Sample preparation method for spherical wave loading test of geomaterials with controllable porosity and moisture content

Abstract

The invention relates to a method for preparing samples for a spherical wave loading test of rock and soil materials with controllable porosity and moisture content. The method solves the problem that the porosity of rock and soil samples such as loess used in existing spherical wave loading tests is below 3% or above 30%, which is difficult to flexibly adjust and has a significant impact on energy coupling and wave propagation characteristics during the spherical wave loading test. The method comprises the following steps: 1. obtaining raw materials for sample preparation; 1.1 calculating the mass fraction of the sample fine sand raw material according to the porosity and density of the sample, the density of the loess raw material particles and the density of the fine sand raw material particles in the soil-sand mixed raw material required for the sample preparation, and obtaining a soil-sand ratio; 1.2 grinding and drying the loess raw material to obtain fine loess; simultaneously sieving the fine sand raw material to obtain fine sand particles, and uniformly mixing the two according to the soil-sand ratio to obtain a soil-sand mixed raw material; 1.3 spraying water on the soil-sand mixed raw material in step 1.2 to obtain the sample preparation raw material; and 2. pressing the sample.

Description

Technical Field

[0001] The invention belongs to the field of explosion impact dynamics of rock and soil materials, and particularly relates to a sample preparation method for a spherical wave loading test of rock and soil materials with controllable porosity and water content. Background Art

[0002] The energy coupling and wave propagation characteristics of geotechnical materials are important supports for the analysis of underground explosion seismic effects, analysis of ground strike damage effectiveness, and mining.

[0003] Porosity and water content significantly influence the energy coupling and wave propagation characteristics of geotechnical samples. Harder rocks like granite generally have porosities below 3%, while loose, porous media like alluvial soil, loess, and highly weathered rock generally have porosities greater than 30%. Softer materials like tuff have porosities between these two ranges. Current sampling methods based on hard rocks like granite generally achieve porosities below 3%, and this porosity depends on the porosity of the rock being mined, making it difficult to flexibly adjust. Sample preparation methods based on pure loess generally achieve porosities above 30%. Currently, a flexible and adjustable sampling method for spherical wave loading tests on geotechnical materials with porosities between these two ranges is lacking. Summary of the Invention

[0004] The purpose of the present invention is to solve the technical problem that the porosity of geotechnical samples such as alluvial soil, loess, and strongly weathered rock used in existing laboratory spherical wave loading tests is below 3% or above 30%, which is difficult to flexibly adjust and has a significant impact on energy coupling and wave propagation characteristics during the spherical wave loading test. The present invention provides a method for preparing geotechnical material samples for spherical wave loading tests with controllable porosity and moisture content.

[0005] In order to achieve the above object, the technical solution adopted by the present invention is:

[0006] A method for preparing samples for a spherical wave loading test of geotechnical materials with controllable porosity and moisture content is characterized in that it comprises the following steps:

[0007] Step 1: Obtain sample preparation materials

[0008] 1.1 Based on the porosity and density of the sample, the density requirement of the loess in the sample, and the density of the loess particles and the density of the fine sand particles in the soil-sand mixture required for sample preparation, calculate the mass fraction of the fine sand in the soil-sand mixture required for sample preparation and obtain the soil-sand ratio;

[0009] 1.2 Grind the loess raw material into micron-sized fine particles and dry them to obtain fine loess; at the same time, sieve the fine sand raw material to retain fine sand particles between 30 and 160 meshes, and evenly mix the fine loess and fine sand particles according to the soil-sand ratio in step 1.1 to obtain a soil-sand mixed raw material;

[0010] 1.3 According to the moisture content requirements of the sample, evenly spray water into the soil-sand mixed raw material in step 1.2 to obtain the sample preparation raw material;

[0011] Step 2: Press the sample

[0012] 2.1 Pour the quantitative sample preparation raw materials evenly into the mold cylinder and press them to obtain the lower structure of a predetermined height;

[0013] 2.2 Place the test particle velocity meter and loading assembly at the center of the upper surface of the substructure;

[0014] 2.3 Evenly place the remaining sample preparation materials into the mold cylinder at the upper end of the lower structure for pressing. After the pressing is completed, remove the mold cylinder to obtain the sample.

[0015] Furthermore, in step 1, the mass fraction β of the fine sand raw material in the soil-sand mixed raw material required for preparing the sample is calculated by the following formula: 砂 ;

[0016]

[0017] Among them, η 土砂 is the porosity of the sample, ρ 土砂 is the density of the sample, ρ 土体 is the density of the loess in the sample, ρ 砂 is the density of fine sand particles, ρ 土粒 is the density of loess particles.

[0018] Furthermore, in step 1.3, the mass of the water is Where, M is the total mass of the sample, is the moisture content of the sample.

[0019] Furthermore, step 2.1 is specifically as follows:

[0020] 2.11 Divide the raw materials for quantitative sample preparation into N portions, where N>1, and the height of each portion should not exceed 1 / 2 of the sample height;

[0021] 2.12 Place the first batch of sample preparation materials evenly into the mold barrel, press it to the specified height, maintain the pressure for at least 30 minutes, and then release the pressure;

[0022] 2.13 Use the same method as step 2.12 to press the next sample on top of the prepared first sample until the N-1 sample preparation materials are pressed;

[0023] 2.14 On the prepared N-1th sample, place the raw material for the Nth sample evenly into the mold barrel, and install a hemisphere with the same size as the first inner shielding tube in the loading assembly on the pressure plate, keeping the center of the hemisphere and the upper surface of the raw material for the Nth sample at the same level, and press it to the specified height. After maintaining the pressure state for no less than 30 minutes, release the pressure to obtain a lower structure with a predetermined height and a hemispherical hole on the upper surface.

[0024] Furthermore, the loading assembly includes a detonating cord, an outer shielding tube, a protective soil core, an inner shielding tube and an explosive ball;

[0025] The protective soil core is a truncated cone structure, the density of the protective soil core is the same as the density of the sample, and the inner diameter of the inner shielding tube is larger than the outer diameter of the detonating cord;

[0026] The lower end of the protective soil core is coaxially provided with a semicircular notch that is adapted to the size of the explosive ball, the area of ​​the protective soil core above the semicircular notch is coaxially provided with a through hole that is connected to the semicircular notch, the diameter of the through hole is adapted to the outer diameter of the inner shielding tube, one end of the inner shielding tube is arranged in the through hole, and the other end is located above the sample, the outer shielding tube is sleeved on the outside of the inner shielding tube with a gap between the two, the lower end of the outer shielding tube is arranged on the protective soil core, and the upper end is located above the sample;

[0027] The upper part of the explosive ball is arranged in the semicircular notch, the lower end of the detonating cord is connected to the explosive ball, the upper end passes through the inner shielding tube and is placed above the sample, and the lower part of the explosive ball is arranged in the hemispherical hole.

[0028] Furthermore, the inner shielding tube includes a first inner shielding tube and a second inner shielding tube which are coaxially arranged and have an inner diameter larger than the detonating cord;

[0029] One end of the second inner shielding tube is disposed in the through hole, and the other end is located in the outer shielding tube. One end of the first inner shielding tube is located in the outer shielding tube and communicates with the second inner shielding tube, and the other end passes through the upper end of the outer shielding tube. The other end of the detonating cord passes through the second inner shielding tube and the first inner shielding tube in sequence and is placed above the sample.

[0030] The first inner shielding tube and the second inner shielding tube have the same diameter, and the second inner shielding tube is shorter than the first inner shielding tube.

[0031] Furthermore, step 2.2 is specifically as follows:

[0032] A. Place the particle velocimeter on the upper surface of the lower structure, keeping the central positioning hole of the particle velocimeter coaxial with the hemispherical hole;

[0033] B. Place the loading assembly at the center of the upper surface of the lower structure, make the explosive ball in the loading assembly fit well with the hemispherical hole on the lower structure, and then fix the loading assembly.

[0034] Furthermore, step 2.3 is specifically as follows:

[0035] 2.31 Divide the remaining sample preparation material into Q portions, where Q>1 and the height of each portion does not exceed 1 / 2 of the sample height;

[0036] 2.32 Place the first batch of sample preparation materials evenly into the mold cylinder, apply pressure to the upper end of the lower structure to press it to the specified height, maintain the pressure for at least 30 minutes, and then release the pressure;

[0037] 2.33 Using the same method as step 2.32, press the next sample on top of the prepared first sample until all Q samples have been pressed.

[0038] 2.34 Remove the mold cylinder and obtain the sample.

[0039] Furthermore, in step 2.1, the pressing is performed by a first pressing plate. When the first N-1 layers are pressed, the first pressing plate is a flat pressing plate. When the first N layers are pressed, the first pressing plate is a hemispherical pressing plate. The hemispherical head is located at the center of the first pressing plate and has the same size as the explosive ball.

[0040] In step 2.3, pressing is performed by a second pressing plate, wherein a through hole is provided in the middle of the second pressing plate, and the shape of the through hole is adapted to the outer shape of the loading assembly.

[0041] Compared with the prior art, the present invention has the following beneficial technical effects:

[0042] 1. Experimental measurements show that when pure fine soil is used as raw material, the density is unlikely to exceed 1.8g / cm 3 The porosity is difficult to be less than 30%. The present invention proposes a method for preparing samples for spherical wave loading test of geotechnical materials with controllable porosity and moisture content. During the sample preparation process, a mixture of fine loess and fine sand is used to prepare the sample, and the density can be easily achieved at 2.0 g / cm 3 Above, the porosity can be reduced to below 30%, thereby realizing the preparation of rock and soil samples with porosity less than 30%, and realizing the controllable porosity of loess samples.

[0043] 2. The present invention proposes a method for preparing samples for a spherical wave loading test of geotechnical materials with controllable porosity and moisture content. During the sample preparation process, a mixture of fine loess and fine sand is used to make samples. Different amounts of water are sprayed into the samples, and simulation of geotechnical samples with different moisture contents can also be achieved.

[0044] 3. In the spherical wave loading test sample preparation method for geotechnical materials with controllable porosity and moisture content proposed in the present invention, the diameter of the sand particles in the sample is less than 1 mm, which is much smaller than the stress wave pulse width (on the order of several centimeters) generated by the explosive ball in the sample. Therefore, the sample can be approximately regarded as a uniform material. That is, this method can better ensure the uniformity of the sample while reducing the porosity.

[0045] 4. The present invention proposes a sample preparation method for a spherical wave loading test on geotechnical materials with controllable porosity and moisture content. When the sample contains sand particles, the hard and angular sand particles can easily puncture the explosive ball. The prefabricated soil core protects the explosive ball, preventing the surface of the explosive ball from being punctured, thereby ensuring the safety of the sample preparation process and the stability of the explosive source performance. BRIEF DESCRIPTION OF THE DRAWINGS

[0046] Figure 1 Schematic diagram of the overall structure of an embodiment of the present invention;

[0047] Figure 2 for Figure 1 Schematic diagram of a local enlarged structure;

[0048] Reference numerals:

[0049] 1. Sample; 2. Particle velocimeter; 3. Loading assembly; 4. Explosive ball; 5. Protective soil core; 6. First inner shielding tube; 7. Second inner shielding tube; 8. Outer shielding tube; 9. Detonating cord. DETAILED DESCRIPTION

[0050] The present invention proposes a loading component for spherical wave loading test of geotechnical materials, such as Figure 1 and Figure 2 As shown, it includes a detonating cord 9, an outer shielding tube 8, a protective soil core 5, an inner shielding tube, and an explosive ball 4;

[0051] The inner shielding tube includes a first inner shielding tube 6 and a second inner shielding tube 7 made of steel. The length of the second inner shielding tube 7 is shorter than that of the first inner shielding tube 6. The density of the protective soil core 5 is the same as that of sample 1.

[0052] The protective soil core 5 is a truncated cone structure. A semicircular notch adapted to the explosive ball 4 is provided in the middle of the large diameter end. A downward through hole is coaxially provided in the middle of the small diameter end. The lower end of the through hole is tangent to the semicircular notch. The inner diameter of the through hole is adapted to the outer diameter of the second inner shielding tube 7. The lower end of the second inner shielding tube 7 is arranged in the through hole and the two are interference fit. The lower end of the second inner shielding tube 7 is flush with the lower end of the through hole. The upper end of the lower end of the second inner shielding tube 7 passes through the through hole and is arranged on the outside of the protective soil core 5. The inner shielding tube 6 is coaxially arranged at the upper end of the second inner shielding tube 7, and the outer shielding tube 8 is sleeved on the outside of the first inner shielding tube 6 and the second inner shielding tube 7, and there is a gap between the outer shielding tube 8 and the second inner shielding tube 7 and the first inner shielding tube 6. The lower end of the outer shielding tube 8 is arranged on the upper end surface of the protective soil core 5, and the explosive ball 4 is arranged in the semicircular notch. The lower end of the detonating cord 9 is connected to the explosive ball 4, and the upper end passes through the second inner shielding tube 7 and the first inner shielding tube 6 in sequence, and is placed on the outside of the first inner shielding tube 6.

[0053] The first inner shield tube 6 and the second inner shield tube 7 have the same inner diameter and outer diameter.

[0054] The inner shielding tube is divided into two sections, long and short. The short tube section is directly embedded in the protective soil core 5 when making the protective soil core 5, so that the connection between the short tube and the protective soil core 5 is more firm. If it is not divided into sections, the manufacturing difficulty of the protective soil core 5 will increase due to the longer shielding tube, and the risk of damage during the demolding process will increase.

[0055] The outer shielding tube 8 can shield the explosive load generated by the explosion of the detonating cord 9, thereby reducing interference with the test. The outer shielding tube 8 is provided with an external thread.

[0056] Based on the above-mentioned loading component 3, the present invention proposes a method for preparing samples for a spherical wave loading test of geotechnical materials with controllable porosity and moisture content. The principle is to prepare samples from a mixture of fine loess and fine sand to achieve controllable porosity of the geotechnical material samples, including the following steps:

[0057] Assume that the sample material is fine loess with a particle size of several microns, the sample diameter is 277 mm, the height is 280 mm, the mass fraction of fine river sand is 50%, and the density of loess in the sample is 1.8 g / cm 3 , the moisture content is the natural moisture content; the inner diameter of the mold barrel is 277mm, the height of the lower half of the mold is 140mm, and the height of the upper half is 250mm;

[0058] Step 1: Obtain sample preparation materials

[0059] 1.1 Based on the porosity and density of sample 1, the density requirement of the loess in the sample, and the density of the loess particles and the density of the fine sand particles in the soil-sand mixture required for sample preparation, calculate the mass fraction of the fine sand in the soil-sand mixture required for sample preparation and obtain the soil-sand ratio;

[0060] Definition: The density of loess particles is ρ 土粒 , the density of loess in sample 1 is ρ 土体 , the density of fine sand particles is ρ 砂 , the volume fraction of fine sand in sample 1 is α 砂 ,

[0061] Sand mass fraction in the sample β 砂 and the volume fraction of sand α 砂 The relationship between them is:

[0062]

[0063] The porosity η of the sample 土砂 Volume fraction of sand α 砂 The relationship between them is:

[0064]

[0065] The mass fraction β of fine sand in the soil-sand mixture required for sample preparation is obtained by the above two formulas: 砂 for;

[0066]

[0067] According to the mass fraction of fine sand raw materials β 砂 , obtain the ratio of loess and fine sand; (the porosity of sample 1 is Since 0<α 砂 <1, the porosity of sample 1 will not be greater than that of pure soil, that is, α 砂 =0).

[0068] In step 1.1, the mass fraction of sand is determined based on the density of the sand used, the density of the loess particles, the density of the loess matrix after final molding, and the desired porosity, thereby determining the configuration method of the soil-sand mixture raw materials;

[0069] 1.2 Grind the loess raw material into fine particles of a few microns and dry them to obtain fine loess; at the same time, sieve the fine sand raw material to retain fine sand particles between 30 and 160 meshes. The sand particle size at this time is less than 1 mm and much larger than the particle size of the soil particles. Evenly mix the fine loess and fine sand particles in a mass ratio of 1:1 to obtain a soil-sand mixed raw material;

[0070] 1.3 According to the moisture content requirement of sample 1, evenly spray water into the soil-sand mixed raw material in step 1.2 to obtain the sample preparation raw material;

[0071] The quality of water is Where, M is the total mass of sample 1, is the moisture content of sample 1.

[0072] Step 2: Pressing Sample 1

[0073] 2.1 Divide the soil-sand mixture of Sample 1 to be pressed into two parts. Set the height of the upper and lower structures to 140 mm. Pour the quantitative sample preparation raw materials evenly into the mold cylinder and press them to obtain a lower structure of a predetermined height. The inner surface of the mold cylinder is cylindrical, and the inner diameter is the same as the outer diameter of Sample 1.

[0074] Specifically:

[0075] 2.11 Divide the raw materials for quantitative sample preparation into two parts and press them in batches. The thickness of each layer is 70 mm, and the mass of each layer of soil-sand mixed sample is 9043 g.

[0076] 2.12 Place the first layer of sample preparation materials into the mold barrel, stir the sample preparation materials again, and initially flatten them. Place the flat first pressing plate on the sample preparation materials, start the press to press the first layer of sample preparation materials to 70mm (i.e., to the required density), and then maintain the pressure for 30 minutes. After the internal stress of the sample is uniform, close the press to release the pressure;

[0077] 2.13 Place the sample preparation materials required for the second layer into the mold barrel. Stir the sample preparation materials again until uniform and initially level them. Place a first pressing plate with a central hemispherical head on the sample preparation materials, embedding the hemispherical head into the sample preparation materials. The end surface of the first pressing plate is in contact with the sample preparation materials. Start the press to press the second layer of soil-sand mixed sample to 140 mm. Maintain pressure for 30 minutes. After the internal stress of the sample is uniform, close the press to release pressure. The diameter of the hemispherical head should be the same as the diameter of the explosive ball to be used, resulting in a lower layer structure with a predetermined height and a hemispherical hole on the upper surface.

[0078] 2.2 Place the test particle velocity meter 2 and loading assembly 3 at the center of the upper surface of the lower structure;

[0079] Specifically:

[0080] A. Place the particle velocimeter 2 on the upper surface of the lower structure so that the central positioning hole of the particle velocimeter 2 is concentric with the hemispherical hole on the lower structure;

[0081] B places the loading assembly 3 at the center of the upper surface of the lower structure, so that the explosive ball 4 in the loading assembly 3 fits well with the hemispherical hole on the lower structure, and then uses the external positioning mechanism to fix the relative position of the outer shielding tube 8 of the loading assembly 3 and the mold cylinder to prevent the outer shielding tube 8 from moving downward due to the friction between the sample preparation raw materials and the outer shielding tube 8 during the sample pressing process.

[0082] In order to prevent the fine sand particles in the sample preparation materials from easily puncturing the explosive balls, the explosive balls can be protected by prefabricated soil cores, ensuring the safety of the sample preparation process and the stability of the explosion source performance;

[0083] The outer shielding tube 8 is used to shield the explosive load generated when the detonating cord 9 explodes from affecting the test and damaging the sample;

[0084] 2.3 Evenly place the remaining sample preparation materials into the mold cylinder for pressing. After completion, remove the mold cylinder to obtain the sample-superstructure pressing;

[0085] Specifically:

[0086] 2.31 The upper structure is further divided into two layers for batch pressing. Each layer is 70 mm thick. The mass of the soil-sand mixture sample of each layer is 9037 g (after deducting the weight of the sample preparation materials corresponding to the volume occupied by the loading component 3);

[0087] 2.32 Place the sample preparation materials required for the third layer (the third layer of the sample) into the mold barrel, stir the sample preparation materials again to evenly mix them, and initially lay them flat. Place a second pressing plate with a through hole in the center on the sample preparation materials, start the press to press the third layer of soil and sand mixed sample to a total height of 210 mm, and then maintain the pressure for 30 minutes. After the internal stress of the sample is uniform, close the press to release the pressure. The through hole of the second pressing plate is compatible with the structure of the loading assembly 3 at the corresponding position (in this embodiment, it is compatible with the external structure of the outer shielding tube 8);

[0088] 2.33 Place the raw materials for the fourth layer of sample preparation into the mold barrel, stir them evenly, and initially lay them flat. Place a second pressing plate with a through hole in the center on the sample preparation materials. Start the press to press the fourth layer of soil-sand mixed sample to a total height of 280 mm. Then maintain the pressure for 30 minutes. After the internal stress of the sample is uniform, close the press to release the pressure.

[0089] 2.34 Keep the press head against the second pressing plate to ensure that the sample is not misaligned, remove the die cylinder, then lift the press head, remove the pressing plate, and complete the preparation of the spherical wave loading test sample.

[0090] In summary, the porosity of the fine loess sample can be controlled by using a mixture of fine loess and fine sand. Experimental measurements show that after 1.1% fine sand particles are mixed into the loess powder, the loess density of the pressed test sample is 1.8g / cm 3 When the porosity is reduced to 19%.

[0091] The diameter of the sand particles in the sample is less than 1 mm, which is much smaller than the stress wave pulse width generated by the explosive ball in the sample (about several centimeters). Therefore, Sample 1 can be approximately regarded as a uniform material, that is, the uniformity of the sample is better guaranteed while reducing the porosity.

[0092] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or replace some or all of the technical features therein with equivalents. However, these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the present invention.

Claims

1. A method for preparing samples for a spherical wave loading test of geotechnical materials with controllable porosity and moisture content, comprising the following steps: Step 1: Obtain sample preparation materials 1.1 Based on the porosity and density of sample (1), the density requirement of the loess body in sample (1), and the density of loess raw material particles and the density of fine sand raw material particles in the soil-sand mixed raw material required for sample preparation, calculate the mass fraction of fine sand raw material in the soil-sand mixed raw material required for sample preparation, and obtain the soil-sand ratio; 1.2 Grind the loess raw material into micron-sized fine particles and dry them to obtain fine loess; at the same time, sieve the fine sand raw material to retain fine sand particles between 30 and 160 meshes, and evenly mix the fine loess and fine sand particles according to the soil-sand ratio in step 1.1 to obtain a soil-sand mixed raw material; 1.3 According to the moisture content requirement of sample (1), evenly spray water into the soil-sand mixed raw material in step 1.2 to obtain the sample preparation raw material; Step 2: Pressing the sample (1) 2.1 Pour the quantitative sample preparation raw materials evenly into the mold cylinder and press them to obtain the lower structure of a predetermined height; 2.2 Place the test particle velocity meter (2) and the loading assembly (3) at the center of the upper surface of the lower structure; 2.3 Evenly place the remaining sample preparation raw materials into the mold cylinder at the upper end of the lower structure and press. After the pressing is completed, remove the mold cylinder to obtain the sample (1); In step 1, the mass fraction β of the fine sand raw material in the soil-sand mixed raw material required to prepare sample (1) is calculated by the following formula: 砂 ; Among them, η 土砂 is the porosity of sample (1), ρ 土砂 is the density of sample (1), ρ 土体 is the density of the loess in sample (1), ρ 砂 is the density of fine sand particles, ρ 土粒 is the density of loess particles.

2. The method for preparing samples for a spherical wave loading test of geomaterials with controllable porosity and moisture content according to claim 1, characterized in that: In step 1.3, the mass of the water is Where, M is the total mass of sample (1), is the moisture content of sample (1).

3. The method for preparing samples for a spherical wave loading test of geotechnical materials with controllable porosity and moisture content according to any one of claims 1-2, characterized in that: Step 2.1 is as follows: 2.11 Divide the raw materials for quantitative sample preparation into N portions, where N>1, and the height of each portion does not exceed 1 / 2 of the height of sample (1); 2.12 Place the first batch of sample preparation materials evenly into the mold barrel, press it to the specified height, maintain the pressure for at least 30 minutes, and then release the pressure; 2.13 Using the same method as step 2.12, press the next sample (1) on the upper end of the prepared first sample (1) until the pressing of the N-1 sample preparation raw materials is completed; 2.14 On the prepared N-1th sample (1), the raw material for the Nth sample is evenly placed in the mold barrel, and a hemisphere with the same size as the first inner shielding tube (6) in the loading component (3) is installed on the pressure plate, keeping the center of the hemisphere and the upper surface of the raw material for the Nth sample at the same level, press it to a specified height, maintain the pressure state for not less than 30 minutes, and then release the pressure to obtain a lower structure with a predetermined height having a hemispherical hole on the upper surface.

4. The method for preparing samples for a spherical wave loading test of geomaterials with controllable porosity and moisture content according to claim 3, characterized in that: The loading assembly (3) comprises a detonating cord (9), an outer shielding tube (8), a protective soil core (5), an inner shielding tube and an explosive ball (4); The protective soil core (5) is a truncated cone structure, the density of the protective soil core (5) is the same as the density of the sample (1), and the inner diameter of the inner shielding tube is larger than the outer diameter of the detonating cord (9); The lower end of the protective soil core (5) is coaxially provided with a semicircular notch that matches the size of the explosive ball (4); the area of ​​the protective soil core (5) located above the semicircular notch is coaxially provided with a through hole that is connected to the semicircular notch; the diameter of the through hole matches the outer diameter of the inner shielding tube; one end of the inner shielding tube is arranged in the through hole, and the other end is located above the sample (1); the outer shielding tube (8) is sleeved on the outside of the inner shielding tube with a gap between the two; the lower end of the outer shielding tube (8) is arranged on the protective soil core (5), and the upper end is located above the sample (1); The upper half of the explosive ball (4) is arranged in the semicircular notch, the lower end of the detonating cord (9) is connected to the explosive ball (4), the upper end of the explosive ball (9) passes through the inner shielding tube and is placed above the sample (1), and the lower half of the explosive ball (4) is arranged in the hemispherical hole.

5. The method for preparing samples for a spherical wave loading test of geomaterials with controllable porosity and moisture content according to claim 4, characterized in that: The inner shielding tube comprises a first inner shielding tube (6) and a second inner shielding tube (7) which are coaxially arranged and have an inner diameter larger than that of the detonating cord (9); One end of the second inner shielding tube (7) is arranged in the through hole, and the other end is located in the outer shielding tube (8); one end of the first inner shielding tube (6) is located in the outer shielding tube (8) and is connected to the second inner shielding tube (7), and the other end passes through the upper end of the outer shielding tube (8); the other end of the detonating cord (9) passes through the second inner shielding tube (7) and the first inner shielding tube (6) in sequence and is placed above the sample (1); The first inner shielding tube (6) and the second inner shielding tube (7) have the same diameter, and the length of the second inner shielding tube (7) is shorter than that of the first inner shielding tube (6).

6. The method for preparing samples for a spherical wave loading test of geotechnical materials with controllable porosity and moisture content according to claim 5, characterized in that: Step 2.2 is as follows: A. Place the particle velocimeter (2) on the upper surface of the lower structure, keeping the central positioning hole of the particle velocimeter (2) coaxial with the hemispherical hole; B. Place the loading assembly (3) at the center of the upper surface of the lower structure, make the explosive ball (4) in the loading assembly (3) fit well with the hemispherical hole on the lower structure, and then fix the loading assembly (3).

7. The method for preparing samples for a spherical wave loading test of geotechnical materials with controllable porosity and moisture content according to claim 6, characterized in that: Step 2.3 is as follows: 2.31 Divide the remaining sample preparation material into Q portions, where Q>1 and the height of each portion does not exceed 1 / 2 of the height of sample (1); 2.32 Place the first batch of sample preparation materials evenly into the mold barrel, apply pressure at the upper end of the lower structure to press it to the specified height, maintain the pressure for at least 30 minutes, and then release the pressure; 2.33 Using the same method as step 2.32, press the next sample (1) on top of the prepared first sample (1) until the pressing of Q sample preparation materials is completed; 2.34 Remove the mold cylinder and obtain sample (1).

8. The method for preparing samples for a spherical wave loading test of geotechnical materials with controllable porosity and moisture content according to claim 7, characterized in that: In step 2.1, the pressing is performed by a first pressing plate. When the first N-1 layers are pressed, the first pressing plate is a flat pressing plate. When the first N layers are pressed, the first pressing plate is a hemispherical pressing plate. The hemispherical head is located at the center of the first pressing plate and has the same size as the explosive ball (4). In step 2.3, pressing is performed by a second pressing plate, wherein a through hole is provided in the middle of the second pressing plate, and the shape of the through hole is adapted to the outer shape of the loading assembly (3).

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