A true triaxial multi-size specimen test device and test method

Abstract

The present invention relates to the technical field of true triaxial testing of rock mechanics, and in particular to a true triaxial multi-size specimen test device and test method. The test device includes six pressure heads, which are respectively arranged corresponding to the six faces of a cubic specimen; a pressure block assembly for pressing against the corresponding face of the cubic specimen is arranged on each of the pressure heads; the pressure block assembly includes a first pressure block and a plurality of adjustment pressure blocks coaxially nested in the first pressure block; the pressure block assembly also includes a plurality of adjustment members arranged in each of the pressure heads; the adjustment members are arranged in a one-to-one correspondence with the adjustment pressure blocks, and are used to drive the adjustment pressure blocks to approach or move away from the first pressure block. The test method uses the test device to carry out true triaxial loading tests on multi-size specimens. The present invention can carry out true triaxial loading tests on multi-size specimens, and has strong practicality.

Description

Technical Field

[0001] The invention relates to the technical field of true triaxial testing of rock mechanics, and in particular to a testing device and a testing method for true triaxial multi-size specimens. Background Art

[0002] The experimental study on the mechanical and deformation properties of geotechnical materials is the basis for establishing the constitutive model of geotechnical materials. Geotechnical tests are also an effective means to improve the development theory and calculation methods of geotechnical materials. In particular, the study on the three-dimensional stress-deformation characteristics of geotechnical materials has guiding significance for on-site design and construction. As an indoor test equipment in the field of civil engineering, the true triaxial loading test device can truly simulate the three-dimensional stress state of geotechnical materials, that is, the stress components applied separately in three directions (i.e., x-direction, y-direction, and z-direction) of the rectangular specimen. By combining the three stress components, the relationship between principal stress and strain and the strength characteristics, i.e., the constitutive relationship of geotechnical materials, are studied. Therefore, compared with the traditional conventional triaxial test, the true triaxial test can better study the mechanical and strength characteristics of soil in a complex stress environment, and thus has a wide range of applications.

[0003] However, the existing single true triaxial apparatus can usually only perform loading tests on specimens of a single design size. If you want to study the impact of size effect on loading results, you need to conduct true triaxial tests on specimens of different sizes. At the same time, you need to replace the existing true triaxial apparatus with different models or replace the indenter with different models. When using different true triaxial apparatuses, it is difficult to eliminate the effects of instrument centering and indenter friction on specimens of different sizes.

[0004] In summary, it is necessary to provide a true triaxial multi-size specimen test device and test method to solve the problem that the existing single true triaxial instrument can only perform a single design size specimen loading test during the loading process. Summary of the invention

[0005] The purpose of the present invention is to provide a true triaxial multi-size specimen test device and test method, the specific technical scheme is as follows:

[0006] In the first aspect, the present invention provides a testing device for true triaxial multi-size specimens, wherein the specimen is a cubic specimen; the testing device includes six pressure heads and is respectively arranged corresponding to the six faces of the cubic specimen; a pressure block assembly is arranged on each of the pressure heads for pressing against the corresponding face of the cubic specimen; the pressure block assembly includes a first pressure block and a plurality of adjustment pressure blocks coaxially nested in the first pressure block; the pressure block assembly also includes a plurality of adjustment members arranged in each of the pressure heads; the adjustment members are arranged in a one-to-one correspondence with the adjustment pressure blocks, and are used to drive the adjustment pressure blocks to approach or move away from the first pressure block.

[0007] Optionally, the adjusting pressure block includes a second pressure block and a third pressure block; the first pressure block, the second pressure block and the third pressure block are coaxially nested in sequence from the outside to the inside; the adjusting member includes a first adjusting component and a second adjusting component; the first adjusting component is in contact with the second pressure block, and is used to drive the second pressure block to approach or move away from the first pressure block and the third pressure block; the second adjusting component is in contact with the third pressure block, and is used to drive the third pressure block to approach or move away from the first pressure block and the second pressure block.

[0008] Optionally, the first adjustment assembly includes a first screw and a first control dial; the first screw is arranged in the pressure head along the central axis of the pressure head; one end of the first screw close to the cubic specimen is in contact with the second pressure block; a first mounting hole for the first control dial to be installed through is arranged in the radial direction of the pressure head, one side of the first control dial is located in the pressure head and is threadedly connected to the first screw, and the other side is located outside the pressure head;

[0009] The first screw rod is in contact with the inner wall surface of the pressing head, and a thread structure matched with the first screw rod is arranged on the inner wall surface of the pressing head.

[0010] Optionally, the second adjustment assembly includes a second screw and a second control dial; the second screw is coaxially arranged in the first screw, and the length of the second screw is greater than that of the first screw; the second screw is in contact with the third pressure block at one end close to the cubic specimen; a second mounting hole for the second control dial to be installed through is provided in the radial direction of the pressure head, one side of the second control dial is located inside the pressure head and threadedly connected to the second screw, and the other side is located outside the pressure head.

[0011] Optionally, the pressure block assembly also includes a first limit block and a second limit block; the first limit block is arranged on the side of the second pressure block away from the cubic sample, and a first slot for limiting the stroke of the first limit block is provided on the inner wall of the pressure head; the second limit block is arranged on the side of the third pressure block away from the cubic sample, and a second slot for limiting the stroke of the second limit block is provided on the inner wall of the second pressure block.

[0012] Optionally, a chamfer is provided on one end of each of the indenters close to the cubic sample.

[0013] In a second aspect, the present invention provides a test method using the true triaxial multi-size specimen test device, comprising the following steps:

[0014] Step 1: Determine the size of the cubic sample and adjust the pressing block assembly to fit the cubic sample;

[0015] Specifically, if the size of the cubic sample is adapted to the first pressing block, the first adjusting assembly and the second adjusting assembly in the pressing block assembly are adjusted until the second pressing block and the third pressing block are close to the first pressing block and are flush with the first pressing block;

[0016] If the size of the cubic sample is adapted to the second pressing block, the first adjusting component and the second adjusting component in the pressing block assembly are adjusted until the second pressing block and the third pressing block are both away from and beyond the first pressing block, and the second pressing block and the third pressing block are flush;

[0017] If the size of the cubic sample is compatible with the third pressing block, adjusting the second adjusting assembly in the pressing block assembly until the third pressing block is away from and beyond the first pressing block and the second pressing block;

[0018] Step 2: First, push the pressure block assemblies on the two pressure heads corresponding to the top and bottom surfaces of the cubic sample toward the center of the top and bottom surfaces of the cubic sample respectively until they are in contact; second, push the pressure block assemblies on the four pressure heads corresponding to the four surfaces of the cubic sample located between the top and bottom surfaces toward the center of the four surfaces of the cubic sample respectively until they are in contact; finally, tighten and seal the pressure chamber;

[0019] Step 3: Push the pressure chamber into the true triaxial loading system, and connect each of the pressure heads in the pressure chamber to the oil cylinder in the true triaxial loading system;

[0020] Step 4: injecting oil into the pressure chamber through the oil cylinder, exhausting the air in the pressure chamber, adjusting the oil pressure to the expected pressure, ensuring that the confining pressure in the pressure chamber is applied to the predetermined value, so that each of the pressure heads fits tightly with the cubic sample;

[0021] Step 5: Perform three-axis loading on the cubic specimen through a true triaxial loading system to complete the loading test.

[0022] Optionally, in step one, a pressing surface formed by flushing the first pressing block, the second pressing block and the third pressing block is a square pressing surface, and a side length of the pressing surface is 0.85-0.95 times a side length of the cubic sample.

[0023] Optionally, in step one, the pressing surface formed by flushing the second pressing block and the third pressing block is a square pressing surface, and the side length of the pressing surface is 0.8-0.9 times the side length of the cubic sample.

[0024] Optionally, in step one, the pressing surface formed by the third pressing block is a square pressing surface, and the side length of the pressing surface is 0.75-0.85 times the side length of the cubic sample.

[0025] The application of the technical solution of the present invention has at least the following beneficial effects:

[0026] (1) The present invention provides a true triaxial multi-size specimen test device, which can perform true triaxial loading tests on specimens of multiple sizes by adjusting the adjusting components in the pressure block assembly to drive the adjusting pressure blocks and the adjusting pressure blocks and the first pressure blocks to form pressure surfaces of different sizes, thereby solving the problem that the existing single true triaxial instrument can only perform loading tests on specimens of a single design size during the loading process. In addition, the device is simple to operate, reusable, highly adaptable, and easy for engineering test personnel to operate.

[0027] (2) The present invention provides a test method for a true triaxial multi-size specimen test device, which can perform true triaxial loading tests on multi-size specimens. The steps are simple and easy to operate, and the method has strong practicality.

[0028] In addition to the above-described purposes, features and advantages, the present invention has other purposes, features and advantages. The present invention will be further described in detail with reference to the accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] The drawings constituting a part of this application are used to provide a further understanding of the present invention. The exemplary embodiments of the present invention and their descriptions are used to explain the present invention and do not constitute an improper limitation of the present invention. In the drawings:

[0030] Figure 1 It is a schematic diagram of the overall structure of a true triaxial multi-size specimen test device in an embodiment of the present invention;

[0031] Figure 2 yes Figure 1 Schematic diagram of the structure of a single pressure head;

[0032] Figure 3 yes Figure 1 Internal schematic diagram of the medium pressure head;

[0033] Figure 4 yes Figure 1 The middle pressure head exploded picture;

[0034] Figure 5 is a schematic diagram of the contact between the indenter and the specimen;

[0035] Figure 6 It is a cross-sectional view of the local structure of the pressure head;

[0036] Figure 7 It is a schematic diagram of the state of the three indenter ends against the 200mm specimen;

[0037] Figure 8 It is a schematic diagram of the state of the three indenter ends against the 150mm specimen;

[0038] Fig. 9 It is a schematic diagram of the state where the ends of the three indenters are against a 100 mm sample;

[0039] Among them, 1. pressure head, 1.1. first slot, 2. first pressure block, 3. second pressure block, 3.1. second slot, 4. third pressure block, 5. first adjustment component, 5.1. first screw, 5.2. first control turntable, 6. second adjustment component, 6.1. second screw, 6.2. second control turntable, 7. first limit block, 8. second limit block, A. sample. DETAILED DESCRIPTION

[0040] The following will be combined with the accompanying drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field belong to the scope of protection of the present invention.

[0041] Example:

[0042] See also Figure 1-9 , a test device for true triaxial multi-size specimens, wherein the specimen A is a cubic specimen; the test device comprises six pressure heads 1 and are respectively arranged corresponding to the six faces of the cubic specimen; a pressure block assembly for pressing against the corresponding face of the cubic specimen is arranged on each of the pressure heads 1; the pressure block assembly comprises a first pressure block 2, a second pressure block 3 and a third pressure block 4 which are coaxially nested in sequence from the outside to the inside; the pressure block assembly also comprises a first adjustment assembly 5 and a second adjustment assembly 6 which are arranged in each of the pressure heads 1; the first adjustment assembly 5 is in contact with the second pressure block 3, and is used to drive the second pressure block 3 to approach or move away from the first pressure block 2 and the third pressure block 4; the second adjustment assembly 6 is in contact with the third pressure block 4, and is used to drive the third pressure block 4 to approach or move away from the first pressure block 2 and the second pressure block 3.

[0043] See also Figure 3-4 The first adjustment component 5 includes a first screw 5.1 and a first control dial 5.2; the first screw 5.1 is arranged in the pressure head 1 along the central axis of the pressure head 1; the first screw 5.1 is in contact with the second pressure block 3 at one end close to the cubic specimen; a first mounting hole for the first control dial 5.2 to be installed through is arranged in the radial direction of the pressure head 1, one side of the first control dial 5.2 is located in the pressure head 1 and is threadedly connected to the first screw 5.1, and the other side is located outside the pressure head 1.

[0044] The first screw 5.1 contacts the inner wall surface of the ram 1, and a thread structure adapted to the first screw 5.1 is provided on the inner wall surface of the ram 1, so that the first screw 5.1 can be rotated up and down and locked along the central axis of the ram 1, thereby ensuring the overall rigidity of the ram.

[0045] See also Figure 3-4 The second adjustment assembly 6 includes a second screw 6.1 and a second control dial 6.2; the second screw 6.1 is coaxially arranged in the first screw 5.1, and the length of the second screw 6.1 is greater than that of the first screw 5.1; the second screw 6.1 is in contact with the third pressure block 4 at one end close to the cubic specimen; a second mounting hole for the second control dial 6.2 to be installed through is provided in the radial direction of the pressure head 1, one side of the second control dial 6.2 is located in the pressure head 1 and is threadedly connected to the second screw 6.1, and the other side is located outside the pressure head 1.

[0046] See also Figure 6 The pressing block assembly also includes a first limit block 7 and a second limit block 8; the first limit block 7 is arranged on the side of the second pressing block 3 away from the cubic sample, and a first card groove 1.1 for limiting the stroke of the first limit block 7 is provided on the inner wall of the pressing head 1; the second limit block 8 is arranged on the side of the third pressing block 4 away from the cubic sample, and a second card groove 3.1 for limiting the stroke of the second limit block 8 is provided on the inner wall of the second pressing block 3.

[0047] Specifically, when the first pressing block 2, the second pressing block 3 and the third pressing block 4 are flush with each other to form a pressing surface, the operator rotates the first control dial 5.2, and then sequentially links the first screw 5.1 and the second pressing block 3 until the second pressing block 3 is flush with the first pressing block 2. At this time, the first slot 1.1 away from the slot wall of the cubic sample contacts and resists the first limit block 7 on the second pressing block 3, providing a reaction force, thereby achieving the same flatness and rigidity of the second pressing block 3 as the conventional pressing head 1; the operator rotates the second control dial 6.2, and then sequentially links the second screw 6.1 and the third pressing block 4 until the third pressing block 4 is flush with the first pressing block 2. At this time, the second slot 3.1 away from the slot wall of the cubic sample contacts and resists the second limit block 8 on the third pressing block 4, providing a reaction force, thereby achieving the same flatness and rigidity of the third pressing block 4 as the conventional pressing head 1.

[0048] When the second pressing block 3 and the third pressing block 4 are flush with each other to form a pressing surface, the operator rotates the first control dial 5.2, and then sequentially links the first screw 5.1 and the second pressing block 3 until the second pressing block 3 moves away from the first pressing block 2 to the target position. At this time, one side of the first limit block 7 of the second pressing block 3 contacts and resists the slot wall of the first slot 1.1 close to the cubic sample to prevent the second pressing block 3 from falling out, while the other side contacts the first screw 5.1, and the first screw 5.1 provides a reaction force to achieve the same flatness and rigidity of the second pressing block 3 as the conventional pressing head 1; the operator rotates the second control dial 6.2, and then sequentially links the second screw 6.1 and the third pressing block 4 until the third pressing block 4 is flush with the second pressing block 3. At this time, the second screw 6.1 contacts the second limit block 8 on the third pressing block 4 to provide a reaction force, and the same flatness and rigidity of the third pressing block 4 as the conventional pressing head 1.

[0049] When the pressing surface is formed by the third pressing block 4, the operator rotates the second control dial 6.2, and then sequentially links the second screw 6.1 and the third pressing block 4 until the third pressing block 4 moves away from the first pressing block 2 and the second pressing block 3 to the target position. At this time, one side of the second limit block 8 of the third pressing block 4 contacts and abuts against the slot wall of the second slot 3.1 close to the cubic sample to prevent the third pressing block 4 from falling out, while the other side contacts the second screw 6.1, and with the help of the reaction force provided by the second screw 6.1, the third pressing block 4 achieves the same flatness and rigidity as the conventional pressing head 1.

[0050] A chamfer is provided on one end of each of the indenters 1 close to the cubic specimen, which effectively prevents collision and extrusion between mutually perpendicular indenters 1 during the test, ensures that the design pressure is effectively applied to the surface of the cubic specimen, and ensures accurate measurement by the measuring system.

[0051] A test method using the true triaxial multi-size specimen test device comprises the following steps:

[0052] Step 1: Determine the size of the cubic sample and adjust the pressing block assembly to fit the cubic sample;

[0053] For details, see Figure 7, if the size of the cubic sample (side length is 200mm) is compatible with the first pressing block 2 (the first pressing block 2 is a square hollow pressing block, the maximum side length of the first pressing block 2 is 180mm, and the second pressing block 3 is adapted to the hollow area of ​​the first pressing block 2), then adjust the first adjustment component 5 and the second adjustment component 6 in the pressing block assembly until the second pressing block 3 and the third pressing block 4 are close to the first pressing block 2 and are flush with the first pressing block 2; wherein, when adjusting the first adjustment component 5, the operator turns the first control dial 5.2, and then sequentially links the first screw 5.1 and the second pressing block 3 until the second pressing block 3 is flush with the first pressing block 2; when adjusting the second adjustment component 6, the operator turns the second control dial 6.2, and then sequentially links the second screw 6.1 and the third pressing block 4 until the third pressing block 4 is flush with the first pressing block 2;

[0054] See also Figure 8 , if the size of the cubic sample (150 mm) is compatible with the second pressing block 3 (the second pressing block 3 is a square hollow pressing block, the maximum side length of the second pressing block 3 is 130 mm, and the third pressing block 4 is adapted to the hollow area of ​​the second pressing block 3), then the first adjusting component 5 and the second adjusting component 6 in the pressing block assembly are adjusted until the second pressing block 3 and the third pressing block 4 are both far away from the first pressing block 2, and the second pressing block 3 and the third pressing block 4 are flush; wherein, when adjusting the first adjusting component 5, the operator turns the first control dial 5.2, and then sequentially links the first screw 5.1 and the second pressing block 3, until the second pressing block 3 is 225 mm away from the first pressing block; when adjusting the second adjusting component 6, the operator turns the second control dial 6.2, and then sequentially links the second screw 6.1 and the third pressing block 4, until the third pressing block 4 is 225 mm away from the first pressing block;

[0055] See also Figure 5 and Fig. 9 , if the size of the cubic sample (side length is 100mm) is compatible with the third pressing block 4 (the third pressing block 4 is a square solid pressing block with a side length of 80mm), then adjust the second adjusting component 6 in the pressing block assembly until the third pressing block 4 is away from and beyond the first pressing block 2 and the second pressing block 3; wherein, when adjusting the second adjusting component 6, the operator rotates the second control dial 6.2, and then sequentially links the second screw 6.1 and the third pressing block 4 until the third pressing block 4 is away from and beyond the first pressing block by 250mm, and away from and beyond the second pressing block by 325mm (when the second pressing block 3 is away from and beyond the first pressing block by 225mm) or 50mm (when the second pressing block 3 is flush with the first pressing block 2);

[0056] Step 2: First, push the pressure block assemblies on the two pressure heads 1 corresponding to the top and bottom surfaces of the cubic sample toward the center of the top and bottom surfaces of the cubic sample respectively until they are in contact; second, push the pressure block assemblies on the four pressure heads 1 corresponding to the four surfaces of the cubic sample located between the top and bottom surfaces toward the center of the four surfaces of the cubic sample respectively until they are in contact; finally, tighten and seal the pressure chamber;

[0057] Step 3: Push the pressure chamber into the true triaxial loading system, and connect each of the pressure heads 1 in the pressure chamber to the oil cylinder in the true triaxial loading system;

[0058] Step 4: inject oil into the pressure chamber through the oil cylinder, discharge the air in the pressure chamber, adjust the oil pressure to the expected pressure, ensure that the confining pressure in the pressure chamber is applied to the predetermined value, and make each of the pressure heads 1 fit tightly with the cubic sample;

[0059] Step 5: Perform three-axis loading on the cubic specimen through a true triaxial loading system to complete the loading test.

[0060] In step one, the pressing surface formed by the first pressing block 2, the second pressing block 3 and the third pressing block 4 when they are flush is a square pressing surface, and the side length of the pressing surface is 0.9 times the side length of the cubic sample. After the cubic sample is pressed toward the center of the pressing surface, a space is left at the boundary between the pressing block assembly and the cubic sample to avoid contact or collision between the mutually perpendicular pressing heads 1 and cause test errors.

[0061] In step one, the pressing surface formed by the second pressing block 3 and the third pressing block 4 when they are flush is a square pressing surface, and the side length of the pressing surface is 0.87 times the side length of the cubic sample. After the pressing surface is pressed against the cubic sample in the center, a space is left at the boundary between the pressing block assembly and the cubic sample to avoid contact or collision between the mutually perpendicular pressing heads 1 and cause test errors.

[0062] In step one, the pressing surface formed by the third pressing block 4 is a square pressing surface, and the side length of the pressing surface is 0.8 times the side length of the cubic sample. After the pressing surface is centered and pressed against the cubic sample, a space is left at the boundary between the pressing block assembly and the cubic sample to avoid contact or collision between the mutually perpendicular indenters 1, which may cause test errors.

[0063] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. For those skilled in the art, the present invention may have various modifications and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A true triaxial multi-size specimen testing device, characterized in that: The sample is a cubic sample; the test device comprises six pressure heads (1) and is respectively arranged corresponding to the six faces of the cubic sample; a pressure block assembly for pressing against the corresponding face of the cubic sample is arranged on each of the pressure heads (1); the pressure block assembly comprises a first pressure block (2) and a plurality of adjustment pressure blocks coaxially nested in the first pressure block (2); the pressure block assembly also comprises a plurality of adjustment members arranged in the pressure head (1); the adjustment members are arranged in a one-to-one correspondence with the adjustment pressure blocks and are used to drive the adjustment pressure blocks to approach or move away from the first pressure block (2); The plurality of regulating pressure blocks include a second pressure block (3) and a third pressure block (4); the first pressure block (2), the second pressure block (3) and the third pressure block (4) are coaxially nested in sequence from outside to inside; the regulating member includes a first regulating component (5) and a second regulating component (6); the first regulating component (5) is in contact with the second pressure block (3) and is used to drive the second pressure block (3) to move closer to or away from the first pressure block (2) and the third pressure block (4); the second regulating component (6) is in contact with the third pressure block (4) and is used to drive the third pressure block (4) to move closer to or away from the first pressure block (2) and the second pressure block (3); By adjusting the adjusting member in the pressure block assembly to drive the adjusting pressure blocks and the adjusting pressure blocks and the first pressure block (2) to form pressure surfaces of different sizes, a true triaxial loading test of samples of multiple sizes can be performed.

2. The true triaxial multi-size specimen testing device according to claim 1 is characterized in that: The first adjustment assembly (5) comprises a first screw (5.1) and a first control dial (5.2); the first screw (5.1) is arranged inside the pressure head (1) along the central axis of the pressure head (1); one end of the first screw (5.1) close to the cubic specimen is in contact with the second pressure block (3); a first mounting hole for the first control dial (5.2) to be installed through is arranged in the radial direction of the pressure head (1); one side of the first control dial (5.2) is located inside the pressure head (1) and is threadedly connected to the first screw (5.1), and the other side is located outside the pressure head (1); The first screw rod (5.1) is in contact with the inner wall surface of the pressing head (1), and a thread structure matching the first screw rod (5.1) is provided on the inner wall surface of the pressing head (1).

3. The true triaxial multi-size specimen testing device according to claim 2, characterized in that: The second adjustment assembly (6) comprises a second screw rod (6.1) and a second control dial (6.2); the second screw rod (6.1) is coaxially arranged in the first screw rod (5.1), and the length of the second screw rod (6.1) is greater than that of the first screw rod (5.1); the end of the second screw rod (6.1) close to the cubic specimen is in contact with the third pressing block (4); a second mounting hole for the second control dial (6.2) to be installed through is arranged in the radial direction of the pressing head (1), one side of the second control dial (6.2) is located inside the pressing head (1) and is threadedly connected to the second screw rod (6.1), and the other side is located outside the pressing head (1).

4. The true triaxial multi-size specimen testing device according to any one of claims 1 to 3, characterized in that: The pressing block assembly further comprises a first limit block (7) and a second limit block (8); the first limit block (7) is arranged on a side of the second pressing block (3) away from the cubic sample, and a first slot (1.1) for limiting the travel of the first limit block (7) is provided on the inner wall of the pressing head (1); the second limit block (8) is arranged on a side of the third pressing block (4) away from the cubic sample, and a second slot (3.1) for limiting the travel of the second limit block (8) is provided on the inner wall of the second pressing block (3).

5. The true triaxial multi-size specimen testing device according to claim 4, characterized in that: A chamfer is provided on one end of each of the indenters (1) close to the cubic sample.

6. A test method using the true triaxial multi-size specimen test device as claimed in claim 4, characterized in that: The following steps are involved: Step 1: Determine the size of the cubic sample and adjust the pressing block assembly to fit the cubic sample; Specifically, if the size of the cubic sample is compatible with the first pressing block (2), the first adjusting component (5) and the second adjusting component (6) in the pressing block assembly are adjusted until the second pressing block (3) and the third pressing block (4) are close to the first pressing block (2) and are flush with the first pressing block (2); If the size of the cubic sample is compatible with the second pressing block (3), the first adjusting component (5) and the second adjusting component (6) in the pressing block assembly are adjusted until the second pressing block (3) and the third pressing block (4) are both away from and beyond the first pressing block (2), and the second pressing block (3) and the third pressing block (4) are flush; If the size of the cubic sample matches the third pressing block (4), adjusting the second adjusting assembly (6) in the pressing block assembly until the third pressing block (4) is away from and beyond the first pressing block (2) and the second pressing block (3); Step 2: First, the pressing block assemblies on the two pressing heads (1) corresponding to the top and bottom surfaces of the cubic sample are respectively pushed toward the center of the top and bottom surfaces of the cubic sample until they are in contact; second, the pressing block assemblies on the four pressing heads (1) corresponding to the four surfaces of the cubic sample located between the top and bottom surfaces are respectively pushed toward the center of the four surfaces of the cubic sample until they are in contact; finally, the pressure chamber is tightly sealed; Step 3: Push the pressure chamber into the true triaxial loading system, and connect each of the pressure heads (1) in the pressure chamber to the oil cylinder in the true triaxial loading system; Step 4: injecting oil into the pressure chamber through the oil cylinder, exhausting the air in the pressure chamber, adjusting the oil pressure to the expected pressure, ensuring that the confining pressure in the pressure chamber is applied to a predetermined value, so that each of the pressure heads (1) fits tightly against the cubic sample; Step 5: Perform three-axis loading on the cubic specimen through a true triaxial loading system to complete the loading test.

7. The test method according to claim 6, characterized in that: In step one, the pressing surface formed by the first pressing block (2), the second pressing block (3) and the third pressing block (4) being flush with each other is a square pressing surface, and the side length of the pressing surface is 0.85-0.95 times the side length of the cubic sample.

8. The test method according to claim 6, characterized in that: In step one, the pressing surface formed by the second pressing block (3) and the third pressing block (4) being flush with each other is a square pressing surface, and the side length of the pressing surface is 0.8-0.9 times the side length of the cubic sample.

9. The test method according to claim 6, characterized in that: In step one, the pressing surface formed by the third pressing block (4) is a square pressing surface, and the side length of the pressing surface is 0.75-0.85 times the side length of the cubic sample.

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