CN215492739U

CN215492739U - Annular compaction device for preparing hollow cylindrical sample

Info

Publication number: CN215492739U
Application number: CN202121682138.6U
Authority: CN
Inventors: 滕越; 扈萍; 马少坤; 刘莹; 张西文; 何本富; 雍浩然
Original assignee: University of Jinan
Current assignee: University of Jinan
Priority date: 2021-07-22
Filing date: 2021-07-22
Publication date: 2022-01-11
Anticipated expiration: 2031-07-22

Abstract

A solid base module is arranged at the top of the inner side of a chassis, the bottom ends of inner four-petal modules are sequentially inserted into inner four-petal placing holes of the solid base module, and the top ends of the inner four-petal modules are provided with a central positioning module; the bottom ends of the outer three-valve module are sequentially inserted into the outer three-valve placing grooves of the compaction base module; the outer hoop is sleeved on the outer side of the middle part of the outer three-valve module; a hollow cylindrical soil sample is placed in a soil sample groove formed by the inner four-valve module and the outer three-valve module; the drop hammer module is arranged at the bottom of the positioning compaction measuring module, and the top of the positioning compaction measuring module is connected with the central positioning module. The method has the characteristics of simple principle, easy operation, quick sample preparation, standard sample forming, accurate water content, uniform compactness, small demoulding disturbance, material saving and the like, and is also suitable for preparing the unsaturated hollow cylindrical sample.

Description

Annular compaction device for preparing hollow cylindrical sample

Technical Field

The utility model relates to the technical field of preparation of hollow cylindrical samples, in particular to an annular compaction device for preparing a hollow cylindrical sample.

Background

With the continuous advance of urbanization, the geotechnical underground engineering design is changed from soil destruction control to soil deformation control, and a mechanical test which is more in line with an actual stress path is a key task of soil mechanics research at the present stage.

The hollow cylindrical torsional shear apparatus is one of the most advanced geotechnical apparatuses, and is an important means for exploring the mechanical properties of soil under a complex stress path containing main stress axis deflection. However, the large height and thin sidewall of the hollow cylindrical sample bring great difficulty to the sample preparation work.

The compaction method is simple to operate and rapid in sample preparation, and is one of the most widely used preparation methods for remolded soil samples at present. When a remolded hollow cylinder sample is prepared by this method, a cylindrical soil sample (diameter: 100 mm. times. height: 200mm) is usually punched out, and an inner hole is cut out by a cutter to obtain a standard hollow cylinder sample (inner diameter: 60 mm. times. outer diameter: 100 mm. times. height: 200 mm).

However, the following problems are found in the actual operation process:

the problem (1) in the drilling process, the end part can generate obvious soil squeezing effect, soil is squeezed out, the height of the soil at the end part is increased, and the soil structures at the inner and outer diameter edges of the end part are damaged;

the problem (2) that after the cutter head enters the soil body to a certain depth, the verticality of the drilled hole is difficult to guarantee, and the wall thickness of the hollow cylindrical sample is easy to be uneven;

the compactness of the top end and the inner wall of the sample after cutting is increased to different degrees compared with other parts, and particularly for unsaturated soil which is not subjected to a subsequent saturation step and has strictly controlled water content, the problem can generate non-negligible influence on a subsequent test;

problem (4) if the soil sample is compacted and the water content is not high or the particle size of the soil particles is large, irreparable pits are formed on the inner diameter wall in the drilling process, the latex film can be embedded into the holes to form pitted surfaces under the internal pressure in the test, the measurement of the test data is inaccurate, and the risk of breaking the latex film is increased.

Problem (5) the existence of water in the soil sample, the soil squeezing effect produced by the drilling make the sample and the retaining wall closely attached, and the sample side wall after the drilling is completed is very thin (the thickness is 20mm), in the process of detaching the retaining wall, the retaining wall is difficult to separate from the soil sample, so that the cracking of the soil sample side wall in different degrees is easily caused, and finally the sample preparation failure is caused.

In order to solve the problems, an annular compaction device for preparing a hollow cylindrical sample is provided.

SUMMERY OF THE UTILITY MODEL

In order to solve the problems in the prior art, the utility model provides an annular compaction device for preparing a hollow cylindrical sample.

The technical scheme adopted by the utility model for solving the technical problems is as follows:

an annular compaction device for preparing a hollow cylindrical sample comprises a chassis 8, a compaction base module 1, an inner four-valve module 2, a central positioning module 4, a drop hammer module 6, a positioning compaction measuring module 7 and an outer three-valve module 15.

The whole concave type disc type structure that is of chassis 8, the inboard top of chassis 8 is provided with hits real base module 1, and vaseline is evenly paintd to the outer wall of interior four lamella modules 2, and the bottom of interior four lamella modules 2 inserts in proper order and hits the interior four lamella placing hole 102 of real base module 1, and central location module 4 is installed on the top of interior four lamella modules 2.

Vaseline is evenly smeared on the whole inner wall and the bottom of the outer wall of the outer three-petal module 15, and the bottom end of the outer three-petal module 15 is sequentially inserted into the outer three-petal placing groove 103 of the compaction base module 1.

The outer hoop 14 is sleeved outside the middle part of the outer three-valve module 15, and the outer three-valve module 15 is fixed into a cylindrical whole.

A hollow cylindrical soil sample 3 is placed in a soil sample groove formed by the inner four-valve module 2 and the outer three-valve module 15; the top of hollow cylinder soil sample 3 is provided with drop hammer module 6, and drop hammer module 6 installs in the bottom of location hit real measuring module 7, and the top of location hit real measuring module 7 is connected with central locating module 4.

Preferably, the compaction base module 1 comprises a compaction base 101, an inner four-valve placing hole 102, an outer three-valve placing groove 103 and a rubber inner membrane plug 104; wherein the inner four-valve module 2 is inserted into the inner four-valve placing hole 102 in sequence, the rubber inner membrane plug 104 is installed in the inner membrane hole formed by the inner four-valve module 2, and the outer three-valve module 15 is inserted into the outer three-valve placing groove 103 in sequence.

Preferably, the inner four-valve module 2 comprises an inner four-valve A201, an inner four-valve B202, an inner four-valve C203 and an inner four-valve D204; the inner four-flap A201 and the inner four-flap B202 are the same in shape, and the cross section of the inner four-flap C203 is in a 120-degree annular shape; the cross section of the inner four-petal D204 is trapezoidal.

Preferably, the center positioning module 4 comprises a center positioning rod base 401, a center positioning rod extension 402, a center positioning rod 403 and a leveling bubble 404; the central positioning rod base 401 comprises four-petal clamping grooves 405 and base connecting bolts 406; a circle of concave four-petal clamping grooves 405 are formed in the outer side of the bottom of the central positioning rod base 401, and proper vaseline is smeared on the inner side walls of the four-petal clamping grooves 405; the top of the center positioning rod base 401 is connected with a center positioning rod extension section 402 through a base connecting bolt 406, the top of the center positioning rod extension section 402 is connected with a center positioning rod 403 through a thread, and the top of the center positioning rod 403 is further provided with a leveling bubble 404.

Preferably, the drop hammer module 6 comprises a drop hammer rod 601 and an annular drop hammer 5; the annular drop hammer 5 comprises an annular drop hammer body 501, a drop hammer rod connecting screw hole 502 and a compaction rod hole 503; the whole annular drop hammer 5 is sleeved on the drop hammer rod 601 through the drop hammer rod connecting screw hole 502, and the compaction rod hole 503 is sleeved on the compaction rod 702 of the positioning compaction measuring module 7.

Preferably, the positioning compaction measuring module 7 comprises an annular compaction chassis 701, a compaction rod 702, a connecting bolt 703, a center locator 704, a center positioning hole 705 and a scale mark 706; the whole annular compaction chassis 701 is annular, a compaction rod 702 is arranged at the upper part of the annular compaction chassis 701, the top of the compaction rod 702 is connected with a central locator 704 through a connecting bolt 703, and the middle part of the central locator 704 is provided with a central positioning hole 705; the periphery of the impact beam 702 is also provided with graduation marks 706.

Preferably, the annular compaction device also comprises an outer cylinder extension section 13, a top disc 10, a support rod 9 and an adjusting bolt 12; the outer cylinder extension section 13 is installed at the top of the outer three-valve module 15, the top plate 10 is sleeved outside the joint of the outer cylinder extension section 13 and the outer three-valve module 15, the supporting rod 9 penetrates through a through hole reserved in the top plate 10 and is spirally installed in a threaded hole reserved in the base plate 8, and the top of the supporting rod 9 is provided with an adjusting bolt 12.

Preferably, the annular compaction device further comprises a sample removing gasket assembly 11, wherein the sample removing gasket assembly 11 comprises a bottom sample removing gasket 1101 and a top sample removing gasket 1102, and the bottom sample removing gasket 1101 is in the shape of a two-semicircular ring; the top knock-out washer 1102 is a full circular ring.

Compared with the prior art, the utility model utilizes the inner wall and the outer wall to form a soil sample groove with standard size, and is matched with the drop hammer module 6 to finish compaction of the hollow cylindrical soil sample; the compaction rod 702 combines the measuring height with the function of calibrating compaction, thereby not only ensuring that the compaction work is consumed as little as possible, but also solving the problem that the compaction height is inconvenient to measure due to the narrow and deep soil sample groove; the central positioning module 4 can help to correct the inner membrane more timely and accurately; the contact path of the valve and the soil body in the process is greatly shortened by inversion and demoulding; the bottom surface sample removing gasket 1101 and the top surface sample removing gasket 1102 effectively protect the inner edge and the outer edge of the end surface of the hollow cylindrical sample, and the possibility of soil body crushing is reduced; the special design of the inner four-valve module 2 can effectively reduce the squeezing force between the valves caused by small radius and thick inner wall on the premise of ensuring the formation of the specified inner diameter, and has the sample preparation accuracy and the disassembly convenience. The method has the characteristics of simple principle, easy operation, quick sample preparation, standard sample forming, accurate water content, uniform compactness, small demoulding disturbance, material saving and the like, and is also suitable for preparing the unsaturated hollow cylindrical sample. Specifically, its advantage lies in:

the method has the advantages that: the rubber inner membrane plugs 104 and the inner four-valve holes of the compaction base 101 act together to complete the fixation of the lower parts of the inner four-valve modules 2; the upper fixing of the inner four-valve module 2 is completed by using a central positioning rod base 401; the upper part and the lower part act simultaneously, so that the problem that the inner four-valve module 2 moves inwards and outwards possibly caused by the larger height of the inner membrane or the soil squeezing effect can be well solved, and the accuracy of the inner diameter size is ensured;

the method has the advantages that: the inner four-valve module 2 consists of a three-valve large membrane and a one-valve small membrane. Because the inner wall is integrally higher, the wall thickness is not suitable to be too small in order to ensure that the four valve modules 2 are integrally vertical after splicing. Under the conditions of small inner diameter and thick inner wall, if the traditional inner and outer concentric angle division mode is adopted, large extrusion force can be generated between films, and later demolding is not easy to occur; the squeezing force between membranes can be effectively reduced by reducing the number of inner membrane flaps, but the contact path with soil during demoulding can be lengthened, and the disturbance of the soil body is increased. The synergistic effect of the two effects is considered, and the special design of the inner four-petal module 2 is adopted, so that the contact path between the demoulding and the soil body is shortened while the squeezing force between the membranes is effectively reduced;

the method has the advantages that: compared with the traditional visual observation method, the leveling bubble 404 at the upper part of the central positioning rod 403 can be used for correcting the micro inclination of the inner membrane and the compaction device in the sample preparation process more timely and accurately; the central positioning rod 403 is connected by bolts and screw holes, so that the installation is convenient, the length of the central positioning rod 403 can be prolonged or shortened according to actual needs, and certain flexibility is realized;

the advantages are that: the positioning compaction measurement module 7 cooperates with the central positioning rod 403 through the central positioning hole 705, so that the level of the chassis 8 and the vertical of the whole module are ensured; thus, the annular drop weight 5 falls along the compaction shaft 702, and it is possible to ensure that the compaction work is lost as little as possible. The compaction rod 702 is marked with scales, so that the problem that the compaction height is inconvenient to measure due to the fact that the soil sample groove is deep and narrow is solved. Meanwhile, the split design of the positioning compaction measuring module 7 enables a user to replace the annular drop hammer 5 with a suitable weight according to actual requirements, so as to achieve an ideal compaction effect;

the advantages are that: the method of inverted demoulding can lead the valve to obtain the shortest soil contact path and fully utilize the weight advantage of the lower part of the valve;

the method has the advantages that: the bottom surface sample removing gasket 1101 and the top surface sample removing gasket 1102 effectively protect the inner edge and the outer edge of the end surface of the hollow cylindrical sample, reduce the possibility of soil body crushing and ensure the integrity of the inner diameter and the outer diameter of the end part of the sample;

additional aspects and advantages of the utility model will be set forth in part in the description which follows and, in part, will be obvious from the description, or may be learned by practice of the utility model.

Drawings

In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the embodiments or the prior art will be briefly described below, it is obvious that the drawings in the following description are only some embodiments of the present invention, and for those skilled in the art, other drawings can be obtained according to the drawings without creative efforts.

Fig. 1-3 are schematic structural views of a compaction base module 1 according to the present invention;

FIG. 4 is a schematic structural diagram of an inner four-valve module 2 according to the present invention;

FIG. 5 is a schematic structural view of the outer three-valve module 15 of the present invention;

FIG. 6 is a schematic structural diagram of the centering module 4 according to the present invention;

fig. 7 is a schematic structural view of the drop hammer module 6 of the present invention;

fig. 8 is a schematic view of a structural annular drop hammer 5 of the present invention;

FIG. 9 is a schematic structural diagram of a positioning compaction measurement module 7 according to the present invention;

FIG. 10 is a schematic view of a bottom knock-out washer 1101 of the present invention;

FIG. 11 is a schematic view of a top knock-out washer 1102 in accordance with the present invention;

FIG. 12 is a schematic view of the overall structure of the annular compaction device of the present invention;

FIG. 13 is a schematic view of the overall structure of the annular compaction device of the present invention;

FIG. 14 is a schematic view of the disassembled structure of the annular compaction device of the present invention.

Description of reference numerals: the device comprises a compaction base module 1, an inner four-petal module 2, a hollow cylindrical soil sample 3, a central positioning module 4, an annular drop hammer 5, a drop hammer module 6, a positioning compaction measuring module 7, a chassis 8, a support rod 9, a top plate 10, a sample disassembling gasket assembly 11, an adjusting bolt 12, an outer cylinder extension section 13, an outer hoop 14, an outer three-petal module 15 and a sample disassembling platform 16.

Detailed Description

Exemplary embodiments of the present disclosure will be described in more detail below with reference to the accompanying drawings, in order that the present disclosure may be more fully understood and fully conveyed to those skilled in the art. While the exemplary embodiments of the present disclosure are shown in the drawings, it should be understood that the utility model is not limited to the embodiments set forth herein.

The installation method of the annular compaction device comprises the following steps:

1-1. vaseline is uniformly coated on the outer wall of the inner four-valve module 2, and the inner four-valve A201, the inner four-valve B202, the inner four-valve C203 and the inner four-valve D204 are sequentially inserted into the inner four-valve placing hole 102 of the compacting chassis 101;

1-2, plugging the upper part of the rubber inner membrane plug 104 into an inner membrane hole formed by the inner four-valve module 2, and checking the joint degree and the integral flatness of the bottom of the rubber inner membrane plug 104 and the compaction base 101 to complete the lower part positioning of the inner four-valve module 2;

1-3, placing the compaction base 101 on the chassis 8;

1-4, smearing a proper amount of vaseline on the four-valve clamping groove 405 of the central positioning rod base 401, installing the vaseline on the top of the inner four-valve module 2, and completing the upper fixing of the inner four-valve module 2;

1-5, the center positioning rod base 401, the center positioning rod extension section 402 and the center positioning rod 403 are sequentially connected from bottom to top through the reserved connecting bolts and screw holes, and therefore the assembly of the center positioning module 4 is completed. Wherein, the number of the central positioning rod extension sections 402 can be increased or decreased according to the actual situation; finely adjusting the positions of the four inner valve modules 2 until the leveling bubble 404 at the top of the central positioning rod 403 is in the central position;

1-6, sequentially inserting the outer three-petal module 15 with the inner wall coated with vaseline into an outer three-petal placing groove 103 of a compacting base 101, sleeving an outer hoop 14, installing a top disc 10, and screwing an adjusting bolt 12 on the upper part of a support rod 9 after checking the integral flatness;

1-7, selecting an annular drop hammer 5 with proper weight, connecting the drop hammer with a screw hole 502 through a drop hammer rod, and assembling the drop hammer with the drop hammer rod 601 to form a drop hammer module 6;

1-8, sleeving a drop hammer module 6 into a compaction rod 702 through a compaction rod hole 503, placing an annular drop hammer 5 on an annular compaction chassis 701, and connecting a central locator 704 with the compaction rod 702 through a connecting bolt 703 to form a positioning compaction measurement module 7;

1-9, a central positioning hole 705 at the upper part of the positioning compaction measuring module 7 passes through the central positioning rod 403, and the annular compaction base plate 701 is placed in a soil sample groove formed by an inner membrane and an outer membrane, and during operation, attention should be paid to ensure that the whole positioning compaction measuring module 7 is vertical so as to reduce the collision between the positioning compaction measuring module 7 and other parts.

Secondly, a soil sample preparation method of the annular compaction device comprises the following steps:

2-1, according to actual sample preparation requirements, matching the soil sample to a target water content, and determining compaction height of each layer and required soil sample quality through a pre-compaction test;

2-2. the soil sample groove formed by the inner film and the outer film has the characteristics of depth and narrowness, and vaseline is smeared on both sides of the soil sample groove, if the soil sample is directly poured into the soil sample groove, the soil body is easy to stick to the wall in the falling process, so that the falling of the compaction device is influenced; for the above reasons, the paper tube is selected as a tool for filling soil. The specific method comprises the following steps: rolling the oil paper into a cylinder with proper thickness, extending the oil paper into the soil sample groove to enable the opening of the cylinder to be as low as possible, filling the soil sample into the oil paper cylinder, moving the oil paper cylinder along the soil sample groove, uniformly spreading the soil sample into the soil sample groove, and further flattening by using a glass rod;

2-3, the compaction operation method comprises the following steps:

(1) before the first layer is formally compacted, compacting of the preparation layer is carried out, the thickness of the preparation layer meets the requirement of galling, and the purpose of the step is to increase the flatness of the bottom of the sample to obtain a better interlayer connection effect;

(2) before the annular drop hammer 5 falls, whether the annular drop hammer 5 is horizontal or not is checked by using the leveling bubble 404 of the upper central rod to ensure that the striking rod 702 is vertical, so that the annular drop hammer 5 is ensured to fall vertically;

(3) reading the height of the soil sample after each layer is compacted, and then napping by using a napping hook; the edge galling degree is properly larger than that of the central part so as to avoid layering of the soil sample; during reading, keeping the sight line horizontal to the upper edge of the top plate, reading the scale number of the tamping rod 702, and taking the difference between the front and the rear of tamping as the actual tamping height;

(4) when the last layer or two layers of soil samples are compacted, the outer cylinder extension section 13 can be installed for auxiliary compaction, and at the moment, the scales on the compaction rod 702 are read firstly and then compacted; during reading, the sight line should be kept horizontal with the upper edge of the outer cylinder extension section 13, and the scale number on the tamping bar 702 is read.

Thirdly, the disassembly method of the annular compaction device comprises the following steps:

3-1, after compaction, taking down the outer cylinder extension section 13, and taking out the positioning compaction measuring module 7 along the central positioning module 4;

3-2, sequentially disassembling the central positioning rod extension section 402, the top disc 10, the bottom disc 8 and the compaction base 101;

3-3, placing a top surface sample removing gasket 1102 on the top of the hollow cylindrical soil sample, taking off the outer hoop 14, inverting the whole device on a sample removing table 16, and installing a bottom surface sample removing gasket 1101 between the bottom of the hollow cylindrical soil sample and the rubber inner membrane plug 104;

3-3, sequentially disassembling the outer three-valve module 15, and specifically: vertically knocking the upper edge of the outer three-petal module 15 by using a small steel hammer, and downwards sliding and detaching the outer three-petal module, wherein the soil body is kept horizontal in the process;

3-4, the film bearing cylinder used in the test can be sleeved on the outer wall of the sample to protect the sample; if the prepared soil sample is unsaturated soil which does not need to be saturated, the film bearing cylinder sleeved with the latex film can be directly sleeved on the outer wall of the sample for protection;

3-5, taking down the bottom center positioning rod base 401, and in the process, paying attention to the fact that the prizing seam is symmetrical; taking off the rubber inner membrane plug;

3-6, vertically tapping the inner four-valve module 2204, and taking out the inner four-valve module inwards and downwards after the inner four-valve module is loosened; according to the method, the remaining inner four-valve modules 2 are sequentially taken down, the bottom sample removing gasket 1101 is not easily extruded in the operation process, and the horizontal and no movement is kept;

3-7. at this time, the sample removal was completed to prepare a hollow cylindrical sample 3 having a standard size (inner diameter 60 mm. times. outer diameter 100 mm. times. height 200 mm).

In order to make the objects, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention are clearly and completely described above with reference to the drawings in the embodiments of the present invention, and it is obvious that the described embodiments are a part of the embodiments of the present invention, but not all of the embodiments. The components of embodiments of the present invention generally described and illustrated in the figures herein may be arranged and designed in a wide variety of different configurations.

Thus, the above detailed description of the embodiments of the utility model presented in the drawings is not intended to limit the scope of the utility model as claimed, but is merely representative of selected embodiments of the utility model. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.

Claims

1. An annular compaction device for preparing a hollow cylindrical sample is characterized in that: the device comprises a chassis (8), a compaction base module (1), an inner four-valve module (2), a central positioning module (4), a drop hammer module (6), a positioning compaction measuring module (7) and an outer three-valve module (15);

the chassis (8) is integrally of a concave disc type structure, the top of the inner side of the chassis (8) is provided with a compacting base module (1), vaseline is uniformly coated on the outer wall of the inner four-petal module (2), the bottom ends of the inner four-petal module (2) are sequentially inserted into inner four-petal membrane placing holes (102) of the compacting base module (1), and the top ends of the inner four-petal module (2) are provided with a central positioning module (4);

vaseline is uniformly coated on the whole inner wall and the bottom of the outer wall of the outer three-petal module (15), and the bottom end of the outer three-petal module (15) is sequentially inserted into an outer three-petal membrane placing groove (103) of the compaction base module (1);

the outer hoop (14) is sleeved on the outer side of the middle part of the outer three-valve module (15), and the outer three-valve module (15) is fixed into a cylindrical whole;

a hollow cylindrical soil sample (3) is placed in a soil sample groove formed by the inner four-valve module (2) and the outer three-valve module (15); the top of hollow cylinder soil sample (3) is provided with drop hammer module (6), and drop hammer module (6) are installed in the bottom of location compaction measuring module (7), and the top and the central location module (4) of location compaction measuring module (7) are connected.

2. The annular compaction apparatus for preparing a hollow cylindrical sample according to claim 1, wherein: the compaction base module (1) comprises a compaction base (101), an inner four-valve placing hole (102), an outer three-valve placing groove (103) and a rubber inner membrane plug (104); the inner four-valve module (2) is sequentially inserted into an inner four-valve placing hole (102), the rubber inner membrane plug (104) is installed in an inner membrane hole formed by the inner four-valve module (2), and the outer three-valve module (15) is sequentially inserted into an outer three-valve placing groove (103).

3. The annular compaction apparatus for preparing a hollow cylindrical sample according to claim 1, wherein: the inner four-valve module (2) comprises an inner four-valve A (201), an inner four-valve B (202), an inner four-valve C (203) and an inner four-valve D (204); wherein, the shape of the inner four-valve A (201) is the same as that of the inner four-valve B (202), and the cross section of the inner four-valve C (203) is in a ring shape of (120); the cross section of the inner four-valve D (204) is trapezoidal.

4. The annular compaction apparatus for preparing a hollow cylindrical sample according to claim 1, wherein: the center positioning module (4) comprises a center positioning rod base (401), a center positioning rod extension section (402), a center positioning rod (403) and a leveling bubble (404); the central positioning rod base (401) comprises four valve clamping grooves (405) and base connecting bolts (406); a circle of concave four-petal clamping grooves (405) are formed in the outer side of the bottom of the central positioning rod base (401), and proper vaseline is smeared on the inner side walls of the four-petal clamping grooves (405); the top of the center positioning rod base (401) is connected with a center positioning rod extension section (402) through a base connecting bolt (406), the top of the center positioning rod extension section (402) is in threaded connection with a center positioning rod (403), and the top of the center positioning rod (403) is also provided with a leveling bubble (404).

5. The annular compaction apparatus for preparing a hollow cylindrical sample according to claim 1, wherein: the drop hammer module (6) comprises a drop hammer rod (601) and an annular drop hammer (5); the annular drop hammer (5) comprises an annular drop hammer body 501, a drop hammer rod connecting screw hole (502) and a compaction rod hole (503); the whole annular drop hammer (5) is sleeved on the drop hammer rod (601) through the drop hammer rod connecting screw hole (502), and the compaction rod hole (503) is sleeved on the compaction rod (702) of the positioning compaction measuring module (7).

6. The annular compaction apparatus for preparing a hollow cylindrical sample according to claim 1, wherein: the positioning compaction measuring module (7) comprises an annular compaction chassis (701), a compaction rod (702), a connecting bolt (703), a center positioner (704), a center positioning hole (705) and a scale mark (706); the whole annular compaction chassis (701) is annular, a compaction rod (702) is arranged at the upper part of the annular compaction chassis (701), the top of the compaction rod (702) is connected with a central locator (704) through a connecting bolt (703), and the middle part of the central locator (704) is provided with a central positioning hole (705); the periphery of the tamping rod (702) is also provided with scale marks (706).

7. The annular compaction apparatus for preparing a hollow cylindrical sample according to claim 1, wherein: the annular compaction device also comprises an outer cylinder extension section (13), a top disc (10), a support rod (9) and an adjusting bolt (12); the outer cylinder extension section (13) is installed at the top of the outer three-valve module (15), the top plate (10) is sleeved outside the joint of the outer cylinder extension section (13) and the outer three-valve module (15), the supporting rod (9) penetrates through a through hole reserved in the top plate (10), the supporting rod is spirally installed in a threaded hole reserved in the chassis (8), and the top of the supporting rod (9) is provided with an adjusting bolt (12).

8. The annular compaction apparatus for preparing a hollow cylindrical sample according to claim 1, wherein: the annular compaction device further comprises a sample removing gasket assembly (11), wherein the sample removing gasket assembly (11) comprises a bottom sample removing gasket (1101) and a top sample removing gasket (1102), and the bottom sample removing gasket (1101) is in the shape of a two-piece semicircular ring; the top-surface sample-removing washer (1102) is in the shape of a full-circle ring.