Soil gas-induced liquefaction test device and test method

Abstract

The invention discloses a soil gas-induced liquefaction test device and a test method, and relates to the field of soil liquefaction test equipment. According to the device, the sample cylinder is filled with sample soil and water, gas is continuously supplied into the sample cylinder through the gas supply mechanism, and the gas continuously seeps upwards along the sample cylinder, so that the seepage impact state of natural gas on the seabed sand soil layer is simulated, and meanwhile, the air pressure of the gap of the sand soil layer is detected through the air pressure detection mechanism; therefore, the soil liquefaction degree of the sandy soil layer under the corresponding air pressure can be obtained by observing the state of the sandy soil layer during gas seepage impact, and data support is provided for monitoring and prevention of soil gas-induced liquefaction of a seabed natural gas layer. The air distribution structure is arranged at the bottom end of the sandy soil layer in the sample cylinder and is communicated with the air supply assembly through the air pressure regulating valve, and when the air supply assembly supplies air into the sample cylinder, the air pressure regulating valve can perform constant-pressure regulation on the air pressure in the air distribution structure, so that the influence of air pressure fluctuation on the test process is prevented, and the test accuracy is improved.

Description

TECHNICAL FIELD

[0001] The application belongs to the field of soil liquefaction test equipment, in particular, relates to a soil gas-induced liquefaction test device and a test method. BACKGROUND

[0002] Ocean natural gas is a mixture of hydrocarbons existing in the sandstone of seabed, mainly in the form of free gas and solid hydrate. Among them, the sand layer is the main gas storage layer of the seabed shallow gas. With the continuous release of natural gas, the pore pressure of sand will increase, resulting in zero effective stress of soil and loss of bearing capacity (i.e. soil liquefaction). The liquefied sand is like a fluid, which produces buoyancy on the buried pipeline, causing the pipeline to float or sink, causing the pipeline to bend and break, affecting the normal mining process of natural gas, and may also cause seabed landslide and collapse, causing marine geological disasters, so it is very important to monitor and prevent soil gas-induced liquefaction. Based on this, the application provides a soil gas-induced liquefaction test device and a test method to simulate the soil gas-induced liquefaction and provide data support for the monitoring and prevention of soil gas-induced liquefaction. SUMMARY

[0003] In view of the problems in the related art, the application provides a soil gas-induced liquefaction test device and a test method to overcome the above technical problems existing in the prior art.

[0004] To solve the above technical problems, the application is realized by the following technical scheme: The application is a soil gas-induced liquefaction test device, which comprises a test table and a test sample cylinder placed on the test table, the inside of the test sample cylinder is filled with test sample soil to form a sand layer, the bottom end of the sand layer is provided with a gas distribution structure, and the inside of the test sample cylinder is further provided with a water accumulation layer which overflows the sand layer; The application further comprises a gas supply mechanism and a gas pressure detection mechanism, the gas supply mechanism comprises a gas supply assembly and a gas pressure regulating valve, the gas supply assembly is communicated with the gas distribution structure in the inside of the test sample cylinder through the gas pressure regulating valve, so that the gas supply assembly can supply gas to the inside of the test sample cylinder through the gas pressure regulating valve and the gas distribution structure, and the gas pressure regulating valve can regulate the gas pressure in the gas distribution structure to form a constant pressure boundary at the bottom end of the inside of the test sample cylinder; The gas pressure detection mechanism is communicated with the sand layer in the test sample cylinder, so that the gas pressure detection mechanism can detect the soil interstitial gas pressure in the sand layer.

[0005] Further, the test sample cylinder comprises a cylinder body and a base, the cylinder body is fixedly installed on the top surface of the base, a gas distribution cavity is formed in the inside of the base, a plurality of gas distribution holes are arranged at the top end of the gas distribution cavity and communicated with the inside of the cylinder body, a gas inlet is fixedly installed on one side of the base and communicated with the gas distribution cavity, and the gas inlet end is communicated with the gas pressure regulating valve.

[0006] Further, the air distribution structure comprises a gravel layer, which is filled in the bottom end of the cylinder body, and the top surface of the gravel layer is paved with a waterproof air-permeable film.

[0007] Further, the side surface of the cylinder body is connected to install a plurality of air pressure detection interfaces which are uniformly distributed from bottom to top, the inner side end of the air pressure detection interface is installed with a filter film, and the outer side end of the air pressure detection interface is in communication with an air pressure detection mechanism.

[0008] Further, the air supply assembly comprises an air compressor, the air compressor is provided with an air supply interface, the air supply interface is installed with an air supply valve, and one end of the air supply interface is connected to install an air distribution conduit.

[0009] Further, the air pressure regulating valve comprises a valve body, one end of the valve body is in communication with the air distribution conduit, the other end of the valve body is connected with a gas delivery conduit, one end of the gas delivery conduit is in communication with the air distribution structure inside the sample cylinder; The inside of the valve body is provided with a gas guide pipe for cutting off the air inlet and outlet ends, the gas guide pipe is provided with a gas guide hole, the valve core is sealingly abutted in the gas guide hole, the valve core is fixedly installed with a valve rod, the top end of the valve body is provided with a constant pressure regulating unit connected with the valve rod, and the constant pressure regulating unit can drive the valve rod and the valve core to move up and down according to the air pressure of the air outlet end of the valve body, so as to adjust the opening size of the gas guide hole.

[0010] Further, the constant pressure regulating unit comprises an air pressure regulating chamber, a flexible diaphragm is fixedly installed in the inside of the air pressure regulating chamber, the flexible diaphragm divides the inside of the air pressure regulating chamber into an upper chamber and a lower chamber, and the lower chamber is in communication with the air outlet end of the valve body through an air pressure balance conduit; A center plate is fixedly installed on the flexible diaphragm, the bottom end of the center plate is fixedly connected with the top end of the valve rod, and the top end of the center plate is abutted to be provided with a pressure spring in the upper chamber.

[0011] Further, the top end of the air pressure regulating chamber is fixedly installed with a limiting sleeve, the air pressure regulating plate is slidingly installed in the inside of the limiting sleeve, the air pressure regulating plate is abutted to the top end of the pressure spring, and the limiting sleeve is also installed with an adjusting driving piece which can drive the air pressure regulating plate to adjust up and down; The adjusting driving piece comprises a threaded sleeve, the threaded sleeve is fixedly installed at the top end of the limiting sleeve, an air pressure adjusting rod is screwedly and drivably installed in the inside of the threaded sleeve, the top end of the air pressure adjusting rod is fixedly installed with an air pressure adjusting handle, and the lower end of the air pressure adjusting rod is fixedly connected with the air pressure regulating plate. The top end of the center plate is fixedly installed with a limiting shaft, and the bottom end of the air pressure adjusting rod is slidingly inserted into the top end of the limiting shaft.

[0012] Further, the air pressure detection mechanism comprises a support fixedly installed on the top surface of the test table, a plurality of air pressure detectors fixedly installed on the support, and an air pressure detection guide pipe connected to the detection port of each air pressure detector and in communication with the sample cylinder.

[0013] The application further discloses a soil body gas-induced liquefaction test method, and the specific steps are as follows. The sample soil is filled into the sample cylinder to form a sand layer, and water is injected into the sample cylinder, so that the water level submerges above the sand layer; Then, the gas supply assembly is started to supply gas to the gas distribution structure at the bottom end of the sample cylinder through the air pressure regulating valve, so that the gas seeps upward through the soil gaps of the sand layer to impact the soil, and the air pressure detection mechanism detects the air pressure in the soil gaps in the sample cylinder; The state of the sand layer under the gas seepage impact is observed to determine the liquefaction degree of the soil.

[0014] The application has the following beneficial effects: 1. In the application, the sample soil and water are filled into the sample cylinder, and the gas supply mechanism continuously supplies gas into the sample cylinder, so that the gas continuously seeps upward along the sample cylinder, thereby simulating the seepage impact state of the natural gas on the seabed sand layer, and the air pressure detection mechanism detects the air pressure in the sand layer gaps, so that the liquefaction degree of the soil in the sand layer under the corresponding air pressure can be obtained by observing the state of the sand layer under the gas seepage impact, data support is provided for the monitoring and prevention of the soil body gas-induced liquefaction of the seabed natural gas layer, and the exploitation of the natural gas and the occurrence of marine geological disasters caused by the liquefaction of the soil are prevented.

[0015] 2. In the application, the gas distribution structure is arranged at the bottom end of the sand layer in the sample cylinder, and the gas distribution structure is in communication with the gas supply assembly through the air pressure regulating valve, so that when the gas supply assembly supplies gas into the sample cylinder, the air pressure regulating valve can constantly regulate the air pressure in the gas distribution structure, so that a constant pressure boundary is formed at the bottom end in the sample cylinder, thereby preventing the air pressure fluctuation from affecting the test progress, and the test accuracy is improved.

[0016] Of course, it is not necessary for any product implementing the present application to achieve all the advantages mentioned above. BRIEF DESCRIPTION OF DRAWINGS

[0017] In order to more clearly illustrate the technical solutions of the embodiments of the application, the following will briefly introduce the drawings needed to be used in the embodiment description. Obviously, the drawings in the following description are only some embodiments of the application, and for those skilled in the art, the drawings obtained from these drawings can also be obtained without creative labor.

[0018] Figure 1It is a three-dimensional structure schematic view of the soil gas-induced liquefaction test device of the present application; Figure 2 It is a three-dimensional structure schematic view of the soil gas-induced liquefaction test device of the present application; Figure 1 It is a three-dimensional structure schematic view of the soil gas-induced liquefaction test device of the present application; Figure 3 It is a three-dimensional structure schematic view of the soil gas-induced liquefaction test device of the present application; Figure 1 It is a three-dimensional structure schematic view of the soil gas-induced liquefaction test device of the present application; Figure 4 It is a three-dimensional structure schematic view of the soil gas-induced liquefaction test device of the present application; Figure 5 It is a three-dimensional structure schematic view of the soil gas-induced liquefaction test device of the present application; Figure 4 It is a three-dimensional structure schematic view of the soil gas-induced liquefaction test device of the present application; Figure 6 It is a three-dimensional structure schematic view of the soil gas-induced liquefaction test device of the present application; Figure 4 It is a three-dimensional structure schematic view of the soil gas-induced liquefaction test device of the present application; Figure 7 It is a three-dimensional structure schematic view of the soil gas-induced liquefaction test device of the present application; Figure 8 It is a three-dimensional structure schematic view of the soil gas-induced liquefaction test device of the present application; Figure 9 It is a three-dimensional structure schematic view of the soil gas-induced liquefaction test device of the present application; Figure 8 It is a three-dimensional structure schematic view of the soil gas-induced liquefaction test device of the present application; Figure 10 It is a three-dimensional structure schematic view of the soil gas-induced liquefaction test device of the present application; Figure 11 It is a three-dimensional structure schematic view of the soil gas-induced liquefaction test device of the present application; Figure 10 It is a three-dimensional structure schematic view of the soil gas-induced liquefaction test device of the present application.

[0019] In the figure: 1, test table; 2, test sample cylinder; 21, cylinder body; 22, base; 23, gas inlet interface; 24, gas pressure detection interface; 25, gas distribution cavity; 26, gas distribution hole; 27, gravel layer; 28, waterproof and breathable film; 29, filter membrane; 3, gas supply mechanism; 31, air compressor; 32, gas distribution conduit; 33, gas delivery conduit; 34, valve body; 35, gas pressure balance conduit; 36, gas pressure adjustment chamber; 37, gas pressure adjustment handle; 38, gas supply interface; 39, gas supply valve; 310, gas guide pipe; 311, gas guide hole; 312, valve core; 313, valve stem; 314, flexible diaphragm; 315, center plate; 316, pressure spring; 317, limiting shaft; 318, gas pressure adjustment rod; 319, gas pressure adjustment plate; 320, limiting sleeve; 321, threaded sleeve; 4, gas pressure detection mechanism; 41, gas pressure detector; 42, support; 43, gas pressure detection conduit. DETAILED DESCRIPTION

[0020] With reference to the drawings of the embodiments of the application, the technical solutions in the embodiments of the application will be clearly and completely described. Obviously, the described embodiments are only a part of the embodiments of the application, but not all the embodiments of the application. Based on the embodiments of the application, all other embodiments obtained by a person of ordinary skill in the art without creative work fall within the protection scope of the application.

[0021] In the description of the application, it should be understood that the terms "opening", "upper", "lower", "top", "middle", "inner" and the like indicate the orientation or positional relationship, and are only used to facilitate the description of the application and simplify the description, and do not indicate or imply that the referred components or elements must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as a limitation of the application.

[0022] Embodiment one

[0023] Please refer to Figures 1-3 As shown in the drawings, the application is a soil gas-induced liquefaction test device, which comprises a test table 1 and a test sample cylinder 2 placed on the test table 1. The inside of the test sample cylinder 2 is filled with test sample soil to form a sand soil layer. The bottom end of the sand soil layer is provided with a gas distribution structure. The inside of the test sample cylinder 2 is also provided with a water accumulation layer that overflows the sand soil layer. The device also comprises a gas supply mechanism 3 and a gas pressure detection mechanism 4. The gas supply mechanism 3 comprises a gas supply assembly and a gas pressure regulating valve. The gas supply assembly is in communication with the gas distribution structure inside the test sample cylinder 2 through the gas pressure regulating valve, so that the gas supply assembly can supply gas to the inside of the test sample cylinder 2 through the gas pressure regulating valve and the gas distribution structure. The gas pressure regulating valve can regulate the gas pressure in the gas distribution structure to form a constant pressure boundary at the bottom end of the test sample cylinder 2. The gas pressure detection mechanism 4 is in communication with the sand soil layer in the test sample cylinder 2, so that the gas pressure detection mechanism 4 can detect the soil interstitial gas pressure in the sand soil layer. During the experiment, the gas supply assembly is turned on to supply gas to the gas distribution structure at the bottom end of the test sample cylinder 2 through the gas pressure regulating valve. Then the gas in the gas distribution structure seeps upward through the soil interstices of the sand soil layer to impact the soil. At the same time, the soil interstitial gas pressure in the test sample cylinder 2 is detected by the gas pressure detection mechanism 4. The state of the sand soil layer under the impact of gas seepage is observed to determine the degree of soil liquefaction.

[0024] The gas-induced liquefaction test can obtain the degree of soil liquefaction of the sand soil layer under the corresponding gas pressure, providing data support for the monitoring and prevention of soil gas-induced liquefaction of the seabed natural gas layer, preventing the impact of soil liquefaction on natural gas exploitation and marine geological disasters. The gas pressure in the gas distribution structure can be regulated by the gas pressure regulating valve to form a constant pressure boundary at the bottom end of the test sample cylinder 2, thereby preventing fluctuations in gas pressure from affecting the test process and improving the accuracy of the test.

[0025] Embodiment two

[0026] Please refer to Figure 1、 Figure 2 、 Figure 8 、 Figure 9 As shown, the difference between this embodiment and the above embodiment is that the sample tube 2 includes a cylinder 21 and a base 22, the cylinder 21 is fixedly installed on the top surface of the base 22, an air distribution cavity 25 is opened inside the base 22, and a plurality of air distribution holes 26 connected to the interior of the cylinder 21 are provided at the top of the air distribution cavity 25, and an air inlet interface 23 connected to the air distribution cavity 25 is fixedly installed on one side of the base 22, and the air inlet end of the air inlet interface 23 is connected to the air pressure regulating valve; the air distribution structure includes a gravel layer 27, the gravel layer 27 is filled at the bottom end of the cylinder 21, and the top surface of the gravel layer 27 is covered with a waterproof and breathable membrane 28.

[0027] When the gas enters the air distribution cavity 25 through the air inlet port 23, it is evenly distributed into the gravel layer 27 through the air distribution holes 26, and finally enters the sand layer inside the cylinder 21 through the waterproof breathable membrane 28. It overflows and is transported upward along the gaps in the soil layer, causing the soil to gradually liquefy. Among them, through the cooperation of the air distribution cavity 25 and the gravel layer 27, the gas can be evenly distributed at the bottom of the cylinder 21, and then the gas can evenly seep into the sand layer to simulate the state of the seabed sand layer being impacted by natural gas, thereby improving the experimental accuracy, and the waterproof and breathable membrane 28 can prevent the water in the cylinder 21 from flowing back downward.

[0028] Example 3

[0029] See also Figures 1-3 、 Figure 4 、 Figure 6 、 Figure 10 、 Figure 11 As shown, the difference between this embodiment and the above embodiment is that the air supply component includes an air compressor 31, the air compressor 31 is provided with an air supply interface 38, the air supply interface 38 is installed with an air supply valve 39, one end of the air supply interface 38 is connected to the air distribution pipe 32; the air pressure regulating valve includes a valve body 34, one end of the valve body 34 is connected to the air distribution pipe 32, the other end of the valve body 34 is connected to the gas delivery pipe 33, one end of the gas delivery pipe 33 is connected to the air distribution pipe 32 inside the sample tube 2. The valve body 34 is connected with the structure; the interior of the valve body 34 is provided with an air guide pipe 310 for isolating the air inlet and outlet ends, and the air guide pipe 310 is provided with an air guide hole 311, and the air guide hole 311 is sealed with a valve core 312, and the valve core 312 is fixedly mounted with a valve stem 313. The top of the valve body 34 is provided with a constant pressure regulating unit connected to the valve stem 313, and the constant pressure regulating unit can drive the valve stem 313 and the valve core 312 to move up and down according to the air pressure at the air outlet end of the valve body 34 to adjust the opening size of the air guide hole 311.

[0030] During the test, the air supply valve 39 is opened, allowing the air compressor 31 to supply air into the sample tube 2 through the air supply interface 38, the air distribution duct 32, the air pressure regulating valve, and the gas delivery duct 33. When the air flows through the air pressure regulating valve, the air is delivered from the air inlet end of the valve body 34 to the air outlet end of the valve body 34 through the air guide hole 311 on the air guide tube 310. Since the air outlet end of the valve body 34 is connected to the air distribution structure inside the sample tube 2, when the air pressure inside the sample tube 2 fluctuates, the air pressure at the air outlet end of the valve body 34 changes synchronously. At this time, the constant pressure regulating unit can drive the valve stem 313 and the valve core 312 to move up and down according to the air pressure at the air outlet end of the valve body 34 to adjust the opening size of the air guide hole 311. Specifically, when the air pressure of the air distribution structure inside the sample tube 2 increases, the constant pressure regulating unit drives the valve stem 313 and the valve core 312 to move upward, seals and shrinks the opening of the air guide hole 311, and adjusts and lowers the air pressure inside the air distribution structure by reducing the air delivery volume. Correspondingly, when the air pressure of the air distribution structure inside the sample tube 2 decreases, the constant pressure regulating unit drives the valve stem 313 and the valve core 312 to move downward, adjusts and increases the opening of the air guide hole 311, and adjusts and raises the air pressure inside the air distribution structure by increasing the air delivery volume. By dynamically adjusting the air pressure inside the air distribution structure, the air pressure inside the air distribution structure is close to a constant pressure stable state, so that a constant pressure boundary is formed at the bottom end inside the sample tube 2, thereby preventing air pressure fluctuations from affecting the test process, which is beneficial to improving the test accuracy.

[0031] Example 4

[0032] See also Figure 5 、 Figure 6 、 Figure 10 、 Figure 11 As shown, the difference between this embodiment and the above embodiment is that the constant pressure regulating unit includes an air pressure regulating chamber 36, and a flexible diaphragm 314 is fixedly installed inside the air pressure regulating chamber 36. The flexible diaphragm 314 divides the interior of the air pressure regulating chamber 36 into an upper chamber and a lower chamber, and the lower chamber is connected to the air outlet end of the valve body 34 through an air pressure balance conduit 35; a center plate 315 is fixedly installed on the flexible diaphragm 314, and the bottom end of the center plate 315 is fixedly connected to the top end of the valve stem 313, and the top end of the center plate 315 is abutted against a pressure spring 316 located in the upper chamber.

[0033] During the test, the center plate 315, the valve rod 313 and the valve core 312 are driven by the elastic force of the pressure spring 316 to move downward, so that the air guide hole 311 is opened, air is transported into the sample cylinder 2, the air at the air outlet end of the valve body 34 is transported into the lower chamber of the air pressure adjusting chamber 36 through the air pressure balance conduit 35, and the flexible diaphragm 314 is extruded and deformed upward until the air pressure in the lower chamber is balanced with the air pressure at the air outlet end of the valve body 34, at which time the air transportation speed of the air guide hole 311 is balanced with the upward air transportation speed of the air distribution structure in the sample cylinder 2, so that the air pressure in the air distribution structure is in a dynamic balance state, and when the air pressure in the air distribution structure fluctuates, the air pressure at the air outlet end of the valve body 34 and the air pressure in the lower chamber of the air pressure adjusting chamber 36 fluctuate synchronously; Specifically, if the air pressure in the air distribution structure increases, the air pressure at the air outlet end of the valve body 34 and the air pressure in the lower chamber of the air pressure adjusting chamber 36 increase synchronously, so that the air pressure in the lower chamber extrudes and abuts against the flexible diaphragm 314 to deform upward, at which time the flexible diaphragm 314 drives the center plate 315, the valve rod 313 and the valve core 312 to move upward, so that the opening of the air guide hole 311 is reduced, the air transportation speed into the air distribution structure is reduced, and the air pressure in the air distribution structure gradually decreases to the original air pressure. Correspondingly, if the air pressure in the air distribution structure decreases, the air pressure at the air outlet end of the valve body 34 and the air pressure in the lower chamber of the air pressure adjusting chamber 36 decrease synchronously, so that the air pressure in the lower chamber extrudes and abuts against the flexible diaphragm 314 to deform upward, and the center plate 315, the valve rod 313 and the valve core 312 are driven by the elastic force of the pressure spring 316 to move downward, so that the opening of the air guide hole 311 is increased, the air transportation speed into the air distribution structure is increased, and the air pressure in the air distribution structure gradually increases to the original air pressure. Through the cooperation of the pressure spring 316, the flexible diaphragm 314, the air pressure adjusting chamber 36 and the air pressure balance conduit 35, the constant pressure regulation of the air pressure in the air distribution structure can be automatically realized, the air pressure fluctuation is reduced, and the experimental precision is improved.

[0034] Further, the top end of the air pressure adjusting chamber 36 is fixedly installed with a limiting sleeve 320, the limiting sleeve 320 is slidably installed with an air pressure adjusting plate 319 inside, the air pressure adjusting plate 319 abuts against the top end of the pressure spring 316, and the limiting sleeve 320 is further installed with an adjusting driving part which can drive the air pressure adjusting plate 319 to ascend and descend; the adjusting driving part comprises a threaded sleeve 321 fixedly installed at the top end of the limiting sleeve 320, the threaded sleeve 321 is internally and threadedly drivenly installed with an air pressure adjusting rod 318, the top end of the air pressure adjusting rod 318 is fixedly installed with an air pressure adjusting handle 37, and the lower end of the air pressure adjusting rod 318 is fixedly connected with the air pressure adjusting plate 319; the top end of the center plate 315 is fixedly installed with a limiting shaft 317, and the bottom end of the air pressure adjusting rod 318 is slidably inserted into the top end of the limiting shaft 317. Wherein, by adjusting the driving member to lift the air pressure adjusting plate 319, the extension length of the pressure spring 316 can be adjusted accordingly, so as to adjust the downward force of the pressure spring 316 on the flexible diaphragm 314, the center plate 315, the valve rod 313 and the valve core 312, and then adjust the opening size of the air guide hole 311 and the air pressure in the sample cylinder 2, so as to carry out the gas liquefaction test under different air pressures and improve the reliability of experimental data. Specifically, when it is necessary to adjust and reduce the test air pressure in the sample cylinder 2, the air pressure adjusting handle 37 drives the air pressure adjusting rod 318 to rotate, so as to drive the air pressure adjusting rod 318 to move upward along the threaded sleeve 321 through threaded transmission, so that the air pressure adjusting rod 318 drives the air pressure adjusting plate 319 to move upward, at this time, the pressure spring 316 is elongated to reduce the downward force on the flexible diaphragm 314, the center plate 315, the valve rod 313 and the valve core 312, so that the flexible diaphragm 314 drives the center plate 315, the valve rod 313 and the valve core 312 to move upward, so as to adjust and reduce the opening size of the air guide hole 311 and the air pressure in the sample cylinder 2. Correspondingly, when it is necessary to adjust and increase the test air pressure in the sample cylinder 2, the air pressure adjusting handle 37 drives the air pressure adjusting rod 318 to rotate in the opposite direction, so as to drive the air pressure adjusting rod 318 to move downward along the threaded sleeve 321 through threaded transmission, so that the air pressure adjusting rod 318 drives the air pressure adjusting plate 319 to move downward, at this time, the pressure spring 316 is contracted to increase the downward force on the flexible diaphragm 314, the center plate 315, the valve rod 313 and the valve core 312, so that the flexible diaphragm 314, the center plate 315, the valve rod 313 and the valve core 312 are driven to move downward, so as to adjust and increase the opening size of the air guide hole 311 and the air pressure in the sample cylinder 2.

[0035] Example five

[0036] Please refer to Figure 1 , Figure 2 , Figure 4 , Figure 5 , Figures 7-9 The difference between the present embodiment and the above-mentioned embodiments is that a plurality of air pressure detection interfaces 24 are uniformly distributed from bottom to top on the side surface of the cylinder body 21, a filter membrane 29 is installed on the inner side end of the air pressure detection interface 24, and the outer side end of the air pressure detection interface 24 is in communication with the air pressure detection mechanism 4; the air pressure detection mechanism 4 comprises a support 42, which is fixedly installed on the top surface of the test bench 1, and a plurality of air pressure detectors 41 are fixedly installed on the support 42, and an air pressure detection guide pipe 43 is connected and installed on the detection port of each air pressure detector 41, and one end of the air pressure detection guide pipe 43 is in communication with the sample cylinder 2.

[0037] The filter membrane 29 can isolate and filter the sand in the sample cylinder 2, preventing the sand from blocking the air pressure detection interface 24. The air pressure detector 41 is installed on the support 42, so that the height of the air pressure detector 41 is higher than the height of the sample cylinder 2. During the test, the water in the cylinder body 21 first seeps into the corresponding air pressure detection conduit 43 through the air pressure detection interface 24. At this time, because the height of the air pressure detector 41 is higher than the height of the sample cylinder 2 and the internal liquid level, the water in the air pressure detection conduit 43 will not flow to the air pressure detector 41, causing the air pressure detector 41 to be damaged by water. During the air inlet test, the air in the soil gap can be transported to the corresponding air pressure detection conduit 43 through the air pressure detection interface 24, so that the air pressure in the air pressure detection conduit 43 gradually increases, and the water in the air pressure detection conduit 43 is pressed back to flow into the cylinder body 21. When the air pressure detection conduit 43 is completely filled with gas, the air pressure value detected by the air pressure detector 41 is the air pressure value of the soil gap at the height of the sand layer. By arranging a plurality of air pressure detection interfaces 24 with different heights on the cylinder body 21, the air pressure at different heights in the sand layer can be detected, the air pressure detection precision can be improved, and the experimental data accuracy can be improved.

[0038] Example six

[0039] The embodiment discloses a soil gas-induced liquefaction test method, and the specific steps are as follows: Fill the sample soil into the sample cylinder 2 to form a sand layer, and then inject water into the sample cylinder 2, so that the water level is submerged above the sand layer; Then, the gas supply assembly is started to supply gas to the gas distribution structure at the bottom end of the sample cylinder 2 through the gas pressure regulating valve, so that the gas seeps upward through the soil gap of the sand layer to impact the soil. At the same time, the soil gap air pressure in the sample cylinder 2 is detected by the air pressure detection mechanism 4. Observe the state of the sand layer when the gas seeps and impacts, and determine the liquefaction degree of the soil.

[0040] Furthermore, the test uses special sand for sand filling, the natural water content of which is ≤1%, the natural dry density is 1.52 g / cm 3 , the relative density of soil particles is 2.54 g / cm 3 , the particle size is 0.3 mm~0.6 mm, and the minimum dry density measured by the funnel method and the measuring cylinder method is 1.428 g / cm 3 , and the maximum dry density measured by the vibration hammering method is 1.584 g / cm 3 .

[0041] The inner diameter of the sample cylinder 2 is 0.1 m, and the height is 0.6 m. During the test, the sand sample is filled in 5 layers, each layer is 8 cm, and the mass of each layer of sand sample is 0.974 kg. Before filling, prepare a suitable amount of degassed water (boil for 15 min, cool and use), then boil each portion of sand sample in water for 30 min and cool, then add 1 / 5 sample height of degassed water in the sample cylinder 2, fill the sand sample with a long spoon, and use a 4 mm diameter metal rod to uniformly vibrate and use a wooden hammer to knock the cylinder wall, control the relative density to be 80%, and the dry density to be 1.55 g / cm 3 At this time, the buoyant density of the soil is 9.4 kN / m 3 , and the water content is 25.2%. After filling the first layer of sand sample, inject the degassed water to 2 / 5 of the sample height, then load the second layer of sand sample, until the predetermined height is reached, and finally leave a water level of 10 cm at the top of the soil column. This method can ensure that the soil is in a completely saturated state, thereby improving the accuracy of the experiment.

[0042] During the test, the gas injection mechanism 3 is injected for about 30 min, and the test phenomenon is photographed, and the gas pressure value measured by the gas pressure detector 41 is recorded. Finally, the liquefaction degree of the soil under different gas pressures is determined by photographing the sand layer shape.

[0043] In the description of the present specification, the description of the terms "one embodiment", "example", "specific example", etc. means that the specific features, structures, materials or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the invention. In the present specification, the illustrative description of the above terms does not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described can be combined in any one or more embodiments or examples in a suitable manner.

[0044] The preferred embodiments of the above disclosed invention are only used to help explain the invention. The preferred embodiments do not describe all the details, nor limit the invention to the specific embodiments described. Obviously, many modifications and changes can be made according to the content of the present specification. The present specification selects and specifically describes these embodiments in order to better explain the principles and practical applications of the invention, so that those skilled in the art can well understand and utilize the invention.

Claims

1. A soil gas-induced liquefaction test device, comprising a test bench and a sample tube placed on the test bench, characterized in that: The interior of the sample tube is filled with sample soil to form a sand layer, the bottom of the sand layer is provided with an air distribution structure, and the interior of the sample tube is also provided with a water accumulation layer overflowing the sand layer; The apparatus further comprises an air supply mechanism and an air pressure detection mechanism, wherein the air supply mechanism comprises an air supply assembly and an air pressure regulating valve, wherein the air supply assembly is connected to an air distribution structure inside the sample tube via the air pressure regulating valve, so that the air supply assembly can supply air to the inside of the sample tube via the air pressure regulating valve and the air distribution structure, and the air pressure regulating valve can regulate the air pressure in the air distribution structure to a constant pressure, so that a constant pressure boundary is formed at the bottom end of the inside of the sample tube; The air pressure detection mechanism is communicated with the sand layer in the sample tube, so that the air pressure detection mechanism can detect the air pressure of the soil gap in the sand layer.

2. The soil gas-induced liquefaction test device according to claim 1, characterized in that: The sample tube includes a tube body and a base. The tube body is fixedly installed on the top surface of the base. An air distribution cavity is opened inside the base. The top of the air distribution cavity is provided with a plurality of air distribution holes connected with the interior of the tube body. An air inlet interface connected with the air distribution cavity is fixedly installed on one side of the base. The air inlet end of the air inlet interface is connected with the air pressure regulating valve.

3. The soil gas-induced liquefaction test device according to claim 2, characterized in that: The air distribution structure includes a gravel layer, the gravel layer is filled at the bottom end of the cylinder, and the top surface of the gravel layer is paved with a waterproof and breathable membrane.

4. The soil gas-induced liquefaction test device according to claim 2, characterized in that: The side surface of the cylinder is connected to and installed with a plurality of air pressure detection interfaces evenly distributed from bottom to top, the inner ends of the air pressure detection interfaces are installed with filter membranes, and the outer ends of the air pressure detection interfaces are all connected to the air pressure detection mechanism.

5. The soil gas-induced liquefaction test device according to claim 1, characterized in that: The air supply assembly includes an air compressor, an air supply interface is provided on the air compressor, an air supply valve is installed on the air supply interface, and an air distribution duct is connected to one end of the air supply interface.

6. The soil gas-induced liquefaction test device according to claim 5, characterized in that: The air pressure regulating valve includes a valve body, one end of which is connected to the gas distribution conduit, and the other end of which is connected to the gas delivery conduit, one end of which is connected to the gas distribution structure inside the sample cylinder; An air guide tube for isolating the air inlet and outlet ends is provided inside the valve body, an air guide hole is provided on the air guide tube, a valve core is sealed in the air guide hole, a valve stem is fixedly mounted on the valve core, and a constant pressure regulating unit connected to the valve stem is provided on the top of the valve body. The constant pressure regulating unit can drive the valve stem and the valve core to move up and down according to the air pressure at the air outlet end of the valve body to adjust the opening size of the air guide hole.

7. The soil gas-induced liquefaction test device according to claim 6, characterized in that: The constant pressure regulating unit includes an air pressure regulating chamber, wherein a flexible diaphragm is fixedly installed inside the air pressure regulating chamber, and the flexible diaphragm divides the air pressure regulating chamber into an upper chamber and a lower chamber, and the lower chamber is connected to the air outlet end of the valve body through an air pressure balance conduit; A center plate is fixedly mounted on the flexible diaphragm, the bottom end of the center plate is fixedly connected to the top end of the valve stem, and the top end of the center plate is abutted against a pressure spring located in the upper chamber.

8. The soil gas-induced liquefaction test device according to claim 7, characterized in that: A limiting sleeve is fixedly installed at the top of the air pressure regulating chamber, and an air pressure regulating plate is slidably installed inside the limiting sleeve. The air pressure regulating plate abuts against the top of the pressure spring, and an adjusting drive member capable of driving the air pressure regulating plate to be raised or lowered is also installed on the limiting sleeve; The adjusting drive member includes a threaded sleeve, which is fixedly mounted on the top of the limiting sleeve. The internal thread of the threaded sleeve is driven by a gas pressure regulating rod, the top of which is fixedly mounted with a gas pressure regulating handle, and the lower end of the gas pressure regulating rod is fixedly connected to the gas pressure regulating plate; A limit shaft is fixedly mounted on the top end of the center plate, and the bottom end of the air pressure regulating rod is slidably plugged into the top end of the limit shaft.

9. The soil gas-induced liquefaction test device according to claim 1, characterized in that: The air pressure detection mechanism includes a support, which is fixedly installed on the top surface of the test bench. A plurality of air pressure detectors are fixedly installed on the support. An air pressure detection tube is connected to the detection port of each air pressure detector, and one end of the air pressure detection tube is connected to the sample tube.

10. A soil gas liquefaction test method, using the soil gas liquefaction test device according to any one of claims 1 to 9, characterized in that: The specific steps are as follows: Fill the sample tube with sample soil to form a sand layer, then add water to the sample tube and make the water level submerge above the sand layer; Then, the air supply assembly is turned on to supply air to the air distribution structure at the bottom of the sample tube through the air pressure regulating valve, so that the air seeps upward through the soil gaps in the sand layer to impact the soil. At the same time, the air pressure in the soil gaps in the sample tube is tested by the air pressure detection mechanism. Observe the state of the sand layer under gas seepage impact to determine the degree of soil liquefaction.

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