A method for reinforcing design of stratum partition of butt joint section of shield tunnel

Abstract

The present application relates to geotechnical engineering curtain grouting-freezing technical field, disclose a kind of shield tunnel ground butt joint section stratum partition reinforcement design method, including the butt joint strong permeation stratum is divided into contact seepage isolation zone, free face self-stabilizing anti-seepage zone, core bearing area and frost heaving thawing and sinking improvement zone;Determine the grouting layer thickness and grouting layer length of contact seepage isolation zone;Determine the grouting layer thickness and grouting layer length of free face self-stabilizing anti-seepage zone;According to target frozen soil thickness, determine the frozen soil layer thickness of core bearing area;Based on freezing thickness, frost heaving rate and thawing rate, combined with frost heaving inhibition coefficient and thawing correction coefficient, calculate frost heaving amount and thawing amount, and according to frost heaving amount and thawing amount, determine the freezing reinforcement thickness of frost heaving thawing and sinking improvement zone.The present application can effectively reduce the seepage flow, solve the structure stability and seepage control problem in high permeability stratum butt joint.

Description

Technical Field

[0001] This invention relates to the field of curtain grouting-freezing technology in geotechnical engineering, and more specifically, to a method for zonal reinforcement design of the underground docking section of a shield tunnel. Background Technology

[0002] In the underground docking construction of shield tunnels, highly permeable strata face core challenges such as frost heave deformation, contact seepage, stratum disturbance, and insufficient bearing capacity. Single freezing methods are prone to threatening the structural stability of the shield body due to frost heave force (9% frost heave rate), and thermal disturbance of the cutterhead can cause spalling and seepage in weakly frozen areas. Single grouting methods are difficult to form a reliable water-stop curtain due to high water pressure seepage, and the bearing capacity of the grout lacks quantitative design standards. Existing technologies cannot simultaneously meet the requirements for impermeability, frost heave resistance, structural stability, and thermal interference control. A synergistic reinforcement method is urgently needed to address seepage isolation, free face self-stabilization, bearing capacity optimization, and frost heave-thaw settlement suppression in complex strata.

[0003] Domestic and international scholars have conducted relevant research on the reinforcement of the surrounding rock and soil of shield tunneling connections. For example, patent application number CN202510568238.2 discloses a reinforcement device and method for the surrounding rock of shield tunneling connections in a high-pressure, water-rich environment. This device can quickly adjust the freezing pipe layout strategy, effectively reducing the time cost increase and construction delays caused by changes in the plan. Patent application number CN202411673739.9 discloses a grouting reinforcement device and its construction method for the middle of shield tunneling connections. Its high-pressure grouting equipment injects cement grout into the gaps in the rock and soil around the tunnel, effectively forming a stable and safe reinforcement zone. Patent application number CN202411565283.4 discloses a method based on shield tunneling connections. The in-situ testing method of curtain grouting achieves complete grout looping by designing the number and length of curtain grouting pipelines, and uses the minimum number of curtain grouting pipelines to ensure that the grouting reinforcement range of the surrounding rock meets the design requirements. Another example is the patent application CN202310787998.3, which discloses an underwater docking reinforcement method in high-water-pressure, highly permeable strata. This method uses curtain grouting-freezing to form a stable reinforcement zone, providing a stable water-proof boundary for tunnel breakthrough excavation. The patent application CN202310150990.6 discloses a construction method for underground docking of shield tunnels in highly permeable sandy strata. This method uses curtain freezing to reinforce the surrounding soil and rock of the shield docking area, reducing the risk of instability and water seepage at the docking section excavation face.

[0004] While existing research has disclosed a small number of related technical achievements, most focus on upgrading and improving the surrounding soil and rock reinforcement devices. Even though some research results have disclosed methods or technologies for reinforcing the surrounding soil and rock in the docking section during shield tunneling, they have not defined the detailed regional division of the stratum reinforcement system and the role of each region. This results in a lack of targeted technical support for the stratum reinforcement effect and faces the following technical challenges:

[0005] 1) Welding and cutting operations are required during the reinforcement and excavation of the shield body in the shield docking section, which releases a lot of heat. Due to the high thermal conductivity of steel, the heat generated by welding and cutting can easily cause the interface between the shield shell and the frozen soil to melt, forming a seepage channel. There is a risk of leakage during the tunneling and excavation of the docking shield.

[0006] 2) Due to the disturbance caused by the excavation of the connecting shield tunnel, the strength and impermeability of the frozen soil at the cut location are weakened, and there is a possibility of rockfall or even leakage and instability, which brings huge construction safety risks and a huge psychological burden to the construction personnel.

[0007] 3) The design reinforcement scope of frozen soil is mostly based on empirical considerations and does not provide clear numerical and theoretical support.

[0008] 4) The subsequent frost heave and thaw settlement effect was not considered during the reinforcement process, which resulted in drawbacks in the reinforcement method.

[0009] No effective solutions have yet been proposed to address the problems in the relevant technologies. Summary of the Invention

[0010] To address the problems in related technologies, this invention proposes a method for zonal reinforcement of the ground strata in the underground docking section of a shield tunnel, in order to overcome the aforementioned technical problems existing in the existing related technologies.

[0011] Therefore, the specific technical solution adopted by the present invention is as follows:

[0012] A method for zoned reinforcement of the ground strata in the underground docking section of a shield tunnel includes the following steps:

[0013] S1. Based on the preset reinforcement requirements, the highly permeable strata in the shield tunnel are divided into the contact seepage isolation zone, the free face self-stabilizing seepage prevention zone, the core bearing zone, and the frost heave and thaw settlement improvement zone.

[0014] S2. Based on the temperature diffusion radius and melting zone radius, the thickness of the grouting layer in the contact seepage isolation zone is determined by combining the correction coefficient, and the length of the grouting layer in the contact seepage isolation zone is determined according to the length of the docking shield, the width of the docking shield cut, and the preset reduction coefficient.

[0015] S3. Based on the target thicknesses for bending and shear control, determine the thickness of the grouting layer in the self-stabilizing seepage prevention zone of the free face, and based on the cut width and overlap length of the connecting shield, determine the length of the grouting layer in the self-stabilizing seepage prevention zone of the free face.

[0016] S4. Convert the frozen soil section into an equivalent grouting section. Based on the equivalent grouting section, calculate the target frozen soil thickness by combining the bending bearing capacity, shear bearing capacity, and deformation control. Determine the frozen soil layer thickness of the core bearing area based on the target frozen soil thickness.

[0017] S5. Based on the freezing thickness, frost heave rate and thaw settlement rate, calculate the frost heave amount and thaw settlement amount by combining the frost heave inhibition coefficient and thaw settlement correction coefficient, and determine the freezing reinforcement thickness of the frost heave and thaw settlement improvement zone according to the frost heave amount and thaw settlement amount.

[0018] Furthermore, the step of dividing the highly permeable strata in the shield tunnel into a contact seepage isolation zone, a self-stabilizing seepage prevention zone at the free face, a core bearing zone, and a frost heave and thaw settlement improvement zone according to the preset reinforcement requirements includes the following steps:

[0019] S11. The interface between the shield and the frozen soil is divided into a contact seepage isolation zone to isolate the seepage channels formed by the melting of frozen soil due to ambient temperature and local hot work.

[0020] S12. Divide the excavation outline area of ​​the shield docking cutterhead into a free-face self-stabilizing seepage prevention zone to provide self-support and waterproofing when the excavation is exposed, and prevent rockfall and water seepage.

[0021] S13. Divide the main frozen wall formed by artificial freezing into a core load-bearing zone to provide key load-bearing capacity and overall water-stop curtain;

[0022] S14. Improve the soil around the frozen zone by infiltration grouting to create a frost heave and thaw settlement improvement zone, so as to suppress frost heave and thaw settlement deformation during freezing and thawing.

[0023] Furthermore, the determination of the grouting layer thickness in the contact seepage isolation zone based on the temperature diffusion radius and melting zone radius, combined with a correction coefficient, and the determination of the grouting layer length in the contact seepage isolation zone according to the length of the docking shield, the width of the docking shield cut, and a preset reduction coefficient includes the following steps:

[0024] S21. Solve the temperature field based on the radial steady-state heat conduction of the multi-layer material cylindrical wall to determine the temperature distribution of each layer of material and obtain the temperature at any position of each layer of material.

[0025] S22. Determine the temperature diffusion radius based on the temperature at any location of each layer of material and the location of the freezing point, and solve the transient temperature field under the conduction of a single heat source in a multi-layered flat plate material.

[0026] S23. Select the maximum value of the temperature diffusion radius and the melting zone radius under the transient temperature field as the initial grouting layer thickness, and combine the correction coefficient to correct the initial grouting layer thickness to obtain the corrected grouting layer thickness of the contact seepage isolation zone.

[0027] S24. Determine the length of the grouting layer in the contact seepage isolation zone based on the length of the docking shield, the width of the docking shield cut, and the preset reduction coefficient.

[0028] Furthermore, the expression for the temperature at any location in each material layer is as follows:

[0029] ;

[0030] ;

[0031] ;

[0032] The revised expression for the grouting layer thickness in the contact seepage isolation zone is:

[0033] ;

[0034] d1 = Max[r, K];

[0035] ;

[0036] ;

[0037] The expression for the length of the grouting layer in the contact seepage isolation zone is:

[0038] L1 = 2 × ω × L C +L D ;

[0039] In the formula, T r T represents the temperature at any location in the i-th layer of material. i T represents the inner surface temperature of the i-th layer of material. i+1 Let r represent the outer surface temperature of the i-th layer of material, and r represent the temperature diffusion radius. i Let r represent the inner radius of the i-th layer of material. i+1 Let R represent the outer radius of the i-th layer of material, Q represent the total heat flux of the material, and R represent the total heat flux of the material. i λ represents the radial thermal resistance of the i-th layer material. i Let d represent the thermal conductivity of the i-th layer of material, L represent the material length, and d represent the thermal conductivity of the i-th layer of material. 1xz The corrected grout layer thickness for the contact seepage isolation zone, γ represents the correction coefficient, d1 represents the initial grout layer thickness, Max[r, K] represents the maximum value between the temperature diffusion radius r and the melting zone radius K, t represents time, ρ represents material density, C represents material specific heat, ΔT represents temperature difference, J represents the latent heat of fusion of the material, L1 represents the grout layer length for the contact seepage isolation zone, ω represents the reduction coefficient, L C L represents the length of the docking shield. D This indicates the width of the cut in the shield tunnel.

[0040] Furthermore, determining the grouting layer thickness of the self-stabilizing seepage prevention zone of the free face based on the target thicknesses for bending and shear control, and determining the grouting layer length of the self-stabilizing seepage prevention zone of the free face based on the cut width and overlap length of the connecting shield tunnel, includes the following steps:

[0041] S31. Based on the material properties and test results of the grouting layer, determine the flexural strength and shear strength of the grouting body in the self-stabilizing seepage prevention zone of the free face;

[0042] S32. Based on the self-stability under construction disturbance and vibration, combined with the dynamic load coefficient and the weight of locally melted water storage, calculate the maximum bending moment and maximum shear force of the grouting body in the self-stabilizing seepage prevention zone of the free face.

[0043] S33. Based on the bending stress calculation and shear stress calculation, combined with the maximum bending moment and maximum shear force of the grouting body, determine the minimum thickness for bending resistance control and the minimum thickness for shear resistance control of the self-stabilizing seepage prevention zone on the free face.

[0044] S34. Select the maximum value of the minimum thickness for bending control and the minimum thickness for shear control as the grouting layer thickness of the self-stabilizing seepage prevention zone of the free face, and determine the length of the grouting layer of the self-stabilizing seepage prevention zone of the free face in combination with the width of the shield cut and the overlap length.

[0045] Furthermore, the expressions for the maximum bending moment and maximum shear force of the grouting body in the self-stabilizing seepage prevention zone of the free face are as follows:

[0046] ;

[0047] ;

[0048] The expression for the thickness of the grouting layer in the self-stabilizing seepage prevention zone of the free face is:

[0049] d2=Max[t M , t V ];

[0050] ;

[0051] ;

[0052] The expression for the length of the grouting layer in the self-stabilizing seepage prevention zone of the free face is:

[0053] L2=L D +2ψ;

[0054] In the formula, M max V represents the maximum bending moment of the grouting body in the self-stabilizing seepage prevention zone of the free face. max ξ represents the maximum shear force of the grouting body in the self-stabilizing seepage prevention zone of the free face, and q represents the dynamic load coefficient. s q represents the weight of the water stored during partial melting. t L represents the weight of the grouting body in the self-stabilizing seepage prevention zone of the free face. D d1 represents the width of the shield tunnel cut, d2 represents the thickness of the grouting layer in the self-stabilizing seepage prevention zone of the free face, and Max[t] represents the thickness of the grouting layer in the self-stabilizing seepage prevention zone of the free face. M , t V] indicates the selection of t M and t V The maximum value in t M This represents the minimum thickness (t) of the self-stabilizing seepage prevention zone on the free face for flexural resistance control. V [σ] represents the minimum thickness of the shear control of the self-stabilized seepage prevention zone of the free face, [τ] represents the bending strength of the grout in the self-stabilized seepage prevention zone of the free face, [τ] represents the shear strength of the grout in the self-stabilized seepage prevention zone of the free face, L2 represents the length of the grout layer in the self-stabilized seepage prevention zone of the free face, and ψ represents the overlap length.

[0055] Furthermore, the process of converting the frozen soil cross-section into an equivalent grouting body cross-section, calculating the target frozen soil thickness based on the equivalent grouting body cross-section, combined with flexural bearing capacity, shear bearing capacity, and deformation control, and determining the frozen soil layer thickness of the core bearing zone based on the target frozen soil thickness includes the following steps:

[0056] S41. Determine the maximum bending moment and maximum shear force in the core bearing area based on the external load, and convert the frozen soil section into an equivalent grouting section with constant thickness and preset width; based on the converted equivalent grouting section, calculate the position of the centroidal axis and moment of inertia of the equivalent section;

[0057] S42. Based on the bending bearing capacity, shear bearing capacity and deformation control, calculate the minimum frozen soil thickness for bending control, shear control and deformation control, and select the maximum value of the minimum frozen soil thickness for bending control, shear control and deformation control as the frozen soil layer thickness of the core bearing area.

[0058] Among them, when the bending stress equation is equal to the bending strength of the frozen soil, the minimum thickness of the frozen soil for bending control in the core bearing area is determined.

[0059] When the shear stress equation is equal to the shear strength of the frozen soil, determine the minimum thickness of the frozen soil that controls the shear strength of the core bearing zone;

[0060] When the deflection equation equals the allowable deflection of the grouting body, determine the minimum frozen soil thickness for deformation control in the core bearing zone.

[0061] Furthermore, the expressions for the maximum bending moment and maximum shear force in the core bearing area are:

[0062] ;

[0063] ;

[0064] The expressions for the position of the centroidal axis and the moment of inertia of the equivalent cross section are:

[0065] ;

[0066] ;

[0067] The expressions for the equations of bending stress, shear stress, and deflection are as follows:

[0068] ;

[0069] ;

[0070] ;

[0071] The expression for the thickness of the permafrost layer in the core bearing area is:

[0072] d3=Max[h f1 h f2 h f3 ];

[0073] In the formula, M m V represents the maximum bending moment in the core load-bearing area. m q represents the maximum shear force in the core bearing area. z L represents the total external soil and water load. D Indicates the width of the cut in the tunnel boring machine, y c h represents the distance from the centroidal axis of the equivalent cross section to the lower edge of the cross section. g E represents the thickness of the grouting layer in the self-stabilizing seepage prevention zone of the free face. f E represents the elastic modulus of frozen soil. g h represents the elastic modulus of the grout. f I represents the calculated thickness of the frozen soil mass. e I represents the equivalent moment of inertia of the cross section. f I represents the moment of inertia of the frozen soil section. g σ represents the moment of inertia of the grouting body cross section. f y represents the compressive stress at the top of the frozen soil mass. t [f] represents the distance from the centroidal axis of the equivalent cross section to the top surface of the frozen soil mass. f ] represents the flexural strength of frozen soil, τ f Represents the shear stress in frozen soil, [τ] f The shear strength of frozen soil, S represents the static moment of the equivalent section above or below the centroidal axis of the equivalent section about the centroidal axis of the equivalent section, δ represents the deflection, [δ] represents the allowable deflection of the grouting body, d3 represents the thickness of the frozen soil layer in the core bearing zone, Max[h f1 h f2 h f3 ] indicates selecting h f1 h f2 h f3 The maximum value in, h f1 h represents the minimum frozen soil thickness for bending resistance control. f2 h represents the minimum thickness of frozen soil mass that controls shear strength. f3This indicates the minimum thickness of the frozen soil body for deformation control.

[0074] Furthermore, the calculation of frost heave and thaw settlement based on freezing thickness, frost heave rate, and thaw settlement rate, combined with frost heave inhibition coefficient and thaw settlement correction coefficient, and the determination of freezing reinforcement thickness of the frost heave and thaw settlement improvement zone based on frost heave and thaw settlement include the following steps:

[0075] S51. Calculate the amount of frost heave based on the freezing thickness and frost heave rate, combined with the frost heave inhibition coefficient, and determine the amount of thaw settlement based on the thaw settlement rate, freezing thickness, and thaw settlement correction coefficient.

[0076] S52. Select the maximum value of frost heave and thaw settlement as the freezing reinforcement thickness of the frost heave and thaw settlement improvement zone.

[0077] Furthermore, the expression for frost heave is:

[0078] A = a × η × H;

[0079] H=d 1xz +d3;

[0080] The expression for the amount of sediment is:

[0081] B=β× ×H;

[0082] The expression for the thickness of the freeze reinforcement in the frost heave and thaw settlement improvement zone is:

[0083] d4 = Max[A, B];

[0084] In the formula, A represents the frost heave amount, α represents the frost heave inhibition coefficient, η represents the frost heave rate, H represents the frozen thickness, and d 1xz The corrected thickness of the grouting layer in the contact seepage isolation zone, d3 represents the thickness of the frozen soil layer in the core bearing zone, B represents the thaw settlement, and β represents the thaw settlement correction factor. d4 represents the thaw settlement rate, d4 represents the thickness of the frozen reinforcement in the frost heave and thaw settlement improvement zone, and Max[A, B] represents the maximum value of A and B.

[0085] The beneficial effects of this invention are as follows:

[0086] 1) This invention pioneered the four-zone design concept for the shield tunnel docking reinforcement zone, with clear functions, which solves the inherent defects of a single construction method.

[0087] 2) This invention provides calculation methods and formulas for key design indicators (thickness, length, strength, temperature) for each zone, elevating the design from experience to the level of theoretical calculation.

[0088] 3) This invention greatly improves the safety and reliability of underground docking through thermo-mechanical multi-field coupling analysis, especially the quantitative evaluation of the thermal insulation effect and bearing capacity of the grouting layer.

[0089] 4) This invention improves grouting in Zone IV, effectively suppressing frost heave and thaw settlement, and reducing the impact on the surrounding environment. Attached Figure Description

[0090] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0091] Figure 1 This is a schematic diagram of the zonal reinforcement of the shield tunnel underground docking section in an embodiment of the present invention.

[0092] Figure 2 This is a schematic diagram of the frozen soil section conversion process in a ground zoning reinforcement design method for the underground docking section of a shield tunnel according to an embodiment of the present invention. Detailed Implementation

[0093] To further illustrate the various embodiments, the present invention provides accompanying drawings, which are part of the disclosure of the present invention. These drawings are mainly used to illustrate the embodiments and can be used in conjunction with the relevant descriptions in the specification to explain the operating principles of the embodiments. With reference to these drawings, those skilled in the art should be able to understand other possible implementation methods and the advantages of the present invention. The components in the drawings are not drawn to scale, and similar component symbols are generally used to represent similar components.

[0094] According to an embodiment of the present invention, a method for zonal reinforcement design of the ground strata in the underground docking section of a shield tunnel is provided.

[0095] This invention addresses the aforementioned problems and shortcomings of existing technologies by employing a "grouting-freezing" composite reinforcement method. The reinforced area is divided into four functional zones: Zone I (contact seepage isolation zone), Zone II (self-stabilizing seepage prevention zone on the free surface), Zone III (core load-bearing zone), and Zone IV (frost heave and thaw settlement improvement zone). This method solves four key technical problems: thermal interference, load-bearing capacity, water sealing, and frost heave and thaw settlement. By combining temperature control equations and thermal resistance calculations, the steady-state and transient heat conduction problems of the multi-layered cylindrical wall (shield-grouting layer-frozen soil) are solved, determining the location of the thaw line and the thickness of the grouting layer in Zone I. Furthermore, through seepage calculations, the significant difference in seepage flow before and after grouting in Zone I is quantitatively analyzed, proving the effectiveness of grouting insulation. Based on structural strength verification results, the reinforcement thickness and length parameters for Zones II and III are determined. Finally, considering the frost heave and thaw settlement effect and the influence mechanism of permeable grouting, the permeable grouting range is determined.

[0096] The present invention will now be further described in conjunction with the accompanying drawings and specific embodiments, such as... Figures 1-2 As shown, the method for zonal reinforcement design of the underground docking section of a shield tunnel according to an embodiment of the present invention includes the following steps:

[0097] S1. Based on the preset reinforcement requirements, the highly permeable strata in the shield tunnel are divided into the contact seepage isolation zone, the free face self-stabilizing seepage prevention zone, the core bearing zone, and the frost heave and thaw settlement improvement zone.

[0098] The step of dividing the highly permeable strata in the shield tunnel into a contact seepage isolation zone, a self-stabilizing seepage prevention zone at the free face, a core bearing zone, and a frost heave and thawing settlement improvement zone according to preset reinforcement requirements includes the following steps:

[0099] S11. The area where the shield body meets the frozen soil is divided into Zone I (contact seepage isolation zone). Its main function is to isolate the seepage channels formed by the melting of frozen soil due to ambient temperature and local hot work.

[0100] S12. The area near the cutterhead of the shield tunneling machine is divided into Zone II (self-stabilizing and seepage-proof zone on the free face). Its main function is to provide self-support and waterproofing when the excavation is exposed, and to prevent rockfall and water seepage.

[0101] S13. The main frozen wall formed by artificial freezing is divided into Zone III (core load-bearing zone), whose main function is to provide the main load-bearing capacity and the overall water-stop curtain.

[0102] S14. Zone IV (frost heave and thaw settlement improvement zone) is established by permeation grouting to improve the soil outside the frozen zone. Its main function is to suppress frost heave and thaw settlement deformation during freezing and thawing.

[0103] Specifically, such as Figure 1 The diagram shows the reinforcement of different areas for the underground docking of the shield tunnel. Figure 1 The four zones are divided as follows: Zone I: When the shield machine is stopped, radial grouting and advance grouting are used to fill the gaps around the shield body to form a grout encapsulation effect; Zone II: The shield slurry chamber is filled with mortar and curtain grouting is used to reinforce the docking cut and the large area of ​​rock and soil around the shield body; Zone III: Curtain freezing is used to apply freezing technology within the curtain grouting area to further reinforce the rock and soil around the shield body; Zone IV: The outermost part of the freezing area to the outermost part of the curtain grouting area is used as the freezing stress effect release area and the frost heave and thaw settlement improvement area.

[0104] S2. Based on the temperature diffusion radius and melting zone radius, the thickness of the grouting layer in the contact seepage isolation zone is determined by combining the correction coefficient, and the length of the grouting layer in the contact seepage isolation zone is determined according to the length of the docking shield, the width of the docking shield cut, and the preset reduction coefficient.

[0105] The process of determining the grouting layer thickness of the contact seepage isolation zone based on the temperature diffusion radius and melting zone radius, combined with a correction coefficient, and determining the grouting layer length of the contact seepage isolation zone according to the length of the docking shield, the width of the docking shield cut, and a preset reduction coefficient includes the following steps:

[0106] S21. Solve the temperature field based on the radial steady-state heat conduction of the multi-layer material cylindrical wall to determine the temperature distribution of each layer of material and obtain the temperature at any position of each layer of material.

[0107] Specifically, the radial thermal resistance of each layer of material is determined based on the thermal conductivity, diffusion radius, and material length:

[0108] ;

[0109] Determine the interface temperature of each material layer based on the total heat flow rate and radial thermal resistance:

[0110] ;

[0111] Determine the temperature T at any location in each layer of material. r :

[0112] ;

[0113] In the formula, T r T represents the temperature at any location in the i-th layer of material. i T represents the inner surface temperature of the i-th layer of material. i+1 Let r represent the outer surface temperature of the i-th layer of material, and r represent the temperature diffusion radius. i Let r represent the inner radius of the i-th layer of material. i+1 Let R represent the outer radius of the i-th layer of material, Q represent the total heat flux of the material, and R represent the total heat flux of the material. i λ represents the radial thermal resistance of the i-th layer material. i Let L represent the thermal conductivity of the i-th layer of material, and L represent the length of the material.

[0114] S22. Based on the temperature at any location of each layer of material, combined with the freezing point temperature (T) r =0) Determine the temperature diffusion radius and solve the transient temperature field under the conduction of a single heat source in a multi-layered flat plate material;

[0115] Specifically, calculate the temperature diffusion radius:

[0116] ;

[0117] Determine the radius of the melting zone under a transient temperature field based on the law of energy conservation:

[0118] ;

[0119] In the formula, K represents the radius of the melting zone, t represents time, ρ represents the material density, C represents the specific heat of the material, ΔT represents the temperature difference, and J represents the latent heat of fusion of the material.

[0120] S23. Select the maximum value of the temperature diffusion radius and the melting zone radius under the transient temperature field as the initial grouting layer thickness. Consider the influence of theoretical deviation, correct the initial grouting layer thickness, introduce a correction coefficient, and combine the correction coefficient to correct the initial grouting layer thickness to obtain the corrected grouting layer thickness of the contact seepage isolation zone.

[0121] Specifically, the revised expression for the thickness of the grouting layer in the contact seepage isolation zone is as follows:

[0122] ;

[0123] d1 = Max[r, K];

[0124] In the formula, d 1xz The corrected grouting layer thickness of the contact seepage isolation zone, γ represents the correction coefficient, with a value range of 1.1~1.2, d1 represents the initial grouting layer thickness, and Max[r, K] represents the selected temperature diffusion radius r and melting zone radius;

[0125] S24. Determine the length of the grouting layer in the contact seepage isolation zone based on the length of the docking shield, the width of the docking shield cut, and the preset reduction coefficient.

[0126] Specifically, the expression for the length of the grouting layer in the contact seepage isolation zone is:

[0127] L1 = 2 × ω × L C +L D ;

[0128] In the formula, L1 represents the length of the grouting layer in the contact seepage isolation zone, ω represents the reduction factor, and its value ranges from 2 / 3 to 3 / 4. C L represents the length of the docking shield. D This indicates the width of the cut in the shield tunnel.

[0129] S3. Based on the target thicknesses for bending and shear control, determine the thickness of the grouting layer in the self-stabilizing seepage prevention zone of the free face, and based on the cut width and overlap length of the connecting shield, determine the length of the grouting layer in the self-stabilizing seepage prevention zone of the free face.

[0130] The process of determining the grouting layer thickness of the self-stabilizing seepage prevention zone of the free face based on the target thicknesses for bending and shear control, and determining the grouting layer length of the self-stabilizing seepage prevention zone of the free face based on the cut width and overlap length of the connecting shield tunnel, includes the following steps:

[0131] S31. Based on the material properties and test results of the grouting layer, determine the flexural strength and shear strength of the grouting body in the self-stabilizing seepage prevention zone of the free face;

[0132] S32. Based on the self-stability under construction disturbance and vibration, combined with the dynamic load coefficient and the weight of locally melted water storage, calculate the maximum bending moment and maximum shear force of the grouting body in the self-stabilizing seepage prevention zone of the free face.

[0133] Specifically, the expressions for the maximum bending moment and maximum shear force of the grouting body in the self-stabilizing seepage prevention zone of the free face are as follows:

[0134] ;

[0135] ;

[0136] In the formula, M max V represents the maximum bending moment of the grouting body in the self-stabilizing seepage prevention zone of the free face. max ξ represents the maximum shear force of the grouting body in the self-stabilizing seepage prevention zone of the free face, and q represents the dynamic load coefficient. s q represents the weight of the water stored during partial melting. t This indicates the weight of the grout in the self-stabilizing seepage prevention zone of the free face;

[0137] S33. Based on the bending stress calculation and shear stress calculation, combined with the maximum bending moment and maximum shear force of the grouting body, determine the minimum thickness for bending resistance control and the minimum thickness for shear resistance control of the self-stabilizing seepage prevention zone on the free face.

[0138] Specifically, the thickness range of the grouting body in the self-stabilizing seepage prevention zone of the free face is determined based on bending stress and shear stress calculations under the most unfavorable internal force conditions.

[0139] ;

[0140] ;

[0141] In the formula, t M This represents the minimum thickness (t) of the self-stabilizing seepage prevention zone on the free face for flexural resistance control. V [σ] represents the minimum thickness of the shear control of the self-stabilized seepage prevention zone of the free face, [τ] represents the flexural strength of the grout in the self-stabilized seepage prevention zone of the free face, and [τ] represents the shear strength of the grout in the self-stabilized seepage prevention zone of the free face.

[0142] S34. Select the maximum value of the minimum thickness for bending control and the minimum thickness for shear control as the grouting layer thickness of the self-stabilizing seepage prevention zone of the free face, and determine the length of the grouting layer of the self-stabilizing seepage prevention zone of the free face in combination with the width of the shield cut and the overlap length.

[0143] Specifically, the expression for the thickness of the grouting layer in the self-stabilizing seepage prevention zone of the free face is:

[0144] d2=Max[tM , t V ];

[0145] The expression for the length of the grouting layer in the self-stabilizing seepage prevention zone of the free face is:

[0146] L2=L D +2ψ;

[0147] In the formula, d2 represents the thickness of the grouting layer in the self-stabilizing seepage prevention zone of the free face. In this embodiment, d2 = h g Max[t] M , t V ] indicates the selection of t M and t V The maximum value in L2 represents the length of the grouting layer in the self-stabilizing seepage prevention zone of the free face, and ψ represents the overlap length, with a value range of 0.3~0.4.

[0148] S4. Convert the frozen soil section into an equivalent grouting section. Based on the equivalent grouting section, calculate the target frozen soil thickness by combining the bending bearing capacity, shear bearing capacity, and deformation control. Determine the frozen soil layer thickness of the core bearing area based on the target frozen soil thickness.

[0149] The process of converting the frozen soil cross-section into an equivalent grouting body cross-section, calculating the target frozen soil thickness based on the equivalent grouting body cross-section, combined with flexural bearing capacity, shear bearing capacity, and deformation control, and determining the frozen soil layer thickness of the core bearing zone based on the target frozen soil thickness includes the following steps:

[0150] S41. Determine the maximum bending moment and maximum shear force in the core bearing area based on the external load, and convert the frozen soil section into an equivalent grouting section with constant thickness and preset width; based on the converted equivalent grouting section, calculate the position of the centroidal axis and moment of inertia of the equivalent section;

[0151] The equivalent section represents the cross-section of the grouting-freezing body after the overall equivalent treatment, such as... Figure 2 The entire cross-section on the right, the equivalent grouting body cross-section represents the cross-section of the upper frozen body as an equivalent grouting body, such as... Figure 2 Grouting body in the upper right half.

[0152] Specifically, the most unfavorable internal force (maximum bending moment M) is determined based on the external load. m Maximum shear force V m And satisfy the following relationship:

[0153] ;

[0154] ;

[0155] In the formula, M m V represents the maximum bending moment in the core load-bearing area.m q represents the maximum shear force in the core bearing area. z This represents the total external soil and water load;

[0156] The grouting-frozen soil serves as the core load-bearing structure of the core bearing area. However, due to the difference in elastic modulus between the grouting and frozen soil, the bearing capacity and deformation calculations require equivalent section conversion. Figure 2 The cross-section of the frozen soil was adjusted to have a constant thickness and a width of L. D *E f / E g The equivalent grouting body cross section;

[0157] The position of the centroidal axis of the equivalent section and the moment of inertia are calculated according to the following relationship:

[0158] ;

[0159] ;

[0160] In the formula, y c h represents the distance from the centroidal axis of the equivalent cross section to the lower edge of the cross section. g E represents the thickness of the grouting layer in the self-stabilizing seepage prevention zone of the free face. f E represents the elastic modulus of frozen soil. g h represents the elastic modulus of the grout. f This represents the calculated thickness of the frozen soil mass, which is a preliminary calculated thickness. e I represents the equivalent moment of inertia of the cross section. f I represents the moment of inertia of the frozen soil section. g The moment of inertia of the grouting body section is represented by the distance from the centroidal axis of the equivalent section to the lower edge of the section.

[0161] S42. Based on the bending bearing capacity, shear bearing capacity and deformation control, calculate the minimum frozen soil thickness for bending control, shear control and deformation control, and select the maximum value of the minimum frozen soil thickness for bending control, shear control and deformation control as the frozen soil layer thickness of the core bearing area.

[0162] Specifically, the minimum frozen soil thickness is determined by controlling the flexural bearing capacity, shear bearing capacity, and deformation:

[0163] When the bending stress equation equals the bending strength of the frozen soil, the minimum frozen soil thickness controlled by the bending resistance of the core bearing zone is determined by computer:

[0164] ;

[0165] In the formula, σ f y represents the compressive stress at the top of the frozen soil mass. t[f] represents the distance from the centroidal axis of the equivalent cross section to the top surface of the frozen soil mass. f [Indicates the flexural strength of frozen soil;]

[0166] When the shear stress equation equals the shear strength of the frozen soil, the minimum frozen soil thickness controlled by the shear strength of the core bearing zone is determined by computer:

[0167] ;

[0168] In the formula, τ f Represents the shear stress in frozen soil, [τ] f The shear strength of frozen soil, where S represents the static moment of the equivalent section above or below the centroidal axis of the equivalent section about the centroidal axis of the equivalent section;

[0169] When the deflection equation equals the allowable deflection of the grouting body, the minimum frozen soil thickness controlled by the deformation of the core bearing zone is determined by computer:

[0170] ;

[0171] In the formula, δ represents deflection, and [δ] represents the allowable deflection of the grouting body.

[0172] Determine the thickness of the permafrost layer in the core bearing area:

[0173] d3=Max[h f1 h f2 h f3 ];

[0174] In the formula, d3 represents the thickness of the permafrost layer in the core bearing area, Max[h f1 h f2 h f3 ] indicates selecting h f1 h f2 h f3 The maximum value in, h f1 h represents the minimum frozen soil thickness for bending resistance control. f2 h represents the minimum thickness of frozen soil mass that controls shear strength. f3 This indicates the minimum thickness of the frozen soil body for deformation control.

[0175] In this embodiment, the thickness h of the frozen soil in the core bearing area f It is obtained by solving three independent design criteria (bending stress, shear stress, and deflection), each criterion corresponding to an equation, and the key geometric parameter y in these equations is... t I e Both S and S are functions of the permafrost thickness. Specifically:

[0176] 1) y tThis represents the distance from the centroidal axis of the equivalent cross-section to the top surface of the frozen soil mass, that is, the vertical distance from the centroidal axis of the equivalent cross-section to the outermost edge of the frozen soil layer. Its value changes with the position of the centroidal axis, while the position of the centroidal axis (y)... c It is determined by the grouting thickness h. g and the thickness of the frozen soil h f Joint decision;

[0177] 2) I e The equivalent cross-sectional moment of inertia is obtained by superimposing the moments of inertia of the grouting section and the frozen soil section after parallel axis shifting (I). e =I g +I f The moment of inertia and its axis-shifting term in the frozen part both include h. f The higher-order terms make I e Become h f Complex functions;

[0178] 3) S represents the static moment of the equivalent section above or below the centroidal axis of the equivalent section about the centroidal axis of the equivalent section, which is the static moment (area moment) of the frozen soil layer about the centroid of the composite section. It is calculated as the product of the frozen soil area and the distance from its centroid to the composite centroid, and also varies with h. f change;

[0179] Wherein, parameter y t I e S and h f The non-linear relationship between them is as follows:

[0180] ;

[0181] Because of these parameters (y t I e 、S) and h f There is a nonlinear relationship between the three design equations (bending stress equation σ). f =0, shear stress equation τ f =0 and the deflection equation δ=0 are both about h f The implicit equations cannot be directly expressed as explicit analytical solutions. Therefore, in practical design, it is necessary to solve each equation separately using numerical iteration methods to obtain the minimum frozen soil thickness that satisfies the bending, shear, and deflection criteria, denoted as h, respectively. f1 h f2 and h f3 That is, respectively to h f The value of h is assigned to the three governing equations (bending stress equation, shear stress equation, and deflection equation). f1 h f2 h f3 The three values ​​can be obtained, and the final design of the frozen soil layer thickness d3 in the core bearing area is to take the maximum value of the three values.

[0182] S5. Based on the freezing thickness, frost heave rate and thaw settlement rate, calculate the frost heave amount and thaw settlement amount by combining the frost heave inhibition coefficient and thaw settlement correction coefficient, and determine the freezing reinforcement thickness of the frost heave and thaw settlement improvement zone according to the frost heave amount and thaw settlement amount.

[0183] The process of calculating the amount of frost heave and frost settlement based on the freezing thickness, frost heave rate, and thaw settlement rate, combined with the frost heave inhibition coefficient and thaw settlement correction coefficient, and determining the freezing reinforcement thickness of the frost heave and thaw settlement improvement zone based on the amount of frost heave and thaw settlement includes the following steps:

[0184] S51. Calculate the amount of frost heave based on the freezing thickness and frost heave rate, combined with the frost heave inhibition coefficient, and determine the amount of thaw settlement based on the thaw settlement rate, freezing thickness, and thaw settlement correction coefficient.

[0185] Specifically, the expression for frost heave is:

[0186] A = a × η × H;

[0187] H=d 1xz +d3;

[0188] In the formula, A represents the frost heave amount, α represents the frost heave inhibition coefficient, with a value ranging from 0.4 to 0.6, η represents the frost heave rate, with a value ranging from 1% to 3%, H represents the frozen thickness, and d 1xz The revised thickness of the grouting layer in the contact seepage isolation zone;

[0189] The expression for the amount of sediment is:

[0190] B=β× ×H;

[0191] In the formula, B represents the amount of melt-settling, and β represents the melt-settling correction coefficient, with a value ranging from 0.3 to 0.5. This represents the settling rate, with a value ranging from 0.8% to 2%.

[0192] S52. Select the maximum value of frost heave and thaw settlement as the freezing reinforcement thickness of the frost heave and thaw settlement improvement zone.

[0193] Specifically, the frost heave and thaw settlement improvement zone was determined to be outside the freezing reinforcement area:

[0194] d4 = Max[A, B];

[0195] In the formula, d4 represents the thickness of the frozen reinforcement in the frost heave and thaw settlement improvement zone, and Max[A, B] represents the maximum value of A and B.

[0196] This invention utilizes a synergistic effect of grouting and freezing to control formation properties in zones: Zone I (contact seepage isolation zone) employs a grouting layer to reduce thermal conductivity, suppressing the thawing of frozen soil caused by ambient temperature and localized thermal operations (such as cutting), and controls the thawing thickness using a heat conduction model to eliminate seepage channels; Zone II (self-stabilizing seepage prevention zone at the free face) uses grouting to provide unconfined strength ≥4.0MPa and permeability coefficient ≤2×10⁻⁶. -6 The bearing-supporting impermeable layer has a thickness of cm / s; Zone III (core bearing zone) provides the main bearing capacity with the frozen wall, and the thickness is optimized through the stratum-structure model; Zone IV (frost heave and thaw settlement improvement zone) involves extended permeable grouting of the frozen zone, through pore filling (filling rate 15%-30%) and reduction of permeability coefficient (10). -3 -10 -5 This method (using a speed of cm / s) inhibits water migration, reducing the frost heave rate to 0.5%-1.5% and the thaw settlement rate to 0.3%-1.2%. It achieves a 27,000-fold reduction in seepage flow, solving the challenges of structural stability and seepage control in high-permeability formation connections.

[0197] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for zoned reinforcement of the strata in the underground docking section of a shield tunnel, characterized in that, Includes the following steps: S1. Based on the preset reinforcement requirements, the highly permeable strata in the shield tunnel are divided into a contact seepage isolation zone, a self-stabilizing seepage prevention zone at the free face, a core bearing zone, and a frost heave and thaw settlement improvement zone; Step S1 specifically includes: S11. The junction between the shield and the frozen soil is divided into a contact seepage isolation zone; S12. Divide the excavation outline area of ​​the shield docking cutterhead into a free face self-stabilizing seepage prevention zone. S13. Divide the artificially frozen main wall into a core bearing area; S14. Improve the soil around the frozen zone by infiltration grouting to create a frost heave and thaw settlement improvement zone. S2. Based on the temperature diffusion radius and melting zone radius, and combined with a correction coefficient, determine the grouting layer thickness of the contact seepage isolation zone, and determine the grouting layer length of the contact seepage isolation zone according to the length of the docking shield, the width of the docking shield cut, and a preset reduction coefficient; Step S2 specifically includes: S21. Solve the temperature field based on the radial steady-state heat conduction of the multi-layer material cylindrical wall to determine the temperature distribution of each layer of material and obtain the temperature at any position of each layer of material. S22. Determine the temperature diffusion radius based on the temperature at any location of each layer of material and the location of the freezing point, and solve the transient temperature field under the conduction of a single heat source in a multi-layered flat plate material. S23. Select the maximum value of the temperature diffusion radius and the melting zone radius under the transient temperature field as the initial grouting layer thickness, and combine the correction coefficient to correct the initial grouting layer thickness to obtain the corrected grouting layer thickness of the contact seepage isolation zone. S24. Determine the length of the grouting layer in the contact seepage isolation zone based on the length of the docking shield, the width of the docking shield cut, and the preset reduction coefficient. S3. Based on the target thicknesses for bending and shear control, determine the thickness of the grouting layer in the self-stabilizing seepage prevention zone of the free face, and based on the width of the shield tunnel cut and the overlap length, determine the length of the grouting layer in the self-stabilizing seepage prevention zone of the free face; Step S3 specifically includes: S31. Based on the material properties and test results of the grouting layer, determine the flexural strength and shear strength of the grouting body in the self-stabilizing seepage prevention zone of the free face; S32. Based on the self-stability under construction disturbance and vibration, combined with the dynamic load coefficient and the weight of locally melted water storage, calculate the maximum bending moment and maximum shear force of the grouting body in the self-stabilizing seepage prevention zone of the free face. S33. Based on the bending stress calculation and shear stress calculation, combined with the maximum bending moment and maximum shear force of the grouting body, determine the minimum thickness for bending resistance control and the minimum thickness for shear resistance control of the self-stabilizing seepage prevention zone on the free face. S34. Select the maximum value of the minimum thickness for bending control and the minimum thickness for shear control as the grouting layer thickness of the self-stabilizing seepage prevention zone of the free face, and determine the grouting layer length of the self-stabilizing seepage prevention zone of the free face in combination with the cut width and overlap length of the connecting shield. S4. Convert the frozen soil section into an equivalent grouting section. Based on the equivalent grouting section, calculate the target frozen soil thickness using flexural bearing capacity, shear bearing capacity, and deformation control. Determine the frozen soil layer thickness in the core bearing zone based on the target frozen soil thickness. Step S4 specifically includes: S41. Determine the maximum bending moment and maximum shear force in the core bearing area based on the external load, and convert the frozen soil section into an equivalent grouting section with constant thickness and preset width; based on the converted equivalent grouting section, calculate the position of the centroidal axis and moment of inertia of the equivalent section; S42. Based on the bending bearing capacity, shear bearing capacity and deformation control, calculate the minimum frozen soil thickness for bending control, shear control and deformation control, and select the maximum value of the minimum frozen soil thickness for bending control, shear control and deformation control as the frozen soil layer thickness of the core bearing area. Specifically, when the bending stress equation equals the bending strength of the frozen soil, the minimum frozen soil thickness controlled by the bending resistance of the core bearing area is determined; when the shear stress equation equals the shear strength of the frozen soil, the minimum frozen soil thickness controlled by the shear resistance of the core bearing area is determined; and when the deflection equation equals the allowable deflection of the grouting body, the minimum frozen soil thickness controlled by the deformation of the core bearing area is determined. S5. Based on the freezing thickness, frost heave rate and thaw settlement rate, calculate the frost heave amount and thaw settlement amount by combining the frost heave inhibition coefficient and thaw settlement correction coefficient, and determine the freezing reinforcement thickness of the frost heave and thaw settlement improvement zone according to the frost heave amount and thaw settlement amount.

2. The method for zoned reinforcement of the strata in the underground docking section of a shield tunnel according to claim 1, characterized in that, The expression for the temperature at any location in each material layer is: ； ； ； The revised expression for the grouting layer thickness in the contact seepage isolation zone is: ； d1 = Max[r, K]; ； ； The expression for the length of the grouting layer in the contact seepage isolation zone is: L1=2×ω×L C +L D ; In the formula, T r T represents the temperature at any location in the i-th layer of material. i T represents the inner surface temperature of the i-th layer of material. i+1 Let r represent the outer surface temperature of the i-th layer of material, and r represent the temperature diffusion radius. i Let r represent the inner radius of the i-th layer of material. i+1 Let R represent the outer radius of the i-th layer of material, Q represent the total heat flux of the material, and R represent the total heat flux of the material. i λ represents the radial thermal resistance of the i-th layer material. i Let d represent the thermal conductivity of the i-th layer of material, L represent the material length, and d represent the thermal conductivity of the i-th layer of material. 1xz The corrected grout layer thickness for the contact seepage isolation zone, γ represents the correction coefficient, d1 represents the initial grout layer thickness, Max[r, K] represents the maximum value between the temperature diffusion radius r and the melting zone radius K, t represents time, ρ represents material density, C represents material specific heat, ΔT represents temperature difference, J represents the latent heat of fusion of the material, L1 represents the grout layer length for the contact seepage isolation zone, ω represents the reduction coefficient, L C L represents the length of the docking shield. D This indicates the width of the cut in the shield tunnel.

3. The method for zoned reinforcement of the strata in the underground docking section of a shield tunnel according to claim 1, characterized in that, The expressions for the maximum bending moment and maximum shear force of the grouting body in the self-stabilizing seepage prevention zone of the free face are: ； ； The expression for the thickness of the grouting layer in the self-stabilizing seepage prevention zone of the free face is: d2=Max[t M ,t V ]; ； ； The expression for the length of the grouting layer in the self-stabilizing seepage prevention zone of the free face is: L2=L D +2ψ; In the formula, M max V represents the maximum bending moment of the grouting body in the self-stabilizing seepage prevention zone of the free face. max ξ represents the maximum shear force of the grouting body in the self-stabilizing seepage prevention zone of the free face, and q represents the dynamic load coefficient. s q represents the weight of the water stored during partial melting. t L represents the weight of the grouting body in the self-stabilizing seepage prevention zone of the free face. D d1 represents the width of the shield tunnel cut, d2 represents the thickness of the grouting layer in the self-stabilizing seepage prevention zone of the free face, and Max[t] represents the thickness of the grouting layer in the free face. M , t V ] indicates the selection of t M and t V The maximum value in t M This represents the minimum thickness (t) of the self-stabilizing seepage prevention zone on the free face for flexural resistance control. V [σ] represents the minimum thickness of the shear control of the self-stabilized seepage prevention zone of the free face, [τ] represents the bending strength of the grout in the self-stabilized seepage prevention zone of the free face, [τ] represents the shear strength of the grout in the self-stabilized seepage prevention zone of the free face, L2 represents the length of the grout layer in the self-stabilized seepage prevention zone of the free face, and ψ represents the overlap length.

4. The method for zoned reinforcement of the strata in the underground docking section of a shield tunnel according to claim 1, characterized in that, The expressions for the maximum bending moment and maximum shear force in the core bearing area are: ； ； The expressions for the position of the centroidal axis and the moment of inertia of the equivalent cross section are: ； ； The expressions for the equations of bending stress, shear stress, and deflection are as follows: ； ； ； The expression for the thickness of the permafrost layer in the core bearing area is: d3=Max[h f1 h f2 h f3 ]; In the formula, M m V represents the maximum bending moment in the core load-bearing area. m q represents the maximum shear force in the core bearing area. z L represents the total external soil and water load. D Indicates the width of the cut in the tunnel boring machine, y c h represents the distance from the centroidal axis of the equivalent cross section to the lower edge of the cross section. g E represents the thickness of the grouting layer in the self-stabilizing seepage prevention zone of the free face. f E represents the elastic modulus of frozen soil. g h represents the elastic modulus of the grout. f I represents the calculated thickness of the frozen soil mass. e I represents the equivalent moment of inertia of the cross section. f I represents the moment of inertia of the frozen soil section. g σ represents the moment of inertia of the grouting body cross section. f y represents the compressive stress at the top of the frozen soil mass. t [f] represents the distance from the centroidal axis of the equivalent cross section to the top surface of the frozen soil mass. f ] represents the flexural strength of frozen soil, τ f Represents the shear stress in frozen soil, [τ] f The shear strength of frozen soil, S represents the static moment of the equivalent section above or below the centroidal axis of the equivalent section about the centroidal axis of the equivalent section, δ represents the deflection, [δ] represents the allowable deflection of the grouting body, d3 represents the thickness of the frozen soil layer in the core bearing zone, Max[h f1 h f2 h f3 ] indicates selecting h f1 h f2 h f3 The maximum value in h f1 h represents the minimum frozen soil thickness for bending resistance control. f2 h represents the minimum thickness of frozen soil mass that controls shear strength. f3 This indicates the minimum thickness of the frozen soil body for deformation control.

5. The method for zoned reinforcement of the strata in the underground docking section of a shield tunnel according to claim 1, characterized in that, The process of calculating frost heave and thaw settlement based on freezing thickness, frost heave rate, and thaw settlement rate, combined with frost heave inhibition coefficient and thaw settlement correction coefficient, and determining the freezing reinforcement thickness of the frost heave and thaw settlement improvement zone based on the frost heave and thaw settlement amounts includes the following steps: S51. Calculate the amount of frost heave based on the freezing thickness and frost heave rate, combined with the frost heave inhibition coefficient, and determine the amount of thaw settlement based on the thaw settlement rate, freezing thickness, and thaw settlement correction coefficient. S52. Select the maximum value of frost heave and thaw settlement as the freezing reinforcement thickness of the frost heave and thaw settlement improvement zone.

6. The method for zoned reinforcement of the strata in the underground docking section of a shield tunnel according to claim 5, characterized in that, The expression for frost heave is: A = a × η × H; H=d 1xz +d3; The expression for the amount of sediment is: B=β× ×H; The expression for the thickness of the freeze reinforcement in the frost heave and thaw settlement improvement zone is: d4 = Max[A, B]; In the formula, A represents the frost heave amount, α represents the frost heave inhibition coefficient, η represents the frost heave rate, H represents the frozen thickness, and d 1xz The corrected thickness of the grouting layer in the contact seepage isolation zone, d3 represents the thickness of the frozen soil layer in the core bearing zone, B represents the thaw settlement, and β represents the thaw settlement correction factor. d4 represents the thaw settlement rate, d4 represents the thickness of the frozen reinforcement in the frost heave and thaw settlement improvement zone, and Max[A, B] represents the maximum value of A and B.

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