Simulation device and method for pipeline leakage considering variability of sand foundation

Abstract

The invention relates to the technical field of geotechnical engineering model tests, and discloses a simulation device for pipeline leakage considering sandy soil foundation variability, which comprises a soil parameter field modeling module, a 3D printing modeling system, a model box, a pipeline, a water pressure loading system, a CCD continuous camera, a data acquisition system and a computer. A three-dimensional sand parameter field model is constructed through CPT field data, a sand foundation with spatial variability is generated in combination with a random field theory, and spatial distribution of mechanical parameters of a soil body is accurately reproduced by utilizing a multi-material 3D printing technology. The pipeline leakage process is simulated through controllable water pressure loading, and soil settlement and pipeline deformation are monitored in real time in combination with CCD imaging and a data acquisition system. The problems that in a traditional test, soil mass heterogeneity simulation and variability simulation technologies are lacked, and seepage-deformation coupling mechanism characterization is not clear are solved, and a reliable test platform is provided for mechanism analysis and prevention and control technology research and development of urban underground pipeline leakage disasters.

Description

Technical Field

[0001] The present invention relates to the technical field of geotechnical engineering model tests, and particularly relates to a simulation device and method for pipeline leakage considering the variability of sandy soil foundations. Background Art

[0002] With the acceleration of the urbanization process, the problem of local uneven settlement of urban roads in China has become increasingly severe. Ground settlement not only damages the integrity of the road structure, affects traffic efficiency, but also poses a potential threat to the safety of pedestrians and vehicles. Studying the internal mechanism of ground settlement and proposing scientific prevention and control measures have become an urgent need in the field of urban underground space safety. With the aging of urban underground pipe networks and the complexity of the load environment, the differential ground settlement induced by pipeline leakage has become the core hidden danger threatening urban safety. A large number of studies have shown that the causes of urban ground settlement can be attributed to natural factors (such as soil consolidation, groundwater extraction) and human factors (such as engineering construction, pipeline leakage). Among them, underground pipeline leakage, as a typical human factor, has become a key risk source for inducing regional settlement and even collapse due to its concealment and gradualness. Buried water supply / drainage pipelines are affected by factors such as steel corrosion and ground load impact, and are prone to form micro-cracks or holes. Under the action of the water pressure in the pipeline, the leaked water body carries hydrodynamic pressure to erode the surrounding soil, resulting in the migration and loss of fine particles, forming void areas or underground cavities; at the same time, the seepage water body changes the distribution of pore water pressure in the soil, weakens the soil strength parameters (such as cohesion, internal friction angle), and increases the effective stress. The continuous development of the above erosion-seepage coupling effect ultimately leads to the accumulation of soil deformation and differential ground settlement, and even induces sudden collapse disasters in severe cases.

[0003] At present, there are significant limitations in the research methods for ground settlement induced by pipeline leakage:

[0004] (1) Difficulty in in-situ observation: The process of underground pipeline leakage is highly concealed, and it is difficult to monitor the dynamic evolution of the seepage path, soil deformation, and cavity expansion in real time;

[0005] (2) Insufficient accuracy of numerical simulation: Existing fluid-solid coupling models are difficult to accurately describe the interaction between water and soil, the spatial variability of soil parameters, and the particle migration effect during the leakage process, resulting in a significant deviation between the prediction results and the actual working conditions;

[0006] (3) The experimental simulations are all based on the assumption of soil homogeneity, using homogeneous soil models, and cannot reflect the spatial random distribution characteristics of parameters such as the internal friction angle, relative density, and permeability coefficient of sand in the actual stratum;

[0007] (4) Rough artificial sample preparation in experiments: Relying on layered filling or mechanical mixing to prepare soil, it is impossible to accurately control the spatial gradient change of microscopic mechanical parameters;

[0008] (5)Single monitoring means: Relying on discrete displacement sensors, it is difficult to capture the full-field continuous deformation and the spatio-temporal correlation between seepage and settlement. Summary of the Invention

[0009] The present invention provides a simulation device and method for pipeline leakage considering the variability of sandy soil foundations. By integrating the random field theory and multi-material 3D printing technology, high-precision physical reconstruction of the spatial variability of soil parameters is achieved; combined with controllable seepage loading and full-field optical monitoring, it breaks through the problems of the lack of simulation of soil heterogeneity and variability and the unclear characterization of the seepage-deformation coupling mechanism in traditional tests, providing a reliable test platform for the mechanism analysis and prevention and control technology research and development of urban underground pipeline leakage disasters.

[0010] The present invention provides a simulation device for pipeline leakage considering the variability of sandy soil foundations, including:

[0011] A soil parameter field modeling module for three-dimensional modeling based on sandy soil foundation data;

[0012] A 3D printing modeling system, the 3D printing modeling system includes a main control machine, a multi-material proportioning port, and a multi-axis linkage printing platform. The main control machine is connected to the soil parameter field modeling module and the multi-material proportioning port. The multi-material proportioning port is connected to the multi-axis linkage printing platform, and the multi-axis linkage printing platform is provided with N material delivery pipes;

[0013] A model box for reproducing the spatial distribution of soil mechanical parameters. The model box is arranged below the N material delivery pipes. A pipeline with leakage holes is arranged inside the model box. The pipeline is arranged inside the model box and penetrates through the opposite side surfaces of the model box;

[0014] A water pressure loading system, the water pressure loading system is connected to one end of the pipeline and cooperates with the pipeline to simulate the leakage condition;

[0015] A data acquisition and monitoring system, the data acquisition and monitoring system includes a strain sensor arranged on the outer wall of the pipeline, and a micro earth pressure gauge and a soil pore water pressure gauge buried in the box body;

[0016] A CCD continuous photographing camera, the CCD continuous photographing camera is arranged on the side surface of the box body and has a set distance from the box body. The CCD continuous photographing camera cooperates with the data acquisition and monitoring system to synchronously collect pipeline pressure changes and deformations, soil responses, and surface settlement data and store them in a computer to analyze the leakage-settlement coupling law.

[0017] Further, the soil parameter field modeling module performs three-dimensional modeling based on a large amount of sandy soil foundation data from geotechnical explorations generated from CPT on-site data. Meanwhile, it generates a three-dimensional spatial variation distribution of sandy soil mechanical parameters based on the random field theory, defines the parameter variation coefficient and correlation distance through the setting of the correlation function method, discretizes the three-dimensional model into voxel grids, and then imports them into the 3D printing modeling system. Among them, the sandy soil mechanical parameters include the internal friction angle, particle size distribution, and relative density, and can be coupled with single or multiple parameters.

[0018] Further, in the 3D printing modeling system,

[0019] The multi-material ratio port includes N different sandy soil material supply bins, and the sandy soil material supply bins have different particle sizes designed according to different ratios for storing sandy soil materials with different physical and mechanical parameters;

[0020] The N material conveying pipes of the multi-axis linkage printing platform are used to transport sandy soil materials of different types and ratio designs. The material conveying pipes are connected to a nozzle pipe for controlling the flow rate and speed. The diameter of the nozzle pipe is adjustable, and a sensor is connected to the nozzle pipe to control the nozzle rate and the port flow rate and feedback to the main control machine;

[0021] The main control machine numerically analyzes the three-dimensional spatial variability sandy soil foundation model, converts the voxel grid into a material ratio code, and conveys the instruction to the multi-material ratio port. The multi-axis linkage printing platform sprays different sandy soil materials at the specified position according to the code instruction through the nozzle, and stacks layer by layer to form a heterogeneous spatial variability sandy soil foundation.

[0022] Further, the model box is composed of high-strength transparent acrylic plate material to form an uncovered rectangular box. Opposite sides of the box are provided with corresponding circular holes for installing the pipes. The pipes pass through the box through the circular holes and are sealed with epoxy resin glue. The pipes are hermetically connected to the water pressure loading system.

[0023] Further, the pipes are set as PE pipes, PVC pipes, and ductile iron pipes with specific sizes and thicknesses. Leakage holes are arranged at an axial interval of 10 cm on the pipes, and the diameter of the leakage holes is set according to the actual seepage flow rate.

[0024] Further, the water pressure loading system is a fully enclosed water tank, and the top of the fully enclosed water tank is provided with a first interface, a second interface, and a third interface;

[0025] The first interface is a water flow interface, its shape is an external thread, and it is closed with a cover when not in use;

[0026] The second interface is a pressure interface, which is connected to an air compressor to control the internal pressure of the pipeline. A first flow valve is provided at the pressure interface to control the leakage rate of the pipeline.

[0027] The third interface is connected to the pipeline, and a second flow valve and a control valve are provided at the connection.

[0028] Further, the strain sensor, the earth pressure gauge, and the soil pore water pressure gauge are used to collect and record the pressure change of the pipeline and the spatio-temporal evolution of seepage-stress in the soil during the pipeline leakage process, and transmit the collected data to the computer for storage and analysis.

[0029] The present invention provides a simulation method for pipeline leakage considering the variability of sandy soil foundations. Based on the simulation device for pipeline leakage considering the variability of sandy soil foundations as described above, the simulation method specifically includes:

[0030] S1. Collect the CPT in-situ investigation data of the target area, use the soil parameter field modeling module to construct a three-dimensional model of the sandy soil foundation, generate a random field of the variation of the physical and mechanical parameters of the sandy soil based on the random field theory by setting the correlation function method, and embed it into the three-dimensional model of the sandy soil foundation. The randomness and correlation of the spatially variable soil are characterized by the trend function, the coefficient of variation, and the correlation distance.

[0031] S2. The soil parameter field modeling module discretizes the three-dimensional model of the sandy soil foundation into 1 cm 3 voxel grids, and converts them into the material mix ratio codes of each voxel and accesses them into the main control computer of the 3D printing modeling system. Each voxel grid includes coordinates, the internal friction angle φ, the grading curve parameters, and the relative density Dr.

[0032] S3. The main control computer of the 3D printing modeling system receives the material mix ratio codes, and transmits the instructions to the multi-axis linkage printing platform, drives the corresponding sandy soil material supply bins in the multi-material ratio ports, conveys the sandy soil materials to the material conveying pipes. Under the intelligent coupling control of the multi-axis linkage printing platform, the nozzles of each material conveying pipe spray the sandy soil materials at specific spatial positions in the model box to complete their respective printing paths.

[0033] S4. Start the water pressure loading system, control the internal water pressure of the pipeline through an air compressor, and control the leakage rate of the leakage holes of the pipeline through the first flow valve to simulate the leakage condition.

[0034] S5. The deformation of the pipeline is collected in real time by the strain sensors of the data acquisition and monitoring system. The soil body is monitored by the earth pressure cells and soil pore water pressure gauges. The simulation box is photographed from the front and top views by the CCD continuous photography camera, so as to extract the full-field displacement through the DIC analysis software. The strain sensors, earth pressure cells, soil pore water pressure gauges and CCD continuous photography camera are synchronously triggered to collect data and transmit it to the computer to analyze the leakage-settlement coupling law.

[0035] The beneficial effects of the present invention are as follows:

[0036] The present invention provides a soil variability leakage-settlement simulation device based on 3D printing technology, and its technical breakthroughs are reflected in:

[0037] 1) High-precision reproduction of soil spatial variability: Breaking through the limitations of traditional homogeneous soil bodies, based on the random field theory, converting CPT exploration data into a three-dimensional heterogeneous soil body model, and precisely implanting the random gradient distribution of parameters such as the internal friction angle of sand, the relative density of sand, and the permeability coefficient in the physical model through multi-material coupling 3D printing technology.

[0038] 2) Intelligent 3D printing control system: Adopting voxel-level material ratio coding technology, the main control machine discretizes the three-dimensional soil body parameter field into voxel grids (the smallest unit is 1 cm 3 ), drives the multi-nozzle collaborative operation, and adjusts the spraying flow rate and path of different sand materials (such as fine sand, medium sand, and coarse sand) in real time to achieve "pixel-level" precise printing of soil mechanical parameters. It supports customizing random field parameters such as the coefficient of variation (COV = 0.1 - 0.5) and correlation distance (0.1 - 1 m) to adapt to different geological conditions.

[0039] 3) Whole-process coupling monitoring of seepage-settlement: Combining the CCD camera and digital image correlation method (DIC), realizing sub-millimeter resolution monitoring of the soil surface displacement field (accuracy 0.05 mm), accurately capturing the differential settlement boundary and the expansion form of the void area. Through the closed-loop feedback control of pressure-flow-deformation, dynamically simulating the interaction between water pressure fluctuations and soil response in actual pipeline leakage. Description of the Drawings

[0040] Figure 1 It is a schematic structural diagram of the simulation device for pipeline leakage considering the variability of sandy soil foundation of the present invention.

[0041] Figure 2 It is a front view of the structure of the simulation device for pipeline leakage considering the variability of sandy soil foundation of the present invention.

[0042] Figure 3 It is a schematic flow diagram of the simulation method for pipeline leakage considering the variability of sandy soil foundation of the present invention.

[0043] In the attached drawings, there are a soil parameter field modeling module 1, a main control machine 21, a multi-material ratio port 22, a multi-axis linkage printing platform 23, a sandy soil foundation 24, a material delivery pipe 25, a 3D printing modeling system 2, a model box 3, a pipeline 4, a water pressure loading system 5, a first interface 51, a second interface 52, a third interface 53, a CCD continuous camera 6, and a data acquisition and monitoring system 7.

[0044] The realization, functional features, and advantages of the objectives of the present invention will be further described in conjunction with embodiments with reference to the attached drawings. Specific Embodiments

[0045] It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention.

[0046] The present invention provides a simulation device and method for pipeline leakage considering the variability of sandy soil foundations, belonging to the technical field of geotechnical engineering tests. The device includes a soil parameter field modeling module 1, a 3D printing modeling system 2, a model box 3, a pipeline 4, a water pressure loading system 5, a CCD continuous camera 6, a data acquisition system, and a computer. A three-dimensional sandy soil parameter field model is constructed through CPT field data, a sandy soil foundation with spatial variability is generated in combination with the random field theory, and the spatial distribution of soil mechanical parameters (such as internal friction angle, relative density, and particle size distribution) is accurately reproduced using multi-material 3D printing technology. The process of pipeline leakage is simulated through controllable water pressure loading, and soil settlement and pipeline deformation are monitored in real time in combination with CCD imaging and the data acquisition system. The present invention solves the error problem caused by the assumption of soil uniformity in traditional tests, and uses advanced and precise 3D printing technology to accurately simulate the spatial variability of real sandy soil foundations, providing technical support for the refined simulation and prediction of pipeline leakage disasters.

[0047] As Figure 1-2 shown, the present invention provides a simulation device for pipeline leakage considering the variability of sandy soil foundations, including:

[0048] A soil parameter field modeling module 1, used for three-dimensional modeling based on sandy soil foundation data;

[0049] A 3D printing modeling system 2, the 3D printing modeling system 2 includes a main control machine 21, a multi-material ratio port 22, and a multi-axis linkage printing platform 23. The main control machine 21 is connected to the soil parameter field modeling module 1 and the multi-material ratio port 22. The multi-material ratio port 22 is connected to the multi-axis linkage printing platform 23, and the multi-axis linkage printing platform 23 is provided with N material delivery pipes 25;

[0050] The model box 3 is used to reproduce the spatial distribution of soil mechanical parameters. The model box 3 is arranged below N material conveying pipes 25. A pipe 4 with leakage holes is arranged inside the model box 3. The pipe 4 is arranged inside the model box 3 and penetrates through the opposite side surfaces of the model box 3.

[0051] The water pressure loading system 5 is connected to one end of the pipe 4 and cooperates with the pipe 4 to simulate the leakage condition.

[0052] The data acquisition and monitoring system 7 includes a strain sensor arranged on the outer wall of the pipe 4, and a micro earth pressure gauge and a soil pore water pressure gauge buried in the box body.

[0053] The CCD continuous photographing camera is arranged on the side surface of the box body and has a set interval distance from the box body. The CCD continuous photographing camera cooperates with the data acquisition and monitoring system 7 to synchronously collect the pressure change and deformation of the pipe 4, the soil response and the ground settlement data and store them in a computer to analyze the leakage-settlement coupling law.

[0054] In one embodiment, the soil parameter field modeling module 1 performs three-dimensional modeling based on a large amount of sandy soil foundation data obtained from geotechnical exploration generated from CPT field data. At the same time, based on the random field theory, a three-dimensional spatial variation distribution of sandy soil mechanical parameters (internal friction angle, particle size distribution, relative density, which can be a single parameter or multiple parameters for coupling) is generated. The parameter variation coefficient and correlation distance are defined by setting the correlation function method, and the three-dimensional model is discretized into voxel grids, and then imported into the 3D printing modeling system 2.

[0055] In one embodiment, the 3D printing modeling system 2 includes a main control machine 21, a multi-material ratio port 22 and a multi-axis linkage printing platform 23. The main control machine 21 numerically analyzes the three-dimensional spatial variability sandy soil foundation model, converts the voxel grid into a material ratio code, and sends the instruction to the material ratio port. The multi-axis linkage printing platform 23 sprays different sandy soil materials at the specified position according to the code instruction through an adjustable nozzle, and stacks them layer by layer to form a heterogeneous spatial variability sandy soil foundation 24, and the flow rate and movement path of the nozzle are controlled by real-time feedback of the main control machine 21.

[0056] The multi-material ratio port 22 includes N different sand material supply bins, and the sand material supply bins have different particle sizes designed according to different ratios, and are used to store sand materials with different physical and mechanical parameters (internal friction angle, particle size gradation, relative density). The N material conveying pipes 25 of the multi-axis linkage printing platform 23 are used to transport sand materials with different types and ratio designs. The material conveying pipes 25 are connected with a nozzle pipe for controlling the flow rate and speed. The diameter of the nozzle pipe is adjustable, and a sensor is connected to the nozzle pipe for controlling the nozzle rate and the port flow rate, and feeding back to the main control machine 21.

[0057] In one embodiment, the model box 3 is composed of a high-strength transparent acrylic plate material to form an uncovered rectangular box body. Circular holes corresponding to each other are provided on two opposite side surfaces of the box body. The aperture diameters are designed according to the geometric scale ratio and are slightly larger than the diameter of the pipeline 4 for installing the pipeline 4. The pipeline 4 penetrates through the box body through the circular holes and is sealed with epoxy resin glue. The pipeline 4 is hermetically connected to the water pressure loading system 5, and leakage holes are preset on the surface of the pipeline 4.

[0058] In one embodiment, the pipeline 4 is set as a PE pipe, a PVC pipe, or a ductile iron pipe with specific dimensions and thicknesses, and is set according to the model ratio. Leakage holes are arranged at an axial interval of 10 cm on the pipeline 4, and the diameter of the leakage holes is set according to the actual seepage flow rate. A strain sensor is connected to the pipeline 4 and is connected to the data acquisition and monitoring system 7.

[0059] In one embodiment, the water pressure loading system 5 is a fully enclosed water tank. The top of the fully enclosed water tank is provided with a first interface 51, a second interface 52, and a third interface 53. The first interface 51 is a water flow interface, and its shape is an external thread and is closed with a cover when not in use. The second interface 52 is a pressure interface, and the pressure interface is connected to an air compressor to control the internal pressure of the pipeline 4. The pressure interface is provided with a first flow valve to control the leakage rate of the pipeline 4. The third interface 53 is connected to the pipeline 4, and a second flow valve and a control valve are arranged at the connection.

[0060] In one embodiment, the strain sensor, the earth pressure gauge, and the soil pore water pressure gauge are used to collect and record the pressure change of the pipeline 4 and the spatio-temporal evolution of soil seepage-stress during the leakage process of the pipeline 4, and transmit the collected data to the computer for storage and analysis. The CCD continuous camera 6 records the soil surface deformation from multiple angles, extracts the full-field displacement data through the digital image correlation method, and captures the water seepage process of the pipeline 4 and the spatio-temporal evolution process of soil settlement.

[0061] As Figure 3As shown, the present invention also provides a simulation method for pipeline leakage considering the variability of sandy soil foundation. Based on the simulation device for pipeline leakage considering the variability of sandy soil foundation as described above, the simulation method specifically includes:

[0062] S1. Collect the CPT on-site investigation data of the target area, use the soil parameter field modeling module 1 to construct a three-dimensional model of the sandy soil foundation, generate a random field of the variation of the physical and mechanical parameters of the sandy soil through the set correlation function method based on the random field theory, and embed it into the three-dimensional model of the sandy soil foundation. Characterize the randomness and correlation of the spatially variable soil through the trend function, coefficient of variation, and correlation distance.

[0063] Parametric modeling of variable soil and setting of random field:

[0064] 1) Collect 100 groups of CPT on-site investigation data (tip resistance range 5 - 30 MPa, side friction resistance 0.1 - 1.5 MPa) of the target area, and construct a three-dimensional model of the sandy soil foundation (geometric similarity ratio 1:20, model size 2m×1m×1m, corresponding prototype 40m×20m×20m);

[0065] 2) Use the exponential correlation function to generate a random field of the internal friction angle of the sandy soil (mean value 32°, coefficient of variation 0.2, correlation distance 0.5m). At the same time, couple the random distribution characteristics of the relative density of the sandy soil (mean value 0.65, coefficient of variation 0.15) and the particle size distribution (proportion of fine sand 30% - 70%) to generate a multi-parameter coupled heterogeneous soil model.

[0066] S2. The soil parameter field modeling module 1 discretizes the three-dimensional model of the sandy soil foundation into 1 cm 3 voxel grids, and converts them into the material mix ratio codes of each voxel and accesses the main control machine 21 of the 3D printing modeling system 2.

[0067] Model discretization is to discretize the three-dimensional model into 1 cm 3 voxel grids. Each grid unit contains coordinates (x, y, z), internal friction angle φ (28° - 38°), gradation curve parameters (d10 = 0.1 - 0.5 mm, Cu = 1.5 - 4.0), and relative density Dr (0.55 - 0.75).

[0068] S3. The main control machine 21 of the 3D printing modeling system 2 receives the material mix ratio code, and transmits the instruction to the multi-axis linkage printing platform 23, drives the corresponding sandy soil material supply bin in the multi-material ratio port 22, conveys the sandy soil material to the material conveying pipe 25. Under the intelligent coupling control of the multi-axis linkage printing platform, the nozzles of each material conveying pipe 25 spray the sandy soil material at specific spatial positions in the model box 3 to complete their respective printing paths.

[0069] 1) The 3D printing modeling system 2 prepares the sandy soil foundation: Convert the voxel grid data into material ratio codes, map them to the main control computer 21 of the 3D printing system. The main control computer 21 sends a call instruction to the material control port. The material ratio port contains multiple or N different sandy soil material supply bins.

[0070] 2) Configuration of material bins: Fine sand bin: The internal friction angle is 25° - 28°, d10 = 0.15 mm, Cu = 1.8; Medium sand bin: The internal friction angle is 30° - 32°, d10 = 0.35 mm, Cu = 2.5; Coarse sand bin: The internal friction angle is 34° - 38°, d10 = 0.45 mm, Cu = 3.5.

[0071] 3) The 3D printing system includes a multi-axis linkage printing platform 23. The multi-axis linkage printing platform 23 has N material delivery pipes 25 for transporting sandy soil materials with different types and ratio designs. The material delivery pipes 25 are connected to a nozzle pipe with controllable flow rate and speed, and its diameter is adjustable. An inductor is connected to the nozzle pipe to control the nozzle rate and port flow rate of different materials, and feedback to the main control computer 21 of the 3D printing modeling. In this embodiment, the main control computer 21 drives the 6-axis linkage printing platform (positioning accuracy ±0.1 mm) according to the code instruction, and through multi-nozzle collaborative spraying (the nozzle diameter is adjustable from 2 to 10 mm, and the flow control accuracy is ±2%), layer by layer to stack the sandy soil foundation 24.

[0072] 4) Quality verification: Randomly select 10% of the printing area for the penetration test (miniature CPT probe, diameter 5 mm). The deviation between the measured internal friction angle and the design value is ≤3°, and the relative density error is ≤5%.

[0073] S4. Start the water pressure loading system 5, control the internal water pressure of the pipeline 4 through the air compressor, and control the leakage rate of the leakage holes of the pipeline 4 through the first flow valve to simulate the leakage condition.

[0074] 1) Installation of the model box 3 and the pipeline 4: Use a high-transparency acrylic model box 3 (thickness 20 mm, compressive strength ≥80 MPa, size 2 m × 1 m × 1 m). A circular hole is opened on the front, rear, and both sides of the box body, and the hole diameter is slightly larger than the diameter of the pipeline 4. The interface uses glue to fix the pipeline 4. The opening hole diameter is converted according to the ratio required for the simulation. PVC pipelines (diameter 50 mm, wall thickness 3 mm) are embedded in the side walls. In this embodiment, it is assumed that leakage holes (diameter 2 mm, a total of 20 holes) are arranged at intervals of 10 cm along the axial direction of the pipeline 4. The interface between the pipeline 4 and the box body is sealed with epoxy resin glue. The end of the pipeline 4 is connected to a fully enclosed pressurized water tank (volume 50 L). The length of the buried pipeline 4 needs to completely penetrate the entire length of the model box 3. One end of the pipeline 4 is connected to the water tank, and the other end penetrates the model thickness and is connected to the water collection device.

[0075] 2) Water pressure loading system 5: The water tank connected to the pipeline 4 is in a fully enclosed state, with 2 interfaces on the upper part. The first interface 51 is a water flow interface, with an external thread shape. When not in use, it is closed with a cover. One end is connected to the pipeline 4, and a flow valve is set at the connection. The second interface 52 is a pressure interface. An air compressor outside the pressure interface is used to control the internal pressure of the pipeline 4. The water pressure in the pipeline 4 is adjusted to 0.2 MPa (simulating the municipal water supply pressure) through the air compressor (pressure range 0 - 0.5 MPa, control accuracy ±1 kPa), and the leakage rate is controlled at 3 L / min by the flow valve (range 0 - 10 L / min).

[0076] S5. The deformation condition of the pipeline 4 is real-time collected through the strain sensors of the data acquisition and monitoring system 7. The soil body is monitored through the earth pressure gauge and the pore water pressure gauge of the soil body. The simulation box is photographed from the front and top views by the CCD continuous photographing camera, so as to extract the full-field displacement through the DIC analysis software. The strain sensors, earth pressure gauges, pore water pressure gauges of the soil body and the CCD continuous photographing camera trigger data acquisition synchronously and transmit the data to the computer to analyze the leakage-settlement coupling law.

[0077] 1) Sensor arrangement: Pipeline 4 monitoring: 12 groups of strain gauges (range ±5000, accuracy 1) are pasted on the outer wall to collect the deformation of the pipeline 4 in real time.

[0078] 2) Soil body monitoring: Miniature earth pressure gauges (range 0 - 50 kPa, spacing 20 cm) and pore water pressure gauges (range 0 - 100 kPa, buried depths 10 cm, 30 cm, 50 cm, 80 cm) are buried.

[0079] 3) Surface deformation monitoring: A dual CCD camera (resolution 4096×2160, frame rate 30 fps) is used to photograph from the front and top views, and the full-field displacement (accuracy 0.05 mm) is extracted through the DIC analysis software (VIC-3D).

[0080] All sensors and cameras are synchronously triggered through the data acquisition system (NIPXIe-1082), with a sampling frequency of 100 Hz, and the data is stored in the computer for coupling analysis.

[0081] S6. Test process and results:

[0082] 1. Leakage - settlement dynamic evolution: Initial stage (0 - 10 min): The seepage water preferentially diffuses along the highly permeable sand layer (internal friction angle ≤ 30°), forming local seepage channels, and the surface settlement is 0.5 - 1.2 mm; Middle stage (10 - 30 min): The migration of fine particles leads to an increase in soil porosity, the void area expands to a diameter of 15 cm, and the differential settlement is significant (the maximum settlement is 8.3 mm, the minimum is 3.1 mm); Final stage (30 - 60 min): The pore water pressure accumulates to 35 kPa, the effective stress of the soil decreases, the settlement rate slows down, and the final maximum settlement is 12.7 mm.

[0083] 2. Analysis of the influence of parameter variability

[0084] Comparison of the coefficient of variation (COV) of the internal friction angle:

[0085] COV Maximum settlement (mm) Debonding zone diameter (cm) 0.1 9.2 8.5 0.2 12.7 15.0 0.3 14.5 18.2

[0086] Gradation coupling effect: When the proportion of fine sand is > 50%, the seepage erosion rate increases by 40% and the settlement range expands by 25%.

[0087] 3. Verification and comparison: Comparing the test results with the Abaqus fluid - solid coupling numerical model verifies the reliability of the 3D - printed heterogeneous soil model.

[0088] Repeat the above experiments, record the spatial variability of sandy soil with different water pressures and different physical and mechanical parameters, and explore the influencing factors of the spatial variability of sandy soil on the leakage of pipeline 4. In the initial stage of leakage, the water flow preferentially diffuses along the highly permeable sand layer, resulting in local settlement. As the leakage continues, differential settlement appears in the area of soil parameter variability. Compare the obtained test results with the numerical simulation.

[0089] It should be noted that in this article, the terms "include", "comprise" or any other variant thereof are intended to cover non - exclusive inclusion, so that a process, apparatus, article or method including a series of elements not only includes those elements but also includes other elements not expressly listed, or also includes elements inherent to such process, apparatus, article or method. Without further limitation, an element defined by the statement "including one..." does not exclude the existence of another identical element in the process, apparatus, article or method including that element.

[0090] The above - mentioned are only the preferred embodiments of the present invention, and do not limit the patent scope of the present invention. Any equivalent structural or equivalent process transformation made using the content of the specification and drawings of the present invention, or directly or indirectly applied in other related technical fields, shall be equally included in the patent protection scope of the present invention.

Claims

1. A simulation device for pipeline leakage considering the variability of sandy soil foundation, characterized in that Including: A soil parameter field modeling module for three-dimensional modeling based on sandy soil foundation data; A 3D printing modeling system, which includes a main control machine, a multi-material proportioning port, and a multi-axis linkage printing platform. The main control machine is connected to the soil parameter field modeling module and the multi-material proportioning port. The multi-material proportioning port is connected to the multi-axis linkage printing platform, and the multi-axis linkage printing platform is provided with N material conveying pipes; A model box for reproducing the spatial distribution of soil mechanical parameters. The model box is arranged below the N material conveying pipes. A pipe with leakage holes is arranged inside the model box. The pipe is arranged inside the model box and penetrates through the opposite side surfaces of the model box; A water pressure loading system, which is connected to one end of the pipe and cooperates with the pipe to simulate the leakage condition; A data acquisition and monitoring system, which includes a strain sensor arranged on the outer wall of the pipe, and a micro-earth pressure gauge and a soil pore water pressure gauge buried in the box body; A CCD continuous photographing camera, which is arranged on the side of the box body and has a set interval distance from the box body. The CCD continuous photographing camera cooperates with the data acquisition and monitoring system to synchronously collect data on pipeline pressure change and deformation, soil response, and ground settlement, and store them in a computer to analyze the leakage-settlement coupling law.

2. The simulation device for pipeline leakage considering the variability of sandy soil foundation according to claim 1, characterized in that, The soil parameter field modeling module performs three-dimensional modeling based on a large amount of sandy soil foundation data obtained from CPT in-situ data for geotechnical exploration. At the same time, it generates a three-dimensional spatial variability distribution of sandy soil mechanical parameters based on the random field theory, defines the parameter variation coefficient and the correlation distance by setting the correlation function method, discretizes the three-dimensional model into voxel grids, and then imports them into the 3D printing modeling system; among them, the sandy soil mechanical parameters include the internal friction angle, particle size distribution, and relative density, and can be coupled with a single parameter or multiple parameters.

3. The simulation device for pipeline leakage considering the variability of sandy soil foundation according to claim 1, characterized in that, In the 3D printing modeling system, The multi-material proportioning port includes N different sandy soil material supply bins. The sandy soil material supply bins have different particle sizes designed according to different proportions and are used to store sandy soil materials with different physical and mechanical parameters; The N material conveying pipes of the multi-axis linkage printing platform are used to transport sandy soil materials of different types and proportion designs. The material conveying pipes are connected with a nozzle pipe for controlling the flow rate and speed. The diameter of the nozzle pipe is adjustable, and an inductor is connected to the nozzle pipe to control the nozzle rate and the port flow rate, and feedback to the main control machine; The main control machine numerically analyzes the three-dimensional spatial variability sandy soil foundation model, converts the voxel grid into a material proportioning code, and sends the instruction to the multi-material proportioning port. The multi-axis linkage printing platform sprays different sandy soil materials at the specified position according to the code instruction through the nozzle, and stacks them layer by layer to form a heterogeneous spatial variability sandy soil foundation.

4. The simulation device for pipeline leakage considering the variability of sandy soil foundation according to claim 1, characterized in that, The model box is composed of high-strength transparent acrylic plates to form an uncovered rectangular box. Opposite sides of the box are provided with corresponding circular holes for installing the pipes. The pipes pass through the box through the circular holes and are sealed with epoxy resin glue. The pipes are hermetically connected to the water pressure loading system.

5. The simulation device for pipeline leakage considering the variability of sandy soil foundation according to claim 4, characterized in that The pipes are made of PE pipes, PVC pipes, or ductile iron pipes with specific dimensions and thicknesses. Leakage holes are arranged at an axial interval of 10 cm on the pipes, and the diameter of the leakage holes is set according to the actual seepage flow rate.

6. The simulation device for pipeline leakage considering the variability of sandy soil foundation according to claim 1, characterized in that, The water pressure loading system is a fully enclosed water tank. The top of the fully enclosed water tank is provided with a first interface, a second interface, and a third interface. The first interface is a water flow interface with an external thread shape and is closed with a cover when not in use. The second interface is a pressure interface. The pressure interface is connected to an air compressor to control the internal pressure of the pipes. The pressure interface is provided with a first flow valve to control the leakage rate of the pipes. The third interface is connected to the pipes, and a second flow valve and a control valve are arranged at the connection.

7. The simulation device for pipeline leakage considering the variability of sandy soil foundation according to claim 1, characterized in that, The strain sensors, earth pressure gauges, and soil pore water pressure gauges are used to collect and record the pressure changes in the pipes and the spatio-temporal evolution of soil seepage-stress during the pipe leakage process, and transmit the collected data to the computer for storage and analysis.

8. A simulation method for pipeline leakage considering the variability of sandy soil foundation, characterized in that, Based on the simulation device for pipe leakage considering the variability of sandy soil foundation according to any one of claims 1 to 7, the simulation method specifically includes: S1. Collect the CPT on-site investigation data of the target area, use the soil parameter field modeling module to construct a three-dimensional model of the sandy soil foundation, generate a random field of the variation of sandy soil physical and mechanical parameters based on the random field theory by setting the correlation function method, and embed it into the three-dimensional model of the sandy soil foundation. The randomness and correlation of the spatially variable soil are characterized by the trend function, coefficient of variation, and correlation distance. S2. The soil parameter field modeling module discretizes the three-dimensional model of the sandy soil foundation into 1-cm 3 voxel grids, and converts them into the material mix ratio codes of each voxel and accesses them to the main controller of the 3D printing modeling system; wherein each voxel grid includes coordinates, the internal friction angle φ, gradation curve parameters, and the relative density Dr. S3. The main control machine of the 3D printing modeling system receives the material mix ratio code and transmits the instruction to the multi-axis linkage printing platform, drives the corresponding sandy soil material supply bin in the multi-material mix ratio port, conveys the sandy soil material to the material conveying pipe. Under the intelligent coupling control of the multi-axis linkage printing platform, the nozzles of each material conveying pipe spray the sandy soil material at specific spatial positions in the model box to complete their respective printing paths. S4. Start the water pressure loading system, control the internal water pressure of the pipes through an air compressor, and control the leakage rate of the leakage holes of the pipes through the first flow valve to simulate the leakage condition. S5. Real-time collect the deformation of the pipes through the strain sensors of the data acquisition and monitoring system, conduct soil monitoring through the earth pressure gauges and soil pore water pressure gauges, and photograph the simulation box from the front and top views through the CCD continuous photography camera to extract the full-field displacement through the DIC analysis software. The strain sensors, earth pressure gauges, soil pore water pressure gauges, and CCD continuous photography camera synchronously trigger to collect data and transmit it to the computer to analyze the leakage-settlement coupling law.

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