A large-load core holder and true triaxial experimental device capable of combining CT scanning

Abstract

The invention discloses a large-load core holder and a true triaxial test device that can be combined with CT scanning. The large-load core holder includes an upper force transmission end, a lower force transmission end and a cylinder. A sample cavity and four capsule accommodating cavities are arranged in the hollow cavity of the cylinder. The two capsule bodies located in the left and right capsule accommodating cavities are used for flexible loading and force transmission in the X direction, and the two capsule bodies located in the front and rear capsule accommodating cavities are used for flexible loading and force transmission in the Y direction. Each capsule body has an inverted skirt interface, and each inverted skirt interface is interference-connected with a sealing plug. Each sealing plug is provided with an injection tube connected to the upper cavity of the capsule body, and all the injection tubes are passed through the upper force transmission end; and a Z-direction loading piston rod is provided in the center of the lower force transmission end. The large-load true triaxial test device includes the large-load core holder, a Z-direction loading cylinder, and X-direction, Y-direction, and Z-direction hydraulic loading systems.

Description

Technical Field

[0001] The invention relates to a large-load core holder and a true triaxial experimental device capable of combining CT scanning, and belongs to the field of rock mechanics and engineering technology. Background Art

[0002] Since the permeability, mechanical properties, crack growth law, etc. of oil and gas reservoir rocks have obvious heterogeneity and anisotropy, it is of great significance to study the seepage characteristics, mechanical properties and crack growth mechanism of cores under true triaxial stress state.

[0003] In addition, because CT nondestructive scanning technology can dynamically characterize the microstructure inside the rock, it is an effective method to reveal the seepage characteristics of the core, the mechanism of crack growth, etc., and it will not damage the internal structure of the rock. Therefore, CT scanning technology has been widely used in the field of oil and gas field development at home and abroad in recent years. The development of modern engineering technology and the theoretical research of rock and soil mechanics are in urgent need of experimental equipment that can realize CT scanning while conducting true triaxial experiments, so as to realize all-round dynamic monitoring of the structural changes inside the rock sample, intuitively understand the local changes, subtle changes and change trends of the internal structure of the rock sample, and facilitate the grasp of the properties of the rock sample under different stress conditions, and understand the real dynamic deformation and failure mechanism of the rock from a microscopic perspective. During CT scanning, a high-precision rotating table is required to realize the relative 360° rotation of the X-ray imaging component and the sample. Therefore, to realize the combined use with CT scanning equipment, not only the true triaxial experimental device needs to be miniaturized and lightweight, but also the core holder needs to be able to realize independent large load loading in three axes without affecting the penetration of X-rays.

[0004] Although Chinese Patent 201510577392.2 discloses a rock true triaxial test system with a CT real-time scanning system, including a true triaxial pressure box, a true triaxial mainframe, a loading device, and a CT scanning device; the true triaxial mainframe includes a bottom plate, a top plate, and supports on the bottom plate and columns; the loading device includes a reaction device, a jack, and a measuring device; the pressure box, the column, and the reaction device located in the scanning area of ​​the CT scanning device are all made of carbon fiber materials; the patent solves the problem that X-rays cannot penetrate traditional true triaxial testing machines by using a specially designed lateral loading system, a carbon fiber force transmission plate, and a column in the CT scanning area, and realizes the real-time coordination of rock true triaxial and CT scanning tests, but the patent can only achieve a loading force of 100kN (equivalent to 0.1 MPa) in each of the three axes, which is far from meeting the loading requirements on standard rock samples and cannot be actually applied. It can only be used to do some approximate simulation tests on some very small samples.

[0005] Chinese patent application 201910088014.6 discloses a true triaxial stress-seepage coupling test device suitable for X-CT. The patent sets five capsules in the core holder to achieve independent flexible loading on the three axial directions of the core. Although the patent can realize the combination of the true triaxial stress-seepage coupling test device and the CT scanning device, it is known from the prior art that the existing force transmission capsules are all sac-shaped objects made of high-elastic rubber. When used for hydraulic loading, one or more liquid inlet and outlet interfaces need to be set on the capsule body. The interface on the existing force transmission capsule body is a circular opening. The circular opening interface and the external joint with pressurized liquid are basically connected by bolt and nut compression sealing structure. For details, please refer to Figure 1 As shown, that is, there is a circular opening on the capsule body ①. The high elasticity of the capsule body material (generally rubber material) is used to expand the opening first, and then the injection tube ④ pre-installed with the lower clamping nut ② and the lower gasket ③ is extended into the capsule body ①, and then the upper gasket ⑤ is added and the upper clamping nut ⑥ is tightened, so that the upper and lower gaskets press the rubber wall at the interface of the capsule body to make it pre-deformed so that it can be sealed when pressurized liquid is added. Since this sealing connection structure will generate great stress locally, and there is a clear boundary between the upper and lower gaskets and the capsule wall, so that the rubber wall at the interface of the capsule body will be sheared, therefore, when the liquid pressure reaches several MPa or even below one MPa, shear rupture may occur in this local area, so that the pressure can no longer be increased. That is to say, the sealing connection structure between the existing capsule body interface and the external joint of the pressurized liquid means that the pressure inside the capsule can only reach a few MPa at most. When the pressure increases, the rubber at the capsule entrance will be locally squeezed or sheared by the high-pressure metal gasket, resulting in local rupture and loading failure. Therefore, the core clamp described in this patent is still unable to achieve the loading requirements of ultra-large loads in three axes.

[0006] Chinese patent application 202010911726.6 discloses a rigid-flexible true triaxial grouting seepage coupling test device for CT scanning. The first principal stress loading system and the second principal stress loading system in the device are both rigid loading systems, and the third principal stress loading system is a flexible system. Although the patent eliminates the corner stress concentration problem caused by three-way stress loading by adopting a composite loading form of two-way rigid loading and one-way flexible loading, the patent has only one flexible loading direction, so CT scanning and photography can only be achieved in this direction. The sample needs to be loaded to a certain load first, and then all connected pipes are removed before the true triaxial test box can be placed in the CT scanning equipment for CT scanning in this direction. Not only can the sample not be scanned in all directions, but it can still only achieve a loading force of several MPa (4 to 7 MPa disclosed in the article).

[0007] In summary, it can be seen that so far, there is no report in the existing technology that can achieve miniaturization and lightweight, while also realizing independent ultra-large loads (up to tens of MPa, or even hundreds of MPa pressure) in three axes, and can be combined with CT scanning. Large-load core holder and true triaxial experimental device. Summary of the invention

[0008] In view of the above-mentioned problems existing in the prior art, the purpose of the present invention is to provide a large-load core holder and a true triaxial experimental device which can be miniaturized and lightweight while realizing independent ultra-large load (up to tens of MPa or even hundreds of MPa pressure) loading in three axes and can be combined with CT scanning.

[0009] In order to achieve the above-mentioned invention object, the present invention adopts the following technical scheme:

[0010] A large-load core clamp capable of combining with CT scanning comprises an uploading end, a downloading end and a cylinder with both ends open and made of non-metallic material that can be penetrated by X-rays, a circumferential pressure-bearing carbon fiber sleeve is arranged in the outer circumferential direction of the cylinder, at least one pair of axial pressure-bearing carbon fiber rings are symmetrically arranged in the outer axis of the cylinder, a sample cavity and four capsule accommodating cavities symmetrically distributed on the left, right, front and rear sides of the sample cavity are arranged in the hollow cavity of the cylinder, wherein: two capsule bodies located in the left and right capsule accommodating cavities are used for flexible loading and force transmission in the X direction, and two capsule bodies located in the front and rear capsule accommodating cavities are used for flexible loading and force transmission in the Y direction; each capsule body is provided with an inverted skirt interface, each inverted skirt interface is interference-connected with a sealing plug, each sealing plug is penetrated with an injection tube connected with the upper cavity of the capsule body, and all the injection tubes are penetrated out of the uploading end; and a Z-direction loading piston rod is penetrated in the center of the downloading end.

[0011] In a preferred embodiment, elastic buffer pads and rigid pressure blocks are provided on the top and bottom of each capsule body.

[0012] In a preferred embodiment, an axial rigid pressing block is provided between the upper force transmitting end and the end of the sample cavity.

[0013] In a preferred embodiment, the inward-turned skirt interface is an embedded cylindrical through hole, and the sealing plug is a metal cylinder.

[0014] In a further preferred embodiment, one or more external convex annular bands are provided on the outer peripheral surface of the sealing plug.

[0015] In a preferred embodiment, the force transmission surface of the capsule body is a flat surface or a curved surface.

[0016] In one implementation scheme, at least one group of centrally symmetrical cantilevers are fixedly provided on the outer periphery of the upper force transmitting end and the outer periphery of the lower force transmitting end, and mirror symmetry is formed between the upper cantilever and the lower cantilever, and an axial pressure-bearing carbon fiber ring is provided on each group of upper and lower cantilevers forming the mirror symmetry.

[0017] A preferred solution is that the upper and lower arc ends of each axially pressure-bearing carbon fiber ring are respectively fixed in the opening of a U-shaped limit seat, and the distance between the bottom surface of the upper U-shaped limit seat and the top surface of the lower U-shaped limit seat is adapted to the distance between the top surface of the upper cantilever and the bottom surface of the lower cantilever, thereby ensuring that each axially pressure-bearing carbon fiber ring can tighten the upper and lower cantilevers and can be easily loaded and unloaded.

[0018] According to a further preferred embodiment, each cantilever is detachably connected with a limit baffle plate which is closely attached to the outer side of the corresponding U-shaped limit seat.

[0019] A further preferred solution is that an upper limit baffle plate is detachably connected on the upper cantilever and is tightly attached to the outer side of the upper U-shaped limit seat, and a lower limit baffle plate is detachably connected on the lower cantilever and is tightly attached to the outer side of the lower U-shaped limit seat, and the upper limit baffle plate and the lower limit baffle plate are in a mirror-symmetrical relationship.

[0020] A large-load true triaxial experimental device capable of combining CT scanning comprises the large-load core clamp and a Z-direction loading cylinder, a Z-direction hydraulic loading system, an X-direction hydraulic loading system, and a Y-direction hydraulic loading system. The Z-direction loading cylinder is sealedly connected to a lower force transmission end head, a piston is arranged in the Z-direction loading cylinder, a Z-direction loading piston rod is fixedly connected to the piston, a hydraulic delivery channel communicating with the piston cavity is arranged at the bottom of the Z-direction loading cylinder, the hydraulic delivery channel is connected to the Z-direction hydraulic loading system through a pressure-resistant hose, the injection pipes on two capsule bodies used for X-direction flexible loading and force transmission in the large-load core clamp are connected to the X-direction hydraulic loading system through a pressure-resistant hose, and the injection pipes on two capsule bodies used for Y-direction flexible loading and force transmission in the large-load core clamp are connected to the Y-direction hydraulic loading system through a pressure-resistant hose.

[0021] In one implementation scheme, the Z-axis loading cylinder and the lower force transmission end are connected via a bidirectional nut.

[0022] In a preferred embodiment, a buffer spacer is provided between the force transmission surface of the capsule body and the force bearing surface of the sample.

[0023] In a further preferred embodiment, the buffer spacer is made of non-metallic material.

[0024] Compared with the prior art, the present invention has the following beneficial technical effects:

[0025] 1. The large-load core holder of the present invention has a circumferential pressure-bearing carbon fiber sleeve and an axial pressure-bearing carbon fiber ring on the outside of the cylinder, and four capsule bodies are provided on the left, right, front and rear sides of the sample cavity, so that independent flexible loading in the X and Y directions is achieved without affecting the penetration of CT scanning rays, so that the large-load core holder can be used in combination with CT scanning equipment;

[0026] 2. The present invention creatively arranges an inverted skirt interface on the capsule body, thereby cleverly avoiding the shear damage of the rubber wall at the interface of the capsule body by the pressurized liquid, so that the pressure resistance of the capsule body is no longer limited by the interface, but only depends on the crushing strength of the rubber material constituting the capsule body. By simply selecting a rubber material with the required crushing strength to make the capsule body, the capsule body can meet the loading requirements of ultra-high hydraulic pressure of up to tens of MPa or even hundreds of MPa. Therefore, the present invention cleverly solves the problem of large-load flexible loading, and makes the loading pressure of the capsule body relatively lower than that of the prior art ( The maximum load that can be achieved is a few MPa) can be achieved by dozens or even hundreds of times (up to tens of MPa, or even hundreds of MPa). Experiments have shown that the true triaxial test device formed by the large-load core holder provided by the present invention can make the flexible loading force in the X and Y directions up to 100 MPa or more, and because the Z direction is rigidly loaded, the Z-direction loading force can be up to 500 MPa or more. Therefore, the true triaxial test device provided by the present invention can fully meet the requirements of the large-load simulation test of the core under the true triaxial stress state, and has significant progress compared with the prior art.

[0027] 3. Since the core holder of the present invention mainly adopts non-metallic composite materials such as carbon fiber, engineering plastics, etc., and the core holder of the present invention can realize ultra-high hydraulic loading in three axes, therefore, under the condition of realizing the same hydraulic loading, the weight of the entire true triaxial test device can be reduced to a few tenths of the traditional true triaxial test device. For example, if the sample specification is 50*50*100mm, the weight of the true triaxial test device provided by the present invention is only 50kg; if the sample specification is 75*75*150mm, the weight of the true triaxial test device provided by the present invention is about 100kg; it can be seen that the present invention can easily realize the lightweight and miniaturization of the core holder and the true triaxial test device, which is of great significance for realizing the combination of the true triaxial test device and the CT scanning technology;

[0028] In summary, compared with the prior art, the present invention not only produces unexpected technical effects, but also produces significant progress, and is of great value in exploring the real dynamic physical property changes of rock samples under true triaxial stress state. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Figure 1 It is a structural schematic diagram of the existing force transmission capsule described in the background technology;

[0030] Figure 2 It is a schematic diagram of the three-dimensional structure of a large-load core holder capable of combining CT scanning provided by an embodiment of the present invention;

[0031] Figure 3 yes Figure 2 A longitudinal cross-sectional view of a heavy-duty core holder is shown;

[0032] Figure 4 yes Figure 3 A partial enlarged view of

[0033] Figure 5 It is a structural schematic diagram of a cylinder provided by an embodiment of the present invention;

[0034] Figure 6 is a partial cross-sectional view of a capsule body provided by an embodiment of the present invention;

[0035] Figure 7 is a schematic structural diagram of a capsule body provided by an embodiment of the present invention after a sealing plug is installed;

[0036] Figure 8 It is a schematic diagram showing the force of the inverted skirt interface described in the embodiment of the present invention after the pressurized liquid is injected;

[0037] Fig. 9 is a schematic structural diagram of a sealing plug provided by an embodiment of the present invention;

[0038] Fig.10 It is a schematic diagram of the connection structure between the inverted skirt interface and the sealing plug described in an embodiment of the present invention;

[0039] Fig.11 is a schematic structural diagram of an axially pressure-bearing carbon fiber ring provided by an embodiment of the present invention;

[0040] Fig.12 is a schematic cross-sectional structural diagram of an axially pressure-bearing carbon fiber ring provided by an embodiment of the present invention;

[0041] Fig.13 is a schematic structural diagram of a U-shaped limit seat described in an embodiment of the present invention;

[0042] Fig.14 It is a schematic diagram of the structure of the axial pressure-bearing carbon fiber ring provided by the embodiment of the present invention for realizing disassembly and assembly;

[0043] Fig.15 It is a structural schematic diagram of a large-load true triaxial experimental device that can be combined with CT scanning provided by an embodiment of the present invention;

[0044] Fig.16It is a schematic structural diagram of a large-load true triaxial experimental device provided by an embodiment of the present invention when used in combination with CT scanning.

[0045] The numbers in the figure are as follows:

[0046] ①, capsule body; ②, lower clamping nut; ③, lower gasket; ④, injection tube; ⑤, upper gasket; ⑥, upper clamping nut;

[0047] 01. Upper force transmission end; 02. Lower force transmission end; 03. Cylinder; 031. Sample cavity; 032a. Left capsule accommodating cavity; 032b. Right capsule accommodating cavity; 032c. Front capsule accommodating cavity; 032d. Back capsule accommodating cavity; 04. Circumferential pressure-bearing carbon fiber sleeve; 05. Axial pressure-bearing carbon fiber ring; 06. Capsule body; 06a. Left capsule body; 06b. Right capsule body; 061. Inverted skirt interface; 0611. Inverted skirt; 062. Force transmission surface; 07. Elastic buffer gasket; 08. Rigid pressure block; 09. Shaft To the rigid pressing block; 010, Z-direction loading piston rod; 011, sealing plug; 0111, outer convex ring belt; 012, injection pipe; 012a, injection pipe on the two capsule bodies constituting the flexible loading in the X direction; 012b, injection pipe on the two capsule bodies constituting the flexible loading in the Y direction; 013, cantilever; 013a, upper cantilever; 013b, lower cantilever; 014, U-shaped limit seat; 014a; upper U-shaped limit seat; 014b, lower U-shaped limit seat; 015, limit baffle; 015a, upper limit baffle; 015b, lower limit baffle;

[0048] 1. Large-load core holder; 1-1. Cylinder section; 2. Z-direction loading cylinder; 21. Piston; 22. Hydraulic delivery channel; 3. Z-direction hydraulic loading system; 4. X-direction hydraulic loading system; 5. Y-direction hydraulic loading system; 6. Bidirectional nut; 7. CT rotating table; 8. CT ray source; 9. CT photosensitive plate; 10. Sample; 101. Stress-bearing surface; 11. Buffer spacer. DETAILED DESCRIPTION

[0049] The technical solution of the present invention is further described in detail below in conjunction with the accompanying drawings and embodiments. It should be understood that the definitions of the terms "upper", "lower", "left", "right", "front", "back", "top", and "bottom" in this application are all relative, and the definitions in the embodiments are only for the convenience of description or simplified description, rather than indicating or implying that the relationship referred to is limited to that described in the embodiments, and therefore cannot be understood as a limitation of the present application.

[0050] Example

[0051] Please combine Figures 2 to 5As shown: This embodiment provides a large-load core holder 1 that can be combined with CT scanning, including an upper force transmitting end 01, a lower force transmitting end 02 and a cylinder 03 with both ends open and made of a non-metallic material that can be penetrated by X-rays, a circumferential pressure-bearing carbon fiber sleeve 04 is provided in the outer circumference of the cylinder 03, at least one pair of axial pressure-bearing carbon fiber rings 05 are symmetrically provided in the outer axis of the cylinder 03, and a sample cavity 031 and a left capsule accommodating cavity 032a symmetrically distributed on the left side of the sample cavity 031, a right capsule accommodating cavity 032b distributed on the right side, a front capsule accommodating cavity 032c distributed on the front side, and a rear capsule accommodating cavity distributed on the rear side are provided in the hollow cavity of the cylinder 03. 032d, wherein: the left capsule body 06a located in the left capsule accommodating cavity 032a and the right capsule body 06b located in the right capsule accommodating cavity 032b are used for flexible loading and force transmission in the X direction, and the front capsule body (not shown in the figure) located in the front capsule accommodating cavity 032c and the rear capsule body (not shown in the figure) located in the rear capsule accommodating cavity 032d are used for flexible loading and force transmission in the Y direction; elastic buffer gaskets 07 and rigid pressure blocks 08 are provided at the top and bottom of each capsule body 06, and an axial rigid pressure block 09 is provided between the upper force transmission terminal 01 and the end of the sample cavity 031; and a Z-direction loading piston rod 010 is passed through the center of the lower force transmission terminal 02.

[0052] Please combine Figure 3 , Figure 4 , Figure 6 and Fig.10 As shown: the capsule body 06 described in this embodiment has an inverted skirt interface 061, and the inverted skirt interface 061 is preferably an embedded cylindrical through hole; a sealing plug 011 is interference-connected in each inverted skirt interface 061 (that is, the outer diameter of the sealing plug 011 is slightly larger than the inner diameter of the inverted skirt interface 061, so that the inverted skirt 0611 can be pre-deformed and can be wrapped on the outer circumferential surface of the sealing plug 011 with a very small force), and an injection tube 012 connected to the inner cavity of the capsule body 06 is penetrated on each sealing plug 011, and all injection tubes 012 pass through the upper force transmitting terminal 01.

[0053] Please refer to Figure 7 and Fig. 9 and Fig.10 As shown, the sealing plug 011 described in this embodiment is preferably a metal cylinder, and it is preferred that the outer peripheral surface of the sealing plug 011 is provided with one or more external convex annular bands 0111, because in this way a concave-convex joint surface can be formed between the outer peripheral surface of the sealing plug 011 and the inverted skirt 0611, which is conducive to achieving ultra-high pressure loading sealing.

[0054] Please refer to Figure 8As shown, when the pressurized liquid enters the capsule body 06 through the liquid injection tube 012, the pressure of the pressurized liquid will be applied to the inverted skirt 0611, causing the inverted skirt 0611 to be more tightly pressed against the outer peripheral surface of the sealing plug 011, thereby achieving a self-tightening seal of the capsule body 06, and the greater the pressure p inside the capsule body 06, the greater the pressure p of the inverted skirt 0611 on the outer peripheral surface of the sealing plug 011, thereby the better the sealing effect.

[0055] The force transmission surface 062 of the capsule body 06 may be a plane (eg Figure 3 , 4 , 6 and 10), which is conducive to the force transmission and loading of cubic specimens; but it can also be a curved surface to facilitate the force transmission and loading of cylindrical specimens.

[0056] Please combine again Figure 2 and Figures 11 to 14 As shown, in the present application, at least one group of centrally symmetrical cantilevers 013 (three groups are shown in the figure, but not limited to this) are fixedly provided on the outer periphery of the upper force transmission end 01 and the outer periphery of the lower force transmission end 02, and mirror symmetry is formed between the upper cantilever 013a and the lower cantilever 013b, and an axial pressure-bearing carbon fiber ring 05 is provided on each group of upper and lower cantilevers forming the mirror symmetry.

[0057] At present, the existing technology is to first assemble the upper force transmission end 01 and the lower force transmission end 02 with the cylinder 03, and then make the axial pressure-bearing carbon fiber ring 05. This assembly method has the problems of low working efficiency and inconvenient sample replacement. In order to solve this problem, the present application provides a method such as Fig.11 The axially pressure-bearing carbon fiber ring 05 shown, combined with Fig.11 and Fig.12 It can be seen that the upper and lower arc ends of the axially pressure-bearing carbon fiber ring 05 are respectively fixed in the opening of a U-shaped limit seat 014. This axially pressure-bearing carbon fiber ring 05 is obtained by winding carbon fiber on two U-shaped limit seats 014 and then thermally curing the carbon fiber with resin. Through this design, the present invention makes the axially pressure-bearing carbon fiber ring 05 an independent component, which not only improves the sample installation efficiency, but also ensures the uniformity and consistency of the axial force on the carbon fiber.

[0058] In particular, by making the distance between the bottom surface of the upper U-shaped stop seat 014a and the top surface of the lower U-shaped stop seat 014b match the distance between the top surface of the upper cantilever 013a and the bottom surface of the lower cantilever 013b, it can ensure that each axial pressure-bearing carbon fiber ring can tighten the upper and lower cantilevers, and it can also facilitate the replacement and loading and unloading of the sample. The specific implementation operation is as follows:

[0059] At the same time, the bottom surface of the upper U-shaped stopper 014a located at the upper arc end of the axial pressure-bearing carbon fiber ring 05 is separated from the top surface of the upper cantilever 013a, and the top surface of the lower U-shaped stopper 014b located at the lower arc end of the axial pressure-bearing carbon fiber ring 05 is separated from the bottom surface of the lower cantilever 013b, so that the axial pressure-bearing carbon fiber ring 05 can be easily disassembled and removed (please refer to Fig.14 As shown in the figure, when all the axial pressure-bearing carbon fiber rings 05 are disassembled and removed, the upper force-transmitting end 01 and the lower force-transmitting end 02 can be separated from the cylinder 03, thereby realizing the replacement operation of the sample in the cylinder 03;

[0060] On the contrary, the bottom surface of the upper U-shaped limit seat 014a located at the upper arc end of the axial pressure-bearing carbon fiber ring 05 is abutted against the top surface of the upper cantilever 013a, and the top surface of the lower U-shaped limit seat 014b located at the lower arc end of the axial pressure-bearing carbon fiber ring 05 is abutted against the bottom surface of the lower cantilever 013b, so that the axial pressure-bearing carbon fiber ring 05 can be installed on the upper cantilever 013a and the lower cantilever 013b (please refer to Fig.14 When all the axial pressure-bearing carbon fiber rings 05 are installed, the upper force-transmitting end 01 and the lower force-transmitting end 02 can be fixedly connected to the cylinder 03.

[0061] In order to avoid the problem that the axial pressure-bearing carbon fiber ring 05 becomes loose and slips due to deformation of the connection with the cantilever, the present application provides a detachable connection on each cantilever 013 with a limit baffle 015 that is tightly attached to the outer side of the corresponding U-shaped limit seat 014. The specific implementation method is: on each upper cantilever 013a, a detachable connection (connected by screws in this embodiment) has an upper limit baffle 015a that is tightly attached to the outer side of the upper U-shaped limit seat 014a, and on each lower cantilever 013b, a detachable connection (connected by screws in this embodiment) has a lower limit baffle 015b that is tightly attached to the outer side of the lower U-shaped limit seat 014b (please refer to Figure 2 As shown), the upper cantilever 013a and the lower cantilever 013b, the upper U-shaped limit seat 014a and the lower U-shaped limit seat 014b, the upper limit baffle 015a and the lower limit baffle 015b all form a mirror symmetric relationship; when it is necessary to remove the axial pressure-bearing carbon fiber ring 05, just loosen the fixing screws first, so that the corresponding upper and lower limit baffles 015a and 015b are rotated 180 degrees, and the blocking effect of the limit baffle on the corresponding axial pressure-bearing carbon fiber ring 05 can be cancelled (please refer to the reference numeral 014a and the reference numeral 014b for details). Figure 2 and Fig.14 shown).

[0062] Fig.15 is a structural schematic diagram of a large load true triaxial experimental device that can be combined with CT scanning provided by an embodiment of the present invention, comprising Fig.15 visible:

[0063] The present application provides a large-load true triaxial experimental device that can be combined with CT scanning, including the above-mentioned large-load core clamp 1 and Z-direction loading cylinder 2, Z-direction hydraulic loading system 3 and X-direction hydraulic loading system 4, Y-direction hydraulic loading system 5, the Z-direction loading cylinder 2 is sealedly connected to the lower force transmission end 02, a piston 21 is provided in the Z-direction loading cylinder 2, the Z-direction loading piston rod 010 is fixedly connected to the piston 21, and a hydraulic delivery channel 22 connected to the piston cavity is provided at the bottom of the Z-direction loading cylinder 2, the hydraulic delivery channel 22 is connected to the Z-direction hydraulic loading system 3 through a pressure-resistant hose, the injection pipes 012a on the two capsule bodies constituting the X-direction flexible loading are connected to the X-direction hydraulic loading system 4 through a pressure-resistant hose, and the injection pipes 012b on the two capsule bodies constituting the Y-direction flexible loading are connected to the Y-direction hydraulic loading system 5 through a pressure-resistant hose; in this embodiment, the Z-direction loading cylinder 2 is connected to the lower force transmission end 02 through a two-way nut 6.

[0064] It should be noted that, in the present application, an inward-turned skirt interface 061 is provided on each capsule body 06, and one or two liquid injection tubes 012 are passed through the sealing plug 011 in each inward-turned skirt interface 061; or two inward-turned skirt interfaces 061 are provided on each capsule body 06, and one liquid injection tube 012 is passed through the sealing plug 011 in each inward-turned skirt interface 061; when two liquid injection tubes are provided on the capsule body 06, an in-and-out circulation of the liquid in the capsule body 06 can be realized, thereby achieving the purpose of heating or cooling the sample while loading it.

[0065] Fig.16 This embodiment shows the combination of the large load true triaxial experimental device and CT scanning, namely:

[0066] When in use, the large-load true triaxial experimental device provided by the present application is placed on the CT rotating table 7, and the position of the CT ray source 8 is such that it can horizontally penetrate the barrel section 1-1 of the large-load core holder 1 to reach the CT photosensitive plate 9.

[0067] Since the barrel section 1-1 of the large-load core holder 1 provided in the present application is mainly made of non-metallic composite materials such as carbon fiber, engineering plastics and the like, and the core holder described in the present invention can realize ultra-high hydraulic loading in three axes respectively, therefore, under the condition of realizing the same hydraulic loading, the present invention can reduce the weight of the entire true triaxial test device to a few tens of times of that of the traditional true triaxial test device. For example, if the sample specification is 50*50*100mm, the weight of the true triaxial test device provided by the present invention is only 50kg; if the sample specification is 75*75*150mm, the weight of the true triaxial test device provided by the present invention is about 100kg; it can be seen that the core holder and true triaxial test device provided by the present invention have the advantages of lightweight and miniaturization, and it is easy to realize the combination of the true triaxial test device and CT scanning, and can realize 360° scanning of CT at any time or position under true triaxial stress conditions (either sample rotation or CT rotation).

[0068] In addition, since the force-bearing surface of the sample 10 may be partially uneven or cracked, the present application sets a buffer spacer 11 between the force-transmitting surface 062 of the capsule body 06 and the corresponding force-bearing surface 101 of the sample 10 (see Fig.15 and Fig.16 As shown), to avoid local damage to the capsule body due to the irregular shape or broken cracks of the local sample; the buffer spacer 11 is preferably made of non-metallic material to avoid affecting the penetration of X-rays and making it impossible to combine with CT scanning.

[0069] Finally, it is necessary to point out here that the above description is only a preferred specific implementation manner of the present invention, but the protection scope of the present invention is not limited thereto, and any changes or substitutions that can be easily thought of by any technician familiar with the technical field within the technical scope disclosed by the present invention should be covered within the protection scope of the present invention.

Claims

1. A large-load core holder capable of combining CT scanning, comprising an upper force transmitting end, a lower force transmitting end and a cylinder with both ends open and made of a non-metallic material that can be penetrated by X-rays, a circumferential pressure-bearing carbon fiber sleeve being provided in the outer circumference of the cylinder, and at least one pair of axial pressure-bearing carbon fiber rings being symmetrically provided in the outer axial direction of the cylinder; characterized in that: A sample cavity and four capsule accommodating cavities symmetrically distributed on the left, right, front and rear sides of the sample cavity are provided in the hollow cavity of the cylinder, wherein: the two capsule bodies located in the left and right capsule accommodating cavities are used for flexible loading and force transmission in the X direction, and the two capsule bodies located in the front and rear capsule accommodating cavities are used for flexible loading and force transmission in the Y direction; each capsule body is provided with an inverted skirt interface, each inverted skirt interface is interference-connected with a sealing plug, each sealing plug is provided with an injection tube connected with the upper cavity of the capsule body, and all the injection tubes are passed through the force transmission terminal; and a Z-direction loading piston rod is provided in the center of the lower force transmission terminal, elastic buffer gaskets and rigid pressure blocks are provided at the top and bottom of each capsule body, an axial rigid pressure block is provided between the force transmission terminal and the end of the sample cavity, the inverted skirt interface is an embedded cylindrical through hole, and the sealing plug is a metal cylinder.

2. The heavy-load core holder according to claim 1, characterized in that: One or more external convex annular bands are arranged on the outer peripheral surface of the sealing plug.

3. The heavy-load core holder according to claim 1, characterized in that: The force transmission surface of the capsule body is a flat surface or a curved surface.

4. The heavy-load core holder according to claim 1, characterized in that: At least one group of centrally symmetrical cantilevers are fixedly arranged on the outer peripheries of the upper force transmitting end and the lower force transmitting end, and mirror symmetry is formed between the upper cantilever and the lower cantilever. An axial pressure-bearing carbon fiber ring is arranged on each group of upper and lower cantilevers forming mirror symmetry.

5. The heavy-load core holder according to claim 4, characterized in that: The upper and lower arc ends of each axially pressure-bearing carbon fiber ring are respectively fixed in the opening of a U-shaped limit seat, and the distance between the bottom surface of the upper U-shaped limit seat and the top surface of the lower U-shaped limit seat is adapted to the distance between the top surface of the upper cantilever and the bottom surface of the lower cantilever, so as to ensure that each axially pressure-bearing carbon fiber ring can tighten the upper and lower cantilevers and can be easily loaded and unloaded.

6. The heavy-load core holder according to claim 5, characterized in that: An upper limit baffle plate is detachably connected on the upper cantilever and is closely attached to the outer side of the upper U-shaped limit seat. A lower limit baffle plate is detachably connected on the lower cantilever and is closely attached to the outer side of the lower U-shaped limit seat. The upper limit baffle plate and the lower limit baffle plate are in a mirror-symmetrical relationship.

7. A high-load true triaxial experimental device capable of combining CT scanning, characterized in that: It comprises the heavy-load core clamp and Z-direction loading cylinder, Z-direction hydraulic loading system, X-direction hydraulic loading system and Y-direction hydraulic loading system according to any one of claims 1 to 6, wherein the Z-direction loading cylinder is sealedly connected to the lower force transmission end head, a piston is arranged in the Z-direction loading cylinder, the Z-direction loading piston rod is fixedly connected to the piston, a hydraulic delivery channel connected to the piston cavity is arranged at the bottom of the Z-direction loading cylinder, the hydraulic delivery channel is connected to the Z-direction hydraulic loading system through a pressure-resistant hose, the injection pipes on the two capsule bodies used for X-direction flexible loading and force transmission in the heavy-load core clamp are connected to the X-direction hydraulic loading system through a pressure-resistant hose, and the injection pipes on the two capsule bodies used for Y-direction flexible loading and force transmission in the heavy-load core clamp are connected to the Y-direction hydraulic loading system through a pressure-resistant hose.

8. The large-load true triaxial test device according to claim 7, characterized in that: A buffer spacer is provided between the force transmission surface of the capsule body and the force bearing surface of the sample, and the buffer spacer is made of non-metallic material.

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