A device and method for reducing boundary reflection effect of multi-class rock blasting physical model test

Abstract

The application provides a device and method for reducing boundary reflection effect of multi-type rock blasting physical model test, belonging to the technical field of geotechnical engineering test equipment, comprising a fixed frame, four corners of the fixed frame are fixedly connected through a combination of screws and fastening nuts and form a rectangular frame structure, a reflection suppression device is arranged close to the inner side wall of the fixed frame, and the inside of the reflection suppression device is used for limiting and placing a rock test piece. Through the synergistic effect of wave impedance gradient matching, transmission wave guiding and multi-scale energy dissipation, the boundary reflection effect of multi-type rock samples in the blasting test is significantly reduced, and the accuracy of test data is improved.

Description

Technical Field

[0001] This invention belongs to the field of rock mechanics and blasting engineering physical model testing technology, specifically a device and method for reducing boundary reflection effects in various types of rock blasting physical model tests. Background Technology

[0002] In physical model tests of rock blasting, boundary reflection is a key issue affecting the accuracy of experimental data. When the blast stress wave propagates to the model boundary, due to the difference in wave impedance between the boundary material and the rock (λ = ρ·V, where λ is wave impedance, ρ is density, and V is wave velocity), reflected waves are formed and interfere with the stress field distribution inside the sample. Studies have shown that the superposition of reflected waves alters the crack propagation path and affects the monitoring data of the dynamic response during the experiment, leading to significant errors in the experimental data that render it unusable for scientific research. Therefore, it is urgent to improve the reliability of experimental results by optimizing boundary treatment techniques.

[0003] Currently, commonly used boundary treatment methods include: the method of wrapping with absorbing materials, which absorbs some energy through material damping, but the significant difference in wave impedance between the absorbing material and the rock causes more than 30% of the stress wave to be reflected back into the sample, interfering with the crack propagation law; and the rigid boundary method (such as steel plate constraint), which can limit the displacement of the sample, but will aggravate the reflection effect, causing stress wave energy to accumulate at the boundary and triggering non-real secondary damage.

[0004] Invention patent CN116165278A uses multiple multiple Bethy wavelet basis functions to decompose and reconstruct the impact stress wave signal, weakening the influence of boundary reflections, but it does not fundamentally solve the boundary reflection problem; instead, it uses mathematical filtering methods. Invention patent CN115932949A proposes a viscoacoustic wave simulation method based on adaptive coefficient finite difference frequency domain (FDFD), which eliminates boundary reflections in numerical simulation calculations but cannot be used in actual experiments or field engineering implementation. Invention patent CN113686967A uses single-material damping to eliminate reflection effects, but its field differs from that of rock mechanics and blasting engineering physical model testing technology. The method in this patent is easily damaged or detached during explosion experiments, leading to failure. Furthermore, single-material damping cannot match the impedance range of various rocks and is highly dependent on the thickness of the boundary material, making it cumbersome and expensive to manufacture. Summary of the Invention

[0005] To address the aforementioned problems, this invention provides a device and method for reducing boundary reflection effects in physical model tests of various rock types during blasting. This device solves the problems of high reflection coefficient, slow energy decay, and poor adaptability in traditional technologies through the synergistic effects of wave impedance gradient matching, transmitted wave guidance, and multi-scale energy dissipation. It can significantly reduce the boundary reflection effects of various rock samples in blasting tests and improve the accuracy of test data.

[0006] To achieve the above-mentioned technical features, the purpose of this invention is as follows: a device for reducing boundary reflection effects in physical model tests of various types of rock blasting, comprising a fixed frame, wherein the four corners of the fixed frame are fixedly connected by a combination of screws and fastening nuts to form a rectangular frame structure.

[0007] A reflection suppression device is attached tightly to the inner wall of the fixed frame;

[0008] The interior of the reflection suppression device is used to limit and place the rock specimen.

[0009] Preferably, the fixing frame includes multiple fixing steel plates, the ends of which are bent to form folded edges, and multiple fastening holes are machined at the locations of the folded edges. The folded edges of adjacent fixing steel plates are fixedly connected by screws installed at the locations of the fastening holes.

[0010] Preferably, the reflection suppression device is a composite structure designed using wave impedance matching theory. The composite structure is made of multiple layers of materials and includes an inner plate, a middle plate and an outer plate from the inside to the outside, wherein the inner plate is in close contact with the rock specimen.

[0011] The reflection suppression device is fixed to the rock specimen by vacuum adsorption. Before installing the reflection suppression device, the rock specimen needs to be polished and wiped clean to ensure that the surface is flat and free of other impurities that may affect the installation operation.

[0012] Preferably, the specific process of using wave impedance matching theory for composite structure design is as follows:

[0013] The wave impedance of each layer of structural material decreases exponentially to avoid large changes, specifically satisfying the following:

[0014] λ=ρ·V;(1)

[0015] λ n =λ 岩石 ·e -a(n-1) (2)

[0016] In the formula, λ is the wave impedance, ρ is the density, V is the wave velocity, and λ n Let λ be the wave impedance of the nth layer material. 岩石 Let λ be the wave impedance of the target rock material, where λ varies for different rock materials.岩石 The difference lies in the fact that e is the natural constant, while a is the attenuation coefficient.

[0017] When the wave impedance changes smoothly and continuously, the reflection coefficient can approach the minimum value. Based on this, by setting an exponential decreasing law, the wave impedance transition is made smooth and abrupt changes are avoided; where the attenuation coefficient 'a' controls the impedance deceleration rate.

[0018] The method for calculating the reflection coefficient of a single-layer interface is formula (3):

[0019] A=(λ n+1 -λ n ) / (λ n+1 +λ n (3)

[0020] In the formula, A is the reflection coefficient;

[0021] Considering reflections with multilayer propagation loss:

[0022] When a wave propagates through a multilayer material, a propagation loss factor α is introduced. n , representing the attenuation of the wave in the nth layer of material; the attenuation is caused by the viscoelastic dissipation and particle scattering of the material, and is expressed as:

[0023] α n =1 / e bndn (4)

[0024] In the formula: b n Let d be the attenuation coefficient of the nth layer. n The thickness of the nth layer;

[0025] The total reflection coefficient is the result of the superposition of reflected waves from each layer:

[0026]

[0027] Preferably, the total reflection coefficient of the three layers of reflective material—inner layer (101), middle layer (102), and outer layer (103)—in the reflection suppression device (100) is:

[0028] A3=A1+(1-A1)·α1·A2·α1·(1-A1)+(1-A1)·α1·(1-A2)·α2·A3·α2·(1-A2)·α1·(1-A1); (6)

[0029] Ignoring higher-order terms, A3 in equation (6) is then simplified to:

[0030] A3≈A1+A2·(α1(1-A1)) 2 +A3·(α1α2(1-A1)(1-A2)) 2 (7)

[0031] If the total emission coefficient needs to be less than 5%, then the equation A1 + A2·(α1(1-A1)) is required. 2 +A3·(α1α2(1-A1)(1-A2)) 2 <5%, assuming a loss factor α n If the value is 0.9, then when A1 = 1.5%, A2 = 2.5%, and A3 = 1%, the total reflectance A3 = 4.07% < 5%.

[0032] Preferably, the inner layer is made of metal powder and epoxy resin composite. A certain volume of metal powder is mixed inside the epoxy resin and mixed for a period of time using a planetary mixer to ensure uniform particle distribution, and then hot pressing is used for molding.

[0033] Preferably, the middle layer is made of silicone rubber and tungsten carbide particles. It is formed by mixing a certain volume of tungsten carbide particles into the silicone rubber and using injection molding under certain injection pressure, temperature and cooling time. The middle layer dissipates energy by utilizing the particle-matrix interface friction and scattering effect during stress wave propagation, and the friction coefficient is ≥0.3.

[0034] Preferably, the outer layer is made of polyurethane foam using a foaming process; the outer layer is in the shape of a honeycomb skeleton, and a magnetorheological fluid containing carbonyl iron powder is injected into the outer honeycomb skeleton using a vacuum injection machine. Dynamic compression triggers a sharp increase in fluid viscosity, thereby achieving rapid attenuation of high-frequency waves.

[0035] Preferably, the principles of energy dissipation through scattering and viscoelastic dissipation in the middle and outer layers are as follows:

[0036] Particle scattering consumes energy, and the energy loss rate is calculated according to formula (8):

[0037] η=μ·σ n ·v·s;(8)

[0038] In the formula: η is the energy consumption ratio, μ is the friction coefficient between the microparticles and the matrix structure, and σ n σ is the normal stress, generated by the explosive load; v is the relative velocity of the particles; s is the contact area of ​​the particles, which is related to the particle size and volume ratio.

[0039] Under dynamic compression, magnetorheological fluids achieve rapid attenuation of high-frequency waves. Under the action of stress waves, the magnetorheological fluid undergoes a phase change, and its viscosity increases dramatically, converting mechanical energy into heat energy. The relationship between shear stress τ and shear rate γ˙ is given by formula (9):

[0040] τ=η(γ˙)·γ˙;(9)

[0041] Power dissipation:

[0042]

[0043] The present invention, in another aspect, provides a test method for reducing boundary reflection effects in physical model tests of various types of rock blasting. The test method employs any one of the devices described above for reducing boundary reflection effects in physical model tests of various types of rock blasting, and includes the following steps:

[0044] Step 1: Use cubic rocks of appropriate material as rock specimens, and drill blast holes in the center of the rock specimens;

[0045] Step 2: Grind the surface of the rock specimen with a diamond grinding wheel until smooth, wipe the surface with anhydrous ethanol to remove dust and oil, and let it dry.

[0046] Step 3: Based on the material of the rock specimen, a reflection suppression device with three matching layers is designed by wave impedance, and the wave impedance λ1 of the inner plate, the wave impedance λ2 of the middle plate, and the wave impedance λ3 of the outer plate are calculated.

[0047] Step 4: Based on the calculation results of Step 3, design and manufacture the reflection suppression device. First, make a casting template of the appropriate size according to the size of the rock specimen. Use a planetary mixer to mix epoxy resin and metal powder, and then use hot pressing to make the inner layer plate. Heat the mold for the middle layer plate to a certain temperature, and inject silicone rubber through injection molding. Before the material is cured, evenly sprinkle tungsten carbide particles. Use a foaming agent to foam and mold the outer layer plate. The material is polyurethane foam. After molding, use a vacuum injection machine to inject magnetorheological fluid into the outer honeycomb skeleton. After the above manufacturing is completed, place it in a room temperature environment and let it stand for a period of time.

[0048] Step 5: Make a fixed frame by bending the two ends of the square metal plate at 45° to form a fixed steel plate, and drill two fastening holes in the bent part. The length of the unbent part of the metal plate is less than the length and width of the rock specimen.

[0049] Step 6: After completing the above preparations, clean the rock specimen and place it in the test site. Use a vacuum machine to vacuum-adhere the reflection suppression device around the rock specimen, ensuring that it is tightly attached to the specimen boundary. Then, place the fixing steel plate of the fixing frame tightly against the reflection suppression device. Place the fixing frame on all four sides of the rock specimen, pass the screws through the fastening holes on the adjacent fixing steel plates, and then tighten the fastening nuts on both sides of the screws to make the fixing frame clamp the entire specimen.

[0050] Step 7: Place monitoring instruments such as strain gauges or accelerometers at the edge of the rock specimen, place explosives in the borehole and fill it with plugging material;

[0051] Step 8: After completing the above steps, connect the detonator to the detonator, evacuate personnel to a safe area, and then ignite and detonate. After detonation, record the measured strain or acceleration on the data processor. Then repeat the above test steps, but without using the reflection suppression device, and place the sensor in the same position to record the data after the explosion. Compare and analyze the effect of the reflection suppression device.

[0052] The present invention has the following beneficial effects:

[0053] 1. In this invention, the boundary reflection coefficient is reduced from 35% to 60% in the traditional method to below 5% through the continuous impedance transition of the gradient wave impedance matching layer (2.5% for granite samples and 2.3% for sandstone), which significantly improves the authenticity of the test data.

[0054] 2. By adjusting the proportion of metal powder (aluminum powder, iron powder) and the porosity gradient, this invention can be adapted to various rock wave impedance ranges, achieving universal applicability.

[0055] 3. This invention effectively controls the reflection effect at the boundary of the rock specimen during the explosion test by means of impedance gradient matching, transmission wave guidance and multi-scale energy dissipation synergistic effect, thereby reducing the influence of reflected waves in the test.

[0056] 4. The device of the present invention is compatible with various rock materials and rock specimen shapes, and the device can be quickly assembled, supporting laboratory and field tests. Attached Figure Description

[0057] The present invention will be further described below with reference to the accompanying drawings and embodiments.

[0058] Figure 1 This is a layout diagram for a specific embodiment of the present invention.

[0059] Figure 2 This is a structural diagram of the reflection suppression device of the present invention.

[0060] Figure 3 This is a diagram showing the details of the fixing frame and the fastening method of the present invention.

[0061] Figure 4 This is a diagram illustrating the effect of strain monitoring with and without the reflection suppression device of the present invention.

[0062] Figure 5 This is a diagram illustrating the effect of blasting a granite specimen with or without the reflection suppression device of the present invention.

[0063] In the diagram: 100 - Reflection suppression device, 101 - Inner plate, 102 - Middle plate, 103 - Outer plate, 200 - Rock specimen, 300 - Fixing frame, 301 - Fixing steel plate, 302 - Fastening hole, 400 - Screw, 500 - Fastening nut. Detailed Implementation

[0064] The embodiments of the present invention will be further described below with reference to the accompanying drawings.

[0065] Example 1:

[0066] Reference Figure 1-3 This invention provides a device for reducing boundary reflection effects in physical model tests of various types of rock blasting. The device includes a fixed frame 300, whose four corners are fixedly connected by screws 400 and fastening nuts 500 to form a rectangular frame structure. A reflection suppression device 100 is tightly attached to the inner wall of the fixed frame 300. The interior of the reflection suppression device 100 is used to limit and hold the rock specimen 200. Through this device, by the synergistic effect of gradient wave impedance matching and multi-level energy dissipation, and through the boundary treatment device that combines wave impedance gradient matching, transmitted wave guidance, and multi-scale energy dissipation, the boundary reflection effect of various types of rock specimens in blasting tests can be significantly reduced, improving the accuracy of the test data.

[0067] Furthermore, the fixing frame 300 includes multiple fixing steel plates 301. The ends of the fixing steel plates 301 are bent to form flanges, and multiple fastening holes 302 are machined at the locations of the flanges. The flanges of adjacent fixing steel plates 301 are fixedly connected by screws 400 installed at the locations of the fastening holes 302. The fixing frame 300 described above can be used to limit the position of the reflection suppression device 100.

[0068] Furthermore, the reflection suppression device 100 is a composite structure designed using wave impedance matching theory. This composite structure is made of multiple layers of materials, comprising, from the inside out, an inner plate 101, a middle plate 102, and an outer plate 103, wherein the inner plate 101 is in close contact with the rock specimen 200. This multi-layered composite structure enables the synergistic effects of wave impedance gradient matching, transmitted wave guidance, and multi-scale energy dissipation.

[0069] Furthermore, the reflection suppression device 100 is vacuum-adhesively fixed to the rock specimen 200. Before installing the reflection suppression device 100, the rock specimen 200 needs to be polished and wiped clean to ensure a smooth surface free of impurities that could affect the installation. This fixing and installation method effectively improves the accuracy of subsequent test data.

[0070] Furthermore, the specific process of using wave impedance matching theory for composite structure design is as follows:

[0071] The wave impedance of each layer of structural material decreases exponentially to avoid large changes, specifically satisfying the following:

[0072] λ=ρ·V;(1)

[0073] λ n =λ 岩石 ·e -a(n-1) (2)

[0074] In the formula, λ is the wave impedance, ρ is the density, V is the wave velocity, and λ n Let λ be the wave impedance of the nth layer material. 岩石 Let λ be the wave impedance of the target rock material, where λ varies for different rock materials. 岩石 The difference lies in the natural constant e and the attenuation coefficient a; a = 0.1 to 0.3, n = 1, 2, 3...

[0075] When the wave impedance changes smoothly and continuously, the reflection coefficient can approach the minimum value. Based on this, by setting an exponential decreasing law, the wave impedance transition is made smooth and abrupt changes are avoided; where the attenuation coefficient 'a' controls the impedance deceleration rate.

[0076] The method for calculating the reflection coefficient of a single-layer interface is formula (3):

[0077] A=(λ n+1 -λ n ) / (λ n+1 +λ n (3)

[0078] In the formula, A is the reflection coefficient;

[0079] Considering reflections with multilayer propagation loss:

[0080] When a wave propagates through a multilayer material, a propagation loss factor α is introduced. n , representing the attenuation of the wave in the nth layer of material; the attenuation is caused by the viscoelastic dissipation and particle scattering of the material, and is expressed as:

[0081] α n =1 / e bndn (4)

[0082] In the formula: b n Let d be the attenuation coefficient of the nth layer. n The thickness of the nth layer;

[0083] The total reflection coefficient is the result of the superposition of reflected waves from each layer:

[0084]

[0085] Furthermore, the total reflection coefficient of the three layers of reflective materials—inner layer 101, middle layer 102, and outer layer 103—in the reflection suppression device 100 is:

[0086] A3=A1+(1-A1)·α1·A2·α1·(1-A1)+(1-A1)·α1·(1-A2)·α2·A3·α2·(1-A2)·α1·(1-A1); (6)

[0087] Ignoring higher-order terms, A3 in equation (6) is then simplified to:

[0088] A3≈A1+A2·(α1(1-A1)) 2 +A3·(α1α2(1-A1)(1-A2)) 2 (7)

[0089] If the total emission coefficient needs to be less than 5%, then the equation A1 + A2·(α1(1-A1)) is required. 2 +A3·(α1α2(1-A1)(1-A2)) 2 <5%, assuming a loss factor α n If the value is 0.9, then when A1 = 1.5%, A2 = 2.5%, and A3 = 1%, the total reflectance A3 = 4.07% < 5%.

[0090] Furthermore, the inner layer plate 101 is made of metal powder and epoxy resin composite. A certain volume of metal powder is mixed inside the epoxy resin and mixed for a period of time using a planetary mixer to ensure uniform particle distribution, and then hot pressing is used for molding.

[0091] Preferably, the metal powder is aluminum or tungsten. In this embodiment, aluminum powder is composited with epoxy resin, and the epoxy resin has a density of 1.2 g / cm³. 3 A certain volume of aluminum powder with a particle size of 50 μm and a density of 2.7 g / cm³ was mixed in. 3 A planetary mixer is used at 200 rpm for 30 minutes to ensure uniform particle distribution; hot pressing is performed at 10 MPa, 120℃, and 30 minutes to achieve a thickness of 10 mm.

[0092] Furthermore, the middle layer 102 is made of silicone rubber and tungsten carbide particles. By mixing a certain volume of tungsten carbide particles into the silicone rubber, it is formed by injection molding under certain injection pressure, temperature and cooling time. The middle layer 102 dissipates energy by utilizing the particle-matrix interface friction and scattering effect during stress wave propagation, and the friction coefficient is ≥0.3.

[0093] Preferably, in this embodiment, the middle layer material is a silicone rubber-tungsten carbide particle composite, with the silicone rubber having a density of 1.1 g / cm³. 3 A certain volume of tungsten carbide particles with a particle size of 0.5 mm and a density of 15.6 g / cm³ were mixed in. 3Manufactured using injection molding, with an injection pressure of 80 MPa, a mold temperature of 60°C, and a cooling time of 5 minutes. The elastic modulus ratio is tungsten carbide:silicone rubber = 150:1, ensuring maximum interfacial friction. Energy is dissipated by particle-matrix interfacial friction and scattering effects during stress wave propagation, resulting in a friction coefficient ≥ 0.3.

[0094] Furthermore, the outer layer 103 is made of polyurethane foam using a foaming process; the outer layer 103 is in the shape of a honeycomb skeleton, and a magnetorheological fluid containing carbonyl iron powder is injected into the outer honeycomb skeleton using a vacuum injection machine. Dynamic compression triggers a sharp increase in fluid viscosity, thereby achieving rapid attenuation of high-frequency waves.

[0095] Preferably, in this embodiment, the outer layer material is polyurethane foam with a porosity of 40% and a density of 0.48 g / cm³. 3 It is manufactured using a foaming process with a foaming agent content of 5%, a foaming time of 10 minutes, and a thickness of 15mm. The outer layer structure is a honeycomb skeleton, into which a magnetorheological fluid containing carbonyl iron powder is injected using a vacuum injection machine. Dynamic compression triggers a sharp increase in fluid viscosity, achieving rapid attenuation of high-frequency waves.

[0096] Furthermore, the principles of energy dissipation through scattering and viscoelastic dissipation in the middle layer plate 102 and the outer layer plate 103 are as follows:

[0097] Particle scattering consumes energy, and the energy loss rate is calculated according to formula (8):

[0098] η=μ·σ n ·v·s;(8)

[0099] In the formula: η is the energy consumption ratio, μ is the friction coefficient between the microparticles and the matrix structure, and σ n σ is the normal stress, generated by the explosive load; v is the relative velocity of the particles; s is the contact area of ​​the particles, which is related to the particle size and volume ratio.

[0100] Under dynamic compression, magnetorheological fluids achieve rapid attenuation of high-frequency waves. Under the action of stress waves, the magnetorheological fluid undergoes a phase change, and its viscosity increases dramatically, converting mechanical energy into heat energy. The relationship between shear stress τ and shear rate γ˙ is given by formula (9):

[0101] τ=η(γ˙)·γ˙;(9)

[0102] Power dissipation:

[0103]

[0104] Preferably, the reflection suppression device can be modified in size and number of composite material layers according to different rock types and size requirements. The composition of the composite material ensures that its wave impedance satisfies A in formulas (2) and (5). 总The requirement is <5%.

[0105] Example 2:

[0106] The present invention, in another aspect, provides a test method for reducing boundary reflection effects in physical model tests of various types of rock blasting. The test method employs any one of the devices described above for reducing boundary reflection effects in physical model tests of various types of rock blasting, and includes the following steps:

[0107] Step 1: Use a cubic rock of appropriate material as rock specimen 200, and drill a blast hole in the center of rock specimen 200;

[0108] Step 2: Grind the surface of the rock specimen 200 with a diamond grinding wheel until smooth, wipe the surface with anhydrous ethanol to remove dust and oil, and let it dry.

[0109] Step 3: For the material of rock specimen 200, a reflection suppression device 100 with three matching layers is designed by wave impedance, and the wave impedance λ1 of the inner plate 101, the wave impedance λ2 of the middle plate 102, and the wave impedance λ3 of the outer plate 103 are calculated.

[0110] Step 4: Based on the calculation results of Step 3, design and manufacture the reflection suppression device 100. First, make a casting template of the appropriate size according to the size of the rock specimen 200. Use a planetary mixer to mix epoxy resin and metal powder, and then use hot pressing to form the inner layer plate 101. Heat the mold for the middle layer plate 102 to a certain temperature, and inject silicone rubber through injection molding. Before the material is cured, evenly sprinkle tungsten carbide particles. Use a foaming agent to foam and form the outer layer plate 103. The material is polyurethane foam. After molding, use a vacuum injection machine to inject magnetorheological fluid into the outer honeycomb skeleton. After the above manufacturing is completed, place it in a room temperature environment and let it stand for a period of time.

[0111] Step 5: Make a fixed frame 300 by bending the two ends of the square metal plate at 45° to form a fixed steel plate 301, and drill two fastening holes 302 in the bent part. The length of the unbent part of the metal plate is less than the length and width of the rock specimen 200.

[0112] Step 6: After completing the above preparations, clean the rock specimen 200 and place it in the test site. Use a vacuum machine to vacuum-adhere the reflection suppression device 100 around the rock specimen 200, ensuring that it is tightly attached to the specimen boundary. Then, place the fixing steel plate 301 of the fixing frame 300 tightly against the reflection suppression device 100. Place the fixing frame 300 on all four sides of the rock specimen. Pass the screw 400 through the fastening hole 302 on the adjacent fixing steel plate 301, and then tighten the fastening nut on both sides of the screw 400 to make the fixing frame 300 clamp the entire specimen.

[0113] Step 7: Place monitoring instruments such as strain gauges or accelerometers at the edge of the rock specimen, place explosives in the borehole and fill it with plugging material;

[0114] Step 8: After completing the above steps, connect the detonator to the detonator, evacuate personnel to a safe area, and then ignite and detonate. After detonation, record the measured strain or acceleration on the data processor. Then repeat the above test steps, but without using the reflection suppression device 100, and place the sensor in the same position to record the data after the explosion. Compare and analyze the effect of having and not having the reflection suppression device 100.

[0115] Example 3:

[0116] The following is in conjunction with the embodiments and appendices Figure 1-5 The technical solution of the present invention will be described in detail. This embodiment takes a single-hole blasting test of granite as an example, but it does not constitute a limitation on the scope of protection of the present invention.

[0117] Step 1: Using a 200mm×200mm×200mm cubic granite specimen (200), drill a 10mm diameter, 100mm deep borehole in the center. Figure 1 As shown.

[0118] Step 2: Grind the sample surface with a diamond grinding wheel until smooth, wipe the surface with anhydrous ethanol to remove dust and oil, and let it stand to dry for 30 minutes.

[0119] Step 3, as follows Figure 2 As shown, a reflection suppression device 100 with three matching layers is designed for the wave impedance of granite, based on the typical wave impedance of granite being λ. 岩石 =15×10 6 kg / (m 2 The wave impedance λ1 of the inner plate 101 was calculated to be 14.25 × 10⁻⁶. 6 kg / (m 2 s), the wave impedance of the middle layer plate 102 is λ2=10.5×10 6 kg / (m 2 s), the wave impedance of the outer layer 103 is λ3 = 5 × 10 6 kg / (m 2 s).

[0120] Step 4: Based on the above design, fabricate the reflection suppression device 100. First, make a casting template of the appropriate size according to the dimensions of the granite. Use a planetary mixer to mix epoxy resin with a density of 1.2 g / cm³. 3 It contains 45% volumetric aluminum powder, with a particle size of 50 μm and a density of 2.7 g / cm³. 3The mixture is stirred for 30 minutes, and then the inner layer 101 is formed by hot pressing. The mold for the middle layer 102 is heated to 60°C, and silicone rubber with a density of 1.1 g / cm³ is injected through injection molding. 3 Before the material hardens, tungsten carbide particles with a diameter of 0.5 mm and a density of 15.6 g / cm³ are evenly sprinkled on top. 3 The outer layer 103, comprising 30% of the volume, is made of polyurethane foam with a porosity of 40% and a density of 0.48 g / cm³, produced by foaming with 5% foaming agent. 3 After molding, a mixture of magnetorheological fluid and carbonyl iron powder (40% by volume) with silicone oil is injected into the outer honeycomb skeleton using a vacuum injection molding machine. After the above fabrication is completed, it is left to stand at room temperature for 24 hours.

[0121] Step 5, as follows Figure 3 As shown, a fixed frame 300 is made by bending the two ends of a square metal plate at 45° to form a fixed steel plate 301, and drilling two fastening holes 302 in the bent part. The length of the unbent part of the metal plate is slightly smaller than the length and width of the granite specimen 200.

[0122] Step 6: After completing the preparations in the above steps, clean the granite specimen 200 and place it in the test site. Use a vacuum machine to vacuum-adhere the reflection suppression device 100 around the granite specimen 200, ensuring it is tightly attached to the specimen boundary. Then, place the fixing steel plate 301 of the fixing frame 300 tightly against the reflection suppression device 100. Place the fixing frame 300 on all four sides of the rock specimen. Pass the screws 400 through the fastening holes 302 on the adjacent fixing steel plates 301, and then tighten the fastening nuts on both sides of the screws 400 to clamp the entire specimen with the fixing frame 300.

[0123] Step 7: Place monitoring instruments such as strain gauges or accelerometers at the edge of the rock specimen, place explosives in the borehole and fill it with plugging material.

[0124] Step 8: After completing the above steps, connect the detonator to the trigger and evacuate personnel to a safe area. Then, ignite and detonate. After detonation, record the measured strain or acceleration on the data processor. Repeat the above test steps, but without the reflection suppression device 100, and place sensors in the same locations to record the data after the explosion. Compare and analyze the effects of having and not having the reflection suppression device 100.

[0125] Comparison of effects in examples:

[0126] from Figure 4 It can be observed that without the reflection suppression device, significant reflection is visible on the strain monitor, with a reflectivity of 39.7%; however, with the reflection suppression device in place, the reflection phenomenon almost disappears, and the reflectivity is only 2.5%. Figure 5 The results of the granite blasting test show that without the reflection suppression device, obvious reflection cracks appear around the granite specimen; however, with the reflection suppression device, no reflection cracks appear around the granite specimen. This indicates that the device is effective, and the method of this invention can effectively suppress reflection.

[0127] The specific embodiments of the present invention have been described in detail above, but these are merely one example, and the present invention is not limited to the specific embodiments described above. For those skilled in the art, any equivalent modifications and substitutions to the present invention are also within the scope of the present invention. Therefore, all equivalent changes and modifications made without departing from the spirit and scope of the present invention should be covered within the scope of the present invention.

Claims

1. A device for reducing boundary reflection effects in physical model tests of various types of rock blasting, characterized in that, The system includes a fixed frame (300), the four corners of which are fixedly connected by screws (400) and fastening nuts (500) to form a rectangular frame structure; a reflection suppression device (100) is tightly attached to the inner wall of the fixed frame (300); the interior of the reflection suppression device (100) is used to limit the placement of the rock specimen (200); the reflection suppression device (100) is a composite structure designed using wave impedance matching theory, and the composite structure is made of multiple layers of materials, including an inner layer plate (101), a middle layer plate (102) and an outer layer plate (103) from the inside to the outside, wherein the inner layer plate (101) is tightly attached to the rock specimen (200); the inner layer plate (101) is made of metal powder and epoxy resin composite; the middle layer plate (102) is made of silicone rubber and tungsten carbide particles composite; and the outer layer plate (103) is made of polyurethane foam using a foaming process.

2. The device for reducing boundary reflection effects in physical model tests of various types of rock blasting according to claim 1, characterized in that, The fixed frame (300) includes multiple fixed steel plates (301). The ends of the fixed steel plates (301) are bent to form folded edges. Multiple fastening holes (302) are machined at the locations of the folded edges. The folded edges of adjacent fixed steel plates (301) are fixedly connected by screws (400) installed at the locations of the fastening holes (302).

3. The device for reducing boundary reflection effects in physical model tests of various types of rock blasting according to claim 2, characterized in that, The reflection suppression device (100) and the rock specimen (200) are fixed together by vacuum adsorption. Before installing the reflection suppression device (100), the rock specimen (200) needs to be polished and wiped clean to ensure that the surface is flat and free of other impurities that may affect the installation operation.

4. The device for reducing boundary reflection effects in physical model tests of various types of rock blasting according to claim 3, characterized in that, The specific process of using wave impedance matching theory for composite structure design is as follows: The wave impedance of each layer of structural material decreases exponentially to avoid large changes, specifically satisfying the following: In the formula, λ For wave impedance, ρ For density, V For wave speed, λ n For the first n Layer material wave impedance, λ 岩石 The target rock material is the wave impedance, where different rock materials... λ 岩石 different, e Natural constant, a The attenuation coefficient; When the wave impedance changes smoothly and continuously, the reflection coefficient approaches its minimum value. Based on this, by setting an exponentially decreasing law, the wave impedance transition is made smooth, avoiding abrupt changes; among which, the attenuation coefficient... a Controlled impedance deceleration rate; The method for calculating the reflection coefficient of a single-layer interface is formula (3): A =( λ n+1 λ n ) / ( λ n+1 + λ n )；（3） In the formula, A The reflection coefficient; Considering reflections with multilayer propagation loss: When a wave propagates through a multilayer material, a propagation loss factor is introduced. α n , indicating that the wave is in the 1st n Attenuation in layered materials; attenuation is caused by viscoelastic dissipation and particle scattering of the material, and is expressed as: α n =1 / e bndn ；（4） In the formula: b n For the first n The attenuation coefficient of the layer, d n For the first n Layer thickness; The total reflection coefficient is the result of the superposition of reflected waves from each layer: 。 5. The device for reducing boundary reflection effects in physical model tests of various types of rock blasting according to claim 4, characterized in that, The total reflection coefficient of the three layers of reflective material in the reflection suppression device (100), namely the inner layer plate (101), the middle layer plate (102), and the outer layer plate (103), is: Ignoring higher-order terms, then, in equation (6) A 3, after simplification, becomes: If the total emission coefficient needs to be less than 5%, then the equation is required. A 1+ A 2 ( α 1(1 A 1)) 2 + A 3 ( α 1 α 2(1 A 1)(1 A 2)) 2 < 5%, assuming loss factor α n If it is 0.9, then when A 1 = 1.5%, A 2 = 2.5%, A When 3=1%, the total reflectance can be made to... A 3 = 4.07% < 5%.

6. The device for reducing boundary reflection effects in physical model tests of various types of rock blasting according to claim 5, characterized in that, The inner layer plate (101) is formed by mixing a certain volume of metal powder inside epoxy resin, mixing it for a period of time using a planetary mixer to ensure uniform particle distribution, and then hot pressing.

7. The device for reducing boundary reflection effects in physical model tests of various types of rock blasting according to claim 6, characterized in that, The middle layer (102) is formed by mixing a certain volume of tungsten carbide particles in silicone rubber and using injection molding process under certain injection pressure, temperature and cooling time. The middle layer (102) dissipates energy by utilizing the particle-matrix interface friction and scattering effect during stress wave propagation, and the friction coefficient is ≥0.

3.

8. The device for reducing boundary reflection effects in physical model tests of various types of rock blasting according to claim 7, characterized in that, The outer layer plate (103) is a honeycomb skeleton. A magnetorheological fluid containing carbonyl iron powder is injected into the outer honeycomb skeleton using a vacuum injection machine. Dynamic compression triggers a sharp increase in fluid viscosity, thereby achieving rapid attenuation of high-frequency waves.

9. The device for reducing boundary reflection effects in physical model tests of various types of rock blasting according to claim 8, characterized in that, The principles of energy dissipation through scattering and viscoelastic dissipation in the middle layer (102) and outer layer (103) are as follows: Particle scattering consumes energy, and the energy loss rate is calculated according to formula (8): In the formula: η Energy consumption ratio μ The coefficient of friction between the microparticles and the matrix structure. σ n This is the normal stress, generated by the explosive load. v The relative velocity of the particles. s This represents the particle contact area, which is related to particle size and volume fraction. Under dynamic compression, magnetorheological fluids achieve rapid attenuation of high-frequency waves. Under stress waves, the fluid undergoes a phase transition, resulting in a dramatic increase in viscosity, converting mechanical energy into heat energy, and mitigating shear stress. τ With shear rate The relationship is given by formula (9): Power dissipation: 。 10. A test method for reducing boundary reflection effects in physical model tests of various types of rock blasting, characterized in that, The experimental method is implemented using the device for reducing boundary reflection effects in physical model tests of various types of rock blasting as described in any one of claims 3-9, and includes the following steps: Step 1: Use a cubic rock of appropriate material as a rock specimen (200), and drill a blast hole in the center of the rock specimen (200); Step 2: Grind the surface of the rock specimen (200) with a diamond grinding wheel until smooth, wipe the surface with anhydrous ethanol to remove dust and oil, and let it dry. Step 3: For the material of the rock specimen (200), a reflection suppression device (100) with a three-layer matching layer is designed based on wave impedance, and the wave impedance of the inner plate (101) is calculated. λ 1. The wave impedance of the middle layer plate (102) is λ 2. Wave impedance of outer plate (103) λ 3; Step 4: Design and manufacture a reflection suppression device (100) based on the calculation results of Step 3. First, make a casting template of the appropriate size according to the size of the rock specimen (200). Use a planetary mixer to mix epoxy resin and metal powder. Then, use hot pressing to make the inner layer plate (101). Heat the mold of the middle layer plate (102) to a certain temperature. Inject silicone rubber through injection molding. Before the material is cured, evenly sprinkle tungsten carbide particles. Use a foaming agent to foam and mold the outer layer plate (103). The material is polyurethane foam. After molding, use a vacuum injection machine to inject magnetorheological fluid into the outer honeycomb skeleton. After the above is completed, place it in a room temperature environment and let it stand for a period of time. Step 5, make a fixed frame (300), bend the two ends of the square metal plate at 45° to form a fixed steel plate (301), and drill two fastening holes (302) in the bent part. The length of the unbent part of the metal plate is less than the length and width of the rock specimen (200). Step 6: After completing the above preparations, clean the rock specimen (200) and place it in the test site. Use a vacuum machine to vacuum-adsorb the reflection suppression device (100) around the rock specimen (200) to ensure that it is close to the specimen boundary. Then, place the fixing steel plate (301) of the fixing frame (300) close to the reflection suppression device (100). Place the fixing frame (300) on all four sides of the rock specimen. Pass the screw (400) through the fastening hole (302) on the adjacent fixing steel plate (301). Then, tighten the fastening nut on both sides of the screw (400) to make the fixing frame (300) clamp the entire specimen. Step 7: Place monitoring instruments such as strain gauges or accelerometers at the edge of the rock specimen, place explosives in the borehole and fill it with plugging material; Step 8: After completing the above steps, connect the detonator to the detonator, evacuate personnel to a safe area, and then ignite and detonate. After detonation, record the measured strain or acceleration on the data processor. Then repeat the above test steps, but without using the reflection suppression device (100), and place the sensor in the same position to record the data after the explosion. Compare and analyze the effect of having and not having the reflection suppression device (100).

Images