CN109991114A - Device and method for testing water-holding parameters of soil containing tetrahydrofuran hydrate - Google Patents

Abstract

The invention discloses a water-holding parameter testing device and a method for soil containing tetrahydrofuran hydrate, and relates to a testing technology for water-holding parameters of soil containing hydrate. The device includes a test part and a water bath constant temperature part; the test part includes a high-pressure nitrogen cylinder (1), a pressure reducing valve (2), a pressure regulating pump (3), a pressure (4), a water storage bottle (5), and a gas collecting pipe (6) , collecting cup (7), balance (8), data acquisition system (9) and valves 1 to 3 (V1 to V3); the constant temperature part of the water bath includes a constant temperature water bath box (10), a circulating pump (11), a temperature sensor (12), the refrigeration system (13) and the 4th to 7th valves (V4 to V7). The invention can simply and quickly prepare a uniform and stable hydrate-containing soil sample; the SWCC curve can be obtained simply, quickly and accurately; the suction range is wide, and the manual error of the traditional shaft translation method can be reduced.

Description

Device and method for testing water-holding parameters of soil containing tetrahydrofuran hydrate

technical field

The invention relates to a testing technology for water-holding parameters of hydrate-containing soil, in particular to a water-holding parameter testing device and method for tetrahydrofuran (THF) hydrate-containing soil.

Specifically, it involves the measurement of the soil-water characteristic relationship curve (SWCC) of soil containing tetrahydrofuran hydrate under different hydrate content conditions, the sample is controlled to form tetrahydrofuran hydrate under low temperature conditions and the test is carried out, and the axis translation technique is used to carry out the suction measurement. Control and measurement, collect and record the water output of the sample according to the automatic data acquisition system, judge the suction balance and calculate the water content of the sample under the suction, and obtain the soil-water characteristics of the soil containing tetrahydrofuran hydrate under different hydrate content conditions The relationship curve provides important data support for hydrate mining.

Background technique

Natural gas hydrate is a new type of clean energy. However, improper exploitation will lead to engineering problems such as submarine landslides and ground subsidence, and it will also release greenhouse gases and cause global warming. The water-holding characteristic parameters of hydrate-bearing sediments are very important basic parameters in the process of natural gas hydrate drilling and exploitation. The mechanical properties, gas-water migration process and occurrence state of sediments are all related to their water-holding properties. The Soil-Water Characteristic Curve (SWCC) is the relationship between soil moisture content and suction, which reflects the water-holding capacity of the soil and is a key function to describe the behavior of unsaturated soils. The SWCC curve is essentially determined by pore-scale characteristics, including pore shape and size distribution, interconnectivity and spatial variability, fluid and interfacial tension, etc. The hydrates present in the sediments will change the soil mass to a large extent. pore-scale features.

It is very difficult to carry out the research on the SWCC curve of hydrate-containing sediments. To avoid the decomposition of hydrates, high fluid pressure and low temperature are required. At the same time, the synthesis of methane hydrate in the laboratory requires a long induction time, and the solubility of methane in water is low. , the seepage loss is large, it is difficult to maintain the stability of the sample during the test, and the cost of synthesis and test equipment is expensive, making the relevant data extremely scarce. Studies have shown that tetrahydrofuran (THF) hydrate has similar thermophysical properties to methane hydrate, which can overcome the above difficulties and replace methane hydrate for experimental research. The synthesis only needs to control low temperature conditions, and the saturation of THF hydrate is easy to control. Therefore, we used THF hydrate as the test object and developed an indoor test device for testing the SWCC curve of THF hydrate sediments. The device can overcome the shortcomings of the commonly used pressure plate method in the soil-water characteristic relationship curve test, such as time-consuming, small suction range, error caused by the need for regular manual reading of test data, and no temperature control system. It can be used for THF hydrate sediment SWCC. The curve test can also be used for the test of conventional samples.

At present, after searching, the device and method for researching and testing the water-holding parameters of hydrate-containing soil have not been reported yet.

Invention content:

The purpose of the present invention is to fill the gaps in obtaining the water-holding parameters of hydrate-containing sediments at home and abroad, overcome the deficiencies in the above-mentioned prior art, and provide a tetrahydrofuran hydrate-containing soil water-holding parameter testing device and method thereof , the design is reasonable, simple and easy to use, which can make the determination result of the soil-water characteristic relationship curve of THF hydrate accurate, the test time is short, and the determination method is convenient.

The technical scheme adopted by the present invention for solving the above problems is:

This device uses nitrogen to apply air pressure to the sample in the pressure chamber under low temperature conditions, uses the axis translation method to control and measure the suction of the sample containing THF hydrate, and judges the suction according to the collection of the water output of the sample by the automatic data collection system. Balance and calculate the water content of the sample under this suction, and obtain the soil-water characteristic curve (SWCC) of the soil containing tetrahydrofuran hydrate, which greatly shortens the test time and realizes the research on the water-holding parameters of the hydrate-containing sedimentary soil. The principle is in line with the hydrate formation mode and mining conditions, the structure is simple, and the cost is low, and it can be equipped for most scientific research and design units.

In this method, the sample is placed in a certain concentration of tetrahydrofuran aqueous solution for saturation, and then the sample is placed in a constant temperature water bath to cool down and induce, so as to obtain tetrahydrofuran hydrate-containing soil with uniform hydrate distribution; the THF hydrate-containing sample is packed It is placed on the clay plate in the pressure chamber of the constant temperature water bath, and various air pressures are applied to the pressure chamber. The axis translation method is used to control and measure the suction of the sample containing THF hydrate. The data acquisition system automatically records the output of the sample in the pressure chamber. According to the water quantity data, the balance and water content of the sample can be quickly judged according to the water output state, and the soil-water characteristic relationship curve (SWCC) under different hydrate saturation conditions can be obtained. The method is simple, accurate and easy to operate.

Specifically:

1. Testing device for water holding parameters of soil containing tetrahydrofuran hydrate

The device includes a test part and a water bath constant temperature part;

The test part includes high pressure nitrogen cylinder, pressure reducing valve, pressure regulating pump, pressure chamber, water storage bottle, gas collecting pipe, liquid collecting cup, balance, data acquisition system and 1st to 3rd valves;

The constant temperature part of the water bath includes a constant temperature water bath, a temperature sensor, a circulating pump, a refrigeration system and the 4th to 7th valves;

Its location and connection relationship are:

A pressure chamber is arranged in a constant temperature water bath, and a sample and a clay plate connected up and down are arranged in the pressure chamber to provide a test place for the sample;

The high-pressure nitrogen cylinder, the pressure reducing valve and the pressure regulating pump are connected to the air inlet of the upper cover of the pressure chamber through the pipeline in turn, so as to provide the air pressure environment for the sample;

The water storage bottle, the first valve and the water inlet of the pressure chamber are connected in sequence to provide a water pressure environment for the sample;

The water outlet of the pressure chamber, the second valve, the gas collecting pipe, the third valve and the liquid collecting cup are connected in sequence, the liquid collecting cup is placed on the balance, the balance is connected with the data acquisition system, and the change of the water effluent of the sample is measured;

The probes of the temperature sensor are arranged at the top, middle and bottom of the constant temperature water bath, and the temperature sensor is connected to the data acquisition system to measure the temperature of the surrounding environment of the sample;

A heat-conducting copper pipe is arranged in the constant temperature water bath, and a cooling liquid inlet, a water circulation inlet, a cooling liquid outlet and a water circulation outlet are respectively arranged on the left and right side walls of the constant temperature water bath;

The water circulation inlet, the 5th valve V5 circulation pump, the 6th valve and the water circulation outlet are connected in a closed-loop sequence to provide a constant temperature environment for the sample;

The outlet of the refrigeration system, the fourth valve, the refrigerant liquid inlet, the heat-conducting copper pipe, the refrigerant liquid outlet, the seventh valve and the inlet of the refrigeration system are connected in a closed-loop sequence to provide a refrigeration environment for the sample.

working principle:

The device uses a water bath constant temperature system to control the temperature. In the water bath constant temperature system, the temperature of the sample saturated with a certain concentration of tetrahydrofuran solution is induced to cool down, and the samples containing THF hydrate with different hydrate contents and uniform distribution are quickly prepared. After the sample is placed on the clay plate in the pressure chamber, the pressure chamber is assembled and placed in a constant temperature water bath box, and a high-pressure nitrogen bottle is used to apply various pressures to the pressure chamber. The pressure reducing valve can change the high-pressure gas in the nitrogen bottle to a low pressure. The gas is transported to the pressure chamber. The pressure regulating pump can pressurize or release the pressure to adjust the air pressure in the pressure chamber. The water storage bottle is used to saturate the entire system and fill the entire test pipeline with water. In the commissioning stage, the gas in the pipeline is collected to ensure that the liquid collected in the collecting cup is indeed discharged from the sample. The collecting cup is used to collect the moisture discharged from the sample. The quality of the moisture is automatically read and recorded by the balance connected to the data acquisition system. , according to the state of water output, the balance and water content of the sample can be quickly judged, and the soil-water characteristic relationship curve (SWCC) under different hydrate saturation conditions can be obtained.

The present invention has the following advantages and positive effects:

1. The uniform and stable hydrate-containing soil samples can be easily and quickly prepared;

2. The SWCC curve can be obtained easily, quickly and accurately;

3. The suction range is wide, which can reduce the manual error of the traditional shaft translation method.

Description of drawings

Fig. 1 is the structural representation of this device;

Fig. 2 is the structural representation of pressure chamber;

Figure 3 is a schematic structural diagram of a constant temperature water bath.

in:

1—High pressure nitrogen cylinder;

2—reducing valve;

3—pressure regulating pump;

4—Pressure chamber,

4-1—air inlet, 4-2—the first sealing rubber ring, 4-3—fixed screw,

4-4—Plexiglas, 4-5—Sample, 4-6—Clay plate,

4-7—the second sealing ring, 4-8—water outlet, 4-9—water inlet,

4-10—pressure chamber base, 4-11—pressure chamber cover, 4-12—drainage groove;

5—water storage bottle;

6—Gas collection pipe;

7—collection cup;

8—balance;

9—Data acquisition system;

10—The constant temperature water bath,

10-1—The upper cover of the water bath, 10-2—the handle of the upper cover, 10-3—the body of the water bath,

10-4—heat-conducting copper pipe, 10-5—refrigerant liquid inlet, 10-6—water circulation inlet,

10-7—refrigerant liquid outlet, 10-8—water circulation outlet;

11—temperature sensor;

12—circulating pump;

13—refrigeration system;

V1, V2, ~V7—The 1st, 2nd to 7th valves.

Detailed ways

1. Device

1. Overall

As shown in Figures 1, 2 and 3, the device includes a test part and a water bath constant temperature part;

The test part includes high pressure nitrogen bottle 1, pressure reducing valve 2, pressure regulating pump 3, pressure chamber 4, water storage bottle 5, gas collecting pipe 6, liquid collecting cup 7, balance 8, data acquisition system 9 and 1st to 3rd valves V1~ v3;

The constant temperature part of the water bath includes a constant temperature water bath box 10, a temperature sensor 11, a circulating pump 12, a refrigeration system 13 and the fourth to seventh valves V4 to V7;

1) Test part

The high-pressure nitrogen cylinder 1, the pressure reducing valve 2 and the pressure regulating pump 3 are sequentially connected to the air inlet 4-1 of the upper cover 4-11 of the pressure chamber through pipelines. The glass cover 4-4 is used as the outer wall of the pressure chamber 4. The pressure chamber upper cover 4-11 and the organic glass cover 4-4 are connected to the pressure chamber base 4-10 through three fixing screws 4-3. The organic glass cover 4-4 The upper edge and the pressure chamber upper cover 4-11 are sealed by the first sealing rubber ring 4-2, and the pressure chamber base 4-10 is sealed by the second sealing rubber ring 4-7, and the second sealing rubber ring 4-7 is also sealed The clay plate 4-6 is fixed, the sample 4-5 is placed on the clay plate 4-6, and a drainage groove 4-12, a water outlet 4-8 and a water inlet 4-9 are arranged under the clay plate 4-6. The water outlet 4-9 is connected to the water storage bottle 5 through the pipeline and the first valve V1, the water outlet 4-8 is connected to the gas collecting pipe 6 through the pipeline and the second valve V2, and the gas collecting pipe 6 is connected to the gas collecting pipe 6 through the pipeline and the third valve V3. In the liquid collection cup 7, the liquid collection cup 7 is placed on the balance 8, and the balance 8 is connected to the data acquisition system 9. The data acquisition system 9 records the water output of the sample by automatically reading the reading of the balance 8, and automatically draws the relationship between the water output and time curve.

2) Water bath constant temperature part

The formation of THF hydrate requires a low temperature environment, so the pressure chamber 4 in which the THF hydrate-containing samples 4-5 are placed in the test part is placed in a constant temperature water bath box 10 for testing, and the refrigerant is ethylene glycol and distilled water in a 1:2 configuration The constant temperature water bath box 10 is composed of a box body 10-3 and an upper cover 10-1. The upper cover 10-1 is formed by combining two small rectangular covers with connecting openings, which is convenient for the pipes of the pressure chamber 4 The box body 10-3 is provided with a heat-conducting copper pipe 10-4 to circulate the refrigerant liquid, and the refrigerant liquid is cooled by the refrigeration system 13. The refrigerant liquid passes through the pipeline and the fourth valve V4 from the refrigeration system 13. 10-5 enters the heat-conducting copper pipe 10-4, and returns to the refrigeration system 13 from the refrigerant liquid outlet 10-7 via the pipeline and the seventh valve V7; The circulating pump 12 is set for water circulation, and the water in the box enters the water circulation inlet 10-6 from the water circulation outlet 10-8 via the pipeline, the sixth valve V6, the circulating pump 12 and the fifth valve V5; in order to detect whether the temperature of the water bath box 10 reaches the target temperature And the temperature is uniform, the three temperature probes in the temperature sensor 11 are respectively arranged on the top, middle and bottom of the water bath 10 , and the data are automatically recorded on the data acquisition system 9 .

Its location and connection relationship are:

A pressure chamber 4 is arranged in the constant temperature water bath box 10, and a sample 4-5 and a clay plate 4-6 connected up and down are arranged in the pressure chamber 4, so as to provide a test place for the sample 4-5;

The high-pressure nitrogen cylinder 1, the pressure reducing valve 2 and the pressure regulating pump 3 are sequentially connected to the air inlet 4-1 of the upper cover 4-11 of the pressure chamber through the pipeline, so as to provide the air pressure environment for the sample 4-5;

The water storage bottle 5, the first valve V1 and the water inlets 4-9 of the pressure chamber 4 are connected in sequence to provide a water pressure environment for the samples 4-5;

The water outlet 4-8 of the pressure chamber 4, the second valve V2, the gas collecting pipe 6, the third valve V3 and the liquid collecting cup 7 are connected in turn, the liquid collecting cup 7 is placed on the balance 8, and the balance 8 is connected with the data acquisition system 9, Measure the change of the effluent of samples 4-5;

The probes of the temperature sensor 11 are respectively arranged at the top, middle and bottom of the constant temperature water bath 10, and the temperature sensor 11 is connected to the data acquisition system 9 to measure the temperature of the surrounding environment of the samples 4-5;

A heat-conducting copper tube 10-4 is arranged in the constant temperature water bath box 10, and a cooling liquid inlet 10-5, a water circulation inlet 10-6, a cooling liquid outlet 10-7 and a water circulation outlet 10 are respectively arranged on the left and right side walls of the constant temperature water bath box 10. -8;

The water circulation inlet 10-6, the fifth valve V5, the circulation pump 12, the sixth valve V6 and the water circulation outlet 10-8 are connected in a closed-loop sequence, providing a constant temperature environment for the sample 4-5;

The outlet of the refrigeration system 13, the fourth valve V4, the refrigerant liquid inlet 10-5, the heat-conducting copper pipe 10-4, the refrigerant liquid outlet 10-7, the seventh valve V4 and the inlet of the refrigeration system 13 are closed-loop connected in sequence, and the sample 4 -5 provides a refrigerated environment.

2. Functional components

1) High pressure nitrogen cylinder 1

It is an ordinary nitrogen gas storage cylinder, provided by Guangdong South China Special Gas Research Institute Co., Ltd.

2) Pressure reducing valve 2

Select the product of Shanghai Weiyue Industrial Co., Ltd., model: YQY-12, input pressure 15Mpa, adjustment range 0.1-1.25MPa.

3) Pressure regulating pump 3

Select Fairchild Industrial Products Company, model: M30BP, adjustment range: 0-15kPa, 15-700kPa, maximum pressure: 1000kpa, accuracy: 0.15psi.

4) Pressure chamber 4

As shown in Figure 2, the pressure chamber 4 includes an air inlet 4-1, a first sealing rubber ring 4-2, a fixing screw 4-3, a plexiglass cover 4-4, a sample 4-5, a clay plate 4-6, a first 2. Sealing rubber ring 4-7, water outlet 4-8, water inlet 4-9, pressure chamber base 4-10, upper cover No. 4-11 drainage groove 4-12;

Its location and connection relationship are:

From bottom to top, the base 4-10, the plexiglass cover 4-4 and the upper cover 4-11 are connected by three evenly distributed fixing screws 4-3 to form a sealed container, and the interface is connected by an O-shaped first sealing rubber ring 4 -2 and the second sealing rubber ring 4-7 are sealed;

An air inlet 4-1 is provided on the upper cover 4-11;

Clay plate 4-6 diameter The second sealing rubber ring 4-7 is embedded in the top of the base 4-10, a sample 4-5 is arranged above the clay plate 4-6, and a drainage groove 4-12, Water outlet 4-8 and water inlet 4-9.

5) Water bottle 5

It is an ordinary water storage bottle with a capacity of 2L.

6) Gas collector 6

It is an ordinary gas collecting tube with scale, with a capacity of 15ml and an accuracy of 0.5ml.

7) Collection cup 7

It is an ordinary beaker with a capacity of 200ml, which is sealed, and a small hole is reserved at the mouth of the cup to connect the pipeline.

8) Balance 8

Ohaus brand electronic scale, model: Scout pro SP202, weighing: 200g, accuracy: 0.01g.

9) Data acquisition system 9

Select Agilent data acquisition instrument and data acquisition software, model: 34972A, connect the balance 8 and the temperature sensor 11 through the channel provided by the acquisition instrument to collect data, record and process.

10) Constant temperature water bath 10

As shown in FIG. 3, the constant temperature water bath box 10 includes a water bath box upper cover 10-1, an upper cover handle 10-2, a water bath box body 10-3, a heat-conducting copper tube 10-4, a refrigerant liquid inlet 10-5, and a water circulation inlet 10-6 , refrigerant liquid outlet 10-7, water circulation outlet 10-8;

Its location and connection relationship are:

The upper cover 10-1 of the water bath box and the water bath box body 10-3 are connected up and down to form a whole;

An upper cover handle 10-2 is arranged on the upper cover 10-1 of the water bath;

The upper and lower parts of the water bath box 10-3 are respectively provided with heat-conducting copper pipes 10-4;

A refrigerant liquid inlet 10-5 and a water circulation inlet 10-6 are respectively provided on the upper part of the inner wall of the water bath box 10-3;

A refrigerant liquid outlet 10-7 and a water circulation outlet 10-8 are respectively provided at the lower part of the inner wall of the water bath box 10-3.

(1) Top cover of water bath box 10-1

It is formed by combining two small rectangular lids with connecting openings, the size is 40cm×40cm, the thickness is 3cm, and the interior is filled with thermal insulation material; the diameter of the opening is d=4cm.

(2) Upper cover handle 10-2

Ordinary pieces.

(3) Water bath box 10-3

A square container with a size of 40cm×40cm×50cm and a thickness of 3cm, filled with thermal insulation materials.

Set four drill holes: refrigerant liquid inlet 10-5, water circulation inlet 10-6, refrigerant liquid outlet 10-7, water circulation outlet 10-8, diameter d=1cm, and the wall of the drill hole is sealed.

(4) Thermal copper tube 10-4

Ordinary parts, 1/2 pipe, outer diameter 12.7mm, close to the inside of the box 10-3 spiral coil stack.

11) Circulating pump 11

The product of Jiangsu Shenglan Instrument Manufacturing Co., Ltd. is selected, model: BT-200B, dual-channel output, output flow: 2×(1～6800)ml/h, output pressure: ≥2.5kg/cm2.

12) Temperature sensor 12

A total of 3 products are selected from Beijing Saiyiling Technology Co., Ltd., product name: pt100, model: 1632-100, working temperature: -40~450℃, error: ±(0.15+0.002∣t∣).

13) Refrigeration system 13

The low temperature constant temperature bath product of Ningbo Tianheng Instrument Factory is selected, model: THD-2030, temperature range:

-20℃～100℃, control accuracy: 0.01℃, built-in circulating pump, pump flow rate 13L/min.

14) 1st to 7th valves V1 to V7

It adopts ordinary high-pressure valve, the diameter of both ends is Φ6mm, it is made of stainless steel, and the pressure resistance is 50MPa.

2. Test method for water-holding parameters of soil containing tetrahydrofuran hydrate (referred to as method)

The method includes the following steps:

① Sample preparation

According to the target hydrate saturation, tetrahydrofuran aqueous solutions of different concentrations were prepared, and samples 4-5 were evacuated and saturated for 24 hours. The 4th to 7th valves V4 to V7, the refrigeration system 13 and the circulating pump 12 were opened, and the saturated test samples were saturated for 24 hours. Samples 4-5 were put into a sealed bag and placed in a water bath box 10 and cooled to -8°C for induction. After 3 days, the water bath box 10 was heated to 1°C for 14 days, so that THF was completely converted into THF hydrate;

The preparation method of tetrahydrofuran aqueous solution is:

m _H2O —the mass of water in the tetrahydrofuran aqueous solution;

m _THF - the mass of tetrahydrofuran in the tetrahydrofuran aqueous solution;

S _H - hydrate saturation;

②Sampling

Considering the extra heat loss of the pressure chamber 4 during the heat transfer process, the temperature of the water bath should have a certain degree of subcooling, and the temperature of the constant temperature water bath box 10 should be lowered to -1°C; The clay plate 4-6 is sealed on the pressure chamber base 4-10, the first valve V1 is opened, and the water in the water storage bottle 5 saturates the drainage groove 4-12 and the pipeline through the water inlet 4-9; The liquid collected in the liquid cup 7 is indeed discharged from the sample 4-5, open the second valve V2 and the third valve V3, make the water pass through the pipeline and fill the gas collecting pipe 6, discharge the gas in the gas collecting pipe 6, close the first valve V1 At the same time, the collection cup 7 should be sealed to prevent moisture loss; then the prefabricated saturated THF-containing hydrate samples 4-5 were weighed, and then placed on the clay plate 4-6, the first sealing rubber ring 4-2 Put into the notch 4-11 of the pressure chamber cover, seal the pressure chamber 4 and install the fixing screw 4-3; put the pressure chamber 4 into the constant temperature water bath box 10 as a whole, connect all the pipelines and close the water bath Box cover 4-11;

③Leak detection and pressurization

Peel the balance 8 with the liquid collecting cup 7, open the data acquisition system 9, open the gas valve of the high-pressure nitrogen cylinder 1, control the pressure reducing valve 2 and the pressure regulating pump 3 to pass the specified air pressure into the pressure chamber 4, and in the data The acquisition system 9 fills in the value of the applied air pressure, and sets the data acquisition time interval; if the pressure display does not change after the first-stage pressure is applied for 2 hours, it can be considered that the pressure chamber is well sealed, and the test can be continued;

④Test

After applying pressure, the water discharged from the samples 4-5 enters the liquid collecting cup 7 through the pipeline, and the data acquisition system 9 reads the reading of the balance 8 in real time to judge whether the suction force of the matrix reaches a balance; after the reading of the balance 8 is stable, the next primary pressure;

⑤Calculation

According to the mass and water output of the saturated THF hydrate-containing samples 4-5 measured before the test, the water content after the suction balance of each level is converted, and then the soil moisture content of the THF hydrate sediment is established according to the suction value and water content of each level. Water Characteristic Relationship Curve (SWCC).

Claims (4)

1. a tetrahydrofuran hydrate-containing soil water-holding parameter testing device is characterized in that: Including the test part and the water bath constant temperature part; The test part includes a high-pressure nitrogen cylinder (1), a pressure reducing valve (2), a pressure regulating pump (3), a pressure chamber (4), a water storage bottle (5), a gas collecting pipe (6), a liquid collecting cup (7), and a balance. (8), the data acquisition system (9) and the first to third valves (V1 to V3); The constant temperature part of the water bath includes a constant temperature water bath box (10), a temperature sensor (11), a circulating pump (12), a refrigeration system (13) and the fourth to seventh valves (V4 to V7); Its location and connection relationship are: A pressure chamber (4) is arranged in a constant temperature water bath (10), a sample (4-5) and a clay plate (4-6) connected up and down are arranged in the pressure chamber (4), and a sample (4-6) is arranged in the pressure chamber (4). 5) A place to provide testing; The high-pressure nitrogen cylinder (1), the pressure reducing valve (2) and the pressure regulating pump (3) are sequentially connected to the air inlet (4-1) of the upper cover (4-11) of the pressure chamber through the pipeline, and the sample 4- 5 Provide air pressure environment; The water storage bottle (5), the first valve (V1) and the water inlet (4-9) of the pressure chamber (4) are connected in sequence to provide a water pressure environment for the sample (4-5); The water outlet (4-8), the second valve (V2), the gas collecting pipe (6), the third valve (V3) and the liquid collecting cup (7) of the pressure chamber (4) are connected in sequence, and the liquid collecting cup (7) is placed On the balance (8), the balance (8) is connected with the data acquisition system (9), and the change of the water effluent of the sample (4-5) is measured; The probes of the temperature sensor (11) are respectively arranged at the top, middle and bottom of the constant temperature water bath (10), the temperature sensor (11) is connected to the data acquisition system (9), and the temperature of the surrounding environment of the sample (4-5) is measured ; A heat-conducting copper tube (10-4) is arranged in the constant temperature water bath (10), and a cooling liquid inlet (10-5), a water circulation inlet (10-6), a cooling liquid inlet (10-5), a water circulation inlet (10-6), Refrigerant liquid outlet (10-7) and water circulation outlet (10-8); The water circulation inlet (10-6), the fifth valve (V5), the circulating pump (12), the sixth valve (V6) and the water circulation outlet (10-8) are connected in a closed-loop sequence to provide a constant temperature environment for the sample (4-5). ; The outlet of the refrigeration system (13), the fourth valve (V4), the refrigerant liquid inlet (10-5), the heat conducting copper pipe (10-4), the refrigerant liquid outlet (10-7), the seventh valve (V4) and the cooling The inlets of the system (13) are successively connected in a closed-loop manner to provide a refrigerating environment for the samples (4-5). 2. by the described tetrahydrofuran hydrate-containing soil water-holding parameter testing device of claim 1, it is characterized in that: The pressure chamber (4) comprises an air inlet (4-1), a first sealing rubber ring (4-2), a fixing screw (4-3), a plexiglass cover (4-4), a sample (4) -5), clay plate (4-6), second sealing ring (4-7), water outlet (4-8), water inlet (4-9), pressure chamber base (4-10), upper cover (4-11), drainage groove (4-12); Its location and connection relationship are: From bottom to top, the base (4-10), the plexiglass cover (4-4) and the upper cover (4-11) are connected to form a sealed container through three evenly distributed fixing screws (4-3). The first sealing rubber ring (4-2) and the second sealing rubber ring (4-7) of the O type are sealed; An air inlet (4-1) is arranged on the upper cover (4-11); Clay plate (4-6) diameter The second sealing rubber ring (4-7) is embedded on the top of the base (4-10), a sample (4-5) is arranged above the clay plate (4-6), and a sample (4-5) is arranged on the top of the clay plate (4-6). A drainage groove (4-12), a water outlet (4-8) and a water inlet (4-9) are arranged below. 3. according to claim 1, it is characterized in that: The constant temperature water bath box (10) comprises a water bath box upper cover (10-1), an upper cover handle (10-2), a water bath box body (10-3), a heat-conducting copper pipe (10-4), and a refrigerant liquid inlet (10-5), a water circulation inlet (10-6), a refrigerant liquid outlet (10-7) and a water circulation outlet (10-8); Its location and connection relationship are: The upper cover (10-1) of the water bath box and the water bath box body (10-3) are connected up and down to form a whole; An upper cover handle (10-2) is arranged on the upper cover (10-1) of the water bath; The upper and lower parts of the water bath box (10-3) are respectively provided with heat-conducting copper pipes (10-4); A refrigerant liquid inlet (10-5) and a water circulation inlet (10-6) are respectively provided on the upper part of the inner wall of the water bath box (10-3); A refrigerant liquid outlet (10-7) and a water circulation outlet (10-8) are respectively provided at the lower part of the inner wall of the water bath box (10-3); The upper cover (10-1) of the water bath box is formed by combining two small rectangular covers with connecting openings, the size is 40cm×40cm, the thickness is 3cm, and the interior is filled with thermal insulation material; the diameter of the opening is d=4cm; The water bath box (10-3) is a square container, the size is 40cm×40cm×50cm, the thickness is 3cm, and the interior is filled with thermal insulation materials. 4. based on the test method of the described test device of claim 1-3, it is characterized in that: The method includes the following steps: ① Sample preparation According to the target hydrate saturation, different concentrations of tetrahydrofuran aqueous solution were prepared, and the sample (4-5) was evacuated and saturated for 24 hours. 12), put the saturated sample (4-5) into a sealed bag and place it in a water bath (10) to cool down to -8°C for induction. Complete conversion of THF to THF hydrate; The preparation method of tetrahydrofuran aqueous solution is: m _H2O —the mass of water in the tetrahydrofuran aqueous solution; m _THF - the mass of tetrahydrofuran in the tetrahydrofuran aqueous solution; S _H - hydrate saturation; ②Sampling Considering the extra heat loss in the heat transfer process of the pressure chamber (4), the temperature of the water bath should have a certain degree of subcooling, and the temperature of the constant temperature water bath (10) should be lowered to -1°C; use the second sealing rubber ring (4- 7) Seal the saturated clay plate (4-6) on the pressure chamber base (4-10), open the first valve (V1), and drain the water in the water storage bottle (5) through the water inlet (4-9). The groove (4-12) and the pipeline are saturated; then, in order to discharge the liquid collected in the collecting cup (7) as the sample (4-5), open the second valve (V2) and the third valve ( V3), make the water pass through the pipeline and fill the gas collecting pipe (6), discharge the gas in the gas collecting pipe (6), close the first valve (V1); at the same time, the liquid collecting cup (7) should be sealed to prevent water loss; then Weigh the prefabricated saturated THF-containing hydrate sample (4-5), then place it on the clay plate (4-6), and place the first sealing rubber ring (4-2) into the pressure chamber upper cover ( 4-11) Seal the pressure chamber (4) after the notch and install the fixing screw (4-3); put the pressure chamber (4) into the constant temperature water bath box (10) as a whole, connect all the pipelines and close the water bath Box cover (4-11); ③Leak detection and pressurization Peel the balance (8) with the liquid collecting cup (7), open the data acquisition system () 9, open the air valve of the high-pressure nitrogen cylinder (1), and control the pressure reducing valve (2) and the pressure regulating pump (3) Enter the specified air pressure into the pressure chamber (4), fill in the applied air pressure value in the data acquisition system (9), and set the data acquisition time interval; if the pressure display does not change after the first-stage pressure is applied for 2 hours, it can be considered that the pressure chamber is airtight Good, the test can continue; ④Test After applying pressure, the water discharged from the sample (4-5) enters the liquid collecting cup (7) through the pipeline, and the data acquisition system (9) reads the reading of the balance (8) in real time to judge whether the suction force of the matrix has reached equilibrium; 8) After the reading is stable, the next level of pressure can be applied; ⑤Calculation According to the weight and water output of the saturated THF hydrate-containing samples (4-5) measured before the test, the water content after the suction balance of each stage is converted, and then the THF hydrate sediment is established according to the suction value and water content of each stage. The soil-water characteristic relationship curve.