Shield tunneling face instability calculation method considering seepage

Abstract

The invention relates to the technical field of shield tunnel construction, in particular to a shield tunneling face instability calculation method considering seepage, which comprises the following steps: S1, extracting pressure water head values of all coordinates in front of an excavation face based on a seepage field in front of the shield tunneling face, and carrying out numerical fitting on all the pressure water head values to obtain a seepage field; obtaining a tunneling face seepage experience model combining a spiral failure mechanism and a translational failure mechanism; s2, constructing a shield tunneling face instability failure mechanism based on the tunneling face seepage experience model; and S3, based on the instability failure mechanism of the shield tunneling face, effective support pressure is obtained. According to the method, the influence of underground water seepage on the stability of the tunneling face is fully considered, more scientific and accurate effective supporting pressure is obtained through calculation, direct guidance is provided for shield tunneling construction, engineers are helped to formulate reasonable supporting schemes and construction parameters, the stability of the tunneling face is ensured, and the construction risk is reduced.

Description

Technical Field

[0001] The invention relates to the technical field of shield tunnel construction, in particular to a shield tunneling face instability calculation method considering seepage. Background Art

[0002] In the development of shield tunneling technology, ensuring the stability of the excavation face has always been a core issue in engineering practice. As tunnel construction extends to more complex geological conditions, especially when encountering groundwater-rich strata, the impact of groundwater seepage on the stability of the excavation face becomes more and more significant. However, current technology still has shortcomings in dealing with this complex problem.

[0003] In the prior art, patent CN114970122A provides a method and system for calculating the optimal support force for instability of the shield tunnel excavation face. This method takes into account a variety of mechanical factors when evaluating the stability of the excavation face, providing an important reference for engineering practice. However, a significant limitation of this technology is that it fails to fully consider the changes in pore water pressure during groundwater seepage and its impact on the stability of the excavation face. The work done by pore water pressure is an important mechanism by which groundwater seepage directly affects soil stability. Ignoring it may lead to deviations in the calculation results and fail to fully reflect the stability status in actual engineering.

[0004] Therefore, it is necessary to develop a more comprehensive and accurate shield excavation face stability analysis method that fully considers the impact of seepage on the excavation face stability. Summary of the invention

[0005] To this end, the technical problem to be solved by the present invention is to overcome the problem that the prior art focuses more on the mechanical properties of soil and its interaction with support pressure, while less consideration is given to the influence of seepage on the stability of the excavation surface, resulting in deviations in the calculation results of limited support pressure and inability to accurately evaluate the stability of the excavation surface.

[0006] In order to solve the above technical problems, the present invention provides a shield tunneling face instability calculation method considering seepage, comprising the following steps:

[0007] S1: Based on the seepage field in front of the shield tunneling face, the pressure head values ​​of each coordinate in front of the excavation face are extracted, and all the pressure head values ​​are numerically fitted to obtain the empirical seepage model of the tunneling face;

[0008] S2: Based on the empirical model of tunneling face seepage, the instability and failure mechanism of the shield tunneling face is constructed;

[0009] S3: Based on the instability and failure mechanism of the shield tunneling face, the effective support pressure is obtained.

[0010] In one embodiment of the present invention, in S1, the expression of the empirical seepage model of the tunneling face is:

[0011]

[0012] Where Δh is the tunnel head difference, h F is the fixed pressure head on the excavation surface, D is the tunnel diameter, and b is the fitting parameter.

[0013] In one embodiment of the present invention, in S2, the method for constructing the instability and failure mechanism of the shield tunneling face is:

[0014] The soil is a uniform soil layer, the effective weight of the soil is γ', the effective cohesion is c', and the effective friction angle is The soil failure satisfies the Mohr-Coulomb criterion, the tunnel burial depth is C, and the effective support pressure σ t '1 acts evenly on the excavation face AB;

[0015] The two-dimensional plane structure of the instability failure mechanism of the shield tunneling face is constructed by using the global coordinate system O(r,θ) and the local coordinate system A(x,y). The instability failure mechanism of the shield tunneling face includes a spiral failure mechanism and a translational failure mechanism; wherein the translational failure mechanism is a plane area composed of point A, point B and point F, and the translational failure mechanism is at point A with a velocity vector For translation, The angle with the horizontal is α; the spiral failure mechanism and the translation failure mechanism are transitioned through the velocity discontinuity surface AF, and a point O is arbitrarily set as the rotation center of the spiral failure mechanism, which rotates clockwise at an angular velocity ω through points O' and A, and the failure boundaries AO' and O'F are logarithmic spirals;

[0016] The distance from the groundwater level to the top of the shield tunnel is h w ; Under the condition that the seepage during tunnel excavation will not cause the groundwater level to drop, the boundary condition of the groundwater level is set to h = h0, where h0 is the groundwater level elevation; when the tunnel end face is under normal pressure, the excavation face is a fixed pressure head Tunnel head difference Δh=h w -h F , considering the pore water pressure u as acting on the soil skeleton and the permissible velocity field v i Therefore, in the instability failure mechanism of the shield tunneling face, u acts on the failure boundaries AF, BF, AO' and O'F, r u is the pore water pressure coefficient.

[0017] In one embodiment of the present invention, in S3, the effective support pressure σ′ is obtained t1 The method is as follows:

[0018] S31: Considering the effect of pore water pressure on the shield tunneling face, for any motion permissible velocity field v i and the strain rate field ε ij , the shield tunneling face structure is in a stable state, and the system dissipated power P v And the actual external force work power P e The following constraints are met:

[0019] Pv≥Pe

[0020] in, is the strain energy per unit volume, is the internal strain rate tensor of the strain body, Ω is the structural volume, S is the boundary volume of the failure mechanism, T i is the traction force vector on the strain body boundary S, γ i is the weight vector, n i is the normal vector perpendicular to the failure surface, and the work done by the pore water pressure is

[0021] S32: Based on the empirical seepage model of the excavation face, under the constraints, let and h F = 0, according to the empirical model of seepage at the excavation face, the work power of the pore water pressure u acting on the boundary surfaces AF, BF, AO', O'F is calculated to obtain the pore water pressure work power P u ;

[0022] S33: The sum of the energy dissipation power on the destruction boundaries AF, BF, O'F, AO' Based on the pore water pressure work power P u and soil gravity power P γ , and obtain the effective support pressure power

[0023] S34: Based on the effective support pressure power The effective support pressure σ is calculated as t1 ′.

[0024] In one embodiment of the present invention, the pore water pressure work power P u The calculation formula is:

[0025] P u =P uAO′ +P uO′F +P uAF +P uBF

[0026] Among them, P uAO′is the work power of pore water pressure u acting on the boundary surface AO', P uO′F is the work done by the pore water pressure u on the boundary surface O'F, P uAF is the work done by the pore water pressure u on the boundary surface AF, P uBF is the work power of pore water pressure u acting on the boundary surface BF;

[0027] The pore water pressure u acts on the boundary surface AO' to do work P uAO′ The calculation method is as follows:

[0028] Let n i =1, u=r u γ′h AO′ , the work power P of the pore water pressure u acting on the boundary surface AO' is obtained uAO′ :

[0029]

[0030] The pore water pressure u acts on the boundary surface O'F to do work P uO′F The calculation method is as follows:

[0031] Let n i =1, u=r u γ′h O′F , the work power P of the pore water pressure u acting on the boundary surface O'F is obtained uO′F :

[0032]

[0033] The work power P of the pore water pressure u acting on the boundary surface AF uAF The calculation method is as follows:

[0034] Let n i =1, u=r u γ′h AF , the work power P of the pore water pressure u acting on the boundary surface AF is obtained uAF :

[0035]

[0036] The pore water pressure u acts on the boundary surface BF to do work P uBF The calculation method is as follows:

[0037] Let n i =1, u=r u γ′h BF, the work power P of the pore water pressure u acting on the boundary surface BF is obtained uBF :

[0038]

[0039] Among them, v AO′ is the velocity of any point on AO′, x AO′ is the horizontal coordinate of any point on AO′; v O′F is the velocity of any point on O'F, x O′F is the horizontal coordinate of any point on O'F; v AF is the speed of any point on AF, x AF is the horizontal coordinate of any point on AF; v BF is the velocity of any point on BF, x BF is the horizontal coordinate of any point on BF.

[0040] In one embodiment of the present invention, the effective support pressure power The support force σ on the excavation face t ′1 can be expressed as:

[0041]

[0042] in, is the excavation face support force vector, v1 is Model.

[0043] In one embodiment of the present invention, the soil gravity power P γ The calculation formula is:

[0044]

[0045] Among them, x F is the horizontal coordinate of point F, θ F is the angle between OF and the vertical direction, θ O′ is the angle between OO′ and the vertical direction, r F is the OF length, r A is the OA length, θ A is the angle between OA and the vertical direction.

[0046] In one embodiment of the present invention, the effective support pressure σ t1 The calculation formula of ′ is as follows:

[0047]

[0048] Among them, N γ1 、N c1 、N u are transition variables.

[0049]

[0050]

[0051] v 12,i is the relative velocity vector, r BF is the distance from any point on BF to point O, x BF is the horizontal coordinate of any point on BF, x BO′ for; r AO′ is the distance from any point on AO′ to point O, r FO′ is the distance from any point on FO′ to point O, P i For any known point on AF′, P i+1 is the next generation point, P i P i+1 =s, s is the discrete length.

[0052] Based on the same inventive concept, the present invention also provides a shield tunneling face instability calculation system considering seepage, which is used to execute the steps of the shield tunneling face instability calculation method considering seepage, and the system includes the following modules:

[0053] An empirical model acquisition module, which is used to extract the pressure head values ​​of various coordinates in front of the excavation face based on the seepage field in front of the shield tunneling face, perform numerical fitting on all the pressure head values, and obtain an empirical model of seepage in the tunneling face;

[0054] A failure mechanism construction module, wherein the failure mechanism construction module is used to construct an instability failure mechanism of a shield tunneling face based on the tunneling face seepage empirical model;

[0055] An effective support pressure calculation module is used to obtain the effective support pressure based on the instability and failure mechanism of the shield tunneling face.

[0056] The present invention also provides a computer storage medium storing a computer software product. The computer software product includes several instructions for enabling a computer device to execute the method for calculating the instability of a shield tunneling face taking into account seepage.

[0057] The above technical solution of the present invention has the following advantages compared with the prior art:

[0058] The present invention constructs an empirical seepage model of the excavation face by numerically fitting the seepage field data in front of the shield excavation face, and constructs the instability failure mechanism of the shield excavation face based on this model. This method combines the principles of seepage mechanics and soil mechanics, fully considers the influence of groundwater seepage on the stability of the excavation face, and makes the calculation result of the effective support pressure more scientific and accurate; the calculated effective support pressure can provide direct guidance for shield excavation construction, help engineers formulate reasonable support plans and construction parameters, ensure the stability of the excavation face, and reduce construction risks. BRIEF DESCRIPTION OF THE DRAWINGS

[0059] In order to make the content of the present invention more clearly understood, the present invention is further described in detail below according to specific embodiments of the present invention in conjunction with the accompanying drawings, wherein

[0060] Figure 1 It is a flow chart of a shield tunneling face instability calculation method considering seepage provided in the first embodiment of the present invention;

[0061] Figure 2 It is a specific flow chart of a shield tunneling face instability calculation method considering seepage provided in the first embodiment of the present invention;

[0062] Figure 3 (a) shows the structural schematic diagram of the instability failure mechanism of the shield tunneling face, and (b) shows the specific mechanical model of the instability failure mechanism of the shield tunneling face;

[0063] Figure 4 It is a numerical model of the instability failure mechanism of shield tunneling face, where (a) represents the geometric model of the failure mechanism, and (b) represents the mesh adaptive numerical model of the failure mechanism;

[0064] Figure 5 is the effective friction under the conditions of Δh / D = 1.0 and c' / (γ'D) = 0 Comparison of failure modes, where (a) represents Failure mode diagram, (b) represents (c) shows the failure mode diagram when φ' = 45°;

[0065] Figure 6 Figure 2 is a comparison of the failure modes of different effective friction forces φ' under the conditions of Δh / D = 1.0 and c' / (γ'D) = 0.01, where (a) represents Failure mode diagram, (b) represents (c) shows the failure mode diagram when φ' = 45°;

[0066] Figure 7 For Comparison of failure modes of different ratios of Δh / D under the conditions of c' / (γ'D)=0, where (a) represents the failure mode diagram of Δh / D=0, (b) represents the failure mode diagram of Δh / D=1.0, and (c) represents the failure mode diagram of Δh / D=2.0;

[0067] Figure 8 Comparison of failure modes for different ratios of Δh / D under the conditions of φ'=30° and c' / (γ'D)=0.01, where (a) represents the failure mode diagram for Δh / D=0, (b) represents the failure mode diagram for Δh / D=1.0, and (c) represents the failure mode diagram for Δh / D=2.0;

[0068] Fig. 9 The effective friction The influence diagram of groundwater level on support pressure under the condition of , where (a) represents the influence diagram of groundwater level on support pressure when c' / (γ'D)=0.01, and (b) represents the influence diagram of groundwater level on support pressure when c' / (γ'D)=0.02;

[0069] Fig.10 It is the influence diagram of groundwater level on support pressure under the condition of effective friction φ'=20°, where (a) represents the influence diagram of groundwater level on support pressure when c' / (γ'D)=0.01, and (b) represents the influence diagram of groundwater level on support pressure when c' / (γ'D)=0.02;

[0070] Fig.11 The effective friction The influence diagram of groundwater level on support pressure under the condition of , where (a) represents the influence diagram of groundwater level on support pressure when c' / (γ'D)=0.01, and (b) represents the influence diagram of groundwater level on support pressure when c' / (γ'D)=0.02;

[0071] Fig.12 It is a structural schematic diagram of a shield tunneling face instability calculation system considering seepage provided in the first embodiment of the present invention;

[0072] Description of the accompanying drawings in the specification: 100, empirical model acquisition module; 200, failure mechanism construction module; 300, effective support pressure calculation module. DETAILED DESCRIPTION

[0073] The present invention is further described below in conjunction with the accompanying drawings and specific embodiments so that those skilled in the art can better understand the present invention and implement it, but the embodiments are not intended to limit the present invention.

[0074] Embodiment 1

[0075] Reference Figures 1-2As shown, the present invention provides a shield tunneling face instability calculation method considering seepage, comprising the following steps:

[0076] S1: Based on the seepage field in front of the shield tunneling face, the pressure head values ​​of each coordinate in front of the excavation face were extracted by numerical software COMSOL. All the pressure head values ​​were numerically fitted by Origin to obtain the empirical seepage model of the tunneling face.

[0077] S2: Based on the empirical model of tunneling face seepage, the instability and failure mechanism of the shield tunneling face is constructed;

[0078] S3: Based on the instability and failure mechanism of the shield tunneling face, the upper limit theorem is used to obtain the effective support pressure.

[0079] The effective support pressure is used as a key mechanical parameter to directly guide the safe implementation of shield tunneling construction, and assist engineers in formulating scientific and reasonable support plans during the design stage, including the selection of support structures, the setting of support strength, and the optimization of construction parameters. By ensuring that the excavation face maintains a stable mechanical state during the excavation process, the risks and hidden dangers in the construction process are effectively reduced.

[0080] In S1, the expression of the empirical model of seepage at the excavation face is:

[0081]

[0082] Where Δh is the tunnel head difference, h F is the fixed pressure head on the excavation surface, D is the tunnel diameter, and b is the fitting parameter.

[0083] Reference Figure 3 As shown in Figure 2, the method for constructing the instability failure mechanism of the shield tunneling face is:

[0084] The soil is a uniform soil layer, the effective weight of the soil is γ', the effective cohesion is c', the effective friction angle is φ', the soil failure satisfies the Mohr-Coulomb criterion, the tunnel burial depth is C, and the effective support pressure σ t '1 acts evenly on the excavation face AB;

[0085] The two-dimensional plane structure of the instability failure mechanism of the shield tunneling face is constructed by using the global coordinate system O(r,θ) and the local coordinate system A(x,y). The instability failure mechanism of the shield tunneling face includes a translation failure mechanism Ω1 and a spiral failure mechanism Ω2; wherein the translation failure mechanism Ω1 is a plane area composed of point A, point B and point F, and the translation failure mechanism Ω1 is at point A with a velocity vector For translation, The angle with the horizontal is α; the spiral damage mechanism Ω2 and the translational damage mechanism Ω1 are transitioned through the velocity discontinuity surface AF, and a point O is arbitrarily set as the rotation center of the spiral damage mechanism Ω2, which rotates clockwise at an angular velocity ω through points O' and A, and the damage boundaries AO' and O'F are logarithmic spirals;

[0086] The distance from the groundwater level to the top of the shield tunnel is h w ; Under the condition that the seepage during tunnel excavation will not cause the groundwater level to drop, the boundary condition of the groundwater level is set to h = h0, where h0 is the groundwater level elevation; when the tunnel end face is under normal pressure, the excavation face is a fixed pressure head Tunnel head difference Δh=h w -h F , considering the pore water pressure u as acting on the soil skeleton and the permissible velocity field v i Therefore, in the instability failure mechanism of the shield tunneling face, u acts on the failure boundaries AF, BF, AO' and O'F, r u is the pore water pressure coefficient.

[0087] In S3 of this embodiment, the effective support pressure σ′ is obtained t1 The method is as follows:

[0088] S31: Obtain the final expression of the upper limit principle considering the pore water pressure effect, the method includes:

[0089] For any motion-permitted velocity field v i and the strain rate field ε ij , the upper limit theorem shows that when the structure is in a stable state, the system dissipated power is not less than the actual external force work power, that is:

[0090] P v ≥P e (2)

[0091]

[0092] In order to study the effect of seepage on the stability of the shield tunneling face, it is necessary to introduce additional terms in inequality (3) to consider the influence of water. These additional terms must take into account the effects of buoyancy, seepage force and water pressure on the structural boundary, so considering uv i The derivative of :

[0093]

[0094] Integrating formula (4) yields:

[0095]

[0096] Where S is the boundary volume of the failure mechanism, n i is the normal vector perpendicular to the failure surface. is the volume strain rate The negative sign is due to the convention that compression is positive. The pore water pressure u can be expressed as a function related to the water head h (the water flows slowly in the soil seepage, so the dynamic part is omitted):

[0097] u=γ w (hZ) (6)

[0098] Among them, γ w is the weight of water, Z is the set ground elevation, and the value is 0;

[0099] Substituting formula (6) into formula (5), we can get:

[0100]

[0101] The second term on the right side of the above inequality (7) represents the work done by the seepage force in the entire mechanism, and the last term is the work done by the buoyancy force. In order to consider the effect of seepage on the stability of the shield tunnel, the effects of the seepage force and the buoyancy force must be considered simultaneously in the analysis. By adding the two terms, we can get the work done by the pore water pressure on the failure mechanism P u :

[0102]

[0103] At this time, substituting equation (8) into (3) can obtain the final upper limit theorem considering seepage:

[0104]

[0105] At this time, the left side of the inequality is the system dissipated power P when the structure is destroyed. v , the right side of the inequality is the work power P done by the external force e , the ultimate load when the structure is destroyed is usually obtained under the condition that both ends of the inequality are equal. is the strain energy per unit volume, is the internal strain rate tensor of the strain body, Ω is the structural volume, S is the boundary volume of the failure mechanism, T i is the traction force vector on the strain body boundary S, γ i is the weight vector, n i is the normal vector perpendicular to the failure surface;

[0106] S32: Based on the empirical model of seepage at the tunneling face, under the constraints, in order to simplify the calculation, it is assumed that the two failure plates are rigid bodies, that is, the dissipation on the radial discontinuity surface of the internal velocity of the spiral rotating plate is not considered, and the energy dissipation will all occur on the failure boundaries AF, BF, O'F, AO'. Let and hF = 0, according to formula (1), calculate the work power of pore water pressure u acting on boundary surfaces AF, BF, AO', O'F, and obtain the pore water pressure work power P u :

[0107] P u =P uAO′ +P uO′F +P uAF +P uBF (10)

[0108] Among them, P uAO′ is the work power of pore water pressure u acting on the boundary surface AO', P uO′F is the work done by the pore water pressure u on the boundary surface O'F, P uAF is the work done by the pore water pressure u on the boundary surface AF, P uBF is the work done by the pore water pressure u on the boundary surface BF.

[0109] Furthermore, the work power P of the pore water pressure u acting on the boundary surface AO' is uAO′ The calculation method is as follows:

[0110] Let n i =1, u=r u γ′h AO′ , the work power P of the pore water pressure u acting on the boundary surface AO' is obtained uAO′ :

[0111]

[0112] The pore water pressure u acts on the boundary surface O'F to do work P uO′F The calculation method is as follows:

[0113] Let n i =1, u=r u γ′h O′F , the work power P of the pore water pressure u acting on the boundary surface O'F is obtained uO′F :

[0114]

[0115] The work power P of the pore water pressure u acting on the boundary surface AF uAF The calculation method is as follows:

[0116] Let n i =1, u=r u γ′h AF, the work power P of the pore water pressure u acting on the boundary surface AF is obtained uAF :

[0117]

[0118] The pore water pressure u acts on the boundary surface BF to do work P uBF The calculation method is as follows:

[0119] Let n i =1, u=r u γ′h BF , the work power P of the pore water pressure u acting on the boundary surface BF is obtained uBF :

[0120]

[0121] Among them, v AO′ is the velocity of any point on AO′, x AO′ is the horizontal coordinate of any point on AO′; v O′F is the velocity of any point on O'F, x O′F is the horizontal coordinate of any point on O'F; v AF is the speed of any point on AF, x AF is the horizontal coordinate of any point on AF; v BF is the velocity of any point on BF, x BF is the horizontal coordinate of any point on BF.

[0122] S33: According to the upper limit theorem of limit analysis, under the critical state, the sum of the energy dissipation power on the destruction boundaries AF, BF, O'F, and AO' is P v :

[0123]

[0124] Soil gravity power P γ The calculation formula is:

[0125]

[0126] Among them, x F is the horizontal coordinate of point F, θ F is the angle between OF and the vertical direction, θ O′ is the angle between OO′ and the vertical direction, r F is the OF length, r A is the OA length, θ A is the angle between OA and the vertical direction;

[0127] From formula (15), we can know that the sum of energy dissipation power is Based on the pore water pressure work power P u and soil gravity power P γ , calculate the effective support pressure power Among them, the effective support pressure power The support force σ on the excavation face t ′1 is uniformly distributed, it can be expressed as:

[0128]

[0129] in, is the excavation face support force vector, v1 is Model.

[0130] S34: Based on the effective support pressure power The effective support pressure σ is calculated as t1 '; Further, the effective support pressure σ t1 The calculation formula of ′ is as follows:

[0131]

[0132] Among them, N γ1 、N c1 、N u are transition variables.

[0133]

[0134]

[0135] v 12,i is the relative velocity vector, r BF is the distance from any point on BF to point O, x BF is the horizontal coordinate of any point on BF, x BO′ for; r AO′ is the distance from any point on AO′ to point O, r FO′ is the distance from any point on FO′ to point O, P i For any known point on AF′, P i+1 is the next generation point, P i P i+1 =s, s is the discrete length.

[0136] The instability and failure mechanism of the shield tunneling face under seepage conditions proposed in this embodiment was verified, and a two-dimensional numerical calculation model was established using the finite element limit analysis software OPTUM G2. Figure 4As shown, the plane model size is 5D×(4D+C), the tunnel width D=6m, the surface additional load is 0, the cover depth C / D=2.0, the groundwater level can be adjusted as required, and the mechanical parameters of the soil are listed in Table 1. The numerical calculation process used in the present invention is as follows:

[0137] (1) Establish the model, set the soil parameters, and set the constitutive model to Mohr-Coulomb constitutive model;

[0138] (2) Excavate to 2.0D, apply standard boundary conditions and "no seepage" boundary conditions to the tunnel sidewalls and the periphery of the model, set the groundwater level and apply a multiplier distributed load on the tunnel excavation surface, and the multiplier is set to 1 kN / m2; the pressure head of the excavation surface is set to 0;

[0139] (3) Set the number of adaptive iterations to 5, select the hybrid solver for solving, set the number of cells to 3000, set the cell type to "upper limit", select "limit analysis" in the working condition stage manager, and select the shear dissipation result for study.

[0140] Table 1

[0141]

[0142] Figure 5 and Figure 6 The changing trends of the mixed failure mode, numerical shear dissipation solution, and Li Wei solution failure mode are given when c' / (γ'D)=0~0.01, φ'=15°~45°, γ'=9.8kN / m3, D=6m, C / D=2.0, and Δh / D=1.0. Because the Li Wei solution studies the three-dimensional failure mechanism of the excavation surface, this experiment selects its numerical symmetry surface for comparative study. It can be observed that with the increase of the effective internal friction angle, the failure height and failure width of the model of the present invention, the numerical solution, and the Li Wei solution are significantly reduced, and the bottom failure inclination angle is significantly increased. It can be seen from Table 2 that when c' / (γ'D)=0.01, γ'=9.8kN / m3, D=6m, C / D=2.0, and Δh / D=1.0, In the process of increasing from 15° to 45°, the bottom inclination angle of the solution of the present invention increased by 71%, the damage height decreased by 75%, and the damage width decreased by 68%, which are large changes, indicating that the mixing mechanism is highly sensitive to the internal friction angle.

[0143] Vertical comparison Figure 5 , Figure 6 It can be seen that with the increase of effective cohesion, the failure height of the solution of the present invention and Li Wei's solution increases. When γ'=9.8kN / m3, D=6m, C / D=2.0, Δh / D=1.0, When c' / (γ'D) increases from 0 to 0.01, the failure height increases by about 17%, and the numerical solution increases the least, only increasing by less than 5%. The bottom inclination of the failure mechanism decreases with the increase of effective cohesion, but the change is not large. In terms of the predicted failure width, no matter what the working condition, the solution of the present invention is not much different from the numerical solution, indicating that the solution of the present invention can accurately predict the failure distance in front of the excavation face in active instability failure. It can be accurately seen from Table 3 that when the effective cohesion changes, the width of the failure zone changes more obviously for the three solutions, indicating that the width of the failure zone is very sensitive to the effective cohesion.

[0144] Table 2

[0145]

[0146]

[0147] Figure 7 and Figure 8 c' / (γ'D) = 0 to 0.01, γ'=9.8kN / m 3 , D = 6m, C / D = 2.0, Δh / D = 0 ~ 2.0, the comparison diagram of the mixed failure mode of the present invention, the numerical shear dissipation solution, and the failure mode of Li Wei's solution. It can be observed that the failure area of ​​the solution of the present invention and Li Wei's solution is basically the same, and the failure height of the solution of the present invention is slightly larger than that of Li Wei's solution. When Δh / D = 0.1, c' / (γ'D) = 0.01, φ' = 30°, the solution of the present invention η is 0.66, the solution of Li Wei is 0.63, and the numerical solution is 0.65. The difference between the solution of the present invention and the numerical solution is only 1.5%, while the failure mode predicted by the Li Wei solution is 7% different from the numerical solution. When Δh / D becomes larger, the failure height of the solution of the present invention, Li Wei's solution, and the numerical solution all becomes lower, the failure width becomes longer, and the bottom inclination angle becomes larger, that is, the failure area develops toward the front of the excavation face. The changes of the solution of the present invention and the numerical solution are consistent, which also illustrates the reliability of the mixed failure mechanism of the present invention. The bottom inclination angle of the failure surface predicted by the numerical solution is the largest, the solution of the present invention is in the middle, and the bottom inclination angle predicted by Li Wei's solution is the smallest. The reason is that the spiral single mechanism is relatively smooth in the bottom area, so the inclination angle is smaller.

[0148] Table 3

[0149]

[0150]

[0151] It can be accurately seen from Table 3 that the three theoretical solutions considering seepage conditions have significantly decreased damage height and significantly increased damage width as Δh / D increases. In terms of predicted damage width, the theoretical solution of the present invention is very close to the numerical solution, and both are larger than Li Wei's solution, indicating that the mixed mechanism has advantages in predicting damage width. When c' / (γ'D)=0.01、φ'=30°、γ'=9.8kN / m3、D=6m、C / D=2.0, in the process of Δh / D increasing from 0 to 2.0, the damage width predicted by the solution of the present invention increases from 0.58 to 0.84, an increase of about 44.8%; Li Wei's solution increases from 0.57 to 0.79, an increase of 38.6%; the numerical solution increases from 0.59 to 0.83, an increase of about 40.6%. The prediction of damage width by multiple damage modes all show that the damage width is extremely sensitive to the head difference, which is also a problem that needs to be paid attention to in shield construction.

[0152] In order to verify the proposed analytical solution method, Figures 9-11 Given Comparison of the ultimate support capacity of the composite mechanism with existing theoretical solutions and numerical solutions when γ'=9.8kN / m3, D=6m, C / D=2.0, Δh / D=1.0~5.0. It can be found from the figure that the analytical solution of this chapter is basically greater than other existing research solutions, and is very close to the numerical solution. The reason is that the solution of the present invention and the OPTUM G2 solution are both two-dimensional mixed failure modes, and the three-dimensional effect is not taken into account, while other analytical solutions are three-dimensional failure modes, but the ultimate support pressure given by the two-dimensional solution is more conservative, so it can be used well in engineering. It can be seen that with the increase of Δh / D, both the analytical solution and the numerical solution of the ultimate support pressure increase. The solution of the present invention is close to linear growth. The reason is that the analytical solution of the present invention is a 4-variable function, which has great randomness when optimized using MATLAB. Different intervals and different initial values ​​will affect the solution of the ultimate support pressure value. Comparison Fig.11 From (a) and (b), it can be seen that when the effective cohesion of the soil increases, the ultimate support pressure will decrease. When Δh / D = 1.0 and c' / (γ'D) = 0.01, the ultimate support pressure solution of the present invention is 0.76, and the Lee solution is 0.68; when c' / (γ'D) increases to 0.02, the present invention solution is 0.74, and the Lee solution is 0.66, and the two solutions change by 26% and 29% respectively; When it increases to 30°, the solution of the present invention decreases to 0.28, and the Lee solution changes to 0.21, which are reduced by 63% and 68% respectively; this indicates that the sensitivity of the ultimate support pressure to the effective internal friction angle is much greater than that of the effective cohesion.

[0153] The predicted value of the ultimate support pressure of the present invention is also very close to the analytical solution given by Perazzelli et al., because the one-dimensional pressure head empirical formula used in the present invention is quoted from their paper, but the present invention uses the limit analysis method to calculate the ultimate support pressure, while Perazzelli et al. use the limit equilibrium method. When c' / (γ'D)=0.01 and Δh / D=2.0, the predicted value of the solution of the present invention is 0.82, while the predicted value of the Perazzelli solution is 0.81, with a difference of less than 1.5%, which illustrates the accuracy of the composite failure mechanism solution of the present invention. Under the same conditions, the predicted value of Li Wei's solution is 0.76, which is lower than the predicted value of 0.79 of the Pan and Dias solution, but both are ultimate support forces calculated based on limit analysis and numerical analysis. Because the seepage field obtained by Li Wei's solution is more evenly distributed near the excavation surface, the seepage head gradient changes more slowly, so the calculated permeability will be smaller. The analytical solution obtained by the present invention is larger than that of Lee's solution. The difference between the two is mainly because Lee simplified the influence of permeability in his research, only considering the work done by the permeability at the excavation surface, and not considering the energy dissipation on the failure interface, which further reflects the stronger adaptability of the solution of the present invention.

[0154] Embodiment 2

[0155] Based on the same inventive concept as the first embodiment, the present invention also provides a shield tunneling face instability calculation system considering seepage, which is used to execute the steps of the shield tunneling face instability calculation method considering seepage described in the first embodiment, such as Fig.12 As shown, the system includes the following modules:

[0156] An empirical model acquisition module 100 is used to extract the pressure head value of each coordinate in front of the excavation face based on the seepage field in front of the shield tunneling face, perform numerical fitting on all the pressure head values, and obtain an empirical seepage model of the tunneling face;

[0157] A failure mechanism construction module 200, wherein the failure mechanism construction module 200 is used to construct an instability failure mechanism of a shield tunneling face based on the tunneling face seepage empirical model;

[0158] The effective support pressure calculation module 300 is used to obtain the effective support pressure based on the instability and failure mechanism of the shield tunneling face.

[0159] The present embodiment proposes a shield tunneling face instability calculation system considering seepage, which is used to implement the aforementioned shield tunneling face instability calculation method considering seepage. Therefore, the specific implementation method of the shield tunneling face instability calculation system considering seepage can be seen from the aforementioned embodiment part of the shield tunneling face instability calculation method considering seepage. For example, the empirical model acquisition module 100, the destruction mechanism construction module 200 and the effective support pressure calculation module 300 are respectively used to correspond to the implementation of steps S1, S2 and S3 in the shield tunneling face instability calculation method considering seepage in the first embodiment. Therefore, its specific implementation method can refer to the description of the corresponding embodiments of each part. In order to avoid redundancy, it will not be repeated here.

[0160] Embodiment 3

[0161] The present invention also provides a computer storage medium, which stores a computer software product. The computer software product includes several instructions for enabling a computer device to execute the instructions of the shield excavation face instability calculation method considering seepage described in Example 1.

[0162] Those skilled in the art will appreciate that the embodiments of the present application may be provided as methods, systems, or computer program products. Therefore, the present application may adopt the form of a complete hardware embodiment, a complete software embodiment, or an embodiment in combination with software and hardware. Moreover, the present application may adopt the form of a computer program product implemented in one or more computer-usable storage media (including but not limited to disk storage, CD-ROM, optical storage, etc.) that include computer-usable program code.

[0163] The present application is described with reference to the flowcharts and / or block diagrams of the methods, devices (systems), and computer program products according to the embodiments of the present application. It should be understood that each process and / or box in the flowchart and / or block diagram, as well as the combination of the processes and / or boxes in the flowchart and / or block diagram, can be implemented by computer program instructions. These computer program instructions can be provided to a processor of a general-purpose computer, a special-purpose computer, an embedded processor, or other programmable data processing device to generate a machine, so that the instructions executed by the processor of the computer or other programmable data processing device generate instructions for implementing the processes in the flowchart and / or block diagram. Figure 1 A process or multiple processes and / or boxes Figure 1 A device that provides the functions specified in a block or multiple blocks.

[0164] These computer program instructions may also be stored in a computer-readable memory capable of directing a computer or other programmable data processing device to operate in a specific manner, so that the instructions stored in the computer-readable memory produce an article of manufacture comprising an instruction device, which implements the process Figure 1 A process or multiple processes and / or boxes Figure 1 A function specified in one or more boxes.

[0165] These computer program instructions can also be loaded onto a computer or other programmable data processing device so that a series of operating steps are executed on the computer or other programmable device to produce a computer-implemented process, thereby providing instructions for implementing the process. Figure 1 A process or multiple processes and / or boxes Figure 1 The steps for the functions specified in one or more boxes.

[0166] Obviously, the above embodiments are merely examples for clear explanation and are not intended to limit the implementation methods. For those skilled in the art, other different forms of changes or modifications can be made based on the above description. It is not necessary and impossible to list all the implementation methods here. The obvious changes or modifications derived from these are still within the protection scope of the invention.

Claims

1. A shield tunneling face instability calculation method considering seepage, characterized in that: The following steps are involved: S1: Based on the seepage field in front of the shield tunneling face, the pressure head values ​​of each coordinate in front of the excavation face are extracted, and all the pressure head values ​​are numerically fitted to obtain the empirical seepage model of the tunneling face; S2: Based on the empirical model of tunneling face seepage, the instability and failure mechanism of the shield tunneling face is constructed; S3: Based on the instability and failure mechanism of the shield tunneling face, the effective support pressure is obtained.

2. The shield tunneling face instability calculation method considering seepage according to claim 1 is characterized by: In S1, the expression of the empirical model of seepage at the excavation face is: Where Δh is the tunnel head difference, h F is the fixed pressure head on the excavation surface, D is the tunnel diameter, and b is the fitting parameter.

3. The shield tunneling face instability calculation method considering seepage according to claim 2 is characterized by: In S2, the method for constructing the instability failure mechanism of the shield tunneling face is: The soil is a uniform soil layer, the effective weight of the soil is γ', the effective cohesion is c', and the effective friction angle is The soil failure satisfies the Mohr-Coulomb criterion, the tunnel burial depth is C, and the effective support pressure σ t '1 acts evenly on the excavation face AB; The two-dimensional plane structure of the instability failure mechanism of the shield tunneling face is constructed by using the global coordinate system O(r,θ) and the local coordinate system A(x,y). The instability failure mechanism of the shield tunneling face includes a spiral failure mechanism and a translational failure mechanism; wherein the translational failure mechanism is a plane area composed of point A, point B and point F, and the translational failure mechanism is at point A with a velocity vector For translation, The angle with the horizontal is α; the spiral failure mechanism and the translation failure mechanism are transitioned through the velocity discontinuity surface AF, and a point O is arbitrarily set as the rotation center of the spiral failure mechanism, which rotates clockwise at an angular velocity ω through points O' and A, and the failure boundaries AO' and O'F are logarithmic spirals; The distance from the groundwater level to the top of the shield tunnel is h w ; Under the condition that the seepage during tunnel excavation will not cause the groundwater level to drop, the boundary condition of the groundwater level is set to h = h0, where h0 is the groundwater level elevation; when the tunnel end face is under normal pressure, the excavation face is a fixed pressure head Tunnel head difference Δh=h w -h F , considering the pore water pressure u as acting on the soil skeleton and the permissible velocity field v i Therefore, in the instability failure mechanism of the shield tunneling face, u acts on the failure boundaries AF, BF, AO' and O'F, r u is the pore water pressure coefficient.

4. The shield tunneling face instability calculation method considering seepage according to claim 3 is characterized by: In S3, the effective support pressure σ is obtained t1 The method of ' is as follows: S31: Considering the effect of pore water pressure on the shield tunneling face, for any permissible velocity field v i and the strain rate field ε ij , the shield tunneling face structure is in a stable state, and the system dissipated power P v And the actual external force work power P e The following constraints are met: P v ≥P e in, is the strain energy per unit volume, is the internal strain rate tensor of the strain body, Ω is the structural volume, S is the boundary volume of the failure mechanism, T i is the traction force vector on the strain body boundary S, γ i is the weight vector, n i is the normal vector perpendicular to the failure surface, and the work done by the pore water pressure is S32: Based on the empirical seepage model of the excavation face, under the constraints, let and h F = 0, according to the empirical model of seepage at the excavation face, the work power of the pore water pressure u acting on the boundary surfaces AF, BF, AO', O'F is calculated to obtain the pore water pressure work power P u ; S33: The sum of the energy dissipation power P on the destruction boundaries AF, BF, O'F, AO' v =P u +P γ +P σt1 , based on the pore water pressure work power P u and soil gravity power P γ , and the effective support pressure power is obtained S34: Based on the effective support pressure power The effective support pressure σ is calculated as t1 ′.

5. The shield tunneling face instability calculation method considering seepage according to claim 4 is characterized by: The pore water pressure work power P u The calculation formula is: P u =P uAO′ +P uO′F +P uAF +P uBF Among them, P uAO′ is the work power of pore water pressure u acting on the boundary surface AO', P uO′F is the work done by the pore water pressure u on the boundary surface O'F, P uAF is the work done by the pore water pressure u on the boundary surface AF, P uBF is the work power of pore water pressure u acting on the boundary surface BF; The pore water pressure u acts on the boundary surface AO' to do work P uAO′ The calculation method is as follows: Let n i =1, u=r u γ′h AO′ , the work power P of the pore water pressure u acting on the boundary surface AO' is obtained uAO′ : The pore water pressure u acts on the boundary surface O'F to do work P uO′F The calculation method is as follows: Let n i =1, u=r u γ′h O′F , the work power P of the pore water pressure u acting on the boundary surface O'F is obtained uO′F : The work power P of the pore water pressure u acting on the boundary surface AF uAF The calculation method is as follows: Let n i =1, u=r u γ′h AF , the work power P of the pore water pressure u acting on the boundary surface AF is obtained uAF : The pore water pressure u acts on the boundary surface BF to do work P uBF The calculation method is as follows: Let n i =1, u=r u γ′h BF , the work power P of the pore water pressure u acting on the boundary surface BF is obtained uBF : Among them, v AO′ is the velocity of any point on AO′, x AO′ is the horizontal coordinate of any point on AO′; v O′F is the velocity of any point on O'F, x O′F is the horizontal coordinate of any point on O'F; v AF is the speed of any point on AF, x AF is the horizontal coordinate of any point on AF; v BF is the velocity of any point on BF, x BF is the horizontal coordinate of any point on BF.

6. The shield tunneling face instability calculation method considering seepage according to claim 4 is characterized by: The effective support pressure power The support force σ on the excavation face t ′1 can be expressed as: in, is the excavation face support force vector, v1 is Model.

7. The shield tunneling face instability calculation method considering seepage according to claim 6 is characterized by: The soil gravity power P γ The calculation formula is: Among them, x F is the horizontal coordinate of point F, θ F is the angle between OF and the vertical direction, θ O′ is the angle between OO′ and the vertical direction, r F is the OF length, r A is the OA length, θ A is the angle between OA and the vertical direction.

8. The shield tunneling face instability calculation method considering seepage according to claim 7 is characterized by: The effective support pressure σ t1 The calculation formula of ′ is as follows: Among them, N γ1 、N c1 、N u are transition variables. v 12,i is the relative velocity vector, r BF is the distance from any point on BF to point O, x BF is the horizontal coordinate of any point on BF, x BO′ for; r AO′ is the distance from any point on AO′ to point O, r FO′ is the distance from any point on FO′ to point O, P i For any known point on AF′, P i+1 is the next generation point, P i P i+1 =s, s is the discrete length.

9. A shield tunneling face instability calculation system considering seepage, characterized in that: The system is used to execute the steps of the shield tunneling face instability calculation method considering seepage as described in any one of claims 1 to 8, and includes the following modules: An empirical model acquisition module, which is used to extract the pressure head value of each coordinate in front of the excavation face based on the seepage field in front of the shield tunneling face, perform numerical fitting on all the pressure head values, and obtain an empirical model of seepage in the tunneling face; A failure mechanism construction module, wherein the failure mechanism construction module is used to construct an instability failure mechanism of a shield tunneling face based on the tunneling face seepage empirical model; An effective support pressure calculation module is used to obtain the effective support pressure based on the instability and failure mechanism of the shield tunneling face.

10. A computer storage medium, characterized in that: The computer storage medium stores a computer software product, which includes a number of instructions for enabling a computer device to execute the method for calculating the instability of a shield tunneling face taking into account seepage as described in any one of claims 1 to 8.

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