Collapse test device for high-saturation gas-sand-containing three-dimensional soil column

Abstract

The utility model discloses a collapse test device for a high-saturation gas-sand-containing three-dimensional soil column. The device comprises a model box, a lifting mechanism, a vacuum pump and a CO2 gas tank, the model box comprises a bottom plate, a box body and a top cover which are sequentially arranged from bottom to top; the box body is of a hollow cylinder structure, the bottom plate is fixedly connected with the box body, the box body is detachably connected with the top cover, and the lifting mechanism is arranged in the box body; a first valve and a second valve are arranged above the top cover, and the second valve is connected with the vacuum pump or the CO2 gas tank. Soil column collapse can be triggered under the totally-closed condition through the lifting mechanism, the vacuum pump, the CO2 gas tank and the model box are used in cooperation, and preparation of a saturated soil column and a high-saturation-degree gas-bearing sand soil column can be achieved respectively. According to the test device, the pressure and the soil saturation can be controlled, and the reliability of a test result is ensured.

Description

Technical Field

[0001] The utility model belongs to the technical field of indoor model box test equipment, and relates to a soil column collapse test device, in particular to a high-saturation gas-containing sand three-dimensional soil column collapse test device. Background Art

[0002] Underwater landslides are common marine geological hazards in offshore deltas, continental shelves, deep sea basins, etc., which are mainly manifested in the large-scale transfer of large amounts of soil. Large-scale underwater landslides can transport more than 100km 3 The flow rate can exceed 19m / s, and can still maintain a flow rate of 3-10m / s on a slide of only 0.2° to 0.3°. These flowing materials are mainly composed of granular materials (such as sand, silt and gravel) and entrained media (such as gas, water and mud). Understanding the fluid dynamic response of granular materials and predicting the speed and range of possible material propagation are crucial for risk assessment and prevention.

[0003] The soil column collapse problem is the most intuitive and effective physical and mechanical test to study the hydrodynamic properties of granular materials. The typical soil column collapse test process includes a cylindrical or rectangular soil column sliding along the base under the drive of its own weight after the side retaining wall is removed. At present, the hydrodynamic properties of dry granular materials have been well understood. However, the collapse mechanism and law of underwater granular materials have not been well revealed due to the complex interaction between fluid and solid particles.

[0004] In addition, due to the high content of organic matter in the soft soil along the coast of my country, the decomposition forms methane which is stored in the overlying or underlying silt sand, shell sand, and silt soil layers, and is easy to form gas-bearing sand layers under the closure of the upper and lower clay layers. The gas in the gas-bearing sand layer often exists between the soil skeleton in the form of free gas. The special existence form of the gas changes the mechanical properties of marine (marine) sedimentary soil, thereby affecting the flow properties of the landslide.

[0005] However, the collapse process of underwater highly saturated gas-sand slopes is difficult to observe on site, and indoor model box tests are also limited by the preparation of gas-sand slopes / soil columns. Therefore, the flow properties of highly saturated gas-sand granular materials remain at the level of theoretical analysis and numerical simulation, and their theoretical results lack experimental support.

[0006] Therefore, it is necessary to propose a new type of underwater soil column collapse test equipment to realize the preparation of underwater highly saturated gas-containing soil columns and soil column collapse tests. Utility Model Content

[0007] The utility model aims to provide a high-saturation gas-containing sand three-dimensional soil column collapse test device to solve the problem in the above-mentioned background technology that the test cannot be carried out due to the lack of high-saturation gas-containing sand soil columns.

[0008] To achieve the above purpose, the utility model provides the following technical solutions:

[0009] A high-saturation gas-containing sand three-dimensional soil column collapse test device, comprising a model box, a lifting mechanism, a vacuum pump and a CO2 gas tank; the model box comprises a bottom plate, a box body and a top cover arranged in sequence from bottom to top; the box body is a hollow cylindrical structure, the bottom plate is fixedly connected to the box body, the box body and the top cover are detachably connected, and the lifting mechanism is arranged inside the box body; a first valve and a second valve are arranged above the top cover, and the second valve is connected to the vacuum pump or the CO2 gas tank.

[0010] Furthermore, the lifting mechanism includes a mold barrel, a rope, a first fixed pulley, a second fixed pulley, a first rotating shaft, a second rotating shaft, and a counterweight block. The first rotating shaft and the second rotating shaft are both fixed on the side wall of the box body. The first rotating shaft is provided with a first fixed pulley, and the second rotating shaft is provided with a second fixed pulley. The mold barrel is a soil column forming mold with upper and lower openings open, located above the bottom plate, and connected to one end of the rope. The rope is vertically introduced upward from the mold barrel into the first fixed pulley and then horizontally enters the second fixed pulley. After changing direction, it is vertically led out and connected to the counterweight block.

[0011] Furthermore, an electromagnet is provided on the side wall of the box body, and the electromagnet is opposite to the counterweight block and is used to fix the counterweight block.

[0012] Furthermore, a counterweight well is provided above the bottom plate, the counterweight well is located directly below the counterweight block, and the bottom of the counterweight well is filled with buffer cotton.

[0013] Furthermore, a TDR time domain reflectometer is also provided on the bottom plate, and the TDR time domain reflectometer is located directly below the mold cylinder.

[0014] Furthermore, the edges of the bottom plate and the top cover protrude from the box body, and the top cover is connected to the bottom plate by bolts.

[0015] Furthermore, a groove is provided on the top of the box body, and a sealing ring is provided in the groove.

[0016] Furthermore, a first pressure gauge is provided on the top cover.

[0017] Furthermore, a transparent window is provided on the side wall of the box.

[0018] A highly saturated gas-containing sand three-dimensional soil column collapse test method is implemented using the above device, comprising the following steps:

[0019] Place the mold cylinder on the bottom plate, weigh a specified weight of dry sand, and fill the mold cylinder in layers to a specified height;

[0020] Connect one end of the rope to the mold cylinder, and the other end to the counterweight, and place the counterweight on the side of the electromagnet after passing through the first fixed pulley and the second fixed pulley in sequence, and turn on the power of the electromagnet to make the counterweight adsorbed on the electromagnet;

[0021] Slowly inject distilled water into the model box to a predetermined water level, the water level should not exceed the height of the mold barrel;

[0022] Install the sealing ring and top cover on the box body in sequence and tighten the bolts;

[0023] Open the second valve, close the first valve, connect the vacuum pump and the second valve with a high-pressure pipe, turn on the vacuum pump, and close the vacuum pump and the second valve after vacuuming, and maintain the negative pressure for no less than 1 day;

[0024] Slowly open the first valve to return the air pressure in the model box to the standard atmospheric pressure value; connect the CO2 gas tank and the second valve through a high-pressure pipe, slowly open the CO2 gas tank, increase the pressure in the model box to the predetermined pressure p1, and maintain the pressure for no less than 2 days to make the CO2 solution reach saturation;

[0025] Slowly reduce the output pressure of the CO2 gas tank to a predetermined pressure p2, so that CO2 gas precipitates from the solution, and monitor the saturation of the soil column by TDR time domain reflectometer. When the predetermined saturation is reached, close the second valve;

[0026] Turn off the power supply of the electromagnet, so that the counterweight block falls into the counterweight well and drives the mold tube to rise vertically. The soil column begins to collapse after losing its side support.

[0027] Compared with the prior art, the beneficial effects of the utility model are:

[0028] 1. The test device of the utility model is provided with a vacuum pump, which can realize the preparation and testing of underwater saturated soil columns; at the same time, the device is also provided with a CO2 gas tank, which can complete the preparation of saturated CO2 pore fluid through the control of gas pressure, and reduce the pressure to make CO2 gas precipitate from the saturated CO2 solution, thereby realizing the preparation and testing of highly saturated gas-containing sandy soil columns.

[0029] 2. The test device of the utility model includes a lifting mechanism, which is connected to a counterweight block and an electromagnet, and can control the lifting of the mold cylinder by turning on and off the electromagnet circuit, thereby realizing the trigger control of the collapse of the soil column in a fully enclosed model box.

[0030] 3. The top cover of the model box of the test device of the utility model is also provided with a pressure gauge, which can be used to observe the pressure changes inside the model box; a transparent window is provided on the side of the model box, which can be used to observe and record the collapse process of the soil column; a TDR time domain reflectometer is provided at the center of the bottom of the soil column to monitor the saturation changes of the soil column; thereby ensuring the controllability of the test variables and improving the reliability of the test results. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] Figure 1 This is a front view structural diagram of the model box in the embodiment of the utility model;

[0032] Figure 2 This is a rear view structural diagram of the model box in the embodiment of the utility model;

[0033] Figure 3 This is a top view of the structure of the model box in the embodiment of the utility model;

[0034] Figure 4 This is a cross-sectional structural diagram of the model box AA in the embodiment of the utility model;

[0035] Figure 5 This is a cross-sectional structural diagram of the model box BB in the embodiment of the utility model;

[0036] Figure 6 This is a cross-sectional structural diagram of the model box CC in the embodiment of the utility model;

[0037] Figure 7 This is a partial structural diagram of the lifting mechanism in the embodiment of the utility model;

[0038] Figure 8 This is a schematic diagram of the installation of the top cover of the model box in the embodiment of the utility model;

[0039] Fig. 9 This is a schematic diagram of the soil column saturation process in the embodiment of the utility model;

[0040] Fig.10 This is a schematic diagram of the preparation process of a highly saturated gas-containing soil column in an embodiment of the utility model;

[0041] In the figure: 1, bottom plate; 101, threaded hole; 2, box body; 201, transparent window; 202, electromagnet; 203, groove; 3, top cover; 302, through hole; 303, first valve; 304, second valve; 4, bolt; 401, nut; 402, screw; 403, thread; 5, lifting mechanism; 501, mold cylinder; 502, rope; 503, first fixed pulley; 504, second fixed pulley; 505, first rotating shaft; 506, second rotating shaft; 507, counterweight; 6, counterweight well; 7, buffer cotton; 801, first pressure gauge; 802, second pressure gauge; 803, TDR time domain reflectometer; 9, sealing ring; 10, high-pressure pipe; 11, vacuum pump; 12, CO2 gas tank. DETAILED DESCRIPTION

[0042] The technical solution of the utility model will be clearly and completely described below in conjunction with the accompanying drawings and embodiments.

[0043] like Figure 1-10As shown, a high-saturation gas-containing sand three-dimensional soil column collapse test device includes a model box, a lifting mechanism 5, a vacuum pump 11 and a CO2 gas tank 12; the model box is a hollow cylindrical structure, including a bottom plate 1, a box body 2 and a top cover 3 arranged in sequence from bottom to top; the bottom plate 1 and the top cover 3 are circular steel plates of equal diameter, and their diameters are larger than the outer diameter of the side wall 2 of the model box; the bottom plate 1 is welded below the box body 2, the top cover 3 is detachably connected to the bottom plate 1 by bolts 4, and the lifting mechanism is arranged inside the box body 2; a first valve 303 and a second valve 304 are arranged above the top cover 3, the second valve 304 is connected to the vacuum pump 11 or the CO2 gas tank 12 through a high-pressure pipe 10, and the closing of the channel is controlled by turning the valve switch.

[0044] The bolt 4 is used to fix the top cover, and is composed of a nut 401, a screw rod 402 and a thread 403 from top to bottom. The length of the screw rod 402 is consistent with the height of the model box 2. The edge of the bottom plate 1 is provided with a threaded hole 101 that matches the thread 403, and the top cover 3 is provided with a through hole 302 that is equivalent to the diameter of the screw rod 402. The bolt 4 passes through the through hole 302 and is connected to the threaded hole 101.

[0045] The lifting mechanism 5 includes a mold barrel 501, a rope 502, a first fixed pulley 503, a second fixed pulley 504, a first rotating shaft 505, a second rotating shaft 506, and a counterweight 507. The first rotating shaft 505 and the second rotating shaft 506 are both fixed on the side wall of the box body 2. The first rotating shaft 505 is provided with a first fixed pulley 503, and the second rotating shaft 506 is provided with a second fixed pulley 504, which can rotate around the shaft. The mold barrel 501 is located above the bottom plate 1 and is connected to one end of the rope 502. The rope 502 is vertically introduced upward from the mold barrel 501 into the first fixed pulley 503 and then horizontally enters the second fixed pulley 504. After changing direction, it is vertically led out and connected to the counterweight 507. The mold barrel 501 is a cylindrical thin-walled barrel with upper and lower openings. The lifting mechanism 5 lifts the mold barrel 501 from the bottom plate 1 to the air through the counterweight 507, thereby triggering the collapse of the soil column.

[0046] The side wall of the box 2 is embedded with an electromagnet 202, which is opposite to the counterweight 507 and is used to fix the counterweight 507. The counterweight 507 needs to be made of iron so that it can be adsorbed by the electromagnet. The electromagnet 202 can generate magnetic force under power-on conditions to attract the counterweight 507, and can lose magnetic force under power-off conditions to cause the counterweight to fall.

[0047] A counterweight well 6 is welded above the base plate 1, and the counterweight well 6 is located directly below the counterweight block 507. The counterweight well 6 is a space with only an upper end open, which is used to receive the falling counterweight block 507; the bottom of the counterweight well 6 is filled with buffer cotton 7 to reduce the vibration caused by the falling of the counterweight block 507.

[0048] The bottom plate 1 is also provided with a TDR time domain reflectometer 803 , which is located directly below the mold cylinder 501 and is used to monitor the saturation of the soil column.

[0049] The top of the box body 2 is provided with a groove 203, and a sealing ring 9 matching its size is provided in the groove 203, and the depth of the groove 203 is less than the diameter of the sealing ring 9. The sealing ring 9 can ensure that the entire model box can be in a sealed state after tightening the bolts 4 on the top cover 3.

[0050] The top cover 3 is provided with a first pressure gauge 801 for measuring the pressure in the model box; a second pressure gauge 802 is provided between the CO2 gas tank 12 and the high-pressure pipe 10.

[0051] A transparent window 201 for observation and video recording is provided on the side wall of the box body 2. The transparent window 201 needs to meet the pressure resistance requirement and is preferably made of tempered glass.

[0052] A three-dimensional soil column collapse test method for highly saturated gas-containing sand implemented by the above device, taking sand as an example, comprises the following steps:

[0053] (1) Preparation of dry sand column: Place the mold cylinder 501 at the center of the bottom plate 1, weigh a specified weight of dry sand, and fill the mold cylinder 501 in layers to a specified height;

[0054] (2) Installing the rotating mechanism 5: Connect one end of the rope 502 to the mold cylinder 501, and the other end to the counterweight 507. After passing through the first fixed pulley 503 and the second fixed pulley 504 in sequence, place the counterweight 507 on the side of the electromagnet 202, turn on the power of the electromagnet 202, and make the counterweight 507 adsorbed on the electromagnet 202;

[0055] (3) Filling distilled water: Slowly inject distilled water into the model box to a predetermined water level, and the water level height does not exceed the height of the mold cylinder 501;

[0056] (4) Install the top cover: Install the sealing ring 9 and the top cover 3 on the box body 2 in sequence, and tighten the bolts 4 to ensure the sealing of the model box;

[0057] (5) Vacuum saturation: open the second valve 304, close the first valve 303, connect the vacuum pump 11 and the second valve 304 with the high-pressure pipe 10, turn on the vacuum pump 11, and the vacuuming time should not be less than 1 hour. After vacuuming, close the vacuum pump 11 and the second valve 304, and maintain the negative pressure time for not less than 1 day;

[0058] (6) Preparing a saturated CO2 solution: Slowly open the first valve 303 to return the air pressure in the model box to the standard atmospheric pressure value; connect the CO2 gas tank 12 and the second valve 304 through the high-pressure pipe 10, slowly open the CO2 gas tank 12, increase the pressure in the model box to a predetermined pressure p1, and maintain the pressure for at least 2 days to saturate the CO2 solution;

[0059] (7) Preparation of highly saturated gas-containing sand column: Slowly reduce the output pressure of the CO2 gas tank 12 to a predetermined pressure p2, so that CO2 gas is precipitated from the solution, and monitor the saturation of the soil column by the TDR time domain reflectometer 803. After reaching the predetermined saturation, close the second valve 304;

[0060] (8) Collapse of soil column: Turn off the power supply of electromagnet 202, so that the counterweight block 507 falls into the counterweight well 6, and drives the mold tube 501 to rise vertically. The soil column begins to collapse after losing the side support.

[0061] The embodiments described above are only some embodiments of the utility model, not all embodiments. Based on the embodiments of the utility model, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the utility model.

[0062] Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art may still modify the technical solutions described in the aforementioned embodiments, or make equivalent substitutions for some of the technical features therein. Any modifications, equivalent substitutions, improvements, etc. made within the ideas and principles of the present invention shall be included in the protection scope of the present invention.

Claims

1. A three-dimensional soil column collapse test device for highly saturated gas-containing sand, characterized in that: The invention comprises a model box, a lifting mechanism (5), a vacuum pump (11) and a CO2 gas cylinder (12); the model box comprises a bottom plate (1), a box body (2) and a top cover (3) which are arranged in sequence from bottom to top; the bottom plate (1) is fixedly connected to the box body (2), the box body (2) is detachably connected to the top cover (3), and the lifting mechanism is arranged inside the box body (2); a first valve (303) and a second valve (304) are arranged above the top cover (3), and the second valve (304) is connected to the vacuum pump (11) or the CO2 gas cylinder (12); the lifting mechanism (5) comprises a mold cylinder (501), a rope (502), a first fixed pulley (503), a second fixed pulley (504), a first rotating shaft (505), a second rotating shaft (506), a counterweight The mold cylinder (501) is located above the bottom plate (1) and is connected to one end of the rope (502). The rope (502) is introduced vertically upward from the mold cylinder (501) into the first fixed pulley (503) and then horizontally enters the second fixed pulley (504). After changing direction, the rope (502) is vertically led out and connected to the counterweight block (507). An electromagnet (202) is provided on the side wall of the box body (2). The electromagnet (202) is opposite to the counterweight block (507) and is used to fix the counterweight block (507).

2. The highly saturated gas-containing sand three-dimensional soil column collapse test device according to claim 1 is characterized in that: A counterweight well (6) is provided above the bottom plate (1), and the counterweight well (6) is located directly below the counterweight block (507). The bottom of the counterweight well (6) is filled with cushioning cotton (7).

3. The highly saturated gas-containing sand three-dimensional soil column collapse test device according to claim 1 is characterized in that: The bottom plate (1) is also provided with a TDR time domain reflectometer (803), and the TDR time domain reflectometer (803) is located directly below the mold cylinder (501).

4. The highly saturated gas-containing sand three-dimensional soil column collapse test device according to claim 1 is characterized in that: The edges of the bottom plate (1) and the top cover (3) protrude from the box body (2), and the top cover (3) is connected to the bottom plate (1) via bolts (4).

5. The highly saturated gas-containing sand three-dimensional soil column collapse test device according to claim 1 is characterized in that: The top of the box body (2) is provided with a groove (203), and a sealing ring (9) is provided in the groove (203).

6. The highly saturated gas-containing sand three-dimensional soil column collapse test device according to claim 1 is characterized in that: The top cover (3) is provided with a first pressure gauge (801).

7. The highly saturated gas-containing sand three-dimensional soil column collapse test device according to claim 1 is characterized in that: A transparent window (201) is provided on the side wall of the box body (2).

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