Design method and system for ground concrete cushion parameters of buried pipeline protection based on rockfall influence

Abstract

The application discloses a method and system for designing parameters of a ground surface concrete cushion layer for protecting a buried pipeline based on rockfall influence, and the method comprises the following steps: constructing a rockfall impact model, a buried pipeline model and a cushion layer model; collecting strain data and velocity of rockfall, variation of earth pressure in an undisturbed soil layer and strain of the buried pipeline model by using a data testing device; analyzing the collected data, and retaining data not exceeding a preset safety range; changing parameters of the cushion layer model by using a control variable method, and keeping other model parameters unchanged until analysis of all parameters of the cushion layer model is completed, and then stopping; further analyzing the retained data to obtain a relationship between strain and the parameters of the cushion layer model, and completing parameter design of the buried pipeline. The application effectively simulates the protection effect of the concrete cushion layer on the buried pipeline under rockfall impact, is closer to an actual engineering, and provides a reference value for the actual engineering.

Description

Technical Field

[0001] This invention relates to the fields of pipeline technology and disaster control technology, specifically to a method and system for designing parameters of the surface concrete cushion layer for buried pipeline protection based on the impact of falling rocks. Background Technology

[0002] Concrete pipes are widely used due to their low cost, ease of construction, excellent corrosion resistance, and good sealing performance. Buried pipelines, as a primary method of pipeline system installation, offer advantages such as relatively convenient construction and no need to occupy ground space; however, unexpected ground impacts can severely affect the stability and operational safety of buried pipelines.

[0003] Currently, protective measures can be divided into two main types: active protection and passive protection. Active protection focuses on preventing rockfall disasters, including supporting and sealing unstable rock masses, and deploying active protective nets. Passive protection focuses on protection after a rockfall has occurred, including setting up retaining walls and rockfall nets to intercept falling rocks. Li Qiaozhen et al., based on explicit dynamic analysis methods, established a three-dimensional dual nonlinear dynamic response analysis model for buried pipelines impacted by spherical falling objects, and explored the variation law of pipeline dynamic response with different influencing factors. Wang Dongyuan et al. studied the load reduction and energy consumption buffering problems of shallowly buried oil and gas pipelines under the impact of landslides and falling rocks, simulating the energy consumption and vibration isolation effect of polystyrene foam plastic cushions with different thicknesses and initial densities using the finite element dynamics software ANSYS / LS-DYNA. Wu Jianli et al. studied the impact force attenuation law and failure mode of reinforced concrete slabs combined with soil particle buffer layers of a certain thickness under rockfall action, and conducted a series of outdoor rockfall impact tests.

[0004] Most studies on buried pipelines impacted by falling rocks tend to treat the pipeline as a single, rigid structure, neglecting the connections between pipes when discussing the pipeline's dynamic response. This is actually a simplification. However, in actual engineering projects, both ballistic cast iron pipelines and concrete water pipelines use flange connections or rubber ring connections. Summary of the Invention

[0005] The purpose of this invention is to provide a method and system for designing parameters of the surface concrete cushion layer for buried pipeline protection based on the impact of falling rocks. This method can achieve the principle of controlling a single variable, solve the problem of operational difficulty in simulating the impact dynamic load of falling rocks, and objectively reflect the protective effect of the concrete cushion layer on the buried pipeline under the action of falling rock impact dynamic load, thus providing a basis for the safety evaluation of buried pipeline protection.

[0006] To solve the above technical problems, the present invention adopts the following technical solution:

[0007] The design method for the surface concrete cushion layer parameters of buried pipeline protection based on the impact of falling rocks includes the following steps:

[0008] S1. Determine the parameters for rockfall, pipeline, soil, and concrete cushion layer.

[0009] S2. Construct a rockfall impact model, a buried pipeline model, and a subgrade model. Place the buried pipeline model in a trench filled with undisturbed soil, place the subgrade model above the buried pipeline model, and place the rockfall impact model above the subgrade model.

[0010] S3. Use data testing equipment to collect strain data and velocity of falling rocks, changes in earth pressure in undisturbed soil layers, and strain of buried pipeline models.

[0011] S4. Analyze the data collected in step S3. If the analysis results exceed the preset safety range, the control system will automatically activate the emergency plan; otherwise, the data will be retained.

[0012] S5. Using the controlled variable method, change the parameters of the cushion layer model while keeping other model parameters unchanged. Repeat steps S3-S4 until all parameters of the cushion layer model have been analyzed, then stop.

[0013] S6. Further analyze the retained data to obtain the relationship between strain and the parameters of the subbase model, and complete the parameter design of the buried pipeline.

[0014] Furthermore, in step S1, determining the experimental parameters includes the following:

[0015] Based on the first and second similarity theory criteria, the parameters are designed, and the geometric similarity ratio of the layout is determined to be L=1. The cross-sectional dimensions and burial depth are designed according to the prototype dimensions at a 1:1 ratio. The similarity ratios of gravity acceleration, unit weight, and density are Cg=1, Cγ=1, and Cr=1. Based on the similarity ratios of geometric and unit weight, the Poisson's ratio and friction angle are fully similar. The elastic modulus is designed according to the similarity ratio of the prototype soil elastic modulus of 1.

[0016] Rockfall parameters include shape, mass, angle, and release height; pipe parameters include material, diameter, wall thickness, and burial depth; and soil parameters include soil type, moisture content, and compaction degree.

[0017] Furthermore, in step S2, the model construction includes the following:

[0018] A rockfall impact model was constructed using cast-in-place concrete spheres, a buried pipeline model was obtained by splicing four sections of concrete pipes together with tongue and groove joints, and a subbase model was obtained by concrete pouring.

[0019] A trench is dug using an excavator, the buried pipeline model is placed in the trench, and then the excavator is used to backfill it with the original soil on site. During backfilling, one side of the buried pipeline model is completely buried, and the other side is sloped.

[0020] Furthermore, in step S3, the collected data includes the following:

[0021] The data testing equipment includes strain bricks, soil pressure gauges, strain gauges, and high-speed cameras.

[0022] A crane is used to lift the falling rocks to a high altitude and place them stationary. After the data testing device is activated, the rock is allowed to fall to a fixed point after the release command is received.

[0023] When a rockfall impacts the model, strain gauges fixed inside the steel cage collect rockfall strain data, strain gauges attached to the inner wall of the buried pipeline model collect dynamic strain of the pipeline, earth pressure gauges set at a set distance above the centerline of the buried pipeline model collect earth pressure change characteristics, and high-speed cameras set next to the impact point record images of the rockfall after it is released from the air, thereby obtaining the velocity of the rockfall impact; the impact point is set at the center of the concrete cushion layer.

[0024] Furthermore, epoxy resin was used to fabricate strain bricks.

[0025] The strain gauges include circumferential strain gauges and axial strain gauges. Five strain gauge monitoring sections are set on the inner wall of the buried pipeline model. These sections are located at the top, waist, and bottom of two sections directly below the impact point and one meter along the axis, as well as the top of a section located 3 meters to the left and right of the impact point along the axis.

[0026] Furthermore, in step S4, the data analysis includes the following:

[0027] The strain gauge is connected to the dynamic signal testing and analysis system via a quarter-bridge circuit. The acquired dynamic strain is plotted into a strain-time history curve at the corresponding pipe cross-section using software. Based on this curve, it is analyzed whether the strain value exceeds the ultimate tensile strain value corresponding to the unstable propagation of cracks in the concrete pipe.

[0028] The earth pressure gauge is connected to the dynamic signal testing and analysis system via a full bridge. The product of the collected earth pressure variation characteristics and the constant coefficient K is plotted as an earth pressure time history curve. The trend of earth pressure variation is analyzed based on this curve.

[0029] Images acquired by a high-speed camera are input into an image analysis system. Based on the height of the falling rock at different times, the trajectory of the impacting object and its ground contact velocity are obtained.

[0030] The emergency plan includes suspending the test, adjusting the rockfall parameters, and rearranging the data testing equipment.

[0031] Furthermore, in step S5, the parameters of the cushion layer model include the thickness of the cushion layer and the concrete strength.

[0032] Furthermore, in step S6, the parameter design of the buried pipeline includes the following:

[0033] By changing the parameters of the subbase model, the protective effect on the pipeline under different rockfall impacts was obtained.

[0034] By setting the ultimate tensile strain of the concrete pipe as a safety threshold, the relationship between the peak tensile strain of the pipe and the thickness of the subbase is obtained, as follows:

[0035]

[0036] Where, ε p denoted as peak tensile strain, h as thickness of the cushion layer, and A, B, and k as correlation coefficients.

[0037] The relationship between the peak tensile strain of the pipeline and the concrete strength of the subbase is as follows:

[0038]

[0039] Where C represents the concrete strength grade.

[0040] Furthermore, this invention also proposes a parameter design system for the surface concrete cushion layer of buried pipeline protection based on the impact of falling rocks, including:

[0041] The data preparation module is used to determine the rockfall parameters, pipe parameters, soil parameters, and different concrete cushion layer parameters required for the experiment.

[0042] The test model construction module is used to construct the rockfall impact model, the buried pipeline model, and the cushion layer model. The buried pipeline model is placed in a trench filled with undisturbed soil, the cushion layer model is placed on top of the buried pipeline model, and the rockfall impact model is placed on top of the cushion layer model.

[0043] The data acquisition module is used to collect data on rockfall strain and velocity in the simulated rockfall impact model, changes in soil pressure in the undisturbed soil layer, and strain in the buried pipeline model using a data testing device.

[0044] The data analysis module is used to analyze the data collected by the data acquisition module. If the analysis results exceed the preset safety range, the control system will automatically activate the emergency plan; otherwise, the data will be retained.

[0045] The experimental module is used to change the parameters of the subgrade model using the controlled variable method, while keeping other model parameters constant, and repeat the steps of data acquisition and data analysis until all parameters of the subgrade model have been analyzed, at which point the process stops.

[0046] The parameter design module is used to further analyze the retained data, obtain the relationship between strain and subbase thickness, and complete the parameter design of the buried pipeline.

[0047] Compared with the prior art, the present invention, employing the above technical solution, has the following technical effects:

[0048] 1. This invention establishes a corresponding field test model by determining a reasonable similarity scale, simplifying and analyzing the prototype test of concrete cushion layers for buried pipelines impacted by falling rocks, thus achieving adaptability to different engineering realities. By simulating the processes of falling rock impact, pipeline burial depth, and cushion layer protection, it effectively simulates the protective effect of concrete cushion layers on buried pipelines under falling rock impact, making it closer to actual engineering and providing reference value for practical engineering.

[0049] 2. This invention uses a reinforced concrete sphere to simulate the impact of falling rocks and changes the thickness of the concrete cushion layer to simulate the protective effect on buried pipelines in actual engineering. The device is simple and has a certain degree of reliability. It can accurately control the magnitude of dynamic load and basically realize the principle of controlling a single variable in the experiment.

[0050] 3. This invention, through a measurement system, can simulate the strain of buried pipelines caused by falling rocks on a concrete cushion layer, as well as the changes in soil pressure in the clay layer, providing experimental basis and research methods for further revealing the protective effect of different thicknesses of concrete cushion layers on buried pipelines. Attached Figure Description

[0051] Figure 1 This is an overall structural diagram of the present invention.

[0052] Figure 2 This is a schematic diagram of the strain gauge bonding position of the present invention.

[0053] Figure 3 This is a front view of the concrete cushion layer of the present invention and a schematic diagram showing the location of the impact point.

[0054] Figure 4 This is a curve showing the relationship between strain and cushion layer thickness in an embodiment of the present invention.

[0055] Figure 5 This is a curve showing the relationship between strain and concrete strength in an embodiment of the present invention.

[0056] Figure labels: 1-rock impact model, 2-substrate model, 3-clay layer, 4-concrete pipe, 5-earth pressure gauge, 6-strain gauge, 7-impact point. Detailed Implementation

[0057] The present invention will be further described below with reference to the accompanying drawings. The following embodiments are only used to more clearly illustrate the technical solution of the present invention, and should not be used to limit the scope of protection of the present invention.

[0058] To achieve the above objectives, this invention proposes a method for designing the parameters of the surface concrete cushion layer for buried pipeline protection based on the impact of falling rocks. The model test site was selected as a field experimental base of a university in Jiangxia District, Wuhan City. Small balls were used to simulate falling rocks. After drilling and sampling the soil layer at the site, the samples were sent to a professional testing company for geotechnical testing. The specific steps are as follows:

[0059] S1. Test Preparation Stage: Based on the actual engineering conditions and research objectives, determine the required parameters for rockfall, pipeline, soil, and different concrete subbase layers; specific details include:

[0060] Based on the first and second similarity theory criteria, the parameters were designed, and the geometric similarity ratio of the layout geometry was determined to be L=1. The model test adopted a large-scale field test. The cross-sectional dimensions and burial depth were designed according to the prototype dimensions at a ratio of 1:1. The similarity ratios of gravity acceleration Cg=1, unit weight Cγ=1, and density Cr=1 were based on the geometric similarity ratio and unit weight similarity ratio to achieve full similarity of Poisson's ratio and friction angle. The elastic modulus was designed according to the similarity ratio of the prototype soil elastic modulus of 1.

[0061] Rockfall parameters include shape, mass, angle, and release height; pipe parameters include material, diameter, wall thickness, and burial depth; and soil parameters include soil type, moisture content, and compaction degree.

[0062] S2. Constructing on-site test models: Build a rockfall impact model 1, a buried pipeline model, and a subgrade model 2; place the buried pipeline model in a trench filled with undisturbed soil, place subgrade model 2 on top of the buried pipeline model, and place rockfall impact model 1 on top of subgrade model 2; Figure 1 As shown, the specific content is as follows:

[0063] A rockfall impact model 1 was constructed using cast-in-place concrete spheres. Under the premise of thorough research and investigation, in order to ensure that the test results of the model are consistent with the engineering conditions of the subway tunnel, four precast concrete pipes 4 were spliced ​​together using tongue and groove joints to ensure that the pipes conform to general water supply pipes, thus obtaining a buried pipe model. The concrete pipes 4 are connected by flexible joints. A subbase model 2 was obtained by concrete pouring.

[0064] A trench was dug using an excavator, without pressurizing the inside of the pipe. The backfill soil at the bottom of the pipe and the soil covering the pipe were compacted in layers, and the compaction degree met the requirements of the construction and acceptance standards and specifications for water supply and drainage pipeline projects. The constraint conditions at both ends of the pipe can be regarded as the same as those of actual buried pipelines. The buried pipeline model was placed in the trench, and then the excavator was used to backfill it with the original soil on site. During backfilling, the compaction degree of the backfill soil must be ensured to ensure that the soil covering the tunnel is in close contact with the tunnel and that the compaction degree is stable. To facilitate the subsequent placement of strain gauges, one side of the buried pipeline model was completely buried during backfilling, and the other side was sloped to facilitate the subsequent placement of strain gauges.

[0065] The precast concrete pipe 4 has an inner diameter of 1500mm, an outer diameter of 1800mm, and a length of 2000mm; the trench is 3.8m deep, 9m long, and 2m wide; and the concrete dimensions are 200cm*200cm*10cm.

[0066] The reinforced concrete sphere is reinforced with 3 M8 stirrups and 2 M8 longitudinal bars, with a steel grade of Grade 1. The sphere is made of C30 concrete and has a diameter of 340mm and a weight of approximately 50kg.

[0067] The pipe wall thickness is 150mm, and the total weight of the pipe is 1943kg, of which 1865kg is concrete and 55.36kg is steel reinforcement.

[0068] S3. Loading Test Model: A crane is used to lift the falling rock from model 1, suspending it above the buried pipeline model. The crane then releases the rock, allowing it to fall freely. A data testing device is used to collect data on the rock's strain, impulse and velocity, changes in soil pressure in the undisturbed soil layer, and strain of the buried pipeline model from model 1. Specific details are as follows:

[0069] The data testing apparatus includes strain bricks, earth pressure gauges (5), strain gauges (6), and a high-speed camera. The strain bricks are made using epoxy resin.

[0070] like Figure 2 As shown, strain gauge 6 includes circumferential strain gauge and axial strain gauge. Five strain monitoring sections are set on the inner wall of the buried pipeline model, namely the top, waist and bottom positions of two sections directly below the impact point and one meter along the axis, and the top position of the section 3 meters to the left and right of the impact point along the axis.

[0071] A crane was used to lift the falling rocks to a height of 30m above the buried pipeline model and place them stationary. After turning on all the data acquisition instruments, the test personnel evacuated to a safe position and waited for the release command to allow the falling rocks to fall at a fixed point. Fixed-point falling can precisely control the landing point of each falling rock.

[0072] When the falling rock impacts the model 1, strain gauges fixed inside the steel cage collect the rock strain data, strain gauges 6 attached to the inner wall of the buried pipeline model collect the dynamic strain of the pipeline, and earth pressure gauges 5, positioned 2.0m and 3.8m above the centerline of the buried pipeline model at different distances from the ground surface, collect the earth pressure change characteristics. A high-speed camera positioned near the impact point records images of the falling rock after its release from the air, thus obtaining the impact velocity and providing crucial data support for subsequent impact force and impulse calculations. To simulate the most dangerous situation of the buried tongue-and-groove concrete pipeline 4 being impacted by falling rocks, the impact point 7 is set at the center of the concrete cushion layer. Figure 3 As shown.

[0073] In this embodiment, a Phantom high-speed camera was placed 10m away from the impact point, and the trajectory and fall velocity were calculated using the domestically produced Qianyanlang image analysis software. The strain gauge 6 is 80mm long and has a resistance of 120Ω. The dynamic signal testing and analysis system is model DH5956. When analyzing the data from strain gauge 6, the measurement accuracy of the dynamic signal testing and analysis system is 10 microstrains, and the sampling rate is 2000Hz per channel. When analyzing the data from earth pressure gauge 5 at a depth of 2.0 meters, the range of the dynamic signal testing and analysis system is 0.5MPa; when analyzing the data from earth pressure gauge 5 at a depth of 3.8 meters, the range of the dynamic signal testing and analysis system is 0.2MPa.

[0074] The falling rock has a height of h = 30 meters and a landing speed of v = 24.5 m / s.

[0075] S4. Model Test and Data Recording: Analyze the data collected in step S3. If the analysis results exceed the preset safety range or the data collected by the instrument is inaccurate due to improper arrangement of the monitoring equipment, the control system will automatically activate the emergency plan to ensure the safety of the test and the reliability of the data; otherwise, the data will be retained. Specific details are as follows:

[0076] Strain gauge 6 is connected to the dynamic signal testing and analysis system via a quarter-bridge circuit. The acquired dynamic strain is plotted into a strain-time history curve at the corresponding pipe section using software. The curve is then analyzed to determine whether the strain value exceeds the ultimate tensile strain value corresponding to the unstable propagation of cracks in the reinforced concrete pipe 4 used in the test.

[0077] Earth pressure gauge 5 is connected to the dynamic signal testing and analysis system via a full bridge. The product of the collected earth pressure variation characteristics and the constant coefficient K is plotted into an earth pressure time history curve. Based on the curve, the change law of earth pressure is analyzed. Earth pressure not only has a direct impact on the structural integrity of the pipeline, but also affects the deformation, displacement and possible failure modes of the pipeline under impact load.

[0078] Images acquired by a high-speed camera are input into an image analysis system, and the trajectory of the impacting object and its ground contact velocity are obtained based on the height of the rockfall at different times.

[0079] The emergency plan includes suspending the test, adjusting the rockfall parameters, and rearranging the data testing equipment.

[0080] S5. Using the controlled variable method, change the thickness of the subbase and the concrete strength of subbase model 2, while keeping other model parameters constant. Repeat steps S3-S4 until all parameters of subbase model 2 have been tested. The parameters of subbase model 2 include the thickness of the subbase and the concrete strength.

[0081] In this embodiment, the pipeline parameters are kept constant, the pipeline burial depth is 2.0m, the rockfall impact energy is 100kJ, the concrete strength of the cushion layer is C30, and the thickness of the cushion layer is changed to 10cm, 15cm, 20cm, 25cm, and 30cm. The soil pressure and strain of the buried pipeline under different concrete cushion layer thicknesses are recorded.

[0082] Keeping the pipeline parameters constant, the pipeline burial depth is 2.0m, the rockfall impact energy is 100kJ, and the thickness of the subbase is 0.1m. The concrete strength of the subbase is changed to C20, C25, C30, C35, and C40. The earth pressure and strain of the buried pipeline under different concrete strengths are recorded.

[0083] S6. Experiment Summary and Feedback: Further analysis of the retained data yielded the relationship between strain and the parameters of the cushion layer model 2, completing the parameter design of the buried pipeline. Specific details are as follows:

[0084] By changing the parameters of the subbase model 2, the protective effect on the pipeline under different rockfall impacts was obtained.

[0085] Using the ultimate tensile strain of prestressed (self-stressed) concrete pipe 4 as specified in GB50268—2008 Code for Construction and Acceptance of Water Supply and Drainage Pipeline Engineering as the safety threshold, the relationship between the peak tensile strain of the pipe and the thickness of the cushion layer is obtained as follows:

[0086]

[0087] Where, ε p denoted as peak tensile strain, h as thickness of the cushion layer, and A, B, and k as correlation coefficients.

[0088] The relationship between the peak tensile strain of the pipeline and the concrete strength of the subbase is as follows:

[0089]

[0090] Where C represents the concrete strength grade.

[0091] S7. Evaluate the effectiveness and accuracy of the experimental system and methods, propose improvement measures and optimization suggestions for problems found in the experiment, and provide a reference for the next experiment or practical engineering application. At the same time, compile the experimental data and results into a report to facilitate subsequent research and communication.

[0092] In this embodiment, corresponding strain-to-substrate thickness curves and strain-to-substrate concrete strength curves are plotted based on the acquired data. For example... Figure 4 As shown, the peak strain of the pipeline decreases non-linearly with increasing concrete cushion thickness. When the cushion thickness is 30cm, the peak tensile strain of the pipeline can be reduced by 27.91% compared to a cushion thickness of 10cm. Figure 5 As shown, the peak strain of the pipeline decreases nonlinearly with the increase of the strength of the subbase concrete. When the subbase concrete strength is C40, the peak strain of the pipeline can be reduced by 19.65% compared with the C20 concrete strength.

[0093] The method provided by this invention can provide guidance for the protection of buried tongue-and-groove concrete pipes. The provided examples give the specific parameter design process and conclusions of the concrete cushion layer, achieving the expected goals and effectively solving the research problems.

[0094] To ensure the accuracy of the experiment, a large number of materials and equipment were used. Subsequent research can be based on this experiment, and numerical simulation software can be used to build models to complete further research.

[0095] This invention enables the establishment of a corresponding field test model by determining a reasonable similarity scale, simplifying the analysis of the concrete cushion layer test prototype for buried pipelines impacted by falling rocks, and achieving adaptability to different engineering realities. By simulating the processes of falling rock impact, pipeline burial depth, and cushion layer protection, it effectively simulates the protective effect of the concrete cushion layer on buried pipelines under falling rock impact, making it closer to actual engineering and providing valuable reference for practical projects.

[0096] The impact of falling rocks is simulated by using a reinforced concrete sphere, and the protective effect of the concrete cushion layer on buried pipelines in actual engineering is simulated by changing the thickness of the concrete cushion layer. The device is simple and has a certain degree of reliability. It can accurately control the magnitude of dynamic load and can basically achieve the principle of controlling a single variable in the experiment.

[0097] The measurement system can simulate the strain of buried pipelines caused by falling rocks on concrete cushion layers, as well as the changes in soil pressure in the clay layer, providing experimental basis and research methods for further revealing the protective effect of different thicknesses of concrete cushion layers on buried pipelines.

[0098] Where there is no conflict, the above embodiments and features described herein can be combined with each other.

[0099] This invention also proposes a parameter design system for the surface concrete cushion layer of buried pipeline protection based on the impact of falling rocks. The system includes a data preparation module, an experimental model construction module, a data acquisition module, a data analysis module, an experimental module, a parameter design module, and a computer program that can run on a processor. It should be noted that each module in the above system corresponds to a specific step of the method provided in this invention embodiment, possessing the corresponding functional modules and beneficial effects for executing the method. Technical details not described in detail in this embodiment can be found in the method provided in this invention embodiment.

[0100] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the technical principles of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A method for designing parameters of surface concrete cushion layer for buried pipeline protection based on the impact of falling rocks, characterized in that, include: S1. Determine the parameters of the falling rock, pipeline, soil, and concrete cushion layer; S2. Construct a rockfall impact model (1), a buried pipeline model, and a subgrade model (2); the buried pipeline model is placed in a trench filled with undisturbed soil, the subgrade model (2) is placed above the buried pipeline model, and the rockfall impact model (1) is placed above the subgrade model (2); specifically: A rockfall impact model was constructed using cast-in-place concrete spheres (1), a buried pipeline model was obtained by splicing four sections of concrete pipe (4) through tongue and groove joints, and a subbase model (2) was obtained by concrete pouring. Use an excavator to dig a trench, place the buried pipeline model in the trench, and then use an excavator to backfill it with the original soil on site. When backfilling, one side of the buried pipeline model is completely buried, and the other side is sloped. S3. Use data testing equipment to collect strain data and velocity data when rocks fall, changes in soil pressure in the undisturbed soil layer, and strain data of the buried pipeline model. S4. Analyze the data collected in step S3. If the analysis result exceeds the preset safety range, the control system will automatically activate the emergency plan; otherwise, the data will be retained. S5. Using the controlled variable method, change the parameters of the cushion layer model (2) while keeping other model parameters unchanged. Repeat steps S3-S4 until all parameters of the cushion layer model (2) are analyzed and then stop. The parameters of the cushion layer model (2) include the thickness of the cushion layer and the concrete strength. S6. Further analysis of the retained data yields the relationship between strain and parameters of the cushion layer model (2), completing the parameter design of the buried pipeline; specifically: By changing the parameters of the cushion layer model (2), the protective effect on the pipeline under different rockfall impacts was obtained. Setting the ultimate tensile strain of the concrete pipe (4) as a safety threshold, the relationship between the peak tensile strain of the pipe and the thickness of the cushion layer is obtained as follows: Where, ε p is the peak tensile strain, h is the thickness of the cushion layer, and A, B, and k are all correlation coefficients; The relationship between the peak tensile strain of the pipeline and the concrete strength of the subbase is as follows: Where C represents the concrete strength grade.

2. The method for designing parameters of the surface concrete cushion layer for buried pipeline protection based on the impact of falling rocks, as described in claim 1, is characterized in that... In step S1, determining the experimental parameters includes the following: Based on the first and second similarity theory criteria, the parameters are designed, and the geometric similarity ratio of the layout is determined to be L=1. The cross-sectional dimensions and burial depth are designed according to the prototype dimensions at a 1:1 ratio. The similarity ratios of gravitational acceleration, unit weight, and density are Cg=1, Cγ=1, and Cr=1. Based on the similarity ratios of geometric and unit weight, the Poisson's ratio and friction angle are fully similar. The elastic modulus is designed according to the similarity ratio of the prototype soil elastic modulus of 1. Rockfall parameters include shape, mass, angle, and release height; pipe parameters include material, diameter, wall thickness, and burial depth; and soil parameters include soil type, moisture content, and compaction degree.

3. The method for designing parameters of the surface concrete cushion layer for buried pipeline protection based on the impact of falling rocks, as described in claim 1, is characterized in that... The concrete ball has a diameter of 340mm and a mass of 50kg; the concrete pipe (4) has an inner diameter of 1500mm, an outer diameter of 1800mm, and a length of 2000mm; the trench is 3.8m deep, 9m long, and 2m wide; the concrete dimensions are 200cm*200cm*10cm.

4. The method for designing parameters of the surface concrete cushion layer for buried pipeline protection based on the impact of falling rocks, as described in claim 1, is characterized in that... In step S3, the collected data includes the following: The data testing device includes strain bricks, earth pressure gauges (5), strain gauges (6), and a high-speed camera; Using a crane, the falling rock in the rock impact model (1) is lifted and suspended above the buried pipeline model and left to stand still. After the data testing device is turned on, the rock is allowed to fall to a fixed point after the unhooking command is received. When the rockfall impact model (1) is impacted by falling rocks, the strain bricks fixed inside the steel cage of the rockfall impact model (1) collect the rockfall strain data, the strain gauges (6) pasted on the inner wall of the buried pipeline model collect the dynamic strain of the pipeline, the earth pressure gauge (5) set at a set distance from the ground surface directly above the centerline of the buried pipeline model collects the earth pressure change characteristics, and the high-speed camera set next to the impact point records the image generated by the falling process of the rockfall after being released from the air, thereby obtaining the speed of the rockfall impact; wherein, the impact point (7) is set at the center of the concrete cushion layer.

5. The method for designing parameters of the surface concrete cushion layer for buried pipeline protection based on the impact of falling rocks, as described in claim 4, is characterized in that... Strain bricks were fabricated using epoxy resin. The strain gauge (6) includes a circumferential strain gauge and an axial strain gauge. Five strain gauge monitoring sections are set on the inner wall of the buried pipeline model, namely the top, waist and bottom positions of two sections directly below the impact point and one meter along the axis, and the top position of the section 3 meters to the left and right of the impact point along the axis.

6. The method for designing parameters of the surface concrete cushion layer for buried pipeline protection based on the impact of falling rocks, as described in claim 4, is characterized in that... In step S4, the data analysis includes the following: Earth pressure gauge (5) is connected to dynamic signal testing and analysis system through a full bridge. The product of the collected earth pressure change characteristics and constant coefficient K is plotted as earth pressure time history curve. The change trend of earth pressure is analyzed based on the curve. The strain gauge (6) is connected to the dynamic signal test and analysis system through a quarter bridge. The collected dynamic strain is plotted into a strain time history curve under the corresponding pipe section using software. Based on the curve, it is analyzed whether the strain value exceeds the ultimate tensile strain value corresponding to the unstable expansion of cracks in the concrete pipe (4). The images acquired by the high-speed camera are input into the image analysis system, and the trajectory of the impacting object and the velocity of the impacting object upon contact with the ground are obtained based on the height of the rockfall at different times. The emergency plan includes suspending the test, adjusting the rockfall parameters, and rearranging the data testing equipment.

7. A system applied to the method for designing parameters of the surface concrete cushion layer for buried pipeline protection based on the impact of falling rocks as described in claim 1, characterized in that, include: The data preparation module is used to determine the rockfall parameters, pipe parameters, soil parameters, and different concrete cushion layer parameters required for the experiment. The test model construction module is used to construct the rockfall impact model, the buried pipeline model, and the cushion layer model. The buried pipeline model is placed in a trench filled with undisturbed soil, the cushion layer model is placed on top of the buried pipeline model, and the rockfall impact model is placed on top of the cushion layer model. The data acquisition module is used to collect data on rockfall strain and velocity in the simulated rockfall impact model, changes in soil pressure in the undisturbed soil layer, and strain in the buried pipeline model using a data testing device. The data analysis module is used to analyze the data collected by the data acquisition module. If the analysis results exceed the preset safety range, the control system will automatically activate the emergency plan; otherwise, the data will be retained. The experimental module is used to change the parameters of the subgrade model using the controlled variable method, while keeping other model parameters constant, and repeat the steps of data acquisition and data analysis until all parameters of the subgrade model have been analyzed and then the process stops. The parameter design module is used to further analyze the retained data, obtain the relationship between strain and subbase thickness, and complete the parameter design of the buried pipeline.

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