Calibration method of concrete mechanical parameters, safety analysis method of tunnel structure, medium and equipment

Abstract

The invention relates to the technical field of concrete detection, in particular to a concrete mechanical parameter calibration method which comprises the following steps: preparing a concrete sample, and carrying out a concrete uniaxial loading test to obtain a stress-strain curve of the concrete sample and broken fracture surface characteristics; concrete mechanical parameters are obtained based on the stress-strain curve and the broken fracture surface characteristic calibration, wherein the concrete mechanical parameters comprise an elastic modulus, a Poisson's ratio, a concrete microcosmic friction coefficient, a damage resistance characteristic value, a damage characteristic value and a concrete post-peak toughness coefficient. According to the method, the concrete mechanical parameters are calibrated through the stress-strain curve obtained through the uniaxial loading test and the broken fracture surface characteristics, the problem of blindness of mechanical parameter determination under the uniaxial loading condition is solved, and compared with a method for obtaining the concrete mechanical parameters through a triaxial loading test, the method for determining the parameters based on the uniaxial loading test device has the advantages that the method is simple and convenient to operate. Manpower and material resources are saved, and the parameter accuracy is ensured.

Description

Technical Field

[0001] The present invention relates to the technical field of concrete detection, and in particular to a method for calibrating concrete mechanical parameters, a method for safety analysis of tunnel structures, a medium and equipment. Background Art

[0002] Fiber reinforced concrete improves its crack resistance and toughness by incorporating fiber materials. Its application in engineering is increasing. Understanding and modeling its constitutive behavior is crucial for analyzing the service safety of infrastructure. Research on fiber reinforced concrete constitutive models has been conducted.

[0003] The construction of concrete constitutive models can be categorized into empirical and theoretical approaches. Empirical methods primarily use fitting methods to describe the stress-strain relationship in concrete. While these methods can characterize the stress-strain relationship to a certain extent, they lack sufficient theoretical support. Theoretical methods derive the stress-strain relationship of concrete based on plasticity or damage development, providing a more solid theoretical foundation. The elastic-plastic damage model based on mesomechanics is a typical theoretical modeling approach that effectively describes the macroscopic mechanical properties of a material based on mesostructural changes, establishing a link between the material's macroscopic mechanical properties and mesostructural changes. When constructing an elastic-plastic damage model based on this theory, concrete is considered to be a composite consisting of a solid matrix and a series of coin-shaped microcracks. A concrete stiffness calculation method is constructed based on Eshelby inclusion theory and the distribution of microcracks in the matrix. A plasticity criterion is established by combining microcrack friction and slip, a damage criterion is established by considering damage resistance, and a reflection algorithm is used to numerically solve the constitutive model. Existing elastic-plastic damage models based on mesomechanics typically determine mesoscopic parameters based on triaxial test results. However, concrete mechanical properties tests are usually carried out using uniaxial loading, which leads to greater blindness in the determination of microscopic parameters, thus limiting the application of this model in concrete. Summary of the Invention

[0004] The present invention aims to provide a calibration method for accurately determining the mechanical parameters of concrete under uniaxial loading. The specific technical solution is as follows:

[0005] The present invention provides a method for calibrating concrete mechanical parameters, comprising the following steps: S1: preparing a concrete sample, carrying out a concrete uniaxial loading test, and obtaining a stress-strain curve of the concrete sample and fracture surface characteristics after destruction;

[0006] S2: The concrete mechanical parameters are obtained based on the stress-strain curve and the fracture surface characteristics after damage. The concrete mechanical parameters include elastic modulus, Poisson's ratio, concrete micro-friction coefficient, damage resistance characteristic value, damage characteristic value and concrete post-peak toughness coefficient.

[0007] Optionally, the S2 includes:

[0008] According to the stress-strain curve, the stress and strain at 35%-45% and 55%-65% of the peak stress are calculated to obtain the elastic modulus and Poisson's ratio of the concrete;

[0009] The angle α between the macroscopic fracture surface of concrete and the horizontal plane is measured based on the fracture surface characteristics after destruction, and the microscopic friction coefficient of concrete is calculated;

[0010] The damage resistance characteristic value, damage characteristic value and post-peak toughness coefficient of concrete are determined based on the concrete micro-friction coefficient.

[0011] Optionally, the angle α between the macroscopic fracture surface of the concrete and the horizontal plane is measured based on the fracture surface characteristics after destruction, and the microscopic friction coefficient of the concrete is calculated, specifically including:

[0012] Assuming that the macro friction coefficient of concrete is η macro Equal to the concrete micro-friction coefficient η, that is, η=η macro ;

[0013] Calculate the normal stress σ at the inclined section where the normal makes an arbitrary angle α with the x-axis α and shear stress τ α , the specific calculation formula is as follows:

[0014]

[0015] Where: x and σ y are the normal stresses in the x and y directions respectively; τ xy is the shear stress acting along the y direction on the plane normal along the x direction; σ α and τ α are the normal stress and shear stress at the oblique section, respectively;

[0016] In the uniaxial loading test, the normal force and tangential force on the side are both 0, that is, σ y =0,τ xy =0, we get:

[0017]

[0018] According to the Mohr-Coulomb criterion, the shear strength is expressed based on the normal stress. The specific calculation formula is as follows:

[0019] τ f =c+σ n tanφ;

[0020] Where: τ f is the shear strength; c is the cohesion; φ is the internal friction angle of concrete; σn is the normal stress on the inclined section; in the above formula, tanφ is the macro friction coefficient of concrete;

[0021] The concrete internal friction angle φ is calculated based on the Mohr circle theory. The specific calculation formula is as follows:

[0022]

[0023] The macro friction coefficient η of concrete is calculated based on the internal friction angle of concrete macro , the specific calculation formula is as follows:

[0024] η macro =tanφ;

[0025] Then the concrete micro-friction coefficient can be obtained, and the specific calculation formula is as follows:

[0026] η=η macro .

[0027] Optionally, the damage resistance characteristic value R dc The specific calculation formula is as follows:

[0028]

[0029] Where: σ1 is the axial stress; χ is a constant, K and G are the bulk modulus and shear modulus, respectively. E is the elastic modulus and v is the Poisson's ratio.

[0030] Optionally, the damage characteristic value d c The specific calculation formula is as follows:

[0031]

[0032] in: is the axial plastic strain, D 11 is the component of the plastic flow direction in the axial direction,

[0033] Optionally, the post-peak toughness coefficient n of concrete is determined by solving the intersection of two functions. The specific expressions of the two functions are as follows:

[0034]

[0035] in: The damage at the volume compression-expansion turning point is d cd The damage d at the stress peak point f The ratio of n is the post-peak toughness coefficient of concrete; к is the ratio of the damage resistance at the volume compression-expansion turning point to the stress peak point; for the above two functions, the independent variables are The dependent variable is n;

[0036] The specific calculation formula of elastic modulus is as follows:

[0037]

[0038] The specific calculation formula of Poisson's ratio is as follows:

[0039]

[0040] Where: ε1 is the axial strain, ε3 is the transverse strain, σ1 is the axial stress, σ p is the peak axial stress.

[0041] The present invention also provides a safety analysis method for a tunnel structure, which performs safety analysis based on the concrete mechanical parameters of the concrete sample obtained by the above calibration, specifically:

[0042] The concrete mechanical parameters of the calibrated concrete specimens are input into the existing elastic-plastic damage model to obtain the stress-strain evolution of the concrete in the tunnel structure.

[0043] Existing finite element software is used to conduct safety analysis of the tunnel structure based on the stress-strain evolution of the concrete of the tunnel structure.

[0044] The present invention also provides a readable storage medium having computer program instructions stored thereon, which implements the security analysis method of the tunnel structure as described above when the computer program instructions are executed by a processor.

[0045] The present invention also provides an electronic device, comprising: at least one processor, at least one memory, and computer program instructions stored in the memory, when the computer program instructions are executed by the processor, the security analysis method of the tunnel structure as described above is performed.

[0046] The technical solution of the present invention can be used to calibrate the mechanical parameters of concrete through the stress-strain curve obtained by the uniaxial loading test and the fracture surface characteristics after destruction, which solves the problem of blindness in determining the mechanical parameters under uniaxial loading. Compared with obtaining the mechanical parameters of concrete by using a triaxial loading test, the present invention determines the parameters based on a uniaxial loading test device, which saves manpower and material resources and ensures the accuracy of the parameters.

[0047] In addition to the above-described objects, features and advantages, the present invention has other objects, features and advantages. The present invention will be further described in detail below with reference to the accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0048] The accompanying drawings, which constitute part of this application, are intended to provide a further understanding of the present invention. The exemplary embodiments of the present invention and their descriptions are intended to explain the present invention and do not constitute an undue limitation of the present invention. In the accompanying drawings:

[0049] Figure 1 Schematic diagram of the formation mechanism of concrete macro cracks in an embodiment of the present invention. Figure 1 (a) is a schematic diagram before rupture, FIG. Figure 1 (b) is a schematic diagram of rupture. Figure 1 (c) is a schematic diagram after rupture;

[0050] Figure 2 This is a force analysis diagram of a concrete internal unit body in an embodiment of the present invention;

[0051] Figure 3 2. Schematic diagram of calculation of concrete meso-friction coefficient in an embodiment of the present invention;

[0052] Figure 4 is a concrete stress-strain curve diagram under different confining pressure conditions in an embodiment of the present invention;

[0053] Figure 5 is a characteristic diagram of the concrete fracture surface in an embodiment of the present invention, Figure 5 (a) is the fracture surface characteristic diagram of vibrated concrete (VC), Figure 5 (b) is the fracture surface characteristic diagram of self-compacting concrete (SCC), Figure 5 (c) is the fracture surface characteristic diagram of concrete (MS05) with 0.5% volume content of copper-plated microwires added. Figure 5 (d) is the fracture surface characteristic diagram of concrete (MS10) with 1.0% volume content of copper-plated microwires added;

[0054] Figure 6 is a comparison chart of the calculated and tested stress-strain relationships of different types of concrete in the embodiment of the present invention. Figure 6 (a) is a comparison chart of the calculated and tested values ​​of VC concrete. Figure 6 (b) is a comparison chart of the calculated and tested values ​​of SCC concrete. Figure 6 (c) is a comparison chart of the calculated and tested values ​​of MS05 concrete. Figure 6 (d) is a comparison chart of the calculated and tested values ​​of MS10 concrete. DETAILED DESCRIPTION

[0055] To make the objectives, features, and advantages of the present invention more readily apparent, the following detailed description of the present invention is provided with reference to the accompanying drawings. The accompanying drawings illustrate several embodiments of the present invention. However, the present invention may be implemented in many different forms and is not limited to the embodiments described herein.

[0056] In the present invention, unless otherwise expressly specified and limited, the terms "installed", "connected", "connected", "fixed" and the like should be understood in a broad sense. For example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection, or an indirect connection through an intermediate medium, or it can be a communication between the two components. For those of ordinary skill in the art, the specific meanings of the above terms in the present invention can be understood according to the specific circumstances. The terms "first" and "second" are used for descriptive purposes only and cannot be understood as indicating or implying relative importance or implicitly indicating the number of the indicated technical features. Therefore, the features defined as "first" and "second" may explicitly or implicitly include one or more of such features.

[0057] In the present invention, unless otherwise expressly specified and limited, a first feature being "above" or "below" a second feature may include the first and second features being in direct contact, or may include the first and second features being in contact not directly but through another feature between them. Moreover, a first feature being "above," "above," and "above" a second feature includes the first feature being directly above and obliquely above the second feature, or simply indicates that the first feature is higher in level than the second feature. A first feature being "below," "below," and "below" a second feature includes the first feature being directly below and obliquely below the second feature, or simply indicates that the first feature is lower in level than the second feature. The terms "vertical," "horizontal," "left," "right," "above," "below," and similar expressions are for illustrative purposes only and do not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operate in a specific orientation, and therefore should not be understood as limiting the present invention.

[0058] The embodiments of the present invention are described in detail below with reference to the accompanying drawings. However, the present invention can be implemented in many different ways as defined and covered by the claims.

[0059] In one embodiment, a method for calibrating concrete mechanical parameters includes the following steps:

[0060] S1: Prepare concrete specimens, conduct uniaxial loading tests on concrete, and obtain stress-strain curves and fracture surface characteristics of concrete specimens after failure;

[0061] S2: Calibrate concrete mechanical parameters based on stress-strain curves and fracture surface characteristics after damage, where concrete mechanical parameters include elastic modulus, Poisson's ratio, concrete micro-friction coefficient, damage resistance characteristic value, damage characteristic value and concrete post-peak toughness coefficient.

[0062] S2 includes:

[0063] According to the stress-strain curve, the stress and strain at 35%-45% and 55%-65% of the peak stress are calculated to obtain the elastic modulus and Poisson's ratio of the concrete. In this embodiment, the stress and strain at 40% and 60% are respectively taken.

[0064] See also Figure 2 and Figure 3 , the angle α between the macroscopic fracture surface of concrete and the horizontal plane is measured based on the fracture surface characteristics after destruction, and the microscopic friction coefficient of concrete is calculated; specifically including:

[0065] Calculate the normal stress σ at the inclined section where the normal makes an arbitrary angle α with the x-axis α and shear stress τ α , the specific calculation formula is as follows:

[0066]

[0067] Where: x and σ y are the normal stresses in the x and y directions respectively; τ xy is the shear stress acting along the y direction on the plane normal along the x direction; σ α and τ α are the normal stress and shear stress at the oblique section, respectively;

[0068] In the uniaxial loading test, the normal force and tangential force on the side are both 0, that is, σ y =0,τ xy =0, we get:

[0069]

[0070] According to the Mohr-Coulomb criterion, the shear strength is expressed based on the normal stress. The specific calculation formula is as follows:

[0071] τ f =c+σ n tanφ;

[0072] Where: τ f is the shear strength; c is the cohesion; φ is the internal friction angle of concrete; σ n is the normal stress on the inclined section; in the above formula, tanφ is the macro friction coefficient of concrete; when τ f =c+σ n When tanφ, the concrete is in the critical state of failure. f >c+σ n When tanφ, concrete begins to fail.

[0073] The concrete internal friction angle φ is calculated based on the Mohr circle theory. The specific calculation formula is as follows:

[0074]

[0075] The macro friction coefficient η of concrete is calculated based on the internal friction angle of concrete macro , the specific calculation formula is as follows:

[0076] η macro =tanφ;

[0077] Then the concrete micro-friction coefficient can be obtained, and the specific calculation formula is as follows:

[0078] η=η macro .

[0079] Damage resistance characteristic value R dc The specific calculation formula is as follows:

[0080]

[0081] Where: σ1 is the axial stress; χ is a constant, K and G are the bulk modulus and shear modulus, respectively. E is the elastic modulus and v is the Poisson's ratio.

[0082] Damage characteristic value d c The specific calculation formula is as follows:

[0083]

[0084] in: is the axial plastic strain, D 11 is the component of the plastic flow direction in the axial direction,

[0085] The post-peak toughness coefficient n of concrete is determined by solving the intersection of two functions. The specific expressions of the two functions are as follows:

[0086]

[0087] in: The damage at the volume compression-expansion turning point is d cd The damage d at the stress peak point f The ratio of n is the post-peak toughness coefficient; к is the ratio of the damage resistance at the volume compression-expansion turning point to the stress peak point.

[0088] For the above two functions, their independent variables are The dependent variable is n.

[0089] The specific calculation formula of elastic modulus is as follows:

[0090]

[0091] The specific calculation formula of Poisson's ratio is as follows:

[0092]

[0093] Where: ε1 is the axial strain, ε3 is the transverse strain, σ1 is the axial stress, σ p is the peak axial stress.

[0094] Concrete usually shows shear failure under external load. It is generally believed that the macroscopic shear fracture surface of concrete is formed by a series of microscopic cracks that extend and penetrate each other, such as Figure 1 When there is no macro shear crack in the concrete, the closed micro cracks in the area where the macro shear crack is located will slip under the action of stress, such as Figure 1 (a). The friction coefficient corresponding to each microcrack is the micro-friction coefficient. As the stress continues to increase, the slip of the microcracks gradually increases. After the stress reaches the peak, most closed microcracks begin to penetrate. When the macro shear crack is just formed, the upper and lower wedges are still in close contact, such as Figure 1 (b) At this point, there is friction between the upper and lower wedges, and the corresponding friction coefficient is the macro friction coefficient. Afterwards, further loading causes macro shear cracks in the concrete and causes the upper and lower wedges, which were originally tightly connected, to move relative to each other, as shown in Figure 2. Figure 1 (c). The formation mechanism of the macroscopic shear fracture surface indicates that the concrete macroscopic shear fracture surface is the result of a series of microscopic crack extensions. The macroscopic friction coefficient at the fracture surface should also be the average friction coefficient of the numerous microscopic microcracks in the region. Therefore, it can be assumed that the microscopic friction coefficient is consistent with the macroscopic friction coefficient. Steel fibers only take effect under significant tension. Before the macroscopic shear fracture surface appears, the internal deformation of the concrete is very small. This indicates that the influence of steel fibers on the concrete macroscopic shear failure surface is limited, and the aforementioned consistency between the microscopic and macroscopic friction coefficients still holds.

[0095] It should be noted that triaxial loading tests are usually used to analyze the mechanical properties of rocks, while concrete mechanical properties tests are usually uniaxial loading. This is because, for specific engineering structures such as tunnels, concrete is usually considered to be in a uniaxial stress state. Without carrying out triaxial loading of concrete, it is difficult to determine the η value and R from a theoretical perspective based on the test results. dc This means that it is impossible to theoretically determine two unknown quantities using a single formula. If forced, determination would require guesswork, leading to blindness in the determination of mechanical parameters under uniaxial loading. Although triaxial loading tests can be conducted to obtain concrete mechanical parameters, the data is very limited in scope, making triaxial loading tests uneconomical.

[0096] Compared to uniaxial loading, triaxial loading requires significant manpower and resources. Conducting concrete mechanical testing involves preparing concrete specimens and then testing concrete mechanical properties. Conventional uniaxial concrete testing requires specimen sizes such as 150mm cubes and 150*150*300 prisms. These specimen sizes are readily available; molds are simply poured into the molds and then cured. Conventional concrete mechanical testing can also be conducted using universal testing machines, which are relatively inexpensive. Triaxial testing requires the addition of cylindrical specimen preparation to conventional concrete specimen preparation. Specifically, cured 150mm cubes and 150*150*300 prisms are further processed into cylindrical specimens with a diameter of 50mm and a height of 100mm. This increases testing costs and specimen preparation time. Furthermore, mechanical property testing requires the use of triaxial loading equipment, which has significantly higher rental costs than universal testing machines.

[0097] This embodiment calibrates the concrete mechanical parameters by the stress-strain curve obtained through the uniaxial loading test and the fracture surface characteristics after destruction, which solves the problem of blindness in determining the mechanical parameters under uniaxial loading. Compared with obtaining the concrete mechanical parameters by using the triaxial loading test, the present invention determines the parameters based on the uniaxial loading test device, which saves manpower and material resources and ensures the accuracy of the parameters.

[0098] In this embodiment, concrete was prepared first, and then the concrete specimens were removed from the mold and placed in a standard curing room with a temperature of 20°C and a relative humidity of more than 95% for 28 days. After the curing was completed, a uniaxial compression test was carried out to obtain the following results: Figure 5 The concrete fracture surface features shown in Figure 2. Figure 4 As shown in the figure, it can be seen that the angle between the concrete fracture surface and the horizontal direction is 62.37°~64.45°. According to the angle, the concrete micro-friction coefficient η can be calculated. According to the concrete micro-friction coefficient, R dc Value, such as:

[0099]

[0100] Further calculation of d c , such as:

[0101]

[0102] Where, is the axial plastic strain, which can be obtained based on test data; D 11 is the component of the plastic flow direction in the axial direction,

[0103] Under uniaxial loading, the к value calculation method is as follows:

[0104]

[0105] The calculation parameters of various types of concrete are summarized in Table 1. The comparison between the calculated values ​​and the tested values ​​of the stress-strain relationship of different types of concrete is shown in Figure 6 It can be seen that the calculated values ​​of the concrete stress-strain curve are in good agreement with the tested values, indicating that the proposed concrete mesomechanics calibration method under uniaxial loading can effectively determine the calculation parameters of the mesomechanics-based elastic-plastic damage model, and the parameter calibration method proposed in this embodiment is reliable.

[0106] Table 1 Calculation parameters

[0107] Concrete type Elastic modulus E / GPa Poisson's ratio v η <![CDATA[R dc / %]]> <![CDATA[d c ]]> n VC 49.66 0.216 0.693 3.19 1.141 2.23 SCC 46.55 0.214 0.807 2.65 0.909 2.11 MS05 35.37 0.212 0.778 3.02 1.226 1.94 MS10 33.00 0.208 0.766 2.90 1.375 1.98

[0108] This embodiment also provides a tunnel structure safety analysis method, which performs safety analysis based on the concrete mechanical parameters of the calibrated concrete sample, specifically:

[0109] The concrete mechanical parameters of the calibrated concrete specimens are input into the existing elastic-plastic damage model to obtain the stress-strain evolution of the concrete in the tunnel structure.

[0110] Existing finite element software is used to conduct safety analysis of the tunnel structure based on the stress-strain evolution of the concrete of the tunnel structure.

[0111] Step 1: Use general finite element software to build a model representing the concrete and steel bars of the tunnel structure;

[0112] Step 2: Input the calculation parameters describing the evolution of concrete stress-strain and other parameters describing the characteristics of other components such as steel bars into the model constructed in step 1;

[0113] Step 3: Use the model constructed in step 1 to perform calculations to obtain the stress, deformation, etc. of the tunnel structure. Based on whether the stress, deformation, etc. exceed the allowable value, the safety can be analyzed.

[0114] This embodiment further includes a readable storage medium having computer program instructions stored thereon. When the computer program instructions are executed by a processor, the security analysis method of the tunnel structure described above is implemented.

[0115] This embodiment also includes an electronic device, including: at least one processor, at least one memory, and computer program instructions stored in the memory. When the computer program instructions are executed by the processor, the security analysis method of the tunnel structure described above is provided.

[0116] Exemplarily, the computer program may be divided into one or more modules / units, which are stored in the memory and executed by the processor to implement the present invention. The one or more modules / units may be a series of computer program instruction segments capable of implementing specific functions, and the instruction segments are used to describe the execution process of the computer program in the electronic device.

[0117] The electronic device may be a computing device such as a mobile phone, desktop computer, laptop, PDA, or cloud server. The electronic device may include, but is not limited to, a processor and memory. For example, the electronic device may also include input / output devices, network access devices, buses, etc.

[0118] The processor may be a central processing unit (CPU), other general-purpose processors, digital signal processors (DSP), application-specific integrated circuits (ASIC), field-programmable gate arrays (FPGA) or other programmable logic devices, discrete gate or transistor logic devices, discrete hardware components, etc. A general-purpose processor may be a microprocessor or any conventional processor, etc. The processor is the control center of the electronic device, connecting various parts of the entire electronic device using various interfaces and lines.

[0119] The memory can be used to store the computer program and / or module, and the processor implements the computer program by running or executing the computer program and / or module stored in the memory, and calling the data stored in the memory. The memory can mainly include a program storage area and a data storage area, wherein the program storage area can store an operating system, at least one application required for a function (such as a sound playback function, an image playback function, etc.); the data storage area can store data created according to the use of the computer (such as calculation result files, etc.). In addition, the memory can include a high-speed random access memory, and can also include a non-volatile memory, such as a hard disk, a memory, a plug-in hard disk, a smart memory card (Smart Media Card, SMC), a secure digital (Secure Digital, SD) card, a flash card (Flash Card), at least one disk storage device, a flash memory device, or other volatile solid-state storage device.

[0120] Wherein, if the module / unit integrated in the electronic device is implemented in the form of a software functional unit and sold or used as an independent product, it can be stored in a computer-readable storage medium. Based on this understanding, the present invention implements all or part of the process in the above-mentioned embodiment method, and can also be completed by instructing the relevant hardware through a computer program. The computer program can be stored in a readable storage medium, and the computer program can implement the steps of the above-mentioned various method embodiments when executed by the processor. Wherein, the computer program includes computer program code, and the computer program code can be in source code form, object code form, executable file or some intermediate form, etc. The computer-readable medium may include: any entity or device that can carry the computer program code, a recording medium, a USB flash drive, a mobile hard disk, a magnetic disk, an optical disk, a computer memory, a read-only memory (ROM), a random access memory (RAM), an electrical carrier signal, a telecommunications signal, and a software distribution medium, etc.

[0121] The foregoing description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. Those skilled in the art will readily appreciate that various modifications and variations of the present invention are possible. Any modifications, equivalent substitutions, or improvements made within the spirit and principles of the present invention shall be included within the scope of protection of the present invention.

Claims

1. A method for calibrating concrete mechanical parameters, characterized in that: The following steps are involved: S1: Prepare concrete specimens, conduct uniaxial loading tests on concrete, and obtain stress-strain curves and fracture surface characteristics of concrete specimens after failure; S2: The concrete mechanical parameters are obtained based on the stress-strain curve and the fracture surface characteristics after damage. The concrete mechanical parameters include elastic modulus, Poisson's ratio, concrete micro-friction coefficient, damage resistance characteristic value, damage characteristic value and concrete post-peak toughness coefficient.

2. The method for calibrating concrete mechanical parameters according to claim 1, characterized in that: The S2 includes: According to the stress-strain curve, the stress and strain at 35%-45% and 55%-65% of the peak stress are calculated to obtain the elastic modulus and Poisson's ratio of the concrete; The angle α between the macroscopic fracture surface of concrete and the horizontal plane is measured based on the fracture surface characteristics after destruction, and the microscopic friction coefficient of concrete is calculated; The damage resistance characteristic value, damage characteristic value and post-peak toughness coefficient of concrete are determined based on the concrete micro-friction coefficient.

3. The method for calibrating concrete mechanical parameters according to claim 2, characterized in that: The angle α between the macroscopic fracture surface of concrete and the horizontal plane is measured based on the fracture surface characteristics after damage, and the microscopic friction coefficient of concrete is calculated, specifically including: Assuming that the macro friction coefficient of concrete is η macro Equal to the concrete micro-friction coefficient η, that is, η=η macro ; Calculate the normal stress σ at the inclined section where the normal makes an arbitrary angle α with the x-axis α and shear stress τ α , the specific calculation formula is as follows: Where: x and σ y are the normal stresses in the x and y directions respectively; τ xy is the shear stress acting along the y direction on the plane normal along the x direction; σ α and τ α are the normal stress and shear stress at the oblique section, respectively; In the uniaxial loading test, the normal force and tangential force on the side are both 0, that is, σ y =0,τ xy =0, we get: According to the Mohr-Coulomb criterion, the shear strength is expressed based on the normal stress. The specific calculation formula is as follows: t f =c+σ n tanf; Where: τ f is the shear strength; c is the cohesion; φ is the internal friction angle of concrete; σ n is the normal stress on the inclined section; in the above formula, tanφ is the macro friction coefficient of concrete; The concrete internal friction angle φ is calculated based on the Mohr circle theory. The specific calculation formula is as follows: The macro friction coefficient η of concrete is calculated based on the internal friction angle of concrete macro , the specific calculation formula is as follows: or macro =tanφ; Then the concrete micro-friction coefficient can be obtained, and the specific calculation formula is as follows: the=the macro 。 4. The method for calibrating concrete mechanical parameters according to claim 3, characterized in that: Damage resistance characteristic value R dc The specific calculation formula is as follows: Where: σ1 is the axial stress; χ is a constant, K and G are the bulk modulus and shear modulus, respectively. E is the elastic modulus and v is the Poisson's ratio.

5. The method for calibrating concrete mechanical parameters according to claim 4, characterized in that: Damage characteristic value d c The specific calculation formula is as follows: in: is the axial plastic strain, D 11 is the component of the plastic flow direction in the axial direction, 6. The method for calibrating concrete mechanical parameters according to claim 5, characterized in that: The post-peak toughness coefficient n of concrete is determined by solving the intersection of two functions. The specific expressions of the two functions are as follows: in: The damage at the volume compression-expansion turning point is d cd The damage d at the stress peak point f The ratio of n is the post-peak toughness coefficient of concrete; к is the ratio of the damage resistance at the volume compression-expansion turning point to the stress peak point; for the above two functions, the independent variables are The dependent variable is n; The specific calculation formula of elastic modulus is as follows: The specific calculation formula of Poisson's ratio is as follows: Where: ε1 is the axial strain, ε3 is the transverse strain, σ1 is the axial stress, σ p is the peak axial stress.

7. A tunnel structure safety analysis method, characterized in that: A safety analysis is performed based on the concrete mechanical parameters of the concrete sample calibrated as claimed in claims 1-6, specifically: The concrete mechanical parameters of the calibrated concrete specimens are input into the existing elastic-plastic damage model to obtain the stress-strain evolution of the concrete in the tunnel structure. Existing finite element software is used to conduct safety analysis of the tunnel structure based on the stress-strain evolution of the concrete of the tunnel structure.

8. A readable storage medium, characterized in that: Computer program instructions are stored thereon, and when the computer program instructions are executed by a processor, the tunnel structure safety analysis method according to claim 7 is implemented.

9. An electronic device, characterized in that: include: At least one processor, at least one memory, and computer program instructions stored in the memory, when the computer program instructions are executed by the processor, the tunnel structure safety analysis method according to claim 7.

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