Device and method for simulating pile-soil interface cyclic shear characteristics in hydrate replacement exploitation process

Abstract

The invention discloses a device and a method for simulating pile-soil interface cyclic shear characteristics in a hydrate replacement exploitation process, and particularly relates to the field of natural gas hydrate exploitation, the device comprises a supporting structure, a power mechanism, a high-pressure reaction kettle system, a control system, a data acquisition system and a data storage system, the high-pressure reaction kettle system comprises a high-pressure reaction kettle, an upper end cover is arranged at the top of the high-pressure reaction kettle, a lower end cover is arranged at the bottom of the high-pressure reaction kettle, high-strength screws are arranged in the upper end cover and the lower end cover, the high-strength screws are in threaded connection with the supporting structure, and sealing rings are connected to the outer sides of the bottoms of the upper end cover and the lower end cover in a sleeving manner. The device can accurately simulate a deep sea high-pressure environment, realizes a CO2 generation and replacement process of methane hydrate, can perform high-precision monotonous or cyclic shear test on a pile-soil interface in and after the process, effectively eliminates a rigid boundary effect, and obtains real and reliable interface mechanical parameters.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of natural gas hydrate exploitation, and more particularly, to a device and method for simulating cyclic shear characteristics of a pile-soil interface in a hydrate displacement exploitation process. BACKGROUND

[0002] Natural gas hydrate is a future clean energy with huge resource potential, and its green, safe and efficient exploitation is a global research hotspot. Among them, the technology of injecting CO2 to displace CH4 hydrate can realize the exploitation of CH4 gas and simultaneously store CO2, which has important environmental and economic value. However, in the displacement exploitation process, the generation and decomposition of hydrate can significantly change the mechanical properties of reservoir sediments, thereby posing a serious threat to the stability of pile structures (such as riser piles and production platform pile foundations) in the exploitation system. The shear characteristics of the interface between the pile foundation and the surrounding hydrate-containing sediments are the core parameters for evaluating the bearing capacity and long-term stability of the pile foundation.

[0003] At present, the traditional soil-structure interface shear apparatus mainly targets soil under normal temperature and pressure, and cannot simulate the high pressure and low temperature environment necessary for hydrate formation and decomposition, nor can it realize the complex physicochemical process of displacement exploitation. In addition, most existing devices are difficult to perform cyclic shear to simulate cyclic loads such as waves.

[0004] Although some mechanical testing devices for hydrate research have appeared in the prior art, their functions are focused on the compression or triaxial mechanical properties of sediments, and lack specialized testing functions for the interface characteristics of "structure-soil", especially the inability to simulate the penetration, extraction and cyclic shear behavior of pile foundations in hydrate-containing soils.

[0005] Therefore, the development of a multifunctional device that can integrate hydrate synthesis, CO2 displacement reaction, high-pressure and low-temperature environment simulation, and cyclic shear testing of the pile-soil interface within one set of equipment is of great significance for revealing the mechanical evolution law of the pile-soil interface during displacement exploitation and ensuring the safety of exploitation. SUMMARY

[0006] In order to overcome the above-mentioned defects of the prior art, embodiments of the present application provide a device for simulating cyclic shear characteristics of a pile-soil interface in a hydrate displacement exploitation process, which can accurately simulate a deep-sea high-pressure environment, realize the generation of methane hydrate and the CO2 displacement process, and can perform high-precision monotonic or cyclic shear testing on the pile-soil interface during and after the process, effectively eliminating the rigid boundary effect, and obtaining true and reliable interface mechanical parameters to solve the problems raised in the background art.

[0007] To achieve the above object, the present application provides the following technical solutions: The utility model provides a device that simulates the cyclic shearing characteristics of pile-soil interface in hydrate replacement exploitation process, including support structure, power mechanism, high pressure reaction kettle system, control system, data acquisition system, data storage system, the high pressure reaction kettle system includes high pressure reaction kettle, the top of high pressure reaction kettle is provided with upper end cover, the bottom of high pressure reaction kettle is provided with lower end cover, the inside of upper end cover and lower end cover all is provided with high strength screw, high strength screw is with support structure is in the form of thread connection arrangement, the bottom outside of upper end cover and lower end cover all is sleeved with sealing ring, the top of support structure is provided with upper gas outlet, the bottom of support structure is provided with lower gas inlet, the outside of support structure is provided with water bath jacket, the inside of water bath jacket is provided with temperature and pressure sensor, the outside of water bath jacket is covered with heat preservation layer, the outside of water bath jacket is provided with refrigerant interface, one end of refrigerant interface is connected with circulating water bath box, the bottom of lower gas inlet is provided with mass flowmeter, one end of mass flowmeter is provided with booster pump, one end of booster pump is provided with methane gas tank, the number of booster pump is two, one end of another booster pump is provided with gas tank.

[0008] In a preferred embodiment, the inner side of the support structure is provided with a lower compacted soil layer, the top of the lower compacted soil layer is provided with a stainless steel gas distribution plate, the bottom end of the stainless steel gas distribution plate is provided with a vacuum pump, the top of the stainless steel gas distribution plate is provided with a porous sediment soil sample layer, and the top of the porous sediment soil sample layer is provided with an upper compacted soil layer.

[0009] In a preferred embodiment, the inside of the support structure is provided with a model pile, the bottom end of the model pile penetrates through the lower end cover, the bottom of the lower end cover is fixedly connected with an adapter plate, a linear bearing is installed on the adapter plate, and the linear bearing is in sliding connection with the model pile.

[0010] In a preferred embodiment, the power mechanism is fixedly installed inside the support structure, the output end of the power mechanism is fixedly connected with a fish-eye joint bearing, the bottom end of the fish-eye joint bearing is fixedly connected with a second floating joint, the bottom of the second floating joint is fixedly connected with a tension and compression sensor, the bottom of the tension and compression sensor is fixedly connected with a first floating joint, and the first floating joint is fixedly connected to the top of the model pile.

[0011] In a preferred embodiment, the top end of the model pile is fixedly connected with an upper hoop rod, the top of the upper hoop rod is fixedly connected with a high-precision displacement meter, the bottom end of the model pile is fixedly connected with a lower hoop rod, and the bottom of the lower hoop rod is fixedly connected with a lower support rod.

[0012] In a preferred embodiment, the high-precision displacement meter is electrically connected to a data acquisition system, which is electrically connected to a data storage system, and the power mechanism is electrically connected to a control system.

[0013] In a preferred embodiment, the inner side of the support structure is fixedly connected to an upper support rod, which is connected to the high-precision displacement meter.

[0014] In a preferred embodiment, the top end of the upper gas outlet is provided with a back pressure valve, one end of which is electrically connected to a storage tank, and the top of the storage tank is electrically connected to a gas storage tank.

[0015] In a preferred embodiment, the inner side of the support structure is rotatably connected to a support member, the outer side of which is slidably connected to a sliding sleeve, one side of which is hingedly connected to a screw rod, the inner side of the support structure is slidably connected to a movable shaft column, the outer side of which is rotatably connected to a first sleeve, the screw rod is slidably connected to the inner side of the first sleeve, one end of the first sleeve is rotatably connected to a nut, the nut is threadedly connected to the screw rod, one end of the movable shaft column is threadedly connected to a fixed nut, the inner side of the support structure is rotatably connected to a second sleeve, one end of the second sleeve is rotatably connected to an adjusting nut, the inner side of the adjusting nut is threadedly connected to an auxiliary support member, and the high-strength screw is slidably connected to the inner side of the second sleeve.

[0016] The application also provides a method for simulating the cyclic shear characteristics of the pile-soil interface in the process of hydrate displacement mining, comprising the following steps: S1. Sample preparation and installation: install the model pile in the predetermined position; sequentially fill the lower dense soil layer, lay the stainless steel gas distribution plate in the high-pressure reaction kettle; fill the porous soil sample layer with standard quartz sand or kaolin, inject simulated pore water using the vacuum saturation method to ensure that the saturation is above 95%; fill the upper dense soil layer; install the upper end cover and tighten it; S2. System connection: connect the power mechanism, the tension and compression sensor, and all measurement sensors to the data acquisition system; S3. Methane hydrate generation: inject methane gas into the kettle at the required rate through the booster pump; control the water bath jacket temperature to the temperature required for hydrate generation through the circulating constant-temperature bath, and maintain the high pressure in the kettle in the hydrate stability zone through the gas injection system, react for five days to promote the generation of methane hydrate in the porous soil sample layer; S4. Interface shear test: drive the power mechanism through the control system to apply slow monotonic or cyclic displacement / load to the model pile, control the loading rate within the required range, and simultaneously record the tension and compression sensor, displacement meter, pressure, and temperature data through the data acquisition system to obtain the pile-soil interface shear characteristics of the pure methane hydrate soil body.

[0017] Technical effects and advantages of the present application: The present application can simulate deep-sea high-pressure environment accurately, realize the generation of methane hydrate and the replacement process of CO2, and can perform high-precision monotonic or cyclic shear test on the pile-soil interface during and after the process, effectively eliminate the rigid boundary effect, and obtain real and reliable interface mechanical parameters. BRIEF DESCRIPTION OF DRAWINGS

[0018] Figure 1 The structure diagram of the device for simulating the cyclic shear characteristics of the pile-soil interface during the hydrate replacement mining process; Figure 2 The structure diagram of the device for simulating the cyclic shear characteristics of the pile-soil interface during the hydrate replacement mining process; Figure 1 The structure diagram of the device for simulating the cyclic shear characteristics of the pile-soil interface during the hydrate replacement mining process; Figure 3 The structure diagram of the device for simulating the cyclic shear characteristics of the pile-soil interface during the hydrate replacement mining process.

[0019] The structure diagram of the device for simulating the cyclic shear characteristics of the pile-soil interface during the hydrate replacement mining process. DETAILED DESCRIPTION

[0020] The technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the drawings in the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, rather than all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those of ordinary skill in the art without creative labor fall within the scope of protection of the present application.

[0021] The technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the drawings in the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, rather than all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those of ordinary skill in the art without creative labor fall within the scope of protection of the present application. Figures 1-3As shown, the device for simulating the cyclic shear characteristics of the pile-soil interface in the process of hydrate replacement mining according to the embodiment of the application comprises a support structure 1, a power mechanism 2, a high-pressure reaction kettle system, a control system 24, a data acquisition system 25 and a data storage system 26. The high-pressure reaction kettle system comprises a high-pressure reaction kettle 3. The top of the high-pressure reaction kettle 3 is provided with an upper end cover 31. The bottom of the high-pressure reaction kettle 3 is provided with a lower end cover 32. High-strength screws 33 are arranged in the interiors of the upper end cover 31 and the lower end cover 32. The high-strength screws 33 are arranged in a threaded connection manner with the support structure 1. The bottom outer sides of the upper end cover 31 and the lower end cover 32 are both sleeved with sealing rings 34. An upper gas outlet 39 is formed in the top of the support structure 1. A lower gas inlet 38 is formed in the bottom of the support structure 1. A water bath jacket 35 is arranged on the outer side of the support structure 1. A temperature and pressure sensor 151 is arranged in the interior of the water bath jacket 35. A heat preservation layer 36 is coated on the outer side of the water bath jacket 35. A refrigerant interface 37 is arranged on the outer side of the water bath jacket 35. One end of the refrigerant interface 37 is in communication with a circulating water bath box 4. A mass flowmeter 19 is arranged at the bottom end of the lower gas inlet 38. One end of the mass flowmeter 19 is provided with a booster pump 18. One end of the booster pump 18 is provided with a methane gas tank 16. The number of the booster pumps 18 is two. One end of the other booster pump 18 is provided with a gas tank 17. The gas tank 17 is a carbon dioxide or nitrogen gas tank.

[0022] A lower dense soil layer 51 is arranged on the inner side of the support structure 1. A stainless steel gas distribution plate 15 is arranged at the top of the lower dense soil layer 51. A vacuum pump 20 is arranged at the bottom end of the stainless steel gas distribution plate 15. A porous sediment soil sample layer 52 is arranged at the top of the stainless steel gas distribution plate 15. An upper dense soil layer 53 is arranged at the top of the porous sediment soil sample layer 52. A model pile 6 is arranged in the interior of the support structure 1. The bottom end of the model pile 6 penetrates the lower end cover 32. An adapter plate is fixedly connected to the bottom of the lower end cover 32. A linear bearing 14 is installed on the adapter plate. The linear bearing 14 is arranged in a sliding connection manner with the model pile 6. The power mechanism 2 is fixedly installed in the interior of the support structure 1.

[0023] A fish-eye joint bearing 93 is fixedly connected to the output end of the power mechanism 2. A second floating joint 92 is fixedly connected to the bottom end of the fish-eye joint bearing 93. A tension and compression sensor 9 is fixedly connected to the bottom of the second floating joint 92. A first floating joint 91 is fixedly connected to the top of the model pile 6. An upper clamp rod 10 is fixedly connected to the top end of the model pile 6. A high-precision displacement meter 8 is fixedly connected to the top of the upper clamp rod 10. A lower clamp rod 12 is fixedly connected to the bottom end of the model pile 6. A lower support rod 13 is fixedly connected to the bottom of the lower clamp rod 12.

[0024] The high-precision displacement meter 8 is in electrical connection with the data acquisition system 25, the data acquisition system 25 is in electrical connection with the data storage system 26, the power mechanism 2 is in electrical connection with the control system 24, the inner side of the support structure 1 is fixedly connected with the upper supporting rod 11, the upper supporting rod 11 is connected with the high-precision displacement meter 8, the top end of the upper gas outlet 39 is provided with a back pressure valve 21, one end of the back pressure valve 21 is electrically connected with a storage tank 22, the storage tank 22 is a carbon dioxide or nitrogen gas tank, and the top of the storage tank 22 is electrically connected with a gas storage tank 23.

[0025] The high-pressure reaction kettle system is a core component, the high-pressure reaction kettle 3 is made of high-strength aluminum alloy, the upper end cover 31 and the lower end cover 32 are connected with the high-pressure reaction kettle 3 through pre-tightening high-strength screws 33, combined with a sealing ring 34, to form a sealed chamber that can withstand a pressure of more than 20 MPa, and the water bath jacket 35 is connected with the external circulating water bath box 4 through the refrigerant interface 37 and the inlet pipeline and the outlet pipeline, so that the temperature in the kettle can be accurately controlled within the range of-10 DEG C to 20 DEG C.

[0026] The lower compacted soil layer 51 can be compacted by kaolin or silty clay, a stainless steel gas distribution plate 15 with uniformly distributed micropores is laid thereon, the porous sediment soil sample layer 52 can be standard sand or quartz sand, the model pile 6 penetrates through all the soil layers, the linear bearing 14 can force the axis of the model pile 6 to coincide with the axis of the soil sample to meet the requirement of the verticality of the model pile 6 in the shear test, so that more accurate test data can be obtained, and the top end of the model pile 6 penetrates through the upper end cover 31.

[0027] The power mechanism 2 is a servo electric cylinder, which is vertically installed on the door-shaped support structure 1, the output rod is connected with one end of the tension-compression sensor 9 through the fisheye joint bearing 93 and the second floating joint 92, the other end of the tension-compression sensor 9 is connected with the top end of the model pile 6 through the first floating joint 91, and the universal hinged structure can effectively eliminate the centering error.

[0028] The tension-compression sensor 9 is a high-precision displacement meter 8 for measuring the displacement of the top end of the model pile 6, which is fixed to the support structure 1 through the upper supporting rod 11, the measuring rod is in contact with the upper hoop rod 10 fixed to the model pile 6, a high-precision displacement meter 8 for measuring the displacement of the bottom end of the model pile 6, which is fixed to the ground through the lower supporting rod 13, the measuring rod is in contact with the lower hoop rod 12 fixed to the model pile 6, a high-precision temperature and pressure sensor installed on the high-pressure reaction kettle 3, and all the sensors are connected to the data acquisition system 25.

[0029] The support structure 1 is rotationally connected with a support piece 27, the outer side of the support piece 27 is slidingly connected with a sliding sleeve 28, one side of the sliding sleeve 28 is hingedly connected with a screw rod 30, the inner side of the support structure 1 is slidingly connected with a movable shaft column 61, the outer side of the movable shaft column 61 is rotationally connected with a first sleeve 29, the screw rod 30 is slidingly connected in the inner side of the first sleeve 29, one end of the first sleeve 29 is rotationally connected with a nut, the nut is in threaded connection with the screw rod 30, one end of the movable shaft column 61 is in threaded connection with a fixed nut 62, the inner side of the support structure 1 is rotationally connected with a second sleeve 64, one end of the second sleeve 64 is rotationally connected with an adjusting nut 65, the inner side of the adjusting nut 65 is in threaded connection with an auxiliary support piece 63, and a high-strength screw 33 is slidingly connected in the inner side of the second sleeve 64.

[0030] Pulling the support piece 27 to overturn to one side of the high-pressure reaction kettle 3, the first sleeve 29 is followed to rotate, the sliding sleeve 28 is upwardly slid on the outer side of the support piece 27, the nut at one end of the first sleeve 29 is rotated, the screw rod 30 is gradually slid out of the inner side of the first sleeve 29, so that one end of the support piece 27 gradually approaches the high-pressure reaction kettle 3 and abuts against the high-pressure reaction kettle 3, the auxiliary support piece 63 is pulled out from the inner side of the support structure 1 and rotated, the auxiliary support piece 63 is gradually slid out of the inner side of the sealing ring 34, until one end of the auxiliary support piece 63 abuts against the high-pressure reaction kettle 3 and stops, so that the high-pressure reaction kettle 3 is abutted by the support piece 27 and the auxiliary support piece 63 on both sides, the stability between the support structure 1 and the high-pressure reaction kettle 3 is improved, the displacement of the support structure 1 or the high-pressure reaction kettle 3 is avoided, the instability of the connection between the power mechanism 2 and the model pile 6 and the damage of the components between the power mechanism 2 and the model pile 6 are avoided, the movable shaft column 61 is upwardly and downwardly slid by loosening the fixed nut 62, so that the height of the first sleeve 29 can be adjusted, the support piece 27 can be further adjusted in angle, and the support piece 27 can fully abut against the high-pressure reaction kettle 3.

[0031] The application also provides a method for simulating the cyclic shear characteristics of the pile-soil interface in the process of hydrate displacement mining, which comprises the following two core steps: Example one: cyclic interface shear characteristics test of pure methane hydrate soil body: The model pile 6 is installed according to the above device embodiment, and the soil sample is layered filled, the lower dense soil layer 51 and the upper dense soil layer 53 play a sealing role, preventing high-pressure gas from channeling along the pile-soil interface; The upper end cover 31 is installed, and each system is connected; The deionized water is injected into the kettle through the gas injection valve of the lower end cover 32, then the methane gas is injected until the pressure reaches 8MPa, and then the temperature in the kettle is controlled at 2℃ by starting the circulating thermostat; The temperature and pressure condition is maintained for five days, and the saturation of methane hydrate generated in the porous soil sample layer can be estimated by phase equilibrium calculation and volume change method. The power mechanism 2 is set in displacement control mode by the control system 24 to pull the model pile 6, the shear rate and shear displacement amplitude are 0.01 mm / s and 5 mm respectively, the cycle number is set to 200 times, and the large-scale interface cyclic shear test is carried out; the data acquisition system 25 synchronously records the pile top load, pile top and pile bottom displacement; The interface peak shear strength can be obtained according to the peak value of the tension-compression sensor 9, and the shear stress-displacement relationship can be obtained according to the displacement curve; Example two: test of interface characteristics after displacement mining: Steps 1-4 of the method embodiment are repeated to generate methane hydrate; The CO2 gas is injected through the gas / liquid injection valve, the pressure in the kettle is increased to MPa which is higher than the phase equilibrium pressure of CH4 hydrate at this temperature, the temperature is maintained at 2℃, the CO2 displacement CH4 reaction is carried out, and the reaction lasts for a certain time; After the reaction is completed, the interface cyclic shear test is carried out again with the shear rate and shear displacement amplitude being 0.1 mm / s and 5 mm respectively, the cycle number is set to 200 times, and all the data are recorded; The results of the method embodiment 1 and the present embodiment are compared, and the influence of CO2 displacement mining on the shear characteristics of the pile-soil interface can be analyzed.

[0032] Finally, it should be pointed out that: first, in the description of the present application, it should be pointed out that unless otherwise specified and limited, the terms "installation", "connection", "connection" should be understood broadly, which can be mechanical connection or electrical connection, or the communication between two elements, or direct connection, "up", "down", "left", "right" and the like are only used to indicate the relative positional relationship, when the absolute position of the described object changes, the relative positional relationship may change; Secondly: the drawings of the disclosed embodiments of the present application only involve the structures involved in the disclosed embodiments of the present application, other structures can refer to the usual design, and in the case of no conflict, the same embodiment and different embodiments of the present application can be combined with each other; Finally: the above only describes the preferred embodiments of the present application, and is not used to limit the present application, any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present application should be included in the protection scope of the present application.

Claims

1. A device for simulating the cyclic shear characteristics of the pile-soil interface during hydrate replacement mining, comprising a support structure (1), a power mechanism (2), a high-pressure reactor system, a control system (24), a data acquisition system (25), and a data storage system (26), characterized in that: The high-pressure reactor system includes a high-pressure reactor (3). The high-pressure reactor (3) has an upper end cover (31) at its top and a lower end cover (32) at its bottom. High-strength screws (33) are installed inside both the upper end cover (31) and the lower end cover (32). These high-strength screws (33) are threadedly connected to the support structure (1). Sealing rings (34) are fitted onto the outer bottom of both the upper end cover (31) and the lower end cover (32). An upper air outlet (39) is opened at the top of the support structure (1), and a lower air inlet (38) is opened at the bottom of the support structure (1). Water is provided on the outer side of the support structure (1). A water bath jacket (35) is provided with a temperature and pressure sensor (151) inside. The water bath jacket (35) is covered with an insulation layer (36) on the outside. A refrigerant interface (37) is provided on the outside of the water bath jacket (35). One end of the refrigerant interface (37) is connected to a circulating water bath tank (4). A mass flow meter (19) is provided at the bottom of the lower air inlet (38). A booster pump (18) is provided at one end of the mass flow meter (19). A methane gas tank (16) is provided at one end of the booster pump (18). The number of booster pumps (18) is set to two. A gas tank (17) is provided at one end of the other booster pump (18).

2. The device for simulating the cyclic shear characteristics of the pile-soil interface during hydrate replacement mining as described in claim 1, characterized in that: The inner side of the support structure (1) is provided with a lower compacted soil layer (51), the top of the lower compacted soil layer (51) is provided with a stainless steel gas distribution plate (15), the bottom of the stainless steel gas distribution plate (15) is provided with a vacuum pump (20), the top of the stainless steel gas distribution plate (15) is provided with a porous sediment soil sample layer (52), and the top of the porous sediment soil sample layer (52) is provided with an upper compacted soil layer (53).

3. The device for simulating the cyclic shear characteristics of the pile-soil interface during hydrate replacement mining as described in claim 1, characterized in that: The support structure (1) has a model pile (6) inside. The bottom end of the model pile (6) passes through the lower end cover (32). The bottom of the lower end cover (32) is fixedly connected to a transition plate. A linear bearing (14) is installed on the transition plate. The linear bearing (14) and the model pile (6) are slidably connected.

4. The device for simulating the cyclic shear characteristics of the pile-soil interface during hydrate replacement mining according to claim 3, characterized in that: The power mechanism (2) is fixedly installed inside the support structure (1). The output end of the power mechanism (2) is fixedly connected to a fisheye joint bearing (93). The bottom end of the fisheye joint bearing (93) is fixedly connected to a second floating joint (92). The bottom of the second floating joint (92) is fixedly connected to a tension and compression sensor (9). The bottom of the tension and compression sensor (9) is fixedly connected to a first floating joint (91). The first floating joint (91) is fixedly connected to the top of the model pile (6).

5. The device for simulating the cyclic shear characteristics of the pile-soil interface during hydrate replacement mining according to claim 3, characterized in that: The top of the model pile (6) is fixedly connected to an upper hoop (10), the top of the upper hoop (10) is fixedly connected to a high-precision displacement gauge (8), the bottom of the model pile (6) is fixedly connected to a lower hoop (12), and the bottom of the lower hoop (12) is fixedly connected to a lower support rod (13).

6. The device for simulating the cyclic shear characteristics of the pile-soil interface during hydrate replacement mining according to claim 5, characterized in that: The high-precision displacement gauge (8) is electrically connected to the data acquisition system (25), the data acquisition system (25) is electrically connected to the data storage system (26), and the power mechanism (2) is electrically connected to the control system (24).

7. The device for simulating the cyclic shear characteristics of the pile-soil interface during hydrate replacement mining according to claim 6, characterized in that: The inner side of the support structure (1) is fixedly connected to an upper support rod (11), which is connected to a high-precision displacement meter (8).

8. The device for simulating the cyclic shear characteristics of the pile-soil interface during hydrate replacement mining according to claim 1, characterized in that: A back pressure valve (21) is provided at the top of the upper air outlet (39), one end of the back pressure valve (21) is electrically connected to a storage tank (22), and the top of the storage tank (22) is electrically connected to a gas storage tank (23).

9. The device for simulating the cyclic shear characteristics of the pile-soil interface during hydrate replacement mining according to claim 1, characterized in that: The support structure (1) is rotatably connected to a support member (27), and a sliding sleeve (28) is slidably connected to the outside of the support member (27). A screw (30) is hinged to one side of the sliding sleeve (28). The support structure (1) is slidably connected to a movable shaft (61), and a first sleeve (29) is rotatably connected to the outside of the movable shaft (61). The screw (30) is slidably connected to the inside of the first sleeve (29). A nut is rotatably connected to one end of the first sleeve (29). The nut and the screw (30) are threadedly connected. A fixed nut (62) is threadedly connected to one end of the movable shaft (61). A second sleeve (64) is rotatably connected to the inside of the support structure (1). An adjusting nut (65) is rotatably connected to one end of the second sleeve (64). An auxiliary support member (63) is threadedly connected to the inside of the adjusting nut (65). A high-strength screw (33) is slidably connected to the inside of the second sleeve (64).

10. A method for simulating the cyclic shear characteristics of the pile-soil interface during hydrate replacement mining, applied to the apparatus for simulating the cyclic shear characteristics of the pile-soil interface during hydrate replacement mining as described in claim 1, characterized in that, Includes the following steps: S1. Sample preparation and installation: Install the model pile (6) in the predetermined position; fill the lower dense soil layer (51) and lay the stainless steel gas distribution plate (15) in the high-pressure reactor (3) in sequence; fill the porous sediment soil sample layer (52) with standard quartz sand or kaolin, inject simulated pore water in a vacuum saturation manner to ensure that the saturation is above 95%; fill the upper dense soil layer (53); install the upper end cap (31) and tighten it; S2. System connection: Connect the power mechanism (2), tension / compression sensor (9) and all measuring sensors to the data acquisition system (25); S3. Methane hydrate formation: Methane gas is injected into the reactor at the required rate by a booster pump (18); the temperature of the water bath jacket (35) is controlled to the required temperature for hydrate formation by a circulating constant temperature bath, and the high pressure in the reactor is maintained in the hydrate stable zone by the gas injection system. The reaction lasts for five days, which promotes the formation of methane hydrate in the porous sediment soil sample layer (52). S4. Interface shear test: The power mechanism (2) is driven by the control system (24) to apply slow monotonic or cyclic displacement / load to the model pile (6), and the loading rate is controlled within the required range. At the same time, the data acquisition system (25) synchronously records the tension and compression sensor (9), high-precision displacement meter (8), pressure and temperature data to obtain the pile-soil interface shear characteristics of pure methane hydrate soil.

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