A method for evaluating the hazard of subway tunnel explosion accidents based on generalized interpolation material point method

Abstract

The present invention provides a method for evaluating the hazard of explosion accidents in subway tunnels based on the generalized interpolation material point method. The method uses the generalized interpolation material point method to perform explicit dynamic solutions on the three-dimensional model of the subway tunnel structure and the surrounding rock and soil under the action of explosion. Finally, the model response under the action of explosion is quantitatively calculated, and the partition of personnel injury level and structural damage level is obtained according to the overpressure calculation results and the damage factor calculation results, so as to quantitatively evaluate the hazard of the explosion accident. This method makes up for the defects of previous empirical qualitative evaluation, overcomes the numerical difficulties of traditional finite element simulation methods caused by grid distortion during explosion simulation, and proposes a set of practical and feasible quantitative hazard evaluation methods, which has certain practical application value, will have a positive role in promoting the formulation of special emergency plans, and has guiding significance for post-disaster repair and later recovery work.

Description

Technical Field

[0001] The invention relates to the technical field of hazard assessment, and in particular to a method for assessing the hazard of a subway tunnel explosion accident based on a generalized interpolation material point method. Background Art

[0002] The development of underground space and the construction of subway tunnels are one of the basic tasks in modern urban development and construction. The development of subway tunnels can effectively alleviate problems such as environmental protection and traffic congestion in large cities.

[0003] However, subway tunnels have the characteristics of dense pipelines, closed space, and high population density. Once an explosion or other safety accident occurs, it will cause great harm to personnel safety and social order. At present, my country has not yet established a complete emergency response plan for subway tunnel explosion disasters. The formulation of emergency plans is mostly based on foreign experience, mainly starting with management measures such as strengthening safety inspections, explosives inspections, and accelerating anti-terrorism emergency response speed.

[0004] When an explosion occurs, the response rules of subway tunnels are very complex due to their different structures. It is difficult to qualitatively measure the damage of the explosion to the structural facilities and internal personnel based on experience alone. However, existing mathematical theories or numerical methods cannot provide a good solution to the complex problem of explosions with ultra-high speed and large deformation.

[0005] Therefore, establishing a method suitable for hazard assessment of subway tunnel explosion accidents will play a positive role in promoting the formulation of special emergency plans, and will also provide guidance for post-disaster repair and subsequent recovery work. Summary of the invention

[0006] The purpose of the present invention is to provide a method for evaluating the hazard of explosion accidents in subway tunnels based on a generalized interpolation material point method, so as to solve the problems existing in the prior art.

[0007] The technical solution adopted to achieve the purpose of the present invention is as follows: a method for evaluating the hazard of explosion accidents in subway tunnels based on a generalized interpolation material point method, comprising the following steps:

[0008] 1) Construct an engineering physics model based on the engineering structural characteristics. The engineering physics model includes the structural model of the subway tunnel and the geological model of the surrounding rock and soil. Discretize the continuum of the engineering physics model into N p Material points are generated, and corresponding material parameters are assigned to each material point. A uniform structured grid is used to cover the entire computational domain to generate a background grid.

[0009] 2) Given the initial conditions, boundary conditions and load conditions of the engineering physics model, set the time step for each calculation.

[0010] 3) Set the detonation point location according to the actual situation and calculate the explosive equivalent based on the type and volume of explosives.

[0011] 4) Use the material point method to solve the explosion response.

[0012] 5) Draw an overpressure distribution cloud map based on the explosion response; draw a personnel injury level zoning map in accordance with the personnel injury level classification standards.

[0013] 6) Draw a damage factor cloud map based on the explosion response. Draw a structural damage level zoning map based on the structural damage level classification standard.

[0014] 7) Conduct a comprehensive explosion accident hazard assessment based on the personnel injury level zoning diagram and the structure damage level zoning diagram.

[0015] Further, in step 4), the calculation process of the explosion response of a single time step is: map the material point information and external force to the background grid nodes. Use the generalized interpolation material point method with contact algorithm to display the integral solution of the model. After the calculation is completed, output the overpressure value and wavefront distribution of each air material point, output the stress value, displacement value and plastic strain value of each concrete material point, and output the stress value, displacement value and plastic strain value of each rock and soil material point. Remap the calculation results on each material point to the background grid nodes. Use the interpolation algorithm on the node to obtain the distribution cloud map of each calculation result. Determine whether the calculation has reached the end time. If not, proceed to the next time step. If so, end.

[0016] Furthermore, in step 4), the HJC concrete model is used for the subway tunnel structure. The steel bars inside the concrete structure are discretized into rod units using the hybrid material point method. The rod unit nodes move together with the concrete material points. The constitutive model of the rod unit nodes adopts the ideal elastic-plastic model.

[0017] Furthermore, after step 7), there are also related steps of changing different explosive equivalents, explosion point locations, structural forms and material parameters, repeating the steps, and analyzing the changing laws of the danger of explosion accidents in different scenarios according to different simulation results.

[0018] The technical effects of the present invention are unquestionable:

[0019] A. The generalized interpolation material point simulation method overcomes the numerical difficulties caused by mesh distortion in traditional finite element simulation methods for explosion simulation, and can better solve ultra-high-speed and large deformation problems such as explosions;

[0020] B. The HJC model is used to better solve the impact problem of concrete structures under explosion, and the hybrid material point method is used to consider the important role of steel bars in the structure;

[0021] C. The material point contact algorithm is used to better reflect the transmission characteristics of explosion stress waves between interfaces of different objects;

[0022] D. Based on the quantitative numerical simulation results, we can obtain the personnel injury level zoning diagram and the structural damage level zoning diagram, so as to further make a comprehensive hazard evaluation of the explosion accident and better guide the formulation of special emergency plans;

[0023] E. The explosive equivalent, explosion point location, structural form, material parameters, etc. can be adjusted arbitrarily in the model, so as to conveniently analyze the changing laws of the danger of explosion accidents in different scenarios based on different simulation results. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 A flow chart for the implementation method;

[0025] Figure 2 A three-dimensional structural model of a subway platform constructed in Example 7;

[0026] Figure 3 The overpressure peak distribution cloud diagram obtained by simulation calculation of a subway platform in Example 7;

[0027] Figure 4 The personnel injury level zoning diagram obtained by simulation calculation of a subway platform in Example 7;

[0028] Figure 5 This is a distribution cloud diagram (top view) of the concrete floor damage factor obtained by simulation calculation of a subway platform in Example 7;

[0029] Figure 6 The concrete floor damage level zoning diagram (top view) obtained by simulation calculation of a subway platform in Example 7;

[0030] Figure 7 The concrete floor damage factor distribution cloud diagram (cross-section diagram) obtained by simulation calculation of a subway platform in Example 7;

[0031] Figure 8 This is a concrete floor damage grade zoning diagram (cross-section diagram) obtained by simulation calculation of a subway platform in Example 7. DETAILED DESCRIPTION

[0032] The present invention is further described below in conjunction with the embodiments, but it should not be understood that the above subject matter of the present invention is limited to the following embodiments. Without departing from the above technical ideas of the present invention, various substitutions and changes are made according to the common technical knowledge and customary means in the art, which should all be included in the protection scope of the present invention.

[0033] Embodiment 1:

[0034] See also Figure 1 This embodiment discloses a method for evaluating the hazard of explosion accidents in subway tunnels based on a generalized interpolation material point method, comprising the following steps:

[0035] 1) Construct an engineering physics model based on the engineering structural characteristics. The engineering physics model includes the structural model of the subway tunnel and the geological model of the surrounding rock and soil. Discretize the continuum of the engineering physics model into N p Material points are generated, and corresponding material parameters are assigned to each material point. A uniform structured grid is used to cover the entire computational domain to generate a background grid.

[0036] 2) Given the initial conditions, boundary conditions and load conditions of the engineering physics model, set the time step for each calculation.

[0037] 3) Set the detonation point location according to the actual situation and calculate the explosive equivalent based on the type and volume of explosives.

[0038] 4) Use the material point method to solve the explosion response.

[0039] 5) Draw an overpressure distribution cloud map based on the explosion response; draw a personnel injury level zoning map in accordance with the personnel injury level classification standards.

[0040] 6) Draw a damage factor cloud map based on the explosion response. Draw a structural damage level zoning map based on the structural damage level classification standard.

[0041] 7) Conduct a comprehensive explosion accident hazard assessment based on the personnel injury level zoning diagram and the structure damage level zoning diagram.

[0042] As a meshless algorithm, the Material Point Method (MPM) has the advantages of no mesh distortion and no convection term in the control equation. This embodiment provides an effective way to study the problem of the hazard assessment method of subway tunnel explosion accidents.

[0043] Embodiment 2:

[0044] The main steps of this embodiment are the same as those of Embodiment 1, wherein step 4) uses the generalized interpolation material point method to perform explicit dynamic solution on the three-dimensional model of the infrastructure structure and the surrounding rock and soil under the action of explosion.

[0045] The calculation process of explosion response in a single time step is as follows: Map material point information and external forces to background grid nodes. Use the generalized interpolation material point method with contact algorithm to display integral solution of the model. After the calculation is completed, output the overpressure value and wavefront distribution of each air material point, output the stress value, displacement value and plastic strain value of each concrete material point, and output the stress value, displacement value and plastic strain value of each rock and soil material point. Remap the calculation results on each material point to the background grid node. Use the interpolation algorithm on the node to obtain the distribution cloud map of each calculation result. Determine whether the calculation has reached the end time. If not, proceed to the next time step. If so, end.

[0046] Embodiment 3:

[0047] The main steps of this embodiment are the same as those of Embodiment 1, wherein in step 4), the subway tunnel structure adopts an HJC concrete model, and the state equation of the HJC concrete model is shown in equations (8)-(10):

[0048] Elastic stage p = K elastic μ (8)

[0049] Transition phase

[0050] Compaction stage

[0051] Where p is the concrete spherical stress, K elastic is the elastic bulk modulus, μ is the elastic volume strain, is the plastic volume strain, F is the compaction coefficient, K1, K2, and K3 are all material parameters. In this embodiment, K1 is 85 GPa, K2 is -171 GPa, and K3 is 208 GPa.

[0052] The steel bars inside the concrete structure are discretized into bar units using the hybrid material point method. The bar unit nodes move together with the concrete material points. The constitutive model of the bar unit nodes adopts the ideal elastic-plastic model. The material model of the steel bar is shown in formula (11):

[0053]

[0054] In the formula, σ y is the yield stress, ε p is the equivalent plastic strain, is the dimensionless equivalent plastic strain rate, A is the initial yield stress at the reference strain rate and reference temperature, B is the material strain hardening modulus, n is the hardening parameter, C is the material strain rate hardening parameter, m is the material softening parameter, T * is the dimensionless temperature.

[0055] The DP constitutive model is adopted for the surrounding rock and soil, and the yield function of the model is shown in formula (12):

[0056]

[0057] Wherein, f is the yield function, I1 is the first stress invariant, J2 is the second deviatoric stress invariant, α and k are positive constants. In this embodiment, α is 0.134, and k is 11.11.

[0058] The state equation used for explosive explosion is shown in formula (13):

[0059]

[0060] Where p is the pressure of the detonation product, E is the unit initial volume internal energy of the detonation product, V is the volume of the detonation product, and A, B, R1, R2 and ω are user-defined material parameters. In this embodiment, A is 371.2 GPa, B is 3.23 GPa, R1 is 4.15, R2 is 0.95, and ω is 0.30.

[0061] The linear polynomial state equation for air is shown in equation (14):

[0062] p=c0+c1μ+c2μ 2 +c3μ 3 +(c4+c5μ+c6μ 2 )E (14)

[0063] Wherein, p is pressure, c0-c6 are user-defined material constants, μ is air volume strain, and E is the internal energy per unit volume of air. In this embodiment, c0-c6 are 0, 0, 0, 0, 0.4, 0.4 and 0, respectively.

[0064] Embodiment 4:

[0065] The main steps of this embodiment are the same as those of embodiment 1, wherein, after step 7), there are also related steps of changing different explosive equivalents, explosion point locations, structural forms and material parameters, repeating the steps, and analyzing the changing laws of the danger of explosion accidents in different scenarios according to different simulation results.

[0066] Embodiment 5:

[0067] The main steps of this embodiment are the same as those of Embodiment 1, wherein the generalized interpolation material point method is used to perform explicit dynamic solution on the three-dimensional model of the infrastructure structure and the surrounding rock and soil under the action of explosion. The shape function and shape function derivative of the generalized interpolation material point method used are shown in equations (15)-(16):

[0068]

[0069]

[0070] Where L is the grid length, 2l p is the particle length, x p is the coordinate of the particle. I are the node coordinates.

[0071] Embodiment 6:

[0072] A method for evaluating the hazard of explosion accidents in subway tunnels based on a generalized interpolation material point method is disclosed, comprising the following steps:

[0073] 1) Construct an engineering physics model based on the engineering structural characteristics. The engineering physics model includes the structural model of the subway tunnel and the geological model of the surrounding rock and soil. Discretize the continuum of the engineering physics model into N p Material points are obtained to obtain a set of three-dimensional lattice coordinates. Corresponding material parameters are assigned to each material point. A layer of computational grid is arranged behind the material point. The density of the material point and the background grid arrangement will affect the accuracy of the calculation results.

[0074] 2) Given the initial conditions, boundary conditions (fixed boundary, non-reflecting boundary, etc.) and load conditions (buildings above the facility, personnel load, etc.) of the engineering physics model, set the time step for each calculation. The time step for each calculation must be less than the maximum critical step to ensure the convergence of the calculation.

[0075] 3) Set the detonation point according to the actual situation, and calculate the explosive equivalent according to the type and volume of the explosive. The explosive equivalent is calculated by dividing the total internal energy of the explosive by the energy released by the explosion of unit mass of TNT.

[0076] 4) Solve the explosion response using the material point method. The generalized interpolation material point method is used to explicitly solve the dynamics of the three-dimensional model of the infrastructure structure and the surrounding rock and soil under the action of the explosion. The HJC model is used for concrete, the bar unit model is used for steel bars, the DP model is used for rock and soil, and the JWL explosion model is used for explosives. The contact between air and concrete structure and rock and soil is also considered.

[0077] The calculation process of explosion response in a single time step is as follows: map material point information and external forces to background grid nodes. Use the generalized interpolation material point method with contact algorithm to solve the model by explicit integration. The material point contact algorithm proposed by Bardenhagen is used for air and concrete structure, and between concrete structure and rock and soil. After the calculation is completed, output the overpressure value and wavefront distribution of each air material point, output the stress value, displacement value and plastic strain value of each concrete material point, and output the stress value, displacement value and plastic strain value of each rock and soil material point. Remap the calculation results on each material point to the background grid node. Use the interpolation algorithm on the node to obtain the distribution cloud map of each calculation result. Determine whether the calculation has reached the end time. If not, proceed to the next time step. If so, end.

[0078] The HJC concrete model is used in the subway tunnel structure, which requires input of parameters such as the initial density, unconfined compressive strength, elastic bulk modulus, and specific heat capacity of the concrete material. The state equation of the HJC concrete model is shown in equations (17)-(19):

[0079] Elastic stage p = K elastic μ (17)

[0080] Transition phase

[0081] Compaction stage

[0082] Where p is the concrete spherical stress, K elastic is the elastic bulk modulus, μ is the elastic volume strain, is the plastic volume strain, F is the compaction coefficient, K1, K2, and K3 are all material parameters. In this embodiment, K1 is 85 GPa, K2 is -171 GPa, and K3 is 208 GPa.

[0083] The steel bars inside the concrete structure are discretized into bar units using the hybrid material point method. The bar unit nodes move together with the concrete material points. The constitutive model of the bar unit nodes adopts the ideal elastic-plastic model, which requires the input of parameters such as shear modulus and plastic modulus. The material model of the steel bar is shown in formula (20):

[0084]

[0085] In the formula, σ y is the yield stress, ε p is the equivalent plastic strain, is the dimensionless equivalent plastic strain rate, A is the initial yield stress at the reference strain rate and reference temperature, B is the material strain hardening modulus, n is the hardening parameter, C is the material strain rate hardening parameter, m is the material softening parameter, T * is the dimensionless temperature.

[0086] The DP constitutive model is used for the surrounding rock and soil, and parameters such as cohesion and internal friction angle of the rock and soil need to be input. The yield function of the model is shown in formula (21):

[0087]

[0088] Wherein, f is the yield function, I1 is the first stress invariant, J2 is the second deviatoric stress invariant, α and k are positive constants. In this embodiment, α is 0.134, and k is 11.11 kPa.

[0089] In the state equation of explosive explosion, it is necessary to input parameters such as the internal energy per unit volume of the explosive, detonation velocity, initial density, specific heat ratio, etc. The state equation used for explosive explosion is shown in formula (22):

[0090]

[0091] Where p is the pressure of the detonation product, E is the unit initial volume internal energy of the detonation product, V is the volume of the detonation product, and A, B, R1, R2 and ω are user-defined material parameters. In this embodiment, A is 371.2 GPa, B is 3.23 GPa, R1 is 4.15, R2 is 0.95, and ω is 0.30.

[0092] The linear polynomial state equation for air requires the input of parameters such as air density, specific heat ratio, and wave speed. The linear polynomial state equation for air is shown in equation (23);

[0093] p=c0+c1μ+c2μ 2 +c3μ 3 +(c4+c5μ+c6μ 2 )E (23)

[0094] Wherein, p is pressure, c0-c6 are user-defined material constants, μ is air volume strain, and E is the internal energy per unit volume of air. In this embodiment, c0-c6 are 0, 0, 0, 0, 0.4, 0.4, 0, respectively.

[0095] 5) According to the standard for classifying the level of injury to personnel caused by shock wave overpressure in Table 1, a zoning diagram of the level of injury to personnel is drawn based on the overpressure distribution cloud diagram.

[0096] Table 1

[0097]

[0098] 6) Determine the structural damage factor by using the ratio of the equivalent plastic strain increment and plastic volume strain increment at the current moment to the accumulated total equivalent plastic strain and plastic volume strain:

[0099]

[0100] Where D is the damage factor, Δε p and Δμ p are the equivalent plastic strain increment and plastic volume strain increment of the current time step respectively; and They are the total equivalent plastic strain and the total plastic volume strain respectively. Then the damage factor cloud map is drawn, and the structural damage level zoning map is drawn in accordance with the structural damage level classification standard in Table 2.

[0101] Table 2

[0102]

[0103] 7) Conduct a comprehensive explosion accident hazard assessment based on the personnel injury level zoning diagram and the structure damage level zoning diagram.

[0104] 8) Change different explosive equivalents, explosion point locations, structural forms and material parameters, repeat the steps, and analyze the changing laws of the danger of explosion accidents in different scenarios based on different simulation results.

[0105] This embodiment makes up for the defects of previous qualitative evaluation based on experience, overcomes the numerical difficulties of traditional finite element simulation methods caused by grid distortion during explosion simulation, and proposes a set of practical and feasible quantitative evaluation methods for hazards. It has certain practical application value, will have a positive role in promoting the formulation of special emergency plans, and will have guiding significance for post-disaster repair and subsequent recovery work.

[0106] Embodiment 7:

[0107] The main steps of this embodiment are the same as those of embodiment 1. In this embodiment, a subway station is selected. The entire model size is 99m×61m×40m, the platform structure size is 19m×61m×6m, and the structure thickness is 1m. Figure 2 The three-dimensional model shown in the figure is discretized into 247,599 material points. At the same time, a 1m×1m×1m background grid is arranged in the entire area. The explosive equivalent is set to 5kg and the location is at the geometric center of the platform structure bottom plate. After numerical calculation of the model using the material point method, the following is obtained: Figure 3 The overpressure distribution cloud diagram shown in the figure is used, and according to the standard for classifying the injury level of personnel by the shock wave overpressure, a personnel injury level zoning diagram is drawn, as shown in Figure 4 Then the calculation is as follows Figure 5 and Figure 7 The concrete slab damage factor distribution cloud diagram is shown in the figure, and according to the structural damage grade classification standard, the following is drawn Figure 6 and Figure 8The structural damage level zoning diagram is shown.

[0108] Embodiment 8:

[0109] This embodiment discloses a method for evaluating the hazard of explosion accidents in subway tunnels based on a generalized interpolation material point method, comprising the following steps:

[0110] 1) Construct an engineering physics model based on the engineering structural characteristics. The engineering physics model includes the structural model of the subway tunnel and the geological model of the surrounding rock and soil. Discretize the continuum of the engineering physics model into N p Material points are generated, and corresponding material parameters are assigned to each material point. A uniform structured grid is used to cover the entire computational domain to generate a background grid.

[0111] 2) Given the initial conditions, boundary conditions and load conditions of the engineering physics model, set the time step for each calculation.

[0112] 3) Set the detonation point location according to the actual situation and calculate the explosive equivalent based on the type and volume of explosives.

[0113] 4) Solve the explosion response using the material point method. The generalized interpolation material point method is used to explicitly solve the dynamics of the three-dimensional model of the infrastructure structure and the surrounding rock and soil under the action of the explosion.

[0114] The calculation process of explosion response in a single time step is as follows: Map material point information and external forces to background grid nodes. Use the generalized interpolation material point method with contact algorithm to display integral solution of the model. After the calculation is completed, output the overpressure value and wavefront distribution of each air material point, output the stress value, displacement value and plastic strain value of each concrete material point, and output the stress value, displacement value and plastic strain value of each rock and soil material point. Remap the calculation results on each material point to the background grid node. Use the interpolation algorithm on the node to obtain the distribution cloud map of each calculation result. Determine whether the calculation has reached the end time. If not, proceed to the next time step. If so, end.

[0115] The HJC concrete model is used in the subway tunnel structure. The state equations of the HJC concrete model are shown in equations (8)-(10):

[0116] Elastic stage p = K elastic μ (8)

[0117] Transition phase

[0118] Compaction stage

[0119] Where p is the concrete spherical stress, K elastic is the elastic bulk modulus, μ is the elastic volume strain, is the plastic volume strain, F is the compaction coefficient, K1, K2, and K3 are all material parameters. In this embodiment, K1 is 85 GPa, K2 is -171 GPa, and K3 is 208 GPa.

[0120] The steel bars inside the concrete structure are discretized into bar units using the hybrid material point method. The bar unit nodes move together with the concrete material points. The constitutive model of the bar unit nodes adopts the ideal elastic-plastic model. The material model of the steel bar is shown in formula (11):

[0121]

[0122] In the formula, σ y is the yield stress, ε p is the equivalent plastic strain, is the dimensionless equivalent plastic strain rate, A is the initial yield stress at the reference strain rate and reference temperature, B is the material strain hardening modulus, n is the hardening parameter, C is the material strain rate hardening parameter, m is the material softening parameter, T * is the dimensionless temperature.

[0123] The DP constitutive model is adopted for the surrounding rock and soil, and the yield function of the model is shown in formula (12):

[0124]

[0125] Wherein, f is the yield function, I1 is the first stress invariant, J2 is the second deviatoric stress invariant, α and k are positive constants. In this embodiment, α is 0.134, and k is 11.11 kPa.

[0126] The state equation used for explosive explosion is shown in formula (13):

[0127]

[0128] Where p is the pressure of the detonation product, E is the unit initial volume internal energy of the detonation product, V is the volume of the detonation product, and A, B, R1, R2 and ω are user-defined material parameters. In this embodiment, A is 371.2 GPa, B is 3.23 GPa, R1 is 4.15, R2 is 0.95, and ω is 0.30.

[0129] The linear polynomial state equation for air is shown in equation (14):

[0130] p=c0+c1μ+c2μ 2 +c3μ 3 +(c4+c5μ+c6μ 2 )E (14)

[0131] Wherein, p is pressure, c0-c6 are user-defined material constants, μ is air volume strain, and E is the internal energy per unit volume of air. In this embodiment, c0-c6 are 0, 0, 0, 0, 0.4, 0.4, 0, respectively.

[0132] The generalized interpolation material point method is used to perform explicit dynamic solutions on the three-dimensional model of the infrastructure structure and the surrounding rock and soil under the action of explosion. The shape function and shape function derivative of the generalized interpolation material point method used are shown in equations (15)-(16):

[0133]

[0134]

[0135] Where L is the grid length, 2l p is the particle length, x p is the coordinate of the particle. I are the node coordinates.

[0136] 5) Draw an overpressure distribution cloud map based on the explosion response; draw a personnel injury level zoning map in accordance with the personnel injury level classification standards.

[0137] 6) Draw a damage factor cloud map based on the explosion response. Draw a structural damage level zoning map based on the structural damage level classification standard.

[0138] 7) Conduct a comprehensive explosion accident hazard assessment based on the personnel injury level zoning diagram and the structure damage level zoning diagram.

[0139] 8) Change different explosive equivalents, explosion point locations, structural forms and material parameters, repeat the steps, and analyze the relevant steps of the changing law of the danger of explosion accidents in different scenarios according to different simulation results.

[0140] It is worth noting that the Material Point Method (MPM), as a meshless algorithm, has the advantages of no mesh distortion and no convection term in the control equation. This embodiment provides an effective way to study the problem of the hazard assessment method of subway tunnel explosion accidents.

Claims

1. A method for evaluating the hazard of subway tunnel explosion accidents based on the generalized interpolation material point method, characterized in that: The following steps are involved: 1) Constructing an engineering physics model according to the engineering structural characteristics; the engineering physics model includes a structural model of the subway tunnel and a geological model of the surrounding rock and soil; discretizing the continuum of the engineering physics model into N p material points, assign corresponding material parameters to each material point; use a uniform structured grid to cover the entire calculation domain to generate a background grid; 2) Given the initial conditions, boundary conditions and load conditions of the engineering physics model, set the time step for each calculation; 3) Set the detonation point according to the actual situation and calculate the explosive equivalent according to the type and volume of explosives; 4) The material point method is used to solve the explosion response; the HJC concrete model is used for the subway tunnel structure; the steel bars inside the concrete structure are discretized into rod units using the hybrid material point method; the rod unit nodes and the concrete material points move together; the constitutive model of the rod unit nodes adopts the ideal elastic-plastic model; the calculation process of the explosion response of a single time step is: mapping the material point information and external forces to the background grid nodes; using the generalized interpolation material point method with contact algorithm to perform explicit integral solution on the model; After the calculation is completed, the overpressure value and wavefront distribution of each air material point are output, the stress value, displacement value and plastic strain value of each concrete material point are output, and the stress value, displacement value and plastic strain value of each rock and soil material point are output; the calculation results on each material point are remapped to the background grid node; the interpolation algorithm is used on the node to obtain the distribution cloud map of each calculation result; it is determined whether the calculation has reached the end time, if not, it will go to the next time step, if so, it will end; 5) Draw an overpressure distribution cloud map based on the explosion response; draw a personnel injury level zoning map in accordance with the personnel injury level classification standard; 6) Draw a damage factor cloud map based on the explosion response; draw a structural damage level zoning map based on the structural damage level classification standard; 7) Conduct a comprehensive explosion accident hazard assessment based on the personnel injury level zoning diagram and the structure damage level zoning diagram.

2. The method for evaluating the hazard of explosion accidents in subway tunnels based on the generalized interpolation material point method according to claim 1 is characterized by: After step 7), there are also related steps of changing different explosive equivalents, explosion point locations, structural forms and material parameters, repeating the steps, and analyzing the changing laws of the danger of explosion accidents in different scenarios according to different simulation results.

Images