Deep tunnel primary support design method based on active control of surrounding rock deformation

Abstract

The invention discloses a deep tunnel primary support design method based on active control over surrounding rock deformation, and solves the problem that in the prior art, a primary support design method is only combined with an anchor rod or a support. The method has the beneficial effects that the tunnel primary support is designed on the basis of surrounding rock deformation in combination with an anchor rod and a support, so that the design accuracy of the tunnel primary support structure is high. Determining initial pre-design parameters of a primary support structure, and determining equivalent support force of an anchoring bearing layer and support reaction force of a support bearing layer according to the initial pre-design parameters of the primary support structure; building a surrounding rock-support interaction mechanical calculation model according to the equivalent support force of the anchoring bearing layer and the support reaction force of the support bearing layer, and solving the deformation of the surrounding rock of the tunnel hole in the whole process to obtain a final deformation value of the surrounding rock of the tunnel hole; according to the determined surrounding rock deformation control value, whether surrounding rock deformation meets the control requirement or not is judged.

Description

Technical Field

[0001] The invention relates to the technical field of mountain tunnel engineering, and in particular to an initial support design method for a deep-buried tunnel based on active control of surrounding rock deformation. Background Art

[0002] The statements in this section merely provide background information related to the present invention and do not necessarily constitute prior art.

[0003] The support structure of tunnel engineering is an important part of the tunnel structure system, which can provide effective guarantee for the stability of the tunnel surrounding rock. At present, according to the design and construction requirements, the tunnel support structure mainly includes integral lining, anchor spraying lining, prefabricated lining and composite lining. In my country, traffic tunnels constructed by drilling and blasting method often use composite lining, which is generally composed of initial support, waterproof layer and secondary lining. Among them, the initial support is a support structure that is applied in time after tunnel excavation. It is generally composed of sprayed concrete, anchor rods, steel mesh, steel frame, etc. It plays an important role in ensuring the safety of tunnel construction period. Therefore, the reasonable design of the initial support structure parameters is particularly important. The determination of the corresponding parameters of the initial support of the tunnel has a great correlation with the surrounding rock mechanics. At present, relatively mature research results have been achieved for the surrounding rock-support interaction model and the anchoring mechanics effect, but the relevant research results have not combined the two in depth, nor have they involved the research on the relevant initial support design methods.

[0004] For example, Chinese patent application CN202011384891.7 discloses a method and system for designing the stiffness of a tunnel support structure system, which obtains the standard deformation of the surrounding rock at each stage of surrounding rock deformation and adjusts the stiffness value of the support structure. It does not fully consider the influence of the anchor rods and the support structure on the established model, but simply considers the need to adjust the support stiffness of the anchor rod layer, resulting in a low accuracy of the final design method. Summary of the invention

[0005] In view of the shortcomings of the prior art, the object of the present invention is to provide a method for designing initial support for a deep buried tunnel based on active control of surrounding rock deformation.

[0006] In order to achieve the above object, the present invention is implemented through the following technical solutions:

[0007] A method for designing initial support for deep buried tunnels based on active control of surrounding rock deformation includes the following contents:

[0008] Determine the surrounding rock deformation control value;

[0009] Determine the initial pre-design parameters of the initial support structure, and determine the equivalent support force of the anchor bearing layer and the support reaction force of the support bearing layer according to the initial pre-design parameters of the initial support structure;

[0010] A mechanical calculation model of surrounding rock-support interaction is established based on the equivalent support force of the anchor bearing layer and the support reaction force of the support bearing layer. The deformation of the rock around the tunnel is solved throughout the entire process to obtain the final deformation value of the rock around the tunnel.

[0011] According to the determined surrounding rock deformation control value, judge whether the surrounding rock deformation meets the control requirements: if the final deformation value of the rock around the tunnel is less than the surrounding rock deformation control value, the design requirements are met; if the final deformation value of the rock around the tunnel is greater than the surrounding rock deformation control value, it is necessary to adjust the initial pre-design parameters of the initial support structure, re-obtain the final deformation value of the rock around the tunnel, and compare it with the surrounding rock deformation control value until the requirements are met. At this time, the initial pre-design parameters of the initial support structure are the final determined initial support structure design parameters.

[0012] In the above-mentioned method for designing initial support for deep buried tunnels based on active control of surrounding rock deformation, the surrounding rock deformation control value is calculated according to the following contents:

[0013] Determine the tunnel surrounding rock grade and surrounding rock mechanical parameters;

[0014] The deformation grade of the surrounding rock is determined according to the grade of the tunnel surrounding rock, and the surrounding rock deformation control value is determined in combination with the surrounding rock mechanical parameters and the tunnel geometric parameters.

[0015] In the above-mentioned method for designing initial support for deep buried tunnels based on active control of surrounding rock deformation, the process of obtaining the equivalent support force of the anchor bearing layer includes the following contents:

[0016] According to the mechanical calculation model of the anchor bearing layer, the vertical load on the tunnel cross section is obtained;

[0017] According to the vertical load on the tunnel cross section, the elastoplastic analytical solution and the limit equilibrium theory, the support strength that can be provided by the outer boundary of the anchor bearing layer is obtained, that is, the equivalent support force of the anchor bearing layer.

[0018] In the above-mentioned method for designing initial support for deep buried tunnels based on active control of surrounding rock deformation, the process for obtaining the equivalent support force of the anchor bearing layer is as follows:

[0019] The number of anchors in the half cross section is obtained according to the tunnel radius and the annular spacing of anchors;

[0020] The thickness of the anchoring composite bearing body is obtained according to the anchor length, tunnel radius and the number of anchors in the half cross section;

[0021] The equivalent support force provided by the prestressed anchor is obtained according to the anchor preload, anchor axial spacing, and anchor circumferential spacing;

[0022] Based on the elastoplastic analytical solution, the tangential stress of the anchor bearing layer is obtained according to the equivalent support force provided by the prestressed anchor, the distance between the anchor bearing layer and the tunnel center, the equivalent cohesion of the anchor bearing layer, the equivalent internal friction angle and the tunnel radius.

[0023] The equivalent support force of the anchor bearing layer is obtained according to the tangential stress of the anchor bearing layer, the tunnel radius, the equivalent support force provided by the prestressed anchor rod and the thickness of the anchor composite bearing body.

[0024] In the above-mentioned method for designing initial support for deep buried tunnels based on active control of surrounding rock deformation, the process of obtaining the equivalent cohesion of the anchor bearing layer and the equivalent internal friction angle includes the following contents:

[0025] The anchor density factor is determined based on the friction coefficient between the anchor and the surrounding rock, the axial spacing of the anchor, the circumferential spacing of the anchor, the tunnel radius and the anchor diameter;

[0026] Determine the equivalent cohesion of the anchor bearing layer according to the anchor density factor and the anchor angle of the anchor;

[0027] The equivalent internal friction angle is determined based on the anchor density factor, the anchor angle and the equivalent cohesion of the anchor bearing layer.

[0028] In the above-mentioned method for designing initial support for deep buried tunnels based on active control of surrounding rock deformation, the process of obtaining the equivalent radial support force of the support bearing layer includes the following contents:

[0029] According to the mechanical calculation model of the support bearing layer and the thick-walled cylinder theory, the support stiffness of the support bearing layer is obtained;

[0030] The support reaction force of the support bearing layer is obtained according to the support stiffness and deformation value of the support bearing layer.

[0031] In the method for designing initial support for a deep buried tunnel based on active control of surrounding rock deformation as described above, the support stiffness of the support bearing layer is obtained according to the shear stiffness of the support bearing layer, the Poisson's ratio of the support bearing layer, the tunnel radius, and the tunnel radius after the support bearing layer is constructed;

[0032] The shear stiffness of the support bearing layer is obtained based on the elastic modulus and Poisson's ratio of the support bearing layer.

[0033] The initial support design method for a deep-buried tunnel based on active control of surrounding rock deformation as described above determines the cross-sectional bending stiffness of the support bearing layer according to the cross-sectional bending stiffness of the concrete part and the cross-sectional bending stiffness of the steel section, and then determines the elastic modulus of the support bearing layer;

[0034] Determine the equivalent compressive strength of the support bearing layer based on the compressive strength of the steel frame, the compressive strength of the concrete, the compressive strength of the concrete, the concrete area and the cross-sectional area of ​​the support bearing layer;

[0035] Determine the ultimate bearing capacity of the support layer based on the tunnel radius, the tunnel radius after the support bearing layer is constructed, and the equivalent compressive strength of the support bearing layer;

[0036] The age of shotcrete is determined based on the ultimate bearing capacity of the support layer and the elastic modulus of the support bearing layer.

[0037] The initial support design method for a deep buried tunnel based on active control of surrounding rock deformation as described above establishes an equivalent mechanical calculation model according to the equivalent support force of the anchor bearing layer and the support reaction force of the support bearing layer to obtain a homogeneous isotropic continuous medium surrounding rock;

[0038] Obtain the equivalent mechanical calculation model of the tunnel under the set hydrostatic stress;

[0039] Based on the uniform deformation condition around the tunnel, the equivalent support force of the anchor bearing layer at the equivalent tunnel radius is transformed into the equivalent support force at the tunnel radius through equivalent transformation, thereby establishing the surrounding rock-support interaction mechanical calculation model.

[0040] In the above-mentioned method for designing initial support for deep buried tunnels based on active control of surrounding rock deformation, the process of obtaining the final deformation value of the rock surrounding the tunnel includes the following contents:

[0041] According to the hydrostatic pressure, surrounding rock cohesion, anchor angle and equivalent support force of anchor bearing layer, the equivalent tunnel radius and displacement change value of tunnel perimeter after anchor bearing layer support are determined;

[0042] The equivalent tunnel radius after anchoring the bearing layer support is converted into the equivalent support force acting at the tunnel radius;

[0043] The displacement change value around the tunnel hole is equal to the displacement change value at the tunnel radius, and the equivalent support force at the tunnel radius is obtained, and then the displacement deformation expression of the tunnel hole around the tunnel radius is obtained;

[0044] The virtual support force generated by the spatial effect of the tunnel excavation surface and the elastic-plastic deformation of the tunnel periphery under the passive reaction force of the supporting structure are obtained.

[0045] The beneficial effects of the present invention are as follows:

[0046] 1) The design method of the present invention first determines the surrounding rock deformation control value, determines the equivalent support force of the anchor bearing layer and the support reaction force of the support bearing layer according to the initial pre-design parameters of the initial support structure, establishes a surrounding rock-support interaction mechanical calculation model based on the two, and obtains the final deformation value of the rock around the tunnel hole. By comparing the final deformation value of the rock around the tunnel hole with the surrounding rock deformation control value, it is judged whether the initial pre-design parameters of the initial support structure meet the requirements, thereby realizing the provision of a deep buried tunnel initial support design method based on active control of surrounding rock deformation.

[0047] 2) In the present invention, based on the vertical load on the tunnel cross section, the elastoplastic analytical solution and the limit equilibrium theory, the support strength that can be provided by the outer boundary of the anchor bearing layer, that is, the equivalent support force of the anchor bearing layer is obtained. In the process of obtaining the equivalent support force of the anchor bearing layer, multiple factors are fully considered based on the elastoplastic analytical solution, including the preload force of the anchor rod, the axial spacing of the anchor rod, the circumferential spacing of the anchor rod, the equivalent cohesion of the anchor bearing layer, the equivalent internal friction angle and other factors, so as to ensure the accuracy of obtaining the equivalent support force of the anchor bearing layer.

[0048] 3) In the present invention, the support stiffness of the support bearing layer is obtained based on the mechanical calculation model of the support bearing layer and the thick-walled cylinder theory; the support reaction force of the support bearing layer is obtained according to the support stiffness of the support bearing layer and the deformation value of the support bearing layer. The support reaction force of the support bearing layer is the support reaction force of the shotcrete and the arch frame. In the process of calculating the support reaction force of the support bearing layer, the shear stiffness of the support bearing layer, the Poisson's ratio of the support bearing layer, the tunnel radius and the tunnel radius after the support bearing layer is constructed are fully considered to obtain the support reaction force of the support bearing layer, so as to ensure the accuracy of the support reaction force of the support bearing layer.

[0049] 4) The present invention adopts an ideal elastic-plastic analytical solution as a whole, combines the mechanical calculation model of the anchor bearing layer, and considers the deformation of the surrounding rock, and proposes a mechanical calculation model of the surrounding rock-support interaction that considers the bearing effect of the anchor bearing layer; derives an analytical calculation expression for the entire deformation process of the deep-buried circular tunnel; finally, based on the mechanical calculation model of the surrounding rock-support interaction, with the goal of controlling the deformation value of the rock around the tunnel, an active control design method for the initial support deformation of the deep-buried tunnel is established, and the quantitative and precise design of the initial support structures such as prestressed anchors, shotcrete and arch frames is realized, forming an active control design method for the initial support deformation with the goal of controlling deformation, overcoming the defects in the design of tunnel engineering support structures, and enriching the relevant theories of refined design of tunnel engineering support structures. BRIEF DESCRIPTION OF THE DRAWINGS

[0050] The accompanying drawings in the specification, which constitute a part of the present invention, are used to provide a further understanding of the present invention. The exemplary embodiments of the present invention and their descriptions are used to explain the present invention and do not constitute improper limitations on the present invention.

[0051] Figure 1 It is a flow chart of a method for designing initial support for a deep buried tunnel based on active control of surrounding rock deformation according to one or more embodiments of the present invention.

[0052] Figure 2 The invention discloses a mechanical calculation model of an anchor bearing layer in an initial support design method for a deep-buried tunnel based on active control of surrounding rock deformation according to one or more embodiments of the invention.

[0053] Figure 3 It is a mechanical calculation model of the support bearing layer in the initial support design method of a deep buried tunnel based on active control of surrounding rock deformation according to one or more embodiments of the present invention.

[0054] Figure 4 It is a tunnel equivalent mechanical calculation model that takes into account the effects of anchor bearing layers and support bearing layers in an initial support design method for a deep-buried tunnel based on active control of surrounding rock deformation according to one or more embodiments of the present invention.

[0055] In the figure: the distances or sizes between parts are exaggerated to show the positions of various parts, and the schematic diagram is for reference only. DETAILED DESCRIPTION

[0056] It should be noted that the following detailed descriptions are illustrative and intended to provide further explanation of the present invention. Unless otherwise specified, all technical and scientific terms used in the present invention have the same meanings as those commonly understood by those skilled in the art to which the present invention belongs.

[0057] It should be noted that the terms used herein are only for describing specific embodiments and are not intended to limit the exemplary embodiments according to the present invention. As used herein, unless otherwise explicitly stated in the present invention, the singular form is also intended to include the plural form. In addition, it should be understood that when the terms "include" and / or "include" are used in this specification, it indicates the presence of features, steps, operations, devices, components and / or combinations thereof;

[0058] As introduced in the background technology, the problems in the prior art, in order to solve the above technical problems, the present invention proposes a method for designing initial support for deep buried tunnels based on active control of surrounding rock deformation.

[0059] Embodiment 1

[0060] In a typical embodiment of the present invention, reference is made to Figure 1 As shown in FIG. 1 , a method for designing initial support for deep buried tunnels based on active control of surrounding rock deformation includes the following contents:

[0061] Determine the surrounding rock deformation control value;

[0062] Determine the initial pre-design parameters of the initial support structure, and determine the equivalent support force of the anchor bearing layer and the support reaction force of the support bearing layer according to the initial pre-design parameters of the initial support structure;

[0063] A mechanical calculation model of surrounding rock-support interaction is established based on the equivalent support force of the anchor bearing layer and the support reaction force of the support bearing layer. The deformation of the rock around the tunnel is solved throughout the entire process to obtain the final deformation value of the rock around the tunnel.

[0064] According to the determined surrounding rock deformation control value, judge whether the surrounding rock deformation meets the control requirements: if the final deformation value of the rock around the tunnel is less than the surrounding rock deformation control value, the design requirements are met; if the final deformation value of the rock around the tunnel is greater than the surrounding rock deformation control value, the design requirements are not met, and the initial pre-design parameters of the initial support structure need to be adjusted, and the final deformation value of the rock around the tunnel is obtained again and compared with the surrounding rock deformation control value until the requirements are met. At this time, the initial pre-design parameters of the initial support structure are the final determined initial support structure design parameters.

[0065] Among them, it is necessary to explain that the anchor bearing layer refers to the anchor rock complex formed by the anchor rod and the surrounding rock, and the support effect is achieved through the support force provided by the anchor rock complex. The support bearing layer refers to the shotcrete and arch support layer. The support effect of the support bearing layer is considered to be the support force acting on the inner surface of the tunnel.

[0066] It is easy to understand that the surrounding rock deformation control value is calculated according to the following:

[0067] Determine the tunnel surrounding rock grade and surrounding rock mechanical parameters based on actual tunnel engineering geological survey data;

[0068] According to the grade of the tunnel surrounding rock, the deformation grade of the surrounding rock is determined, and the surrounding rock deformation control value is determined in combination with the surrounding rock mechanical parameters and tunnel geometric parameters.

[0069] The mechanical parameters of surrounding rock include the strength and deformation properties of surrounding rock. The mechanical parameters of surrounding rock include compressive strength, shear strength, etc. The deformation property refers to the deformation characteristics of surrounding rock when subjected to external stress.

[0070] Regarding the anchor bearing layer, after the tunnel is excavated and the anchor bolts are installed, a conical compaction zone is formed between two adjacent anchor bolts due to the interaction between the anchor bolts and the surrounding rock. The compaction zones of the surrounding rock under the action of the anchor bolt group are interconnected and connected to form a continuous and stable layered anchoring structure. The process of obtaining the equivalent support force of the anchor bearing layer includes the following contents:

[0071] refer to Figure 2 As shown in the figure, according to the existing mature mechanical calculation model of anchor bearing layer, the vertical load on the tunnel cross section is obtained, F nIt is the vertical load on the tunnel cross section and is distributed symmetrically about the tunnel axis;

[0072] According to the vertical load on the tunnel cross section, the elastoplastic analytical solution and the limit equilibrium theory, the support strength that can be provided by the outer boundary of the anchor bearing layer is obtained, that is, the equivalent support force of the anchor bearing layer.

[0073] In this embodiment, the process of obtaining the equivalent support force of the anchor bearing layer is as follows:

[0074] The number of anchors in the half cross section is obtained according to the tunnel radius and the annular spacing of anchors;

[0075] The thickness of the anchoring composite bearing body is obtained according to the anchor length, tunnel radius and the number of anchors in the half cross section;

[0076] The equivalent support force provided by the prestressed anchor is obtained according to the anchor preload, anchor axial spacing, and anchor circumferential spacing;

[0077] Based on the elastoplastic analytical solution, the tangential stress of the anchor bearing layer is obtained according to the equivalent support force provided by the prestressed anchor, the distance between the anchor bearing layer and the tunnel center, the equivalent cohesion of the anchor bearing layer, the equivalent internal friction angle and the tunnel radius.

[0078] The equivalent support force of the anchor bearing layer is obtained according to the tangential stress of the anchor bearing layer, the tunnel radius, the equivalent support force provided by the prestressed anchor rod and the thickness of the anchor composite bearing body;

[0079] Specifically, according to the tangential stress of the anchor bearing layer It can be seen that when the thickness of the anchor bearing layer is b, F n It can be expressed as

[0080]

[0081] According to the Mohr-Coulomb yield criterion (MC yield criterion) and combined with the limit equilibrium theory, the support strength that the outer boundary of the anchor bearing layer can provide, that is, the equivalent support force P of the anchor bearing layer can be derived. b The calculation formula is:

[0082]

[0083] Assuming that the surrounding rock of the anchor bearing layer obeys the Moore-Coulomb yield criterion, based on the classical elastic-plastic analytical solution (Fenner solution), the radial stress σ of the anchor bearing layer is obtained: m rp and the tangential stress σ m θp The expression is:

[0084]

[0085] Where: r is the distance between the anchor bearing layer and the tunnel center, R0 is the tunnel radius, P y The equivalent support force provided by the prestressed anchor; c*, are the equivalent cohesion and equivalent internal friction angle of the anchor bearing layer, c is the cohesion of the anchor bearing layer, is the internal friction angle of the anchor bearing layer;

[0086] The expression of anchor composite bearing thickness b is:

[0087]

[0088] The number of anchor rods in the half cross section is N.

[0089]

[0090] Prestressed anchors provide equivalent support force;

[0091]

[0092] Where, Q is the preload force of the anchor rod; L is the length of the anchor rod; S L is the axial spacing of anchor rods, S T is the circumferential spacing of anchor rods.

[0093] It should be noted that the process of obtaining the equivalent cohesion and equivalent internal friction angle of the anchor bearing layer includes the following contents:

[0094] The anchor density factor is determined based on the friction coefficient between the anchor and the surrounding rock, the axial spacing of the anchor, the circumferential spacing of the anchor, the tunnel radius and the anchor diameter;

[0095] Determine the equivalent cohesion of the anchor bearing layer according to the anchor density factor and the anchor angle of the anchor;

[0096] The equivalent internal friction angle is determined according to the anchor density factor, the anchor angle and the equivalent cohesion of the anchor bearing layer;

[0097] Specifically, after anchor support, the anchor itself can not only effectively improve the stability of the tunnel surrounding rock, but also due to the coupling effect between the anchor and the tunnel surrounding rock, the self-bearing capacity of the tunnel surrounding rock can be fully exerted. The surrounding rock of the anchor is regarded as a uniform and continuous composite material by homogenization treatment, and the anchor density factor β is defined as:

[0098]

[0099] Where: λ is the friction coefficient between the anchor and the surrounding rock. In the threaded steel anchor support system, λ = tanφ, Db is the anchor rod diameter.

[0100] Based on the assumption that the composite material of the anchor and surrounding rock still satisfies the MC yield criterion, the expressions of the equivalent internal friction angle φ* and equivalent cohesion c* of the anchor structure are derived:

[0101]

[0102] The equivalent elastic modulus of the anchoring structure is affected by the elastic modulus of the anchor rod and the elastic modulus of the surrounding rock. According to the area equivalence principle, the equivalent elastic modulus of the anchoring structure E is obtained. * The expression is:

[0103]

[0104] In the formula, E b is the elastic modulus of the anchor, E is the elastic modulus of the surrounding rock, c is the cohesion and φ is the internal friction angle.

[0105] In addition to anchor support, shotcrete + arch frame (steel arch frame, grid arch frame) structure is also an important part of the initial support. This structure is called the support bearing layer. The process of obtaining the equivalent radial support force of the support bearing layer includes the following contents:

[0106] refer to Figure 3 As shown, according to the mechanical calculation model of the support bearing layer and the existing thick-walled cylinder theory, the support stiffness of the support bearing layer is obtained;

[0107] The support reaction force of the support bearing layer is obtained according to the support stiffness and deformation value of the support bearing layer.

[0108] Among them, the support stiffness of the support bearing layer is obtained according to the shear stiffness of the support bearing layer, the Poisson's ratio of the support bearing layer, the tunnel radius and the tunnel radius after the support bearing layer is constructed;

[0109] The shear stiffness of the support bearing layer is obtained according to the elastic modulus of the support bearing layer and the Poisson's ratio of the support bearing layer;

[0110] Determine the cross-sectional bending stiffness of the support bearing layer according to the cross-sectional bending stiffness of the concrete part and the cross-sectional bending stiffness of the steel section, and then determine the elastic modulus of the support bearing layer;

[0111] Determine the equivalent compressive strength of the support bearing layer based on the compressive strength of the steel frame, the compressive strength of the concrete, the compressive strength of the concrete, the concrete area and the cross-sectional area of ​​the support bearing layer;

[0112] Determine the ultimate bearing capacity of the support layer based on the tunnel radius, the tunnel radius after the support bearing layer is constructed, and the equivalent compressive strength of the support bearing layer;

[0113] The age of shotcrete is determined based on the ultimate bearing capacity of the support layer and the elastic modulus of the support bearing layer.

[0114] Specifically, according to the thick-walled cylinder theory, the support stiffness K of the support bearing layer is c for:

[0115]

[0116] Therefore, the support reaction force P of the supporting bearing layer is c for:

[0117] P c =K c u0 (12)

[0118] In the formula, R 0l is the radius of the tunnel after the support bearing layer is constructed; u0 is the deformation value of the support bearing layer; G is the shear stiffness of the support bearing layer, G = E c / (2(1-v c ));v c E is the Poisson's ratio of the supporting bearing layer; c is the elastic modulus of the supporting bearing layer.

[0119] Among them, the mechanical parameters of the support layer are jointly determined by the shotcrete and the arch structure. Due to the hardening characteristics of shotcrete, its mechanical properties have a certain timeliness. Many scholars have analyzed its mechanical properties and used the shotcrete strength and elastic modulus E proposed in the prior art. c1 The relationship between the age t is as follows:

[0120]

[0121] Where: E c1,0 , σ c1,0 is the ultimate strength and elastic modulus of shotcrete; t is the age of shotcrete; α, β are time constants, and α=β can be taken.

[0122] Regarding the calculation of the stiffness of the arch structure, the calculation is carried out according to the shotcrete stiffness calculation formula (Formula (11)). It is only necessary to replace the elastic modulus. Similarly, if the equivalent elastic modulus of the shotcrete structure and the arch structure is substituted into Formula (11), it can be considered as the support stiffness of the support layer. The Poisson's ratio of the support layer can be assumed to be the Poisson's ratio of the shotcrete. Therefore, according to the principle of equivalent section bending stiffness, the equivalent elastic modulus of the support layer E can be obtained: c The calculation expression is:

[0123] E c I=E c1 I c1 +E c2 I c2(14)

[0124] In the formula, E c I: Component section bending stiffness; E: c1 I c1 Section bending stiffness of the concrete part; E c2 I c2 The cross-sectional bending stiffness of the steel section.

[0125] Similarly, the calculation expression of the ultimate bearing capacity of the support layer is:

[0126]

[0127] According to the area equivalence principle, the equivalent compressive strength calculation expression of the support layer can be deduced as follows:

[0128] σ c A=σ c1 A c1 +σ c2 A c2 (16)

[0129] In the formula, σ c is the equivalent compressive strength of the supporting layer; c1 is the compressive strength of the steel frame; c2 A is the compressive strength of concrete; c1 A is the cross-sectional area of ​​the steel frame; c2 is the concrete area; A is the cross-sectional area, A=A c1 +A c2 .

[0130] After the anchor rod is installed, the anchor rod and the surrounding rock form an anchor-rock complex (anchor bearing layer). Based on the mechanical calculation model of the anchor bearing layer and the classical elastic-plastic analytical solution (Fenner solution), the equivalent support force of the anchor bearing layer is obtained, and the equivalent mechanical calculation model (such as Figure 4 As shown in Figure 2), an equivalent mechanical calculation model is established based on the equivalent support force of the anchor bearing layer and the support reaction force of the support bearing layer to obtain the homogeneous isotropic continuous medium surrounding rock;

[0131] When the hydrostatic stress is P0, the radius of the tunnel plastic zone R p 、Displacement around the hole u b0 The calculation expression is as follows:

[0132]

[0133] In the formula, R b is the equivalent tunnel radius after anchoring the bearing layer support;

[0134] Based on the uniform deformation condition around the tunnel, the equivalent support force of the anchor bearing layer at the equivalent tunnel radius is transformed into the equivalent support force at the tunnel radius through equivalent transformation, thereby establishing a mechanical calculation model of surrounding rock-support interaction.

[0135] From the analysis of the support layer bearing mechanics calculation model, it can be seen that the equivalent support force provided by the support bearing layer is related to its own deformation, that is, there is an interaction relationship between the support bearing layer and the surrounding rock deformation. Therefore, in order to consider the support effect of the support bearing layer, it is necessary to establish a surrounding rock-support interaction mechanics calculation model. Since the equivalent radius of the tunnel in the above tunnel equivalent mechanical calculation model considering the effect of the anchor bearing layer is R b , it is impossible to directly establish a relationship with the supporting bearing layer. Therefore, based on the consistent deformation condition of the tunnel perimeter, this application converts the anchor bearing layer into an equivalent tunnel radius R b The equivalent support force P b Transformed into the equivalent support force P acting at the tunnel radius R0 ib , the specific conversion is as follows:

[0136] Based on the uniform deformation condition around the tunnel, we can get:

[0137]

[0138] Right now

[0139]

[0140] Solving the formula, we can obtain the equivalent support force P when the tunnel radius is R0. ib for:

[0141]

[0142] Therefore, the calculation expression of the deformation of the rock around the tunnel under the action of the anchor bearing layer is:

[0143]

[0144] The generation and development of tunnel surrounding rock deformation are affected by various force fields, mainly including original rock stress, virtual support force generated by excavation surface spatial effect, Passive reaction of supporting structure Pc Etc. Therefore, based on the spatial effect of the excavation surface and the analytical solution of the elastic-plastic displacement of the surrounding rock under the action of the anchor bearing layer established above, this patent establishes a new surrounding rock-support mechanics calculation model that considers the effect of the anchor bearing layer, as described below.

[0145] From formula (20), we can know that the force around the tunnel is The calculation expression of the elastic-plastic deformation of the tunnel under the action is:

[0146]

[0147] Corresponding to the elastic displacement at the outer diameter of the support bearing layer The support reaction force P c for:

[0148]

[0149] In the formula,

[0150] Corresponds to Virtual support force for;

[0151]

[0152] According to the Hoek fitting formula, we can get:

[0153]

[0154] in, It is calculated by the classical elastic-plastic displacement formula (Fenner solution) of the tunnel based on the MC criterion.

[0155] Corresponds to Virtual support force for

[0156]

[0157] Where: is the radial displacement of the surrounding rock at point A when support begins; A It is the distance from point A to the excavation surface when support begins.

[0158] Substituting equations (22) and (23) into equation (21), we can obtain the real-time analytical equation for the deformation of the whole process of surrounding rock-support interaction when the surrounding rock undergoes radial elastic-plastic displacement for support:

[0159]

[0160] in,

[0161]

[0162] It is easy to understand that, based on the mechanical calculation model of surrounding rock-support interaction, the longitudinal deformation curve of the tunnel is obtained and the support construction time is determined.

[0163] The design method provided in this application adopts an ideal elastic-plastic analytical solution as a whole, combines the mechanical calculation model of the anchor bearing layer, and considers the deformation of the surrounding rock, and proposes a mechanical calculation model of the surrounding rock-support interaction that considers the bearing effect of the anchor bearing layer; derives an analytical calculation expression for the entire deformation process of the deep-buried circular tunnel hole; finally, based on the mechanical calculation model of the surrounding rock-support interaction, with the goal of controlling the deformation value of the rock around the tunnel hole, an active control design method for the initial support deformation of the deep-buried tunnel is established, and the quantitative and precise design of the initial support structures such as prestressed anchors, shotcrete and arch frames is realized, forming an active control design method for the initial support deformation with the goal of controlling deformation, thereby overcoming the defects in the design of the support structure of tunnel engineering.

[0164] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. For those skilled in the art, the present invention may have various modifications and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A method for designing initial support for deep buried tunnels based on active control of surrounding rock deformation, characterized in that: It includes the following: Determine the surrounding rock deformation control value; Determine the initial pre-design parameters of the initial support structure, and determine the equivalent support force of the anchor bearing layer and the support reaction force of the support bearing layer according to the initial pre-design parameters of the initial support structure; A mechanical calculation model of surrounding rock-support interaction is established based on the equivalent support force of the anchor bearing layer and the support reaction force of the support bearing layer. The deformation of the rock around the tunnel is solved throughout the entire process to obtain the final deformation value of the rock around the tunnel. According to the determined surrounding rock deformation control value, judge whether the surrounding rock deformation meets the control requirements: if the final deformation value of the rock around the tunnel is less than the surrounding rock deformation control value, the design requirements are met; If the final deformation value of the rock around the tunnel is greater than the surrounding rock deformation control value, the initial pre-design parameters of the initial support structure need to be adjusted, the final deformation value of the rock around the tunnel needs to be obtained again, and compared with the surrounding rock deformation control value until the requirements are met. At this time, the initial pre-design parameters of the initial support structure are the finalized initial support structure design parameters.

2. The method for designing initial support for deep buried tunnels based on active control of surrounding rock deformation according to claim 1 is characterized in that: The surrounding rock deformation control value is calculated according to the following contents: Determine the tunnel surrounding rock grade and surrounding rock mechanical parameters; The deformation grade of the surrounding rock is determined according to the grade of the tunnel surrounding rock, and the surrounding rock deformation control value is determined in combination with the surrounding rock mechanical parameters and the tunnel geometric parameters.

3. The method for designing initial support for deep buried tunnels based on active control of surrounding rock deformation according to claim 1 is characterized in that: The process of obtaining the equivalent support force of the anchor bearing layer includes the following contents: According to the mechanical calculation model of the anchor bearing layer, the vertical load on the tunnel cross section is obtained; According to the vertical load on the tunnel cross section, the elastoplastic analytical solution and the limit equilibrium theory, the support strength that can be provided by the outer boundary of the anchor bearing layer is obtained, that is, the equivalent support force of the anchor bearing layer.

4. The method for designing initial support for deep buried tunnels based on active control of surrounding rock deformation according to claim 3 is characterized in that: The process of obtaining the equivalent support force of the anchor bearing layer is as follows: The number of anchors in the half cross section is obtained according to the tunnel radius and the annular spacing of anchors; The thickness of the anchoring composite bearing body is obtained according to the anchor length, tunnel radius and the number of anchors in the half cross section; The equivalent support force provided by the prestressed anchor is obtained according to the anchor preload, anchor axial spacing, and anchor circumferential spacing; Based on the elastoplastic analytical solution, the tangential stress of the anchor bearing layer is obtained according to the equivalent support force provided by the prestressed anchor, the distance between the anchor bearing layer and the tunnel center, the equivalent cohesion of the anchor bearing layer, the equivalent internal friction angle and the tunnel radius. The equivalent support force of the anchor bearing layer is obtained according to the tangential stress of the anchor bearing layer, the tunnel radius, the equivalent support force provided by the prestressed anchor rod and the thickness of the anchor composite bearing body.

5. The method for designing initial support for deep buried tunnels based on active control of surrounding rock deformation according to claim 4 is characterized in that: The process of obtaining the equivalent cohesion of the anchor bearing layer and the equivalent internal friction angle includes the following contents: The anchor density factor is determined based on the friction coefficient between the anchor and the surrounding rock, the axial spacing of the anchor, the circumferential spacing of the anchor, the tunnel radius and the anchor diameter; Determine the equivalent cohesion of the anchor bearing layer according to the anchor density factor and the anchor angle of the anchor; The equivalent internal friction angle is determined based on the anchor density factor, the anchor angle and the equivalent cohesion of the anchor bearing layer.

6. The method for designing initial support for deep buried tunnels based on active control of surrounding rock deformation according to claim 1, characterized in that: The process of obtaining the equivalent radial support force of the support bearing layer includes the following contents: According to the mechanical calculation model of the support bearing layer and the thick-walled cylinder theory, the support stiffness of the support bearing layer is obtained; The support reaction force of the support bearing layer is obtained according to the support stiffness and deformation value of the support bearing layer.

7. The method for designing initial support for deep buried tunnels based on active control of surrounding rock deformation according to claim 6, characterized in that: The support stiffness of the support bearing layer is obtained according to the shear stiffness of the support bearing layer, the Poisson's ratio of the support bearing layer, the tunnel radius and the tunnel radius after the support bearing layer is constructed; The shear stiffness of the support bearing layer is obtained based on the elastic modulus and Poisson's ratio of the support bearing layer.

8. The method for designing initial support for deep tunnels based on active control of surrounding rock deformation according to claim 7 is characterized in that: Determine the cross-sectional bending stiffness of the support bearing layer according to the cross-sectional bending stiffness of the concrete part and the cross-sectional bending stiffness of the steel section, and then determine the elastic modulus of the support bearing layer; Determine the equivalent compressive strength of the support bearing layer based on the compressive strength of the steel frame, the compressive strength of the concrete, the compressive strength of the concrete, the concrete area and the cross-sectional area of ​​the support bearing layer; Determine the ultimate bearing capacity of the support layer based on the tunnel radius, the tunnel radius after the support bearing layer is constructed, and the equivalent compressive strength of the support bearing layer; The age of shotcrete is determined based on the ultimate bearing capacity of the support layer and the elastic modulus of the support bearing layer.

9. The method for designing initial support for deep buried tunnels based on active control of surrounding rock deformation according to claim 1, characterized in that: An equivalent mechanical calculation model is established according to the equivalent support force of the anchor bearing layer and the support reaction force of the support bearing layer to obtain a homogeneous isotropic continuous medium surrounding rock; Obtain the equivalent mechanical calculation model of the tunnel under the set hydrostatic stress; Based on the uniform deformation condition around the tunnel, the equivalent support force of the anchor bearing layer at the equivalent tunnel radius is transformed into the equivalent support force at the tunnel radius through equivalent transformation, thereby establishing the surrounding rock-support interaction mechanical calculation model.

10. The method for designing initial support for deep buried tunnels based on active control of surrounding rock deformation according to claim 9, characterized in that: The process of obtaining the final deformation value of the rock around the tunnel includes the following contents: According to the hydrostatic pressure, surrounding rock cohesion, anchor angle and equivalent support force of anchor bearing layer, the equivalent tunnel radius and displacement change value of tunnel perimeter after anchor bearing layer support are determined; The equivalent tunnel radius after anchoring the bearing layer support is converted into the equivalent support force acting at the tunnel radius; The displacement change value around the tunnel hole is equal to the displacement change value at the tunnel radius, and the equivalent support force at the tunnel radius is obtained, and then the displacement deformation expression of the tunnel hole around the tunnel radius is obtained; The virtual support force generated by the spatial effect of the tunnel excavation surface and the elastic-plastic deformation of the tunnel periphery under the passive reaction force of the supporting structure are obtained.

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