A system and method for preparing a sample for a spherical wave loading test of a granular material

Abstract

The application provides a granular material spherical wave loading test sample preparation system and method, and solves the problem that the existing technology generally adopts a method of crushing and refining raw materials and then reshaping to form a sample, the precision of the sample is limited, and the test result is inaccurate when loess is taken as a research object; the device comprises a positioning disc, a locking structure, a pressure head, a pressure plate, a flat head plug column, a hemispherical head plug column and a mold cylinder; the mold cylinder is in a split structure in the circumferential direction; a through radial notch is arranged in the middle of the mold cylinder, and a stepped hole is arranged in the center of the pressure plate; the flat head plug column and the hemispherical head plug column are alternately installed in the large-diameter end of the stepped hole when a lower structure of the sample is pressed; the positioning disc is arranged on the upper end or the inner side of the upper end of the mold cylinder, a locking hole is arranged in the center of the positioning disc, the locking structure is arranged at the locking hole, and at least two through holes are arranged on the positioning disc; the upper end of the pressure head is located above the positioning disc, and the lower end of the pressure head is in contact with the pressure plate after penetrating the through hole, and a sample preparation method is further provided.

Description

TECHNICAL FIELD

[0001] The present application relates to a stress wave loading test sample preparation system used in the field of rock-soil material explosion impact dynamics test research, in particular to a spherical wave loading test sample preparation system and method for granular material. BACKGROUND

[0002] The dynamic mechanical properties of rock-soil medium have a significant impact on the energy coupling of underground explosion and stress wave propagation. It has significant academic value and engineering significance to clarify the dynamic mechanical properties of rock-soil medium under explosion load. The current methods for studying the dynamic mechanical properties of rock-soil medium include Hopkinson bar test, flat plate impact test, and spherical wave loading test. Hopkinson bar can load one-dimensional stress wave on the material, and can study the dynamic mechanical properties of the material under medium-high strain rate. Flat plate impact test can load one-dimensional strain wave on the material, and can study the dynamic mechanical properties of the material under high pressure and high strain rate. Spherical wave loading test can load spherical wave on the material, and can study the dynamic mechanical properties of the material under three-dimensional stress-strain conditions, which can provide a more accurate material model for the simulation of underground explosion seismic waves.

[0003] The spherical wave loading test in the laboratory studied by Lu Qiang et al. (Lu Qiang, Wang Zhanjiang, Zhu Yurong, et al. Time-domain and frequency-domain analysis of measured spherical wave particle velocity in granite [J]. Modern Applied Physics, Vol. 9(4), 2018.12.) is to place a spherical explosive at the center of the sample, and a detonating cord is drawn from the center of the explosive sphere. A circular ring-shaped particle velocity meter made of enameled wire is embedded on the central plane of the sample in the height direction, and then the entire sample is placed in a magnetic field. When the explosive sphere explodes and causes the particles in the medium to move, it will drive the particle velocity meter to move together, thereby cutting the magnetic induction lines to form an induced electromotive force, and the particle velocity in the medium can be obtained by measuring the induced electromotive force.

[0004] When the research object is a hard medium such as rock, on-site coring, cutting, carving, and processing are generally used, while for granular materials such as loess and alluvial soil, it is difficult to process samples by on-site coring, and only by crushing and refining the raw materials and then reshaping them. Since the laboratory spherical wave loading test is a scaled-down test of the on-site closed explosion test, it is necessary to ensure the equivalence with the on-site test, and high precision is required for sample preparation. Therefore, it is necessary to design a sample preparation system for granular material spherical wave loading test. SUMMARY

[0005] The present application aims to solve the problem that it is difficult to prepare samples by on-site coring processing when loess, alluvial soil and other granular materials are taken as research objects in the prior art, and only the method of crushing and refining the raw materials and then reshaping them can be used to prepare the samples, and a granular material spherical wave loading test sample preparation system and method are provided.

[0006] To achieve the above-mentioned purpose, the technical scheme adopted by the present application is as follows:

[0007] A granular material spherical wave loading test sample preparation system, which is characterized in that:

[0008] The system comprises a positioning disc, a locking structure, a pressure head, a pressure plate, a flat-head plug column, a hemispherical-head plug column and a mold cylinder.

[0009] The mold cylinder is in a split structure in the circumferential direction, and the split structures are detachably connected.

[0010] The inner diameter of the mold cylinder is matched with the diameter of the sample to be prepared, and a through gap is arranged in the middle of the mold cylinder, which is used to pass through the lead wire of a particle velocity meter arranged inside the sample during sample preparation.

[0011] The pressure plate is arranged inside the mold cylinder during sample pressing, the outer diameter of the pressure plate is matched with the inner diameter of the mold cylinder, a stepped hole is arranged in the center of the pressure plate, the size of the small-diameter section of the stepped hole is matched with the size of the outer shielding tube of the loading assembly arranged inside the sample, and the size of the large-diameter section of the stepped hole is matched with the size of the upper end of the flat-head plug column and the hemispherical-head plug column.

[0012] The flat-head plug column and the hemispherical-head plug column are alternately arranged in the large-diameter end of the stepped hole during pressing of the lower structure of the sample.

[0013] The positioning disc is coaxially arranged on the upper end or the inner side of the upper end of the mold cylinder and is located above the pressure plate during pressing of the upper structure of the sample, a locking hole is arranged in the center of the positioning disc, the locking structure is arranged at the locking hole and is used to fix the position of the outer shielding tube of the loading assembly arranged inside the sample, and at least two through holes are arranged on the positioning disc.

[0014] The pressure head is arranged above the positioning disc during pressing of the upper structure of the sample, the lower end of the pressure head is in contact with the pressure plate after passing through the through hole, and an external press sequentially passes through the pressure head and the pressure plate to press the sample.

[0015] Further, the diameter of the pressure plate is 0.5 mm smaller than the inner diameter of the mold cylinder.

[0016] Further, the through gap is arranged in the middle of any split structure of the mold cylinder.

[0017] Further, the positioning disc comprises an outer ring, an inner ring and at least two connecting rods connecting the outer ring and the inner ring.

[0018] The locking hole is arranged at the center of the inner ring, and the outer ring is arranged on the mold cylinder, and the through hole is formed between the two adjacent connecting rods.

[0019] Further, the locking structure comprises a fastening nut and a locking buckle of the boss structure, the large-diameter end of the locking buckle is larger in diameter than the locking hole, the small-diameter end of the locking buckle is matched with the diameter of the locking hole and is arranged in the locking hole from top to bottom, the center of the locking buckle is provided with a bushing for the outer shielding tube to pass through, and the fastening nut is used for being threadedly connected to the outside of the upper end of the outer shielding tube, the large-diameter end of the locking buckle is abutted against the end face of the fastening nut, and the fixing of the outer shielding tube is realized.

[0020] Further, the fixing screw is further included.

[0021] The inner thread is arranged at the upper end of the flat head plug column and the hemispherical head plug column, the fixing screw is threadedly installed in the flat head plug column or the hemispherical head plug column through the small-diameter section of the stepped hole of the pressing plate, the screw cap of the fixing screw is attached to the end face of the pressing plate, and the fixing of the flat head plug column or the hemispherical head plug column is realized.

[0022] The application further provides a particle material spherical wave loading test sample preparation method, and the speciality thereof is that the particle material spherical wave loading test sample preparation system is used, and the following steps are included.

[0023] Step 1: according to the upper layer structure and the lower layer structure of the sample, the sample preparation raw material is divided into upper layer raw material and lower layer raw material;

[0024] Step 2: pressing of the lower layer structure

[0025] 2.1 the lower layer raw material is divided into N parts, and the corresponding pressing height of each part of raw material is obtained, wherein N>1;

[0026] 2.2 the first part of lower layer raw material is uniformly placed into the mold cylinder, the flat head plug column is placed horizontally in the mold cylinder at the large-diameter end of the stepped hole of the pressing plate, the pressing plate is pressed, the first part of lower layer raw material is pressed to the corresponding height, the pressing state is maintained for not less than 30 min, then the pressing plate is taken out, and the flat head plug column is in contact with the first part of lower layer raw material;

[0027] 2.3 the same method as that in step 2.2 is used to press the next part of sample on the first part of sample which is pressed, until the pressing of the N-1 part of sample is completed;

[0028] 2.4 the Nth part of lower layer raw material is uniformly placed into the mold cylinder on the N-1 part of sample which is prepared, the flat head plug column on the pressing plate is replaced by the hemispherical head plug column and is horizontally placed in the mold cylinder, the pressing plate is pressed, the Nth part of lower layer raw material is pressed to the corresponding height, the pressing state is maintained for not less than 30 min, then the pressing plate is taken out, and the lower layer structure with the hemispherical surface groove is obtained.

[0029] Step 3: pressing of the upper structure

[0030] 3.1 Set the loading assembly in the center of the lower structure, and keep the explosive ball of the loading assembly set at the semispherical recess; at the same time, coaxially set the particle velocity meter on the lower structure, keep the particle velocity meter concentric with the semispherical recess, and lead the lead wire of the particle velocity meter out from the through gap; at the same time, divide the upper raw material into Q parts, and obtain the corresponding pressing height of each part of the raw material, wherein Q>1;

[0031] 3.2 Disassemble the semispherical head plug column;

[0032] 3.3 Place the first part of the upper raw material uniformly above the lower structure and the particle velocity meter, reversely set the pressing plate and sleeve it on the outer shielding tube of the loading assembly, horizontally set it inside the mold cylinder, set the positioning disc on the upper end of the mold cylinder, and fix the outer shielding tube at the locking hole of the positioning disc through the locking structure; install the pressing head, make the lower end of the pressing head contact with the pressing plate after passing through the through hole on the positioning disc, press the pressing head, press the first part of the upper raw material to the corresponding height, keep the pressing state for not less than 30 minutes, and complete the pressing of the first part of the upper sample;

[0033] 3.4 Release the pressure, and take out the pressing head, the locking structure, the positioning disc and the pressing plate;

[0034] 3.5 Use the same method as steps 3.3 and 3.4 to press the next part of the upper sample on the pressed first part of the upper sample, until the pressing of the Q-1 part of the upper raw material is completed;

[0035] 3.6 Use the same method as step 3.3 to complete the pressing of the Q part of the upper raw material;

[0036] Step 4: disassemble the spherical wave loading test sample preparation system of the granular material, and obtain the sample.

[0037] Further, the step 4 is specifically:

[0038] Keep the pressing state, disassemble the mold cylinder, release the pressure, and then take down the pressing head, the locking structure, the positioning disc and the pressing plate in sequence, and complete the preparation of the spherical wave loading test sample of the granular material.

[0039] Further, in steps 2.1 and 3.1, the pressing thickness corresponding to any one of the parts of the raw material is less than or equal to 1 / 2 of the sample pressing height.

[0040] Compared with the prior art, the present application has the beneficial technical effects as follows:

[0041] 1、The present application, through the combination of positioning disc and locking structure, forms good positioning effect on the loading assembly in the sample, thereby avoiding the position displacement of the loading assembly in the sample pressing process, and ensuring the sample precision and reliability.

[0042] 2、The present application adopts split type mold cylinder, which can ensure assembly precision and facilitate sample demolding after pressing.

[0043] 3、The present application adopts the mode of pressing plate with holes matched with replaceable plug column, realizes the pressing of plane, different diameter ball hole surface, avoids the processing of multiple pressing plates, and reduces the processing cost.

[0044] 4、The present application adopts the pressing head diameter smaller than the mold cylinder by 0.5 mm, which is verified by test, can ensure the free movement of the pressing head in the mold cylinder, and prevent the leakage of fine soil particles from the gap, thereby ensuring the smoothness of the sample preparation process and the sample precision.

[0045] 5、The present application can be used for sample preparation of soil, soil sand mixture and other particulate spherical wave loading test, and provides support for the research on spherical wave propagation characteristics of geotechnical materials. BRIEF DESCRIPTION OF DRAWINGS

[0046] Figure 1 is the use state structure schematic diagram of the particle material spherical wave loading test sample preparation system embodiment one of the present application;

[0047] Figure 2 is the structure schematic diagram of the flat head plug column in the embodiment one of the present application;

[0048] Figure 3 is the structure schematic diagram of the half ball head plug column in the embodiment one of the present application;

[0049] Figure 4 is the loading system structure schematic diagram in the embodiment one of the present application;

[0050] Figure 5 is the loading system structure schematic diagram in the embodiment two of the present application;

[0051] Figure 6 is the assembly structure schematic diagram of the pressing plate and the flat head plug column in the embodiment one of the present application;

[0052] REFERENCE NUMERALS:

[0053] 1, pressing machine; 2, mold cylinder; 3, positioning disc; 4, locking buckle; 5, pressing head; 6, pressing plate; 71, flat head plug column; 72, half ball head plug column; 8, particle velocity meter; 9, detonating cord; 10, outer shielding tube; 11, inner shielding tube; 12, explosive ball; 13, sample; 14, loading assembly; 15, protective soil core; 16, first inner shielding tube; 17, second inner shielding tube. Detailed Implementation

[0054] Example 1:

[0055] like Figure 4 As shown, the loading system includes a loading component 14 and a particle velocimeter 8;

[0056] The loading component 14 includes a detonating cord 9, an outer shielding tube 10, a protective soil core 15, an inner shielding tube 11, and an explosive ball 12.

[0057] The inner shielding tube 11 includes a first inner shielding tube 16 and a second inner shielding tube 17. The length of the second inner shielding tube 17 is less than the length of the first inner shielding tube 16. The density of the protective soil core 15 is the same as the density of the sample 13.

[0058] The protective soil core 15 has a frustum-shaped structure. A semi-circular notch, compatible with the explosive ball 12, is provided in the center of the large-diameter end face. A downward-facing mounting hole is coaxially provided in the center of the small-diameter end. The lower end of the mounting hole is tangent to the semi-circular notch. The inner diameter of the mounting hole matches the outer diameter of the second inner shielding tube 17. The lower end of the second inner shielding tube 17 is positioned within the mounting hole with an interference fit, and the lower end of the second inner shielding tube 17 is flush with the lower end of the mounting hole. The upper end of the second inner shielding tube 17 protrudes from the mounting hole and is positioned outside the protective soil core 15. The first inner shielding tube 16 is coaxially positioned... The outer shielding tube 10 is sleeved outside the first inner shielding tube 16 and the second inner shielding tube 17, and there is a gap between the outer shielding tube 10 and the second inner shielding tube 17 and the first inner shielding tube 16. The lower end of the outer shielding tube 10 is set on the upper end surface of the protective soil core 15. The upper end of the outer shielding tube 10 is lower than the upper end of the first inner shielding tube 16. The explosive ball 12 is set in the semi-circular notch. The lower end of the detonating cord 9 is connected to the explosive ball 12, and the upper end passes through the second inner shielding tube 17 and the first inner shielding tube 16 in sequence, and is placed outside the first inner shielding tube 16.

[0059] The inner diameter and outer diameter of the first inner shielding tube 16 and the second inner shielding tube 17 are the same, and the upper end of the outer shielding tube 10 is provided with an external thread.

[0060] Based on the above system, such as Figure 1 , Figure 2 and Figure 3 As shown, the present invention provides a sample preparation system for spherical wave loading test of particulate materials, including a mold cylinder 2, a positioning disk 3, a locking structure, a pressure head 5, a pressure plate 6, a flat-headed plug 71, and a hemispherical-headed plug 72.

[0061] The inner diameter of the mold cylinder 2 is matched with the diameter of the sample 13 to be pressed, and the mold cylinder 2 is composed of a third shell and a fourth shell which are of the same structure, a first shell and a second shell which are of the same structure as the half-hoop structure, the third shell including a third body and a semicircular plate mounted on one side of the third body, a plurality of protrusions being arranged on the other side of the third body, the third shell and the fourth shell being oppositely arranged and bolt-connected to form a lower structure (a hollow cylindrical structure with one end open) of the mold cylinder 2, the first shell and the second shell being provided with grooves corresponding in number to the protrusions at one end, the first shell and the second shell being oppositely arranged and bolt-connected to form an upper structure (an axially-through cylindrical structure) of the mold cylinder 2, the upper structure of the mold cylinder 2 and the lower structure of the mold cylinder 2 being assembled through the positioning of the protrusions and the grooves, and the mold cylinder 2 composed of four parts facilitating demolding.

[0062] A through gap (arranged on the third shell or the fourth shell) is arranged on the upper part of the lower structure of the mold cylinder 2 for the lead of the particle velocity meter 8 to pass through, the gap extending at both ends to form an included angle of 120°, and the depth of the gap along the axial direction being 5 mm.

[0063] The positioning disc 3 includes an outer ring, an inner ring, and three connecting rods connecting the outer ring and the inner ring, the three connecting rods being uniformly arranged; the center of the inner ring is provided with a locking hole, the diameter of the outer ring is less than or equal to the inner diameter of the mold cylinder 2, and the positioning disc 3 is arranged on the upper edge of the mold cylinder 2 when the sample 13 is pressed, a through hole being formed between adjacent two connecting rods.

[0064] The locking structure includes a locking buckle 4 and a fastening nut, the locking buckle 4 including a first column and a second column, the diameter of the first column being smaller than the diameter of the second column, so that the first column and the second column are coaxially connected to form a boss structure, the diameter of the first column being smaller than the diameter of the locking hole, and the diameter of the second column being larger than the diameter of the locking hole, a through insertion hole being arranged in the middle of the locking buckle 4 for the outer shielding tube 10 to pass through, the diameter of the insertion hole being larger than the outer diameter of the outer shielding tube 10.

[0065] The pressure head 5 includes a force bearing plate of a disc structure and three support plates uniformly mounted on one side of the force bearing plate in the circumferential direction, the support plates being capable of passing through the gap between any two adjacent connecting rods.

[0066] As shown in Figure 6 , the pressing plate 6 is of a disc structure, the pressing plate 6 being provided with a stepped hole in the center, the small-diameter end of the stepped hole being matched with the structure of the outer shielding tube 10, and the outer diameter of the pressing plate 6 being 0.5 mm smaller than the inner diameter of the mold cylinder 2.

[0067] As shown in Figure 2 and Figure 3As shown, the flat head plug post 71 and the hemispherical head plug post 72 are alternately installed on the pressing plate 6 when pressing the lower structure of the sample 13, the axial length of the flat head plug post 71 is equal to the length of the large diameter section of the stepped hole, the diameter of the flat head plug post 71 is matched with the diameter of the small diameter section of the stepped hole (the flat head plug post 71 is clearance fit with the small diameter section of the stepped hole), and the middle of one end of the flat head plug post 71 is provided with an internal threaded hole; the hemispherical head plug post 72 comprises a plug post body in a cylindrical structure and a hemispherical head installed at the middle of one end of the plug post body, the diameter of the hemispherical head is the same as the diameter of the explosive ball 12, the axial length of the plug post body is equal to the length of the large diameter section of the stepped hole, the diameter of the plug post body is matched with the diameter of the large diameter section of the stepped hole (the plug post body is clearance fit with the large diameter section of the stepped hole), and the middle of the other end of the plug post body is provided with an internal threaded hole.

[0068] The assembly mode of the device is as follows:

[0069] The assembly mode of the device when pressing the lower structure:

[0070] When the lower part of the lower structure of the sample 13 is pressed, the flat head plug post 71 is first installed on the pressing plate 6, the flat head plug post 71 is placed in the large diameter section of the stepped hole of the pressing plate 6, and the fixed screw is threadedly connected to the upper end of the flat head plug post 71 through the small diameter section of the stepped hole of the pressing plate 6, so that when the end face of the flat head plug post 71 abuts against the stepped face of the stepped hole of the pressing plate 6, the nut of the fixed screw is attached to the upper end face of the pressing plate 6, thereby realizing the fixation of the flat head plug post 71, ensuring that the lower end face of the flat head plug post 71 is flush with the lower end face of the pressing plate 6 after the flat head plug post 71 is installed, and ensuring the precision and reliability of the pressing of the sample 13, and when the lower structure is pressed, the pressing plate 6 with the installed flat head plug post 71 is placed above the raw material for pressing.

[0071] When the upper part of the lower structure of the sample 13 is pressed (at this time, the hemispherical hole for arranging the explosive ball 12 needs to be left), the hemispherical head plug post 72 is first installed on the pressing plate 6, the hemispherical head plug post 72 is placed in the large diameter section of the stepped hole of the pressing plate 6, and the fixed screw is threadedly connected to the upper end of the hemispherical head plug post 72 through the small diameter section of the stepped hole of the pressing plate 6, so that when the end face of the hemispherical head plug post 72 abuts against the stepped face of the stepped hole of the pressing plate 6, the nut of the fixed screw is attached to the upper end face of the pressing plate 6, thereby realizing the fixation of the hemispherical head plug post 72, and after the hemispherical head plug post 72 is installed, the end of the lower end face of the pressing plate 6 in contact with the raw material of the sample 13 can protrude a hemispherical body for pressing the hemispherical recess, and when the upper part of the lower structure is pressed, the pressing plate 6 with the installed hemispherical head plug post 72 is placed above the raw material for pressing.

[0072] The assembly mode of the device when pressing the upper structure:

[0073] The pressing plate 6 is placed on the raw material inside the mold cylinder 2 in the opposite direction of the lower structure (i.e. the large diameter section faces upwards, and the small diameter section faces the raw material), and the outer shielding tube 10 passes through the stepped hole on the pressing plate 6, the positioning disc 3 is placed on the mold cylinder 2, and the outer shielding tube 10 passes through the locking hole of the positioning disc 3, the locking buckle 4 is sleeved on the outside of the outer shielding tube 10, and the first column of the locking buckle 4 is located in the locking hole, the second column of the locking buckle 4 overlaps above the positioning disc 3, then the fastening nut is threadedly connected to the upper end of the outer shielding tube 10 until the lower end of the fastening nut abuts against the upper end of the second column of the locking buckle 4, after the pressing head 5 passes through the positioning disc 3 from top to bottom, the supporting rod of the pressing head 5 contacts the upper end of the pressing plate 6, pressure is applied to the pressing head 5, and the upper structure can be pressed.

[0074] Based on the above device, the application further provides a preparation method of a particle material spherical wave loading test sample

[0075] In this embodiment, the raw material for preparing the sample 13 is fine loess with a particle size of several microns, the density of the sample 13 is set to 1.8 g / cm 3 , the water content is the natural water content, the diameter of the sample 13 is 277 mm, and the height is 280 mm.

[0076] The maximum loadable force of the press 1 is related to the bottom area S of the sample 13, and needs to meet the requirement of generating a pressure of at least 10 MPa on the surface of the sample 13, that is, the maximum loadable force is not less than S*10 MPa.

[0077] The method comprises the following steps:

[0078] Preparation:

[0079] Assembling the loading assembly 14:

[0080] A. The detonating cord 9 with the 5 mm diameter explosive ball 12 is sequentially threaded through the first inner shielding tube 16 with an outer diameter of 2 mm and an inner diameter of 1.2 mm and the second inner shielding tube 17, until the bottom surface of the first inner shielding tube 16 is tangent to the explosive ball 12;

[0081] B. The outer shielding tube 10 with an outer diameter of 4 mm is sleeved outside the first inner shielding tube 16 and the second inner shielding tube 17, until the bottom is arranged on the protective soil core 15;

[0082] C. The first inner shielding tube 16, the second inner shielding tube 17 and the outer shielding tube 10 are fixedly bonded by using glue;

[0083] Step 1: The upper structure and the lower structure of the sample 13 are both set to 140 mm in height; the lower structure of the mold cylinder 2 is 140 mm in height, and the upper structure is 250 mm in height, according to the upper structure and the lower structure of the sample 13, the sample 13 raw material is divided into upper raw material and lower raw material;

[0084] Step 2: pressing of the lower structure

[0085] 2.1 Divide the lower raw material into 2 parts, and obtain the corresponding height of 70mm after pressing for each part, and the mass of each part of raw material is 7593g;

[0086] 2.2 Put the first part of the lower raw material into the mold cylinder 2, stir the raw material evenly, and initially place it flat, install the flat head plug column 71 at the step hole of the pressing plate 6, and place the pressing plate 6 with the flat head plug column 71 installed horizontally inside the mold cylinder 2 to adhere to the first part of the lower raw material, start the press 1 to press the pressing plate 6, press the first layer of raw material to 70mm, then keep pressing for 30min, then close the press 1 to release the pressure, and take out the pressing plate 6;

[0087] 2.3 On the prepared first sample 13, put the second part of the lower raw material into the mold cylinder 2, stir the raw material evenly, and initially place it flat, replace the flat head plug column 71 on the pressing plate 6 with a hemispherical head plug column 72 (the diameter of the hemispherical head body is 5mm), and place the pressing plate 6 with the hemispherical head plug column 72 installed horizontally inside the mold cylinder 2 so that the hemispherical head plug column 72 is in contact with the second part of the lower raw material, start the press 11 to press the pressing plate 6, press the second part of the lower raw material to a total height of 140mm, then keep pressing for 30min, then close the press 11 to release the pressure, and take out the pressing plate 6 to obtain a lower structure with a hemispherical recess;

[0088] Step 3: pressing of the upper structure

[0089] 3.1 Set the loading assembly 14 at the center of the lower structure, and keep the explosive ball 12 of the loading assembly 14 set at the hemispherical recess (fixed with glue); At the same time, set the particle velocity meter 8 coaxially on the lower structure, keep the particle velocity meter 8 coaxial with the hemispherical recess, and lead the lead wire of the particle velocity meter out of the gap of the lower mold cylinder; At the same time, divide the upper raw material into 2 parts, and obtain the corresponding height of 70mm after pressing for each part, and the mass of each part of raw material is 7587g; (The weight of the sample preparation raw material corresponding to the volume occupied by the loading assembly 3 has been deducted);

[0090] 3.2 Remove the hemispherical head plug column 72 on the pressing plate 6;

[0091] 3.3 Put the first portion of the upper layer material (layer 3) on the lower layer structure, mix the material evenly and place it flat. Set the pressing plate 6 on the outer shielding tube 10 of the loading assembly 14 from top to bottom, and then set it horizontally inside the mold cylinder 2. Install the locking structure in the locking hole of the positioning disc 3, and then set the positioning disc 3 on the upper end of the mold cylinder 2. Place the positioning disc 3 on the mold cylinder 2, and make the outer shielding tube 10 pass through the locking hole of the positioning disc 3. Set the locking buckle 4 on the outside of the outer shielding tube 10, and make the first column of the locking buckle 4 located in the locking hole, and the second column of the locking buckle 4 located above the positioning disc 3. Then thread the fastening nut on the upper end of the outer shielding tube 10 until the lower end of the fastening nut abuts against the upper end of the second column of the locking buckle 4 (to prevent the loading assembly 14 from moving downward due to friction between the material and the outer wall of the shielding tube during the pressing of the sample 13). After the pressing head 5 passes through the positioning disc 3 from top to bottom, the support rod of the pressing head 5 contacts the upper end of the pressing plate 6. The press 1 applies pressure to the pressing head 5, and the first portion of the upper layer material is pressed to a total height of 210 mm. Then keep the pressure for 30 minutes to complete the pressing of the first portion of the upper layer sample 13.

[0092] 3.4 Release the pressure, and remove the pressing head 5, the locking buckle 4, the fastening nut, the positioning disc 3, and the pressing plate 6.

[0093] 3.5 Add the remaining upper layer sample 13 material (layer 4) on the upper end of the prepared first portion of the upper layer sample 13. Mix the material evenly and place it flat. Set the pressing plate 6 on the outer shielding tube 10 of the loading assembly 14 from top to bottom, and then set it horizontally inside the mold cylinder 2. Install the locking structure in the locking hole of the positioning disc 3, and then set the positioning disc 3 on the upper end of the mold cylinder 2. Place the positioning disc 3 on the mold cylinder 2, and make the outer shielding tube 10 pass through the locking hole of the positioning disc 3. Set the locking buckle 4 on the outside of the outer shielding tube 10, and make the first column of the locking buckle 4 located in the locking hole, and the second column of the locking buckle 4 located above the positioning disc 3. Then thread the fastening nut on the upper end of the outer shielding tube 10 until the lower end of the fastening nut abuts against the upper end of the second column of the locking buckle 4. After the pressing head 5 passes through the positioning disc 3 from top to bottom, the support rod of the pressing head 5 contacts the upper end of the pressing plate 6. The press 1 applies pressure to the pressing head 5, and the second portion of the upper layer material is pressed to a total height of 280 mm. Then keep the pressure for 30 minutes to complete the pressing of the upper layer structure.

[0094] Step 4: Keep the press 1 in the pressing state to ensure that the sample 13 is not misaligned. Remove the upper half of the mold cylinder 22, the lower half of the mold cylinder 22, release the pressure, and then remove the pressing head 5, the locking buckle 4, the positioning disc 3, and the pressing plate 6 in sequence. Complete the preparation of the granular material spherical wave loading test sample 13, and obtain the sample 13.

[0095] The particle material spherical wave loading test sample 13 preparation system and method can be used for sample 13 production of soil, soil-sand mixture and other bulk particle spherical wave loading test, and can provide support for the spherical wave propagation characteristic research of rock and soil materials.

[0096] Embodiment 2:

[0097] The difference between Embodiment 2 and Embodiment 1 is that:

[0098] As shown in Figure 5 , the loading assembly 14 does not contain the protective soil core 15, and the inner layer shielding tube 11 is integrally arranged.

[0099] Finally, it should be noted that: the above embodiments are only used to illustrate the technical solutions of the present application, and not to limit them; although the present application has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that: it can still modify the technical solutions recorded in the foregoing embodiments, or make equivalent replacement for part or all of the technical features; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the scope of the technical solutions of the present application.

Claims

1. A granular material spherical wave loading test sample preparation system, characterized in that: it comprises a positioning disc (3), a locking structure, a pressure head (5), a pressure plate (6), a flat head plug column (71), a hemispherical head plug column (72), and a mold cylinder (2); the mold cylinder (2) is in a split structure along the circumference, and the split structures are detachably connected; the inner diameter of the mold cylinder (2) is matched with the diameter of the sample (13) to be prepared, and the middle part of the mold cylinder (2) is provided with a through gap for the lead wire of a particle velocity gauge (8) arranged inside the sample (13) to pass out when the sample (13) is prepared; the pressure plate (6) is arranged inside the mold cylinder (2) when the sample is pressed, the outer diameter of the pressure plate (6) is matched with the inner diameter of the mold cylinder (2), the center of the pressure plate (6) is provided with a stepped hole, the size of the small-diameter section of the stepped hole is matched with the size of the outer shielding tube (10) in the loading assembly (14) arranged inside the sample (13), and the size of the large-diameter section of the stepped hole is matched with the size of the upper end of the flat head plug column (71) and the hemispherical head plug column (72); the flat head plug column (71) and the hemispherical head plug column (72) are alternately arranged in the large-diameter end of the stepped hole when the lower structure of the sample (13) is pressed; the positioning disc (3) is coaxially arranged on the upper end or the inner side of the upper end of the mold cylinder (2) and is located above the pressure plate (6) when the upper structure of the sample (13) is pressed, the center of the positioning disc (3) is provided with a locking hole, the locking structure is arranged at the locking hole and is used for fixing the position of the outer shielding tube (10) in the loading assembly (14) arranged inside the sample (13), and at least two through holes are arranged on the positioning disc (3); the pressure head (5) is located above the positioning disc (3) when the upper structure of the sample (13) is pressed, the lower end of the pressure head (5) is in contact with the pressure plate (6) after passing through the through hole, and an external press (1) presses the sample (13) through the pressure head (5) and the pressure plate (6) in sequence; the locking structure comprises a locking buckle (4) of a fastening nut and a boss structure, the large-diameter end of the locking buckle (4) is larger in diameter than the locking hole, the small-diameter end of the locking buckle (4) is matched with the diameter of the locking hole and is arranged in the locking hole from top to bottom, the center of the locking buckle (4) is provided with a plug hole through which the outer shielding tube (10) passes, the fastening nut is used for being threadedly connected to the outside of the upper end of the outer shielding tube (10), the large-diameter end of the locking buckle (4) is in abutment with the fastening nut, and the outer shielding tube (10) is fixed; further comprising a fixing screw; the upper end of the flat head plug column (71) and the hemispherical head plug column (72) is provided with an internal thread, the fixing screw is threadedly arranged on the flat head plug column (71) or the hemispherical head plug column (72) through the small-diameter section of the stepped hole of the pressure plate (6), and the fixing screw is in abutment with the end face of the pressure plate (6) through the screw cap of the fixing screw, so that the flat head plug column (71) or the hemispherical head plug column (72) is fixed.

2. The granular material spherical wave loading test sample preparation system according to claim 1, characterized in that: the diameter of the pressure plate (6) is smaller than the inner diameter of the mold cylinder (2) by 0.5 mm. ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ 3. The system for preparing a sample for a spherical wave loading test of granular material according to claim 1 or 2, characterized in that: the through hole is arranged in the middle of any petal structure of the mold cylinder (2).

4. The system for preparing a sample for a spherical wave loading test of granular material according to claim 3, characterized in that: the positioning disc (3) comprises an outer ring, an inner ring and at least two connecting rods connecting the outer ring and the inner ring; the locking hole is arranged in the center of the inner ring, the outer ring is arranged on the mold cylinder (2), and the through hole is formed between the adjacent two connecting rods.

5. A method of preparing a sample for a spherical wave loading test of a granular material, characterized in that The system for preparing a sample for a spherical wave loading test of granular material according to any one of claims 1-4 comprises the following steps: Step 1: According to the upper structure and the lower structure of the sample (13), the sample (13) preparation raw material is divided into upper layer raw material and lower layer raw material; Step 2: Lower structure compression 2.1 Divide the lower layer raw material into N parts, and obtain the corresponding compression height of each part, wherein N>1; 2.2 Put the first part of the lower layer raw material into the mold cylinder (2) uniformly, place a flat head plug column (71) on the large diameter end of the stepped hole of the pressing plate (6) and then place it horizontally in the mold cylinder (2), press the pressing plate (6), and press the first part of the lower layer raw material to the corresponding height, keep the pressing state for not less than 30 min, then release the pressure, take out the pressing plate (6), and the flat head plug column (71) is in contact with the first part of the lower layer raw material; 2.3 Use the same method as step 2.2 to compress the next part of the sample (13) on the compressed first part of the sample (13), until the compression of the N-1 part of the sample (13) is completed; 2.4 Put the Nth part of the lower layer raw material into the mold cylinder (2) uniformly on the prepared N-1 part of the sample (13), replace the flat head plug column (71) on the pressing plate (6) with a hemispherical head plug column (72) and then place it horizontally in the mold cylinder (2), press the pressing plate (6), and press the Nth part of the lower layer raw material to the corresponding height, keep the pressing state for not less than 30 min, then release the pressure, take out the pressing plate (6), and obtain the lower structure with a hemispherical recess; Step 3: Compression of the upper structure 3.1 Set the loading assembly (14) at the center of the lower structure, and keep the explosive ball (12) of the loading assembly (14) arranged at the hemispherical recess; at the same time, coaxially arrange the particle velocity meter (8) on the lower structure, keep the particle velocity meter (8) concentric with the hemispherical recess, and lead the lead wire of the particle velocity meter (8) out of the through hole; at the same time, divide the upper layer raw material into Q parts, and obtain the corresponding compression height of each part, wherein Q>1; 3.2 Remove the hemispherical head plug column (72); 3.3 Place the first portion of the upper layer of raw material evenly above the lower layer structure and the particle velocity meter (8), set the pressure plate (6) in reverse and cover the outer shielding tube (10) of the loading assembly (14), horizontally set it inside the mold cylinder (2), set the positioning disc (3) on the upper end of the mold cylinder (2), and fix the outer shielding tube (10) at the locking hole of the positioning disc (3) through the locking structure; install the pressure head (5), make the lower end of the pressure head (5) contact with the pressure plate (6) after passing through the through hole on the positioning disc (3), press the pressure head (5), press the first portion of the upper layer of raw material to the corresponding height, keep the pressure state for not less than 30 minutes, complete the pressing of the first portion of the upper layer of sample (13); 3.4 Release the pressure, remove the pressure head (5), locking structure, positioning disc (3) and pressure plate (6); 3.5 Use the same method as steps 3.3 and 3.4 to press the next portion of the upper layer of sample (13) on the pressed first portion of the upper layer of sample (13), until the pressing of the Q-1 portion of the upper layer of raw material is completed; 3.6 Use the same method as step 3.3 to complete the pressing of the Q portion of the upper layer of raw material; Step 4: disassemble the particle material spherical wave loading test sample preparation system to obtain the sample (13).

6. The particle material spherical wave loading test sample preparation method according to claim 5, wherein: the step 4 is specifically: keep the pressure state, remove the mold cylinder (2), release the pressure, and then remove the pressure head (5), locking structure, positioning disc (3), and pressure plate (6) in sequence to complete the preparation of the particle material spherical wave loading test sample (13).

7. The particle material spherical wave loading test sample preparation method according to claim 5 or 6, wherein: in the step 2.1 and the step 3.1, the pressing thickness of any one of the portions of raw material is less than or equal to 1 / 2 of the pressing height of the sample (13).

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