A method and system for dividing underground engineering into deep and shallow burying based on tunnel excavation effect

Abstract

The application provides a deep and shallow buried division method and system of underground engineering based on tunnel excavation effect, and belongs to the technical field of computer-aided design. The scheme comprises the following steps: obtaining an initial ground stress field of a tunnel area; sampling the tunnel area, carrying out a conventional triaxial test, and obtaining a full stress-strain curve of surrounding rock; obtaining ground stress information of a given engineering section according to the initial ground stress field of the tunnel area, establishing a three-dimensional numerical model of the tunnel, carrying out numerical simulation by using a constitutive model considering strain softening, and obtaining a stress field after tunnel excavation; and based on the full stress-strain curve and the stress field after tunnel excavation, deep and shallow buried division is carried out. The scheme fully considers that the occurrence of tunnel disasters under strong tectonic stress is significantly affected by true three-dimensional stress, considers the tunnel excavation effect, carries out deep and shallow buried division based on the true three-dimensional stress field, provides clear suggestions for the selection of the constitutive model of surrounding rock in the design process, and provides clear guidance for support design.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of computer-aided design, in particular to a method and system for dividing deep and shallow buried underground engineering based on tunnel excavation effect. BACKGROUND

[0002] At present, the division of deep and shallow buried can be roughly divided into two categories.

[0003] The first category defines the index of specific engineering depth: that is, according to the depth of underground engineering, the critical depth is defined. Generally, when the mining depth exceeds 600 meters, it is considered as deep mining, but for countries with developed mining industry such as South Africa and Canada, the depth of mine reaches 800-1000m is called deep mining; Germany defines the depth of mine exceeding 800-1000m as deep mine, and the depth of mine exceeding 1200m as super deep mine; Japan defines the critical depth of deep mine as 600m, while the United Kingdom and Poland define it as 750m. The depth of deep resource mining in China can be defined as follows: coal mine 800-1500m, metal mine 1000-2000m.

[0004] The second category considers the surrounding rock and tunnel excavation characteristics: 1. Deep refers to the depth and the depth interval below the depth at which the engineering rock mass begins to exhibit nonlinear mechanical phenomena as the mining depth increases. The engineering located in this depth interval is called deep engineering. 2. Based on the surrounding rock relaxation theory, it is believed that the maximum pressure arch that can be formed during tunnel excavation is the limit value of deep and shallow buried tunnel. This means that if the depth of tunnel excavation is lower than this limit value, it is impossible to form a self-stable pressure arch, and the tunnel is divided into shallow buried tunnel. 3. Based on the theory of rock and soil continuum mechanics, it is believed that the minimum depth of the surrounding rock relaxation influence range cannot reach the ground surface, which is the limit value of deep and shallow buried tunnel. If the depth of tunnel excavation reaches this limit value, it is possible to cause deformation and failure that penetrates to the ground surface, so the tunnel is divided into deep buried tunnel.

[0005] However, as tunnels gradually develop towards the western region, tectonic stress has become an important factor affecting the stability of the tunnel. Under strong tectonic stress, the tunnel often appears large deformation, rock burst and other important disasters. Most of the existing deep and shallow buried division methods are difficult to apply to deep buried tunnels under the influence of strong tectonic stress, and thus cannot provide clear guidance for support design.

[0006] Therefore, it is necessary to provide an improved technical solution to the above-mentioned deficiencies of the prior art. SUMMARY

[0007] The purpose of the present application is to provide a tunnel excavation effect-based underground engineering deep-shallow burying division method and system to solve the problem that the existing deep-shallow burying division is not obviously related to engineering excavation disturbance and has no clear guidance for support design.

[0008] To achieve the above purpose, the present application provides the following technical solutions:

[0009] In a first aspect, the present application provides a tunnel excavation effect-based underground engineering deep-shallow burying division method, comprising:

[0010] Step S1, acquiring tunnel size information and initial ground stress field of a tunnel area;

[0011] Step S2, sampling the tunnel area and carrying out a conventional triaxial test with confining pressure from 0 to the maximum initial ground stress value to obtain a full stress-strain curve of the surrounding rock;

[0012] Step S3, acquiring ground stress information of a given engineering section according to the initial ground stress field of the tunnel area to establish a three-dimensional numerical model of the tunnel, carrying out numerical simulation by using a strain softening constitutive model to obtain a stress field after tunnel excavation;

[0013] Step S4, deep-shallow burying division based on the full stress-strain curve and the stress field after tunnel excavation.

[0014] In one possible implementation, in step S3:

[0015] The strain softening constitutive model is any one of the following constitutive models: a Mohr-Coulomb constitutive model considering strain softening, a Hoek-Brown constitutive model considering strain softening, and a unified strain hardening and strain softening elastoplasticity UHS constitutive model of surrounding rock.

[0016] In one possible implementation, deep-shallow burying division based on the full stress-strain curve and the stress field after tunnel excavation comprises:

[0017] According to a characteristic stress point in the full stress-strain curve, the full stress-strain curve is divided into multiple stages;

[0018] Deep-shallow burying division is performed according to the characteristics of the full stress-strain curve after stage division and the stress distribution law in the stress field after tunnel excavation.

[0019] In one possible implementation, deep-shallow burying division according to the characteristics of the full stress-strain curve after stage division and the stress distribution law in the stress field after tunnel excavation comprises:

[0020] If the stress distribution in the stress field after tunnel excavation indicates that the surrounding rock is in elastic state, the tunnel is divided into shallow tunnel.

[0021] In one possible implementation, according to the characteristics of the full stress-strain curve after stage division and the stress distribution in the stress field after tunnel excavation, the deep-shallow buried division is performed, including:

[0022] If the stress distribution in the stress field after tunnel excavation indicates that the surrounding rock is in plastic state, the axial plastic strain of the surrounding rock is analyzed:

[0023] If the axial plastic strain after excavation is 0, and the formation of the plastic zone of the tunnel is mainly caused by tangential stress concentration at this time, the tunnel is divided into medium buried tunnel;

[0024] If the axial plastic strain after excavation is not 0, and the formation of the plastic zone of the tunnel is caused by the redistribution of tangential stress and axial stress at this time, the tunnel is divided into deep buried tunnel.

[0025] In one possible implementation, in the deep buried tunnel:

[0026] If the full stress-strain curve obtained by carrying out the conventional triaxial test all appears post-peak softening, the deep buried tunnel is defined as first deep buried tunnel;

[0027] If the full stress-strain curve obtained by carrying out the conventional triaxial test does not appear post-peak softening, the deep buried tunnel is defined as second deep buried tunnel.

[0028] In a second aspect, the embodiment provides a tunnel analysis and support design method, including:

[0029] The deep-shallow buried division method based on tunnel excavation effect provided by any of the above embodiments is used to divide the tunnel into deep-shallow buried tunnel;

[0030] According to the results of deep-shallow buried division, different constitutive models are used for tunnel analysis and support design.

[0031] In one possible implementation, according to the structure of deep-shallow buried division, different constitutive models are used for tunnel design, including:

[0032] If the tunnel is a shallow tunnel, an elastic constitutive model is used in tunnel analysis and support design;

[0033] If the tunnel is a medium buried tunnel, a constitutive model considering strain softening is used in tunnel analysis and support design;

[0034] If the tunnel is a first deep buried tunnel, a strain softening constitutive model considering the influence of intermediate principal stress is used in tunnel analysis and support design;

[0035] If the tunnel is a second deep-buried tunnel, a strain hardening-strain softening constitutive model considering the influence of intermediate principal stress is used in tunnel analysis and support design.

[0036] In a third aspect, the embodiment provides a deep-shallow buried division system for underground engineering based on tunnel excavation effect, comprising:

[0037] The acquisition unit is configured to acquire tunnel size information and an initial ground stress field of the tunnel area.

[0038] The test unit is configured to sample the tunnel area, perform a conventional triaxial test with confining pressure from 0 to a maximum initial ground stress value, and obtain a full stress-strain curve of the surrounding rock.

[0039] The simulation unit is configured to acquire ground stress information of a given engineering section based on the stress field of the tunnel area, establish a three-dimensional numerical model of the tunnel, perform numerical simulation using a strain softening constitutive model, and obtain a stress field after tunnel excavation.

[0040] The first division unit is configured to perform deep-shallow buried division based on the full stress-strain curve and the stress field after tunnel excavation.

[0041] In a fourth aspect, the embodiment provides a tunnel analysis and support design system, comprising:

[0042] The second division unit is configured to perform deep-shallow buried division on the tunnel using the deep-shallow buried division method for underground engineering based on tunnel excavation effect according to any of the above embodiments.

[0043] The design unit is configured to perform tunnel analysis and support design using different constitutive models according to the deep-shallow buried division result.

[0044] In a fifth aspect, the embodiment provides a computer-readable storage medium having a computer program stored thereon, wherein the computer program is executed by a processor to implement the steps of the deep-shallow buried division method for underground engineering based on tunnel excavation effect or the tunnel analysis and support design method according to any of the above embodiments.

[0045] In a sixth aspect, the embodiment provides an electronic device, comprising a memory, a processor, and a program stored in the memory and executable on the processor, wherein the processor implements the steps of the deep-shallow buried division method for underground engineering based on tunnel excavation effect or the tunnel analysis and support design method according to any of the above embodiments when executing the program.

[0046] In a seventh aspect, the embodiments provide a computer program product comprising computer executable instructions for causing a computer to perform the steps of the method for dividing deep and shallow buried underground engineering based on tunnel excavation effect or the method for tunnel analysis and support design according to any of the above embodiments.

[0047] Advantages:

[0048] The method for dividing deep and shallow buried underground engineering based on tunnel excavation effect provided in the application fully considers that the occurrence of tunnel disasters is significantly affected by true three-dimensional stress under strong tectonic stress, and based on the true three-dimensional stress field, the deep and shallow buried division is performed in combination with the stage characteristics of the full stress-strain curve and the stress distribution law of the surrounding rock after excavation, considering the tunnel excavation effect and the influence of the principal stress after excavation on the plastic state of the surrounding rock, so that the division result can be applied to deep buried tunnels under the influence of strong tectonic stress, can provide clear suggestions for the selection of the surrounding rock constitutive model in the design process, and can provide clear guidance for support design. BRIEF DESCRIPTION OF DRAWINGS

[0049] Figure 1 A flowchart of the method for dividing deep and shallow buried underground engineering based on tunnel excavation effect according to some embodiments of the application is shown.

[0050] Figure 2 An electronic device schematic diagram is shown.

[0051] Figure 3 A stress-strain curve schematic diagram is shown.

[0052] Figure 4 A schematic diagram of the process of determining the characteristic stress by using the strain curve method is shown.

[0053] Figure 5 A logic diagram of the method for dividing deep and shallow buried underground engineering based on tunnel excavation effect according to some embodiments of the application is shown. DETAILED DESCRIPTION

[0054] The embodiments of the application are described below in conjunction with the accompanying drawings.

[0055] The embodiments of the application can be applied to Figure 2The electronic device shown can be, but is not limited to, a mobile terminal such as a mobile phone, a tablet computer, a handheld computer, a personal digital assistant (PDA), a smart television, a smart camera, a wearable device such as a smart bracelet, a smart watch, smart glasses, or other computer equipment such as a desktop computer, a laptop computer, an ultra-mobile personal computer (UMPC), a netbook, a smart screen, and the like.

[0056] As shown in Figure 2 The electronic device 200 can include one or more of the following components: a processor 201, a memory 203, a communication interface 202, a communication bus 204. The memory 203 can be connected to the processor 201 through the bus 204. The bus can transmit data between the processor 201 and the memory 203. The bus can be divided into an address bus, a data bus, a control bus, and the like.

[0057] The processor 201 can include one or more processing cores, and can utilize various interfaces and lines to connect various parts within the entire electronic device 200, execute various functions of the electronic device 200 and process data by running or executing instructions, programs, code sets or instruction sets stored in the memory 203, and calling data stored in the memory 203. For example, the processor 201 can include an application processor (AP), a modem processor, a CPU, a graphics processing unit (GPU), an image signal processor (ISP), a controller, a video codec, a digital signal processor (DSP), a field-programmable gate array (FPGA), a programmable logic array (PLA), a neural-network processing unit (NPU), and the like. Among them, the CPU mainly processes operating systems, user interfaces, and application programs; the GPU is responsible for rendering and drawing the content to be displayed; the NPU is used to implement artificial intelligence (AI) functions; and the modem is used to process wireless communication. Different processing units can be independent devices or integrated into one or more processors. For example, the above-mentioned multiple processing units are integrated into one SoC, or the AP is a separate semiconductor chip and the other processing units are integrated into one SoC, which is not limited in the present application.

[0058] The memory 203 can include a random access memory (RAM) and can also include a read-only memory (ROM), and can further include a non-transitory computer-readable storage medium. The memory 203 can be used to store instructions, programs, codes, code sets or instruction sets. The memory 203 can include a program storage area and a data storage area, wherein the program storage area can store instructions for implementing an operating system, instructions for at least one function, such as a method for dividing underground engineering into deep and shallow buried, a tunnel analysis and support design method, etc.; and the data storage area can store data created according to the use of the electronic device 200, such as input data related to tunnel excavation, etc.

[0059] In addition, those skilled in the art can understand that the structure of the electronic device 200 shown in the above-described drawings does not constitute a limitation on the electronic device 200, and the electronic device can include more or fewer components than those shown, or combine certain components, or different component arrangements. For example, the electronic device 200 also includes components such as a microphone, a speaker, a radio frequency circuit, a sensor, an audio circuit, a power supply, a Bluetooth module, and the like, which are not described here.

[0060] Embodiment one

[0061] The embodiment provides a tunnel excavation effect-based underground engineering deep and shallow burying division method, wherein the excavation effect of the tunnel is a comprehensive performance of a tunnel shape, a stress state and rock mass quality. Figure 1 As shown in the figure, the tunnel excavation effect-based underground engineering deep and shallow burying division method includes steps S1-S4, and specifically as follows:

[0062] Step S1, acquiring tunnel size information and an initial ground stress field of a tunnel area.

[0063] In the embodiment, the stress field of the tunnel site area can be obtained through field stress testing, or the stress field of the tunnel site area can be obtained through finite element numerical simulation.

[0064] As an example, according to the tunnel site area and the drilling condition requirements, a comprehensive drilling ground stress measurement is carried out mainly by the hydraulic fracturing method and supplemented by the ASR method and the DCDA method, information such as the principal stress direction and size at different depths of the tunnel drilling is understood, the tunnel ground stress distribution law is obtained, and the stress field is fitted.

[0065] Step S2, sampling the tunnel area and carrying out a conventional triaxial test with a confining pressure from 0 to a maximum initial ground stress value to obtain a full stress-strain curve of the surrounding rock.

[0066] The conventional triaxial test is used to study the influence of the confining pressure on the deformation, strength and failure characteristics of the surrounding rock in the underground engineering.

[0067] In the embodiment, the conventional triaxial mechanical test is carried out on the siltstone under different confining pressures to obtain the full stress-strain curve of the siltstone under different confining pressures.

[0068] It should be noted that the full stress-strain curve refers to a stress-strain relationship curve that can fully show the full process of deformation of the rock under the action of load.

[0069] Exemplarily, the conventional triaxial test process is as follows:

[0070] Representative surrounding rock samples, such as siltstone, were drilled from the tunnel's burial depth and processed into standard specimens (diameter d = 50 mm, height h = 100 mm) according to the recommendations of the International Society for Rock Mechanics. These rock samples were then polished to ensure parallelism and inhomogeneity errors were less than 0.02 mm and 0.05 mm, respectively. To ensure homogeneity and uniformity, specimens with similar dimensions and physical properties were carefully selected. A conventional triaxial test was conducted using an MTS815 rock mechanics testing system with displacement loading to obtain the full stress-strain curves of the surrounding rock. The confining pressure level during the test ranged from 0 MPa to the maximum stress level (maximum initial ground stress value) in the plane perpendicular to the tunnel axis. The obtained stress-strain curves of the surrounding rock are shown below. Figure 3 As shown.

[0071] Step S3: Based on the initial geostress field of the tunnel area, obtain the geostress information of the given engineering section to establish a three-dimensional numerical model of the tunnel. Use a constitutive model that considers strain softening to carry out numerical simulation and obtain the stress field after tunnel excavation.

[0072] Specifically, for a given engineering cross-section, a three-dimensional numerical model of the tunnel is established based on the initial geostress field of the tunnel area and geostress information. The size of the numerical model should be 3 to 5 times the actual engineering dimensions to eliminate the influence of boundary effects. Monitoring points are set at the most unfavorable cross-section of the numerical model to monitor the stress field of the surrounding rock after excavation.

[0073] Here, the most unfavorable cross section refers to the section where the plastic zone first appears or is the largest. Examples include cross sections with poor rock mass quality and the location of corner points in the tunnel shape.

[0074] In this embodiment, a constitutive model considering strain softening is used to conduct numerical simulation to obtain the stress field after tunnel excavation.

[0075] The constitutive model that considers strain softening can be any of the following constitutive models: the Mohr-Coulomb constitutive model that considers strain softening, the Hoek-Brown constitutive model that considers strain softening (abbreviated as HB model), or the UHS constitutive model of unified strain hardening and strain softening elastoplasticity of surrounding rock.

[0076] Understandably, other constitutive models can be used in the selection process, but the constitutive model used should at least take strain softening into account.

[0077] It is necessary to point out that the nonlinear Hoek-Brown criterion (generalized Hoek-Brown criterion) is used to describe the characteristic yield surfaces in the UHS model; in order to overcome the defect of using constant plastic shear strain to record the yield surface position, the normalized plastic shear strain is used as the plastic internal variable; the hard / softening rule is introduced to reproduce the nonlinearity of the stress-strain curve, and the non-associated flow rule is used to describe the swelling behavior of rock in the pre-peak and post-peak stages.

[0078] The UHS model uses the generalized Hoek-Brown criterion to describe the initial yield surface, the peak strength surface and the residual strength surface, and the expression is as follows:

[0079]

[0080] In the formula, f() is the yield surface equation, a, m b , s are all strength-related parameters, i = 0, 1, 2, respectively representing the initial yield surface, the peak strength surface and the residual strength surface, m b[0] , m b[1] , m b[2] are the m b values at the initial yield surface, the peak strength surface and the residual strength surface, S [0] , S [1] , S [2] are the S values at the initial yield surface, the peak strength surface and the residual strength surface, a [0] , a [1] , a [2] are the a values at the initial yield surface, the peak strength surface and the residual strength surface, σ1 is the maximum principal stress, σ3 is the minimum principal stress / confining pressure, σ c is the uniaxial compressive strength.

[0081] The UHS model uses the normalized plastic shear strain as the plastic internal variable, which is calculated according to the following definition:

[0082]

[0083]

[0084] Among them,

[0085] In the formula, γ p[1c] , γ p[2c] are the plastic shear strains at the peak strength surface and the residual strength surface under the conventional triaxial condition, are the normalized plastic shear strains in the pre-peak and post-peak stages; γ p is the plastic shear strain recorded in the constitutive relation; is the axial plastic strain, is the circumferential plastic strain.

[0086] where γ p[1c] , γ p[2c] are obtained by fitting the plastic shear strain at the peak strength plane and the residual strength plane with respect to the confining pressure σ3 under conventional triaxial conditions using linear formula, which are expressed as follows:

[0087] γ p[1c] = b [1] σ3 + c [1] (4)

[0088] γ p[2c] = b [2] σ3 + c [2] (5)

[0089] where b [1] , b [2] are the confining pressure dependent coefficients at the peak strength and the residual strength, respectively, and c [1] , c [2] are the plastic shear strain at the peak strength and the residual strength under uniaxial compression, respectively.

[0090] The softening / hardening rule of the UHS model is as follows:

[0091] It is considered that the macroscopic mechanical parameters of the surrounding rock present nonlinear evolution characteristics with the plastic shear strain in the strain hardening stage and the strain softening stage. In the UHS model, the parameters m b and s are used to control the movement of the yield surface.

[0092] In the strain hardening stage, from the initial yield surface [0] to the peak strength surface [1], m b and s evolve as follows:

[0093]

[0094] where k1 is the hardening parameter, which is a rock inherent property, and k1 should be greater than 0; is the pre-peak normalized plastic shear strain.

[0095] When k1 tends to 0, the stress-strain curve is approximately elastic-plastic. With the increase of k1, the degree of nonlinearity in the strain hardening stage of the stress-strain curve gradually decreases.

[0096] In the strain softening stage, from the peak strength surface [1] to the residual strength surface [2], m b and s evolve as follows:

[0097]

[0098] where k2 is the softening parameter, which is also a rock inherent property, and k2 should be greater than 0; is the post-peak normalized plastic shear strain.

[0099] When k2 approaches 0, the stress-strain curve is approximately brittle-plastic, and with the increase of k2, the nonlinearity of the strain softening stage in the stress-strain curve gradually decreases.

[0100] The non-associated flow rule of the UHS model is as follows:

[0101] Flow rules are often used to describe the relationship between stress and strain rate of rock materials in the process of plastic deformation. The flow rule determines the direction of plastic deformation rate of rock under a given stress state, i.e. the flow rule can be used to determine the ratio of plastic deformation in different directions in the process of incremental loading.

[0102] Flow rules include associated flow rules and non-associated flow rules. In the associated flow rule, the direction of plastic strain rate is associated with the direction of stress increment; while in the non-associated flow rule, the direction of plastic strain rate is allowed to be inconsistent with the direction of stress increment. In the process of describing the plastic strain increment of rock, the use of associated flow rules often leads to overestimation of the plastic deformation of rock. Therefore, the non-associated flow rule is used to describe the deformation characteristics of rock in the present embodiment, and the plastic potential function used in the UHS model is as follows:

[0103]

[0104] In the formula, g is the plastic potential function, c c is the equivalent cohesive force under the current stress state, ψ c is the equivalent dilatancy angle under the current stress state, which is calculated by the following formula:

[0105]

[0106] In the formula, d are the volume, maximum and minimum plastic strain increments, respectively.

[0107] Further, in order to simplify, two constant dilatancy angles are used in the UHS model, i.e. a constant pre-peak dilatancy angle ψ pre is used before the peak strength, and another constant post-peak dilatancy angle ψ post is used after the peak strength.

[0108] Therefore, the principal plastic strain can be calculated by the following formula:

[0109]

[0110] In the formula, λ s is the plastic multiplier, σ hσj, j = 1, 2, 3, are the principal stresses, with j = 1, 2, 3 representing the maximum, intermediate and minimum principal stresses, respectively.

[0111] There are 15 parameters in the UHS model, including 5 strength-related parameters, 3 strain hardening parameters, 3 strain softening parameters, 2 dilatancy parameters and 2 elastic parameters. For intact rock, a [0] = a [1] = a [2] = 0.5, s [1] = 1, s [2] = 0.

[0112] The strength-related parameters are σ c , m b[0] , s [0] , m b[1] and m b[2] , which control the nonlinear features of the three characteristic yield surfaces. σ c is the uniaxial compressive strength, which is determined from uniaxial compression tests. m b[0] and s [0] are related to the initial yield strength, which can be obtained by conducting at least two sets of triaxial compression tests to obtain the crack instability stress σ cd under triaxial compression, and then fitting the initial yield surface equation of formula (1) to the crack instability stresses under different confining pressures. m b[1] and m b[2] are related to the peak strength surface, which can be determined from at least one set of triaxial compression tests. m b[2] and m b[2] are related to the residual strength surface, which can be determined from one set of triaxial compression tests according to formula (1). If m b[1] is less than m b[2] , there will be strain softening after the peak strength. When m b[1] is greater than m [1] , there will be no strain softening stage as long as the confining pressure is large enough.

[0113] The strain hardening parameters control the nonlinear features of the pre-peak stress-strain curve. They are c [1] , b [1] and k [1] . c [1] is the plastic shear strain at the peak strength under uniaxial compression. b [1] reflects the effect of confining pressure on the plastic shear strain at the peak strength. By conducting one set of triaxial compression tests, the plastic shear strain at the peak strength under triaxial compression is obtained. Then b [1] is obtained by fitting the plastic shear strain at the peak strength surface and the confining pressure using the linear formula (formula (4)). Once b [1]It has been determined that the shape of the stress-strain curve in the pre-peak stage is determined by k. [1] Control. To calibrate k [1] At least one set of stress-strain curves for the pre-peak stage is required. Calibrate k. [1] There are two methods. The first method is to fit the stress-strain curve, and the second method is to calculate it using formula (6) or formula (7).

[0114] The strain softening parameters control the nonlinearity of the stress-strain curve in the post-peak stage. These are c [2] b [2] and k [2] c [2] It is the plastic shear strain at the residual strength under uniaxial compression conditions. (b) [2] This reflects the effect of confining pressure on the plastic shear strain at the residual strength. By conducting one or more sets of triaxial compression tests, the plastic shear strain at the residual strength under triaxial compression conditions can be obtained. Then, by fitting the plastic shear strain at the confining pressure and residual strength surfaces using the linear formula (Formula (5)), b can be obtained. [2] Once b [2] and c [2] It has been determined that the shape of the stress-strain curve in the post-peak stage is determined by k. [2] Control. Calibration k [2] There are also two methods, including fitting the post-peak stress-strain curve and calculating using formula (8) or formula (9).

[0115] The model contains two expansion parameters ψ pre and ψ post These parameters, axial and circumferential, respectively control the expansion behavior of the rock in the pre- and post-peak stages, as reflected in the axial stress-circumferential strain curves. These two parameters can be obtained by fitting the stress-strain curves. In addition, the model includes two elastic parameters: the elastic modulus E and Poisson's ratio μ. The elastic modulus E can be obtained by calculating the slope of the linear elastic stage of the axial stress-axial strain curve, while the Poisson's ratio μ is the ratio of the circumferential strain increment to the axial strain increment in the linear elastic stage.

[0116] In summary, a total of 15 parameters need to be calibrated in the UHS model. These can be obtained through at least one set of uniaxial compression tests and one set of triaxial compression tests. However, considering the nonlinear behavior of the rock, more test results will improve the accuracy of the calibration.

[0117] After parameter calibration, numerical simulation is carried out to obtain the stress field after tunnel excavation. The stress field after excavation includes the distribution of radial stress, axial stress and tangential stress of the surrounding rock with radius after excavation.

[0118] Step S4: Based on the full stress-strain curve and the stress field after tunnel excavation, perform deep and shallow burial classification.

[0119] In this embodiment, by combining the full stress-strain curve and the stress field after tunnel excavation, the influence of the intermediate principal stress on the plastic state of the surrounding rock is considered for deep and shallow buried division based on the real three-dimensional stress field, so that the deep and shallow buried division method has obvious and close connection with the disturbance effect of tunnel excavation, can be applied to deep buried tunnels under the influence of strong tectonic stress, and further provides clear guidance for tunnel analysis and design.

[0120] Specifically, based on the full stress-strain curve and the stress field after tunnel excavation, deep and shallow buried division is performed, including:

[0121] Step S41, according to the characteristic stress points in the full stress-strain curve, the full stress-strain curve is divided into multiple stages.

[0122] In this embodiment, the obtained full stress-strain curve is divided into stages, for example, it can be divided into six stages by five characteristic stress points. The multiple stages include: compaction stage, elastic stage, crack stable growth stage, crack unstable expansion stage, post-peak stage, and residual stage.

[0123] Taking the stress-strain curve of siltstone under 30 MPa confining pressure as an example, Figure 4 is a schematic diagram of the process of determining the characteristic stress by using the strain curve. As Figure 4 shown, the figure contains 4 curves: the axial stress-axial strain curve and the axial stress-radial strain curve obtained by directly testing the extensometer in the conventional triaxial test; the volume strain-axial strain curve (abbreviated as total volume strain); and the crack volume strain-axial strain curve (abbreviated as crack volume strain). According to the characteristics of the four curves in the figure, the deviatoric stress-axial strain curve of the sample can be divided into six stages by five characteristic stress points. The division of each stage and the characteristics are as follows:

[0124] Compaction stage: occurring in the initial stage of loading, the original micro-pores and micro-cracks in the sample are compacted and closed, and the corresponding deviatoric stress at the end of this stage is crack closure stress cc . The volume strain V and the crack volume strain all show compression characteristics, gradually decreasing to 0, and the deviatoric stress-axial strain curve shows a concave growth with a gentle slope. The axial strain growth rate decreases. That is, σ cc , which is the first characteristic stress point

[0125] Elastic stage: with the increase of axial stress, secondary cracks gradually form, develop and stably connect. ε V still shows compression characteristics, The deviatoric stress-axial strain curve is approximately linear up to the crack initiation stress σ ci , whose slope defines the elastic modulus. The deviatoric stress-radial strain curve is also approximately linear. ci σ is the second characteristic stress point.

[0126] Crack stable growth stage: from the crack closure stress σ cc to the crack unstable propagation stress σ cd , the crack inside the rock initiates and expands, the total volume strain increment is less than the elastic volume strain increment, , the deviatoric stress-axial strain curve still shows an approximately linear growth, and the deviatoric stress-radial strain curve deviates slightly from the linear segment. σ cd is the third characteristic stress point.

[0127] Crack unstable propagation stage: once the axial stress exceeds the crack unstable propagation stress (σ cd ), the growth of the crack will become unstable. The crack gradually condenses into a shear plane. ε V The curve appears an inflection point, the volume of the sample changes from compression to expansion. The deviatoric stress-axial strain curve shows an upward convex nonlinear feature. The axial strain increases rapidly, and the deviatoric stress-radial strain curve deviates from the linearity to a greater extent. The peak stress σ f is the fourth characteristic stress point.

[0128] Post-peak stage: macroscopic fracture surface is formed, and the sample is destroyed. The axial stress decreases sharply from the peak stress σ f to the residual stress σ s . σ s is the fifth characteristic stress point.

[0129] Residual stage: after the residual stress σ s , the sample slips along the macroscopic fracture surface, and the stress-strain curve appears a plateau segment.

[0130] In addition, Figure 4 the axial elastic strain the axial plastic strain the hoop elastic strain the hoop plastic strain The above parameters are used to calculate the plastic shear strain.

[0131] Step S42, according to the characteristics of the full stress-strain curve after stage division and the stress distribution law in the stress field after tunnel excavation, deep and shallow buried division is carried out.

[0132] In other words, in this embodiment, the distinction between shallow and deep burial is based on the characteristics of the stress-strain curve and the actual stress field after tunnel excavation. The criteria for different tunnel burial depths are as follows:

[0133] Step S421: If the stress distribution pattern in the stress field after tunnel excavation indicates that the surrounding rock is in an elastic state, then the tunnel is classified as a shallow tunnel.

[0134] Specifically, when the stress distribution of the surrounding rock after excavation shows that the radial stress gradually increases and the tangential stress gradually decreases as the radius increases, it indicates that the surrounding rock is in an elastic state. At this time, since the tunnel excavation redistribution process only loads to the elastic stage of the surrounding rock and the post-peak stage is not utilized, only the elastic stage of the stress-strain curve of the surrounding rock is utilized, it is defined as a shallow buried tunnel.

[0135] Step S422: If the stress distribution pattern in the stress field after tunnel excavation indicates that the surrounding rock has entered a plastic state, then analyze the axial plastic strain of the surrounding rock:

[0136] In this embodiment, when the stress distribution of the surrounding rock after excavation exhibits the following pattern: radial stress gradually increases with increasing radius, while tangential stress initially increases and then gradually decreases, it indicates that the surrounding rock has entered a plastic state. At this point, the axial plastic strain of the surrounding rock should be analyzed.

[0137] Step S4221: If the axial plastic strain is 0 after excavation, the formation of the tunnel plastic zone is mainly caused by tangential stress concentration, and the tunnel is classified as a buried tunnel.

[0138] Here, if the axial plastic strain is 0 after excavation, it indicates that the principal stress did not participate in the determination of the plastic zone. Therefore, the tunnel is classified as a buried tunnel.

[0139] Step S4222: If the axial plastic strain is not zero after excavation, the formation of the plastic zone in the tunnel is caused by the redistribution of tangential stress and axial stress. In this case, the tunnel is classified as a deep-buried tunnel.

[0140] Here, if the axial plastic strain is not zero after excavation, it indicates that the principal stress is involved in the determination of the plastic zone. Therefore, the tunnel is classified as a deep-buried tunnel.

[0141] Furthermore, in the deep-buried tunnel: if the full stress-strain curves obtained by conventional triaxial tests all show post-peak softening, then the deep-buried tunnel is defined as the first deep-buried tunnel (also known as: Deep-buried I).

[0142] If the full stress-strain curve obtained by conducting a conventional triaxial test shows no stress drop, then the deep-buried tunnel is defined as the second deep-buried tunnel.

[0143] It should be noted that if the stress-strain curve of the surrounding rock of the test exists without stress drop, it indicates that the stress level of the tunnel is relatively high relative to the quality of the surrounding rock, and is defined as a second deep buried tunnel (also referred to as: deep II).

[0144] The tunnel excavation effect-based underground engineering deep-shallow buried division method provided in the embodiment is further described below. Figure 5 The tunnel excavation effect-based underground engineering deep-shallow buried division method provided in the embodiment is further described below.

[0145] As shown in Figure 5 , the stress distribution of the surrounding rock presents the characteristics that the radial stress σ r gradually increases and the tangential stress σ θ gradually decreases with the increase of the radius r, at this time, only the elastic stage of the stress-strain curve of the surrounding rock is used, and there is no plastic zone on the wall, and the tunnel is defined as a shallow buried tunnel. When the buried depth gradually increases, the stress distribution of the surrounding rock after excavation presents the characteristics that the radial stress σ r gradually increases and the tangential stress σ θ first increases and then gradually decreases with the increase of the radius r, at this time, the surrounding rock enters a plastic state, and the axial plastic strain of the surrounding rock is analyzed, if the axial plastic strain after excavation is 0, the tunnel is defined as a medium buried tunnel. When the stress-strain relationship presents the characteristics of strain hardening and strain softening, and the axial plastic strain after excavation is not 0, it indicates that the plastic state is caused by the tangential stress σ θ and the axial stress σ z together, that is, the intermediate principal stress participates in the judgment of the plastic zone, and is defined as a deep buried tunnel. Further, in the deep buried tunnel, if the stress-strain curves of the surrounding rock tested all present post-peak softening, it is defined as deep I, and if the stress-strain curves of the surrounding rock tested exist without stress drop, it indicates that the stress level of the tunnel is relatively high relative to the quality of the surrounding rock, and is defined as deep II.

[0146] In summary, the tunnel excavation effect-based underground engineering deep-shallow buried division method provided in the embodiment fully considers that under strong tectonic stress, the occurrence of tunnel disasters is significantly affected by true three-dimensional stress, based on the true three-dimensional stress field, considers the influence of the excavation effect of the tunnel and the intermediate principal stress after excavation on the plastic state of the surrounding rock, and combines the stage characteristics of the full stress-strain curve and the stress distribution law of the surrounding rock after excavation to divide the deep-shallow buried, so that the division result can be applied to the deep buried tunnel under the influence of strong tectonic stress, can provide clear suggestions for the selection of the surrounding rock constitutive model in the design process, and provide clear guidance for the support design.

[0147] The method for deep and shallow bury division of underground projects based on the tunnel excavation effect provided in the embodiments of the present application combines full stress-strain curves and stress fields after tunnel excavation, comprehensively considers damage in the tunnel excavation process, nonlinear characteristics of surrounding rock, and three-dimensional stress anisotropy (i.e., whether the intermediate principal stress is prominent) at the location of the underground project, and performs deep and shallow bury division based on the stress-strain relationship of surrounding rock, stress distribution of surrounding rock after excavation, and characteristics of the plastic zone of the tunnel wall, thereby improving the rationality and applicability of the division.

[0148] Embodiment Two

[0149] The embodiment provides a tunnel analysis and support design method, which comprises the following steps:

[0150] The method for deep and shallow bury division of underground projects based on the tunnel excavation effect described in any of the above embodiments is used to perform deep and shallow bury division on the tunnel, and the specific implementation method is referred to the foregoing steps, which will not be described here.

[0151] According to the results of the deep and shallow bury division, different constitutive models are used for tunnel analysis and support design. Since the results of the deep and shallow bury division are obtained based on the tunnel excavation effect, and are closely related to the tunnel shape, stress state, and rock mass quality, the results can provide guidance for the selection of the constitutive model, and then different constitutive models are selected according to the deep and shallow bury division for tunnel analysis and support design.

[0152] Further, according to the structure of the deep and shallow bury division, different constitutive models are used for tunnel design, including:

[0153] If the tunnel is a shallow buried tunnel, an elastic constitutive model is used in the tunnel analysis and support design.

[0154] If the tunnel is a medium buried tunnel, a constitutive model considering strain softening is used in the tunnel analysis and support design.

[0155] It can be understood that for a medium buried tunnel, the selected constitutive model should at least consider the influence of strain softening, and therefore, a constitutive model considering strain hardening and strain softening is also applicable to the analysis and design of a medium buried tunnel.

[0156] If the tunnel is a first deep buried tunnel, a strain softening constitutive model considering the influence of the intermediate principal stress is used in the tunnel analysis and support design.

[0157] If the tunnel is a second deep buried tunnel, a strain hardening-strain softening constitutive model considering the influence of the intermediate principal stress is used in the tunnel analysis and support design.

[0158] Embodiment Three

[0159] The embodiment provides a system for deep and shallow bury division of underground projects based on the tunnel excavation effect, comprising:

[0160] a collection unit configured to acquire tunnel size information and an initial ground stress field of a tunnel region;

[0161] a test unit configured to sample the tunnel region, perform a conventional triaxial test with a confining pressure from 0 to a maximum initial ground stress value, and obtain a full stress-strain curve of the surrounding rock;

[0162] a simulation unit configured to acquire ground stress information of a given engineering section according to a stress field of the tunnel region, establish a three-dimensional numerical model of the tunnel, perform numerical simulation using a strain-softening constitutive model, and obtain a stress field after tunnel excavation;

[0163] a first division unit configured to divide the tunnel into deep and shallow buried tunnels based on the full stress-strain curve and the stress field after tunnel excavation.

[0164] The underground engineering deep and shallow buried division system based on tunnel excavation effect provided in the embodiments can realize the steps and processes of the underground engineering deep and shallow buried division method based on tunnel excavation effect provided in any of the embodiments, and achieve the same technical effects, which will not be repeated here.

[0165] Embodiment Four

[0166] The tunnel analysis and support design system provided in the embodiments includes:

[0167] a second division unit configured to divide the tunnel into deep and shallow buried tunnels using the underground engineering deep and shallow buried division method based on tunnel excavation effect provided in any of the embodiments;

[0168] a design unit configured to perform tunnel analysis and support design using different constitutive models according to the deep and shallow buried division result.

[0169] The tunnel analysis and support design system provided in the embodiments can realize the steps and processes of the tunnel analysis and support design method provided in any of the embodiments, and achieve the same technical effects, which will not be repeated here.

[0170] The above only describes the preferred embodiments of the present application and is not intended to limit the present application. The present application can have various modifications and changes for those skilled in the art. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present application shall be included in the protection scope of the present application.

Claims

1. A method for classifying the depth of underground engineering projects based on tunnel excavation effects, characterized in that, include: Step S1: Obtain tunnel size information and initial geostress field in the tunnel area; Step S2: Sample the tunnel area and conduct a conventional triaxial test from 0 to the maximum initial ground stress value to obtain the full stress-strain curve of the surrounding rock; Step S3: Based on the initial geostress field of the tunnel area, obtain the geostress information of the given engineering section to establish a three-dimensional numerical model of the tunnel. Use a constitutive model that considers strain softening to carry out numerical simulation and obtain the stress field after tunnel excavation. Step S4: Based on the full stress-strain curve and the stress field after tunnel excavation, perform a classification of deep and shallow burial, including: Based on the characteristic stress points in the full stress-strain curve, the full stress-strain curve is divided into multiple stages; Based on the characteristics of the full stress-strain curves after stage division and the stress distribution pattern in the stress field after tunnel excavation, the deep and shallow burial areas are divided as follows: If the stress distribution pattern in the stress field after tunnel excavation indicates that the surrounding rock is in an elastic state, then the tunnel is classified as a shallow tunnel. If the stress distribution pattern in the stress field after tunnel excavation indicates that the surrounding rock has entered a plastic state, then analyze the axial plastic strain of the surrounding rock: If the axial plastic strain is 0 after excavation, the formation of the plastic zone in the tunnel is mainly caused by tangential stress concentration, and the tunnel is classified as a mid-buried tunnel. If the axial plastic strain is not zero after excavation, the formation of the plastic zone in the tunnel is caused by the redistribution of tangential stress and axial stress, and the tunnel is classified as a deep-buried tunnel.

2. The method for classifying the depth of underground engineering burial as described in claim 1, characterized in that, In step S3: The constitutive model considering strain softening is any one of the following constitutive models: the Mohr-Coulomb constitutive model considering strain softening, the Hoek-Brown constitutive model considering strain softening, and the UHS constitutive model of unified strain hardening and strain softening elastoplasticity in surrounding rock.

3. The method for classifying the depth of underground engineering burial as described in claim 2, characterized in that, In the deep-buried tunnel: If all the full stress-strain curves obtained from conventional triaxial tests show post-peak softening, then the deep-buried tunnel is defined as the first deep-buried tunnel. If the full stress-strain curve obtained by conventional triaxial testing does not exhibit post-peak softening, then the deep-buried tunnel is defined as the second deep-buried tunnel.

4. A tunnel analysis and support design method, characterized in that, include: The method for classifying underground engineering depth and shallow burial based on tunnel excavation effect as described in any one of claims 1 to 3 is used to classify tunnels into depth and shallow burial. Based on the results of the classification of deep and shallow burial, different constitutive models are used for tunnel analysis and support design.

5. The tunnel analysis and support design method according to claim 4, characterized in that, Based on the structural classification of deep and shallow burial, different constitutive models are used for tunnel design, including: If the tunnel is a shallow tunnel, an elastic constitutive model is used in the tunnel analysis and support design; If the tunnel is a buried tunnel, the constitutive model that considers strain softening is used in the tunnel analysis and support design. If the tunnel is the deepest buried tunnel, the strain softening constitutive model that takes into account the influence of the intermediate principal stress is adopted in the tunnel analysis and support design. If the tunnel is the second deepest buried tunnel, the strain hardening-strain softening constitutive model that takes into account the influence of the principal stress is adopted in the tunnel analysis and support design.

6. A system for classifying the depth of underground engineering projects based on tunnel excavation effects, characterized in that, include: The acquisition unit is used to obtain tunnel size information and the initial geostress field of the tunnel area; The test unit is used to sample the tunnel area and conduct conventional triaxial tests from 0 to the maximum initial ground stress value to obtain the full stress-strain curve of the surrounding rock; The simulation unit is used to obtain the ground stress information of a given engineering section based on the initial ground stress field of the tunnel area, so as to establish a three-dimensional numerical model of the tunnel. The strain softening constitutive model is used to carry out numerical simulation to obtain the stress field after the tunnel is excavated. The first division unit is used to divide the tunnel into deep and shallow burial sections based on the full stress-strain curve and the stress field after tunnel excavation. The first partitioning unit is further used for: Based on the characteristic stress points in the full stress-strain curve, the full stress-strain curve is divided into multiple stages; Based on the characteristics of the full stress-strain curve after stage division and the stress distribution law in the stress field after tunnel excavation, the deep and shallow burial levels are divided as follows: If the stress distribution pattern in the stress field after tunnel excavation indicates that the surrounding rock is in an elastic state, then the tunnel is classified as a shallow tunnel. If the stress distribution pattern in the stress field after tunnel excavation indicates that the surrounding rock has entered a plastic state, then analyze the axial plastic strain of the surrounding rock: If the axial plastic strain is 0 after excavation, the formation of the plastic zone in the tunnel is mainly caused by tangential stress concentration, and the tunnel is classified as a mid-buried tunnel. If the axial plastic strain is not zero after excavation, the formation of the plastic zone in the tunnel is caused by the redistribution of tangential stress and axial stress, and the tunnel is classified as a deep-buried tunnel.

7. A tunnel analysis and support design system, characterized in that, include: The second division unit is used to divide the tunnel into deep and shallow burial sections using the underground engineering deep and shallow burial division method based on tunnel excavation effect as described in any one of claims 1 to 3. Design units are used to perform tunnel analysis and support design using different constitutive models based on the results of the deep and shallow burial classification.

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