Deeply-buried soft rock tunnel supporting structure design method based on energy regulation and control

Abstract

The invention provides a deep-buried soft rock tunnel supporting structure design method based on energy regulation and control, and belongs to the technical field of tunnel engineering. Comprising the following steps: obtaining components of crustal stress in a large principal stress direction, a middle principal stress direction and a small principal stress direction; manufacturing a rock cylinder test piece and a cube test piece; carrying out a conventional uniaxial compression test on the cylindrical test piece to obtain basic strength parameters of the surrounding rock; carrying out a true triaxial loading and unloading test on the cubic test piece to obtain the ultimate dissipated energy of the surrounding rock; drawing up a tunnel anchor rod supporting structure design scheme; establishing a deep-buried soft rock tunnel calculation model considering the synergistic effect of the surrounding rock and the anchor rod, and calculating the dissipated energy density of the surrounding rock and the absorbed energy of the supporting structure; the instability energy judgment basis of the surrounding rock and the instability energy judgment basis of the anchor rod are calculated; and judging the stability of the surrounding rock and the stability of the anchor rod. The method is suitable for the tunnel in a deep high-energy geological environment, and can reflect the energy driving essence of the instability failure of the high-ground-stress deeply-buried soft rock tunnel.

Description

Technical Field

[0001] The invention belongs to the technical field of tunnel engineering, and relates to a design method for the support structure of a deep-buried soft rock tunnel based on energy regulation. Background Technique

[0002] In the construction of railway tunnel engineering, high in-situ stress deep-buried soft rock tunnels have brought great hazards to the construction and later operation safety of tunnels due to the squeezing large deformation caused by high in-situ stress. The support structure design problem of high in-situ stress deep-buried soft rock tunnels has always troubled the majority of tunnel constructors. The existing support structure design methods mainly rely on the prediction of squeezing potential, which can be divided into the engineering analogy method, the theoretical analysis method, and the machine learning method according to different prediction methods. The engineering analogy method is based on the comprehensive analysis of existing tunnel cases with similar surrounding rock conditions and service functions, establishes a large deformation grading evaluation method for high in-situ stress deep-buried soft rock tunnels, and proposes corresponding support schemes and support parameters for different deformation grades for engineering design reference. The theoretical analysis method calculates the stress and deformation in the process of interaction between the surrounding rock and the support through theoretical analysis, and then evaluates the stability of the tunnel, and optimizes the support scheme according to the evaluation results. The machine learning method collects a large amount of deformation monitoring data and formation condition parameters, proposes the key factors affecting tunnel deformation, selects a suitable machine learning model for training, optimizes the prediction accuracy of the model by adjusting parameters and algorithms, and finally uses the trained model to predict the tunnel deformation of the actual project, and evaluates the squeezing risk and designs the support structure according to the prediction results.

[0003] The existing support design methods mainly evaluate the stability of high in-situ stress deep-buried soft rock tunnels from the perspectives of stress-strain field and displacement field evolution. However, the large deformation disasters during the construction of high in-situ stress soft rock tunnels have not been completely and effectively controlled at present, and it is still an engineering problem to be solved urgently. The deep rock mass in the high in-situ stress environment stores a high strain energy and belongs to a high-energy geological environment. The excavation of deep tunnels causes a free face in the surrounding rock of the tunnel, resulting in stress redistribution in the surrounding rock and the accumulation of energy on the free face. When the energy accumulated in the surrounding rock in the near area of the tunnel circumference exceeds the energy storage limit, the dissipation and release of energy will be triggered, which will further induce the deformation, damage and failure of the surrounding rock. Therefore, the deformation and failure process of the surrounding rock of high in-situ stress deep-buried soft rock tunnels is driven by energy. The traditional stress-strain relationship cannot reflect the energy-driven essence of the deformation and failure of the surrounding rock, and there are certain limitations in quantifying the deformation grade, severity of the tunnel and the support effect of different support parameters. A reasonable support should make the surrounding rock and support structure of the tunnel meet the requirements of bearing capacity and allowable deformation at the same time. Designing the support structure from the perspective of energy can achieve the unity of strength design and stiffness design. Summary of the Invention

[0004] The invention provides a design method for the support structure of a deep-buried soft rock tunnel based on energy regulation, including the following steps: Step 1: Test the in-situ stress in the tunnel site area to obtain the components of the in-situ stress in the directions of the major principal stress, intermediate principal stress, and minor principal stress respectively; Based on the rock masses at the engineering site in the tunnel site area, make specimens in the shapes of cylinders and cubes respectively; Step 2: Conduct a conventional uniaxial compression test on the cylindrical specimens to obtain the basic strength parameters of the surrounding rock; Conduct a true triaxial loading and unloading test on the cubic specimens to obtain the ultimate dissipated energy of the surrounding rock; Step 3: Take the energy dissipation limit value of the surrounding rock as the evaluation index for the bearing capacity of the surrounding rock of the deep-buried soft rock tunnel under high in-situ stress, and formulate a design scheme for the tunnel bolt support structure. Distribute the mortar bolts uniformly along the longitudinal and circumferential directions of the tunnel to form the tunnel support structure, and then formulate the relevant parameters of the tunnel support structure; Step 4: Based on the relevant parameters of the formulated tunnel support structure, establish a calculation model for the deep-buried soft rock tunnel considering the synergistic effect of the surrounding rock and bolts, and calculate the dissipated energy density of the surrounding rock and the absorbed energy of the support structure; Step 5: Based on the dissipated energy density of the surrounding rock and the absorbed energy of the support structure, calculate the instability energy judgment basis of the surrounding rock and the instability energy judgment basis of the bolts ; Step 6: Judge the stability of the surrounding rock according to the instability energy judgment basis of the surrounding rock and judge the stability of the bolts according to the instability energy judgment basis of the bolts ; If the stability of the surrounding rock and the stability of the bolts both meet the requirements, output the design scheme for the tunnel bolt support structure. If the stability of the surrounding rock and the stability of the bolts do not meet the requirements, adjust the relevant parameters of the tunnel support structure formulated in Step 3, such as increasing the number of bolts, reducing the bolt spacing, increasing the bolt length, or selecting bolts with greater strength, and return to Step 4.

[0005] Furthermore, the basic strength parameters of the surrounding rock include: elastic modulus , Poisson's ratio , uniaxial compressive strength , dilation coefficient , peak geological strength index , rock mass quality characteristic parameter and disturbance coefficient ; The specific process of obtaining the ultimate dissipated energy of the surrounding rock is as follows: S2.1: According to the in-situ stress test results, set the required initial values of the stresses on the six faces of the specimen respectively to simulate the stress state of the surrounding rock before tunnel excavation; among them, set the initial values of the upper and lower axial stress acting faces of the specimen to the major principal stress Set the initial value of the lateral stress on two mutually parallel sides of the test piece as the intermediate principal stress Set the initial value of the lateral stress on the other two mutually parallel sides of the test piece as the minor principal stress ; Keep the intermediate principal stress unchanged, and continuously increase the axial major principal stress at a constant loading rate by means of displacement loading Continuously unload the minor principal stress at a constant unloading rate by means of stress unloading When the minor principal stress is unloaded to zero, the test ends, and the stress-strain curves of the test piece in the directions of the major principal stress, intermediate principal stress, and minor principal stress at different time periods during the true triaxial loading and unloading process are obtained; S2.2. Based on the stress-strain and each energy component of the test piece in the directions of the major principal stress , intermediate principal stress , and minor principal stress during the elastic deformation stage of the true triaxial loading and unloading process, obtain the elastic strain energy and plastic dissipation energy of the test piece; S2.3. Based on the elastic strain energy and plastic dissipation energy of the test piece, calculate the energy dissipation rate of the test piece; S2.4. Take the plastic dissipation energy corresponding to the maximum value of the energy dissipation rate of the test piece as the energy consumption limit value of the surrounding rock , and take the energy consumption limit value of the surrounding rock as the evaluation index of the bearing capacity of the surrounding rock of the deep buried soft rock tunnel with high geostress.

[0006] Furthermore, the relevant parameters of the preliminarily determined tunnel support structure include: the layout spacing of adjacent bolts along the tunnel axis is , the included angle between adjacent bolts along the circumferential direction of the tunnel is , the length of the bolt is , the diameter of the anchorage area is , the elastic modulus of the bolt , the hardening modulus of the bolt , the yield strength of the bolt , the ultimate tensile strength of the bolt , the yield strain of the bolt , and the failure strain of the bolt .

[0007] Furthermore, the specific process of calculating the dissipated energy density of the surrounding rock and the absorbed energy of the support structure is as follows: S4.1. Establish a calculation model for deep tunnels considering the collaborative action of the surrounding rock and bolts, and input the basic parameters of the tunnel model, the strength parameters of the surrounding rock, and the material parameters of the bolts; The basic parameters of the tunnel model include: the excavation radius of the tunnel is , the virtual support reaction force acting on the tunnel wall is , the initial rock stress where the tunnel is located is , the layout spacing of adjacent bolts along the tunnel axis is , the angle between adjacent bolts along the circumferential direction of the tunnel is , the length of the bolt is and the radius of the anchorage zone is ; The strength parameters of the surrounding rock include: the elastic modulus , the Poisson's ratio , the uniaxial compressive strength , the peak geological strength index , the rock mass characteristic parameter and the disturbance coefficient ; The material parameters of the bolts include: the shear stiffness between the bolt and the grout interface , the bond strength between the bolt and the grout interface or between the surrounding rock and the grout interface , the friction angle of the grout failure surface , the elastic modulus of the bolt , the hardening modulus of the bolt , the yield strength of the bolt , the ultimate tensile strength of the bolt , the yield strain of the bolt and the failure strain of the bolt ; S4.2. Based on the deep tunnel calculation model, solve the stress evolution path of the deep tunnel surrounding rock under the collaborative action of the surrounding rock and bolts after tunnel excavation, and obtain the radial deformation of the th layer of the surrounding rock at the th unloading; S4.3. Based on the radial deformation of the th layer of the surrounding rock at the th unloading, solve the stress evolution path of the deep tunnel bolts under the collaborative action of the surrounding rock and bolts after tunnel excavation; S4.4. Calculate the energy density and total energy of the surrounding rock according to the stress evolution path of the surrounding rock; S4.5. Calculate the energy density and total absorbed energy of the bolts according to the stress evolution path of the bolts.

[0008] Furthermore, the established calculation model for deep tunnels satisfies the following conditions: (I) Assume that the tunnel depth is greater than 500 m, and the in-situ stress before excavation is a hydrostatic pressure environment with uniform distribution; (II) The surrounding rock is a homogeneous and isotropic elastic material, and the stress state in the plastic stage satisfies the three-dimensional H-B strength criterion and the strain increment conforms to the non-associated flow rule; (III) The mechanical behavior of the interaction between the bolt and the surrounding rock satisfies the bond-slip model, and the relationship between the shear stress per unit length of the bolt and the relative displacement between the bolt and the surrounding rock satisfies the following formula: ; where is the shear stress per unit length of the bolt; is the relative displacement between a certain point on the bolt and the surrounding rock at this position; is the shear stiffness between the bolt and the grout interface or between the surrounding rock and the grout interface; is the bond strength between the bolt and the grout interface or between the surrounding rock and the grout interface; is the friction angle of the failure surface of the grouting body; is the effective diameter of the interface between the bolt and the grouting layer; is the confining pressure per unit length of the bolt, and for the bolt embedded in the surrounding rock, the confining pressure on the bolt is equal to the radial stress of the surrounding rock ; (IV) The relationship between the axial force and the tensile deformation of the bolt satisfies the linear hardening elastoplastic mechanical model shown in the following formula: ; where is the axial stress of the bolt, is the tensile strain of the bolt.

[0009] Furthermore, the specific process of solving the radial deformation of the -th layer of the surrounding rock during the -th unloading is as follows: S4.2.1 Assume that the stress in the anchored area of the surrounding rock satisfies the following equilibrium equation: ; where is the bolt geometric coefficient, ; is the distance from any position of the surrounding rock to the center of the circle, is the radial stress of the surrounding rock; The stress in the unanchored area of the surrounding rock satisfies the following equilibrium equation: ; The stress in the elastic zone of the surrounding rock satisfies the following quantitative relationship: ; The stress in the plastic zone of the surrounding rock satisfies the three-dimensional HB strength criterion; S4.2.2, calculate surrounding rock stress; Assume a virtual support reaction force acting on the cave wall The original rock stress of the tunnel Gradually uninstall to 0 required The number of the step and surrounding rock layer is , then the finite difference method is used to obtain the The surrounding rock mass at the first unloading The stress of the layer is ,in, is the number of unloading steps for support reaction unloading, is the number of the surrounding rock layer, ; S4.2.3. Based on the calculation results of surrounding rock stress, solve the surrounding rock stress Layer relative to Elastic strain increment of the layer ; S4.2.4. Combine the deformation coordination equation and plastic potential function to solve the total strain of the surrounding rock ; S4.2.5. Total strain based on surrounding rock , solve The surrounding rock mass at the first unloading Radial deformation of the layer .

[0010] Furthermore, the specific process of solving the stress evolution path of the anchor bolt in the deep tunnel under the synergistic effect of the surrounding rock and the anchor bolt after tunnel excavation is as follows: S4.3.1. Based on The surrounding rock mass at the first unloading Radial deformation of the layer , solve for any point in the anchor Relative displacement between the surrounding rock and the first unloading and the shear stress of the anchor bolt; S4.3.2. Based on the shear stress of the anchor rod, calculate The first unloading of the anchor Axial force of each layer ; S4.3.3 Calculation of the tensile strain of anchor bolts based on the linear strengthening elastoplastic mechanical model of anchor bolts .

[0011] Furthermore, the neutral point position of the anchor rod is determined as follows: The position of the neutral point is determined according to the self - balance equation of the bolt. The self - balance equation of the bolt is as follows: ; Among them, is the distance between the neutral point of the bolt and the anchor head, is the distance between any point on the bolt and the bolt; When specifically solving the position of the neutral point of the bolt, the specific process is as follows: (i). Assume that the position of the neutral point is ; (ii). According to the expression of and the expression of , successively calculate the relative displacements and shear stresses of each node of the bolt; substitute the trial - calculation results of the shear stresses into the self - balance equation of the bolt; (iii). Judge whether the shear stress satisfies the self - balance equation; (iv). If not, adjust the position of the neutral point to , and return to (ii); if it satisfies, directly determine the position of the neutral point of the bolt as the final position.

[0012] Furthermore, the specific process of calculating the energy density and total energy of the surrounding rock according to the stress path of the surrounding rock is as follows: S4.4.1. According to the calculation results of the stress path of the surrounding rock, obtain the elastic energy density , plastic dissipation energy density and plastic release energy density of the th layer of the surrounding rock after times of unloading; S4.4.2. Integrate the energy - density components within the plastic zone to obtain the increment of elastic strain energy , plastic dissipation energy and plastic release energy of the plastic zone of the surrounding rock during the plastic - deformation stage; The specific process of calculating the energy density and absorbed total energy of the bolt according to the stress path of the bolt is as follows: S4.5.1. According to the calculation results of the stress path of the bolt, the distribution density of the absorbed energy of the bolt along the length direction ; S4.5.2. Integrate the energy density of any point on the bolt along the length direction to solve the absorbed energy of a single bolt during the th unloading; According to the number of bolts contained in the tunnel per unit length in the longitudinal direction, obtain the total absorbed energy of the bolts per unit cross - section of the tunnel under plane - strain conditions .

[0013] Furthermore, based on the instability energy judgment criterion of surrounding rock The specific process for judging the stability of the surrounding rock is as follows: When the instability energy judgment criterion of the surrounding rock is met, it is determined that there is no risk of instability failure of the surrounding rock; when the instability energy judgment criterion of the surrounding rock is met, it is determined that there is a risk of instability of the surrounding rock, and the greater the instability energy judgment criterion of the surrounding rock is, the higher the risk of instability; Based on the instability energy judgment criterion of the bolt The specific process for judging the stability of the bolt is as follows: When the instability energy judgment criterion of the bolt is met, it is determined that the bolt is in the normal working stage; when the instability energy judgment criterion of the bolt is met, it is determined that the bolt will be pulled off; When the instability energy judgment criterion of the surrounding rock and the instability energy judgment criterion of the bolt are both less than 1, it indicates that the design requirements of the support structure for deep-buried soft rock tunnels are met; when the instability energy judgment criterion of the surrounding rock and the instability energy judgment criterion of the bolt are both greater than or equal to 1, it indicates that the design requirements of the support structure for deep-buried soft rock tunnels are not met.

[0014] Compared with the prior art, the present invention has the following beneficial effects: (1) The present invention proposes a design method for the support structure of deep-buried soft rock tunnels based on energy regulation, which is applicable to tunnels in deep high-energy geological environments and can reflect the energy-driven essence of the instability failure of deep-buried soft rock tunnels under high in-situ stress. The essence of the instability failure of the surrounding rock in deep-buried soft rock tunnels under high in-situ stress is the result of the dissipated energy exceeding the energy consumption limit of the surrounding rock, and the essence of the failure of the support structure is that the absorbed energy exceeds the energy storage limit of the support. Therefore, the new design method proposed by the present invention aims to control the dissipated energy density of the surrounding rock and the absorbed energy density of the support structure within the limit values from the perspective of energy regulation to ensure the stability of the two load-bearing bodies of the surrounding rock and the support.

[0015] (2) The design method for the support structure of deep-buried soft rock tunnels based on energy regulation proposed by the present invention can achieve the unity of strength design and stiffness design, and solves the design problem that it is difficult to quantify the support parameters for deep-buried soft rock tunnels under high in-situ stress. A reasonable support structure should, on the one hand, fully mobilize the bearing capacity of the surrounding rock and have a certain ability to release the deformation of the surrounding rock, and on the other hand, also have compressive strength to prevent the surrounding rock from loosening and failing. Therefore, for the design of the support structure of deep-buried soft rock tunnels under high in-situ stress, the unity of strength design and stiffness design should be achieved, and energy is an effective index to achieve the unity of the two and an important basis for the design of the support structure.

[0016] In addition to the purposes, features and advantages described above, the present invention has other purposes, features and advantages. The present invention will be further described in detail below with reference to the drawings. Description of the Drawings

[0017] The drawings forming a part of this application are used to provide a further understanding of the present invention. The schematic embodiments of the present invention and their descriptions are used to explain the present invention and do not constitute an improper limitation of the present invention. In the drawings: Figure 1 is a schematic flow chart of a design method for a deep-buried soft rock tunnel support structure based on energy regulation in an embodiment of the present invention; Figure 2 is a schematic diagram of a deep tunnel calculation model in an embodiment of the present invention; Figure 3(a) is a schematic diagram of the zoning in the elastic deformation stage of the surrounding rock in an embodiment of the present invention; Figure 3(b) is a schematic diagram of the zoning in the plastic deformation stage of the surrounding rock and the radius of the plastic zone is less than the radius of the anchorage zone in an embodiment of the present invention; Figure 3(c) is a schematic diagram of the zoning in the plastic deformation stage of the surrounding rock and the radius of the plastic zone is greater than the radius of the anchorage zone in an embodiment of the present invention; Figure 4 is a schematic diagram of the relative displacement and shear stress between the surrounding rock and the bolt in an embodiment of the present invention; Figure 5 is a schematic diagram of the distribution curve of the dissipated energy density of the surrounding rock in an embodiment of the present invention; Figure 6 is a schematic diagram of the distribution curve of the absorbed energy density of the bolt in an embodiment of the present invention.

[0018] Wherein: ① is the elastic zone of the surrounding rock, ② is the plastic zone of the surrounding rock, ③ is the elastic-plastic boundary, ④ is the bolt, ⑤ is the elastic zone with anchor, ⑥ is the elastic zone without anchor, ⑦ is the plastic zone with anchor, ⑧ is the plastic zone without anchor, ⑨ is the neutral point of the bolt, ⑩ is the shear stress distribution curve of the bolt, is the test result of the energy dissipation limit of the surrounding rock, is the calculation result of the maximum dissipated energy density of the surrounding rock, is the energy storage limit of the bolt, is the calculation result of the maximum absorbed energy density of the bolt. Detailed Embodiments

[0019] To make the above objects, features, and advantages of the present invention more clearly understandable, the following provides a detailed description of the specific embodiments of the present invention in conjunction with the accompanying drawings. It should be noted that the accompanying drawings of the present invention are all in simplified forms and use non-precise scales, only for conveniently and clearly assisting in the description of the embodiments of the present invention; the several mentioned in the present invention are not limited to the specific quantities in the accompanying drawing examples; the orientation or positional relationships indicated by 'front', 'middle', 'back', 'left', 'right', 'up', 'down', 'top', 'bottom','middle', etc. in the present invention are all based on the orientation or positional relationships shown in the accompanying drawings of the present invention, and do not indicate or imply that the devices or components referred to must have a specific orientation, nor can it be construed as a limitation to the present invention.

[0020] See Figure 1 As shown, a design method for a support structure of a deeply buried soft rock tunnel based on energy regulation provided by the present invention includes the following steps: Step 1: Use the stress relief method to test the in-situ stress in the tunnel site area near the tunnel face, and respectively obtain the components of the in-situ stress in the direction of the major principal stress, the intermediate principal stress, and the minor principal stress according to the elastic mechanics theory and the measured strain data, and record the component of the in-situ stress in the direction of the major principal stress as the major principal stress , record the component of the in-situ stress in the direction of the intermediate principal stress as the intermediate principal stress and record the component of the in-situ stress in the direction of the minor principal stress as the minor principal stress ; At the same time, select a complete and relatively large rock mass from the engineering site in the tunnel site area, and prepare the rock mass into a cylindrical specimen with a size of 50mm×100mm (diameter×height) and a cubic specimen with a size of 100mm×100mm×100mm (length×width×height), and the surface flatness error of the cylindrical specimen and the cubic specimen is ±0.05mm, and the perpendicularity error is ±0.25°.

[0021] Step 2: Conduct a conventional uniaxial compression test on the cylindrical specimen to obtain the basic strength parameters of the surrounding rock; Conduct a true triaxial loading and unloading test on the cubic specimen to obtain the ultimate dissipation energy of the surrounding rock.

[0022] The basic strength parameters of the surrounding rock include: elastic modulus , Poisson's ratio , uniaxial compressive strength , dilation coefficient , peak geological strength index , rock mass quality characteristic parameter and disturbance coefficient .

[0023] The specific process of obtaining the ultimate dissipation energy of the surrounding rock is as follows: S2.1. Set the initial values to be applied to the stresses on the six surfaces of the specimen according to the in-situ stress test results, so as to simulate the stress state of the surrounding rock before tunnel excavation. Among them, set the initial values of the axial stress acting surfaces on the upper and lower sides of the specimen as the major principal stress , set the initial values of the lateral stresses on two mutually parallel side surfaces of the specimen as the intermediate principal stress , and set the initial values of the lateral stresses on the other two mutually parallel side surfaces of the specimen as the minor principal stress ; Keep the intermediate principal stress unchanged, and continuously increase the axial major principal stress at a constant loading rate by means of displacement loading, and continuously unload the minor principal stress at a constant unloading rate by means of stress unloading. When the minor principal stress is unloaded to zero, the test ends, and the stress-strain curves of the specimen in the directions of the major principal stress, intermediate principal stress, and minor principal stress at different time periods during the true triaxial loading and unloading process are obtained.

[0024] Furthermore, the different time periods during the true triaxial loading and unloading include the elastic deformation stage, plastic yield stage, post-peak strain softening stage, and residual stage.

[0025] S2.2. Based on the stress-strain in the directions of the major principal stress , intermediate principal stress , and minor principal stress of the specimen during the elastic deformation stage of the true triaxial loading and unloading process, as well as the energy components of the specimen, obtain the elastic strain energy and plastic dissipation energy of the specimen; The expression of the elastic strain energy of the specimen is as follows: ; ; Among them, is the elastic modulus of the specimen, is the Poisson's ratio of the specimen, is the elastic strain in the direction of the major principal stress, is the elastic strain in the direction of the intermediate principal stress, is the elastic strain in the direction of the minor principal stress.

[0026] The expression of the plastic dissipation energy of the rock is as follows: ; ; Among them, is the total energy of the input rock, and its value is equal to the integral of the principal stresses in all directions with respect to strain; is the total strain in the direction of the major principal stress, is the total strain in the direction of the intermediate principal stress, is the total strain in the direction of the minor principal stress; specifically, 、 and are measured by LVDT displacement sensors installed in the true triaxial test equipment.

[0027] S2.3. Based on the elastic strain energy and plastic dissipation energy of the specimen, calculate the energy dissipation rate of the specimen.

[0028] The energy dissipation rate of the specimen is expressed as follows: .

[0029] S2.4. Take the plastic dissipation energy corresponding to the energy dissipation rate of the specimen reaching its maximum value as the energy consumption limit value of the surrounding rock, and take the energy consumption limit value of the surrounding rock as the evaluation index for the bearing capacity of the surrounding rock of the high-geostress deep-buried soft rock tunnel.

[0030] Specifically, assume that the slope in the evolution curve of the energy dissipation rate of the specimen = 0, then it is the energy dissipation rate of the specimen reaching its maximum value ; that is: ; .

[0031] Step 3. Take the energy consumption limit value of the surrounding rock as the evaluation index for the bearing capacity of the surrounding rock of the high-geostress deep-buried soft rock tunnel. Initially draw up the design scheme of the tunnel bolt support structure, and distribute the mortar bolts evenly along the longitudinal and circumferential directions of the tunnel to form the tunnel support structure, and initially draw up the relevant parameters of the tunnel support structure.

[0032] The relevant parameters of the initially drawn up tunnel support structure include: the layout spacing of adjacent bolts along the tunnel axis is , the included angle between adjacent bolts along the circumferential direction of the tunnel is , the length of the bolt is , the diameter of the anchorage area is , the elastic modulus of the bolt , Hardening modulus of the bolt , Yield strength of the bolt , Ultimate tensile strength of the bolt , Yield strain of the bolt And failure strain of the bolt .

[0033] Step 4: Based on the relevant parameters of the preliminarily determined tunnel support structure, establish a calculation model for a deep-buried soft rock tunnel considering the synergy between the surrounding rock and the bolt, and calculate the dissipated energy density of the surrounding rock and the absorbed energy of the support structure.

[0034] The specific process is as follows: S4.1: Establish a calculation model for a deep tunnel considering the synergy between the surrounding rock and the bolt (see the structure of the deep tunnel calculation model in Figure 2 ), and input the basic parameters of the tunnel model, the strength parameters of the surrounding rock, and the material parameters of the bolt; Preferably, the basic parameters of the tunnel model include: the excavation radius of the tunnel is , the virtual support reaction force acting on the tunnel wall is , the in-situ stress of the tunnel is , the layout spacing of adjacent bolts along the tunnel axis is , the included angle between adjacent bolts along the circumferential direction of the tunnel is , the length of the bolt is And the radius of the anchorage zone is ;

[0035] Preferably, the strength parameters of the surrounding rock include: elastic modulus , Poisson's ratio , uniaxial compressive strength , peak geological strength index , rock mass quality characteristic parameter And disturbance coefficient . Among them: elastic modulus , Poisson's ratio And uniaxial compressive strength Are obtained through the uniaxial compression test of the rock, and the peak geological strength index , rock mass quality characteristic parameter And disturbance coefficient Are obtained according to the data obtained from the on-site survey of the surrounding rock of the tunnel face and then using The chart prediction method. Specifically, The chart prediction method is an existing technology.

[0036] Preferably, the bolt material parameters include: the shear stiffness between the bolt and the grout interface , the bond strength between the bolt and the grout interface or between the surrounding rock and the grout interface , the friction angle of the grouting body failure surface , the elastic modulus of the bolt , the hardening modulus of the bolt , the yield strength of the bolt , the ultimate tensile strength of the bolt , the yield strain of the bolt and the failure strain of the bolt . Among them: the shear stiffness , the bond strength and the bond strength are obtained through the pull-out test of the bolt, while other strength parameters are found according to the "Code for Design of Steel Structures" (GB 50017-2017).

[0037] The calculation model of the deep tunnel needs to meet the following conditions: (Ⅰ), Assume that the tunnel burial depth is large enough (burial depth greater than 500m), and the in-situ stress before excavation is a hydrostatic pressure environment with uniform distribution; (Ⅱ), Assume that the surrounding rock is a homogeneous and isotropic elastic material. And the stress state of the rock in the plastic stage satisfies the three-dimensional H-B strength criterion, and the strain increment of the rock in the plastic stage conforms to the non-associated flow rule; (Ⅲ), The mechanical behavior of the interaction between the bolt and the surrounding rock satisfies the bond-slip model, and the relationship between the shear stress per unit length of the bolt and the relative displacement between the bolt and the surrounding rock satisfies the following formula: ; Among them, is the shear stress per unit length of the bolt; is the relative displacement between a certain point on the bolt and the surrounding rock at this position; is the shear stiffness between the bolt and the grout interface or between the surrounding rock and the grout interface; is the bond strength between the bolt and the grout interface or between the surrounding rock and the grout interface; is the friction angle of the grouting body failure surface; is the effective diameter of the interface between the bolt and the grouting layer; is the confining pressure per unit length of the bolt, and for the bolt embedded in the surrounding rock, the confining pressure on the bolt is equal to the radial stress of the surrounding rock .

[0038] (Ⅳ), The relationship between the axial force and the tensile deformation of the bolt satisfies the linear hardening elastoplastic mechanical model shown in the following formula: ; Among them, is the axial stress of the bolt, is the tensile strain of the bolt

[0039] Furthermore, the expression of the three-dimensional H-B strength criterion is as follows: ; ; ; ; ; ; where, is the octahedral shear stress, is the average value of the first principal stress and the third principal stress in the octahedron, is the uniaxial compressive strength of the octahedron, , , are the strength parameters reflecting the rock characteristics in the three-dimensional H-B strength criterion, and are calculated according to the geological strength index , the rock mass characteristic parameter and the disturbance coefficient ; is the maximum principal stress of the specimen, is the intermediate principal stress of the specimen, is the minimum principal stress of the specimen, , and are obtained by conducting a true triaxial loading and unloading test on the specimen to simulate the true stress path of the surrounding rock after the excavation of a deep-buried tunnel.

[0040] Furthermore, the strain increment of the rock in the plastic zone conforms to the non-associated flow rule and satisfies the plastic potential function ; The expression of the plastic potential function is as follows: ; where, is the plastic radial strain increment, is the plastic circumferential strain increment, is the dilatancy coefficient of the rock.

[0041] Furthermore, due to the strain-softening behavior of the surrounding rock in the plastic stage, the geological strength index decreases linearly with the increase of its plastic deviatoric strain. Therefore, a strain-softening model of the surrounding rock in the plastic stage is established; The expression of the strain-softening model of the surrounding rock in the plastic stage is as follows: ; ; Among them, is the plastic deviatoric strain of the rock, which is the difference between the plastic circumferential strain and the plastic radial strain ; is the critical plastic deviatoric strain of the rock; is the peak value of the geological strength index of the rock, and it is also its initial value; is the residual value of the geological strength index of the rock.

[0042] S4.2. Solve the stress evolution path of the surrounding rock of the deep tunnel under the combined action of the surrounding rock and the bolt after tunnel excavation based on the deep tunnel calculation model (that is, solve the radial deformation of the th layer of the surrounding rock at the th unloading); The specific steps are as follows: S4.2.1. Assume that the stress in the anchored area of the surrounding rock needs to satisfy the following equilibrium equation: ; Among them, is the bolt geometric coefficient, ; is the distance from any position of the surrounding rock to the center of the circle, is the radial stress of the surrounding rock.

[0043] The stress in the unanchored area of the surrounding rock needs to satisfy the following equilibrium equation: ; The stress in the elastic zone of the surrounding rock needs to satisfy the following quantitative relationship; ; The stress in the plastic zone of the surrounding rock needs to satisfy the three-dimensional H-B strength criterion.

[0044] S4.2.2. Calculate the stress of the surrounding rock; the specific process is as follows: As shown in Figures 3(a) to 3(c), according to the size relationship between the radius of the anchored area and the radius of the plastic zone, the surrounding rock is divided into an anchored elastic zone, an unanchored elastic zone, an anchored plastic zone, and an unanchored plastic zone.

[0045] Among them, the stress in the elastic zone with anchor is calculated by combining the stress balance equation of the surrounding rock anchoring zone and the stress quantitative relationship formula of the elastic zone of the surrounding rock; the stress in the elastic zone without anchor is calculated by combining the stress balance equation of the non-anchoring zone of the surrounding rock and the stress quantitative relationship formula of the elastic zone of the surrounding rock; the stress in the plastic zone with anchor is calculated by combining the stress balance equation of the rock anchoring zone and the three-dimensional HB strength criterion expression; the stress in the plastic zone without anchor is calculated by combining the stress balance equation of the non-anchoring zone of the surrounding rock and the three-dimensional HB strength criterion expression.

[0046] Furthermore, when calculating the stresses in the elastic zone with anchor, the elastic zone without anchor, the plastic zone with anchor, and the plastic zone without anchor, the finite difference method is used to obtain the stress evolution path of the surrounding rock during the tunnel excavation unloading process. The specific calculation method is as follows: Assume that the virtual support reaction force acting on the tunnel wall is The original rock stress of the tunnel Gradually uninstall to 0 required The number of the step and surrounding rock layer is , then the finite difference method is used to obtain the The surrounding rock mass at the first unloading The stress of the layer is ,in, is the number of unloading steps for support reaction unloading, is the number of the surrounding rock layer, ;

[0047] S4.2.3. Based on the calculation results of surrounding rock stress, solve the surrounding rock stress Elastic strain of the layer ; The specific process is as follows: According to Hooke's law, the surrounding rock Layer relative to Elastic strain increment of the layer , and then get the surrounding rock Elastic strain of the layer ; Surrounding rock Layer relative to Elastic strain increment of the layer The expression is as follows: ; Surrounding rock Elastic strain of the layer The expression is as follows: ; ; in, For the Layer relative to The stress increment of the layer; S4.2.4. Simultaneously solve the deformation compatibility equation and the plastic potential function to obtain the total strain of the surrounding rock ; The total strain of the surrounding rock is expressed as follows: ; ; .

[0048] S4.2.5. From the total strain of the surrounding rock and the elastic strain increment , solve for the plastic strain increment of the -th layer of the surrounding rock relative to the -th layer, and then obtain the plastic strain of the -th layer of the surrounding rock; The plastic strain increment of the -th layer of the surrounding rock relative to the -th layer is expressed as follows: ; The plastic strain of the -th layer of the surrounding rock is expressed as follows: ; From the strain and physical equation of the surrounding rock, the radial deformation of the -th layer of the surrounding rock during the -th unloading can be solved; ; where is the radius of the -th layer of the surrounding rock.

[0049] S4.3. Based on the radial deformation of the -th layer of the surrounding rock during the -th unloading, solve for the stress evolution path of the deep tunnel bolt under the combined action of the surrounding rock and the bolt after tunnel excavation; The specific process is as follows: S4.3.1. Solve for the relative displacement between any point in the bolt and the surrounding rock during the -th unloading, as well as the shear stress of the bolt; The relative displacement between any point in the bolt and the surrounding rock during the -th unloading is expressed as follows: ; Among them, is the node number of the neutral point of the bolt; After the bolt is installed, it is the th layer of surrounding rock corresponding to the neutral point of the bolt at the th unloading deformation; After the bolt is installed, it is the deformation of the corresponding th layer of surrounding rock at the th unloading.

[0050] Furthermore, as shown in Figure 4 , the judgment method of the position of the neutral point of the bolt is as follows: The position of the neutral point is determined according to the self - balance equation of the bolt; The self - balance equation of the bolt is as follows: ; Among them, is the distance between the neutral point of the bolt and the bolt head, is the distance between any point on the bolt and the bolt.

[0051] Even further, when specifically solving the position of the neutral point of the bolt, the specific process is as follows: (i) Assume the position of the neutral point is ; (ii) According to the expressions of and , calculate the relative displacement and shear stress of each node of the bolt by trial calculation in turn; (iii) Substitute the trial - calculation result of the shear stress into the self - balance equation of the bolt, and judge whether the shear stress satisfies the self - balance equation; (iv) If not satisfied, adjust the position of the neutral point to , and return to step (ii) to recalculate the relative displacement and shear stress of each node of the bolt until the calculation converges to find a suitable position of the neutral point , and confirm this position of the neutral point as the final position.

[0052] If satisfied, directly determine the position of the neutral point of the bolt as the final position.

[0053] S4.3.2. Calculate the axial force of the th layer of the bolt at the th unloading based on the shear stress of the bolt; The expression of the axial force of the th layer of the bolt at the th unloading is as follows: ; S4.3.3 Calculate the tensile strain of the bolt based on the linear hardening elastoplastic mechanical model of the bolt ; The tensile strain of the bolt is expressed as follows: ; where is the cross-sectional area of the bolt.

[0054] S4.4 Calculate the energy density and total energy of the surrounding rock according to the stress path of the surrounding rock; The specific process is as follows: S4.4.1 Obtain the elastic energy density , plastic dissipation energy density , and plastic release energy density of the th layer of the surrounding rock after times of unloading according to the calculation results of the stress path of the surrounding rock; The expressions of the elastic energy density , plastic dissipation energy density , and plastic release energy density are as follows: ; ; ; where is the plastic dissipation strain, is the plastic release strain, is the natural constant; S4.4.2 Integrate the energy density components within the plastic zone to obtain the elastic strain energy increment , plastic dissipation energy , and plastic release energy of the plastic zone of the surrounding rock during the plastic deformation stage; The expressions of the elastic strain energy increment , plastic dissipation energy , and plastic release energy of the plastic zone of the surrounding rock during the plastic deformation stage are as follows: ; ; where is the initial elastic energy density of the surrounding rock before tunnel excavation, is the Poisson's ratio of the surrounding rock, is the elastic modulus of the surrounding rock.

[0055] S4.5. Calculate the energy density and total absorbed energy of the anchor bolt according to the stress path of the anchor bolt.

[0056] The specific process is as follows: S4.5.1. According to the calculation results of the stress path of the anchor bolt, the distribution density of the absorbed energy of the anchor bolt along the length direction ; The distribution density of the absorbed energy of the anchor bolt along the length direction is expressed as follows: ; S4.5.2. Integrate the energy density of any point of the anchor bolt along the length direction to obtain the absorbed energy of a single anchor bolt during the th unloading. Further, according to the number of anchor bolts contained in the unit length of the tunnel along the longitudinal direction, the total absorbed energy of the anchor bolts in the unit cross-section of the tunnel under plane strain conditions can be obtained ; The total absorbed energy of the anchor bolts in the unit cross-section of the tunnel under plane strain conditions is expressed as follows: ; Where: is the differential.

[0057] Step Five. Calculate the instability energy judgment basis of the surrounding rock based on the dissipated energy density of the surrounding rock and the absorbed energy of the support structure and the instability energy judgment basis of the anchor bolt ; Judge the stability of the surrounding rock according to the instability energy judgment basis of the surrounding rock and judge the stability of the anchor bolt according to the instability energy judgment basis of the anchor bolt. If the stability of the surrounding rock and the stability of the anchor bolt both meet the requirements, output the design scheme of the tunnel anchor bolt support structure. If the stability of the surrounding rock and the stability of the anchor bolt do not meet the requirements, adjust the relevant parameters of the tunnel support structure proposed in Step Three and return to Step Four.

[0058] Furthermore, the expression of the instability energy judgment basis of the surrounding rock is: ; Where, is the maximum plastic strain energy density of the surrounding rock, is the energy dissipation limit value of the surrounding rock.

[0059] When the instability energy judgment basis of the surrounding rock, it is determined that there is no risk of instability failure of the surrounding rock; when the instability energy judgment basis of the surrounding rock, it is determined that there is a risk of instability of the surrounding rock, and the instability energy judgment basis of the surrounding rock The greater it is, the higher the risk of instability.

[0060] Furthermore, the basis for judging the instability energy of the bolt has the following expression: ; ; Where: is the maximum absorption energy density of the bolt, is the energy storage limit value of the bolt, is the yield strength of the bolt, is the ultimate tensile strength of the bolt, is the yield strain of the bolt, is the failure strain of the bolt.

[0061] When the basis for judging the instability energy of the bolt is satisfied, it is determined that the bolt is in the normal working stage (i.e., the bolt is in a state where it will not be pulled apart); when the basis for judging the instability energy of the bolt is satisfied, it is determined that the bolt will be pulled apart. Example:

[0062] Taking the major principal stress as 10.20 MPa, the intermediate principal stress as 10.10 MPa, and the minor principal stress as 9.80 MPa as an example, a specific description of a design method for a deep-buried soft rock tunnel support structure based on energy regulation involved in this application is as follows: Step 1: Select a complete and relatively large rock mass from the engineering site in the tunnel site area, and prepare the rock mass into cylindrical specimens with a size of 50 mm × 100 mm (diameter × height) and cubic specimens with a size of 100 mm × 100 mm × 100 mm (length × width × height). The surface flatness error of the cylindrical specimens and cubic specimens is ±0.05 mm, and the perpendicularity error is ±0.25°.

[0063] Step 2: According to the results of the uniaxial compression test, the strength parameters of the formation are obtained as follows: rock elastic modulus , Poisson's ratio , uniaxial compressive strength , peak geological strength index , rock mass quality characteristic parameter , disturbance coefficient ; According to the test results of the in-situ stress in the tunnel site area, a true triaxial loading and unloading test is carried out on the cubic specimens. Based on the established method for determining the energy consumption limit of the surrounding rock of the deep-buried soft rock tunnel under high in-situ stress, the energy consumption limit of the surrounding rock is obtained.

[0064] Step 3: Select grouted bolts with a length of 5.0 m, which are evenly distributed longitudinally and circumferentially along the tunnel. The layout spacing of adjacent bolts along the longitudinal direction of the tunnel is , and a total of 30 bolts are arranged circumferentially around the tunnel perimeter. A calculation model of a deep-buried soft rock tunnel considering the interaction between the surrounding rock and the bolts is established according to the preliminary design parameters of the bolts, and the dissipated energy density of the surrounding rock and the absorbed energy of the support structure are calculated.

[0065] Step 4: According to the calculation results of the energy density of the surrounding rock and the support structure, obtain the maximum dissipated energy density of the surrounding rock under the interaction between the surrounding rock and the support as shown in Figure 5 and Figure 6 , and the maximum absorbed energy density of the bolts .

[0066] According to the test results of the energy consumption limit of the surrounding rock and the calculation results of the maximum dissipated energy density of the surrounding rock, obtain the basis for judging the instability energy of the surrounding rock ; According to the strength parameters of the bolts and the calculation results of the maximum absorbed energy density of the bolts, obtain the basis for judging the instability energy of the bolts ; The basis for judging the instability energy of the surrounding rock and the basis for judging the instability energy of the bolts are both less than 1, meeting the design requirements, and the design is completed.

[0067] The above are only the preferred embodiments of the present invention and are not used to limit the present invention. For those skilled in the art, the present invention can have various modifications and changes. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principle of the present invention shall be included within the protection scope of the present invention.

Claims

1. A method for designing a deep soft rock tunnel support structure based on energy regulation, characterized in that: The following steps are involved: Step 1: Test the geostress in the tunnel site area to obtain the components of the geostress in the direction of major principal stress, medium principal stress and minor principal stress respectively; The rock mass at the tunnel site was used to make cylindrical and cubic specimens. Step 2: Conduct a conventional uniaxial compression test on the cylindrical specimen to obtain the basic strength parameters of the surrounding rock; Carry out true triaxial loading and unloading tests on cubic specimens to obtain the ultimate dissipated energy of the surrounding rock; Step 3: Based on the energy consumption limit of the surrounding rock As an evaluation index of the bearing capacity of the surrounding rock of deep-buried soft rock tunnels with high geostress, a design scheme for the tunnel anchor support structure is formulated, mortar anchors are evenly distributed along the longitudinal and circumferential directions of the tunnel to form a tunnel support structure, and then relevant parameters of the tunnel support structure are formulated; Step 4: Based on the relevant parameters of the proposed tunnel support structure, a calculation model of a deep soft rock tunnel considering the synergistic effect of surrounding rock and anchor bolts is established, and the dissipated energy density of the surrounding rock and the absorbed energy of the support structure are calculated; Step 5: Calculate the instability energy of the surrounding rock based on the dissipated energy density of the surrounding rock and the absorbed energy of the support structure And the basis for judging the instability energy of anchor bolts ; Step 6: Determine the basis based on the instability energy of the surrounding rock Determine the stability of the surrounding rock and the basis for judging the instability energy of the anchor Determine the stability of the anchor rod; if the stability of the surrounding rock and the stability of the anchor rod meet the requirements, output the tunnel anchor support structure design plan; if the stability of the surrounding rock and the stability of the anchor rod do not meet the requirements, adjust the relevant parameters of the tunnel support structure proposed in step three and return to step four.

2. The method for designing a deep soft rock tunnel support structure based on energy regulation according to claim 1 is characterized in that: The basic strength parameters of the surrounding rock include: elastic modulus , Poisson's ratio , Uniaxial compressive strength , shear expansion coefficient , Peak geological intensity index , surrounding rock quality characteristic parameters and the disturbance coefficient ; The specific process of obtaining the ultimate dissipated energy of the surrounding rock is as follows: S2.

1. According to the ground stress test results, the initial values ​​of the stresses on the six surfaces of the specimen are set to simulate the stress state of the surrounding rock before tunnel excavation; the initial values ​​of the upper and lower axial stress action surfaces of the specimen are set as the major principal stress The initial values ​​of the lateral stress on two parallel sides of the specimen are set as the intermediate principal stress The initial values ​​of the lateral stresses on the other two parallel sides of the specimen are set as the minor principal stress ; Maintaining the intermediate principal stress The displacement loading method is used to continuously increase the axial principal stress at a constant loading rate. , using stress unloading to continuously unload the minor principal stress at a constant unloading rate , when the minor principal stress When the unloading reaches zero, the test ends, and the stress-strain curves of the specimens in the directions of major principal stress, intermediate principal stress and minor principal stress at different time periods during the true triaxial loading and unloading process are obtained; S2.2, based on the elastic deformation stage of the specimens in the true triaxial loading and unloading process, the specimens were , intermediate principal stress and minor principal stress The stress and strain in the direction and the energy components of the specimen are used to obtain the elastic strain energy of the specimen. and plastic dissipated energy ; S2.

3. Elastic strain energy based on the specimen and plastic dissipated energy , calculate the energy dissipation rate of the specimen ; S2.4, based on the energy dissipation rate of the specimen reaches its maximum value The corresponding plastic dissipation energy is taken as the energy dissipation limit of the surrounding rock. , based on the energy consumption limit of the surrounding rock As an evaluation index of the bearing capacity of the surrounding rock of deep-buried soft rock tunnels with high ground stress.

3. The method for designing a deep soft rock tunnel support structure based on energy regulation according to claim 1 is characterized in that: The relevant parameters of the tunnel support structure preliminarily proposed include: the spacing between adjacent anchor bolts along the tunnel axis is , the angle between adjacent anchor bolts along the circumference of the tunnel is The length of the anchor rod is The diameter of the anchoring area is , elastic modulus of anchor , Hardening modulus of anchor , yield strength of anchor , Ultimate tensile strength of anchor , yield strain of anchor and the failure strain of the anchor .

4. The method for designing a deep soft rock tunnel support structure based on energy regulation according to claim 1 is characterized in that: The specific process of calculating the dissipated energy density of the surrounding rock and the absorbed energy of the support structure is as follows: S4.

1. Establish a deep tunnel calculation model that takes into account the synergistic effect of surrounding rock and anchor bolts, and input the basic parameters of the tunnel model, surrounding rock strength parameters, and anchor bolt material parameters; The basic parameters of the tunnel model include: the excavation radius of the tunnel is , the virtual support reaction force acting on the cave wall is , the original rock stress of the tunnel is , the spacing between adjacent anchor bolts along the tunnel axis is , the angle between adjacent anchor bolts along the circumference of the tunnel is The length of the anchor rod is and the radius of the anchoring zone is ; The surrounding rock strength parameters include: elastic modulus , Poisson's ratio , Uniaxial compressive strength , Peak geological intensity index , rock quality characteristic parameters and the disturbance coefficient ; The anchor material parameters include: shear stiffness between the anchor and slurry interface , the bond strength between the anchor and the grout interface or between the surrounding rock and the grout interface , friction angle of the grouting failure surface , elastic modulus of anchor , Hardening modulus of anchor , yield strength of anchor , Ultimate tensile strength of anchor , yield strain of anchor and the failure strain of the anchor ; S4.

2. Based on the deep tunnel calculation model, the stress evolution path of the surrounding rock of the deep tunnel under the synergistic effect of the surrounding rock and anchor after tunnel excavation is solved, and the first The surrounding rock mass at the first unloading Radial deformation of the layer ; S4.3, based on The surrounding rock mass at the first unloading Radial deformation of the layer Solve the stress evolution path of deep tunnel anchors under the synergistic effect of surrounding rock and anchors after tunnel excavation; S4.

4. Calculate the energy density and total energy of the surrounding rock based on the stress evolution path of the surrounding rock; S4.

5. Calculate the energy density and total absorbed energy of the anchor based on the stress evolution path of the anchor.

5. The method for designing a deep soft rock tunnel support structure based on energy regulation according to claim 4 is characterized in that: The established deep tunnel calculation model meets the following conditions: (I) Assuming the tunnel depth is greater than 500m, the ground stress before excavation is a uniformly distributed hydrostatic pressure environment; (II) The surrounding rock is a homogeneous and isotropic elastic material and the stress state in the plastic stage satisfies the three-dimensional HB strength criterion and the strain increment conforms to the non-associated flow law; (III) The mechanical behavior of the interaction between the anchor and the surrounding rock satisfies the bond-slip model. The relationship between the shear stress per unit length of the anchor and the relative displacement between the anchor and the surrounding rock satisfies the following formula: ； in, is the shear stress per unit length of the anchor; is the relative displacement between a certain point on the anchor and the surrounding rock at that position; is the shear stiffness between the anchor and grout interface or between the surrounding rock and grout interface; It is the bond strength between the anchor and grout interface or between the surrounding rock and grout interface; is the friction angle of the failure surface of the grouting body; is the effective diameter of the interface between the anchor and the grouting layer; is the confining pressure per unit length of the anchor rod. For an anchor rod embedded in the surrounding rock, the confining pressure on the anchor rod is equal to the radial stress of the surrounding rock. ; (IV) The relationship between the axial force and tensile deformation of the anchor bolt satisfies the linear strengthening elastic-plastic mechanical model shown in the following formula: ； in, is the axial stress of the anchor rod, is the tensile strain of the anchor rod.

6. The method for designing a deep soft rock tunnel support structure based on energy regulation according to claim 5 is characterized in that: Solve The surrounding rock mass at the first unloading Radial deformation of the layer The specific process is as follows: S4.2.

1. Assume that the stress in the surrounding rock anchoring area satisfies the following equilibrium equation: ； in, is the geometric coefficient of the anchor rod, ; is the distance from any position of the surrounding rock to the center of the circle, is the radial stress of the surrounding rock; The stress in the non-anchored area of ​​the surrounding rock satisfies the following equilibrium equation: ； The stress in the elastic zone of the surrounding rock satisfies the following quantitative relationship: ； The stress in the plastic zone of the surrounding rock satisfies the three-dimensional HB strength criterion; S4.2.2, calculate surrounding rock stress; Assume a virtual support reaction force acting on the cave wall The original rock stress of the tunnel Gradually uninstall to 0 required The number of the step and surrounding rock layer is , then the finite difference method is used to obtain the The surrounding rock mass at the first unloading The stress of the layer is ,in, is the number of unloading steps for support reaction unloading, is the number of the surrounding rock layer, ; S4.2.

3. Based on the calculation results of surrounding rock stress, solve the surrounding rock stress Layer relative to Elastic strain increment of the layer ; S4.2.

4. Combine the deformation coordination equation and plastic potential function to solve the total strain of the surrounding rock ; S4.2.

5. Total strain based on surrounding rock , solve The surrounding rock mass at the first unloading Radial deformation of the layer .

7. The method for designing a deep soft rock tunnel support structure based on energy regulation according to claim 6 is characterized in that: The specific process of solving the stress evolution path of deep tunnel anchors under the synergistic effect of surrounding rock and anchors after tunnel excavation is as follows: S4.3.

1. Based on The surrounding rock mass at the first unloading Radial deformation of the layer , solve for any point in the anchor Relative displacement between the surrounding rock and the first unloading and the shear stress of the anchor; S4.3.

2. Based on the shear stress of the anchor rod, calculate The first unloading of the anchor Axial force of each layer ; S4.3.3 Calculation of the tensile strain of anchor bolts based on the linear strengthening elastoplastic mechanical model of anchor bolts .

8. The method for designing a deep soft rock tunnel support structure based on energy regulation according to claim 7 is characterized in that: The method for determining the neutral point position of the anchor rod is as follows: The position of the neutral point is determined based on the self-balancing equation of the anchor bolt; The self-balancing equation of the anchor is as follows: ； in, is the distance between the neutral point of the anchor and the anchor head, is the distance between any point of the anchor and the anchor; When solving the neutral point position of the anchor rod, the specific process is as follows: (i) Assume the position of the neutral point to be ; (ii) Based on The expression and The relative displacement and shear stress of each node of the anchor bolt are calculated in turn by using the expression of; the calculated results of shear stress are substituted into the self-balance equation of the anchor bolt; (iii) Determine whether the shear stress satisfies the self-equilibrium equation; (iv) If not satisfied, adjust the neutral point to , and return to (ii); if satisfied, directly determine the neutral point position of the anchor rod as the final position.

9. The method for designing a deep soft rock tunnel support structure based on energy regulation according to claim 8, characterized in that: The specific process of calculating the energy density and total energy of the surrounding rock according to the stress path of the surrounding rock is as follows: S4.4.

1. Based on the calculation results of surrounding rock stress path, the surrounding rock stress path is obtained. Layers are experiencing Elastic energy density after unloading , plastic dissipated energy density and plastic release energy density ; S4.4.

2. Integrate the energy density component within the plastic zone to obtain the elastic strain energy increment of the surrounding rock plastic zone during the plastic deformation stage. , Plastic dissipated energy and plastic release energy ; The specific process of calculating the energy density and total absorbed energy of the anchor according to the stress path of the anchor is as follows: S4.5.

1. Based on the calculation results of the anchor stress path, the distribution density of the anchor absorbed energy along the length direction ; S4.5.

2. Integrate the energy density at any point of the anchor along its length and solve The absorbed energy of a single anchor during the first unloading; According to the number of anchors contained in the tunnel unit length along the longitudinal direction, the total absorbed energy of the anchors per unit section of the tunnel under plane strain conditions is obtained. .

10. The method for designing a deep soft rock tunnel support structure based on energy regulation according to claim 9, characterized in that: According to the instability energy of surrounding rock The specific process of judging the stability of surrounding rock is as follows: When the instability energy of surrounding rock is determined based on When the surrounding rock is unstable, it is judged that there is no risk of instability and failure; when the instability energy of the surrounding rock is judged based on When the surrounding rock is at risk of instability, the instability energy of the surrounding rock is determined based on The larger it is, the higher the risk of instability. According to the instability energy of anchor bolt The specific process of judging the stability of the anchor is as follows: When the instability energy of the anchor is determined based on When the anchor bolt is in the normal working stage, the anchor bolt is judged to be in the normal working stage; when the anchor bolt instability energy is judged based on When , it is determined that the anchor rod will be broken; When the instability energy of surrounding rock is determined based on And the basis for judging the instability energy of anchor bolts When both are less than 1, it means that the design requirements of the support structure of deep soft rock tunnels are met; when the instability energy of the surrounding rock is determined based on And the basis for judging the instability energy of anchor bolts When both are greater than or equal to 1, it means that the design requirements of the support structure of deep soft rock tunnels are not met.

Images