating around the rotation center O, and D is the tunnel radius of the tunnel in opposite excavation, is the angle between the initial radius r0 and the horizontal line, L is the distance between the two tunnel faces, and a is the angle between the initial radius r0 and the final radius r of the slip surface of the log-spiral wedge-shaped slip failure body α

[0017]

[0018]

[0019] Preferably, in the step S2, the gravity moment M of the log-spiral wedge-shaped slip failure body itself in front of the two tunnel faces with respect to the rotation center O is obtained by using formula (3) wO

[0020]

[0021] The uniformly distributed load σ of the log-spiral wedge-shaped slip failure body generated by the gravity of the semi-elliptical collapse body above the two tunnel faces is obtained by using formula (4) v The moment of the force with respect to the rotation center O

[0022]

[0023] The support moment M of the rotation center O generated by the support force P on the tunnel face is obtained by using formula (5) PO

[0024]

[0025] The resistance moment M of the log-spiral slip surface of the wedge-shaped slip failure body is obtained by using formula (6) RO

[0026]

[0027] Preferably, the formula (3) is obtained by using the following steps:

[0028] A1, the wedge-shaped slip failure body is divided into n equal soil strips to obtain the gravity dW of a unit soil strip θ and the force arm s of the gravity center of the unit soil strip with respect to the rotation center O θ :

[0029]

[0030] The force arm s of the gravity center of the unit soil strip with respect to the rotation center O θ :

[0031]

[0032] A2, the gravity dW of a unit soil strip obtained in A1 is used to obtain the gravity moment M of the log-spiral wedge-shaped slip failure body itself in front of the two tunnel faces with respect to the rotation center O by using formula (3) θ ​and the force arm s of the gravity center of the soil slice to the rotation center O θ An integral equation as shown in equation (9) is established to derive the gravity moment equation of the wedge-shaped sliding failure body at the rotation center O;

[0033]

[0034] Preferably, the equation (2) is derived by the following steps: C′ is the long axis value of the elliptical failure body.

[0035] Preferably, the equation (6) is derived by the following steps:

[0036] B1, assuming that the soil slice of the wedge-shaped sliding failure body in front of the tunnel face keeps force balance in the horizontal and vertical directions, the force relationship of the soil slice in the horizontal and vertical directions as shown in equation (10) is obtained:

[0037]

[0038] In equation (10), l θ = r θ dθ, T θ is the tangential impedance force on the logarithmic spiral sliding surface of the arbitrary soil slice of the wedge-shaped sliding failure body, N θ is the normal impedance force on the logarithmic spiral sliding surface of the arbitrary soil slice of the wedge-shaped sliding failure body.

[0039] B2, based on the Mohr-Coulomb failure criterion, the tangential impedance force T θ on the logarithmic spiral sliding surface of the arbitrary soil slice of the wedge-shaped sliding failure body is obtained:

[0040]

[0041]

[0042] B3, the integral equation as shown in equation (13) is established according to equations (11) and (12) to derive the impedance moment M RO on the logarithmic spiral sliding surface of the wedge-shaped sliding failure body.

[0043]

[0044] Preferably, after the step S3, the method further comprises: performing numerical simulation analysis by using a numerical simulation method to obtain a numerical simulation result; comparing the numerical simulation result with the support force P calculated in the step S3; and determining that the active failure mode and the critical support force P are reasonable if the comparison result is within an error range, otherwise, the active failure mode and the critical support force P are unreasonable.

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

[0046] A first modeling module for establishing an active failure mode of a tunnel face in counter-advancing excavation, the active failure mode comprising a logarithmic spiral wedge-shaped slip surface failure body in front of the two tunnel faces and a semi-elliptical collapse body above the two tunnel faces;

[0047] A second modeling module for determining geometric relationships of the active failure mode, based on limit equilibrium method, to obtain a moment balance equation of the logarithmic spiral wedge-shaped slip surface failure body and the semi-elliptical collapse body;

[0048] A third calculation module for inversely deriving a critical support pressure P of the tunnel face in counter-advancing excavation according to the moment balance equation.

[0049] As a further improvement of the above technical solution, preferably, the system for determining support pressure of a tunnel face in counter-advancing excavation further comprises a fourth verification and judgment module for performing numerical simulation analysis by using a numerical simulation method to obtain a numerical simulation result, and comparing the numerical simulation result with the critical support pressure P calculated by the third calculation module, and if the comparison result is within an error range, it is judged that the active failure mode and the critical support pressure P are reasonable, otherwise, they are not reasonable.

[0050] As a general inventive concept, the present application also provides a system for determining support pressure of a tunnel face in counter-advancing excavation, comprising a microprocessor and a memory connected to each other, the microprocessor being programmed or configured to perform the steps of the above-mentioned method for determining support pressure of a tunnel face in counter-advancing excavation.

[0051] As a general inventive concept, the present application also provides a computer readable medium having stored therein a computer program programmed or configured to perform the above-mentioned method for determining support pressure of a tunnel face in counter-advancing excavation.

[0052] Compared with the prior art, the present application has the following advantages:

[0053] The present application constructs an active failure mode of a tunnel face in counter-advancing excavation, the active failure mode comprising a logarithmic spiral wedge-shaped slip surface failure body in front of the two tunnel faces and a semi-elliptical collapse body above the two tunnel faces, derives a theoretical model of critical support pressure of the tunnel face in counter-advancing excavation, and obtains the critical support pressure of the tunnel face. A numerical simulation method is used to simulate a numerical simulation failure mode of the tunnel face in counter-advancing excavation and its critical support force, to verify the rationality of the theoretical model of the active failure mode in analyzing the stability of the tunnel face. The verification result shows that the model is reasonable for analyzing the stability of the tunnel face considering the counter-advancing excavation, and the support pressure result of the tunnel face is reliable under the premise of ensuring the construction period. Attached Figure Description

[0054] 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.

[0055] Figure 2 This is a mechanical analysis diagram of the wedge-shaped rotational failure region provided in an embodiment of the present invention.

[0056] 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.

[0057] Figure 4 This is a schematic diagram of the numerical model provided in an embodiment of the present invention.

[0058] 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.

[0059] 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.

[0060] 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

[0061] 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.

[0062] Example 1:

[0063] like Figures 1 to 7 As shown in the figure, a method for determining the support pressure at the tunnel face in a counter-excavation tunnel according to this embodiment includes the following steps:

[0064] 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 semi-elliptical collapse body above the two tunnel faces.

[0065] The application first establishes an active failure mode of a tunnel face of opposite excavation. Active failure of the tunnel face is that when the support pressure applied to the tunnel face is less than the soil pressure of the tunnel face, the soil within a certain range in front of the tunnel face collapses and fails towards the inside of the tunnel. Assuming that the stratum is homogeneous soil, the ground surface is completely horizontal, there is no additional load on the ground surface, the influence of underground water is not considered, the failure range of the tunnel face does not reach the ground surface, the tunnel depth is C, the tunnel diameter is D, the horizontal distance between the tunnel faces of two tunnels is L, and a uniform support force is applied to the tunnel face. In order to be simple, the stability problem of the tunnel face of opposite excavation is assumed to be a two-dimensional plane model. Considering that the entire model is left-right symmetrical, only the left half is taken as an example for description. When the distance between the tunnel faces of opposite excavation is continuously close, a wedge-shaped failure body of a logarithmic spiral slip surface is formed in front of the tunnel faces of two tunnels. Under the action of double disturbance of opposite excavation, a double disturbance area is formed above the tunnel faces of two tunnels. The outline of the double disturbance area is close to a semi-ellipse. Therefore, the active failure mode of the tunnel face of opposite excavation provided by the application includes a wedge-shaped failure body of a logarithmic spiral slip surface in front of the tunnel faces and a semi-ellipse collapse body above the tunnel faces, as shown in FIG. 1. Figure 1

[0066] S2, a geometric relationship of the active failure mode is determined. Based on the limit equilibrium method, a moment balance equation of the wedge-shaped failure body of a logarithmic spiral slip surface and the semi-ellipse collapse body is obtained.

[0067] According to the disturbance characteristics of the soil in front of the tunnel face of opposite excavation, it is assumed that the two tunnel faces of opposite excavation will disturb each other when the distance between the two tunnel faces is L. A wedge-shaped body EGF with a logarithmic spiral failure surface is established in front of the tunnel face, and the rotation center O occurs in the rotation failure. The soil in the area above the soil between the tunnel faces is a semi-ellipse failure body, which vertically downwardly fails under the action of its own gravity. The wedge-shaped failure body EGF acts on its own gravity W, the support force P of the tunnel face, and the gravity σ of the semi-ellipse failure body above it. v The shear force T and the normal force N on the logarithmic spiral surface, and the gravity σ of the semi-ellipse failure body acting on itself. v .

[0068] The soil body parameters and the geometric parameters of the failure mode of the embodiment project are shown in Table 1.

[0069] Table 1: Soil body and geometric parameters of opposite excavation tunnel.

[0070]

[0071] As Figure 2 ​As shown, the wedge-shaped failure body (i.e. the logarithmic spiral wedge-shaped failure body) of the logarithmic spiral slip surface in front of the tunnel face of the counter-attack tunnel rotates and slips along the logarithmic spiral slip surface around a rotation center O point, the wedge-shaped slip failure body is EGF, EG is exactly the radius of the tunnel face, EF is half of the distance between the two tunnel faces, i.e. L / 2, and the horizontal distance of the left tunnel face from the rotation center O is l OE The elliptical failure body of the double disturbance area formed above the two tunnel faces rotates downward in the vertical direction, and it is assumed that the minor axis of the elliptical failure body is exactly equal to the distance L between the two tunnel faces, and the major axis is C'.

[0072] When the rotation center O rotates through an angle θ, the logarithmic spiral of the wedge-shaped failure body can be expressed as:

[0073]

[0074] where r is the radius corresponding to the logarithmic spiral when the rotation angle is θ, is the included angle between the initial radius r0 and the horizontal line.

[0075] According to the geometric relationship, the initial radius r0, the horizontal distance l of the side tunnel face from the rotation center O OE and the distance L between the two tunnel faces, the tunnel radius D, and the included angle between the initial radius r0 and the horizontal line The geometric relationship between the initial radius r0 and the final radius r of the logarithmic spiral slip surface in front of the tunnel face of the counter-attack tunnel α and the included angle α between them is:

[0076]

[0077]

[0078]

[0079] According to the limit equilibrium theory, the moment balance equation of the failure body EGF and the semi-elliptical failure body of the failure mode of the tunnel face of the counter-attack tunnel provided by the present application can be obtained as:

[0080]

[0081] where, M wO is the gravity moment of the wedge-shaped slip failure body EGF in front of the tunnel face on the rotation center O point, is the uniform load σ v acting on the wedge-shaped slip failure body EGF in front of the tunnel face generated by the gravity of the semi-elliptical collapse body above the two tunnel faces, and M POThe supporting moment M formed by the uniform supporting force P acting on the tunnel face to the rotation center O RO The resisting moment of the wedge-shaped sliding failure body EGF on the logarithmic spiral sliding surface in front of the tunnel face.

[0082] S3, the critical supporting force P acting on the tunnel face is calculated by inversely deducing the moment balance equation.

[0083] First, each moment is calculated separately:

[0084] 1) The gravity moment M of the wedge-shaped sliding failure body EGF to the rotation center O wO :

[0085] As Figure 3 shown, referring to the Bishop slice method, the wedge-shaped sliding failure body EGF is divided into n equal soil slices, then the gravity of a unit soil slice is:

[0086]

[0087] Where γ is the unit weight of the soil, is the angle between the tangent at the intersection point of the logarithmic spiral curve and the horizontal line when the initial radius r0 of the logarithmic spiral curve of the wedge-shaped failure body turns through an angle θ.

[0088] The force arm of the center of gravity of a unit soil slice to the rotation center O is:

[0089]

[0090] The moment of the wedge-shaped sliding failure body EGF to the rotation center O is:

[0091]

[0092]

[0093] Where:

[0094]

[0095] 2) The gravity moment of the elliptical gravity failure area to the rotation center O

[0096] The distributed force of the gravity of the elliptical gravity failure area can be expressed as:

[0097]

[0098] Then the moment can be expressed as:

[0099]

[0100] 3) The support moment M generated by the uniform support force P on the tunnel face on the center of rotation O PO

[0101]

[0102] 4) The resistance moment M on the logarithmic spiral slip surface of the wedge-shaped slip failure body EGF in front of the tunnel face RO

[0103] The soil strips of the wedge-shaped slip failure body EGF in front of the tunnel face maintain force balance in the horizontal and vertical directions, and thus the force relationship in the horizontal and vertical directions can be expressed as:

[0104]

[0105] Based on the Mohr-Coulomb failure criterion, the tangential resistance force on the logarithmic spiral slip surface of any soil strip of the wedge-shaped slip failure body EGF is:

[0106]

[0107] where l θ = r θ dθ

[0108] According to equations 15 and 16, we have:

[0109]

[0110] Then the resistance moment M on the logarithmic spiral slip surface of the wedge-shaped slip failure body EGF is: RO which can be expressed as:

[0111]

[0112]

[0113] Substituting equations (9), (12), (13), and (18) into equation (5), it is derived that the limit support force P of the tunnel face can be expressed as:

[0114]

[0115] where:

[0116]

[0117] S4, simulation verification is carried out using FLAC3D numerical simulation software, including verification of the established failure mode of the tunnel face and the critical support force of the counter-excavation tunnel:

[0118] FLAC3D numerical simulation software is used to simulate the failure mode and critical support force of the tunnel face with different spacing. In the simulation, the tunnel contour is formed by full-face excavation at one time. In order to avoid the influence of boundary effects on the accuracy of the simulation, the model is set to be large enough, and the two-dimensional plane numerical model is established as shown in Figure 4 . In the numerical simulation, the length of the entire model is 80m, the thickness is 1m, and the height is 50m. The grid is divided into blocks. When the spacing of the tunnel face of the opposite excavation is 60m, the entire model is composed of 16000 unit bodies, including 32522 unit nodes. The top of the model is a free surface, the vertical surface on both sides is fixed in the horizontal direction, and the vertical direction can deform freely, and the bottom of the model is completely fixed. In the simulation, it is assumed that the soil body obeys the Mohr-Coulomb failure criterion, the soil body is a non-cohesive soil, and the influence of additional load is ignored, i.e. the cohesion c is 0. In the simulation process, the specific parameters are shown in Table 1.

[0119] In order to concentrate on verifying the failure mode and critical support pressure of the tunnel face with different spacing, the spacing of the tunnel face of the opposite excavation is 60m in the first simulation, and then the spacing of the tunnel face of the opposite excavation is gradually reduced by 10m each time, and the minimum is 10m. When the tunnel excavation is completed, the soil inside the tunnel is supported in time, and the surface stress is applied instead of the lining support. Then, the face support force P perpendicular to the face is applied to the face, and the initial support force of the face is applied according to γ×H×K (where K is the pressure coefficient, ). In order to obtain the critical support force of the face, the stress control method is used to gradually reduce the face support force. The stress control method gradually reduces the applied face support force until the soil of the face still deforms significantly when the applied face support force is unchanged, which is considered as the critical support force of the tunnel face. By simulating the face failure of the tunnel face with a spacing of 60m, 50m, 40m, 30m, 20m and 10m, the displacement contour of the tunnel face can be obtained as shown in Figure 5 , wherein Figure 5 (a) to Figure 5 (f) are 60m to 10m, respectively.

[0120] The relationship between the tunnel face support force and the horizontal displacement of the face center point is shown in Figure 6 ( Figure 6 (a) is the left displacement, Figure 6(b) is right side displacement). Comparing the failure mode of the tunnel face provided by the application with the displacement nephogram obtained by FLAC3D numerical simulation, it is found that when the tunnel face distance is 20 m and 10 m, the failure mode provided by the application is very close to the numerical simulation result, indicating that the failure mode of the tunnel face provided by the application can reflect the failure characteristics when the tunnel face distance is small and the tunnel faces affect each other, and the failure mode of the tunnel face provided by the application is reasonable.

[0121] Further comparing the theoretical model solution of the tunnel face support pressure provided by the application with the critical support pressure of the tunnel face determined by numerical simulation, the result is shown in Figure 7 . It is found through comparison that when the tunnel face distance is 60 m, 50 m, 40 m, 30 m, 20 m and 10 m, the theoretical model solution of the tunnel face support pressure provided by the application is basically consistent with the critical support pressure of the tunnel face determined by numerical simulation. The comparison result shows that the theoretical model of the tunnel face support pressure provided by the application is reliable.

[0122] As a general inventive concept, the application further provides a tunnel face support pressure determination system for opposite excavation, comprising the following modules:

[0123] A first modeling module is configured to establish an active failure mode of the soil body of the tunnel face for opposite excavation, wherein the active failure mode comprises a logarithmic spiral wedge-shaped slip surface failure body in front of the two tunnel faces and a semi-elliptical collapse body above the two tunnel faces.

[0124] A second modeling module is configured to obtain a moment balance equation of the logarithmic spiral wedge-shaped slip surface failure body and the semi-elliptical collapse body according to formula (1) based on the limit equilibrium method:

[0125]

[0126] wherein M wO is the gravity moment of the logarithmic spiral wedge-shaped slip surface failure body in front of the two tunnel faces to the rotation center O point, M v is the gravity moment of the semi-elliptical collapse body above the two tunnel faces to the rotation center O point, PO M RO is the support moment of the uniform support force P on the tunnel face to the rotation center O point,

[0127] A third calculation module is configured to obtain the critical support force P of the tunnel face for opposite excavation according to formula (1) by reverse derivation.

[0128]

[0129] In the above formula, γ is the unit weight of the soil body, σ v is the distributed force on the failure body of the logarithmic spiral wedge-shaped slip surface generated by the gravity of the semi-elliptical collapse body above the two working faces, c is the cohesion, r0 is the initial radius of the slip surface of the failure body of the logarithmic spiral wedge-shaped slip surface, θ is the angle of rotation of the initial radius r0 around the rotation center O, D is the radius of the tunnel opposite the excavation tunnel, is the angle between the initial radius r0 and the horizontal line, L is the distance between the two working faces of the tunnel, and α is the angle between the initial radius r0 and the final radius r α of the slip surface of the logarithmic spiral wedge-shaped slip surface,

[0130]

[0131]

[0132] The system for determining the support pressure of the working face of the tunnel opposite the excavation tunnel further comprises a fourth verification and judgment module for performing numerical simulation analysis by using a numerical simulation method to obtain a numerical simulation result, comparing the numerical simulation result with the critical support force P calculated by the third calculation module, and judging that the active failure mode and the critical support force P are reasonable if the comparison result is within an error range, and otherwise not reasonable.

[0133] As a general inventive concept, the present application also provides a system for determining the support pressure of the working face of the tunnel opposite the excavation tunnel, comprising a microprocessor and a memory connected to each other, the microprocessor being programmed or configured to perform the steps of the method for determining the support pressure of the working face of the tunnel opposite the excavation tunnel.

[0134] As a general inventive concept, the present application also provides a computer readable medium, the computer readable storage medium storing a computer program programmed or configured to perform the method for determining the support pressure of the working face of the tunnel opposite the excavation tunnel.

[0135] Those skilled in the art will appreciate that embodiments of the present application can be readily used as software, hardware, or a combination of software and hardware. In a software embodiment, various software modules in accordance with embodiments of the present application are stored in a memory such as a computer memory or disk storage for use by, or in connection with, the software on the computer system. The software can provide for programs to be transferred to another computer readable medium for use by or in connection with the other system. For the purposes of this application, a computer readable medium can be any medium that can contain, store, or maintain the program for use by or in connection with the computer system, apparatus, or device. The computer readable medium can be, but is not limited to, an electronic, magnetic, optical, electromagnetic, infrared, or semiconductor system, apparatus, or device. More specific computer readable medium examples would include a portable magnetic disk, a random access memory (RAM), a read-only memory (ROM), an erasable programmable read-only memory (EPROM or Flash memory), and optical fiber. Note that the computer readable medium can even be paper or another suitable medium upon which the program is printed, as the medium is to be Figure 1 one or more functions specified in the flow or flows and / or blocks Figure 1 one or more functions specified in the flow or flows and / or blocks Figure 1 one or more functions specified in the flow or flows and / or blocks Figure 1 one or more functions specified in the flow or flows and / or blocks Figure 1 one or more functions specified in the flow or flows and / or blocks Figure 1 Figure 1 one or more functions specified in the flow or flows and / or blocks

[0136] While this application has been disclosed in connection with the preferred embodiments shown and described, many modifications and variations of which will be appreciated to those skilled in the art. It is therefore contemplated that the application shall ove all modifications and variations that do not depart from the spirit and scope of the present application.

Claims

1. A method of determining support pressure against a tunnel face in a tunnel excavation, characterized by: The method comprises the following steps: S1, establishing an active failure mode of a tunnel face of a counter-excavation, the active failure mode comprising a logarithmic spiral wedge-shaped sliding surface failure body in front of the two tunnel faces and a semi-elliptical collapse body above the two tunnel faces; S2, determining the 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 semi-elliptical collapse body based on a limit equilibrium method; S3, obtaining a critical support force P of the tunnel face of the counter-excavation by reverse derivation according to the moment balance equation; In the step S2, the moment balance equation is shown in equation (1): （1） wherein, is the gravity torque formed by the gravity of the two-face front logarithmic spiral wedge slip surface damage body to the rotation center O point, is the gravity of the two-face front semi-elliptical collapse body acting on the logarithmic spiral wedge slip surface damage body is the torque formed by the rotation center O point, is the support torque formed by the uniform support force P acting on the tunnel face to the rotation center O point, is the impedance torque on the logarithmic spiral slip surface of the logarithmic spiral wedge slip surface damage body; The critical support force P of the tunnel face of the counter-excavation is shown in equation (2): （2） In the above formula, The equation (3) is obtained by the following steps: The unit weight of soil. The force distributed on the logarithmic spiral wedge-shaped slip surface failure body is the gravitational force of the semi-elliptical collapse body above the two facets. c For cohesion, , , , The initial radius of the slip surface of the logarithmic spiral wedge-shaped slip surface failure body is given. , Starting radius The angle of rotation around the center of rotation O, D The radius of the tunnel is the radius of the tunnel excavated from opposite directions. Starting radius The angle between the tunnel face and the horizontal line, where L is the distance between the two tunnel faces. The initial radius of the slip surface of the logarithmic spiral wedge-shaped slip surface failure body and final radius The angle between them ， 。 2. The method of claim 1, wherein: In the step S2, the gravity moment formed by the gravity of the failure body of the logarithmic spiral wedge-shaped slip surface in front of the two working faces around the rotation center O point is obtained by using formula (3) （3） The gravity of the semi-elliptical collapse body above the two working faces is used to obtain the uniform load on the logarithmic spiral wedge-shaped sliding failure body The moment of force formed by the rotation center O point （4） The support moment P generated by the support force P on the tunnel face on the rotation center O is obtained by using equation (5) （5） The impedance moment on the logarithmic spiral slip surface of the wedge-shaped slip failure body is obtained by using equation (6) （6）。 3. The method of claim 2, wherein: The equation (6) is obtained by the following steps: A1, divide the wedge-shaped sliding failure body into n equal soil strips to obtain the gravity of a unit soil strip and the force arm of the center of gravity of a unit soil strip to the rotation center O : （7） （8） for a starting radius at an angle radius of the slip plane at the time of the logarithmic spiral wedge slip plane failure body slip plane A2, the gravity of the unit soil strip obtained according to A1 and the force arm of the gravity center of the unit soil strip to the rotation center O An integral equation as shown in equation (9) is established, and the equation of the moment of gravity generated by the wedge-shaped slip failure body at the rotation center O is derived. （9）。 4. The method of claim 3, wherein: In the formula (2) shown , is the long axis value of the elliptical damage body.

5. The method of claim 4, wherein: B1, the soil strip of the wedge-shaped sliding failure body in front of the tunnel face keeps force balance in the horizontal and vertical directions, and a force relationship of the soil strip in the horizontal and vertical directions is obtained as shown in equation (10): After the step S3, the method further comprises performing numerical simulation analysis by using a numerical simulation method to obtain a numerical simulation result, comparing the numerical simulation result with the support force P obtained in the step S3, and judging that the active failure mode and the critical support force P are reasonable if the comparison result is within an error range, or not reasonable otherwise. （10） In formula (10), , is the tangential resistance force on the logarithmic spiral slip surface of any soil slice of the wedge-shaped slip failure body, is the normal resistance force on the logarithmic spiral slip surface of any soil slice of the wedge-shaped slip failure body. B2, based on Mohr-Coulomb failure criterion, the tangential impedance force on the logarithmic spiral slip surface of any soil strip of wedge-shaped slip failure body is obtained : （11） （12） B3. The integral equation as shown in equation (13) is established according to equation (11) and equation (12), and the impedance moment on the logarithmic spiral slip surface of the wedge-shaped slip failure body is derived ; （13）。 6. The method of claim 5, wherein: The method comprises the following modules:

7. A system for determining support pressure on a face of a tunnel being excavated, for carrying out the method of determining support pressure on a face of a tunnel being excavated according to any one of claims 1 to 6, characterized in that: A first modeling module is configured to establish an active failure mode of a tunnel face of a counter-excavation, the active failure mode comprising a logarithmic spiral wedge-shaped sliding surface failure body in front of the two tunnel faces and a semi-elliptical collapse body above the two tunnel faces; A second modeling module is configured to determine the geometric relationship of the active failure mode, and obtain a moment balance equation of the logarithmic spiral wedge-shaped sliding surface failure body and the semi-elliptical collapse body based on a limit equilibrium method; A third calculation module is configured to obtain a critical support force P of the tunnel face of the counter-excavation by reverse derivation according to the moment balance equation. The computer readable medium stores a computer program programmed or configured to perform the method for determining a support pressure of a tunnel face of a counter-excavation according to any one of claims 1 to 6.

8. A computer readable medium characterized by: ​

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