Establishment of a safety threshold prediction model for high-density polyethylene pipelines under strong earthquakes

Abstract

The present invention provides a method for establishing a safety threshold prediction model for high-density polyethylene (HDPE) pipelines under strong earthquakes, comprising the following steps: S1: conducting field tests on spigot-and-socket high-density polyethylene (HDPE) corrugated pipelines under strong earthquakes to obtain field test data; S2: using the test data, fitting a mathematical prediction model for the interface angle; S3: calculating the vibration velocity safety threshold of the buried HDPE pipeline under strong earthquake loads based on current polyethylene pipeline construction specifications; and S4: establishing a finite element model to verify the mathematical prediction model for the interface angle obtained in step S2. The present invention has the following beneficial effects: the method can solve the problem in the prior art of the difficulty in effectively assessing the hazards of buried spigot-and-socket high-density polyethylene (HDPE) drainage pipelines in cities under strong earthquake loads, and provide a scientific and reasonable basis for judgment in the design and construction of blasting projects, earthquake structural protection projects, and buried spigot-and-socket high-density polyethylene (HDPE) drainage pipeline installation projects.

Description

Technical Field

[0001] The present invention relates to the technical field of pipeline engineering and blasting engineering, and in particular to a method for establishing a safety threshold prediction model for high-density polyethylene pipelines under strong earthquake action. Background Art

[0002] Large-diameter, directly buried high-density polyethylene corrugated pipes are an important component of urban drainage systems and the "vascular network" on which cities depend for survival. Due to their excellent corrosion and impact resistance, HDPE corrugated pipes are mostly buried in shallow soil layers in urban areas. Due to the limited length of a single section of pipeline, and the limitations of transportation conditions and manufacturing processes, during the process of burying and installing pipelines, pipe connections are mostly made in the form of socket joints. However, this comes with the fact that during pipeline operation, they are susceptible to external loads, causing joints or pipe bodies to fail, resulting in seepage and exhaust, which may lead to corrosion around the pipeline, collapse of surrounding roads, traffic jams, damage to ground structures, groundwater pollution and other adverse consequences.

[0003] With the rapid development of infrastructure projects in my country, the demand for urban underground space projects is growing. Urban areas have complex geological environments, and underground space projects often need to be constructed in hard rock formations. Blasting, as a key method for hard rock excavation, is widely used due to its efficiency and cost-effectiveness. However, blasting excavation can produce a variety of harmful effects, such as flying rocks, harmful gases, and blasting vibration, with blasting vibration having the greatest impact. During normal pipeline operation, the intense vibration loads generated by blasting can cause pipeline deformation. When the deformation exceeds the allowable value, the pipeline will fail. Furthermore, my country is a vast country with multiple seismic zones scattered throughout its territory. The seismic waves generated by earthquakes also have a significant impact on the safe operation of pipelines.

[0004] In existing research, the safety characteristics of pipelines under strong seismic loads mainly focus on the study of gas pipelines made of ductile iron, steel, polyethylene and other materials. In terms of pipeline structure, the research is mostly aimed at directly buried single-section pipelines; and the research on the pipeline response characteristics under strong seismic loads is only focused on the dynamic response characteristics of the pipeline, and there is little research on the pipeline safety control threshold. In summary, it can be seen that previous related research is difficult to provide effective reference.

[0005] In summary, there is no unified approach in the existing technology for the research on the vibration velocity safety threshold of socket-type high-density polyethylene pipes under strong earthquakes, which makes it difficult to provide a scientific and reasonable basis for blasting engineering construction and earthquake protection. Summary of the Invention

[0006] In view of this, the present invention provides a method for establishing a safety threshold prediction model for high-density polyethylene pipelines under strong earthquakes, the method comprising the following steps:

[0007] S1: Using explosives to simulate strong earthquake loads, conduct field tests on socket-and-spigot high-density polyethylene corrugated pipes under strong earthquake loads and obtain field test data;

[0008] S2: Using the test data obtained in step S1 and combining it with the dimensional analysis method, a mathematical prediction model of the interface angle is obtained by fitting;

[0009] The specific process of step S2 is as follows:

[0010] Using the dimensionless analysis method, the physical relationship of pipeline vibration velocity is established:

[0011] (1)

[0012] Where vp is the pipeline vibration velocity, Q is the maximum single-section charge, R is the blasting distance, D is the pipeline diameter, L is the length of a single section of the HDPE pipe, ρ is the HDPE pipe density, and c is the wave propagation velocity in the medium;

[0013] According to the dimensional homogeneity theorem, Q, R, and c are selected as dimensionally independent quantities, and other parameters are dimensionally dependent quantities. The dimensionless number can be obtained as follows:

[0014]

[0015] Considering ρ and c as constants, let

[0016]

[0017] Then the above formula (1) can be expressed as:

[0018] (2)

[0019] Where K is a constant;

[0020] According to the pipeline structure, the calculation formula of the pipeline interface angle can be obtained

[0021]

[0022] Where: θ is the interface angle, ∆h is the relative displacement between the spigot pipe interface and the tail, and L is the length of a single pipe segment;

[0023] The pipeline vibration velocity data is fitted with the surface data directly above, and the

[0024] (4)

[0025] Where: vp is the pipeline vibration velocity, vg is the surface vibration velocity;

[0026] The pipeline vibration velocity and pipeline interface displacement are fitted with formulas to obtain

[0027] (5)

[0028] Substitute the fitting formulas (4) and (5) into the angle calculation formula (3) to obtain the mathematical prediction model of the interface angle.

[0029]

[0030] Among them, K2, K1, a, b, c, and d are all constants obtained by fitting;

[0031] S3: Calculate the vibration velocity safety threshold of the buried high-density polyethylene pipeline under strong seismic load based on the current polyethylene pipeline construction specifications and the pipeline interface angle as a judgment basis according to the mathematical prediction model obtained in step S2;

[0032] S4: Establishing a finite element model, using the finite element model to verify the vibration velocity safety threshold of the buried high-density polyethylene pipeline obtained in step S3, and determining whether the mathematical prediction model of the interface angle obtained in step S2 is reasonable;

[0033] If it is reasonable, a reliable mathematical prediction model of the interface angle can be obtained;

[0034] If it is unreasonable, return to step S2 and repeat steps S2-S5 until a reliable mathematical prediction model of the interface angle is obtained.

[0035] Furthermore, the process of step S1 is as follows:

[0036] S101: Select a test site; dig a trench at the test site, select and assemble multiple sections of high-density polyethylene corrugated pipes as research objects; arrange sensors, backfill the soil, and compact it;

[0037] S102, drilling a blasting hole; burying explosives and detonating them, and using the above-mentioned sensors to collect field test data.

[0038] Furthermore, the sensors in step S1 include a pipe vibration velocity sensor, a displacement sensor, a stress and strain sensor, and a soil vibration velocity sensor.

[0039] Furthermore, the pipe body vibration velocity sensor is located inside the high-density polyethylene pipe and is used to monitor the vibration velocity of the high-density polyethylene pipe; the displacement sensor is located at the interface of the high-density polyethylene pipe and is used to monitor the relative displacement generated between the socket and the plug of the high-density polyethylene pipe; the stress and strain sensors are arranged at fixed distances along the cross-section of the high-density polyethylene pipe body and are used to monitor the stress and strain of the high-density polyethylene pipe; the soil vibration velocity sensor is located on the soil square of the high-density polyethylene pipe and is used to monitor the vibration velocity of the soil.

[0040] Furthermore, in step S4, a finite element model is established, and the vibration velocity safety threshold of the buried high-density polyethylene pipeline obtained in step S3 is verified using the finite element model. The method for determining whether the mathematical prediction model of the interface angle obtained in step S2 is reasonable specifically includes the following steps:

[0041] S401: Based on the working conditions of the field test in step S1, a finite element numerical model with a spatial position relationship consistent with the working conditions of the field test is established, and a simulation numerical result is obtained using the finite element numerical model;

[0042] S402: Comparing the simulation numerical results with the field test results. If the error between the simulation numerical results and the field test results is within the allowable error range, it is indicated that the finite element numerical model is valid; otherwise, repeat step S401 until a valid finite element numerical model is obtained.

[0043] S403: Based on the effective finite element numerical model obtained in step S402, gradually increase the amount of explosives in the finite element numerical model and increase the magnitude of the strong earthquake load until a simulated vibration velocity safety threshold is obtained through simulation of the finite element numerical model, and compare the simulated vibration velocity safety threshold with the vibration velocity safety threshold calculated by the mathematical prediction model in step S3; if the error is within the allowable error range of 10%, the mathematical prediction model in step S2 is reasonable, otherwise the mathematical prediction model in step S2 is unreasonable.

[0044] Furthermore, the allowable error in step S402 and step S403 is 10%.

[0045] Compared with the prior art, the present invention has the following advantages and beneficial effects:

[0046] The present invention provides a method for establishing a prediction model for the safety threshold of high-density polyethylene (HDPE) pipelines under strong earthquakes. The method obtains test data for the safety threshold of HDPE pipelines under strong earthquakes through field tests, and establishes a mathematical prediction model for predicting the angle of HDPE pipeline interfaces based on the test data, thereby predicting the safety threshold of HDPE pipelines. The method solves the technical problem in the prior art that research on the vibration velocity safety threshold of socket-type HDPE pipelines under strong earthquakes is difficult to provide a scientific and reasonable basis for blasting engineering construction and earthquake protection. The method thus provides an effective theoretical basis for solving safety protection issues in buried pipeline projects and guiding the development of technologies such as earthquake disaster prevention. Furthermore, after establishing the mathematical prediction model for the angle of HDPE pipeline interfaces, the method also verifies the mathematical prediction model using a finite element numerical model, ensuring the reliability of the mathematical prediction model and the accuracy of the HDPE pipeline safety threshold predicted by the mathematical prediction model, thereby improving the engineering safety of HDPE pipeline design and construction. BRIEF DESCRIPTION OF THE DRAWINGS

[0047] Figure 1 This is a flow chart of a method for establishing a safety threshold prediction model for high-density polyethylene pipelines under strong earthquakes according to an embodiment of the present invention;

[0048] Figure 2 This is a diagram showing the relationship between the positions of the socket-type high-density polyethylene corrugated pipes under strong earthquakes and a method for establishing a safety threshold prediction model for high-density polyethylene pipes under strong earthquakes according to an embodiment of the present invention.

[0049] In the figure, 1-groove, 2-high-density polyethylene corrugated pipe, 3-blasting hole, 4-explosive. DETAILED DESCRIPTION

[0050] To make the objectives, technical solutions and advantages of the present invention more clear, the embodiments of the present invention will be further described below with reference to the accompanying drawings.

[0051] The present invention provides a method for establishing a safety threshold prediction model for high-density polyethylene pipelines under strong earthquakes, so as to solve the problem in the prior art that it is difficult to effectively evaluate the hazards of urban buried socket-and-spigot high-density polyethylene drainage pipelines under strong earthquake loads, thereby achieving the purpose of providing an effective reference for blasting engineering construction and earthquake structure protection, and providing a scientific and reasonable judgment basis for the protection of buried socket-and-spigot high-density polyethylene drainage pipelines.

[0052] Please refer to Figure 1 and Figure 2 The present invention provides a method for establishing a safety threshold prediction model for high-density polyethylene pipelines under strong earthquakes, comprising the following steps:

[0053] S1: Using explosives to simulate strong earthquake loads, conduct field tests on socket-and-spigot high-density polyethylene corrugated pipes under strong earthquake loads and obtain field test data;

[0054] Specifically, the process of step S1 is as follows:

[0055] S101: Select an area with typical urban stratum characteristics as the research site. Use an excavator to excavate a trench 1 in the pre-selected site. Select a multi-section PE100-grade high-density polyethylene (HDPE) corrugated pipe 2 as the primary research object. Assemble the HDPE corrugated pipe 2 using a socket-and-spigot joint. Arrange sensors, bury the HDPE corrugated pipe 2 in the trench bottom 1, and backfill the soil. Compact the backfill using a roller and compactor.

[0056] S102, drilling a blasting hole 3; burying explosives 4 and detonating them, and using the above-mentioned sensors to collect field test data.

[0057] The sensors in step S101 include a pipe vibration velocity sensor, a displacement sensor, a stress and strain sensor, and a soil vibration velocity sensor.

[0058] The pipe body vibration velocity sensor is located inside the high-density polyethylene pipe 2 and is used to monitor the pipeline vibration velocity v p The displacement sensor is located at the interface of the high-density polyethylene pipe and is used to monitor the relative displacement ∆h between the (high-density polyethylene pipe) spigot pipe interface and the tail. The stress and strain sensors are set at fixed distances along the cross-section of the high-density polyethylene pipe and are used to monitor the stress and strain of the high-density polyethylene pipe. The soil vibration velocity sensor is located on the soil in the square of the high-density polyethylene pipe and is used to monitor the surface vibration velocity v of the soil. g .

[0059] During the above-mentioned sensor arrangement process, the pipe body vibration velocity sensor, displacement sensor, and stress strain sensor are first arranged and buried in the trench 1 along with the pipe body. After the backfill is completed, the density of the backfill soil is tested using a density measuring device. When the density requirement meets the specification standard, the soil vibration velocity sensor is arranged on the surface directly above the pipeline.

[0060] In step S102, different distances from the blast center (m) and explosive quantities (kg) are used to simulate the strength of different strong earthquake loads. A hydraulic drilling rig is used to drill holes and explosives are buried in the rock stratum for blasting. The explosives are detonated and the above-mentioned sensors are used to obtain field test data.

[0061] Specifically, 12kg of 2# rock emulsion explosives are buried every 5 meters on the vertical plane from the pipeline axis. The bottom of the explosives is 8m from the ground surface, and the burial depth is selected to be 5m. The detonating detonator and detonating cord are led out of the ground and connected to the detonating equipment.

[0062] It is particularly important to note that before blasting, the data acquisition instrument must be debugged and channel parameters must be set; strain and displacement data must be collected before detonating the detonator; and when the pipeline and surrounding rock and soil are stable, collection must be stopped and the data saved.

[0063] S2: Using the test data obtained in step S1 and combining it with the dimensional analysis method, a mathematical prediction model of the interface angle is obtained by fitting. The specific process is as follows:

[0064] Using the dimensionless analysis method, the physical relationship of pipeline vibration velocity is established:

[0065] (1)

[0066] The meanings, units, and dimensions of the above physical quantities are shown in the following table

[0067]

[0068] Note: L—dimension of length; T—dimension of time; M—dimension of mass.

[0069] According to the dimensional homogeneity theorem, Q, R, and c are selected as dimensionally independent quantities, and other parameters are dimensionally dependent quantities. The dimensionless number can be obtained as follows:

[0070]

[0071] According to the actual project, when the project site conditions are constant, the density and propagation speed can be approximately regarded as constants. Therefore, ρ and c are regarded as constants here.

[0072] (1)

[0073] Then the above formula (1) can be expressed as:

[0074] (2)

[0075] Where K is a constant;

[0076] According to the pipeline structure, the calculation formula of the pipeline interface angle can be obtained

[0077]

[0078] Where: θ is the interface angle, ∆h is the relative displacement between the spigot pipe interface and the tail, and L is the length of a single pipe segment;

[0079] The pipeline vibration velocity vp and the surface vibration velocity vg are fitted to obtain

[0080] (4)

[0081] Where: v p is the pipeline vibration velocity, v g is the surface vibration velocity.

[0082] Pipeline vibration velocity v p The formula is fitted with the relative displacement ∆h between the spigot pipe interface and the tail, and the result is

[0083] (5)

[0084] Substitute the fitting formulas (4) and (5) into the angle calculation formula (3) to obtain the mathematical prediction model of the interface angle.

[0085] (6)

[0086] Among them, K2, K1, a, b, c, and d are all constants obtained by fitting.

[0087] In this embodiment, the results obtained by fitting the actual field test data are as follows:

[0088] (7)

[0089] S3: Calculate the vibration velocity safety threshold of the buried high-density polyethylene pipeline under strong seismic load based on the current polyethylene pipeline construction specifications and the pipeline interface angle as a judgment basis according to the mathematical prediction model obtained in step S2;

[0090] Specifically: By looking up the relevant specifications (DBJ52T 039-2017) and the pipe production manual, it is found that the allowable interface angle of HDPE corrugated pipes is 2°. Substituting it into the vibration velocity angle prediction formula (7), under this working condition, when the allowable pipe interface angle reaches 2°, the vibration velocity safety threshold of the socket-type HDPE corrugated pipe under strong seismic load is 21.1 cm / s.

[0091] S4: Establishing a finite element model, using the finite element model to verify the vibration velocity safety threshold of the buried high-density polyethylene pipeline obtained in step S3, and determining whether the mathematical prediction model of the interface angle obtained in step S2 is reasonable;

[0092] If it is reasonable, a reliable mathematical prediction model of the interface angle can be obtained;

[0093] If it is unreasonable, return to step S2 and repeat steps S2-S4 until a reliable mathematical prediction model of the interface angle is obtained.

[0094] Specifically, in step S4, the finite element model is used to verify the vibration velocity safety threshold of the buried high-density polyethylene pipeline obtained in step S3, and the process of judging whether the mathematical prediction model of the interface angle obtained in step S2 is reasonable is as follows;

[0095] S401: Based on the working conditions of the field test in step S1, a finite element numerical model with a spatial position relationship consistent with the working conditions of the field test is established, and a numerical simulation is performed using the finite element numerical model;

[0096] S402: Comparing the numerical simulation results with the field test results. If the error between the numerical simulation results and the field test results is within the allowable error range, it is considered that the finite element numerical model is valid; otherwise, repeat step S401 until a valid finite element numerical model is obtained.

[0097] S403: On the basis of the effective finite element numerical model obtained in step S402, gradually increase the amount of explosives in the finite element numerical model and increase the magnitude of the strong earthquake load until a simulated vibration velocity safety threshold is obtained through simulation of the finite element numerical model, and compare the simulated vibration velocity safety threshold with the vibration velocity safety threshold (i.e., 21.1 cm / s) calculated by the mathematical prediction model in step S3; if the error is within the allowable error range, the vibration velocity safety threshold in step S3 is reasonable, and the mathematical prediction model of the interface angle obtained in step S2 is also reasonable; otherwise, both the vibration velocity safety threshold in S3 and the mathematical prediction model of the interface angle obtained in step S2 are unreasonable.

[0098] The allowable error in the above steps S4401 and S403 is 10%.

[0099] It should be noted that in step S1, the field test data including the pipeline vibration velocity of the high-density polyethylene pipe is obtained. v p , relative displacement between the spigot pipe interface and the tail ∆h, surface vibration velocity v g , stress and strain of high-density polyethylene pipe. v p ,∆h,v g The mathematical prediction model for fitting the interface angle, the stress and strain of the high-density polyethylene pipe, are used as the field working condition parameters when establishing the finite element model in step S4.

[0100] In this document, directional terms such as front, back, top, and bottom are defined based on the positions of components in the accompanying drawings and relative to each other, and are intended only for clarity and convenience in describing the technical solution. It should be understood that the use of these directional terms should not limit the scope of protection claimed in this application.

[0101] In the absence of conflict, the above embodiments and features in the embodiments may be combined with each other.

[0102] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. A method for establishing a safety threshold prediction model for high-density polyethylene pipelines under strong earthquakes, characterized by: The method comprises the following steps: S1: Using explosives to simulate strong earthquake loads, conduct field tests on socket-and-spigot high-density polyethylene corrugated pipes under strong earthquake loads and obtain field test data; S2: Using the test data obtained in step S1 and combining it with the dimensional analysis method, a mathematical prediction model of the interface angle is obtained by fitting; The specific process of step S2 is as follows: Using the dimensionless analysis method, the physical relationship of pipeline vibration velocity is established: （1） in is the pipeline vibration velocity, Q is the maximum single-section charge, R is the blasting distance, D is the pipeline diameter, L is the length of a single section of the HDPE pipe, ρ is the HDPE pipe density, and c is the wave propagation velocity in the medium; According to the dimensional homogeneity theorem, Q, R, and c are selected as dimensionally independent quantities, and other parameters are dimensionally dependent quantities. The dimensionless number can be obtained as follows: Considering ρ and c as constants, let 、 are the exponents of the corresponding terms in the formula respectively; Then the above formula (1) can be expressed as: （2） Where K is a constant, 、 、 、 The exponents of the corresponding terms of the formula respectively; According to the pipeline structure, the calculation formula of the pipeline interface angle can be obtained Where: θ is the interface angle, ∆h is the relative displacement between the spigot pipe interface and the tail, and L is the length of a single pipe segment; The pipeline vibration velocity data is fitted with the surface data directly above, and the （4） Where: Pipeline vibration velocity, Surface vibration velocity; The pipeline vibration velocity and pipeline interface displacement are fitted with formulas to obtain （5） Substitute the fitting formulas (4) and (5) into the angle calculation formula (3) to obtain the mathematical prediction model of the interface angle. （6） in 、 , a, b, c, and d are all constants obtained by fitting; S3: Based on the current polyethylene pipeline construction specifications, taking the pipeline interface angle as the judgment basis, and according to the mathematical prediction model obtained in step S2, calculating the vibration velocity safety threshold of the buried high-density polyethylene pipeline under strong seismic load; S4: Establishing a finite element model, using the finite element model to verify the vibration velocity safety threshold of the buried high-density polyethylene pipeline obtained in step S3, and determining whether the mathematical prediction model of the interface angle obtained in step S2 is reasonable; If it is reasonable, a reliable mathematical prediction model of the interface angle can be obtained; If it is unreasonable, return to step S2 and repeat steps S2-S5 until a reliable mathematical prediction model of the interface angle is obtained.

2. The method for establishing a safety threshold prediction model for high-density polyethylene pipelines under strong earthquakes according to claim 1, characterized in that: The specific process of step S1 is as follows: S101: Select a test site; dig a trench at the test site, select and assemble multiple sections of high-density polyethylene corrugated pipes as research objects; arrange sensors, backfill the soil, and compact it; S102, drilling a blasting hole; burying explosives and detonating them, and using the above-mentioned sensors to collect field test data.

3. The method for establishing a safety threshold prediction model for high-density polyethylene pipelines under strong earthquakes according to claim 2, characterized in that: The sensors in step S1 include a pipe vibration velocity sensor, a displacement sensor, a stress and strain sensor, and a soil vibration velocity sensor.

4. The method for establishing a safety threshold prediction model for high-density polyethylene pipelines under strong earthquakes according to claim 3, characterized in that: The pipe body vibration velocity sensor is located inside the high-density polyethylene pipe and is used to monitor the vibration velocity of the high-density polyethylene pipe; the displacement sensor is located at the interface of the high-density polyethylene pipe and is used to monitor the relative displacement between the socket and the plug of the high-density polyethylene pipe; the stress and strain sensors are arranged at fixed distances along the cross-section of the high-density polyethylene pipe body and are used to monitor the stress and strain of the high-density polyethylene pipe. The soil vibration velocity sensor is located on the soil square of the high-density polyethylene pipe and is used to monitor the vibration velocity of the soil.

5. The method for establishing a safety threshold prediction model for high-density polyethylene pipelines under strong earthquakes according to claim 1, characterized in that: In step S4, a finite element model is established, and the vibration velocity safety threshold of the buried high-density polyethylene pipeline obtained in step S3 is verified using the finite element model. The method for determining whether the mathematical prediction model of the interface angle obtained in step S2 is reasonable specifically includes the following steps: S401: Based on the working conditions of the field test in step S1, a finite element numerical model with a spatial position relationship consistent with the working conditions of the field test is established, and a simulation numerical result is obtained using the finite element numerical model; S402: comparing the simulation numerical results with the field test results. If the error between the simulation numerical results and the field test results is within the allowable error range, it indicates that the finite element numerical model is valid. Otherwise, repeat step S401 until a valid finite element numerical model is obtained; S403: Based on the effective finite element numerical model obtained in step S402, gradually increase the amount of explosives in the finite element numerical model and increase the magnitude of the strong earthquake load until a simulated vibration velocity safety threshold is obtained through simulation of the finite element numerical model, and compare the simulated vibration velocity safety threshold with the vibration velocity safety threshold calculated by the mathematical prediction model in step S3; if the error is within the allowable error range of 10%, the mathematical prediction model in step S2 is reasonable, otherwise the mathematical prediction model in step S2 is unreasonable.

6. The method for establishing a safety threshold prediction model for high-density polyethylene pipelines under strong earthquakes according to claim 5, characterized in that: The permissible error in step S402 and step S403 is 10%.

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