A tunnel system safety evaluation method based on unit danger coefficient

Abstract

This application provides a method for safety evaluation of tunnel systems based on unit hazard coefficients, including the following specific steps: defining the hazard coefficients of surrounding rock and lining structural units; defining the hazard coefficients of anchor bolt units, and defining the hazard coefficients of anchor bolt bodies and anchor bolt interfaces; defining the "surrounding rock-anchor bolt-lining" system and its safety evaluation index, defining the rock mass, anchor bolts, and lining within the anchor bolt reinforcement range as the "surrounding rock-anchor bolt-lining" system, and establishing the hazard coefficient index of the "surrounding rock-anchor bolt-lining" system; establishing a damage level classification standard, and combining the results of gravity dam seismic damage analysis to establish a tunnel damage level classification standard based on unit hazard coefficients (EDC). This application can evaluate the "surrounding rock-anchor bolt-lining" system as a whole, and can intuitively give the degree of danger of surrounding rock, anchor bolts, lining, and the "surrounding rock-anchor bolt-lining" system in various parts of the tunnel, which is very convenient for assessing tunnel stability and guiding engineering design.

Description

Technical Field

[0001] This application relates to the field of stability analysis and safety evaluation of underground caverns, specifically to a safety evaluation method for tunnel systems based on unit hazard coefficients. Background Technology

[0002] Large-scale hydropower projects in western China include numerous complex hydraulic tunnels. The surrounding rock, anchor bolts, and lining of these tunnels form a combined system. Under the frequent and intense seismic activity in western China, the stability and reliability of the "surrounding rock-anchor bolt-lining" system are extremely important issues. A reasonable evaluation of its safety and reliability is of great significance for the seismic design, safe operation, and post-earthquake reinforcement of hydraulic tunnels.

[0003] Anchor bolts connect the tunnel surrounding rock and lining to form a combined system that shares the external load. Their mechanical response is not only related to the inherent mechanical behavior of the materials but also closely related to the complex contact behaviors between the anchor bolt and the surrounding rock, the surrounding rock and the lining, and between the anchor bolt and the lining. During an earthquake, different failure modes may coexist, such as damage to the surrounding rock and lining, separation of the surrounding rock and lining, anchor bolt breakage, and anchor bolt shearing, making the earthquake failure mode exceptionally complex. Currently, most safety assessments of tunnels treat the surrounding rock or lining structure as a single analysis object, using indicators such as displacement, stress, and plastic zone of the surrounding rock and structure for stability evaluation, without considering the "surrounding rock-anchor bolt-lining" system holistically. Summary of the Invention

[0004] The purpose of this application is to provide a method for evaluating the safety of tunnel systems based on unit hazard coefficients, which can intuitively and reasonably evaluate the safety and reliability of tunnels, provide technical support for engineering decisions, and strongly guide engineering design.

[0005] To achieve the above objectives, this application provides the following technical solution:

[0006] This application provides a method for safety evaluation of tunnel systems based on unit hazard coefficients, including the following specific steps:

[0007] Define the hazard factor of the surrounding rock and lining structural unit, and define the hazard factor (EDC) of the surrounding rock and lining structural unit. r This is used to quantitatively evaluate the degree of danger of an element from the yield surface within the elastic zone; the larger the value, the more dangerous the element.

[0008] Define the risk factor of the anchor bolt element, define the risk factors of the anchor bolt body and the anchor bolt interface, and take the larger value as the risk factor of the anchor bolt element.

[0009] Define the "surrounding rock-anchor bolt-lining" system and its safety evaluation index. Define the rock mass, anchor bolt and lining within the anchor bolt reinforcement range as the "surrounding rock-anchor bolt-lining" system. Based on the risk coefficient of the surrounding rock and lining structural unit and the risk coefficient of the anchor bolt unit, establish the risk coefficient index of the "surrounding rock-anchor bolt-lining" system by averaging the unit volume.

[0010] Establish a damage level classification standard, and combine the results of gravity dam seismic damage analysis to establish a tunnel damage level classification standard based on the element hazard coefficient (EDC).

[0011] The defined risk factor for the surrounding rock and lining structure unit is specifically as follows:

[0012] Damage to the surrounding rock and lining structural units is an irreversible process involving the continuous initiation, development, and eventual connection of micro-cracks and micro-voids within the rock mass to form macroscopic cracks. The damage coefficient is considered a monotonic function of cumulative plastic deviatoric strain.

[0013]

[0014] In the formula: This is the limiting damage coefficient; and The damage constant; It is the deviatoric tensor of plastic strain. , and This can be determined through experimentation;

[0015] The deformation process of the surrounding rock and lining structural units is divided into an elastic stage and a plastic damage stage.

[0016] In the elastic stage, the yield proximity is defined as the distance from the stress point of the surrounding rock and lining structural unit to the yield surface. The hazard factor of the surrounding rock and lining structural unit in the elastic zone is defined as... ,in, and They are respectively and The second invariant of the deviatoric stress at a point;

[0017] During the plastic damage stage, the hazard factor of the surrounding rock and lining structural unit is defined as EDC. r = 1 + d.

[0018] The defined risk factor for the anchor bolt unit is specifically as follows:

[0019] The risk factors for the anchor bolt body and the anchor bolt interface are defined separately, and the larger value is taken as the risk factor for the anchor bolt element.

[0020] The element hazard factor of the anchor rod is defined as follows:

[0021]

[0022] The element hazard factor of the anchor bolt interface can be defined as follows:

[0023]

[0024] The element safety factor of the anchor bolt element is expressed as: , The axial strain of the anchor rod; The ultimate elastic tensile strain of the anchor bolt; This represents the strain corresponding to the anchor bolt breaking. This represents the relative slippage at the anchor bolt interface; The relative slip corresponding to the peak shear strength; The relative slip amount corresponding to the residual strength fracture initiation point.

[0025] The specific risk factor indicators for establishing the "surrounding rock-anchor bolt-lining" system are as follows:

[0026]

[0027] In the formula: The risk factor of the system; , and These are the number of surrounding rock, anchor bolts, and lining units within the area of ​​interest. , and These refer to the volumes of the surrounding rock, anchor bolts, and lining units within the area of ​​interest. , and These are the unit hazard coefficients for the surrounding rock, anchor bolts, and lining units within the area of ​​concern. The values ​​of the magnitude are distributed in the range of [0, 2]. The larger the value, the greater the disturbance of the system and the lower the security.

[0028] In the steps of establishing the damage level classification standard, 1.05, 1.2, 1.5, and 1.8 are used as EDC limits.

[0029] Compared with the prior art, the beneficial effects of the present invention are: the safety evaluation method for the tunnel “surrounding rock-anchor bolt-lining” system proposed in the present invention can evaluate the degree of danger of the surrounding rock, anchor bolt and lining at the unit scale, and can also evaluate the danger of the “surrounding rock-anchor bolt-lining” as a system, which has important guiding significance for engineering design. Attached Figure Description

[0030] To more clearly illustrate the technical solutions of the embodiments of this application, the accompanying drawings used in the embodiments of this application will be briefly introduced below. It should be understood that the following drawings only show some embodiments of this application and should not be regarded as a limitation of the scope. For those skilled in the art, other related drawings can be obtained based on these drawings without creative effort.

[0031] Figure 1 A schematic diagram of the Mohr-Coulomb yield surface on the π plane;

[0032] Figure 2 This is a schematic diagram of a full-length bonded anchor mechanical analysis system;

[0033] Figure 3 This is a schematic diagram of the trilinear model of the anchor bolt.

[0034] Figure 4 A schematic diagram of the trilinear model of the anchor bolt interface;

[0035] Figure 5 Finite element model and anchor bolt layout diagram;

[0036] Figure 6 Distribution map of EDC values ​​in the surrounding rocks of the cave;

[0037] Figure 7 Distribution diagram of EDC values ​​for anchor bolts and lining;

[0038] Figure 8 This is a flowchart of a method according to an embodiment of the present invention. Detailed Implementation

[0039] The technical solutions of the embodiments of this application will now be described with reference to the accompanying drawings. It should be noted that similar reference numerals and letters in the following drawings indicate similar items; therefore, once an item is defined in one drawing, it does not need to be further defined and explained in subsequent drawings.

[0040] The terms “comprising,” “including,” or any other variations thereof are intended to cover a non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or apparatus. Without further limitation, an element defined by the phrase “comprising one…” does not exclude the presence of other identical elements in the process, method, article, or apparatus that includes said element.

[0041] like Figure 8As shown, this invention proposes a safety evaluation method for a tunnel "surrounding rock-anchor bolt-lining" system based on unit hazard coefficients. The method mainly includes: proposing unit hazard coefficient indices with clear physical meaning for the surrounding rock, anchor bolts, and lining structures; considering the "surrounding rock-anchor bolt-lining" system as a whole, and obtaining the hazard coefficient of the tunnel "surrounding rock-anchor bolt-lining" system by averaging the volumes of the three parts; and establishing a mapping relationship between unit hazard coefficients and damage levels to evaluate the safety level of individual objects such as the surrounding rock, anchor bolts, and lining, as well as the "surrounding rock-anchor bolt-lining" system.

[0042] The specific implementation steps of this invention are as follows:

[0043] (1) Definition and calculation formula of the hazard factor of surrounding rock and lining structure unit

[0044] For frictional materials such as surrounding rock and lining structures, the initiation, propagation, and connection of micro-cracks within the material are fundamental structural changes during stress. Due to initial defects in the material, uneven initial micro-cracks exist within the rock mass. As the load gradually increases, these micro-cracks gradually initiate and propagate, eventually connecting to form macro-cracks, leading to material failure. The presence of these micro-cracks creates stress-relief zones, the volume of which gradually approaches the total material volume with increasing load. This failure process can be characterized by a damage coefficient d, and its elastoplastic damage constitutive relation can be expressed as:

[0045]

[0046] In the formula: The effective stress tensor of the element; The deviator tensor is the effective stress of the element; Kronecker symbol; The damage stress tensor of the element; The stress is three times the volumetric stress. The effective stress of the element is assumed to satisfy the Mohr-Coulomb yield criterion, i.e.

[0047]

[0048] In the formula: For cohesion; It is the internal friction angle; , , These are the first, second, and third principal stresses, respectively. and These are the second and third invariants of the deviatoric stress, respectively.

[0049] Damage to the surrounding rock and lining structure is an irreversible process involving the continuous initiation, development, and eventual connection of micro-cracks and micro-voids within the rock mass to form macroscopic cracks. The damage coefficient can be considered a monotonic function of the cumulative plastic deviatoric strain.

[0050]

[0051] In the formula: This is the limiting damage coefficient; and The damage constant; The deviatoric tensor for plastic strain; To accumulate plastic deviatoric strain. , and It can be determined through experiments.

[0052] Based on the above theory, the deformation process of the surrounding rock and lining structural unit can be divided into an elastic stage and a plastic damage stage. In the elastic stage, the yield proximity can be defined to describe the distance from the stress point of the element to the yield surface. Specifically, keeping the Lode angle constant on the π plane, it is the ratio of the distance from the stress point to the yield surface along the line connecting the stress point and the origin of the π plane to the distance from the origin of the π plane to the yield surface. For example... Figure 1 As shown, the yield proximity YAI = A0A1 / OA 1， Its complementary parameters are According to the elastoplastic theory, , Therefore, the element hazard factor of the elastic zone element is defined as follows: .in, and They are respectively and The second invariant of the deviatoric stress at a point. If we keep the Lode angle constant in the plane and set equation (2) to zero, then The expression is

[0053]

[0054] In the formula: c is the cohesive force; It is the internal friction angle; The definition is shown in equation (2).

[0055] Risk Factor (EDC) of Surrounding Rock and Lining Structure Unit r This can be used to quantitatively evaluate the degree of danger of an element from the yield surface within the elastic zone; the larger the value, the more dangerous the element. For elements entering the plastic state, the damage characteristics of the element are further considered. In this case, the element danger factor is defined as EDC. r= 1 + d. EDC r The value of is distributed within [0, 2]. The larger the value, the more dangerous the element is. When the value is less than 1.0, it indicates that the element is in an elastic state.

[0056] It should be noted that, since there are many constitutive models available for nonlinear numerical analysis of surrounding rock and lining structures, this invention only uses the elastoplastic damage constitutive model based on the Mohr-Coulomb yield criterion as an example to derive the formula for calculating the element hazard coefficient of the surrounding rock and lining elements. However, this invention still has universality, and the derivation ideas and methods can be transferred to other models.

[0057] (2) Definition and calculation formula of the hazard factor of anchor bolt unit

[0058] The ultimate tensile strength of a fully bonded anchor depends on both the tensile strength of the anchor body and the shear strength of the interface (anchor-mortar interface or mortar-surrounding rock interface). The failure mechanisms of the anchor-mortar interface and the mortar-surrounding rock interface are the same, and the mortar layer thickness is relatively small. Therefore, the two interfaces can be combined into one, meaning the mechanical behavior of the anchor-mortar interface and the mortar-surrounding rock interface is equivalent to that of the anchor-mortar interface. The mechanical behavior of a fully bonded anchor can be... Figure 2 Intuitive representation.

[0059] To realistically simulate anchor bolt behavior, both the tension of the bolt itself and the shear behavior at the bolt-mortar interface must be considered. The anchor bolt element method is currently the most widely used method for simulating the tensile behavior of anchor bolts. As a metallic material, anchor bolts undergo elastic deformation, plastic hardening, and tensile fracture under tensile loads. In practical simulations, the plastic hardening phenomenon of anchor bolts can be neglected. Figure 3 As shown, the deformation stages of the anchor bolt can be divided into: Stage For the linear elastic stage, stage This is the plastic stage, stage This is the large deformation-fracture stage, as shown in the figure. The axial strain of the anchor rod; The ultimate elastic tensile strain of the anchor bolt; This represents the strain corresponding to the anchor bolt breaking. This refers to the tensile force of the anchor bolt. This represents the ultimate tensile force of the anchor bolt. The Young's modulus of the anchor bolt; This represents the cross-sectional area of ​​the anchor bolt.

[0060] For the deformation behavior of the anchor bolt interface, it can be used as follows: Figure 4 The trilinear model shown represents stage I as the linear elastic stage, stage II as the slip softening stage, and stage III as the residual deformation stage. (See figure.) This represents the relative slippage at the anchor bolt interface; The relative slip corresponding to the peak shear strength; The relative slip amount corresponding to the residual strength fracture initiation point; Shear stiffness at the anchor bolt interface; The length of the anchor bolt unit; The shear force at the anchor bolt interface; This represents the ultimate shear force at the anchor bolt interface; This represents the residual shear force at the anchor bolt interface.

[0061] Therefore, similar to the definition of the hazard factor of a rock mass element, the hazard factors of the anchor bolt body and the anchor bolt interface can be defined separately, and the larger value can be taken as the hazard factor of the anchor bolt element.

[0062] The element hazard factor of the anchor bolt can be defined as follows:

[0063]

[0064] The element hazard factor of the anchor bolt interface can be defined as follows:

[0065]

[0066] The element safety factor of the anchor bolt element can be expressed as: Its value is also distributed in the range of [0, 2]. The larger the value, the more dangerous the unit is.

[0067] It should be noted that: for anchor bolt structures, there are many existing research models that describe the nonlinear behavior of the anchor bolt itself and the anchor bolt interface, and are not limited to the trilinear model in this invention. However, this invention still has universality because the risk factor index established in this invention is based on the axial strain of the anchor bolt and the shear slip of the anchor bolt interface, and is not affected by the model itself, and can be fully transferred to other models.

[0068] (3) The “surrounding rock-anchor bolt-lining” system and its safety evaluation indicators

[0069] The rock mass, anchor bolt, and lining within the anchor bolt reinforcement area are considered to constitute a "surrounding rock-anchor bolt-lining" system, without considering the rock mass outside the anchor bolt reinforcement area. Based on the established hazard factor indices for the surrounding rock, anchor bolt, and lining units, a hazard factor index for the "surrounding rock-anchor bolt-lining" system can be established through unit volume averaging, specifically as follows:

[0070]

[0071] In the formula: The risk factor of the system; , and These are the number of surrounding rock, anchor bolts, and lining units within the area of ​​interest. , and These refer to the volumes of the surrounding rock, anchor bolts, and lining units within the area of ​​interest. , and These are the element hazard factors (EDCs) for the surrounding rock, anchor bolts, and lining units within the area of ​​concern. c This refers to the unit hazard factor of the tunnel lining structure. Its calculation method is the same as that of the unit hazard factor of the rock mass element. The different symbols used here are to distinguish it from the unit hazard factor of the rock mass element. The values ​​are still distributed in the range of [0, 2]. The larger the value, the greater the disturbance of the system and the lower the security.

[0072] (4) Standards for classifying damage levels

[0073] Based on the analysis results of earthquake damage to gravity dams, this invention establishes a tunnel damage level classification standard based on EDC, using 1.05, 1.2, 1.5, and 1.8 as EDC limits, as shown in Table 1.

[0074] Table 1. Tunnel Damage Levels Based on EDC

[0075]

[0076] This invention uses a water diversion tunnel of a hydropower station as an example to illustrate the specific implementation process of the invention and verify its rationality. The water diversion tunnel of the hydropower station is 7126 m long, with undulating ground along its route, passing through different geological structures. This tunnel section is located in the middle of the water diversion system, adopts a circular cross-section structure, with an excavated diameter of 10.2 m, a lined tunnel diameter of 9.0 m, a tunnel center elevation of 32.00 m, a tunnel depth of 241.67 m, and a maximum internal water head of 135.24 m. It is a reinforced concrete structure, with a lining thickness of 0.6 m, using C25 concrete. The three-dimensional finite element model of the water diversion tunnel uses eight-node hexahedral elements, resulting in 59584 isoparametric elements and 64003 nodes. Model scope and coordinate system: The x-axis extends from -90.0 m to 90.0 m, perpendicular to the tunnel axis; the y-axis extends from -90.0 m to 90.0 m, coinciding with the tunnel axis, with the direction of water flow being positive; the z-axis extends from -48.0 m to 273.67 m, parallel to the geodetic coordinate system. The overall three-dimensional finite element model of the water diversion tunnel is as follows: Figure 5 As shown.

[0077] The physical and mechanical parameters of the surrounding rock and lining are shown in Table 2. The physical and mechanical parameters of the anchor bolt are: density 7900 kg / m³. 3The Young's modulus is 200 GPa, Poisson's ratio is 0.2, yield strength is 400 MPa, and tensile failure strain is 0.15. The y = 0 plane was selected as the monitoring section, and the top, bottom, and waist of this section were selected as three monitoring points.

[0078] Table 2 Physical and mechanical parameters of surrounding rock and lining

[0079]

[0080] In the calculation, the initial stress field was considered as self-weight stress. Anchor bolts were applied promptly after excavation, and the lining structure was applied after the surrounding rock deformation converged. The influence of surrounding rock pressure on the lining was not considered. The lining was subjected to a water head of approximately 150 m. The calculated EDC distribution of the surrounding rock around the tunnel is shown in [reference needed]. Figure 6 As shown, the EDC value distribution of anchor bolts and linings is shown in the figure. Figure 7 As shown.

[0081] from Figure 6 As can be seen from the data, the EDC value of the surrounding rock in the tunnel is relatively large at the waist of the tunnel, while it is relatively small at the top and bottom. The maximum EDC value of the surrounding rock reaches 1.389. According to Table 1, the damage level of the rock mass unit at this location is moderate. Figure 7 As can be seen from the data, under the action of internal water and self-weight load, the EDC of the lining structure shows a pattern of smaller value at the top, followed by the middle, and the largest value at the bottom. The maximum EDC value of the lining structure reaches about 1.80, mainly distributed at the bottom of the lining. According to Table 1, the failure level of the lining unit at this location is complete failure. The EDC value of the anchor bolts shows a pattern of larger value at the middle of the tunnel and relatively smaller value at the top and bottom of the tunnel. In addition, there are obvious differences in the distribution of anchor bolt EDC values ​​along the length of the anchor bolts. Specifically, the EDC value of the anchor bolts near the excavation face is relatively large, while the EDC value of the anchor bolts in the internal rock mass is relatively small. The EDC value of the anchor bolts near the excavation face is basically between 1.8 and 2.0. At this time, the anchor bolt unit can be considered to be completely failed.

[0082] According to formula (7), the EDC* values ​​of the tunnel "surrounding rock-anchor bolt-lining" system at the top, middle, and bottom of the tunnel were calculated, and the results are summarized in Table 3. It can be seen that the EDC* values ​​of the "surrounding rock-anchor bolt-lining" system at the three characteristic locations are all less than 1.05, and the damage level is basically intact, which indicates that the system has good safety and stability. This is quite different from the evaluation results of individual objects such as surrounding rock, anchor bolt, and lining in the system. This is consistent with the basic understanding that in underground caverns, the damage to the cavern is mainly local damage, and the probability of system instability is very small. The safety evaluation method of the tunnel "surrounding rock-anchor bolt-lining" system proposed in this invention can evaluate the degree of danger of surrounding rock, anchor bolt, and lining at the unit scale, and can also evaluate the danger of the "surrounding rock-anchor bolt-lining" as a system, which has important guiding significance for engineering design.

[0083] Table 3 Safety evaluation results of "surrounding rock-anchor bolt-lining" in characteristic parts of the tunnel

[0084]

[0085] The above description is merely an embodiment of this application and is not intended to limit the scope of protection of this application. Various modifications and variations can be made to this application by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of this application should be included within the scope of protection of this application.

Claims

1. A method for safety evaluation of tunnel systems based on unit hazard coefficients, characterized in that, The specific steps include the following: Define the hazard factor for the surrounding rock and lining structure unit. The hazard factor for the surrounding rock and lining structure unit is used to quantitatively evaluate the degree of hazard of the unit. Define the risk factor of the anchor bolt element, define the risk factors of the anchor bolt body and the anchor bolt interface, and take the larger value as the risk factor of the anchor bolt element. Define the "surrounding rock-anchor bolt-lining" system and its safety evaluation index. Define the rock mass, anchor bolt and lining within the anchor bolt reinforcement range as the "surrounding rock-anchor bolt-lining" system. Based on the risk coefficient of the surrounding rock and lining structural unit and the risk coefficient of the anchor bolt unit, establish the risk coefficient index of the "surrounding rock-anchor bolt-lining" system by averaging the unit volume. Establish a damage level classification standard, and combine the results of gravity dam earthquake damage analysis to establish a tunnel damage level classification standard based on the unit hazard coefficient; The defined risk factor for the anchor bolt unit is specifically as follows: The risk factors for the anchor bolt body and the anchor bolt interface are defined separately, and the larger value is taken as the risk factor for the anchor bolt element. The element hazard factor of the anchor rod is defined as follows: ， The element hazard factor of the anchor bolt interface is defined as follows: ， The element safety factor of the anchor bolt element is expressed as: , The axial strain of the anchor rod; The ultimate elastic tensile strain of the anchor bolt; This represents the strain corresponding to the anchor bolt breaking. This represents the relative slippage at the anchor bolt interface; The relative slip corresponding to the peak shear strength; The relative slip amount corresponding to the starting point of residual strength.

2. The method for safety evaluation of tunnel systems based on unit hazard coefficients according to claim 1, characterized in that, The defined risk factor for the surrounding rock and lining structure unit is specifically as follows: Damage to the surrounding rock and lining structural units is an irreversible process involving the continuous initiation, development, and eventual connection of micro-cracks and micro-voids within the rock mass to form macroscopic cracks. The damage coefficient is considered a monotonic function of cumulative plastic deviatoric strain. ， In the formula: This is the limiting damage coefficient; and The damage constant; For the deviatoric tensor of plastic strain, , and This can be determined through experimentation; The deformation process of the surrounding rock and lining structural units is divided into an elastic stage and a plastic damage stage. In the elastic stage, the yield proximity is defined as the distance from the stress point of the surrounding rock and lining structural unit to the yield surface. The hazard factor of the surrounding rock and lining structural unit in the elastic zone is defined as... ,in, and They are respectively and The second invariant of the deviatoric stress at a point; During the plastic damage stage, the hazard factor of the surrounding rock and lining structural unit is defined as EDC. r = 1 + d.

3. The method for safety evaluation of tunnel systems based on unit hazard coefficients according to claim 1, characterized in that, The specific risk factor indicators for establishing the "surrounding rock-anchor bolt-lining" system are as follows: ， In the formula: The risk factor of the system; , and These are the number of surrounding rock, anchor bolts, and lining units within the area of ​​interest. , and These refer to the volumes of the surrounding rock, anchor bolts, and lining units within the area of ​​interest. , and These are the unit hazard coefficients for the surrounding rock, anchor bolts, and lining units within the area of ​​concern. The values ​​of the magnitude are distributed in the range of [0, 2]. The larger the value, the greater the disturbance of the system and the lower the security.

4. The method for safety evaluation of tunnel systems based on unit hazard coefficients according to claim 1, characterized in that, In the steps of establishing the damage level classification standard, 1.05, 1.2, 1.5, and 1.8 are used as EDC limits.

Images