Method and system for testing pipe-soil action of slope section in mountainous area

Abstract

The invention provides a method and a system for testing the pipe-soil action of a mountain slope section, belongs to the technical field of pipeline engineering, and aims to perform a landslide test under multiple gradients by simulating the real environment of the mountain slope section and construct a pipe-soil interaction model, so that the constructed pipe-soil interaction model is closer to the real situation, and the test efficiency is improved. The method comprises the following steps: burying a test pipe fitting in a test soil body; in response to triggering of the landslide test, the inclination angle of the test box body is controlled to change, so that the gradient of the test soil body is changed, and a first mechanical parameter and a second mechanical parameter are collected in the changing process until the inclination angle stops changing; the first mechanical parameters comprise stress and strain of the test pipe fitting and deformation of the test pipe fitting; the second mechanical parameters comprise soil pressure and deformation of soil around the pipe and overall deformation of the test soil body; and constructing a pipe-soil interaction model based on the first mechanical parameters and the second mechanical parameters.

Description

Technical Field

[0001] The invention relates to the technical field of pipeline engineering, and in particular to a test method and system for pipe-soil action in a slope section of a mountainous area. Background Art

[0002] As the fastest, most economical and most effective means of transporting oil and gas, the structural stability and safe operation of pipelines in service have gradually attracted widespread attention from the engineering community. According to the results of the national oil and gas resource evaluation, my country's oil and gas resource potential will be mainly distributed in the Sichuan Basin, the East Yunnan and West Guizhou Basins, and the Junggar Basin. More and more new long-distance buried pipelines will inevitably pass through mountainous areas in western my country. The slope sections of mountainous areas in some areas are affected by factors such as heavy rainfall and earthquakes, and are prone to landslides, which can cause pipeline deformation and even rupture, resulting in immeasurable losses. Therefore, before laying pipelines in mountain slope sections, it is necessary to evaluate the pipe-soil interaction in order to design the pipeline and select the location of the pipeline to avoid pipeline accidents caused by landslides.

[0003] At present, there are three main methods for evaluating pipe-soil interaction in the world: test method, analytical method and numerical simulation method. Among them, the test method is mainly used for the pipe-soil interaction evaluation of low-grade steel (≤X65) and small-diameter (≤600mm) steel pipes and small-diameter PVC and HDPE plastic pipes in dry and fully saturated sand. However, with the adjustment of my country's energy structure, especially the increase in demand for clean, green and environmentally friendly natural gas, the number of high-grade steel (X70, X80, X90 and X100) and large-diameter (Φ1016mm, Φ1219mm, Φ1422mm) oil and gas pipelines is increasing. In actual engineering, the stress state of the soil around the pipeline is completely different from the mechanical behavior of dry and fully saturated sand. It is difficult to obtain an accurate pipe-soil interaction model using the test method.

[0004] The analytical methods recommended by the current design guidelines (ASCE 1984, ALA 2005 and PRCI 2009) are all derived from the fitting of physical model test data. The recommended numerical simulation model is the elastic foundation beam model based on soil springs. This model idealizes the mechanical behavior of the soil into a series of independent and discontinuous soil springs, and evaluates the pipe-soil interaction by calculating the py curve of the soil spring stiffness. The py curve of the soil spring stiffness is a simple empirical fit based on the test data and cannot truly reflect the mechanical behavior of the soil. There are many uncertainties when it comes to problems such as non-uniform soil, multi-axial stress, strain localization and large strain, which makes the existing method of constructing the pipe-soil interaction model have large errors and low accuracy.

[0005] Therefore, a new method is urgently needed to construct a pipe-soil interaction model to improve the accuracy of pipe-soil interaction analysis. Summary of the invention

[0006] In view of this, the present invention aims to propose an experimental method and system for pipe-soil interaction in mountainous slope sections, so as to solve the problem of large errors and low accuracy in constructing pipe-soil interaction models using numerical simulation, analytical methods and the like.

[0007] A first aspect of an embodiment of the present invention provides a test method for pipe-soil action on a slope section in a mountainous area, the method comprising:

[0008] The test pipe is buried in a test soil body; wherein the test soil body is constructed in a test box;

[0009] In response to the triggering of the landslide test, the inclination angle of the test box is controlled to change so that the slope of the test soil body changes, and the first mechanical parameter and the second mechanical parameter are collected during the change process until the inclination angle stops changing;

[0010] The first mechanical parameter includes the stress and strain of the test pipe and the deformation of the test pipe; the second mechanical parameter includes the soil pressure and deformation of the soil around the pipe and the overall deformation of the test soil; the soil around the pipe is the soil around the test pipe;

[0011] Based on the first mechanical parameter and the second mechanical parameter, a pipe-soil interaction model is constructed; wherein the pipe-soil interaction model is used to simulate the interaction between the pipeline and the soil in the mountain slope section environment.

[0012] Furthermore, constructing the pipe-soil interaction model based on the first mechanical parameter and the second mechanical parameter includes:

[0013] Determine the first mechanical parameter and the second mechanical parameter in each landslide stage; wherein the landslide stage includes the initial small deformation stage, the uniform large deformation stage and the accelerated destruction stage of the test soil at the corresponding slope;

[0014] Based on the first mechanical parameter corresponding to each of the landslide stages, determining the first mechanical change characteristic corresponding to the landslide stage, and based on the second mechanical parameter corresponding to each of the landslide stages, determining the second mechanical change characteristic corresponding to the landslide stage;

[0015] The first mechanical change characteristics are the stress and strain change characteristics and deformation change characteristics of the test pipe at each landslide stage; the second mechanical change characteristics are the deformation mode and failure mode of the soil around the pipe at each landslide stage, and the deformation change characteristics of the slope as a whole at each landslide stage; the landslide stage includes the initial small deformation stage of the slope, the uniform large deformation stage and the accelerated failure stage;

[0016] The pipe-soil interaction model is constructed according to the first mechanical change characteristics and the second mechanical change characteristics respectively corresponding to each of the landslide stages.

[0017] Furthermore, burying the test pipe in the test soil includes:

[0018] burying the test pipe at a preset depth in the test soil;

[0019] The method further comprises:

[0020] The landslide test is carried out on the test soil body in which the test pipe is buried at different preset depths to obtain the corresponding pipe-soil interaction model.

[0021] Furthermore, before burying the test pipe in the test soil, the method further includes:

[0022] Performing compression and tension calibration tests on different pipe materials respectively, obtaining strength parameters and stress-strain curves of a plurality of the pipe materials, so as to determine a target pipe material from the plurality of the pipe materials;

[0023] The step of burying the test pipe in the test soil comprises:

[0024] A test pipe fitting cast with the target pipe material is buried in the test soil body to test the interaction between the test pipe fitting corresponding to the target pipe material and the test soil body.

[0025] A second aspect of the present invention provides a test system for pipe-soil action on a slope section in a mountainous area, the test system being used to implement the test method described in the first aspect, the test system comprising:

[0026] Pipeline landslide test platform and detection device;

[0027] The pipeline landslide test platform comprises: a test box with an opening at the top, a lifting device and a support platform; one end of the test box is connected to the lifting device, and the other end is rotatably connected to a fixed support on the support platform, so that the inclination angle of the test box changes with the lifting of the lifting device; the test box is used to hold test pipes and test soil;

[0028] The detection device is used to collect a first mechanical parameter and a second mechanical parameter; wherein the first mechanical parameter includes the stress and strain of the test pipe and the deformation of the test pipe; the second mechanical parameter includes the soil pressure and deformation of the soil around the pipe and the overall deformation of the test soil; the soil around the pipe is the soil located around the test pipe.

[0029] Furthermore, the lifting device is a hydraulic rod, a retractable end of the hydraulic rod is fixedly connected to one end of the test box, and the other end of the hydraulic rod is connected to the support platform, so that the one end of the test box can be lifted and lowered by the extension and retraction of the hydraulic rod, so that the inclination angle of the test box changes.

[0030] Furthermore, the test soil body includes a slope section and a slope top section, the slope top section is parallel to the bottom of the test box, and the slope section is close to one end of the test box connected to the fixed support, so that the slope of the test soil body changes with the inclination angle of the test box.

[0031] Furthermore, a sliding belt is laid on the inner bottom of the test box, and the test soil is accumulated on the surface of the sliding belt to assist the test soil in causing a landslide.

[0032] Furthermore, the test soil body includes a slope section and a slope top section; a load-bearing baffle is also provided inside the test box, and the load-bearing baffle is provided at one end away from the slope section and in contact with the test soil body;

[0033] Wherein, soil is filled in the gap area formed by the load-bearing baffle and the test box to apply thrust to the load-bearing baffle, so as to cause the test soil to slide.

[0034] Furthermore, the detection device includes a first detection device and a second detection device; wherein the first detection device is used to detect the overall deformation of the test soil, the deformation of the soil around the pipe and the deformation of the pipeline; the second detection device is used to detect the stress and strain of the test pipe, the stress and strain of the soil around the pipe and the soil pressure of the soil around the pipe.

[0035] The test system for the effect of pipe-soil on a slope section in a mountainous area and the test method for the effect of pipe-soil on a slope section in a mountainous area have the same advantages over the prior art, and will not be elaborated here.

[0036] Compared with the prior art, the test method for the pipe-soil action in mountainous slope sections of the present invention has the following advantages:

[0037] The test method for pipe-soil interaction in a mountain slope section provided by the present invention comprises: burying the test pipe in a test soil body; wherein the test soil body is constructed in a test box; in response to the triggering of a landslide test, controlling the inclination angle of the test box to change so that the slope of the test soil body changes, and collecting a first mechanical parameter and a second mechanical parameter during the change until the inclination angle stops changing; wherein the first mechanical parameter comprises the stress and strain of the test pipe and the deformation of the test pipe; the second mechanical parameter comprises the soil pressure and deformation of the soil surrounding the pipe and the overall deformation of the test soil body; the soil surrounding the pipe is the soil body located around the test pipe; based on the first mechanical parameter and the second mechanical parameter, constructing a pipe-soil interaction model; wherein the pipe-soil interaction model is used to simulate the interaction between the pipeline and the soil body in the mountain slope section environment;

[0038] Therefore, the present invention simulates the real environment of the mountain slope section through an indoor model, and then conducts a landslide test based on the simulated real environment. During the landslide test, mechanical parameters such as deformation, stress and strain of the test pipe and the test soil are collected. Since the mechanical parameters of the test pipe and the mechanical parameters of the test soil are continuously obtained during the test, it can reflect the mechanical change characteristics of the test pipe and the test soil during the test, that is, the change law of deformation, stress and strain, and then construct a pipe-soil interaction model of the mountain slope section according to the mechanical parameters. Therefore, since the mechanical parameters themselves reflect the real interaction between the pipe and the soil during the landslide, the constructed pipe-soil interaction model can be closer to the actual situation and can truly reflect the mechanical behavior of the soil; based on this method, the design of the pipeline and the selection of the laying position can improve the safety of the oil and gas pipeline in the mountain slope section; at the same time, since the test method provided by the present invention can carry out landslide tests under different slopes, the pipe-soil interaction model of the mountain slope section under different slopes can be directly obtained, and the test method is simple and fast. BRIEF DESCRIPTION OF THE DRAWINGS

[0039] The accompanying drawings constituting a part of the present invention are used to provide a further understanding of the present invention. The exemplary embodiments of the present invention and their descriptions are used to explain the present invention and do not constitute an improper limitation of the present invention. In the accompanying drawings:

[0040] Figure 1 A flow chart showing the steps of a test method for the pipe-soil action on a slope section in a mountainous area provided by the first embodiment of the present invention;

[0041] Figure 2 A flow chart showing the steps of a test method for the pipe-soil action on a slope section in a mountainous area provided by another embodiment of the present invention;

[0042] Figure 3A schematic diagram of the structure of a test system for pipe-soil action on a slope section in a mountainous area provided by a second embodiment of the present invention is shown;

[0043] Figure 4 The finite element model of the landslide test platform provided in the second embodiment of the present invention is shown;

[0044] Figure 5 A cross-sectional view of a test box provided in the second embodiment of the present invention is shown;

[0045] Figure 6 A top view of a test box provided in the second embodiment of the present invention is shown;

[0046] Figure 7 A diagram showing test results of a test method for the pipe-soil action on a mountain slope section according to an embodiment of the present invention;

[0047] Figure 8 A schematic diagram showing deformation results of a test pipe after a test method for the pipe-soil action on a mountain slope section according to an embodiment of the present invention;

[0048] Explanation of the accompanying reference numerals: 1. Pipeline landslide test platform; 11. Test box; 111. Test soil; 1111. Slope section; 1112. Slope top section; 112. Test pipe fitting; 113. Slide belt; 114. Load-bearing baffle; 12. Lifting device; 13. Support platform; 131. Fixed support; 132. Support column; 2. Detection device. DETAILED DESCRIPTION

[0049] It should be noted that, in the absence of conflict, the embodiments of the present invention and the features in the embodiments may be combined with each other.

[0050] In the related technologies, the evaluation methods of pipe-soil interaction usually adopt three methods: test method, analytical method and resin simulation method; among them, the test method is mainly used for the pipe-soil interaction evaluation of low-grade (≤X65) and small-diameter (≤600mm) PVC and HDPE plastic pipes in dry and fully saturated sand. However, with the adjustment of my country's energy structure, especially the increase in demand for clean, green and environmentally friendly natural gas, the number of oil and gas pipelines with high steel grades (X70, X80, X90 and X100) and large diameters (Φ1016mm, Φ1219mm, Φ1422mm) is increasing. In actual engineering, the stress state of the soil around the pipeline is completely different from the mechanical behavior of dry and fully saturated sand. It is difficult to obtain an accurate pipe-soil interaction model using the test method.

[0051] The formulas of the analytical method recommended in the current design guide are all derived from the fitting of physical model test data; in the recommended numerical simulation method, the numerical simulation model is an elastic foundation beam model based on soil springs; this model idealizes the mechanical behavior of the soil into a series of independent and discontinuous soil springs, and evaluates the pipe-soil interaction by calculating the py curve of the soil spring stiffness. Among them, the py curve of the soil spring stiffness is a simple empirical fit based on the test data, which cannot truly reflect the mechanical behavior of the soil, and there are many uncertainties when it comes to problems such as uneven soil, multi-axial stress, strain localization and large strain. Therefore, the current various pipe-soil interaction evaluation methods cannot reflect the actual pipe-soil interaction, which will cause deviations in the designed pipelines, especially in mountain slope sections. Due to the complex terrain and the susceptibility to landslides, it is easy to cause danger to the buried pipelines in mountain slope sections, causing immeasurable losses.

[0052] In view of this, the present invention provides a test method and system for pipe-soil interaction in a mountain slope section. By adopting a model test method, the environment of a real mountain slope section is simulated, and a landslide test is carried out in the simulated environment, and pipe-soil data under the action of the landslide is collected, and then a pipe-soil interaction model is constructed based on the pipe-soil data. Therefore, the process of pipe-soil interaction can be simulated and analyzed by an indoor model test method. Since the relevant parameters of the pipe-soil interaction are simulated based on the real situation, the constructed pipe-soil interaction model is close to the real situation, so that the pipeline designed based on the pipe-soil interaction model can remain safe under the action of the landslide, which greatly improves the safety of the pipeline.

[0053] The following will describe in detail a method and system for testing the pipe-soil action on a slope section in a mountainous area provided by the present invention with reference to the accompanying drawings and in combination with embodiments.

[0054] Embodiment 1

[0055] Reference Figure 1 , Figure 1 The flowchart of the test method for the soil-pipe action in a mountain slope section provided by the embodiment of the present invention is shown as follows: Figure 1 As shown, the method includes:

[0056] S101, burying the test pipe in the test soil.

[0057] The test soil is constructed in a test box. The test soil is collected according to the actual situation of the mountain slope section to simulate the situation of laying pipelines in the mountain slope section. That is, the slope of the test soil is set according to the slope of the mountain slope section, and the material and compaction degree of the test soil are determined according to the soil material of the mountain slope section.

[0058] In order to simulate the slopes of various mountain slopes, the test box is set to have an adjustable tilt angle. Therefore, for mountain slopes with different slopes, only the tilt angle needs to be adjusted to simulate the slope of the real environment.

[0059] In the embodiment of the present invention, the position where the test pipe is buried in the test soil is determined according to the actual situation. For example, the laying position of the test pipe is determined based on the depth-to-diameter ratio used in history.

[0060] In some embodiments, due to differences in the environments of different mountain slope sections, such as different soil structures and different soil materials, the same laying position does not mean that the current position is the position with the least stress. Therefore, multiple depth-to-diameter ratios can be set to conduct landslide tests at different laying positions to determine the specific burial depth of the pipeline.

[0061] S102, in response to the triggering of the landslide test, controlling the inclination angle of the test box to change so that the slope of the test soil body changes, and collecting the first mechanical parameter and the second mechanical parameter during the change process until the inclination angle stops changing.

[0062] Among them, the first mechanical parameters include the stress and strain of the test pipe fitting, and the deformation of the test pipe fitting; the second mechanical parameters include the soil pressure and deformation of the soil around the pipe, and the overall deformation of the test soil; the soil around the pipe is the soil located around the test pipe fitting.

[0063] In the embodiment of the present invention, a pipe-soil interaction model under landslide is constructed. Therefore, by conducting a landslide test, a landslide occurs in the slope section of the test soil body, and data is collected during the landslide. During the landslide test, the slope of the test soil body is changed by changing the inclination angle of the test box, so that the landslide test is carried out at different slopes to obtain the deformation, stress strain and soil pressure of the test pipe and the test soil body at different slopes. Thus, the pipe-soil interaction at different slopes can be obtained to meet the pipeline design requirements of different slopes in mountain slope sections.

[0064] In some embodiments, considering the changes in soil quality in mountain slope sections, during the model test, test models with different compaction degrees, different slopes and different burial depths can be directly used to conduct landslide tests to take into account pipeline design requirements in various situations.

[0065] For example, as shown in Table 1 below, Table 1 shows 6 groups of different model test parameters, thereby obtaining the interaction between pipelines and soils with different soil materials, different compaction degrees, different slopes and different buried depths under the action of landslides, thereby meeting the pipeline design requirements for slope sections in mountainous areas and improving the safety of oil and gas pipelines.

[0066] Table 1 Test groups with different test soils, different slopes and different depth-to-diameter ratios

[0067] serial number Test soil Slope(°) Pipe diameter(mm) Aspect ratio H / D 1 Loose sand 15(°) 100 1 2 Medium dense sand 30(°) 100 2 3 Compacted sand 45(°) 100 3 4 Loose clay 15(°) 100 1 5 medium dense clay 30(°) 100 2 6 Compacted clay 45(°) 100 3

[0068] S103: constructing a pipe-soil interaction model based on the first mechanical parameter and the second mechanical parameter.

[0069] The pipe-soil interaction model is used to simulate the interaction between the pipe and the soil in the mountain slope environment. Specifically, it is mainly the interaction between the pipe buried in the soil and the soil around the pipe in the mountain slope environment under the action of landslide. Its main purpose is to design the wall thickness, burial position, etc. of the pipe buried in the mountain slope, that is, for pipeline design.

[0070] Specifically, after collecting multiple first mechanical parameters and second mechanical parameters, in order to construct a pipe-soil interaction model, it is necessary to determine the deformation, stress-strain of the test pipe at each landslide stage, the soil pressure, deformation and stress-strain values ​​of the soil around the pipe, and the deformation value of the slope as a whole; and then determine the deformation, stress-strain change characteristics of the pipeline and soil at each landslide stage. Therefore, based on a variety of change characteristics, the deformation mechanism of the pipeline under the action of landslide, the strain, soil pressure, deflection and other conditions of the limit and critical limit states, are obtained, thereby providing a reference for the design of the pipeline.

[0071] In some embodiments, the test method of the embodiment of the present invention can also be used to evaluate the safety of pipelines, etc., so as to determine the safety of pipelines buried in mountain slope sections by constructing a pipe-soil interaction model.

[0072] For example, when it is necessary to evaluate the safety of a pipeline on a slope section in a mountain area, the soil quality of the slope section in the mountain area, the slope gradient, the laying position of the pipeline, and the diameter and wall thickness of the pipeline are determined; then the soil environment of the slope section in the mountain area and the laying position of the pipeline are simulated in a test box; wherein, a similar simulation method is used to determine the laying position, diameter and wall thickness of the pipeline in the mountain slope section model, such as determining the ratio of the burial depth of the test pipe fitting to the actual burial depth by determining the ratio of the height of the test soil body to the height of the actual mountain slope, and then determining the burial depth of the pipeline; thus, after burying the test pipe fitting simulating the actual pipeline at the corresponding laying position, the inclination angle of the test box is controlled to change until the test soil body reaches the corresponding angle; then a landslide test is carried out to determine the deformation degree of the pipeline under the action of the landslide, and the safety of the pipeline is evaluated by the deformation degree.

[0073] The test method for pipe-soil interaction in a mountain slope section provided by an embodiment of the present invention uses a model to simulate the real environment of a mountain slope section, and then conducts a landslide test in the simulated environment and collects test data. Based on the collected data of landslide tests with different slopes, the interaction between the pipeline and the soil in the mountain slope section is simulated, and a pipe-soil interaction model is constructed; thereby, the obtained pipe-soil interaction model is closer to the real result, thereby improving the safety of the oil and gas pipeline in the mountain slope section and avoiding the occurrence of pipeline rupture caused by landslides; at the same time, since the inclination angle of the test box can be directly changed in the embodiment of the present invention to change the slope of the test soil, landslide tests under different slopes can be carried out simultaneously, and pipe-soil test models under multiple slopes can be determined, thereby simplifying the test method.

[0074] Reference Figure 2 , Figure 2 FIG. 1 is a flow chart showing a method for testing soil-pipe action in a slope section of a mountainous area according to another embodiment of the present invention. Figure 2 As shown, the method includes:

[0075] S201, performing compression and tension calibration tests on different pipe materials respectively, obtaining strength parameters and stress-strain curves of a plurality of the pipe materials, so as to determine a target pipe material from the plurality of the pipe materials.

[0076] In the embodiment of the present invention, the pipe material and wall thickness of the pipe are two influencing factors that control the overall strength of the pipe. The pipe material is relatively fixed, and the wall thickness can be adjusted according to actual needs. The pipe material of the pipe can be determined first, and then the wall thickness of the pipe can be designed according to the pipe-soil interaction. Therefore, before the landslide test, compression and tensile calibration tests can be performed on different pipe materials to determine the strength of different pipe materials, as well as parameters such as stress and strain. Among them, the target pipe material is determined according to actual needs, and the present invention does not make specific restrictions.

[0077] S202, burying a test pipe fitting cast by using the target pipe material in the test soil body to test the interaction between the test pipe fitting corresponding to the target pipe material and the test soil body.

[0078] After the pipe material is determined, the test pipe fittings cast from the pipe material are used for relevant tests. In the indoor simulation test, the mountain slope section is reduced to a test soil model for testing, so the test pipe fittings also need to be reduced according to the actual pipeline; thus, through the similar simulation method, the ratio of the test pipe fitting to the actual pipe diameter is determined based on the ratio of the height of the test soil to the height of the mountain slope section.

[0079] S203, in response to the triggering of the landslide test, controlling the inclination angle of the test box to change so that the slope of the test soil body changes, and collecting the first mechanical parameter and the second mechanical parameter during the change process until the inclination angle stops changing.

[0080] In the embodiment of the present invention, the test box is controlled to change from a low inclination angle to a high inclination angle, thereby making the slope of the test soil gradually change from gentle to steep, and collecting mechanical parameters during the change process. The inclination angle is set to a maximum inclination angle according to the slope of the actual mountain slope section. For example, if the maximum inclination angle of the mountain slope section is 40°, the sum of the slope of the test soil and the inclination angle of the test box is 40°, and the inclination angle stops changing.

[0081] Among them, the first mechanical parameters include the stress and strain of the test pipe fitting, and the deformation of the test pipe fitting; the second mechanical parameters include the soil pressure and deformation of the soil around the pipe, and the overall deformation of the test soil; the soil around the pipe is the soil located around the test pipe fitting.

[0082] S204, determining the first mechanical parameter and the second mechanical parameter in each landslide stage.

[0083] The landslide stage includes the initial small deformation stage, the uniform large deformation stage and the accelerated destruction stage of the test soil at the corresponding slope.

[0084] The landslide stages are divided according to the deformation state of the slope. In the initial small deformation stage of the slope, obvious cracks appear in the slope, and the soil deformation is initially large, but as time goes on, the deformation gradually tends to a normal state. In the uniform large deformation stage, the soil in the slope section continues to deform at a constant speed under the action of gravity. In the accelerated destruction stage, the deformation rate of the slope will gradually increase, and as time goes on, the deformation rate increase continues to expand until the entire slope becomes unstable and destroyed.

[0085] S205, determining a first mechanical change characteristic corresponding to each landslide stage based on the first mechanical parameter corresponding to the landslide stage, and determining a second mechanical change characteristic corresponding to the landslide stage based on the second mechanical parameter corresponding to the landslide stage.

[0086] S206: constructing the pipe-soil interaction model according to the first mechanical change characteristics and the second mechanical change characteristics respectively corresponding to each of the landslide stages.

[0087] Among them, the first mechanical change characteristics are the stress and strain change characteristics and deformation change characteristics of the test pipe at each landslide stage; the second mechanical change characteristics are the deformation mode and failure mode of the soil around the pipe at each landslide stage, and the deformation change characteristics of the slope as a whole at each landslide stage. Since there are differences in the mechanical properties between the test soil and the test pipe at each landslide stage, it is necessary to collect the first mechanical parameters and the second mechanical parameters of each landslide stage to determine the mechanical change characteristics of the test pipe and the test soil, especially the mechanical change characteristics of the soil around the pipe at each landslide stage; thus, the deformation mechanism of the pipeline at different slopes and different landslide stages can be determined according to the mechanical change characteristics, and a pipe-soil interaction model can be constructed; from the pipe-soil interaction model, the deformation mechanism of the pipeline, the strain of the limit and critical limit states, the soil pressure and deflection, etc. can be obtained, and the pipeline design based on the above parameters can be carried out. Among them, the pipe-soil interaction model is used to simulate the interaction between the pipeline and the soil in the mountain slope section environment.

[0088] It should be noted that the above three landslide stages are a general law followed by the deformation evolution of the slope under the action of gravity, that is, there are three landslide stages under different slopes. Therefore, when conducting tests with varying slopes, the mechanical parameters of the three landslide stages are actually measured separately under each slope to determine the deformation change characteristics, stress and strain change characteristics of the pipeline under different landslide stages, as well as the deformation change characteristics, stress and strain change characteristics and soil pressure change characteristics of the soil around the pipe. Therefore, the pipe-soil interaction model is constructed based on the mechanical change characteristics.

[0089] Specifically, the determining of the first mechanical change characteristic based on the first mechanical parameter includes: establishing a deformation curve according to the pipeline deformation at different landslide stages, and establishing a stress-strain curve according to the stress-strain parameters of the pipeline at different landslide stages, so as to obtain the deformation change law and stress-strain change law of the pipeline; the deformation change law and stress-strain change law of the pipeline are the mechanical change characteristics of the reaction test pipe under the action of landslide.

[0090] The determining of the second mechanical change characteristic based on the second mechanical parameter includes: establishing a deformation curve according to the deformation of the soil around the pipe at different landslide stages and establishing an earth pressure change curve according to the earth pressure of the soil around the pipe at different landslide stages, so as to obtain the earth pressure change law and deformation law of the soil around the pipe; the earth pressure change law and deformation law of the soil around the pipe reflect the mechanical change characteristics of the test soil under the action of landslide.

[0091] In some embodiments, in order to determine the position where the pipeline is subjected to the least stress according to the pipe-soil interaction model to improve the safety of the pipeline, the buried depth of the pipeline is changed to conduct a landslide test, and the pipe-soil interaction model at multiple buried depths is established; specifically, the steps include:

[0092] burying the test pipe at a preset depth in the test soil;

[0093] The landslide test is carried out on the test soil body in which the test pipe is buried at different preset depths to obtain the corresponding pipe-soil interaction model.

[0094] Among them, due to different buried depths, the test pipes are subjected to different forces, and the preset depth positions of multiple pipeline burials can be determined first; wherein the preset depth position can be determined based on the historical pipeline burial depth under similar terrain, or can be directly calculated based on the strength of the pipe material and the soil pressure of the slope section in the mountain area, and the present invention does not make specific restrictions. After determining the buried depth positions of multiple pipelines, multiple test models can be used respectively to bury the test pipes at multiple different depth positions in the test soil, and then conduct landslide experiments.

[0095] In some embodiments, in order to simplify the test process, multiple test pipes can be buried at different positions in the test soil, so that a model can be directly used to conduct a pipe-soil interaction test at the burial depth, and then the errors that may be caused by burying multiple test pipes can be corrected, thereby improving the test efficiency while ensuring accuracy.

[0096] The test method for pipe-soil interaction in a mountain slope section provided by an embodiment of the present invention uses a model to simulate the real environment of a mountain slope section, and then conducts a landslide test in the simulated environment and collects test data. Based on the collected data of landslide tests with different slopes, the interaction between the pipeline and the soil in the mountain slope section is simulated, and a pipe-soil interaction model is constructed. Thus, by conducting a landslide test indoors simulating the real environment of a mountain slope section, a pipe-soil interaction model under the action of a landslide is obtained, so that the constructed pipe-soil interaction model is closer to the real result, thereby improving the safety of the oil and gas pipeline in the mountain slope section and avoiding the occurrence of pipeline rupture caused by landslide. At the same time, since the inclination angle of the test box can be directly changed in the embodiment of the present invention to change the slope of the test soil, landslide tests under different slopes can be carried out simultaneously, and pipe-soil test models under multiple slopes can be determined, thereby simplifying the test method.

[0097] Embodiment 2

[0098] Reference Figure 3 , Figure 3The schematic diagram of the structure of the test system for the pipe-soil action on the slope section of a mountain area provided by an embodiment of the present invention is shown. The test system is used to implement the test method described in any of the above embodiments, such as Figure 3 As shown, the test system comprises:

[0099] Pipeline landslide test platform 1 and detection device 2;

[0100] The pipeline landslide test platform 1 comprises: a test box 11 with an opening at the top, a lifting device 12 and a support platform 13; one end of the test box 11 is connected to the lifting device 12, and the other end is rotatably connected to a fixed support 131 on the support platform 13, so that the inclination angle of the test box 11 changes with the lifting and lowering of the lifting device 12; the test box 11 is used to hold test pipes 112 and test soil 111.

[0101] In some embodiments, continue to refer to Figure 3 The support platform 13 is further provided with a support column 132 , and the support column 132 is provided at one end away from the fixed support 131 to support the test box 11 when the test box 11 is in a horizontal state.

[0102] The lifting device 2 is a hydraulic rod, one retractable end of the hydraulic rod is fixedly connected to one end of the test box 11, and the other end of the hydraulic rod is connected to the support platform 13, so that the extension and retraction of the hydraulic rod can drive one end of the test box 11 to rise and fall, so that the inclination angle of the test box 11 changes.

[0103] Specifically, Figure 3 As shown, since one end of the test box 11 is movable, that is, it rises and falls with the extension and retraction of the hydraulic rod, and the other end is fixed at the position of the fixed support 131, when the hydraulic rod is extended and retracted, one end of the test box 11 will be driven to rise and fall, and the other end will rotate on the fixed support 131, thereby causing the test box 11 to tilt as a whole, and the angle between the bottom of the test box 11 and the horizontal plane is the inclination angle.

[0104] Among them, refer to Figure 4 and Figure 5 , Figure 4 The finite element geometric model diagram of the test box is shown. Figure 5 The structure of the test soil body 111 in the test box 11 is shown; Figure 4 It can be seen that the test soil 111 is accumulated at the rear position of the test box 11; Figure 5It can be seen that the test soil body 111 in the test box 11 includes a slope section 1111 and a slope top section 1112, wherein the slope top section 1112 is parallel to the bottom of the test box 11, and the slope section 1111 is close to the end where the test box 110 and the fixed support 131 are connected, so that the slope of the test soil body 111 changes with the inclination angle of the test box 11. Specifically, since the slope section 1111 is close to the side where the fixed support 131 is located, the actual inclination angle α of the test soil body is the sum of the slope angle of the test soil body 111 itself and the inclination angle of the test box 11, and thus, the slope of the test soil body 111 can be changed by changing the inclination angle of the test box 11.

[0105] In some embodiments, continue to refer to Figure 5 In order to realize the landslide test under different slopes, a sliding belt 113 is laid on the inner bottom of the test box 11, and the test soil 111 is accumulated on the surface of the sliding belt 113 to assist the test soil 111 to slide. Specifically, the main function of the sliding belt 113 is to reduce the friction at the bottom of the test soil 111, so that the test soil 111 is more likely to slide, thereby facilitating the implementation of the landslide test. The material of the sliding belt 113 is not specifically limited in the present invention, and it only needs to be able to reduce the friction.

[0106] In some embodiments, continue to refer to Figure 5 When the slope is relatively gentle, it is difficult for the test soil to slide. Therefore, a load-bearing baffle 114 is also provided inside the test box 11. The load-bearing baffle 114 is provided at an end away from the slope section 1111 and in contact with the test soil 111. The soil is filled in the gap area formed by the load-bearing baffle 114 and the test box 11 to apply thrust to the load-bearing baffle 114, so that the test soil 111 slides.

[0107] In an embodiment of the present invention, the detection device 2 includes a first detection device 21 (not shown in the figure) and a second detection device 22 (not shown in the figure); wherein the first detection device 21 is used to detect the overall deformation of the test soil, the deformation of the soil around the pipe and the deformation of the pipeline; the second detection device 22 is used to detect the stress and strain of the test pipe, the stress and strain of the soil around the pipe and the soil pressure of the soil around the pipe.

[0108] Among them, the first detection device 21 is arranged around the pipeline landslide test platform 1 to observe the deformation of the test soil and the deformation of the test pipe during the landslide process; the first detection device 21 at least includes: a total station, a displacement meter, a three-dimensional laser scanner, a PIV (Particle Image Velocimetry) device, and a steel tape measure; the second detection device 22 at least includes: a strain gauge and an earth pressure box.

[0109] The second detection device 22 is arranged inside the test soil body 11 to detect soil pressure, stress and strain inside the test soil body and stress and strain of the test pipe. The second detection device 22 at least includes: soil pressure box, strain gauge, etc.

[0110] In some embodiments, reference Figure 6 In order to make the deformation of the entire slope easier to measure, before the landslide test, a flexible paper strip observation net can be laid on the surface of the test soil 11 and slope displacement observation points can be evenly spaced to determine the displacement of the entire slope by observing the displacement of the paper strips.

[0111] In some embodiments, color powder may be added to the test soil body 11 to facilitate observation of the displacement of the test soil body 11, especially the soil around the pipe, so as to determine the deformation of the soil around the pipe under the action of landslide.

[0112] The test system for pipe-soil interaction in a mountain slope section provided by an embodiment of the present invention constructs a pipeline landslide test platform 1, constructs a test soil body 111 in a box 11 of the pipeline landslide test platform 1, and adjusts the inclination of the box 11 during the test by a lifting device 12, thereby adjusting the slope of the test soil body 111, so as to achieve the purpose of simulating the terrain of a mountain slope section; at the same time, the lifting device 12 in the pipeline landslide test platform 1 can realize stepless slope change, and landslide tests under different slopes can be realized by thrust change, thereby enabling landslide tests under different conditions to be carried out, so that the test results are closer to the real environment results and the test method is simple and easy to implement. The test system for pipe-soil interaction in a mountain slope section provided by an embodiment of the present invention is used to conduct tests to construct a pipe-soil interaction model, and the results obtained are closer to the real results, which can improve the reliability of pipeline design and thus improve the safety of oil and gas pipelines in mountain slope sections.

[0113] The following is an explanation of the use of the test system for the pipe-soil effect on the slope section of a mountain area with a specific example:

[0114] First, after determining the target pipe material from a variety of pipe materials through compression and tension calibration tests, a test pipe 112 cast with the target pipe material is buried inside the slope section 111 of the test soil body 111 to construct a test model in the test box 11 of the pipeline landslide test platform 1; the test model is used to simulate the real environment of the mountain slope section and the scene of the mountain slope section with buried pipelines. Among them, multiple different pipeline buried depth positions can be determined through historical buried depth data to determine the pipe-soil interaction at different pipeline buried depths.

[0115] Afterwards, when conducting a landslide test, the inclination angle of the test box 11 is adjusted from small to large by controlling the lifting device 12, so that the slope of the test soil body 111 changes with the inclination angle of the test box 11, and the detection device 2 is used to collect the first mechanical parameters of the test pipe 112 and the second mechanical parameters of the test soil body 111 in the three landslide stages of initial small deformation, uniform large deformation and accelerated destruction of the slope. Specifically, the first detection device 21 is used to collect the deformation values ​​of the top and front and rear sides of the test pipe 112 in the three landslide stages of initial small deformation, uniform large deformation and accelerated destruction of the slope, and the second detection device 22 is used to collect the horizontal, vertical and axial deformation values ​​of the body of the test pipe 112 in the three landslide stages of initial small deformation, uniform large deformation and accelerated destruction of the slope, and the soil pressure of the top and front and rear sides of the test pipe 112. Among them, since there are three landslide stages in the test soil with different slopes, during the experiment, it is necessary to collect the first mechanical parameters of the test pipe 112 and the second mechanical parameters of the test soil 111 in the three landslide stages under different slopes.

[0116] For example, in order to test the pipe-soil interaction in three slope conditions of 15° (gentle slope), 30° (slope), and 45° (steep slope) in a slope section in a mountainous area, the hydraulic rod of the lifting device 12 is adjusted to extend and retract, so that the slope of the test soil body 11 changes from 15° to 30° and then to 45°. At each slope, the first mechanical parameters of the three landslide stages, namely the initial small deformation stage of the slope, the uniform large deformation stage, and the accelerated destruction stage, as well as the second mechanical parameters are collected respectively; then the relevant mechanical parameters of the test pipe 112 and the test soil body 111 corresponding to the different landslide stages of the three slope shapes are obtained.

[0117] in, Figure 7 The test results of the pipe-soil interaction test method in the mountain slope section are shown in the figure. After the landslide test, the pipe was bent and deformed. Figure 7 The test pipe is dug out and the deformation of the pipe is measured using a tape measure. Figure 8 The schematic diagram of the deformation results of the test pipe shown in Figure 8It can be seen that the test tube has two bends, which divide the test tube into three sections. The length of the first section is 48 cm, and the lengths of the second and third sections are both 51 cm. The first bending angle is 18°, and the second bending angle is 15°.

[0118] Then, based on the collected mechanical parameters, the mechanical change characteristics of the test pipes, the mechanical change characteristics of the soil around the pipes, and the mechanical change characteristics of the slope as a whole in the three landslide stages under each slope were determined, and then the pipe-soil interaction model was constructed based on the above mechanical change characteristics. Thus, the interaction model between the pipeline and the soil in the mountain slope environment was obtained.

[0119] It should be noted that the various embodiments in this specification are described in a progressive manner, and each embodiment focuses on the differences from other embodiments. The same or similar parts between the various embodiments can be referenced to each other.

[0120] Although the preferred embodiments of the present invention have been described, those skilled in the art may make additional changes and modifications to these embodiments once they have learned the basic creative concept. Therefore, the appended claims are intended to be interpreted as including the preferred embodiments and all changes and modifications that fall within the scope of the embodiments of the present invention.

[0121] Finally, it should be noted that, in this article, the orientation or position relationship indicated by the terms "center", "up", "down", "left", "right", "vertical", "horizontal", "inside", "outside", etc. is based on the orientation or position relationship shown in the drawings, which is only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operate in a specific orientation, and therefore cannot be understood as a limitation of the present invention. In addition, relational terms such as "first" and "second" are only used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply that there is any such actual relationship or order between these entities or operations, nor can they be understood as indicating or implying relative importance. Moreover, the terms "include", "comprise" or any other variant thereof are intended to cover non-exclusive inclusion, so that a process, method, article or terminal device including a series of elements includes not only those elements, but also other elements not explicitly listed, or also includes elements inherent to such a process, method, article or terminal device. In the absence of further restrictions, the elements defined by the sentence "including one..." do not exclude the existence of other identical elements in the process, method, article or terminal device including the elements.

[0122] The above is a detailed introduction to the test method and system for the soil action of a slope section in a mountain area provided by the present invention. The principle and implementation method of the present invention are explained in this article using specific examples. The description of the above embodiments is only used to help understand the present invention, and the content of this specification should not be understood as limiting the present invention. At the same time, for those skilled in the art, according to the present invention, there will be different forms of changes in the specific implementation methods and application scopes. It is not necessary and impossible to list all the implementation methods here, and the obvious changes or modifications derived therefrom are still within the protection scope of the present invention.

Claims

1. A test method for pipe-soil action on slope sections in mountainous areas, characterized in that: The method comprises: The test pipe is buried in a test soil body; wherein the test soil body is constructed in a test box; In response to the triggering of the landslide test, the inclination angle of the test box is controlled to change so that the slope of the test soil body changes, and the first mechanical parameter and the second mechanical parameter are collected during the change process until the inclination angle stops changing; The first mechanical parameter includes the stress and strain of the test pipe and the deformation of the test pipe; the second mechanical parameter includes the soil pressure and deformation of the soil around the pipe and the overall deformation of the test soil; the soil around the pipe is the soil around the test pipe; Based on the first mechanical parameter and the second mechanical parameter, a pipe-soil interaction model is constructed; wherein the pipe-soil interaction model is used to simulate the interaction between the pipeline and the soil in the mountain slope section environment.

2. The test method for the pipe-soil effect in mountainous slope sections according to claim 1 is characterized in that: The constructing the pipe-soil interaction model based on the first mechanical parameter and the second mechanical parameter includes: Determine the first mechanical parameter and the second mechanical parameter in each landslide stage; wherein the landslide stage includes the initial small deformation stage, the uniform large deformation stage and the accelerated destruction stage of the test soil at the corresponding slope; Based on the first mechanical parameter corresponding to each of the landslide stages, determining the first mechanical change characteristic corresponding to the landslide stage, and based on the second mechanical parameter corresponding to each of the landslide stages, determining the second mechanical change characteristic corresponding to the landslide stage; The first mechanical change characteristics are the stress and strain change characteristics and deformation change characteristics of the test pipe at each landslide stage; the second mechanical change characteristics are the deformation mode and failure mode of the soil around the pipe at each landslide stage, and the deformation change characteristics of the slope as a whole at each landslide stage; the landslide stage includes the initial small deformation stage of the slope, the uniform large deformation stage and the accelerated failure stage; The pipe-soil interaction model is constructed according to the first mechanical change characteristics and the second mechanical change characteristics respectively corresponding to each of the landslide stages.

3. The test method for the pipe-soil effect in mountainous slope sections according to claim 1 is characterized in that: The step of burying the test pipe in the test soil comprises: burying the test pipe at a preset depth in the test soil; The method further comprises: The landslide test is carried out on the test soil body in which the test pipe is buried at different preset depths to obtain the corresponding pipe-soil interaction model.

4. The test method for the pipe-soil effect in mountainous slope sections according to claim 1 is characterized in that: Before burying the test pipe in the test soil, the method further includes: Performing compression and tension calibration tests on different pipe materials respectively, obtaining strength parameters and stress-strain curves of a plurality of the pipe materials, so as to determine a target pipe material from the plurality of the pipe materials; The step of burying the test pipe in the test soil comprises: A test pipe fitting cast with the target pipe material is buried in the test soil body to test the interaction between the test pipe fitting corresponding to the target pipe material and the test soil body.

5. A test system for pipe-soil action in mountainous slope sections, characterized in that: The test system is used to implement the test method described in any one of claims 1 to 4 above, and the test system includes: Pipeline landslide test platform and detection device; The pipeline landslide test platform comprises: a test box with an opening at the top, a lifting device and a support platform; one end of the test box is connected to the lifting device, and the other end is rotatably connected to a fixed support on the support platform, so that the inclination angle of the test box changes with the lifting of the lifting device; the test box is used to hold test pipes and test soil; The detection device is used to collect a first mechanical parameter and a second mechanical parameter; wherein the first mechanical parameter includes the stress and strain of the test pipe and the deformation of the test pipe; the second mechanical parameter includes the soil pressure and deformation of the soil around the pipe and the overall deformation of the test soil; the soil around the pipe is the soil located around the test pipe.

6. The test system for soil-pipe action in mountainous slope sections according to claim 5 is characterized in that: The lifting device is a hydraulic rod, one retractable end of the hydraulic rod is fixedly connected to one end of the test box, and the other end of the hydraulic rod is connected to the support platform, so that the extension and retraction of the hydraulic rod can drive one end of the test box to rise and fall, so that the inclination angle of the test box changes.

7. The test system for soil-pipe action in mountainous slope sections according to claim 5 is characterized in that: The test soil body includes a slope section and a slope top section, wherein the slope top section is parallel to the bottom of the test box, and the slope section is close to one end of the test box connected to the fixed support, so that the slope of the test soil body changes with the inclination angle of the test box.

8. The test system for soil-pipe action in mountainous slope sections according to claim 5 is characterized in that: A sliding belt is laid on the inner bottom of the test box, and the test soil is accumulated on the surface of the sliding belt to assist the test soil in causing landslide.

9. The test system for soil-pipe action in mountainous slope sections according to claim 8 is characterized in that: The test soil body includes a slope section and a slope top section; a load-bearing baffle is also provided inside the test box, and the load-bearing baffle is provided at one end away from the slope section and in contact with the test soil body; Wherein, soil is filled in the gap area formed by the load-bearing baffle and the test box to apply thrust to the load-bearing baffle, so as to cause the test soil to slide.

10. The test system for soil-pipe action in mountainous slope sections according to claim 5, characterized in that: The detection device includes a first detection device and a second detection device; wherein the first detection device is used to detect the overall deformation of the test soil, the deformation of the soil around the pipe and the deformation of the pipeline; the second detection device is used to detect the stress and strain of the test pipe, the stress and strain of the soil around the pipe and the soil pressure of the soil around the pipe.

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