Device and method for testing peak stress at rock mass fracture during blasting

Abstract

The application discloses a device and a method for testing peak stress of rock mass at a broken area during blasting, and the device comprises a rock test piece, a blast hole and a test assembly, the blast hole is located at the center of the rock test piece, the test assembly is located in the rock broken area and comprises a horizontal plane test unit for bearing stress generated by horizontal plane blasting and a central vertical plane test unit for bearing stress generated by vertical plane blasting, the horizontal plane test unit is located in the radial direction of the blast hole, the central vertical plane test unit is located directly below the axis of the blast hole, the horizontal plane test unit and the central vertical plane test unit are both provided with a plurality of test points, and a circular ring test piece is arranged at each test point. The application tests the strain of the thin circular ring caused by the explosion stress through the horizontal plane test unit and the central vertical plane test unit, so as to obtain the peak stress of the position of the thin circular ring, and further obtain the peak stress of the rock broken area under the current explosive quantity and the attenuation of the explosion stress.

Description

Technical Field

[0001] The invention relates to the field of rock mass blasting strain measurement technology, specifically to a device and method for testing the peak stress at the fracture point of rock mass during blasting. Background Technology

[0002] When explosives detonate rock masses, the near-field zone experiences a strong unloading effect due to the loosening of the rock mass caused by the shock wave. In the fractured rock zone, the propagation of stress waves causes the intense stress to exceed the rock's bearing capacity, leading to damage. Simultaneously, it disturbs weak structural surfaces, which may undergo shear slip under strong seismic disturbances. Therefore, by measuring the maximum stress generated during a quantitative explosive blast and the attenuation of the explosive stress, appropriate protective measures can be taken to prevent damage to the surrounding rock mass and the project during construction, thereby improving the safety and efficiency of blasting operations.

[0003] In a prior art horizontal layered rock mass explosion stress wave propagation test structure (CN206696443U), the explosion stress test uses sensors placed on the rock mass to measure the stress experienced by the rock mass. Multiple sensors are arranged at equal intervals to conduct the test and obtain the stress wave propagation attenuation. However, this method uses multiple sensors, which is costly, and the stress experienced by the rock after it is broken is greatly reduced, making it impossible to accurately measure the maximum stress generated during the explosion.

[0004] In view of the above, it is necessary to study a device and method for testing the peak stress at the fracture point of rock mass during blasting in order to solve the above-mentioned technical problems. Summary of the Invention

[0005] The purpose of this invention is to provide a device and method for testing the peak stress at the fracture point of rock mass during blasting, so as to solve the problem mentioned in the background art that the maximum stress generated during blasting cannot be accurately measured.

[0006] To achieve the above objectives, the invention provides the following technical solution:

[0007] An apparatus for testing the peak stress at the fracture point of rock mass during blasting, comprising:

[0008] Rock specimens, formed by concrete casting, are used to simulate rocks. The appropriate concrete mix ratio can be selected based on the strength of the rock.

[0009] The blasting assembly, located at the center of the rock specimen, is used to blast the rock specimen, forming a rock fracture zone (which includes a crushing zone and a fracturing zone) after the rock specimen is blasted. The blasting assembly includes a borehole and an explosive charge filled in the borehole. During the test experiment, the explosive charge is detonated by an electronic detonator.

[0010] The testing assembly, located within the rock fracture zone (including the crushing zone and the fracturing zone), is used to test the explosive stress and stress attenuation on the horizontal and central vertical planes within the rock fracture zone (including the crushing zone and the fracturing zone). The testing assembly includes a horizontal plane testing unit for withstanding horizontal explosive stress and a central vertical plane testing unit for withstanding vertical explosive stress. The horizontal plane testing unit has at least four sets, each located radially from the explosive assembly. The central vertical plane testing unit is located directly below the explosive assembly. Both the horizontal plane testing unit and the central vertical plane testing unit have multiple testing points, with each testing point corresponding to a circular test piece.

[0011] As a further improvement of the present invention, the circular test piece includes a thin circular ring, a strain gauge, and a cover plate. The thin circular ring has a through hole at its center, and a strain gauge is applied to the inner wall of the through hole. The strain gauge is used to sense the deformation state of the thin circular ring under the blasting pressure after the blasting component is activated. Cover plates are provided at both ends of the thin circular ring to prevent concrete from entering during pouring.

[0012] As a further improvement of the present invention, the test assembly also includes a dynamic strain gauge for receiving strain gauge deformation state data, and each strain gauge is connected to the dynamic strain gauge via a wire.

[0013] As a further improvement of the present invention, the area of ​​the strain gauge occupies half of the area of ​​the through hole and is located close to the position of the drug pack.

[0014] As a further improvement of the present invention, an explosion-proof baffle is provided on one side of the rock specimen, and the dynamic strain gauge is located behind the explosion-proof baffle and on the side away from the rock specimen. The explosion-proof baffle is used to withstand the shock wave generated by the blast and any flying rocks that may occur, protecting the instrument and the personal safety of the operators.

[0015] As a further improvement of the present invention, the thin ring only deforms without being destroyed after being subjected to explosive stress, and the elastic modulus of the material of the thin ring is 17-206 GPa.

[0016] A method for testing the peak stress at the fractured rock mass during blasting, using the aforementioned apparatus for testing the peak stress at the fractured rock mass during blasting, comprises the following steps:

[0017] S1. Determine the explosive equivalent, estimate the maximum explosive stress value that the explosive charge may generate, and select the material corresponding to the elastic modulus of the thin ring of the horizontal plane test unit and the central vertical plane test unit according to the estimated maximum explosive stress value.

[0018] S2. Attach the strain gauge to the inner wall of the thin ring and bring it close to the explosive charge, ensuring that the strain gauge's compressive area occupies half of the inner wall area of ​​the thin ring. After the strain gauge is attached, attach the cover plate to both ends of the thin ring and place the strain gauge's lead wire between the thin ring and the cover plate. This completes the assembly of the ring test piece. Repeat this process to make multiple pieces for later use.

[0019] S3. At the center of the rock specimen, multiple circular test pieces corresponding to the central vertical plane test unit are buried at equal intervals in the vertical direction passing through the center of the explosive pack. Multiple circular test pieces corresponding to the horizontal plane test unit are buried at equal intervals in at least four directions around the same horizontal plane of the explosive pack, and the circular test pieces in each direction are in the same straight line with the explosive pack. Connect the wires corresponding to all strain gauges to the dynamic strain gauge respectively.

[0020] S4. Install an explosion-proof baffle on one side of the rock specimen and fill the borehole with explosive charges;

[0021] S5. Detonate the explosive charge to start the blasting, record the strain data of the dynamic strain gauge, and according to the strain curve, take the maximum strain value and substitute it into the circular ring stress-strain relationship formula to obtain the peak explosive stress at each thin ring position; according to the distribution of peak explosive stress at each thin ring position, obtain the attenuation of explosive stress.

[0022] As a further improvement of the present invention, the method for selecting the material of the thin ring with a suitable elastic modulus for the horizontal plane test unit in step S1 is as follows: Based on the estimated maximum explosion stress of the explosive charge, the material of the thin ring is initially selected, and steps S2-S5 are performed to obtain the peak explosion stress value corresponding to each test point. Thin ring test points with a peak strain value less than 500 are selected (in this case, the material's elastic modulus is too large, resulting in a smaller and less accurate strain value). All thin ring materials in the same ring ring ring are replaced, ensuring consistency. The elastic modulus of the replaced thin ring material must be less than that of the initially selected thin ring material. The experiment is repeated until the strain values ​​of all thin ring peaks are greater than 500. When the strain values ​​of the tested peaks are all greater than 500... When the appropriate elastic modulus of each ring in the horizontal plane test unit is obtained, the material selection method for the appropriate elastic modulus of the thin ring in the central vertical plane test unit is as follows: based on the estimated maximum explosion stress of the explosive charge, the material of the thin ring is initially selected and steps S2-S5 are performed to obtain the peak explosion stress value corresponding to each test point. The test point of the thin ring with a peak strain value of less than 500 is selected, and the material of the thin ring at the test point where the peak strain value is less than 500 is replaced. The elastic modulus of the replaced thin ring material must be less than the elastic modulus of the initially selected thin ring material. The experiment is repeated until the strain value of all thin ring peaks is greater than 500. When the strain value of the tested peaks is greater than 500, the appropriate elastic modulus of the thin ring at each point in the central vertical plane test unit is obtained. Thin rings can be tested with different materials. Thin rings made of materials with smaller elastic modulus will experience greater strain and higher precision. At the same time, when selecting thin rings made of materials with smaller elastic modulus, it is necessary to ensure that the thin rings will not be damaged by excessive explosive stress.

[0023] As a further improvement of the present invention, the stress-strain relationship formula of the annulus in step S4 is as follows:

[0024]

[0025] In the formula: E is the elastic modulus of the thin ring, ε is the strain value of the inner wall of the ring, l1 is the outer radius of the ring, and l2 is the inner radius of the ring.

[0026] The thin ring has a simple structure and its mechanical property formula is easy to derive. By measuring the deformation of the inner wall of the thin ring with strain gauges, the maximum strain value can be substituted into the derived formula to calculate the maximum stress on the outer wall of the thin ring, which is the peak explosive stress at the location of the thin ring. The data can also be sorted to obtain the attenuation of the explosive stress.

[0027] Compared with existing technologies, the beneficial effects of the invention are:

[0028] 1. This invention uses a horizontal plane test unit and a central vertical plane test unit to test the strain of a thin ring caused by the shock wave during the blasting of a rock specimen, thereby deriving the stress on the inner ring. Based on the performance analysis of the ring, the stress on the outside of the ring is then derived, i.e., the peak explosive stress at the location of the thin ring. This invention can quickly obtain the peak stress at the rock fracture point and the attenuation of the explosive stress under the current explosive charge.

[0029] 2. This invention utilizes a device and method for measuring the peak stress at the rock fracture point during blasting using a thin circular ring. It enables testing of coupled blasting with a fully charged borehole. Through multiple experimental comparative analyses, it provides highly accurate and reliable data, allowing for better analysis of the peak stress at the rock fracture point and the attenuation of explosive stress during quantitative explosive blasting, providing data reference for engineering blasting construction. Furthermore, this invention can also measure the peak stress at the rock fracture point and the attenuation of explosive stress during decoupled blasting operations, blasting in directions different from the borehole. This allows for the determination of the possible crushing zone, fracture zone, and elastic vibration zone that may occur during blasting in different materials and with different explosive charge positions, thereby enabling the development of corresponding blasting schemes.

[0030] 3. The device and method of the present invention are simple to operate and can be tested on the construction site, which greatly facilitates the operation of construction personnel, can quickly and efficiently measure data, avoids the need to go to the laboratory to measure experimental data, greatly reduces time costs, and greatly improves the progress of the project.

[0031] 4. This invention can be used not only to test the maximum stress generated by engineering blasting and the attenuation of the explosive stress, but also to test the huge water pressure impact force generated by the opening of the reservoir gate to release water on the riverbed, the huge stress generated by landslides, and other situations that may generate instantaneous huge stress.

[0032] 5. The materials used in this invention are a thin circular ring, a cardboard cover plate, strain gauges, and high-grade two-core shielded wires specifically for strain gauges. These materials are inexpensive, significantly reducing experimental costs and saving resources. Attached Figure Description

[0033] Figure 1 This is a schematic diagram of the device for testing the peak stress at the fracture point of rock mass during blasting, as described in this invention.

[0034] Figure 2 This is a wiring diagram of strain gauges on the inner wall of a thin circular ring when a thin circular ring is embedded in the same direction as the peak stress device for testing rock fracture during blasting according to the present invention.

[0035] Figure 3 This is a perspective view of the strain gauge wiring attached to the inner wall of the thin circular ring of the device for testing the peak stress at the rock fracture point during blasting, and a comparison image of the thin circular ring with a cardboard cover attached.

[0036] Figure 4 This is a top view showing the embedding of a thin circular ring in the peak stress testing device at the rock fracture point during blasting, as per the present invention.

[0037] Figure 5 This is a schematic front view of the thin circular ring embedded in the peak stress device at the rock fracture point during blasting, as per the present invention.

[0038] Figure 6 This is a diagram showing the dynamic strain gauge and wiring diagram of the device for testing peak stress at rock fracture points during blasting, as described in this invention.

[0039] Figure 7 This is a diagram showing the arrangement of the thin ring and strain gauges in the borehole-decoupled charge of the peak stress device for testing rock fracture during blasting, as per the present invention.

[0040] Figure 8 This invention provides a diagram showing the arrangement of thin rings and strain gauges when the peak stress device for testing rock fracture during blasting is used in tunnel excavation blasting, with the blast holes and explosive charges placed horizontally.

[0041] Figure 9 For the present invention Figure 1 The derivation of the stress-strain relationship formula for the circular ring is illustrated in the schematic diagram of micro-element analysis.

[0042] Figure 10 This is a flowchart of the method for testing the peak stress at the fracture point of rock mass during blasting, as described in this invention.

[0043] Reference numerals: 1. Rock specimen; 2. Circular test specimen; 201. Cover plate; 202. Strain gauge; 203. Thin circular ring; 3. Rock fracture zone; 4. Dynamic strain gauge; 5. Wire; 6. Blast hole; 7. Explosive charge; 8. Explosion-proof baffle; 9. Main unit. Detailed Implementation

[0044] The technical solutions of the embodiments of the invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the invention, and not all embodiments. Based on the embodiments of the invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the invention.

[0045] Example 1

[0046] Please see Figure 1 An apparatus for testing the peak stress at the fracture point of rock mass during blasting, comprising a rock specimen, a blasting assembly, and a testing assembly:

[0047] Rock specimens, formed by concrete casting, are used to simulate rocks. The appropriate concrete mix ratio can be selected based on the strength of the rock.

[0048] The blasting assembly, located at the center of the rock specimen 1, is used to blast the rock specimen 1. After the rock specimen 1 is blasted, a rock fracture zone 3 is formed. The rock fracture zone 3 includes a crushing zone and a fracturing zone. The rock fracture zone 3 is also a simulated rock mass crushing zone. The blasting assembly includes a borehole 6 and an explosive charge 7 filled in the borehole 6. When the explosive charge 7 fills the borehole 6, the center of the explosive charge coincides with the center of the borehole for coupled blasting.

[0049] The test assembly, located within the rock fracture zone (including the crushing zone and the fracturing zone) 3, is used to test the explosive stress and stress attenuation on the horizontal and central vertical planes within the rock fracture zone (including the crushing zone and the fracturing zone) 3. The test assembly includes a horizontal plane test unit for bearing the horizontal explosive stress and a central vertical plane test unit for bearing the vertical explosive stress. The horizontal plane test unit has at least four sets, located radially from the explosive assembly. The central vertical plane test unit is located directly below the explosive assembly. Both the horizontal plane test unit and the central vertical plane test unit have multiple test points, and each test point corresponds to a circular test piece 2.

[0050] Preferably, the circular test piece 2 includes a thin circular ring 203, with a through hole at the center of the thin circular ring 203. A strain gauge 202 is applied to the inner wall of the through hole. The strain gauge 202 is used to sense the deformation state of the thin circular ring 203 under the blast pressure after the blasting component is activated. Cover plates 201 are provided at both ends of the thin circular ring 203.

[0051] Specifically, the cover plate is preferably a cardboard cover plate, used to be pasted to both ends of the thin ring to prevent concrete from entering the thin ring during its installation and affecting the experiment. The thin ring is used to be installed near the same horizontal plane as the center of the explosive charge and on the vertical plane passing through the center of the explosive charge, bearing the vertical explosion stress, and is an important part of the entire testing device. The thin ring is a hollow circular ring specimen with an outer diameter of 29.2 mm and an inner diameter of 12 mm, and its thickness is 5 mm. The elastic modulus of the material used is selected according to the experimental requirements and must meet the requirement that it only deforms without breaking after being subjected to explosion stress. The structural strength of the thin ring is much higher than that of the material being exploded, and the material of the thin ring has high strength and strong resistance, which can effectively avoid damage to the test specimen due to the huge stress generated by the explosion, which is conducive to the scientific accuracy of the experimental test. Under the influence of explosion stress, the thin ring will undergo irreversible plastic deformation and will not rebound. Therefore, the strain data measured by strain gauges is more accurate and can reduce experimental errors.

[0052] Preferably, the test assembly also includes a dynamic strain gauge 4 for receiving deformation state data of the strain gauges 202, with each strain gauge 202 connected to the dynamic strain gauge 4 via a wire 5.

[0053] Specifically, the strain gauge is a rectangular thin sheet 5mm wide and 18.8-18.9mm long. The strain gauge provides feedback on the deformation data of the thin ring under pressure after the blast is initiated. When burying the thin ring, the side with the strain gauge should face the center of the explosive charge and be on the same horizontal plane as the center of the explosive charge to ensure uniform stress on the thin ring and accurate recording of the deformation data caused by the blast stress.

[0054] Specifically, the conductor 5 is a high-grade two-core shielded conductor specifically for strain gauges; the dynamic strain gauge 4 is a TST5961 dynamic strain gauge, and each strain gauge must be individually connected to two channels on the TST5961 dynamic strain gauge to form a closed loop for transmitting the data recorded by the strain gauge. The conductor must be able to withstand a certain pressure without breaking and be able to transmit accurate data. The maximum input range of the TST5961 dynamic strain gauge is ±10000uε, the resolution is 0.1uε, the number of channels is 32, and each channel does not interfere with each other.

[0055] In use, the TST5961 dynamic strain gauge receives data from each strain gauge and transmits the data to the host 9 and display screen of the accompanying software via a data cable. The host 9 and display screen of the accompanying software are used to process the data transmitted by the strain gauge, display the strain curve in real time, obtain the maximum strain value, and save the data using dedicated software. It can also be used to control the electric detonator to start the detonation program. Of course, how the data is processed and how the electric detonator is controlled uses existing processing software and hardware.

[0056] An electric detonator is embedded in the explosive charge. The electric detonator is used to detonate the explosive charge. It is activated by a specific program of the main unit 9. Detonation can only be carried out after personnel safety has been confirmed, so as to avoid explosion accidents caused by improper operation and improve the safety of the experiment. The detonation of the electric detonator is controlled by existing technology, which will not be described in detail here.

[0057] Preferably, the area of ​​strain gauge 202 occupies half of the area of ​​the through hole and is located close to the position of the explosive charge 7.

[0058] Preferably, an explosion-proof baffle is installed on one side of the rock specimen 1, and the dynamic strain gauge is located on the side of the explosion-proof baffle 8 away from the rock specimen 1. The explosion-proof baffle is used to withstand the shock wave generated by the blast and the flying rocks that may be generated by the blast, protecting the personal safety of the operators and ensuring the safety of the experiment.

[0059] Preferably, the thin ring 203 deforms without breaking under explosive stress, and the elastic modulus of the material of the thin ring 203 is 17-206 GPa. A reference table of the elastic modulus of commonly used materials for thin rings is shown in Table 1.

[0060] Table 1 Elastic modulus of thin circular ring material

[0061] lead 17 Rolled aluminum 69 Hard aluminum alloy 70 Rolled zinc 82 Cold-drawn brass 90～97 Hard aluminum bronze 103 Rolled manganese bronze 108 Rolled pure copper 108 Rolled phosphor bronze 113 Cold-drawn pure copper 127 White / Gray Cast Iron 113～157 Ductile iron 140～154 Malleable cast iron 155 cast steel 175 carbon steel 200～201 Nickel-chromium steel, alloy steel 206

[0062] See Figure 7 The peak stress device for testing rock fracture during blasting, as described in this invention, can also be used to test blasting methods for rock specimens with uncoupled charges in the borehole. When used to test blasting methods for rock specimens with uncoupled charges in the borehole, the strain gauge is positioned close to the explosive charge.

[0063] See Figure 8 The peak stress device for testing rock fracture during blasting, as described in this invention, can also be used to test blasting during tunnel excavation. During tunnel excavation blasting, the blast hole and explosive charge are placed horizontally, and strain gauges are also positioned near the explosive charge.

[0064] Example 2

[0065] See Figure 10 A method for testing the peak stress at the fracture point of rock mass during blasting, the specific steps of which are as follows:

[0066] S1. Cast rock specimens to determine the location of the blast holes, the amount of explosive charge in the explosive package, and estimate the maximum explosive stress that the explosive package may generate. Select a thin ring 203 of suitable material. In this embodiment, the thin ring used has an outer diameter of 29.2 mm, an inner diameter of 12 mm, and a thickness of 5 mm.

[0067] S2. Select a rectangular strain gauge 202 with a length of 18.8–18.9 mm and a width of 5 mm. Use AB glue to attach the strain gauge 202 to a suitable location on the inner wall of the thin ring 203. The specific dimensions of the thin ring can be made according to the available materials and needs at the construction site, as well as the existing strain gauge dimensions. The inner wall area of ​​the thin ring must be twice the strain gauge compression area. Then, connect the strain gauge-specific high-grade two-core shielded wire 5 to the strain gauge 202.

[0068] S3. Use AB glue to attach the cardboard cover plate 201 to both ends of the thin ring 203, and bury it in eight directions (horizontal plane test unit) radially to the same horizontal plane of the explosive charge and in the vertical direction (central vertical plane test unit) passing through the center of the explosive charge. When burying the thin rings in the same direction, the center point of the thin ring, the center point of the strain gauge, and the center of the explosive charge position should be on the same straight line, and the side with the strain gauge should face the explosive charge position. Set three test points in each direction, and bury one ring test piece for each test point. The thin rings in the same direction should be spaced 100mm apart, with the thin ring closest to the explosive charge position 1 150mm away from the blast hole position 1. If the requirements of the construction site differ, the spacing between the thin rings and the distance between the thin ring closest to the explosive charge position and the blast hole position can be changed according to the specific requirements of the on-site blasting project to ensure the scientific accuracy of the test results. The installation of the circular test specimens and their wires in the eight directions of the horizontal plane and the vertical direction can be carried out by drilling or by pouring rock specimens layer by layer while simultaneously installing them.

[0069] S4. Connect the high-grade two-core shielded wire 5 for strain gauges to the TST5961 dynamic strain gauge 4, ensuring that each strain gauge is individually connected to a single interface (two channels) on the strain gauge to form a closed loop. Then, use a data cable to connect the strain gauge to the host computer 9 and display screen of the accompanying software. Open the accompanying software and check whether the strain gauges, strain gauge, host computer 9, and display screen are functioning normally. Only after confirming that they are functioning normally can you proceed to the next step (the display screen and the host computer carrying the software use conventional equipment in the existing technology).

[0070] S5. Install the explosion-proof baffle 8 and the electric detonator. Connect the electric detonator to the power line. After confirming that all personnel have evacuated to a safe area, connect the other end of the power line to the main unit 9. The operator then starts the detonation procedure to begin the experiment.

[0071] S6. After the detonation procedure is initiated, the host computer and display screen equipped with the supporting software record the strain curves and strain data of the inner walls of each thin ring in real time. The maximum strain value is substituted into the derived ring stress-strain relationship formula (10) to calculate the maximum stress on the outer wall of the thin ring, which is the peak explosive stress at the location of the thin ring. The strain data and the calculated peak explosive stress data are saved using dedicated software. See Figure 9 Divide the thin circular ring into many small parts through the center, and analyze one of them. The derivation of the mechanical property formula of the thin circular ring is as follows:

[0072] Consider a thin circular ring as a differential element. Assume the pressure on the outer wall of the ring is p, and a and b are boundary coefficients. Since the outer diameter of the thin ring is 29.2 mm, the outer radius is 14.6 mm. The inner diameter is 12 mm, so the inner radius is 6 mm. Assuming the pressure on the inner wall of the thin ring is 0, the boundary conditions are as follows:

[0073]

[0074]

[0075] Solving for:

[0076]

[0077]

[0078] (Analysis only of normal stress) (5) When r = 6 mm

[0079] but

[0080] And σ=E·ε(8)

[0081]

[0082] Simplifying, we get: p = 2.461E·ε (To ensure accuracy, we take 3 significant figures.) (10)

[0083] If the size of the thin ring can be changed based on the available materials and requirements at the construction site, assuming the outer radius of the thin ring after the size change is l1 and the inner radius is l2, then the following formula can be used for calculation:

[0084]

[0085] The measured strain data were systematically screened, and thin rings with peak strain values ​​less than 500 (low accuracy) were selected as test points. Without changing the position of these thin rings, the material of the thin rings was changed, and the above method was repeated until the peak strain values ​​of all thin rings were greater than 500. The requirements for the new thin ring material were: the elastic modulus must be lower than that of the original material to increase the strain on the inner wall of the thin ring and improve accuracy; and the replaced thin ring must withstand explosive stress without failure. The elastic modulus of commonly used thin ring materials is shown in Table 1.

[0086] In this embodiment of the invention, the peak explosive stress of all high-precision strain gauges is summarized, and the explosive stress attenuation diagram is plotted using the accompanying software and the attenuation of explosive stress is analyzed to provide data reference for actual construction.

[0087] In summary, the device and method for testing the peak stress at the rock fracture point during blasting utilize a horizontal plane testing unit and a central vertical plane testing unit to measure the strain generated by the shock wave on a thin circular ring during blasting of a rock specimen. This allows for the deduction of the stress on the inner ring, and further analysis of the ring's performance yields the stress on the outer ring, i.e., the peak explosive stress at the location of the thin circular ring. This allows for the rapid determination of the peak stress at the rock fracture point and the attenuation of the explosive stress under the current explosive charge. Furthermore, this invention can test coupled blasting with the explosive charge filling the borehole. Through multiple experimental comparative analyses, it provides highly accurate and reliable data, enabling better analysis of the peak stress at the rock fracture point and the attenuation of the explosive stress during quantitative explosive blasting, thus providing data reference for engineering blasting operations. This invention can also measure the peak stress at the rock fracture point and the attenuation of the explosive stress during decoupled blasting operations when blasting in directions different from the borehole. This allows for the determination of the crushing zone, fracture zone, and elastic vibration zone that may occur during blasting in different materials and at different explosive charge positions, thereby enabling the formulation of corresponding blasting schemes.

[0088] It should be noted that, in this document, relational terms such as "first" and "second" are used only to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Furthermore, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such process, method, article, or apparatus.

[0089] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A device for testing the peak stress at the fracture point of rock mass during blasting, characterized in that, The device includes: Rock specimens, formed by concrete casting, are used to simulate rocks; The blast hole, located at the center of the rock specimen, is used to blast the rock specimen, and after the rock specimen is blasted, a rock fracture zone is formed. The blast hole is used to fill the explosive charge and electric detonator. The testing assembly, located within the rock fracture zone, is used to test the explosive stress and stress attenuation on the horizontal and central vertical planes within the rock fracture zone. The testing assembly includes a horizontal plane testing unit for withstanding horizontal explosive stress and a central vertical plane testing unit for withstanding vertical explosive stress. The horizontal plane testing unit has at least four sets, each located radially from the borehole. The central vertical plane testing unit is located directly below the borehole. Both the horizontal plane testing unit and the central vertical plane testing unit have multiple testing points, with each testing point corresponding to a circular test piece. The circular test piece includes a thin circular ring, a strain gauge, and a cover plate. The thin circular ring has a through hole at its center, and the strain gauge is installed on the inner wall of the through hole. The strain gauge is used to sense the deformation state of the thin circular ring under the explosive stress after the explosion is initiated. The two ends of the thin circular ring are respectively provided with cover plates to prevent concrete from entering during the pouring process.

2. The apparatus for testing the peak stress at the fractured part of rock mass during blasting according to claim 1, characterized in that: The testing assembly also includes a dynamic strain gauge for receiving strain gauge deformation state data, and each strain gauge is connected to the dynamic strain gauge via wires.

3. The apparatus for testing the peak stress at the fractured rock mass during blasting according to claim 2, characterized in that: The strain gauge has a compressive deformation area that occupies half of the inner wall area of ​​the thin ring, and the strain gauge is located on the side closer to the explosive pack.

4. The apparatus for testing the peak stress at the fractured rock mass during blasting according to claim 3, characterized in that: An explosion-proof baffle is provided on one side of the rock specimen, and the dynamic strain gauge is located behind the explosion-proof baffle and on the side away from the rock specimen.

5. The apparatus for testing the peak stress at the fractured rock mass during blasting according to claim 4, characterized in that: The thin ring only deforms without being destroyed after being subjected to explosive stress, and the elastic modulus of the material of the thin ring is 17-206 GPa.

6. A method for testing the peak stress at the fracture point of rock mass during blasting, characterized in that, The specific steps of using the apparatus for testing the peak stress at the rock fracture point during blasting as described in any one of claims 1-5 are as follows: S1. Determine the explosive equivalent, estimate the maximum explosive stress value that the explosive charge may generate, and select the material corresponding to the elastic modulus of the thin ring of the horizontal plane test unit and the central vertical plane test unit according to the estimated maximum explosive stress value. S2. Attach the strain gauge to the inner wall of the thin ring and bring it close to the explosive charge, ensuring that the compressive deformation area of ​​the strain gauge occupies half of the inner wall area of ​​the thin ring. After the strain gauge is attached, connect it with wires and attach the cover plate to both ends of the thin ring so that the wires connecting the strain gauge are located between the thin ring and the cover plate, ensuring that there is no gap between the cover plate and the thin ring. This completes the assembly of the ring test piece. Repeat this process to make multiple pieces for later use. S3. At the center of the rock specimen, multiple circular test pieces corresponding to the central vertical plane test unit are buried at equal intervals in the vertical direction passing through the center of the explosive pack. Multiple circular test pieces corresponding to the horizontal plane test unit are buried at equal intervals in at least four directions around the same horizontal plane of the explosive pack, and the circular test pieces in each direction are in the same straight line with the explosive pack. Connect the wires corresponding to all strain gauges to the dynamic strain gauge respectively. S4. Install an explosion-proof baffle on one side of the rock specimen and fill the borehole with explosive charges; S5. Detonate the explosive charge to start the blasting, record the strain data of the dynamic strain gauge, and according to the strain curve, take the peak strain value and substitute it into the circular ring stress-strain relationship formula to obtain the peak explosive stress at each thin circular ring position. The attenuation of explosive stress is determined based on the distribution of peak explosive stress at each thin ring location.

7. The method for testing the peak stress at the fractured part of the rock mass during blasting according to claim 6, characterized in that: The method for selecting the appropriate elastic modulus material of the thin ring in step S1 for the horizontal plane test unit is as follows: Based on the estimated maximum explosive stress that the explosive charge can generate, the material of the thin ring is initially selected, and steps S2-S5 are performed to obtain the peak explosive stress value corresponding to each test point. Thin ring test points with peak strain values ​​less than 500 are selected. All thin ring materials in the same ring ring at the test point with a peak strain value less than 500 are replaced to ensure consistency. The elastic modulus of the replaced thin ring material must be less than that of the initially selected thin ring material. The experiment is repeated until the peak strain values ​​of all thin rings are greater than 500. When the tested peak strain values ​​are all greater than 500, the appropriate elastic modulus of each ring in the horizontal plane test unit is obtained. The method for selecting the material of a thin ring with a suitable elastic modulus for the central vertical plane test unit is as follows: Based on the estimated maximum explosive stress that the explosive charge can generate, the material of the thin ring is initially selected, and steps S2-S5 are performed to obtain the peak explosive stress value corresponding to each test point. The thin ring test point with a peak strain value of less than 500 is selected, and the material of the thin ring at the test point with the peak strain value of less than 500 is replaced. The elastic modulus of the replaced thin ring material must be less than the elastic modulus of the initially selected thin ring material. The experiment is repeated until the strain value of all thin ring peaks is greater than 500. When the strain value of the tested peaks is greater than 500, the thin ring with a suitable elastic modulus for each point of the central vertical plane test unit is obtained.

8. The method for testing the peak stress at the fracture point of rock mass during blasting according to claim 7, characterized in that: The stress-strain relationship formula for the circular ring mentioned in step S4 is: In the formula: This is the stress value. The elastic modulus of the thin circular ring, This represents the strain value of the inner wall of the ring. The outer radius of the ring, Let be the inner radius of the annulus.

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