A safety grading evaluation method and system for buried steel pipes under rockfall impact

Abstract

The present invention discloses a safety grading evaluation method and system for buried steel pipes under the impact of falling rocks, and relates to the technical field of falling rock disasters. The safety grading evaluation method of the present invention obtains the maximum ovality and maximum tensile strain of the buried steel pipe after the impact of falling rocks through numerical analysis model simulation; obtains the fitting formula of the falling rock kinetic energy, impact offset, maximum tensile strain and maximum ovality through fitting and calculation; establishes a grading index to obtain the rockfall kinetic energy and impact offset of the actual buried steel pipe site; obtains the maximum tensile strain of the steel pipe through the fitting formula, and compares it with the grading index to obtain the safety level of the buried steel pipe. This method can not only provide a scientific basis for the safety grading evaluation of buried steel pipes under the impact of falling rocks, but also provide assistance for the reasonable design of steel pipe lines, thereby ensuring the quality and safety of buried steel pipes in rockfall risk areas.

Description

Technical Field

[0001] The present invention relates to the technical field of rockfall disasters, and in particular to a safety grading evaluation method and system for buried steel pipes under rockfall impact. Background Art

[0002] With the rapid development of my country's energy industry in recent years, long-distance buried oil and gas pipelines, as transmission vehicles, have expanded in unprecedented length and breadth, becoming a crucial component of surface engineering. Most of these long-distance oil and gas pipelines traverse rockfall-prone areas, such as mountainous areas and seismic zones. In engineering practice, a crucial aspect of buried pipeline route design is determining the appropriate offset distance between the pipeline and potential rockfall impact points. For existing operational pipelines, assessing the safety of buried pipelines based on rockfall parameters and impact offset distance is a crucial component of risk management.

[0003] Chinese invention patent CN108956336B discloses a test device for the impact load and shock absorption effects of buried pipelines. This device can simulate indoor tests of the impact load and shock absorption effects of buried pipelines under different soil types, impact load magnitudes and directions, and spring stiffnesses. By measuring and analyzing the strain and deformation characteristics and damage process of the pipeline, it provides a test basis for the impact resistance of the buried pipeline. However, this device is suitable for indoor analysis and does not fully adapt to actual buried pipelines and site environments. Currently, there is still a lack of scientific basis and technical solutions for the safety classification evaluation of existing buried steel pipes under the impact of falling rocks. Summary of the Invention

[0004] The problem to be solved by the present invention is to provide a safety grading evaluation method and system for buried steel pipes under the impact of falling rocks, and to perform safety grading evaluation and analysis on existing actual buried steel pipes under the impact of falling rocks.

[0005] In a first aspect, the present invention provides a method for evaluating the safety of buried steel pipes under rockfall impact, comprising the following steps:

[0006] S1. Obtain parameter information of the actual buried steel pipe and the site where it is located, and construct a numerical analysis model based on the parameter information;

[0007] S2. Based on the constructed numerical analysis model, simulation calculations are performed under different rockfall kinetic energies and different impact offsets to obtain the simulation results for each impact, including the maximum ovality and maximum tensile strain of the buried steel pipe;

[0008] S3. Fitting the maximum ovality and maximum tensile strain of the buried steel pipe under different rockfall kinetic energy and different impact offsets to obtain a first fitting formula;

[0009] S4. Fitting the maximum tensile strain under different rockfall kinetic energies and different impact offsets with the rockfall kinetic energy and impact offset to obtain a second fitting formula;

[0010] S5. Establish safety classification indicators for buried steel pipes;

[0011] S6. Obtain the kinetic energy and impact offset of the rockfall at the actual site where the buried steel pipe is located, substitute them into the second fitting formula, and obtain the maximum tensile strain of the buried steel pipe;

[0012] S7. Compare the maximum tensile strain of the buried steel pipe with the safety grading index of the buried steel pipe to obtain the safety grade of the buried steel pipe.

[0013] Preferably, in step S1, the parameter information includes: the geometric dimensions, material parameters and burial depth of the actual buried steel pipe, as well as the soil material and rockfall material parameters of the site.

[0014] Preferably, the numerical analysis model is constructed according to the parameter information, and the method includes the following sub-steps:

[0015] S11. Use Solid164 entity elements to model the soil and fallen rocks at the site where the buried steel pipe is located;

[0016] S12, the buried steel pipe is modeled using Shell163 shell elements;

[0017] S13, dividing the soil and air in the unit modeling into ALE grids; dividing the rest of the unit modeling into Lagrangian grids, and coupling the ALE grid and the Lagrangian grid using the fluid-structure coupling keyword;

[0018] S14. Set the soil around and at the bottom as non-reflecting boundary conditions.

[0019] Preferably, in step S2, the simulation calculation includes:

[0020] Set the rockfall of preset weight to different initial velocities, and simulate different kinetic energies of rockfall by changing the initial velocity.

[0021] By changing the horizontal distance between the rockfall and the steel pipe axis, different impact offsets can be obtained.

[0022] Obtain the maximum ovality and maximum tensile strain of the steel pipe during each impact simulation.

[0023] Preferably, in step S3, the first fitting formula is:

[0024] ;

[0025] Where Δ represents the maximum ovality of the steel pipe, and ε represents the maximum tensile strain of the steel pipe.

[0026] Preferably, in step S4, the second fitting formula is:

[0027] ;

[0028] Where E represents the kinetic energy of the rockfall and R represents the impact offset.

[0029] Preferably, in step S5, establishing a safety classification index for buried steel pipes includes:

[0030] The ultimate tensile strain of buried steel pipe steel is taken as the first-level index, and the first-level index A1 is expressed as:

[0031]

[0032] One fifth of the ultimate tensile strain of the buried steel pipe is used as the secondary index, and the secondary index A2 is expressed as:

[0033]

[0034] Taking the ovality limit of the buried steel pipe as the third-level index, based on the first fitting formula, the third-level index A3 is expressed as:

[0035] .

[0036] Preferably, in step S6, the kinetic energy and impact offset of the rockfall at the site where the actual buried steel pipe is located are obtained, and the impact kinetic energy of the rockfall is calculated by measuring the volume of the rockfall and the vertical height difference between the rockfall separation point and the buried steel pipe; the horizontal distance between the rockfall impact point and the buried steel pipe is measured to obtain the impact offset; and the maximum tensile strain of the actual buried steel pipe is calculated by the second fitting formula.

[0037] Preferably, in step S7, the safety level of the buried steel pipe is divided as follows:

[0038] When 0 < maximum tensile strain < level 3 index, the safety level corresponding to the buried steel pipe is level 4;

[0039] When the third-level index < maximum tensile strain < second-level index, the corresponding safety level of the buried steel pipe is the third level;

[0040] When the secondary index < maximum tensile strain < primary index, the corresponding safety level of the buried steel pipe is the second level;

[0041] When the first-level index is less than the maximum tensile strain, the corresponding safety level of the buried steel pipe is the first level.

[0042] In a second aspect, the present invention further provides a safety grading evaluation system for buried steel pipes under rockfall impact, comprising: a modeling unit, a simulation unit, a first fitting unit, a second fitting unit, an establishment unit, a calculation unit, and an evaluation unit:

[0043] The modeling unit is used to obtain parameter information of the actual buried steel pipe and the site where it is located, and to construct a numerical analysis model based on the parameter information;

[0044] The simulation unit is used to simulate and calculate the numerical analysis model under different rockfall kinetic energy and different impact offset conditions to obtain the simulation results of each impact;

[0045] The first fitting unit is used to fit the maximum ovality and the maximum tensile strain under different rockfall kinetic energies and different impact offsets to obtain a first fitting formula;

[0046] The second fitting unit is used to fit the maximum tensile strain under different rockfall kinetic energies and different impact offsets with the rockfall kinetic energy and impact offset to obtain a second fitting formula;

[0047] The establishing unit is used to establish safety classification indicators for buried steel pipes;

[0048] The calculation unit is used to obtain the kinetic energy and impact offset of the rockfall at the actual site where the buried steel pipe is located, and substitute them into the second fitting formula to obtain the maximum tensile strain of the buried steel pipe;

[0049] The evaluation unit is used to compare the maximum tensile strain of the buried steel pipe with the classification index to obtain the safety level of the buried steel pipe. According to actual engineering requirements, the buried steel pipe route is set based on the corresponding safety level, and the offset between the buried steel pipe and the potential rockfall impact point is greater than the safety offset of the corresponding safety level.

[0050] Preferably, the modeling unit includes: a component modeling unit, a division unit and a setting unit; the component modeling unit models the soil and fallen rocks using Solid164 entity units, and models the steel pipe using Shell163 shell units; the division unit divides the soil and air into ALE grids, and the rest into Lagrangian grids, and couples the ALE grid and the Lagrangian grid through fluid-solid coupling keywords; the setting unit is used to set the surrounding area and bottom of the soil to non-reflection boundary conditions.

[0051] Preferably, the simulation unit includes: a rockfall simulation unit, an impact offset simulation unit and an output unit; the rockfall simulation unit sets different initial velocities for rockfalls of preset weights, and simulates different rockfall kinetic energies by changing the magnitude of the initial velocities; the impact offset simulation unit obtains different impact offsets by changing the horizontal distance from the rockfall to the axis of the steel pipe; the maximum ovality and maximum tensile strain of the steel pipe during each impact simulation are obtained through the output unit.

[0052] Compared with the prior art, the present invention adopts the above technical solution and has the following technical effects:

[0053] The safety grading evaluation method for buried steel pipes under the impact of falling rocks of the present invention obtains the maximum tensile strain of the buried steel pipes under the impact of falling rocks through simulation, analysis and calculation, and then combines the grading indicators to realize a graded evaluation of the safety degree of the buried steel pipes after the impact of falling rocks. This method can not only provide a scientific basis for the safety grading evaluation of buried steel pipes under the impact of falling rocks, but also help the reasonable design of steel pipe lines, thereby ensuring the quality and safety of buried steel pipes in rockfall risk areas. BRIEF DESCRIPTION OF THE DRAWINGS

[0054] Figure 1 This is a flow chart of the safety classification evaluation method for buried steel pipes under rockfall impact of the present invention;

[0055] Figure 2 Schematic diagram of the positional relationship between the rockfall impact point and the buried steel pipe according to an embodiment of the present invention;

[0056] Figure 3 This is a fitting result diagram of the maximum ovality and maximum tensile strain of the buried steel pipe according to an embodiment of the present invention;

[0057] Figure 4 This is a fitting result diagram of the maximum tensile strain of the buried steel pipe, the kinetic energy of the rockfall, and the impact offset according to an embodiment of the present invention;

[0058] Figure 5 This is a schematic diagram of the structure of a safety grading evaluation system for buried steel pipes under rockfall impact according to an embodiment of the present invention;

[0059] Markings in the figure:

[0060] 1. Impact point No. 1; 2. Impact point No. 2; 3. Impact point No. 3; 4. Impact point No. 4; 5. Impact point No. 5; 6. Buried steel pipe; 100. Safety grading evaluation system; 110. Modeling unit; 120. Simulation unit; 130. First fitting unit; 140. Second fitting unit; 150. Establishment unit; 160. Calculation unit; 170. Evaluation unit. DETAILED DESCRIPTION

[0061] In order to make the purpose, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. The components of the embodiments of the present invention generally described and shown in the drawings herein can be arranged and designed in various different configurations. Therefore, the following detailed description of the embodiments of the present invention provided in the drawings is not intended to limit the scope of the claimed invention, but merely represents selected embodiments of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of the present invention.

[0062] It should be noted that similar reference numerals and letters represent similar items in the following drawings. Therefore, once an item is defined in one drawing, it does not need to be further defined or explained in subsequent drawings. At the same time, in the description of the present invention, the terms "first" and "second" are used only to distinguish the description and should not be understood as indicating or implying relative importance.

[0063] Example 1:

[0064] like Figure 1 As shown, this embodiment provides a safety classification evaluation method for buried steel pipes under rockfall impact, including the following steps:

[0065] S1. Obtain parameter information of the actual buried steel pipe and the site where it is located, and construct a numerical analysis model based on the parameter information.

[0066] It should be noted that in this embodiment, the parameter information includes: the geometric dimensions, material parameters and burial depth of the buried steel pipe, as well as the soil material and rockfall parameters of the site; constructing the numerical analysis model includes the following sub-steps:

[0067] S11. The soil and rockfall were modeled using Solid164 entity elements;

[0068] S12, the buried steel pipe is modeled using Shell163 shell elements;

[0069] S13, dividing the soil into ALE grids and the rest into Lagrangian grids, and coupling the ALE grid and the Lagrangian grid using the fluid-structure coupling keyword;

[0070] S14. Set the surrounding areas and bottom of the soil as non-reflecting boundary conditions to obtain a numerical analysis model.

[0071] S2. Under different rockfall kinetic energy and impact offset conditions, the numerical analysis model is simulated and calculated to obtain the simulation results of each impact, wherein the impact simulation results include the maximum ovality and maximum tensile strain of the steel pipe.

[0072] In this embodiment, step S2 includes the following sub-steps:

[0073] S21, setting different initial velocities for falling rocks of preset weight, and simulating different kinetic energies of falling rocks by varying the magnitude of the initial velocities;

[0074] S22, different impact offsets are obtained by changing the horizontal distance between the rockfall and the steel pipe axis;

[0075] S23. Obtain the maximum ovality and maximum tensile strain of the steel pipe during each impact simulation.

[0076] Specifically, in this embodiment, the rockfall mass is set to 20 t, and three different rockfall kinetic energies are simulated by changing the initial velocity: 1000 kJ, 2000 kJ, and 3000 kJ. The relative position relationship between the rockfall impact point and the buried steel pipe 6 is obtained as follows: Figure 2 As shown in the figure, the rockfall impact points from near to far are: impact point 1, impact point 2, impact point 3, impact point 4, impact point 5, and the corresponding impact offsets are 0 m, 1 m, 2 m, 3 m, and 4 m.

[0077] The maximum ovality and maximum tensile strain of the steel pipe under different rockfall kinetic energies and different impact offsets of this embodiment are shown in Table 1.

[0078] Table 1

[0079]

[0080] S3. Fit the maximum ovality and maximum tensile strain of the steel pipe under different rockfall kinetic energies and different impact offsets to obtain a first fitting formula.

[0081] The maximum ovality and maximum tensile strain of the steel pipe in Table 1 are fitted, and the fitting results are as follows: Figure 3 As shown in the figure, Δ represents the maximum ovality of the steel pipe, and ε represents the maximum tensile strain of the steel pipe. The first fitting formula is:

[0082] .

[0083] S4. Fit the maximum tensile strain of the steel pipe under different rockfall kinetic energies and different impact offsets to the rockfall kinetic energy and impact offset to obtain a second fitting formula.

[0084] The maximum tensile strain of the steel pipe in Table 1, the kinetic energy of rockfall and the impact deflection are fitted, and the fitting results are as follows: Figure 4 As shown in the figure, ε represents the maximum tensile strain of the steel pipe, E represents the kinetic energy of the rockfall, and R represents the impact offset. The second fitting formula is:

[0085] .

[0086] S5. Establish grading indicators.

[0087] In this embodiment, the constructed grading indicators specifically include:

[0088] The ultimate tensile strain of steel pipe steel is used as the first-level indicator;

[0089] One fifth of the ultimate tensile strain of the steel pipe is used as the secondary index;

[0090] The ovality limit of the steel pipe is used as the third-level indicator;

[0091] According to the design specifications, the ultimate tensile strain of the steel pipe is generally taken as 0.02, and the ovality limit is generally taken as 0.03.

[0092] Therefore, the first-level indicators are:

[0093] ;

[0094] In the formula, A1 is the first-level indicator, is the ultimate tensile strain of the steel pipe.

[0095] The secondary indicators are:

[0096] ;

[0097] In the formula, A2 is the secondary indicator, is the ultimate tensile strain of the steel pipe.

[0098] Using the first fitting formula, the three-level indicators are:

[0099] ;

[0100] Where A3 is the third-level indicator, It is the limit value of steel pipe ovality.

[0101] S6. Substitute the kinetic energy of rockfall and impact offset at the actual site where the buried steel pipe is located into the second fitting formula to obtain the maximum tensile strain of the buried steel pipe.

[0102] In this embodiment, obtaining the kinetic energy and impact offset of rockfall at the site where the actual buried steel pipe is located includes the following sub-steps:

[0103] S61. The impact kinetic energy of the rockfall is calculated by measuring the volume of the rockfall and the vertical height difference between the rockfall separation point and the buried steel pipe. The calculation formula is:

[0104] ;

[0105] Where E represents the kinetic energy of the rockfall, m represents the mass of the rockfall, g is the acceleration due to gravity, and h is the vertical height difference between the rockfall separation point and the buried steel pipe.

[0106] S62, by measuring the horizontal distance between the rockfall impact point and the buried steel pipe, the impact offset distance R is obtained;

[0107] S63. Calculate the maximum tensile strain of the actual buried steel pipe using the second fitting formula.

[0108] S7. Compare the maximum tensile strain of the buried steel pipe with the classification index to obtain the safety level of the buried steel pipe.

[0109] In this embodiment, the safety levels of buried steel pipes include:

[0110] When 0 < maximum tensile strain < level 3 index, the safety level corresponding to the buried steel pipe is level 4;

[0111] When the third-level index < maximum tensile strain < second-level index, the corresponding safety level of the buried steel pipe is the third level;

[0112] When the secondary index < maximum tensile strain < primary index, the corresponding safety level of the buried steel pipe is the second level;

[0113] When the first-level index is less than the maximum tensile strain, the safety level corresponding to the buried steel pipe is the first level;

[0114] Specifically, in this embodiment, rockfall is simulated using the MAT_RIGID material model; air is simulated using the MAT_VACUUM material model; soil is simulated using the MAT-MOHR-COULOMB material model; and steel pipes are simulated using the MAT-PLASTIC-KINEMATIC material model.

[0115] The numerical analysis model constructed in step S1 simulates the dynamic effects of actual rockfall on buried steel pipes more accurately, allowing for a precise safety assessment of buried steel pipes under varying rockfall kinetic energy and impact offsets. Furthermore, through the methods of steps S2 to S7, a relationship is established between rockfall kinetic energy, impact offset, maximum tensile strain, and maximum ovality of the steel pipe, making the safety assessment of buried steel pipes more scientific and rational.

[0116] Example 2:

[0117] like Figure 5 As shown, this embodiment provides a safety grading evaluation system 100 for buried steel pipes under rockfall impact, corresponding to the safety grading evaluation method for buried steel pipes under rockfall impact described in the present invention.

[0118] The security classification evaluation system 100 includes:

[0119] Modeling unit 110, used to obtain parameter information of the actual buried steel pipe and the site where it is located, and build a numerical analysis model based on the parameter information;

[0120] The simulation unit 120 is used to simulate the numerical analysis model under different rockfall kinetic energies and different impact offsets to obtain the simulation results of each impact, wherein the impact simulation results include the maximum ovality and maximum tensile strain of the steel pipe;

[0121] The first fitting unit 130 is used to fit the maximum ovality and the maximum tensile strain under different rockfall kinetic energies and different impact offsets to obtain a first fitting formula;

[0122] The second fitting unit 140 is used to fit the maximum tensile strain under different rockfall kinetic energies and different impact offsets to the rockfall kinetic energy and impact offset to obtain a second fitting formula;

[0123] An establishing unit 150, configured to establish a grading index;

[0124] The calculation unit 160 is used to obtain the kinetic energy and impact offset of the rockfall at the site where the buried steel pipe is actually located, and substitute them into the second fitting formula to obtain the maximum tensile strain of the buried steel pipe;

[0125] The evaluation unit 170 is used to compare the maximum tensile strain of the buried steel pipe with the classification index to obtain the safety level of the buried steel pipe.

[0126] In this embodiment, the modeling unit 110 includes:

[0127] Component modeling unit, used to model soil and rockfall using Solid164 solid units; and to model steel pipes using Shell163 shell units;

[0128] The division unit is used to divide the soil and air into ALE grids; the rest of the grid is divided into Lagrangian grids, and the ALE grid and Lagrangian grid are coupled through the fluid-structure coupling keyword;

[0129] The boundary setting unit is used to set the soil around and at the bottom as non-reflecting boundary conditions.

[0130] In this embodiment, the simulation unit 120 includes:

[0131] The kinetic energy simulation unit is used to set different initial velocities for falling rocks of preset weight, and simulate different kinetic energies of falling rocks by changing the magnitude of the initial velocities;

[0132] Impact offset simulation unit, used to obtain different impact offsets by changing the horizontal distance from the rockfall to the steel pipe axis;

[0133] Output unit, used to obtain the maximum ovality and maximum tensile strain of the steel pipe during each impact simulation.

[0134] In this embodiment, the establishing unit 150 includes:

[0135] The first-level indicator unit takes the ultimate tensile strain of steel pipe steel as the first-level indicator;

[0136] Secondary index unit: one fifth of the ultimate tensile strain of the steel pipe is used as the secondary index;

[0137] The third-level indicator unit takes the ovality limit of the steel pipe as the third-level indicator.

[0138] This embodiment ensures the safety of the buried steel pipe under the impact of falling rocks by setting the offset between the designed route of the buried steel pipe and the potential rockfall impact point to be greater than the safety offset, reduces safety accidents caused by structural deformation or cracking, and improves the safety and reliability of the buried steel pipe.

[0139] Furthermore, the specific application of the safety grading evaluation system for buried steel pipes under the impact of falling rocks includes:

[0140] Measure the volume of the falling rock and the vertical height difference between its departure point and the buried steel pipe, and calculate the impact kinetic energy of the falling rock;

[0141] Measure the horizontal distance between the rockfall impact point and the buried steel pipe;

[0142] The maximum tensile strain of the buried steel pipe is calculated;

[0143] The maximum tensile strain of the buried steel pipe is compared with the classification index to obtain the safety classification evaluation of the buried steel pipe.

[0144] Furthermore, the safety classification of buried steel pipes under the impact of falling rocks is evaluated, including:

[0145] Based on the first-level index, the second-level index and the third-level index, the safe offset of the buried steel pipe design route under the potential threat of rockfall at different safety levels is calculated, and the safety levels include the first level, the second level, the third level and the fourth level;

[0146] According to actual engineering requirements, the offset between the buried steel pipe design route and the potential rockfall impact point is set to be greater than the safety offset at the corresponding safety level.

[0147] As can be seen, the grading evaluation system proposed in this invention is easy to implement and simplifies the process for assessing the safety of buried steel pipes under rockfall impact. It can provide a scientific basis for the grading evaluation of the safety of buried steel pipes under rockfall impact, and can also help to rationally design steel pipe lines to ensure the quality and safety of buried steel pipes in rockfall-prone areas. The grading evaluation method of this invention not only provides guidance for the current grading evaluation of the safety of buried steel pipes under rockfall impact, but also provides a reference for similar projects in the future.

[0148] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principles of the present invention, and these improvements and modifications should also be regarded as the scope of protection of the present invention.

Claims

1. A safety grading evaluation method for buried steel pipes under rockfall impact, characterized in that: The steps include: S1. Obtain parameter information of the actual buried steel pipe and the site where it is located, and construct a numerical analysis model based on the parameter information; S2. Based on the constructed numerical analysis model, simulation calculations are performed under different rockfall kinetic energies and different impact offsets to obtain the simulation results for each impact, including the maximum ovality and maximum tensile strain of the buried steel pipe; S3. Fitting the maximum ovality and maximum tensile strain of the buried steel pipe under different rockfall kinetic energy and different impact offsets to obtain a first fitting formula; S4. Fitting the maximum tensile strain under different rockfall kinetic energies and different impact offsets with the rockfall kinetic energy and impact offset to obtain a second fitting formula; S5. Establish safety classification indicators for buried steel pipes; S6. Obtain the kinetic energy and impact offset of the rockfall at the actual site where the buried steel pipe is located, substitute them into the second fitting formula, and obtain the maximum tensile strain of the buried steel pipe; S7. Compare the maximum tensile strain of the buried steel pipe with the safety grading index of the buried steel pipe to obtain the safety grade of the buried steel pipe.

2. The safety classification evaluation method for buried steel pipes under rockfall impact according to claim 1 is characterized in that: In step S1, the parameter information includes: the geometric dimensions, material parameters and burial depth of the actual buried steel pipe, as well as the soil material and rockfall material parameters of the site; The numerical analysis model is constructed according to the parameter information, and the method includes the following sub-steps: S11. Use Solid164 entity elements to model the soil and fallen rocks at the site where the buried steel pipe is located; S12, the buried steel pipe is modeled using Shell163 shell elements; S13, dividing the soil and air in the unit modeling into ALE grids; dividing the rest of the unit modeling into Lagrangian grids, and coupling the ALE grid and the Lagrangian grid using the fluid-structure coupling keyword; S14. Set the soil around and at the bottom as non-reflecting boundary conditions.

3. The safety classification evaluation method for buried steel pipes under rockfall impact according to claim 1 is characterized in that: In step S2, the simulation calculation includes: Set the falling rocks of preset weight to different initial velocities, and simulate different kinetic energies of falling rocks by changing the initial velocities. By changing the horizontal distance between the rockfall and the steel pipe axis, different impact offsets can be obtained. Obtain the maximum ovality and maximum tensile strain of the steel pipe during each impact simulation.

4. The safety classification evaluation method for buried steel pipes under rockfall impact according to claim 1 is characterized in that: The first fitting formula is: ； Where, Δ represents the maximum ovality of the steel pipe, and ε represents the maximum tensile strain of the steel pipe; The second fitting formula is: ； Where E represents the kinetic energy of the rockfall and R represents the impact offset.

5. The safety classification evaluation method for buried steel pipes under rockfall impact according to claim 4 is characterized in that: Establish safety classification indicators for buried steel pipes, including: The ultimate tensile strain of buried steel pipe steel is taken as the first-level index, and the first-level index A1 is expressed as: ； One fifth of the ultimate tensile strain of the buried steel pipe is used as the secondary index, and the secondary index A2 is expressed as: ； Taking the ovality limit of the buried steel pipe as the third-level index, based on the first fitting formula, the third-level index A3 is expressed as: ； Where, is the ultimate tensile strain of the steel pipe, It is the limit value of steel pipe ovality.

6. The safety classification evaluation method for buried steel pipes under rockfall impact according to claim 4 is characterized in that: In step S6, the kinetic energy and impact offset of the rockfall at the site where the actual buried steel pipe is located are obtained, and the steps are as follows: S61. The impact kinetic energy of the rockfall is calculated by measuring the volume of the rockfall and the vertical height difference between the rockfall separation point and the buried steel pipe. The calculation formula is: ； Where m represents the mass of the rockfall, g is the acceleration of gravity, and h is the vertical height difference between the rockfall separation point and the buried steel pipe; S62, by measuring the horizontal distance between the rockfall impact point and the buried steel pipe, the impact offset distance R is obtained; S63. Calculate the maximum tensile strain of the actual buried steel pipe using the second fitting formula.

7. The safety classification evaluation method for buried steel pipes under rockfall impact according to claim 6, characterized in that: In step S7, the safety level of the buried steel pipe is divided into the following categories: When 0 < maximum tensile strain < level 3 index, the safety level corresponding to the buried steel pipe is level 4; When the third-level index < maximum tensile strain < second-level index, the corresponding safety level of the buried steel pipe is the third level; When the secondary index < maximum tensile strain < primary index, the corresponding safety level of the buried steel pipe is the second level; When the first-level index is less than the maximum tensile strain, the corresponding safety level of the buried steel pipe is the first level.

8. A safety grading and evaluation system for buried steel pipes under rockfall impact, used to implement the safety grading and evaluation method for buried steel pipes according to any one of claims 1 to 7, characterized in that: include: Modeling unit, simulation unit, first fitting unit, second fitting unit, establishment unit, calculation unit, evaluation unit: The modeling unit is used to obtain parameter information of the actual buried steel pipe and the site where it is located, and to construct a numerical analysis model based on the parameter information; The simulation unit is used to simulate and calculate the numerical analysis model under different rockfall kinetic energy and different impact offset conditions to obtain the simulation results of each impact; The first fitting unit is used to fit the maximum ovality and the maximum tensile strain under different rockfall kinetic energies and different impact offsets to obtain a first fitting formula; The second fitting unit is used to fit the maximum tensile strain under different rockfall kinetic energies and different impact offsets with the rockfall kinetic energy and impact offset to obtain a second fitting formula; The establishing unit is used to establish safety classification indicators for buried steel pipes; The calculation unit is used to obtain the kinetic energy and impact offset of the rockfall at the actual site where the buried steel pipe is located, and substitute them into the second fitting formula to obtain the maximum tensile strain of the buried steel pipe; The evaluation unit is used to compare the maximum tensile strain of the buried steel pipe with the classification index to obtain the safety level of the buried steel pipe. According to actual engineering requirements, the buried steel pipe route is set based on the corresponding safety level, and the offset between the buried steel pipe and the potential rockfall impact point is greater than the safety offset of the corresponding safety level.

9. The safety grading and evaluation system for buried steel pipes under rockfall impact according to claim 8, characterized in that: The modeling unit includes: a component modeling unit, a division unit and a setting unit; The component modeling unit models the soil and fallen rocks using Solid164 solid units, and models the steel pipe using Shell163 shell units; the partitioning unit divides the soil and air into ALE grids, and the rest into Lagrangian grids, and couples the ALE grid and the Lagrangian grid through the fluid-solid coupling keyword; the setting unit is used to set the surrounding area and bottom of the soil to non-reflecting boundary conditions.

10. The safety grading and evaluation system for buried steel pipes under rockfall impact according to claim 8, characterized in that: The simulation unit includes: a rockfall simulation unit, an impact offset simulation unit and an output unit; The rockfall simulation unit sets different initial velocities for rockfalls of preset weight, and simulates different rockfall kinetic energies by changing the magnitude of the initial velocities; the impact offset simulation unit obtains different impact offsets by changing the horizontal distance from the rockfall to the axis of the steel pipe; and the output unit obtains the maximum ovality and maximum tensile strain of the steel pipe during each impact simulation.

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