Safety state evaluation method and system for utility tunnel

Abstract

The present invention relates to the technical field of safety state evaluation methods for utility tunnels. Provided are a safety state evaluation method and system for a utility tunnel. The method comprises: using a steady-state heat release method to calculate a simulated temperature at each three-dimensional grid node; using a finite difference method to calculate a temperature field distribution coefficient at each three-dimensional grid node, and acquiring temperature distribution coefficients at center points of three-dimensional grids by means of an arithmetic mean method; and using a coupled damage method to construct a coupling coefficient matrix at any grid location, calculating equivalent damage energy at any grid location by means of an inner product method, and normalizing and mapping the equivalent damage energy to a safety coefficient at any grid center point. Three-dimensional grid discretization enables more accurate capture of complex geometric features of a utility tunnel structure, and clear marking of locations of potential fire sources, thereby improving the efficiency of hidden danger identification by means of targeted monitoring, and realizing high-precision calculation of a simulated temperature field under complex boundary conditions; and equivalent damage energy is mapped to dimensionless safety coefficients, thereby realizing cross-regional risk comparability.

Description

Safety Status Evaluation Method and System for Integrated Utility Tunnels Technical Field

[0001] This invention relates to the technical field of safety status evaluation methods for integrated utility tunnels, specifically to a safety status evaluation method and system for integrated utility tunnels. Background Technology

[0002] Traditional safety assessments of utility tunnel structures are often based on single heat sources or static temperature field analysis, which fails to accurately reflect the complex heat conduction characteristics under the combined effects of multiple heat sources and lacks dynamic modeling of temperature-stress coupling effects. Existing technologies often employ simplified damage models, assessing only single failure modes such as brittleness or ductility. Furthermore, conventional methods frequently rely on local sampling or empirical thresholds, failing to achieve grid-level refined analysis and making it difficult to accurately locate high-risk areas, thus affecting the timeliness of accident prevention and maintenance decisions.

[0003] The existing technology, disclosed in CN112906239A, uses multi-source information fusion to evaluate the safety status of integrated utility tunnels in mountainous areas. It combines the impact of various risk factors on tunnel engineering safety to obtain a strength safety factor for the integrated utility tunnel. This safety factor is then used to reduce the surrounding rock strength parameters, and the stability of the surrounding rock under different working conditions is calculated based on the obtained strength parameters to evaluate the safety status of the integrated utility tunnel. However, this method does not consider potential fire sources or vulnerable areas of the tunnel structure, does not simulate temperature distribution under the combined action of multiple fire sources, and ignores the coupling effects of multiple mechanisms such as creep damage. Furthermore, it does not use grid construction to accurately locate the risk areas of the tunnel, resulting in an incomplete risk assessment. Therefore, an efficient and reliable method for evaluating the safety status of integrated utility tunnels is urgently needed.

[0004] The information disclosed in the background section is only intended to enhance the understanding of the background of this disclosure, and therefore may include information that does not constitute prior art known to those skilled in the art. Summary of the Invention

[0005] The purpose of this invention is to provide a safety status evaluation method and system for integrated utility tunnels to solve the problems mentioned in the background art.

[0006] To achieve the above objectives, the present invention provides the following technical solution:

[0007] The safety status evaluation method for integrated utility tunnels includes the following specific steps:

[0008] S1: Determine the coordinate system and mark the location coordinates of potential fire sources. Divide the steel structure of the utility tunnel into several three-dimensional grids with a set grid step size, determine the coordinates of all three-dimensional grid nodes, and collect the ambient temperature of the utility tunnel at the same time.

[0009] S2: Set the same heat release intensity condition for each potential fire source at its location coordinates. Based on the simulated temperature of the pipe gallery and the set heat release intensity condition, construct a linear heat conduction model. Use the steady-state heat release method to calculate the simulated temperature of each three-dimensional grid node. Based on the simulated temperatures of adjacent three-dimensional grid nodes, use the finite difference method to calculate the temperature field distribution coefficient of each three-dimensional grid node, and use the arithmetic mean method to obtain the temperature distribution coefficient of the center point of the three-dimensional grid.

[0010] S3: Based on the temperature distribution coefficient at the center point of each three-dimensional mesh, combined with the coupling effect of temperature and stress, the response of each three-dimensional mesh is evaluated in detail for different types of damage behavior. Quantitative indices for brittle damage, ductile damage and creep damage are constructed respectively, and integrated into the local damage tensor of each three-dimensional mesh.

[0011] S4: Based on the local damage tensor, the coupling coefficient matrix at any grid location is constructed using the coupled damage method, and the equivalent damage energy at any grid location is calculated using the inner product method. The equivalent damage energy is then normalized and mapped to the safety coefficient of any grid center point.

[0012] S5: Compare the safety coefficient of any grid center point with the set safety threshold. If it exceeds the safety threshold, the grid location is considered a risk area.

[0013] Furthermore, the utility tunnel is uniformly divided into several three-dimensional grids. The specific steps are as follows:

[0014] The origin of the coordinate system is chosen as the intersection of the cross-section at the entrance of the utility tunnel and the tunnel's axis. This intersection is then extended along the tunnel's axis to establish... The axial direction is perpendicular to the axis of the utility tunnel and points towards the width of the utility tunnel. axial direction, perpendicular to , The axial direction and the height direction of the straight pipe gallery are In the axial direction, with a set grid step size , , The utility tunnel is uniformly divided into grid units in three-dimensional space, and grid nodes that extend beyond the steel structure of the utility tunnel are removed.

[0015] The position of any 3D mesh node is represented as ,in, , , They represent in , , The discrete point index along the direction divides the pipe gallery into discrete three-dimensional mesh units.

[0016] Furthermore, the steady-state heat release method is used to calculate the simulated temperature of each three-dimensional mesh node. The specific steps are as follows:

[0017] No. The coordinates of the potential ignition source locations are: Construct a linear heat conduction model:

[0018] ;

[0019] in,

[0020] ;

[0021] ;

[0022] Indicates the simulated ambient temperature; Indicates the first The maximum heat release rate of a potential ignition source center; Indicates the first The attenuation radius of heat from a potential fire source; Indicates the first The potential ignition sources are numbered as follows in the 3D mesh node: The simulated temperature generated at that location; Indicates thermal conductivity; Represents 3D mesh nodes To the A potential ignition source Euclidean distance; , , They represent the first A potential source of fire , , The coordinate position of the point in the direction; Indicates the first The combustion rate of fuel per unit area of ​​a potential ignition source; Indicates the first The area of ​​a potential ignition source burning; Indicates the first The calorific value of fuel from a potential ignition source; Indicates the first The combustion efficiency coefficient of fuel for each potential ignition source; Indicates the index number of potential fire sources; This represents the total number of potential fire sources.

[0023] Furthermore, the specific steps for obtaining the temperature distribution coefficient at the center point of the three-dimensional mesh using the arithmetic mean method are as follows:

[0024] Based on the simulated temperature of adjacent 3D mesh nodes, the temperature field distribution coefficient of each 3D mesh node is calculated using the finite difference method:

[0025] ;

[0026] ;

[0027] ;

[0028] in, , , They represent , , Gradient of direction; The 3D mesh node number is Number of grid indices on the right side; The 3D mesh node number is Number of grid indices on the left; The 3D mesh node number is Number of grid indices on the front side; The 3D mesh node number is Number of grid indices at the rear; The 3D mesh node number is The number of grid indices above; The 3D mesh node number is The number of grid indices below;

[0029] Calculate the gradient magnitude based on the simulated temperature gradient:

[0030] ;

[0031] in, The 3D mesh node number is Gradient magnitude at the location;

[0032] Calculate the ratio of the local gradient magnitude to the maximum gradient across the entire field to construct the temperature field distribution coefficient:

[0033] ;

[0034] in, The 3D mesh node number is Temperature field distribution coefficient at that location;

[0035] Based on the temperature field distribution coefficients of the three-dimensional mesh nodes, the temperature distribution coefficients at the center points of the three-dimensional mesh are obtained using the arithmetic mean method.

[0036] ;

[0037] Represents the center point of the grid Temperature distribution coefficient at that location; Indicates along Offset of neighboring points along the axial direction. Indicates the left endpoint of the current grid cell. Indicates the left endpoint of the adjacent grid cell on the right; Indicates along Offset of neighboring points along the axial direction. Indicates the rear endpoint of the current mesh cell. Indicates the rear endpoint of the adjacent grid cell in front; Indicates along Offset of neighboring points along the axial direction. Indicates the bottom endpoint of the current mesh cell. Indicates the bottom endpoint of the adjacent grid cell above; The 3D mesh node number is Temperature field distribution coefficient at that location.

[0038] Further, the local damage variables for each 3D mesh are obtained, specifically through the following steps:

[0039] The response of each 3D mesh is evaluated in detail for different types of damage behavior, and quantitative indices for brittle damage, ductile damage, and creep damage are constructed respectively. Among them, the tensile strength method is used to construct the brittle damage coefficient at any mesh location:

[0040] ;

[0041] in, Represents the center point of the grid The brittle damage coefficient at the location; This indicates the critical simulation temperature of the pipe gallery material. This indicates the simulated melting temperature of the pipe gallery material; This indicates the minimum stress that the material can currently withstand; Indicates in The tensile strength below;

[0042] The ductility damage coefficient at the center of an arbitrary mesh is constructed by coupling stress with simulated temperature.

[0043] ;

[0044] in, Represents von Mises stress; Represents the center point of the grid The ductile damage coefficient at the location; Indicates in Yield strength below; This indicates the reference simulation temperature of the pipe gallery material at room temperature; Indicates the stress sensitivity index;

[0045] Creep damage coefficients at arbitrary mesh locations are constructed using the high-temperature creep effect method:

[0046] ;

[0047] in, Represents the center point of the grid The creep damage coefficient at the location; This represents the mean stress in the pipe gallery; This indicates the actual structural thickness of the utility tunnel; Indicates the standard thickness of the utility tunnel;

[0048] Based on the brittle damage coefficient, ductile damage coefficient, and creep damage coefficient at any grid center point, a local damage variable is defined for the center of any grid:

[0049] ;

[0050] in, Represents the center point of the grid Local damage variables at the location.

[0051] Furthermore, the safety coefficient for any grid center point is constructed, and the specific steps are as follows:

[0052] Based on the local damage tensor, a coupling coefficient matrix at any mesh location is constructed using the coupled damage method:

[0053] ;

[0054] in, Represents the center point of the grid The coupling coefficient matrix at the location;

[0055] The equivalent damage energy at any grid location is calculated using the inner product method;

[0056] ;

[0057] in, Represents the center point of the grid Equivalent damage energy; express Device matrix; express The transpose of the matrix;

[0058] The equivalent damage energy is normalized and mapped to a safety factor at any grid location:

[0059] ;

[0060] in, Represents the center point of the grid Safety factor.

[0061] Furthermore, the safety factor of any grid center point is compared with a set safety threshold. If it exceeds the safety threshold, the grid location is considered a risk area. The specific steps are as follows:

[0062] when A value greater than or equal to 0.8 indicates the grid center point. In a safe state; when A value greater than or equal to 0.5 but less than 0.8 indicates the center point of the grid. In a state of alert; when When it is less than 0.5, it indicates the center point of the grid. They are in a high-risk state.

[0063] Furthermore, after clustering is completed, all impurities are divided into multiple different types based on the clustering results. For each type of impurity, the total number of impurities belonging to that type is counted. After the count is completed, the number of each impurity type is compared with the preset threshold. If the threshold is exceeded, an alarm is issued.

[0064] The present invention also provides a safety status evaluation system for integrated utility tunnels, the evaluation system being used to perform the above-described evaluation method, including:

[0065] The data acquisition module is used to determine the coordinate system and mark the location coordinates of potential fire sources. With a set grid step size, it uniformly divides the steel structure of the utility tunnel into several three-dimensional grids, determines the node coordinates of all three-dimensional grids, and collects the ambient temperature of the utility tunnel.

[0066] The temperature distribution coefficient construction module is used to set the same heat release intensity condition for each potential fire source at its location coordinates. Based on the simulated environmental temperature of the pipe gallery and the set heat release intensity condition, a linear heat conduction model is constructed. The steady-state heat release method is used to calculate the simulated temperature of each three-dimensional grid node. Based on the simulated temperatures of adjacent three-dimensional grid nodes, the finite difference method is used to calculate the temperature field distribution coefficient of each three-dimensional grid node, and the arithmetic mean method is used to obtain the temperature distribution coefficient of the center point of the three-dimensional grid.

[0067] The local damage tensor construction module is used to refine the evaluation of the response of each three-dimensional mesh based on the temperature distribution coefficient at the center point of each three-dimensional mesh and the coupling effect of temperature and stress, for different types of damage behavior. It constructs quantitative indicators for brittle damage, ductile damage and creep damage respectively, and integrates them into the local damage tensor of each three-dimensional mesh.

[0068] The safety coefficient construction module is used to construct the coupling coefficient matrix at any mesh location based on the local damage tensor using the coupled damage method, and calculate the equivalent damage energy at any mesh location using the inner product method. The equivalent damage energy is then normalized and mapped to the safety coefficient of any mesh center point.

[0069] The evaluation module compares the safety coefficient of any grid center point with a set safety threshold. If the safety threshold is exceeded, the grid location is considered a risk area.

[0070] Compared with the prior art, the beneficial effects of the present invention are:

[0071] By utilizing the steady-state heat release method and the finite difference method, the temperature distribution under the combined action of multiple heat sources can be efficiently simulated, overcoming the limitations of traditional single heat source models. Based on the construction of local damage tensors of temperature-stress coupling, the quantification of multiple indicators of brittle, ductile, and creep damage is integrated, realizing the comprehensive evaluation of multiple failure modes. By generating grid-level safety coefficients through normalized mapping, the identification of risk areas becomes more intuitive. By combining temperature field modeling of multiple heat sources with three-dimensional grid-level damage quantification, the safety assessment accuracy of pipe gallery structures under complex thermal environments is significantly improved. Attached Figure Description

[0072] Figure 1 is a schematic diagram of the overall method flow of the present invention.

[0073] Figure 2 shows the relationship between the safety factor at any grid center point and the equivalent damage energy.

[0074] Figure 3 is a schematic diagram of the overall system of the present invention. Detailed Implementation

[0075] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to specific embodiments.

[0076] It should be noted that, unless otherwise defined, the technical or scientific terms used in this invention should have the ordinary meaning understood by one of ordinary skill in the art to which this invention pertains. The terms "first," "second," and similar terms used in this invention do not indicate any order, quantity, or importance, but are merely used to distinguish different components. Terms such as "comprising" or "including" mean that the element or object preceding the word encompasses the elements or objects listed following the word and their equivalents, without excluding other elements or objects. Terms such as "connected" or "linked" are not limited to physical or mechanical connections, but can include electrical connections, whether direct or indirect. Terms such as "upper," "lower," "left," and "right" are used only to indicate relative positional relationships; when the absolute position of the described object changes, the relative positional relationship may also change accordingly.

[0077] Example:

[0078] Please refer to Figures 1 and 2. This invention provides a technical solution:

[0079] The safety status evaluation method for integrated utility tunnels includes the following specific steps:

[0080] S1: Determine the coordinate system and mark the location coordinates of potential fire sources. Divide the steel structure of the utility tunnel into several three-dimensional grids with a set grid step size, determine the coordinates of all three-dimensional grid nodes, and collect the ambient temperature of the utility tunnel at the same time.

[0081] The specific steps for uniformly dividing the pipe gallery into several three-dimensional grids are as follows:

[0082] The origin of the coordinate system is chosen as the intersection of the cross-section at the entrance of the utility tunnel and the tunnel's axis. This intersection is then extended along the tunnel's axis to establish... The axial direction is perpendicular to the axis of the utility tunnel and points towards the width of the utility tunnel. axial direction, perpendicular to , The axial direction and the height direction of the straight pipe gallery are In the axial direction, with a set grid step size , , The utility tunnel is uniformly divided into grid units in three-dimensional space, and grid nodes that extend beyond the steel structure of the utility tunnel are removed.

[0083] The position of any 3D mesh node is represented as ,in, , , They represent in , , The discrete point index along the direction divides the pipe gallery into discrete three-dimensional mesh units.

[0084] S2: Set the same heat release intensity condition for each potential fire source at its location coordinates. Based on the simulated temperature of the pipe gallery and the set heat release intensity condition, construct a linear heat conduction model. Use the steady-state heat release method to calculate the simulated temperature of each three-dimensional grid node. Based on the simulated temperatures of adjacent three-dimensional grid nodes, use the finite difference method to calculate the temperature field distribution coefficient of each three-dimensional grid node, and use the arithmetic mean method to obtain the temperature distribution coefficient of the center point of the three-dimensional grid.

[0085] The method of calculating the simulated temperature of each three-dimensional mesh node using steady-state heat release involves the following steps:

[0086] No. The coordinates of the potential ignition source locations are: Construct a linear heat conduction model:

[0087] ;

[0088] in,

[0089] ;

[0090] ;

[0091] Indicates the simulated ambient temperature; Indicates the first The maximum heat release rate of a potential ignition source center; Indicates the first The attenuation radius of heat from a potential fire source; Indicates the first The potential ignition sources are numbered as follows in the 3D mesh node: The simulated temperature generated at that location; Indicates thermal conductivity; Represents 3D mesh nodes To the A potential ignition source Euclidean distance; , , They represent the first A potential source of fire , , The coordinate position of the point in the direction; Indicates the first The combustion rate of fuel per unit area of ​​a potential ignition source; Indicates the first The area of ​​a potential ignition source burning; Indicates the first The calorific value of fuel from a potential ignition source; Indicates the first The combustion efficiency coefficient of fuel for each potential ignition source; Indicates the index number of potential fire sources; This represents the total number of potential fire sources.

[0092] formula In solving the problem, the dependent variable Indicates the first The potential ignition sources are numbered as follows in the 3D mesh node: The simulated temperature generated at that location is quantified by the formula using an exponential decay term to quantify the energy diffusion of the heat source with distance, and combined with the ambient temperature. This reflects the combined effect of multiple heat sources on local temperature; when the heat source is considered a point source, the steady-state temperature field decays exponentially with distance, and this exponential term directly originates from the heat conduction equation. The scale of the controlled thermal influence range; the coordinates of the heat source determine the relative distance between the heat source and the grid nodes. This directly affects the temperature decay rate, as the distance between the grid node and the fire source... As the temperature increases, the temperature decreases exponentially due to the term. Rapidly decreases thermal conductivity Increasing this will accelerate energy dissipation and weaken the local temperature rise effect. Combustion efficiency coefficient When the temperature increases, the simulated temperature Significantly improved; diffusion radius When the range is expanded, the thermal influence range is extended; the temperature contribution of multiple fire sources to the same grid node is reflected by the superposition summation term, which conforms to the superposition principle of linear systems.

[0093] formula In the solution, The physical meaning is the effective heat released by the fire source through combustion per unit time. By quantifying the actual energy output of the fire source, it provides accurate input for temperature field calculation and significantly improves the reliability of fire spread simulation. The rate of fuel mass consumption per unit area directly affects the time-varying characteristics of the heat release rate. Characterizes the spatial extent of the fire source; as the area increases, the proportion of total fuel participating in combustion increases linearly. It reflects the inherent chemical energy of fuel; the higher the calorific value, the greater the energy released per unit mass of fuel during combustion. Characterizing the ratio of actual combustion heat to the theoretical maximum, correcting for heat loss due to incomplete combustion or heat dissipation; all independent variables , , , All with They are directly proportional; as any parameter increases, the heat release intensity increases synchronously.

[0094] The specific steps for obtaining the temperature distribution coefficient at the center point of the three-dimensional mesh using the arithmetic mean method are as follows:

[0095] Based on the simulated temperature of adjacent 3D mesh nodes, the temperature field distribution coefficient of each 3D mesh node is calculated using the finite difference method:

[0096] ;

[0097] ;

[0098] ;

[0099] in, , , They represent , , Gradient of direction; The 3D mesh node number is Number of grid indices on the right side; The 3D mesh node number is Number of grid indices on the left; The 3D mesh node number is Number of grid indices on the front side; The 3D mesh node number is Number of grid indices at the rear; The 3D mesh node number is The number of grid indices above; The 3D mesh node number is The number of grid indices below;

[0100] In the above formula, the temperature difference between adjacent nodes reflects the trend of spatial temperature change. The larger the difference, the more significant the gradient, which directly drives the characterization of the non-uniformity of the temperature field distribution. , , Define the spatial discretization scale; the smaller the spacing, the denser the grid, and the higher the local resolution of gradient calculation. The superposition of the temperature contributions from multiple heat sources affects the sum of the temperatures of adjacent nodes, thereby regulating the gradient magnitude.

[0101] Calculate the gradient magnitude based on the simulated temperature gradient:

[0102] ;

[0103] in, The 3D mesh node number is Gradient magnitude at the location;

[0104] Calculate the ratio of the local gradient magnitude to the maximum gradient across the entire field to construct the temperature field distribution coefficient:

[0105] ;

[0106] in, The 3D mesh node number is Temperature field distribution coefficient at that location;

[0107] In the above formula, The physical meaning is the ratio of the current node's temperature gradient magnitude to the global maximum gradient magnitude, mapping the gradient intensity to the normalized interval. In this process, a quantitative comparison of heat flux intensity distribution under different scenarios is achieved; The magnitude of the gradient modulus directly determines the value of the molecule, reflecting the degree of drastic local temperature change at that node. The larger the gradient modulus, the greater the magnitude of the gradient. The closer it is to 1; As the normalization benchmark of the denominator increases, the values ​​of all nodes... Reduce proportionally to ensure the result remains dimensionless; and They exhibit a linear proportional relationship, with the ratio increasing significantly as the modulus length increases. and They exhibit an inverse proportional relationship; as the maximum value increases, the normalization results of all nodes are compressed.

[0108] Based on the temperature field distribution coefficients of the three-dimensional mesh nodes, the temperature distribution coefficients at the center points of the three-dimensional mesh are obtained using the arithmetic mean method.

[0109] ;

[0110] Represents the center point of the grid Temperature distribution coefficient at that location; Indicates along Offset of neighboring points along the axial direction. Indicates the left endpoint of the current grid cell. Indicates the left endpoint of the adjacent grid cell on the right; Indicates along Offset of neighboring points along the axial direction. Indicates the rear endpoint of the current mesh cell. Indicates the rear endpoint of the adjacent grid cell in front; Indicates along Offset of neighboring points along the axial direction. Indicates the bottom endpoint of the current mesh cell. Indicates the bottom endpoint of the adjacent grid cell above; The 3D mesh node number is Temperature field distribution coefficient at that location.

[0111] In the above formula, Grid center point The temperature distribution coefficient at a given location is physically the arithmetic mean of the temperature distribution coefficients of the surrounding eight grid nodes, achieving a smooth transition from discrete nodes to continuous spatial representation of the three-dimensional temperature distribution coefficient. The center point coefficient is the average of the coefficients of the surrounding eight grid nodes, including the current cell endpoint and the endpoints of adjacent cells, with each node having a contribution weight of 1. This reflects the spatial continuity of the local temperature distribution; offset parameter , , Traverse the three-dimensional neighborhood, ensuring that the endpoints of the current grid cell and its directly adjacent cells are all included in the calculation range, covering all spatially associated thermodynamic feature nodes; the coefficient of any adjacent node... When it increases, The weight increases proportionally, i.e., 1 / 8, and the overall relationship is linearly superimposed.

[0112] S3: Based on the temperature distribution coefficient at the center point of each three-dimensional mesh, combined with the coupling effect of temperature and stress, the response of each three-dimensional mesh is evaluated in detail for different types of damage behavior. Quantitative indices for brittle damage, ductile damage and creep damage are constructed respectively, and integrated into the local damage tensor of each three-dimensional mesh.

[0113] The specific steps to obtain the local damage variables for each 3D mesh are as follows:

[0114] The response of each 3D mesh is evaluated in detail for different types of damage behavior, and quantitative indices for brittle damage, ductile damage, and creep damage are constructed respectively. Among them, the tensile strength method is used to construct the brittle damage coefficient at any mesh location:

[0115] ;

[0116] in, Represents the center point of the grid The brittle damage coefficient at the location; This indicates the critical simulation temperature of the pipe gallery material. This indicates the simulated melting temperature of the pipe gallery material; This indicates the minimum stress that the material can currently withstand; Indicates in The tensile strength below;

[0117] In the above formula, the dependent variable Grid center point The brittle damage coefficient at the stress point is physically represented as a normalized damage probability based on the temperature distribution coefficient and stress state. Reflecting the thermal load intensity at the current grid center point, the closer the temperature is to the melting threshold... The probability of brittle damage increases nonlinearly. Define the range of thermal damage thresholds for materials to form a normalized benchmark for damage ratios; Characterizes material strength and load state, and measures the contribution of external loads to strength degradation; dependent variable along with The increase in , following a quadratic function, rapidly reflects the exponential deterioration of brittle damage near the melting temperature. The quadratic amplification of the damage contribution in the high-temperature region is more consistent with the abrupt changes in the characteristics of brittle fracture. When it decreases, Significant increase; critical simulation temperature As the temperature rises, the normalized temperature difference term decreases. Decrease; when When the coefficient is close to 1, the material is near its load-bearing limit, and the brittle damage coefficient is low. Suppressed, conversely, low stress state much smaller At this time, temperature-dominated damage is allowed, amplifying the brittle damage coefficient. .

[0118] The ductility damage coefficient at the center of an arbitrary mesh is constructed by coupling stress with simulated temperature.

[0119] ;

[0120] in, Represents von Mises stress; Represents the center point of the grid The ductile damage coefficient at the location; Indicates in Yield strength below; This indicates the reference simulation temperature of the pipe gallery material at room temperature; Indicates the stress sensitivity index;

[0121] In the above formula, Represents the center point of the grid The ductile damage coefficient at a given location, by coupling the von Mises stress criterion with temperature-driven material softening properties, dynamically characterizes the ductile damage process in local areas of the pipe gallery. The multiaxial stress state of the grid points is characterized by its larger value, which indicates that the material undergoes more significant equivalent plastic deformation and directly drives the accumulation of ductile damage. Reflects the local temperature of the material The resistance to plastic deformation decreases with increasing temperature. A decrease accelerates damage growth; Quantify the degree to which the local temperature deviates from the ambient temperature reference; an increase in temperature indicates... The damage contribution of stress terms is indirectly amplified by material softening; stress sensitivity index Controlling the nonlinear amplification effect of stress-to-damage ratio The yield strength exhibits a superlinear response characteristic of plastic deformation rate with increasing stress; as the exponent increases, the damage coefficient under the same stress ratio increases power-law. Reduce the softening of materials caused by high temperatures. The ratio increases, Significant increase.

[0122] Creep damage coefficients at arbitrary mesh locations are constructed using the high-temperature creep effect method:

[0123] ;

[0124] in, Represents the center point of the grid The creep damage coefficient at the location; This represents the mean stress in the pipe gallery; This indicates the actual structural thickness of the utility tunnel; Indicates the standard thickness of the utility tunnel;

[0125] In the above formula, the dependent variable Represents the center point of the grid The creep damage coefficient at the location is used to dynamically assess the creep damage accumulation rate of the pipe gallery in the service environment by integrating temperature-driven high-temperature creep effect, thickness-related structural stability, and the threshold response of mean stress to material flow. This indicates that atomic diffusion is accelerated under high temperature conditions, the material creep rate increases significantly, and the nonlinear damage contribution in the high temperature region is amplified to the fourth power. The ratio of actual thickness to standard thickness reflects the structure's local creep resistance. Reduced thickness weakens the load-bearing section and exacerbates damage. When it increases, Reduce and inhibit damage accumulation; Characterizing the internal driving force of a material using the hyperbolic tangent function To constrain the saturation effect of damage growth and avoid excessive stress leading to non-physical damage values, thus obtaining the mean stress. The impact of damage It tends to saturate after yielding, avoiding unlimited growth, which conforms to the plastic flow characteristics of materials after yielding; when close to At that time, the damage coefficient increased to the fourth power, reflecting the accelerating effect of high temperature on creep; When it increases, As the value approaches 1, the damage coefficient increases significantly.

[0126] Based on the brittle damage coefficient, ductile damage coefficient, and creep damage coefficient at any grid center point, a local damage variable is defined for the center of any grid:

[0127] ;

[0128] in, Represents the center point of the grid Local damage variables at the location.

[0129] S4: Based on the local damage tensor, the coupling coefficient matrix at any grid location is constructed using the coupled damage method, and the equivalent damage energy at any grid location is calculated using the inner product method. The equivalent damage energy is then normalized and mapped to the safety coefficient of any grid center point.

[0130] The specific steps for constructing the safety factor of any grid center point are as follows:

[0131] Based on the local damage tensor, a coupling coefficient matrix at any mesh location is constructed using the coupled damage method:

[0132] ;

[0133] in, Represents the center point of the grid The coupling coefficient matrix at the location;

[0134] In the above formula, the nonlinear coupling effect between different damage mechanisms is reflected by the off-diagonal elements of the matrix, such as the promoting effect of brittle microcracks on ductile and plastic flow, and the threshold regulation of creep damage on brittle fracture. This represents the gain effect of ductile damage on brittle damage, with the coefficient 0.7 and the square root term reflecting its nonlinear weak gain characteristics. This indicates the threshold regulation of creep damage on brittle damage. Reducing material continuity linearly amplifies the risk of brittle cracking; a coefficient of 0.3 reflects a low coupling weight. This indicates the interference effect of brittle damage on ductile damage; a linear coefficient of 0.5 indicates a moderate effect on ductile damage. This indicates the passivation effect of creep damage on ductile damage, with 0.8 reflecting its damage saturation trend; This indicates the aggravating effect of brittle damage on creep damage, with the superlinear power of 1.5 highlighting its dramatic promoting effect on creep damage. This indicates the synergistic enhancement of creep damage by ductile damage, with a linear coefficient of 0.6 indicating that it significantly accelerates the high-temperature creep rate; the main diagonal element is fixed at 1 to ensure that the energy contribution of a single damage is independent of the coupling effect.

[0135] The equivalent damage energy at any grid location is calculated using the inner product method;

[0136] ;

[0137] in, Represents the center point of the grid Equivalent damage energy; express Device matrix; express The transpose of the matrix;

[0138] In the above formula, The physical meaning is a comprehensive energy characterization of multiple damage modes, such as brittleness, ductility, and creep, after nonlinear coupling; it aggregates the synergistic effect of multiple damages through inner product operations, quantifying the local energy accumulation state of the material. A symmetric positive definite matrix is ​​constructed to cover all possible paths of multi-damage interaction, eliminating energy calculation bias caused by asymmetric coupling. The square root operation converts the inner product result into a scalar energy value, which is consistent with the energy release rate form in classical fracture mechanics. Each component directly determines the energy amplitude; the greater the damage value, the more significant the energy accumulation. The inner product form captures the anisotropic characteristics of multi-damage coupling through tensor multiplication; any damage component is... , , The increase of all can lead to The rise reflects the driving force of damage accumulation on energy growth; matrix The larger the coefficient of the diagonal elements in the non-central region, the stronger the contribution of a specific damage combination to energy.

[0139] The equivalent damage energy is normalized and mapped to a safety factor at any grid location:

[0140] ;

[0141] in, Represents the center point of the grid Safety factor.

[0142] In the above formula, the damage energy is represented by a normalized mapping. It is integrated with the maximum single damage value to form a dimensionless safety index, which directly quantifies the risk of local failure. This is used to characterize the most severe independent damage mode in the current mesh; the larger the value, the better. The smaller; Used to adjust the contribution weight of extreme damage to the safety factor. The higher the value, the more significant the reduction effect of extreme damage on safety; This converts energy values ​​into scalar damage intensity, demonstrating the continuous weakening of safety due to the synergistic effect of multiple damages. The higher the energy value, The smaller the value; avoid zero damage when the "1" in the denominator is less significant. The formula diverges, and the whole formula is in the form of a hyperbolic function, which conforms to the law of gradual decay of safety as damage increases; At that time, the impact of extreme damage on safety outweighs the multi-damage coupling effect.

[0143] In the above embodiments, 10 sets of data on the equivalent damage energy and safety factor at any grid center point are given to reflect the change of the safety factor with the equivalent damage energy, as shown in Table 1:

[0144] Table 1: Relationship between equivalent damage energy and safety factor

[0145]

[0146] As can be seen from Table 1 above, given The value is 0.1. As the equivalent damage energy at the center point of the grid increases, its corresponding safety factor gradually decreases, which is consistent with... The higher the energy value, The smaller the change.

[0147] S5: Compare the safety coefficient of any grid center point with the set safety threshold. If it exceeds the safety threshold, the grid location is considered a risk area.

[0148] The step involves comparing the safety coefficient of any grid center point with a set safety threshold. If the safety threshold is exceeded, the grid location is considered a risk area. The specific steps are as follows:

[0149] when A value greater than or equal to 0.8 indicates the grid center point. In a safe state; when A value greater than or equal to 0.5 but less than 0.8 indicates the center point of the grid. In a state of alert; when When it is less than 0.5, it indicates the center point of the grid. They are in a high-risk state.

[0150] Please refer to Figure 3. The present invention also provides a safety status evaluation system for integrated utility tunnels. This evaluation system is used to perform the above-described evaluation method and includes:

[0151] The data acquisition module is used to determine the coordinate system and mark the location coordinates of potential fire sources. With a set grid step size, it uniformly divides the steel structure of the utility tunnel into several three-dimensional grids, determines the node coordinates of all three-dimensional grids, and collects the ambient temperature of the utility tunnel.

[0152] The temperature distribution coefficient construction module is used to set the same heat release intensity condition for each potential fire source at its location coordinates. Based on the simulated environmental temperature of the pipe gallery and the set heat release intensity condition, a linear heat conduction model is constructed. The steady-state heat release method is used to calculate the simulated temperature of each three-dimensional grid node. Based on the simulated temperatures of adjacent three-dimensional grid nodes, the finite difference method is used to calculate the temperature field distribution coefficient of each three-dimensional grid node, and the arithmetic mean method is used to obtain the temperature distribution coefficient of the center point of the three-dimensional grid.

[0153] The local damage tensor construction module is used to refine the evaluation of the response of each three-dimensional mesh based on the temperature distribution coefficient at the center point of each three-dimensional mesh and the coupling effect of temperature and stress, for different types of damage behavior. It constructs quantitative indicators for brittle damage, ductile damage and creep damage respectively, and integrates them into the local damage tensor of each three-dimensional mesh.

[0154] The safety coefficient construction module is used to construct the coupling coefficient matrix at any mesh location based on the local damage tensor using the coupled damage method, and calculate the equivalent damage energy at any mesh location using the inner product method. The equivalent damage energy is then normalized and mapped to the safety coefficient of any mesh center point.

[0155] The evaluation module compares the safety coefficient of any grid center point with a set safety threshold. If the safety threshold is exceeded, the grid location is considered a risk area.

[0156] The above formulas are all dimensionless calculations. The formulas are derived from software simulations based on a large amount of collected data to obtain the most recent real-world results. The preset parameters in the formulas are set by those skilled in the art according to the actual situation.

[0157] The above embodiments can be implemented, in whole or in part, by software, hardware, firmware, or any other combination thereof. When implemented in software, the above embodiments can be implemented, in whole or in part, as a computer program product. Those skilled in the art will recognize that the units and algorithm steps of the various examples described in conjunction with the embodiments disclosed herein can be implemented by electronic hardware, or a combination of computer software and electronic hardware. Whether these functions are implemented in hardware or software depends on the specific application and design constraints of the technical solution.

[0158] The units described as separate components may or may not be physically separate. The components shown as units may or may not be physical units; they may be located in one place or distributed across multiple network units. Some or all of the units can be selected to achieve the purpose of this embodiment, depending on actual needs.

[0159] The above description is merely a specific embodiment of this application, but the scope of protection of this application is not limited thereto. Any changes or substitutions that can be easily conceived by those skilled in the art within the scope of the technology disclosed in this application should be included within the scope of protection of this application.

Claims

1. A method for evaluating a safety state of a utility tunnel, characterized by the steps of include: S1: Determine the coordinate system and mark the location coordinates of potential fire sources. Divide the steel structure of the utility tunnel into several three-dimensional grids with a set grid step size, determine the coordinates of all three-dimensional grid nodes, and collect the ambient temperature of the utility tunnel at the same time. S2: Set the same heat release intensity condition for each potential fire source at its location coordinates. Based on the simulated temperature of the pipe gallery and the set heat release intensity condition, construct a linear heat conduction model. Use the steady-state heat release method to calculate the simulated temperature of each three-dimensional grid node. Based on the simulated temperatures of adjacent three-dimensional grid nodes, use the finite difference method to calculate the temperature field distribution coefficient of each three-dimensional grid node, and use the arithmetic mean method to obtain the temperature distribution coefficient of the center point of the three-dimensional grid. S3: Based on the temperature distribution coefficient at the center point of each three-dimensional mesh, combined with the coupling effect of temperature and stress, the response of each three-dimensional mesh is evaluated in detail for different types of damage behavior. Quantitative indices for brittle damage, ductile damage and creep damage are constructed respectively, and integrated into the local damage tensor of each three-dimensional mesh. S4: Based on the local damage tensor, the coupling coefficient matrix at any grid location is constructed using the coupled damage method, and the equivalent damage energy at any grid location is calculated using the inner product method. The equivalent damage energy is then normalized and mapped to the safety coefficient of any grid center point. S5: Compare the safety coefficient of any grid center point with the set safety threshold. If it exceeds the safety threshold, the grid location is considered a risk area.

2. The safety status evaluation method for integrated utility tunnels according to claim 1, characterized in that, The specific steps for uniformly dividing the pipe gallery into several three-dimensional grids are as follows: The origin of the coordinate system is chosen as the intersection of the cross-section at the entrance of the utility tunnel and the tunnel's axis. This intersection is then extended along the tunnel's axis to establish... The axial direction is perpendicular to the axis of the utility tunnel and points towards the width of the utility tunnel. axial direction, perpendicular to 、 The axial direction and the height direction of the straight pipe gallery are In the axial direction, with a set grid step size 、 、 The utility tunnel is uniformly divided into grid units in three-dimensional space, and grid nodes that extend beyond the steel structure of the utility tunnel are removed. The position of any 3D mesh node is represented as ,in, 、 、 They represent in 、 、 The discrete point index along the direction divides the pipe gallery into discrete three-dimensional mesh units.

3. The safety status evaluation method for integrated utility tunnels according to claim 2, characterized in that, The method of calculating the simulated temperature of each three-dimensional mesh node using steady-state heat release involves the following steps: The The coordinates of the potential ignition source locations are: Construct a linear heat conduction model: ； in, ； ； Indicates the simulated ambient temperature; Indicates the first The maximum heat release rate of a potential ignition source center; Indicates the first The attenuation radius of heat from a potential fire source; Indicates the first The potential ignition sources are numbered as follows in the 3D mesh node: The simulated temperature generated at that location; Indicates thermal conductivity; Represents 3D mesh nodes To the A potential ignition source Euclidean distance; 、 、 They represent the first A potential source of fire 、 、 The coordinate position of the point in the direction; Indicates the first The combustion rate of fuel per unit area of ​​a potential ignition source; Indicates the first The area of ​​a potential ignition source burning; Indicates the first The calorific value of fuel from a potential ignition source; Indicates the first The combustion efficiency coefficient of fuel for each potential ignition source; Indicates the index number of potential fire sources; This represents the total number of potential fire sources.

4. The safety status evaluation method for integrated utility tunnels according to claim 2, characterized in that, The specific steps for obtaining the temperature distribution coefficient at the center point of the three-dimensional mesh using the arithmetic mean method are as follows: Based on the simulated temperature of adjacent 3D mesh nodes, the temperature field distribution coefficient of each 3D mesh node is calculated using the finite difference method: ； ； ； in, 、 、 They represent 、 、 Gradient of direction; The 3D mesh node number is Number of grid indices on the right side; The 3D mesh node number is Number of grid indices on the left; The 3D mesh node number is Number of grid indices on the front side; The 3D mesh node number is Number of grid indices at the rear; The 3D mesh node number is The number of grid indices above; The 3D mesh node number is The number of grid indices below; Calculate the gradient magnitude based on the simulated temperature gradient: ； in, The 3D mesh node number is Gradient magnitude at the location; Calculate the ratio of the local gradient magnitude to the maximum gradient across the entire field to construct the temperature field distribution coefficient: ； in, The 3D mesh node number is Temperature field distribution coefficient at that location; Based on the temperature field distribution coefficients of the three-dimensional mesh nodes, the temperature distribution coefficients at the center points of the three-dimensional mesh are obtained using the arithmetic mean method. ； Represents the center point of the grid Temperature distribution coefficient at that location; Indicates along Offset of neighboring points along the axial direction. Indicates the left endpoint of the current grid cell. Indicates the left endpoint of the adjacent grid cell on the right; Indicates along Offset of neighboring points along the axial direction. Indicates the rear endpoint of the current mesh cell. Indicates the rear endpoint of the adjacent grid cell in front; Indicates along Offset of neighboring points along the axial direction. Indicates the bottom endpoint of the current mesh cell. Indicates the bottom endpoint of the adjacent grid cell above; The 3D mesh node number is Temperature field distribution coefficient at that location.

5. The safety status evaluation method for integrated utility tunnels according to claim 1, characterized in that, The specific steps to obtain the local damage variables for each 3D mesh are as follows: The response of each 3D mesh is evaluated in detail for different types of damage behavior, and quantitative indices for brittle damage, ductile damage, and creep damage are constructed respectively. Among them, the tensile strength method is used to construct the brittle damage coefficient at any mesh location: ； in, Represents the center point of the grid The brittle damage coefficient at the location; This indicates the critical simulation temperature of the pipe gallery material. This indicates the simulated melting temperature of the pipe gallery material; This indicates the minimum stress that the material can currently withstand; Indicates in The tensile strength below; The ductility damage coefficient at the center of an arbitrary mesh is constructed by coupling stress with simulated temperature. ； in, Represents von Mises stress; Represents the center point of the grid The ductile damage coefficient at the location; Indicates in Yield strength below; This indicates the reference simulation temperature of the pipe gallery material at room temperature; Indicates the stress sensitivity index; Creep damage coefficients at arbitrary mesh locations are constructed using the high-temperature creep effect method: ； in, Represents the center point of the grid The creep damage coefficient at the location; This represents the mean stress in the pipe gallery; This indicates the actual structural thickness of the utility tunnel; Indicates the standard thickness of the utility tunnel; Based on the brittle damage coefficient, ductile damage coefficient, and creep damage coefficient at any grid center point, a local damage variable is defined for the center of any grid: ； in, Represents the center point of the grid Local damage variables at the location.

6. The safety status evaluation method for integrated utility tunnels according to claim 1, characterized in that, The specific steps for constructing the safety factor of any grid center point are as follows: Based on the local damage tensor, a coupling coefficient matrix at any mesh location is constructed using the coupled damage method: ； in, Represents the center point of the grid The coupling coefficient matrix at the location; The equivalent damage energy at any grid location is calculated using the inner product method; ； in, Represents the center point of the grid Equivalent damage energy; express Device matrix; express The transpose of the matrix; The equivalent damage energy is normalized and mapped to a safety factor at any grid location: ； in, Represents the center point of the grid Safety factor.

7. The safety status evaluation method for integrated utility tunnels according to claim 8, characterized in that, The step involves comparing the safety coefficient of any grid center point with a set safety threshold. If the safety threshold is exceeded, the grid location is considered a risk area. The specific steps are as follows: when A value greater than or equal to 0.8 indicates the grid center point. In a safe state; when A value greater than or equal to 0.5 but less than 0.8 indicates the center point of the grid. In a state of alert; when When it is less than 0.5, it indicates the center point of the grid. They are in a high-risk state.

8. A safety status evaluation system for integrated utility tunnels, characterized in that: The evaluation system is used to perform the evaluation method according to any one of claims 1-7, including: The data acquisition module is used to determine the coordinate system and mark the location coordinates of potential fire sources. With a set grid step size, it uniformly divides the steel structure of the utility tunnel into several three-dimensional grids, determines the node coordinates of all three-dimensional grids, and collects the ambient temperature of the utility tunnel. The temperature distribution coefficient construction module is used to set the same heat release intensity condition for each potential fire source at its location coordinates. Based on the simulated environmental temperature of the pipe gallery and the set heat release intensity condition, a linear heat conduction model is constructed. The steady-state heat release method is used to calculate the simulated temperature of each three-dimensional grid node. Based on the simulated temperatures of adjacent three-dimensional grid nodes, the finite difference method is used to calculate the temperature field distribution coefficient of each three-dimensional grid node, and the arithmetic mean method is used to obtain the temperature distribution coefficient of the center point of the three-dimensional grid. The local damage tensor construction module is used to refine the evaluation of the response of each three-dimensional mesh based on the temperature distribution coefficient at the center point of each three-dimensional mesh and the coupling effect of temperature and stress, for different types of damage behavior. It constructs quantitative indicators for brittle damage, ductile damage and creep damage respectively, and integrates them into the local damage tensor of each three-dimensional mesh. The safety coefficient construction module is used to construct the coupling coefficient matrix at any mesh location based on the local damage tensor using the coupled damage method, and calculate the equivalent damage energy at any mesh location using the inner product method. The equivalent damage energy is then normalized and mapped to the safety coefficient of any mesh center point. The evaluation module compares the safety coefficient of any grid center point with a set safety threshold. If the safety threshold is exceeded, the grid location is considered a risk area.

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