JP5769107B2 - Test method for fracture strength of gas hydrate pellets - Google Patents

Description

  The present invention provides, for example, properties of gas hydrate when molding gas hydrate pellets in a gas hydrate production plant that produces natural gas hydrate present under the seabed in a state suitable for transportation and storage. The present invention relates to a test method for breaking strength performed to grasp the above.

  Natural gas hydrate (NGH), the main component of which is methane, exists under the seabed at a depth of 500 m or less in frozen land zones such as Siberia, Canada, and Alaska and in the continental area. This NGH is a water-like solid substance or clathrate hydrate that is composed of gas molecules such as methane and water molecules and is stable under low temperature and high pressure, and as clean energy that emits less carbon dioxide and air pollutants. It is attracting attention.

  Natural gas, after being liquefied, is stored and used as energy, but its production and storage are performed at an extremely low temperature of -162 ° C. On the other hand, natural gas hydrate has the advantage that it exhibits stable properties without being decomposed at −20 ° C. and can be handled as a solid. Because of these characteristics, it is possible to effectively use gas resources in undeveloped small and medium gas fields for reasons such as profitability existing all over the world, or short distance from small gas fields, small-scale transportation. In such a case, a natural gas hydrate system (NGH system) is expected in which natural gas is hydrated for transportation, storage, and regasification.

  In the NGH system, NGH suitable for transportation and storage is generated at NGH shipping bases such as small and medium gas fields, and transported to the desired NGH receiving base by transport ships and vehicles, etc., and the transported NGH is stored at the NGH receiving base. If necessary, it will be used as an energy source by the NGH gasifier. FIG. 6 is a schematic block diagram illustrating an example of the configuration of a gas hydrate generation plant used in the NGH shipping base. The mined source gas G is sufficiently mixed with water W in the generator 21 which is a high-pressure reaction vessel to be hydrated, and a low concentration gas hydrate (GH) slurry is generated. The generated GH slurry is supplied to the dehydrator 23 by the supply pump 22 and dehydrated to generate a high-concentration GH slurry. At this time, the dehydrator 23 is supplied to the lowermost part of the dehydrator 23. When the supplied GH slurry ascends the dehydrator 23, the GH slurry is dehydrated at a draining portion (a portion that separates hydrate particles and water by micropores, slits, etc.) provided in the middle of the dehydrator 23. It is taken out from the upper end part. The extracted gas hydrate is extracted as powdered GH powder. This GH powder is supplied to the pellet former 24 and granulated to form GH pellets having a size suitable for transportation and storage. Next, after being cooled by the cooler 25 to a temperature at which it does not decompose even under normal pressure, it is supplied to the decompressor 26. That is, from the generator 21 to the cooler 25, processing is performed under normal temperature and high pressure, which is a gas hydrate generation condition, and the cooler 25 and the depressurization device 26 are processed to a temperature that does not decompose even under normal pressure. Is done. Thereafter, the formed GH pellets are fed to a storage tank and stored.

  By the way, the applicant of the present application has proposed a manufacturing method and manufacturing apparatus for gas hydrate pellets that can manufacture pellets excellent in storability at low cost (see Patent Document 1). This method for producing gas hydrate pellets comprises dehydrating gas hydrate by compression molding means under its production conditions, and forming gas hydrate raw material gas and water between the gas hydrate particles into gas hydrate. , Which is molded into pellets. The compression molding means uses a briquetting roll having a plurality of pellet molding dies on the outer peripheral surface and comprising a pair of rolls rotating in opposite directions.

On the other hand, there are various types of GH pellet forming equipment, not limited to the above briquetting rolls, but in order to plan and design these equipment, the properties of the generated GH, especially during storage. and so that the efficiency of transportation is good, and what kind, etc. of the formed pellets, it is necessary to design the molding apparatus according to the specifications suitable for the nature and the like. Among the properties that the pellets want to grasp is the size of the internal friction force. That is, it is one of the parameters for grasping the strength against the fracture of the pellet, and in order to acquire this internal friction force, it is necessary to perform a triaxial compression test of the GH pellet. By this triaxial compression test, the main stress difference (axial stress σα−side stress σr) is determined from the axial compression force at the time of fracture of the specimen and the cross-sectional area of the specimen. This measurement is performed for at least three or more different lateral stresses, and the compressive strength (σα−σr) max, which is the maximum value of the principal stress difference obtained from the results, is set on the σ axis, as shown in FIG. In the same way, draw a stress circle of Mole with these as diameters. If the common tangent of the stress circle of these moldings is drawn, the intercept of the vertical axis can be obtained as the adhesive force and the gradient as the shear resistance angle.

  As the triaxial compression test, for example, “Soil Consolidation Drainage (CD) Triaxial Compression Test Method” described in Non-Patent Document 1 and others are defined as the Geotechnical Society Standards. As for GH pellets, it is preferable to conduct tests in accordance with the Geotechnical Society standards because qualitative and objective data can be obtained. Further, as this kind of soil test method, for example, there is a soil test method for civil engineering materials disclosed in Patent Document 2.

The triaxial compression tester for this triaxial compression test is configured such that a rubber sleeve that accommodates a specimen is accommodated in a triaxial pressure chamber composed of a pressure cylindrical container, and a load is applied in the axial direction of the specimen by a loading piston. the axial stress, there is a structure to impart lateral stress by adding a load from the surrounding rubber sleeve by pressurizing the pressurized liquid such as water filled in the triaxial pressure chamber.

JP 2007-270029 A JP 2010-54418 A

Geotechnical Society Standard JGA0524: 2000 “Consolidated Drainage (CD) Triaxial Compression Test Method”

  By the way, in the triaxial compression test method of Non-Patent Document 1, since earth and sand are used for the specimen, the triaxial pressure chamber can be tested by supplying water to the pressurized liquid, When the specimen is GH, in order to stabilize GH under normal pressure, it is necessary to cool to about −20 ° C., so the water filled in the triaxial pressure chamber is frozen. For this reason, the triaxial pressure chamber is filled with a refrigerant such as an antifreeze liquid instead of water. In addition, since GH is accompanied by unreacted water at the time of production, even if the test is performed in a state where this water is mixed, it cannot contribute to qualitative evaluation, and the accompanying water is excluded. Testing is required.

  Furthermore, if the refrigerant supplied to the triaxial pressure chamber infiltrates into the rubber sleeve containing the GH pellet as the specimen, the refrigerant may react with the GH pellet and decompose the GH pellet. Therefore, it is necessary to prevent the refrigerant from coming into contact with the specimen.

  Therefore, an object of the present invention is to provide a method for testing the breaking strength of GH pellets, which can reliably measure data when performing a triaxial compression test to grasp the breaking strength of GH pellets.

As a technical means for achieving the above object, according to the test method for fracture strength of gas hydrate pellets according to the present invention, a specimen is accommodated in a rubber sleeve made of rubber, and the rubber sleeve is made of a pressure cylindrical container. is accommodated in the axial pressure chamber, the specimen added to the load in the axial direction by loading the piston, a triaxial compression test machine for adding a load from increasing the pressure of the pressurized liquid triaxial pressure chamber side direction In the test method for the fracture strength of the gas hydrate pellets used, the rubber sleeve accommodates the gas hydrate pellets, and the triaxial pressure chamber is filled with a refrigerant that cools the gas hydrate to a temperature that does not decompose even under normal pressure, The internal pressure of the rubber sleeve and the internal pressure of the triaxial pressure chamber are increased to a pressure at which the gas hydrate does not decompose even at room temperature, and the triaxial compression tester And left to warm to temperature, and the vertical stress applying step of the axial load of the appropriate size by operating the loading piston is added to the gas hydrate pellets, the pressure of the pressurized liquid of the triaxial pressure chamber raised to an appropriate size and allowed to reach and horizontal stress applying step of adding a lateral load to the gas hydrate pellets, three principal stress direction load performed alternately into a desired size, the three principal stress direction load is in a state in desired size, it is characterized by measuring the breaking strength of the gas hydrate by adding an axial load in the loading piston.

  Pellets formed with GH produced by a GH production plant are accommodated in the rubber sleeve. At this time, the shape and dimensions of the formed GH pellets are necessary and sufficient to be accommodated in the rubber sleeve, and are the shapes and dimensions required for the triaxial compression tester that provides the GH pellets.

  When the GH pellet is supplied to the rubber sleeve, it is carried out at atmospheric pressure (normal pressure), so it is necessary to place the GH pellet in a low temperature atmosphere of about −20 ° C. so that the GH pellet does not decompose. For this reason, the inside of the rubber sleeve is cooled using a refrigerant such as an antifreeze liquid as the pressurized liquid in the triaxial pressure chamber. In this state, unreacted water at the time of production accompanying the GH pellet is frozen and mixed in an ice state. For this reason, it is not possible to test a GH pellet in this state. Therefore, it is necessary to thaw the ice and remove it from the GH pellet. In order to thaw ice, it is necessary to place GH under high pressure because the temperature of the GH pellet is raised to room temperature. That is, the pressurized liquid in the triaxial pressure chamber is pressurized to increase the lateral stress of the GH pellet, and pore water is added to the rubber sleeve to increase the water pressure, thereby placing the GH pellet under high pressure. At this time, it is sufficient to increase the pressure to the GH generation pressure (about 5.4 MPa). However, since the fracture strength test is performed, the pressure is higher than the generation pressure, for example, the pressure inside the triaxial pressure chamber and the rubber sleeve Is 7MPa. Alternatively, when performing the test, it is necessary to increase the lateral stress. For example, the triaxial pressure chamber is set to 7.5 MPa, and the pressure is set to 0.5 MPa larger than 7 MPa that is the pressure of water in the rubber sleeve. .

  Next, the temperature of the refrigerant in the triaxial pressure chamber is raised to room temperature, for example, room temperature of the test chamber. For this purpose, the triaxial compression tester is left to wait for the refrigerant temperature to rise.

  In a state where the temperature of the refrigerant has risen to room temperature, the ice mixed in the GH pellet is thawed. In this state, a vertical stress applying step is performed in which the load piston is operated to apply an appropriate amount of axial stress to the GH pellet. The magnitude of the axial stress which is the loading width of “appropriate size” at this time is selected according to the number of stages until the side stress reaches the test value, as will be described later. For example, if the number of steps is 10, the loading stress is divided into 10 steps and the axial stress of a desired magnitude is obtained. In the triaxial pressure tester, when the internal pressure of the triaxial pressure chamber increases, the pressure of the pore water in the rubber sleeve is controlled to be a balanced value.

  If an axial stress is applied with an appropriate loading width, a horizontal stress that increases the pressure of the pressurized liquid in the triaxial pressure chamber to increase the lateral stress of the GH pellets to an appropriate value above the previous value. An application process is performed. In this case, the “appropriately increased” boost width is increased stepwise before reaching the magnitude of the lateral stress to be tested (test value). The size is such that it can be increased to a desired lateral stress without breaking and with as few times as possible. Increasing the number of stepwise increases to the desired amount of side stress, that is, reducing the pressure increase width is preferable because it reduces the chance that the GH pellet is inadvertently destroyed, but the time required for pressure increase This increases the test time. Further, the boosting width varies depending on the generation state of GH to be subjected to the test, and the boosting width is appropriate for the GH.

  As described above, the vertical stress applying step for increasing the axial stress by the loading piston and the horizontal stress applying step for increasing the side stress due to the pressure increase in the triaxial pressure chamber are repeated an appropriate number of times, so that the side stress is increased. Set to the desired size. At this time, the difference between the lateral stress and the axial stress is taken as the test value for the lateral stress. For example, as described above, if the axial stress and the lateral stress are 7.0 MPa and 7.5 MPa in the initial stage, the difference of 0.5 MPa is applied to GH as the lateral stress. The test value of the lateral stress may be this difference. That is, when the test value of the side stress is 3.0 MPa, the vertical stress applying step and the horizontal stress applying step are alternately performed, and the difference between the side stress and the axial stress is 3.0 MPa. To be.

  Once the desired lateral stress is obtained, the loading piston is actuated to apply axial stress and measure the fracture strength.

  Thus, if the vertical stress applying step and the horizontal stress applying step are alternately performed and the fracture strength is measured in a plurality of values of the side stress, the stress circle of the molding can be drawn for each. The common tangent line is drawn, and the adhesive force and the shear resistance angle are required.

  According to a second aspect of the present invention, there is provided a method for testing the fracture strength of a gas hydrate pellet, wherein the static earth pressure coefficient in the vertical direction stress applying step is 0.5, and the static earth pressure coefficient in the horizontal direction stress applying step is 0.5. Is characterized by an upper limit of 1.0.

The static earth pressure coefficient (Κ ₀ ) is a ratio of these stresses as shown in Equation 1, where sv ′ is the axial stress and sh ′ is the horizontal stress.
Κ ₀ = sh '/ sv' [Formula 1]

That is, the vertical stress applying step and the horizontal stress applying step are performed in a range where the static earth pressure coefficient (Κ ₀ ) is in the range of 0.5 <Κ ₀ <1.0.

If the static earth pressure coefficient (Κ ₀ ) is 0.5 or more, it is the value that GH, which is the specimen to be measured, is in the elastic region, and when axial stress is applied so as to be less than this value In some cases, GH is inadvertently destroyed, making it impossible to perform a desired measurement. Further, when the static earth pressure coefficient ( ₀ ) is 1.0 or more, the amount of increase in the horizontal stress becomes too large, and there is a high possibility that the gas hydrate is destroyed.

  According to the method for testing the breaking strength of GH pellets according to the present invention, the breaking strength of GH pellets can be grasped, so the properties of the generated GH can be reliably grasped, and the pellet molding machine It can contribute to planning and design, can form GH pellets that are highly efficient for storage and transportation, etc., and can improve the utilization efficiency of GH.

It is a figure explaining the test method of the fracture strength of the gas hydrate pellet which concerns on this invention, (a)-(c) is a figure explaining the procedure of this test method, (d) is not based on this procedure It is a figure explaining the phenomenon which arises. It is a schematic structure figure showing an example of a triaxial compression tester. It is a graph which shows the relationship with the circumferential strain at the time of giving a horizontal direction stress to GH pellet by the test method which concerns on this invention. It is a graph which shows the relationship with the circumferential strain at the time of giving a horizontal direction stress to GH pellet irrespective of the test method which concerns on this invention. It is a graph explaining the relationship between a stress circle of a molding and a fracture line. It is a schematic block diagram explaining an example of the structure of the conventional gas hydrate production | generation plant utilized for the shipping base of a natural gas hydrate.

  Hereinafter, based on the preferred embodiments shown in the drawings, a method for testing the breaking strength of gas hydrate pellets according to the present invention will be specifically described. First, an outline of the structure and operation of the triaxial compression tester will be described.

  FIG. 2 shows a schematic structure of a triaxial compression tester 1 used for carrying out the test method according to Non-Patent Document 1. This triaxial compression tester 1 is provided with a triaxial pressure chamber 2 formed by a pressure cylinder and a rubber sleeve 3 made of a rubber cylinder disposed in the triaxial pressure chamber 2 for a destructive test. The specimen S to be provided is accommodated in the rubber sleeve 3. A specimen S accommodated in the rubber sleeve 3 is placed on the pedestal 4 with a placement plate 4a interposed therebetween, and a loading piston 5 is disposed on the top of the specimen S with a pressing plate 5a interposed therebetween. The specimen S is compressed by a piston rod 5b in which the loading piston 5 slides with a compression device (not shown).

  The triaxial pressure chamber 2 is filled with a pressurized liquid that imparts a lateral stress to the specimen S, and the pressure is adjusted by the compressor 6. In the case of a soil test, water is used as the pressurized liquid. The internal pressure of the triaxial pressure chamber 2 is acquired by the pressure gauge 7 or the like. Further, a back pressure pipe 6a is connected to the discharge port of the compressor 6 so as to communicate with the inside of the rubber sleeve 3, so that the inside of the rubber sleeve 3 can be pressurized. The back pressure is measured by a back pressure gauge 6b or the like disposed in the back pressure pipe 6a.

  In the case of the soil test, since the specimen S is earth and sand, the contained moisture is squeezed out by being pressurized, so that the discharge pipe 8 and the like for discharging the water exuded into the rubber sleeve 3 etc. Is in communication. In addition, a porous plate made of sintered metal or the like is used for the placement plate 4a and the pressing plate 5a so that the exudate can pass therethrough, and the exudate or the like is not reduced without abruptly reducing the internal pressure of the rubber sleeve 3. Can be discharged. The back pressure pipe 6a and the discharge pipe 8 are partially shared, and a switching valve 9 is interposed at an appropriate position.

  Further, the axial stress applied to the specimen S when the load piston 5 is pressed down is measured by a load meter 10a, a displacement meter 10b, or the like.

  A description will be given of a fracture strength test method by a triaxial compression test using the above-described triaxial compression tester 1 and using a GH pellet as a specimen S.

  The GH pellets are formed into a shape and size that can be accommodated in the rubber sleeve 3 by a pellet molding machine such as a pelletizer. Since the rubber sleeve 3 has a cylindrical shape, the GH pellet also has a substantially cylindrical shape. The GH pellet is decomposed and unstable unless it is cooled to about −20 ° C. under normal pressure. Since the triaxial compression tester is in a room temperature atmosphere such as a test room, it is necessary to cool the GH. In addition, since the triaxial pressure chamber 2 is cooled to −20 ° C. and is filled with water as a pressurized liquid, it freezes. Therefore, as the pressurized liquid, a refrigerant such as an antifreeze liquid cooled to about −20 ° C. is used. Fill.

  Next, a test method for the breaking strength of the GH pellet according to the present invention will be described.

  In the state where the triaxial pressure chamber 2 is filled with a refrigerant such as an antifreeze liquid cooled to about −20 ° C., a GH pellet as a specimen formed into a cylindrical shape is accommodated. In this GH pellet, unreacted water out of the water supplied to react with methane gas during production is mixed in a frozen state. In tests conducted in the presence of this ice, it is not qualitative and the objectivity may not be guaranteed, so it is necessary to remove this ice, and it is necessary to raise the temperature of the GH pellet to room temperature. . When GH pellets are placed in a room temperature atmosphere, it is necessary to avoid decomposition under high pressure conditions. For this reason, the pressure inside the triaxial pressure chamber 2 and the rubber sleeve 3 is increased. That is, the compressor 3 is operated to increase the internal pressure of the triaxial pressure chamber 2, and the back pressure pipe 6a is communicated with the inside of the rubber sleeve 3 by opening and closing an appropriate switching valve 9, so that the inside of the rubber sleeve 3 is opened. Supply pore water and pressurize. Further, since the GH generation pressure is about 5.4 MPa, it is sufficient to increase the pressure further. For example, the internal pressure of the triaxial pressure chamber 2 is 7.5 MPa and the internal pressure of the rubber sleeve 3 is 7.0 MPa. By increasing the internal pressure of the pressure chamber 2, a horizontal stress can be applied in advance to the GH pellet. In addition, you may put under the same pressure without providing a pressure difference.

  With GH placed under high pressure, it waits until the refrigerant in the triaxial compression chamber 2 reaches room temperature. When the refrigerant in the triaxial pressure chamber 2 reaches room temperature, GH also rises to room temperature, and the ice mixed inside is thawed to become water. This water is discharged from the discharge pipe 8 while maintaining the pressure in the rubber sleeve 3.

  FIG. 1A shows a state where the triaxial pressure chamber 2 and the rubber sleeve 3 are raised to room temperature. In the triaxial compression test in the case of soil, the internal pressure of the triaxial pressure chamber 2 is increased to apply a lateral stress to the specimen S, and in the state where the desired lateral stress is obtained, A destructive test is performed by applying axial stress at 5. In order to carry out this method with GH as it is, when the lateral stress is increased to a desired magnitude at once, as shown in FIG. 1 (d), the diameter of GH is reduced and the rubber sleeve 3 is loaded. The piston 5 dropped out and the GH pellet contacted the refrigerant in the triaxial pressure chamber 2. Because this refrigerant uses an alcohol-based antifreeze, the GH pellets were decomposed, making it impossible to perform a triaxial compression test.

Therefore, as shown in FIG. 1 (b), performing the vertical stress applying step of applying an axial stress by adding an axial load of appropriate size said the loading piston 5 is actuated to GH, Slightly increases axial stress. At this time, the GH pellet is considered to slightly expand in diameter due to the axial load. Next, as shown in FIG. 1 (c), a horizontal stress applying step is performed in which the pressure of the refrigerant in the triaxial pressure chamber 2 is slightly increased to add a lateral load to the GH pellet. By the added lateral load at this time, considered to enlarged the GH pellets it is restored to the original size, Therefore, it is not the rubber sleeve 3 from falling out loading piston 5.

Wherein the vertical stress applying step, so as not to fall below the stationary earth pressure coefficient (Kappa0) is 0.5, i.e., 0.5 is added an axial load to the lower limit, in the horizontal direction stress applying step, a stationary earth pressure coefficient ( The side load is applied by increasing the pressure in the triaxial pressure chamber 2 so that Κ0) does not exceed 1.0, that is, 1.0 is the upper limit.

In other words, when the static earth pressure coefficient (Κ ₀ ) is within the range of 0.5 <Κ ₀ <1.0, the vertical stress applying step and the horizontal stress applying step are performed, and the three principal stress direction stresses are set to a desired magnitude. Until it becomes, it repeats performing these vertical direction stress provision process and horizontal direction stress provision process alternately. At this time, the vertical stress and the horizontal stress are increased little by little.
The static earth pressure coefficient (Κ ₀ ) is a ratio of these stresses as shown in Equation 1, where sv ′ is the axial stress and sh ′ is the horizontal stress.
Κ ₀ = sh '/ sv' [Formula 1]

  When the horizontal stress becomes a desired magnitude, the load piston 5 described above is operated to measure the breaking strength of the GH pellet. The horizontal stress value is measured by, for example, an instruction from the pressure gauge 7, and the axial stress value is measured by, for example, an instruction from the load gauge 10a or the displacement gauge 10b.

By performing the above operations for different values of horizontal stress, the main stress difference, axial stress, ie, vertical stress σ _α , and lateral stress, ie, horizontal direction, are determined from the axial compression force and cross-sectional area at the time of fracture of the GH pellet. The difference (σ _α −σ _r ) from the stress σ _r is obtained, and the compressive strength (σ _α −σ _r ) max, which is the maximum value of the main stress difference, is set on the σ axis, as shown in FIG. Draw a stress circle with a diameter of. If the common tangent of the stress circle of these moldings is drawn, the intercept of the vertical axis can be obtained as the adhesive force and the gradient as the shear resistance angle.

FIG. 3 shows a change in the circumferential strain Εpr [%] of the GH pellet when the horizontal direction stress sh ′ [MPa] is applied in the procedure of the present invention. At this time, the upper limit of the static earth pressure coefficient (Κ0) is 0.7, and the vertical stress applying step and the horizontal stress applying step are performed in the range of 0.5 <Κ0 <0.7. Further, FIG. 4 shows a change in the circumferential strain Εpr [%] of the GH pellet when the horizontal stress sh ′ [MPa] is applied regardless of the procedure of the present invention.

  As shown in FIG. 4, when the procedure of the present invention is not used, that is, when the horizontal stress sh ′ is continuously applied, the circumferential strain Εpr is from 0.6 to 0.7 [MPa] to 1.0 [MPa]. However, the circumferential strain Εpr suddenly exceeded 10 [%] while exceeding 1.0 [MPa], and the test could not be continued.

  On the other hand, in the case of the procedure of the present invention, even when the horizontal stress sh ′ increased to 3.0 [MPa], the circumferential strain Εpr was 2.0 [%] and the test could be continued. .

  According to the method for testing the breaking strength of GH pellets according to the present invention, the breaking strength of GH pellets can be measured as accurately as possible, and therefore it is possible to determine the internal friction force, which is superior in storage and transportation. Contributes to the formation of pellets.

S Specimen 1 Triaxial compression tester 2 Triaxial pressure chamber 3 Rubber sleeve 5 Loading piston 6 Compressor
6a Back pressure pipe 7 Pressure gauge 8 Drain pipe 9 Switching valve
10a load cell
10b Displacement meter

Claims (2)

The specimen is accommodated in a rubber rubber sleeve, and the rubber sleeve is accommodated in a triaxial pressure chamber composed of a pressure cylindrical container. A load is applied to the specimen in the axial direction by a loading piston, and the specimen is added in the triaxial pressure chamber. In the test method of fracture strength of gas hydrate pellets using a triaxial compression tester that increases the pressure of the pressurized liquid and adds a load from the side direction,
Gas hydrate pellets are housed in the rubber sleeve,
The triaxial pressure chamber is filled with a refrigerant that cools the gas hydrate to a temperature that does not decompose even under normal pressure,
Increasing the internal pressure of the rubber sleeve and the internal pressure of the triaxial pressure chamber to a pressure at which the gas hydrate does not decompose even at room temperature,
The triaxial compression tester is allowed to stand until the refrigerant temperature rises to room temperature,
The vertical stress applying step of the axial load of the appropriate size by operating the loading piston is added to the gas hydrate pellets, the triaxial an elevated by laterally the pressure of the pressurized liquid in the pressure chamber to the appropriate size and horizontal stress applying step of a load added to the gas hydrate pellets, three principal stress direction load performed alternately to reach the desired size,
While three principal stress direction load is in the desired size, the method of testing breaking strength of the gas hydrate pellets, characterized in that to measure the breaking strength of the gas hydrate by adding an axial load in the loading piston . The static earth pressure coefficient in the vertical stress application step, with 0.5 as the lower limit,
The test method for the fracture strength of a gas hydrate pellet according to claim 1, wherein the static earth pressure coefficient in the horizontal stress applying step is 1.0 as an upper limit.

Images