A triaxial test sample preparation device for granular materials and a method for using the same

Abstract

The present invention relates to the technical field of sample preparation for testing, and discloses a sample preparation device for triaxial testing of granular materials and a method for using the same, that is, on the one hand, when the petals of the molding mold are molded together, by making the bottom of the molding mold sleeve on the top periphery of the mold base and pressing the bottom of the sample wrapping film, the structural stability of the mold during sample preparation can be improved; on the other hand, before sample preparation, the internal ventilation structure of the mold petals can be used to form a negative pressure so that the middle part of the sample wrapping film is stretched and tightly attached to the inner wall surface of the molding mold, which is convenient for laying the sample wrapping film, thereby facilitating the sample preparation efficiency and qualified rate of non-sticky cylindrical samples. In addition, since the triaxial compression test can be conveniently performed on the molded non-sticky cylindrical sample when the petals are opened, compared with the existing vacuum sample preparation method and the freezing sample preparation method, time and steps can be saved, and the efficiency of sample preparation and testing can be greatly improved.

Description

Technical Field

[0001] The invention belongs to the technical field of test sample preparation, and in particular relates to a particle material triaxial test sample preparation device and a use method thereof. Background Art

[0002] The triaxial compression test refers to a test with lateral compression and shear force. The instrument used is a triaxial shear instrument (also called a triaxial compression instrument), also referred to as a triaxial test. The core part of the triaxial shear instrument is the triaxial pressure chamber, which is equipped with an axial pressure system, a lateral pressure system, and a pore water pressure measurement system. The soil sample used in the test is cylindrical, and its height to diameter ratio is 2 to 2.5. The sample is wrapped with a thin rubber membrane to completely separate the pore water of the soil sample from the liquid (water) outside the membrane. The conventional triaxial compression test is to place the cylindrical sample in a triaxial pressure chamber filled with water or other liquid media, and the liquid pressure in the pressure chamber and the pressure and deformation at both ends of the sample are controlled by an external pressure controller. The triaxial compression test can fully reflect the entire process of the sample from stress deformation to destruction. Therefore, in the study of rock and soil mechanics, it is the most important test method for studying the deformation characteristics of rock and soil.

[0003] Due to the fragmentation of soil, soil can be regarded as a collection of granular materials. When preparing triaxial test specimens, if there are clay particles in the material, the specimen can maintain its shape through cementation force. Generally, a three-flap sample mold can be used for preparation, that is, the soil in the three-flap sample mold is compacted by a sample striker to form a cylindrical specimen; due to the presence of clay particles, after the three-flap sample mold is removed, the specimen can still maintain a cylindrical shape, and then it is wrapped with a rubber film and placed in the pressure chamber of the triaxial compression instrument for testing. When there is no clay particle in the material, the specimen cannot remain upright after the sample mold is removed, so the conventional method is no longer applicable.

[0004] For the sample preparation process of non-sticky granular materials, the existing method is generally as follows: first, tie a rubber film on the base of the testing machine (i.e., the base of the pressure chamber of the triaxial compression instrument); install a three-flap sample preparation mold, and then turn the rubber film outward on the three-flap sample preparation mold; then fill the non-sticky granular material into the mold in layers until the last layer is installed; level the surface, remove the mold clamp, add a sample cap, put the rubber film initially turned outward on the mold on the sample cap, and tie it tightly; connect the drainage (air) hole in the sample cap to the vacuum pump, then turn on the vacuum pump, and draw air from the top of the sample to form a negative pressure inside the sample, so that the non-sticky sample can stand upright under the action of negative pressure, and finally remove the three-flap sample preparation mold. In addition, there is another method of freezing the sample with a certain moisture content and the mold together in a freezer, and using the frozen moisture to generate cohesion between the particles.

[0005] However, both of the above methods have the following problems: (1) The diameter of the sample base of the triaxial testing machine is the same as the inner diameter of the three-flap sample preparation mold. Therefore, it is very unstable to place the three-flap sample preparation mold on the sample base. It often requires the assistance of assistants and the effect is poor. (2) The rubber film on the mold needs to be kept close to the mold. However, in actual operation, it is difficult to keep the rubber film close to the inside of the mold. (3) It is difficult to control the precise pressure when vacuuming the sample. That is, when the sample is large, it takes a long time to vacuumize the sample to achieve the same negative pressure. Sometimes, the sample is unstable, resulting in sample preparation failure. The overall stability and efficiency of this vacuum sampling method are poor. (4) Due to the use of the vacuum method, the sample already has an initial consolidation pressure inside. Therefore, this method cannot be used for experimental research on soil samples with low consolidation pressure or naturally deposited samples. (5) If the freezing method is used, water will expand after turning into ice, which will cause certain changes to the internal structure of the sample, thereby affecting the representativeness of the test results. At the same time, the frozen sample needs to be thawed at room temperature, and it also takes a long time to conduct formal tests, which reduces the test efficiency. Summary of the invention

[0006] In order to solve the problems of poor stability and low efficiency in the existing sample preparation process for non-sticky granular materials, the present invention aims to provide a granular material triaxial test sample preparation device and a use method thereof.

[0007] The technical solution adopted in the first aspect of the present invention is:

[0008] A sample preparation device for a triaxial test of granular materials, comprising a forming mold, a mold opening and closing switching mechanism, a sample wrapping film, a mold base, a mold top ring and a sample preparation pressure head, wherein the forming mold comprises at least two petals and can form an outer wall body for forming a cylindrical sample when the petals are closed, and the mold opening and closing switching mechanism is used to drive the forming mold to switch between opening the petals and closing the petals;

[0009] The petal body comprises an outer shell, an inner shell and a transverse support structure, wherein the outer shell is connected to the inner shell via the transverse support structure, so that the two shells are closed at the bottom, there is a gap cavity in the middle and an annular groove is formed on the top surface, a first through hole connected to the gap cavity is provided on the outer wall surface of the outer shell, and a plurality of evenly arranged second through holes connected to the gap cavity are provided on the inner wall surface of the inner shell;

[0010] When the molding mold petals are closed, the bottom of the sample wrapping film is sleeved on the top periphery of the mold base and is pressed by the molding mold sleeved on the top periphery of the mold base, the middle part of the sample wrapping film is attached to the inner wall surface of the molding mold and is used to wrap the cylindrical sample, the top of the sample wrapping film is turned outward and is pressed by the mold top ring embedded in the annular groove, the sample making press head is movably inserted into the mold top ring and is used to extrude the cylindrical sample located inside the molding mold and wrapped by the sample wrapping film.

[0011] Based on the above invention, on the one hand, when the petals of the molding mold are closed, by making the bottom of the molding mold sleeve on the top periphery of the mold base and pressing the bottom of the sample wrapping film, the structural stability of the mold during sample preparation can be improved. On the other hand, the internal ventilation structure of the mold petals can be used before sample preparation to form a negative pressure so that the middle part of the sample wrapping film is stretched and tightly attached to the inner wall surface of the molding mold, which is convenient for laying the sample wrapping film, thereby facilitating the improvement of the sample preparation efficiency and qualified rate of the non-sticky cylindrical sample. In addition, because the triaxial compression test can be conveniently performed on the molded non-sticky cylindrical sample when the petals are opened, compared with the existing vacuum sample preparation method, the vacuum time can be saved, the vacuum control difficulty can be reduced, and it is suitable for experimental research on soil samples with low consolidation pressure or naturally deposited samples, which greatly improves the efficiency of sample preparation and testing. Compared with the existing freezing sample preparation method, it can save freezing time and ensure the representativeness of the test results, and can also improve the efficiency of sample preparation and testing.

[0012] Optimally, the gap cavities of all petals are annularly connected when the petals of the molding mold are closed, and the first through hole is only provided on the outer wall surface of any one of the petals.

[0013] In a further optimization, a vertical groove is provided on the annular end surface of the outer shell;

[0014] When the petals of the molding mold are closed, two adjacent petals seal the outer side of the gap cavity through the sealing strip located in the vertical strip groove.

[0015] Optimally, a valve for opening / closing the corresponding through hole is provided in the first through hole.

[0016] Optimally, when the number of the petals is two and they are half-shaped petals, the mold opening and closing switching mechanism includes a pneumatic piston, a first rigid connecting member, a second rigid connecting member and a fixed block;

[0017] The number of the pneumatic pistons is two and they are respectively arranged vertically on the left and right sides of the petal body, wherein the fixing part of the pneumatic piston is installed on the extension bracket on the corresponding side, and the extension bracket is fixedly installed on the middle periphery of the mold base;

[0018] The number of the first rigid connectors is two and they are arranged on the left and right sides of the petal body respectively, the number of the second rigid connectors is also two and they are arranged on the left and right sides of the petal body respectively, wherein one end of the first rigid connector and one end of the second rigid connector are respectively hinged to the movable part of the pneumatic piston on the corresponding side, the other end of the first rigid connector is hinged to the top of one petal body, and the other end of the second rigid connector is hinged to the top of the other petal body;

[0019] The number of the fixing blocks is two and they are arranged on the left and right sides of the petal body respectively, wherein the fixing blocks are arranged on the extension brackets on the corresponding sides and are hinged to the bottoms of the two petals respectively.

[0020] Further optimized, a circular shaft hole is provided in the fixing block, and a transverse rotating shaft is provided on the left and right sides of the bottom of the petal body, wherein the shaft section of the transverse rotating shaft is fan-shaped and the fan-shaped angle is less than 150 degrees;

[0021] The transverse rotation axes of the two petals respectively pass through the same circular axis hole on the corresponding side.

[0022] Optimally, the sample making press head adopts a T-shaped structure, wherein the lateral portion of the sample making press head can be limited by the top of the top ring of the mold.

[0023] Optimally, it also includes a first O-ring and / or a second O-ring;

[0024] The first O-ring is used to tighten the bottom of the rubber mold sleeved on the top periphery of the mold base when the molding mold petal is opened;

[0025] The second O-ring is used to tighten the top of the rubber mold on the outer periphery of the test pressure head after the top ring of the mold is removed.

[0026] Optimally, a third through hole is provided on the bottom surface of the annular groove, which is connected to the gap cavity and can be closed by the top ring of the mold;

[0027] The triaxial test sample preparation device for granular materials also includes a pressure chamber for triaxial compression testing, wherein the pressure chamber includes a base and a surrounding tube, the base is fixedly connected to the mold base via a central column, and the bottom of the surrounding tube is detachably sealed and connected to the base, forming a pressure chamber cavity that can accommodate the molding mold, the mold opening and closing switching mechanism and the cylindrical sample.

[0028] Optimally, the enclosure includes an annular bottom plate, a top cover, a transparent cylinder and a plurality of vertically arranged reinforcing ribs;

[0029] The annular bottom plate is used to be detachably sealed and connected to the base, and the annular edge area of ​​the top cover is fixedly connected to the annular bottom plate through the reinforcing ribs;

[0030] The bottom end of the transparent cylinder is sealed and embedded in the top surface of the annular bottom plate, the top end of the transparent cylinder is sealed and embedded in the bottom surface of the top cover, and the reinforcing ribs are arranged at intervals around the transparent cylinder in an annular direction.

[0031] The technical solution adopted in the second aspect of the present invention is:

[0032] A method for using the granular material triaxial test sample preparation device according to the first aspect, comprising:

[0033] The molding die is switched to a petal-opening state through the mold opening and closing switching mechanism;

[0034] Put the bottom of the sample wrapping film onto the top periphery of the mold base;

[0035] The molding die is switched to a valve body mold closing state through the mold opening and closing switching mechanism, and the bottom of the molding die is pressed against the bottom of the sample wrapping film;

[0036] Turning the top of the sample wrapping film outward and covering the top of the forming mold;

[0037] The mold top ring is embedded in the annular groove, and the top of the sample wrapping film that is turned outward is pressed tightly;

[0038] The first through hole is opened, and air is evacuated from the gap cavity inside the valve body through the first through hole, so that the middle part of the sample wrapping film is stretched and closely attached to the inner wall surface of the molding die;

[0039] Cutting off the first through hole, weighing a target mass of sample material, and pouring the sample material into the space inside the molding die and surrounded by the sample wrapping film;

[0040] The sample preparation press is movably inserted into the top ring of the mold, and the cylindrical sample is obtained by extruding the sample preparation press;

[0041] Pull out the sample preparation pressure head, and then place a second water permeable pressure gauge on the top of the cylindrical sample;

[0042] The first through hole is opened, the top ring of the mold is removed, and then a test pressure head is placed on the second permeable stone;

[0043] The top of the sample wrapping film that has been turned inside out is restored, and a second O-ring is put on the outer circumference of the test pressure head.

[0044] Optimally, when a third through hole is provided on the bottom surface of the annular groove, and the granular material triaxial test sample preparation device further includes a pressure chamber for triaxial compression test, after resetting the top of the everted sample wrapping film and sleeved the second O-ring on the outer periphery of the test pressure head, the use method further includes:

[0045] Assembling the base and the surrounding cylinder to obtain a pressure chamber cavity capable of accommodating the forming mold, the mold opening and closing switching mechanism and the cylindrical sample;

[0046] Injecting pressurized liquid into the cavity of the pressure chamber to submerge the test pressure head and fill the cavity of the pressure chamber;

[0047] The molding mold is switched to a petal-opening state through the mold opening and closing switching mechanism so as to carry out a triaxial compression test on the cylindrical sample.

[0048] The beneficial effects of the present invention are:

[0049] (1) The present invention provides a triaxial compression test sample preparation device suitable for non-sticky granular materials and a method for using the same, that is, when the petals of the molding die are closed, the bottom of the molding die is sleeved on the top periphery of the mold base and the bottom of the sample wrapping film is pressed tightly, so that the structural stability of the mold during sample preparation can be improved; on the other hand, before sample preparation, the internal ventilation structure of the mold petals can be used to form a negative pressure so that the middle part of the sample wrapping film is stretched and tightly attached to the inner wall surface of the molding die, which is convenient for laying the sample wrapping film, thereby facilitating the sample preparation efficiency and qualified rate of non-sticky cylindrical samples;

[0050] (2) Since the triaxial compression test can be conveniently performed on the formed non-viscous cylindrical sample when the petal is open, compared with the existing vacuum sample preparation method, the vacuum time can be saved and the vacuum control difficulty can be reduced. It is also suitable for testing and studying soil samples with low consolidation pressure or naturally deposited samples, which greatly improves the efficiency of sample preparation and testing. Compared with the existing freezing sample preparation method, it can save freezing time and ensure the representativeness of the test results, which can also improve the efficiency of sample preparation and testing.

[0051] (3) Before the triaxial test begins, the cylindrical sample can always be supported by the surrounding pressure, ensuring that the test sample has a good initial state, thereby ensuring the reliability of the test results. At the same time, it can avoid the use of vacuum or freezing methods, reducing the impact on the internal structure of the sample. It is very suitable for carrying out triaxial testing on non-sticky granular materials;

[0052] (4) After the pressurized liquid is injected into the pressure chamber, the initial confining pressure of different magnitudes can be accurately controlled, so that the state of the soil under natural accumulation can be more realistically reflected, especially the soil with low consolidation pressure can be tested and analyzed (the vacuum method has a large initial consolidation force on the soil and cannot meet the test requirements for achieving low consolidation force);

[0053] (5) Since the sample making pressure head adopts a T-shaped structure and the lateral part of the sample making pressure head can be limited by the top of the top ring of the mold, when the lateral part of the sample making pressure head (i.e., the circumferential edge part) contacts the top of the top ring of the mold, it is considered that the sample has reached the target height and further extrusion is stopped, thereby accurately controlling the sample height. Especially when it is necessary to prepare a denser sample, compared with the traditional manual compaction method, it is easy to prepare a sample that meets the height requirements and has a higher density. BRIEF DESCRIPTION OF THE DRAWINGS

[0054] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0055] Figure 1 It is a schematic diagram of the internal three-dimensional structure of the granular material triaxial test sample preparation device provided by the present invention.

[0056] Figure 2 The present invention is a schematic diagram of the internal cross-sectional structure of the sample preparation device for the triaxial test of granular materials provided by the present invention.

[0057] Figure 3 It is a schematic diagram of the internal side view structure of the granular material triaxial test sample preparation device provided by the present invention.

[0058] Figure 4 It is a schematic diagram of the three-dimensional structure of the petal body in the forming mold provided by the present invention.

[0059] Figure 5 It is a schematic diagram of the top view structure of the petal body in the forming mold provided by the present invention.

[0060] Figure 6The present invention is a schematic diagram of the cross-sectional structure of a sample preparation device for a triaxial test of granular materials.

[0061] In the above drawings: 1-forming mold; 11-valve body; 111-outer shell; 112-inner shell; 113-lateral support structure; 114-gap cavity; 115-annular groove; 1161-first through hole; 1162-second through hole; 1163-third through hole; 117-vertical groove; 118-sealing strip; 119-lateral shaft; 2-mold opening and closing switching mechanism; 21-pneumatic piston; 221-rigid connector; 222-second rigid connector; 23-fixed block; 3-sample wrapping film; 4-mold base; 41-extension bracket; 5-mold top ring; 61-sample preparation pressure head; 62-test pressure head; 63-top pressure head; 71-first O-ring; 72-second O-ring; 100-cylindrical sample; 200-first permeable stone; 300-second permeable stone; 501-base; 5011-center column; 502-circumferential cylinder; 5021-annular bottom plate; 5022-top cover; 5023-transparent cylinder; 5024-reinforcement ribs. DETAILED DESCRIPTION

[0062] The present invention will be further described below in conjunction with the accompanying drawings and specific embodiments. It should be noted that although the description of these embodiments is used to help understand the present invention, it does not constitute a limitation of the present invention. The specific structures and functional details disclosed herein are only used to describe the exemplary embodiments of the present invention. However, the present invention can be embodied in many alternative forms, and it should not be understood that the present invention is limited to the embodiments set forth herein.

[0063] It should be understood that although the terms first, second, etc. may be used herein to describe various units, these units should not be limited by these terms. These terms are only used to distinguish one unit from another unit. For example, a first unit can be referred to as a second unit, and similarly, a second unit can be referred to as a first unit without departing from the scope of the exemplary embodiments of the present invention.

[0064] It should be understood that the term "and / or" that may appear in this article is merely a description of the association relationship between associated objects, indicating that three relationships may exist. For example, A and / or B can represent three situations: A exists alone, B exists alone, and A and B exist at the same time. The term " / and" that may appear in this article describes another type of association object relationship, indicating that two relationships may exist. For example, A / and B can represent two situations: A exists alone, and A and B exist alone. In addition, the character " / " that may appear in this article generally indicates that the previous and next associated objects are in an "or" relationship.

[0065] It should be understood that when an element is referred to herein as being "connected," "connected," or "coupled" to another element, it can be directly connected or coupled to the other element, or intermediate elements can exist. Conversely, when an element is referred to herein as being "directly connected" or "directly coupled" to another element, no intermediate elements are present. Additionally, other words used to describe the relationship between elements (e.g., "between" versus "directly between," "adjacent" versus "directly adjacent," etc.) should be interpreted in a similar manner.

[0066] It should be understood that the terms used herein are only used to describe specific embodiments and are not intended to limit the exemplary embodiments of the present invention. As used herein, the singular forms "a", "an", and "the" are intended to include the plural forms unless the context clearly indicates otherwise. It should also be understood that when the terms "include", "comprises", "includes", and / or "comprising" are used herein, they specify the existence of the claimed features, integers, steps, operations, units, and / or components, and do not exclude the existence or addition of one or more other features, quantities, steps, operations, units, components, and / or their combinations.

[0067] It should be understood and also noted that in some alternative embodiments, the functions / actions that appear may be different from the order in which the figures appear. For example, depending on the functions / actions involved, two figures shown in succession may actually be performed substantially concurrently, or may sometimes be performed in the reverse order.

[0068] It should be understood that in the following description, specific details are provided to facilitate a complete understanding of the example embodiments. However, it should be understood by those of ordinary skill in the art that the example embodiments can be implemented without these specific details. For example, the system can be shown in a block diagram to avoid obscuring the example with unnecessary details. In other examples, well-known processes, structures, and techniques may not be shown in unnecessary detail to avoid obscuring the example embodiments.

[0069] Embodiment 1

[0070] like Figures 1 to 6As shown, the granular material triaxial test sample preparation device provided in this embodiment includes a molding mold 1, a mold opening and closing switching mechanism 2, a sample wrapping film 3, a mold base 4, a mold top ring 5 and a sample preparation pressure head 61, wherein the molding mold 1 includes at least two petals 11 and can form an outer wall body for molding a cylindrical sample 100 when the petals are molded, and the mold opening and closing switching mechanism 2 is used to drive the molding mold 1 to switch between the opening of the petals and the closing of the petals; the petals 11 include an outer shell 111, an inner shell 112 and a transverse support structure 113, wherein the outer shell 111 and the inner shell 112 are connected at intervals by the transverse support structure 113, so that the two shells are closed at the bottom, there is a gap cavity 114 in the middle, and an annular groove 115 is formed on the top upper surface, and the outer shell 111 is provided with a plurality of grooves. A first through hole 1161 connected to the gap cavity 114 is provided on the wall surface, and a plurality of evenly arranged second through holes 1162 connected to the gap cavity 114 are provided on the inner wall surface of the inner shell 112; when the petals of the molding mold 1 are closed, the bottom of the sample wrapping film 3 is sleeved on the top periphery of the mold base 4 and is pressed by the molding mold 1 sleeved on the top periphery of the mold base 4, the middle part of the sample wrapping film 3 is attached to the inner wall surface of the molding mold 1 and is used to wrap the cylindrical sample 100, the top of the sample wrapping film 3 is turned outward and is pressed by the mold top ring 5 embedded in the annular groove 115, and the sample making press head 61 is movably inserted into the mold top ring 4 and is used to extrude the cylindrical sample 100 located inside the molding mold 1 and wrapped by the sample wrapping film 3.

[0071] like Figures 1 to 6 As shown, in the specific structure of the granular material triaxial test sample preparation device, the molding mold 1 is used to surround an outer wall body that can be used to mold the cylindrical sample 100 (generally cylindrical) when the petals are molded, and when the petals are opened, the bottom of the molding mold 1 can be released from the top periphery of the mold base 4, thereby facilitating the bottom of the sample wrapping film 3 to be put on the top periphery of the mold base 4, and facilitating the triaxial compression test of the molded cylindrical sample 100; for example, Figures 3 to 5As shown, the molding die 1 is composed of two petal bodies 11 in the shape of halves. In the petal structure of the molding die 1, since the first through hole 1161, the gap cavity 114 and the second through hole 1162 are sequentially connected, the first through hole 1161 can be used to close the gap cavity 114 and the closed gap between the inner wall surface and the sample wrapping film 3 connected through the second through hole 1162 (since the bottom of the sample wrapping film 3 is pressed by the molding die 1 on the top periphery of the mold base 4, and the top of the sample wrapping film 3 is turned outward and pressed by the mold top ring 5 embedded in the annular groove 115, the gap is The upper and lower ends are sealed respectively) to evacuate air, thereby forming a negative pressure inside the mold, so that the middle part of the sample wrapping film 3 is stretched and tightly attached to the inner wall surface of the molding mold 1, so as to prepare the qualified cylindrical sample 100; in addition, after the cylindrical sample 100 is formed, air is inflated through the first through hole 1161 to restore the normal pressure inside the mold, and then when the petal opens, it is beneficial to make the middle part of the sample wrapping film 3 separate from the inner wall surface of the molding mold 1, so as to further perform a triaxial compression test on the cylindrical sample 100 wrapped by the sample wrapping film 3.

[0072] The sample wrapping film 3 is used to wrap the sample material (such as non-sticky granular material) before molding and the cylindrical sample 100 after molding. It can be, but is not limited to, a rubber film. The mold base 4 is used to mold the bottom of the cylindrical sample 100 and to serve as a carrier of the cylindrical sample 100 during the triaxial compression test so that the test can be done directly after molding. The mold top ring 5 is used to stabilize the top film structure of the petal body 11 on the one hand to prevent the petal body from dispersing during extrusion molding and ensure successful sample preparation; on the other hand, it is used to press the top of the everted sample wrapping film 3 to prevent the sample wrapping film 3 from sliding down due to the dynamic friction generated between the sample material and the film during extrusion molding. The sample preparation press head 61 is used to mold the top of the cylindrical sample 100.

[0073] Therefore, through the detailed structural description of the aforementioned triaxial test sample preparation device for granular materials, a triaxial compression test sample preparation device suitable for non-sticky granular materials is provided, that is, on the one hand, when the petals of the molding mold are closed, by making the bottom of the molding mold cover the top periphery of the mold base and pressing the bottom of the sample wrapping film, the structural stability of the mold during sample preparation can be improved; on the other hand, before sample preparation, the internal ventilation structure of the mold petals can be used to form a negative pressure so that the middle part of the sample wrapping film is stretched and tightly attached to the inner wall surface of the molding mold, which is convenient for laying the sample wrapping film, thereby helping to improve the sample preparation efficiency and pass rate of non-sticky cylindrical samples. In addition, since the triaxial compression test can be conveniently carried out on the formed non-viscous cylindrical sample when the petals are opened, compared with the existing vacuum sample preparation method, the vacuum time can be saved and the difficulty of vacuum control can be reduced. It is also suitable for experimental research on soil samples with low consolidation pressure or naturally deposited samples, which greatly improves the efficiency of sample preparation and testing. Compared with the existing freezing sample preparation method, it can save freezing time, ensure the representativeness of the test results, and improve the efficiency of sample preparation and testing.

[0074] Optimally, the method for using the above-mentioned granular material triaxial test sample preparation device may include, but is not limited to, the following steps S101 to S111.

[0075] S101. The molding mold 1 is switched to a petal-opening state through the mold opening and closing switching mechanism 2.

[0076] S102 . Put the bottom of the sample wrapping film 3 onto the top periphery of the mold base 4 .

[0077] In step S102, since the molding mold 1 has been switched to the petal-opening state, the bottom of the molding mold 1 will be released from the top periphery of the mold base 4, and it is convenient to put the bottom of the sample wrapping film 3 on the top periphery of the mold base 4. In addition, the first permeable stone 200 and the first filter paper (not shown in the figure) need to be placed on the top surface of the mold base 4 in sequence.

[0078] S103. The molding mold 1 is switched to the valve body mold closing state through the mold opening and closing switching mechanism 2, and the bottom of the molding mold 1 is pressed against the bottom of the sample wrapping film 3.

[0079] S104 . Turn the top of the sample wrapping film 3 inside out and cover the top of the molding mold 1 .

[0080] S105. Embed the mold top ring 5 in the annular groove 115 and press the top of the everted sample wrapping film 3.

[0081] S106 . Open the first through hole 1161 , and evacuate the gap cavity 114 inside the petal body 11 through the first through hole 1161 , so that the middle part of the sample wrapping film 3 is stretched and tightly attached to the inner wall surface of the molding mold 1 .

[0082] In the step S106 , air can be pumped using, but is not limited to, an ear suction ball or an air pump connected to the first through hole 1161 .

[0083] S107 . Close the first through hole 1161 , weigh a target mass of sample material, and pour it into the space inside the molding die 1 and surrounded by the sample wrapping film 3 .

[0084] In step S107, the target mass is pre-set according to the experimental target, and the sample material may be, but is not limited to, a non-viscous granular material, such as loose soil. In addition, after the sample material is poured in, it can generally be compacted stepwise in three layers.

[0085] S108. The sample-preparing press head 61 is movably inserted into the top sleeve ring 4 of the mold, and the cylindrical sample 100 is obtained by extruding the sample-preparing press head 61 .

[0086] In the step S108, after the sample pressing head 61 is inserted, the sample pressing head 61 can be struck by a hammer or the mold base 4 can be moved upward (at this time, the sample pressing head 61 and the mold base 4 are moved upward). Figure 6 The top pressure head 63 in the middle is in contact and stationary), and pressure is applied to the pressure head to squeeze and obtain the cylindrical sample 100.

[0087] S109 . Pull out the sample preparation press head 61 , and then place the second permeable stone 300 on the top of the columnar sample 100 .

[0088] In the step S109 , it is necessary to conventionally place a second filter paper (not shown in the figure) and a second permeable stone 300 on the top surface of the columnar sample 100 in sequence.

[0089] S110 . Connect the first through hole 1161 , remove the mold top ring 5 , and then place the test pressure head 62 on the second permeable stone 300 .

[0090] In the step S110 , the test indenter 62 is a conventional test component.

[0091] S111. Reset the top of the sample wrapping film 3 that has been turned outward, and put a second O-ring 72 on the outer periphery of the test pressure head 62.

[0092] Therefore, through the use method described in detail in the aforementioned steps S101 to S111, it is possible to, but not limited to, quickly and efficiently prepare qualified cylindrical samples for triaxial compression testing for non-sticky granular materials.

[0093] Optimally, a third through hole 1163 is provided on the bottom surface of the annular groove 115, which is connected to the gap cavity 114 and can be closed by the top ring 5 of the mold; the granular material triaxial test sample preparation device also includes a pressure chamber for triaxial compression test, wherein the pressure chamber includes a base 501 and a surrounding tube 502, the base 501 is fixedly connected to the mold base 4 through a central column 5011, and the bottom of the surrounding tube 502 is detachably sealed and connected to the base 501, forming a pressure chamber cavity that can accommodate the molding mold 1, the mold opening and closing switching mechanism 2 and the cylindrical sample 100.

[0094] like Figure 5 As shown, the third through hole 1163 is used to facilitate the removal of internal air when the pressurized liquid is poured into the gap cavity 114 (through the first through hole 1161), so that the pressurized liquid (such as water) can surround the sample wrapping film 3 and the cylindrical sample 100 before the petals of the molding die 1 open, and then the liquid pressure can be used to maintain the cylindrical shape when the petals open. The pressure chamber is a triaxial pressure chamber, which, in addition to the base 501 and the surrounding tube 502, can also be conventionally configured with an axial pressure system, a lateral pressure system, and a pore water pressure measurement system, etc., in order to perform a triaxial compression test. Figure 6As shown, since the base 501 is fixedly connected to the mold base 4 through the central column 5011, the cylindrical sample 100 can be directly prepared in the pressure chamber (for the convenience of preparation, the surrounding cylinder 502 needs to be removed first), and then the surrounding cylinder 502 is assembled to obtain a closed pressure chamber, and then a pressurized liquid (such as water) is gradually injected into the pressure chamber from the bottom to the top, so that the pressurized liquid surrounds the sample wrapping film 3 and the cylindrical sample 100, and finally when the petal is opened, the pressurized liquid is used to replace the mold to maintain the stability of the cylindrical sample 100, so that the triaxial compression test of the cylindrical sample 100 can be carried out. Therefore, before the test starts, the cylindrical sample 100 can always be supported by the surrounding pressure, ensuring that the test sample has a good initial state, thereby ensuring the reliability of the test results, and at the same time avoiding the use of vacuum or freezing methods, reducing the impact on the internal structure of the sample, which is very suitable for carrying out triaxial testing work on non-sticky granular materials. In addition, after the pressurized liquid is injected into the pressure chamber, the initial confining pressure of different sizes can be accurately controlled, so that the state of the soil under natural accumulation conditions can be more realistically reflected, especially for testing and analyzing soil with low consolidation pressure (the vacuum method has a large initial consolidation force on the soil and cannot meet the testing requirements for achieving low consolidation force).

[0095] In a further optimized method, the method of using the above-mentioned granular material triaxial test sample preparation device may further include, but is not limited to, the following steps S112 to S114 after the step S111.

[0096] S112. Assemble the base 501 and the surrounding cylinder 502 to obtain a pressure chamber cavity that can accommodate the molding mold 1, the mold opening and closing switching mechanism 2 and the cylindrical sample 100.

[0097] S113. Inject pressurized liquid into the cavity of the pressure chamber to submerge the test pressure head 62 and fill the cavity of the pressure chamber.

[0098] S114. The molding mold 1 is switched to the petal-opening state through the mold opening and closing switching mechanism 2 so as to carry out a triaxial compression test on the cylindrical sample 100 .

[0099] Through the aforementioned steps S112 to S114, after the sample preparation is completed, the pressure chamber can be directly filled with water under confining pressure, and by controlling the liquid pressure in the pressure chamber, the cylindrical sample 100 is always supported by the surrounding pressure, ensuring that the test sample has a good initial state and the correctness of the triaxial compression test. In addition, compared with the traditional vacuuming or freezing method, since there is no need to spend vacuuming time, freezing time or thawing time, the efficiency of sample preparation and testing can be greatly improved.

[0100] Further optimized, the surrounding tube 502 includes an annular bottom plate 5021, a top cover 5022, a transparent cylinder 5023 and a plurality of vertically arranged reinforcing ribs 5024; the annular bottom plate 5021 is used to be detachably sealed and connected to the base 501, and the annular edge area of ​​the top cover 5022 is fixedly connected to the annular bottom plate 5021 through the reinforcing ribs 5024; the bottom end of the transparent cylinder 5023 is sealed and embedded in the top surface of the annular bottom plate 5021, and the top end of the transparent cylinder 5023 is sealed and embedded in the bottom surface of the top cover 5022, and the reinforcing ribs 5024 are arranged circumferentially around the transparent cylinder 5023 at intervals. Figure 1 and 6 As shown, the detachable connection between the annular bottom plate 5021 and the base 501 can be achieved by, but is not limited to, a bolt structure. The transparent cylinder 5023 is used as the main body of the enclosure. Its transparency can be used to facilitate test personnel to observe the opening and closing of the valve body in the room, which is beneficial for grasping the progress of the test. The reinforcing ribs 5024 are used to strengthen the overall structural stability of the enclosure 502, and because they are arranged at intervals, they will not affect the observation of internal test phenomena. Therefore, through the specific structural design of the enclosure 502, it is possible to facilitate the observation of test phenomena while ensuring convenient assembly and use. In addition, as Figure 6 As shown, a top pressure head 63 for pressing downward against the test pressure head 62 is provided on the bottom surface of the top cover 5022, and the axial pressure applied at the top can be measured by the top pressure head 63 (at this time, the base 501 can move up and down, while the top pressure head 63 does not move).

[0101] Optimally, the gap cavities 114 of all petals 11 are circumferentially connected when the petals of the molding mold 1 are molded together, and the first through hole 1161 is only provided on the outer wall surface of any one of the petals 11. Figure 3 As shown, since the gap cavity 114 is annularly connected when the petals of the molding mold 1 are closed, only one first through hole 1161 is required to achieve the purpose of internal air extraction, air filling and water filling, which can simplify the structural design of the molding mold.

[0102] Further optimized, a vertical groove 117 is provided on the annular end surface of the outer shell 111; when the petals of the molding mold 1 are closed, the two adjacent petals 11 are sealed on the outside of the gap cavity 114 by the sealing strip 118 located in the vertical groove 117. Figure 2 and 4 As shown in Figures 5 to 5, the cooperation design of the vertical groove 117 and the sealing strip 118 can ensure the sealing effect during internal air extraction, so that negative pressure can be formed.

[0103] Optimally, a valve for opening / closing the corresponding through hole is provided in the first through hole 1161. By providing the valve, it is convenient to control the opening / closing (i.e. closing) of the first through hole 1161 during use. Further optimized, the valve can be implemented by, but not limited to, a valve structure such as a manual valve, a solenoid valve, a hydraulic valve or a pneumatic valve.

[0104] Optimized, when the number of the petal bodies 11 is two and they are respectively half-shaped petal bodies, the mold opening and closing switching mechanism 2 includes a pneumatic piston 21, a first rigid connecting member 221, a second rigid connecting member 222 and a fixing block 23; the number of the pneumatic pistons 21 is two and they are respectively arranged vertically on the left and right sides of the petal body 11, wherein the fixing portion of the pneumatic piston 21 is installed on the extension bracket 41 on the corresponding side, and the extension bracket 41 is fixedly installed on the middle periphery of the mold base 4; the number of the first rigid connecting members 221 is two and they are respectively arranged on the left and right sides of the petal body 11, and the second rigid connecting member 222 is arranged on the left and right sides of the petal body 11. There are two connectors 222, which are arranged on the left and right sides of the petal body 11, respectively. One end of the first rigid connector 221 and one end of the second rigid connector 222 are respectively hinged to the movable part of the pneumatic piston 21 on the corresponding side, the other end of the first rigid connector 221 is hinged to the top of one petal body 11, and the other end of the second rigid connector 222 is hinged to the top of the other petal body 11. There are two fixing blocks 23, which are arranged on the left and right sides of the petal body 11, respectively. The fixing blocks 23 are arranged on the extension bracket 11 on the corresponding side and are respectively hinged to the bottom of the two petals 11. Figures 1 to 3 As shown, the pneumatic piston 21 is used to lift or lower the movable part under pneumatic action (need to be connected to a conventional pneumatic pressure control pipeline), which can be realized by using an existing pneumatic piston structure; the first rigid connector 221 and the second rigid connector 222 can be, but are not limited to, strip steel plates. The working principle of the mold opening and closing switching mechanism 2 can be, but is not limited to, as follows: when the movable part is lifted, since the first rigid connector 221 and the second rigid connector 222 are rigid parts, and the bottom of the petal body 11 is hinged and restricted by the fixed block 23, the top of the petal body 11 can only open to the front or rear side (the front and rear directions and the left and right directions are perpendicular to each other on the horizontal plane) until the movable part reaches the maximum stroke, and the petal body opens to the maximum; otherwise, when the movable part descends, the petal body is molded. Therefore, through the above-mentioned structural design, the purpose of switching between petal body opening and petal body mold closing for the molding mold 1 with a double petal body structure can be achieved to ensure normal use.

[0105] Further optimized, a circular shaft hole is provided in the fixing block 23, and a transverse shaft 119 is provided on the left and right sides of the bottom of the petal body 11, wherein the axial section of the transverse shaft 119 is fan-shaped and the fan-shaped angle is less than 150 degrees; the transverse shafts 119 of the two petals 11 respectively pass through the same circular shaft hole on the corresponding side. Figure 3 and 4 As shown, through the above structural design, the two petals 11 can be rotated around the same axis to open or close the mold, ensuring that the two petals are tightly connected at the circumferential end after closing the mold. In addition, since the fan angle is less than 150 degrees, the maximum opening range of the petals can be more than 60 degrees, ensuring normal use.

[0106] Optimally, the sample making press head 61 adopts a T-shaped structure, wherein the transverse portion of the sample making press head 61 can be limited by the top of the mold top ring 5. Figure 1 and 2 As shown, in the process of squeezing the sample material using the sample pressing head 61, when the lateral portion (i.e., the annular edge portion) of the sample pressing head 61 contacts the top of the mold top ring 5, it is considered that the sample has reached the target height and further squeezing is stopped, thereby accurately controlling the sample height. Especially when it is necessary to prepare a denser sample, compared with the traditional manual compaction method, a sample that meets the height requirements and has a higher density can be easily prepared.

[0107] The optimization further includes a first O-ring 71, wherein the first O-ring 71 is used to tighten the bottom of the rubber mold 6 on the top periphery of the mold base 4 when the petals of the molding mold 1 are opened.

[0108] like Figure 2 As shown, by configuring the first O-ring 71, the bottom of the rubber mold 6 sleeved on the top periphery of the mold base 4 can be tightened before and after sample preparation and during the test to ensure the correctness of the subsequent triaxial compression test.

[0109] The optimization further includes a second O-ring 72, wherein the second O-ring 72 is used to tighten the top of the rubber mold 6 on the outer periphery of the test pressure head 62 after the mold top ring 5 is removed.

[0110] like Figure 6 As shown, by configuring the second O-ring 72, the top of the rubber mold 6 which is sleeved on the outer periphery of the test pressure head 62 can be tightened after sample preparation and during the test, thereby ensuring the correctness of the subsequent triaxial compression test.

[0111] In summary, the granular material triaxial test sample preparation device and the use method thereof provided in this embodiment have the following technical effects:

[0112] (1) This embodiment provides a triaxial compression test sample preparation device suitable for non-sticky granular materials and a method for using the same, that is, on the one hand, when the petals of the molding mold are closed, by making the bottom of the molding mold sleeve on the top periphery of the mold base and pressing the bottom of the sample wrapping film, the structural stability of the mold during sample preparation can be improved; on the other hand, before sample preparation, the internal ventilation structure of the mold petals can be used to form a negative pressure so that the middle part of the sample wrapping film is stretched and tightly attached to the inner wall surface of the molding mold, which is convenient for laying the sample wrapping film, thereby facilitating the sample preparation efficiency and qualified rate of non-sticky cylindrical samples;

[0113] (2) Since the triaxial compression test can be conveniently performed on the formed non-viscous cylindrical sample when the petal is open, compared with the existing vacuum sample preparation method, the vacuum time can be saved and the vacuum control difficulty can be reduced. It is also suitable for testing and studying soil samples with low consolidation pressure or naturally deposited samples, which greatly improves the efficiency of sample preparation and testing. Compared with the existing freezing sample preparation method, it can save freezing time and ensure the representativeness of the test results, which can also improve the efficiency of sample preparation and testing.

[0114] (3) Before the test begins, the cylindrical sample can always be supported by the surrounding pressure, ensuring that the test sample has a good initial state, thereby ensuring the reliability of the test results. At the same time, it can avoid the use of vacuum or freezing methods, reducing the impact on the internal structure of the sample. It is very suitable for triaxial testing of non-sticky granular materials;

[0115] (4) After the pressurized liquid is injected into the pressure chamber, the initial confining pressure of different magnitudes can be accurately controlled, which can more realistically reflect the state of the soil under natural accumulation conditions, especially for testing and analyzing soil with low consolidation pressure (while the vacuum method has a large initial consolidation force on the soil and cannot meet the test requirements for achieving low consolidation force);

[0116] (5) Since the sample making pressure head adopts a T-shaped structure and the lateral part of the sample making pressure head can be limited by the top of the top ring of the mold, when the lateral part of the sample making pressure head (i.e., the circumferential edge part) contacts the top of the top ring of the mold, it is considered that the sample has reached the target height and further extrusion is stopped, thereby accurately controlling the sample height. Especially when it is necessary to prepare a denser sample, compared with the traditional manual compaction method, it is easy to prepare a sample that meets the height requirements and has a higher density.

[0117] The above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit them; although the present invention is described in detail with reference to the above embodiments, a person skilled in the art should understand that the technical solutions described in the above embodiments can still be modified, or some of the technical features can be replaced by equivalents. However, these modifications or replacements do not deviate the essence of the corresponding technical solutions from the spirit and scope of the technical solutions of the embodiments of the present invention.

[0118] Finally, it should be noted that the present invention is not limited to the above optional implementations, and anyone can derive other various forms of products under the enlightenment of the present invention. The above specific implementations should not be understood as limiting the scope of protection of the present invention. The scope of protection of the present invention should be based on the definition in the claims, and the description can be used to interpret the claims.

Claims

1. A triaxial test sample preparation device for granular materials, characterized in that: The invention comprises a molding die (1), a mold opening and closing switching mechanism (2), a sample wrapping film (3), a mold base (4), a mold top ring (5) and a sample making press head (61), wherein the molding die (1) comprises at least two petals (11) and can form an outer wall for molding a cylindrical sample (100) when the petals are closed, and the mold opening and closing switching mechanism (2) is used to drive the molding die (1) to switch between opening the petals and closing the petals; The petal body (11) comprises an outer shell (111), an inner shell (112) and a transverse support structure (113), wherein the outer shell (111) and the inner shell (112) are connected to each other at intervals through the transverse support structure (113), so that the two shells are closed at the bottom, there is a gap cavity (114) in the middle, and an annular groove (115) is formed on the top surface, a first through hole (1161) connected to the gap cavity (114) is provided on the outer wall surface of the outer shell (111), and a plurality of evenly arranged second through holes (1162) connected to the gap cavity (114) are provided on the inner wall surface of the inner shell (112); When the petals of the molding die (1) are closed, the bottom of the sample wrapping film (3) is sleeved on the top periphery of the mold base (4) and is pressed by the molding die (1) sleeved on the top periphery of the mold base (4); the middle of the sample wrapping film (3) is attached to the inner wall surface of the molding die (1) and is used to wrap the cylindrical sample (100); the top of the sample wrapping film (3) is turned outward and is pressed by the mold top ring (5) embedded in the annular groove (115); the sample preparation press (61) is movably inserted into the mold top ring (5) and is used to extrude the cylindrical sample (100) located inside the molding die (1) and wrapped by the sample wrapping film (3); When the number of the petal bodies (11) is two and they are respectively half-shaped petal bodies, the mold opening and closing switching mechanism (2) includes a pneumatic piston (21), a first rigid connecting member (221), a second rigid connecting member (222) and a fixing block (23); the number of the pneumatic pistons (21) is two and they are respectively arranged vertically on the left and right sides of the petal body (11), wherein the fixing portion of the pneumatic piston (21) is mounted on the extension bracket (41) on the corresponding side, and the extension bracket (41) is fixedly mounted on the middle periphery of the mold base (4); the number of the first rigid connecting members (221) is two and they are respectively arranged on the left and right sides of the petal body (11), and the second rigid connecting member (222) is arranged on the left and right sides of the petal body (11). The number of the connecting pieces (222) is also two and they are arranged on the left and right sides of the petal body (11), respectively, wherein one end of the first rigid connecting piece (221) and one end of the second rigid connecting piece (222) are respectively hinged to the movable part of the pneumatic piston (21) on the corresponding side, the other end of the first rigid connecting piece (221) is hinged to the top of one petal body (11), and the other end of the second rigid connecting piece (222) is hinged to the top of the other petal body (11); the number of the fixing blocks (23) is two and they are respectively arranged on the left and right sides of the petal body (11), wherein the fixing blocks (23) are arranged on the extension bracket on the corresponding side and are respectively hinged to the bottom of the two petals (11); The sample making press head (61) adopts a T-shaped structure, wherein the transverse portion of the sample making press head (61) can be limited by the top of the mold top ring (5).

2. The triaxial test sample preparation device for granular materials according to claim 1, characterized in that: The gap cavities (114) of all the petals (11) are annularly connected when the petals of the molding mold (1) are molded together, and the first through hole (1161) is only provided on the outer wall surface of any one of the petals (11).

3. The triaxial test sample preparation device for granular materials according to claim 2, characterized in that: A vertical groove (117) is provided on the annular end surface of the outer shell (111); When the petals of the molding mold (1) are closed, two adjacent petals (11) seal the outer side of the gap cavity (114) via the sealing strip (118) located in the vertical strip groove (117).

4. The triaxial test sample preparation device for granular materials according to claim 1, characterized in that: Also includes a first O-ring (71) and / or a second O-ring (72); The first O-ring (71) is used to tighten the bottom of the rubber mold (6) sleeved on the top periphery of the mold base (4) when the petal body of the molding mold (1) is opened; The second O-ring (72) is used to tighten the top of the rubber mold (6) which is sleeved on the outer periphery of the test pressure head (62) after the mold top ring (5) is removed.

5. The triaxial test sample preparation device for granular materials according to claim 1, characterized in that: A third through hole (1163) is provided on the bottom surface of the annular groove (115) and is connected to the gap cavity (114) and can be closed by the mold top ring (5); The granular material triaxial test sample preparation device also includes a pressure chamber for triaxial compression testing, wherein the pressure chamber includes a base (501) and a surrounding tube (502), the base (501) is fixedly connected to the mold base (4) via a central column (5011), and the bottom of the surrounding tube (502) is detachably sealed and connected to the base (501), forming a pressure chamber cavity that can accommodate the molding mold (1), the mold opening and closing switching mechanism (2) and the columnar sample (100).

6. The triaxial test sample preparation device for granular materials according to claim 5, characterized in that: The surrounding cylinder (502) includes an annular bottom plate (5021), a top cover (5022), a transparent cylinder (5023) and a plurality of vertically arranged reinforcing ribs (5024); The annular bottom plate (5021) is used to be detachably sealed and connected to the base (501), and the annular edge area of ​​the top cover (5022) is fixedly connected to the annular bottom plate (5021) via the reinforcing ribs (5024); The bottom end of the transparent cylinder (5023) is sealed and embedded in the top surface of the annular bottom plate (5021), the top end of the transparent cylinder (5023) is sealed and embedded in the bottom surface of the top cover (5022), and the reinforcing ribs (5024) are arranged at intervals around the transparent cylinder (5023) in a circular direction.

7. A method for using the triaxial test sample preparation device for granular materials according to any one of claims 1 to 6, characterized in that: include: The molding mold (1) is switched to a valve body open state by means of the mold opening and closing switching mechanism (2); Putting the bottom of the sample wrapping film (3) onto the top periphery of the mold base (4); The molding die (1) is switched to a valve body mold closing state through the mold opening and closing switching mechanism (2), and the bottom of the molding die (1) is pressed against the bottom of the sample wrapping film (3); Turning the top of the sample wrapping film (3) outward and covering the top of the molding die (1); The mold top ring (5) is embedded in the annular groove (115) and the top of the sample wrapping film (3) which is turned outward is pressed tightly; The first through hole (1161) is connected, and air is evacuated from the gap cavity (114) inside the petal body (11) through the first through hole (1161), so that the middle part of the sample wrapping film (3) is stretched and tightly attached to the inner wall surface of the molding die (1); Cutting off the first through hole (1161), weighing a target mass of sample material, and pouring it into a space located inside the molding die (1) and surrounded by the sample wrapping film (3); The sample preparation press (61) is movably inserted into the top sleeve ring (4) of the mold, and the columnar sample (100) is obtained by extruding the sample preparation press (61); Pull out the sample preparation pressure head (61), and then place the second permeable stone (300) on the top of the columnar sample (100); The first through hole (1161) is opened, and the top ring (5) of the mold is removed, and then a test pressure head (62) is placed above the second permeable stone (300); The top of the sample wrapping film (3) that has been turned outward is restored, and a second O-ring (72) is sleeved on the outer circumference of the test pressure head (62).

8. The method for using the triaxial test sample preparation device for granular materials as claimed in claim 7, characterized in that: When a third through hole (1163) is provided on the bottom surface of the annular groove (115), and the granular material triaxial test sample preparation device further comprises a pressure chamber for triaxial compression test, after the top of the everted sample wrapping film (3) is reset and a second O-ring (72) is sleeved on the outer periphery of the test pressure head (62), the method of use further comprises: Assembling the base (501) and the surrounding cylinder (502) to obtain a pressure chamber cavity capable of accommodating the molding die (1), the die opening and closing switching mechanism (2) and the columnar sample (100); Injecting pressurized liquid into the cavity of the pressure chamber to submerge the test pressure head (62) and fill the cavity of the pressure chamber; The molding die (1) is switched to a petal-opening state by means of the mold opening and closing switching mechanism (2) so as to carry out a triaxial compression test on the columnar sample (100).

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