Device and method for acquiring expansion parameters of non-penetrating structural surfaces under CO2 phase change pneumatic action

Abstract

The present invention provides a device and method for acquiring expansion parameters of a non-penetrating structural surface under the action of CO2 phase change pneumatics. The acquisition method includes prefabricating a PMMA thin plate, drilling a blasthole in the middle of the thin plate to prefabricate the non-penetrating structural surface, providing a foil resistance strain gauge on one side, and spraying speckle on the other side; using a micro phase change cracker to perform CO2 phase change pneumatic loading; using a high-speed camera to record changes on the thin plate surface, recording the entire process of crack initiation, expansion, and penetration; using a foil resistance strain gauge and an ultra-dynamic strain testing system to obtain the crack cracking strain and cracking time; using a digital image processing system to obtain the displacement field of the thin plate surface, and then obtain the strain field of the thin plate surface, comparing the crack cracking strain and cracking time, and analyzing the crack expansion direction, expansion length, and expansion speed. The technical solution proposed by the present invention has the beneficial effects of being able to simultaneously perform digital image testing and strain testing, and the testing method is highly efficient, low-cost, and highly feasible.

Description

Technical Field

[0001] The present invention relates to the field of geotechnical engineering technology, and in particular to a device and method for obtaining expansion parameters of a non-penetrating structural surface under the action of CO2 phase change pneumatics. Background Art

[0002] Carbon dioxide phase-change fracturing, as an alternative to explosive blasting, has been successfully applied in many projects. This technology primarily uses the phase energy difference during the carbon dioxide phase change process as the energy source for rock-breaking. During testing, an initiator is used to trigger a heating tube to generate heat, causing the liquid carbon dioxide to transition to a supercritical state. Once this state is achieved, the pressure in the carbon dioxide phase-change fracturing device continuously increases. Once the pressure exceeds the breaking pressure of the constant-pressure shear plate, the supercritical carbon dioxide is instantly released and transformed into high-pressure carbon dioxide gas, generating a pneumatic effect that impacts the rock mass and ultimately fractures the rock.

[0003] The gas-dynamic loads of carbon dioxide phase change are complex, and are mainly composed of shock stress waves and the action of high-pressure gas wedges. The synergistic influence mechanism of shock stress waves and high-pressure gas wedges is not yet clear.

[0004] Common rock masses are composed of blocks and structural planes, which are further divided into interpenetrating and interpenetrating planes. Rock mass fragmentation is often associated with the expansion of interpenetrating planes, which are widely distributed within the rock mass. Under blasting loads, cracks in the rock mass often propagate along these planes until they penetrate and break the rock. Interpenetrating planes within the rock mass are key media factors influencing the effectiveness of blasting. Analyzing the expansion mechanism of interpenetrating planes under the action of carbon dioxide phase-change gasification provides the theoretical foundation for understanding the mechanism of carbon dioxide phase-change fracturing and is crucial for achieving efficient carbon dioxide phase-change fracturing in engineering. Analyzing the interpenetrating mechanism of interpenetrating planes first requires determining the key expansion parameters of these planes. Currently, research on the expansion mechanism of interpenetrating planes under carbon dioxide phase-change fracturing technology is lacking, and methods for determining the expansion parameters of interpenetrating planes under the action of carbon dioxide phase-change gasification have also not been explored. Summary of the Invention

[0005] In view of this, an embodiment of the present invention provides a device and method for obtaining expansion parameters of non-penetrating structural surfaces under the action of CO2 phase change pneumatics, aiming to obtain the expansion length, direction and expansion speed of non-penetrating structural surfaces under the action of carbon dioxide phase change pneumatics. The testing method is highly efficient, low-cost and highly feasible.

[0006] An embodiment of the present invention provides a device for acquiring expansion parameters of a non-penetrating structural surface under the action of CO2 phase change pneumatics, comprising a PMMA sheet, a micro phase change cracking device, a plurality of foil resistance strain gauges, a high-speed camera, a digital image processing system, and an ultra-dynamic strain testing system;

[0007] The PMMA sheet has a first side surface and a second side surface facing each other, a blasthole drilled through the middle, and a non-through structural surface prefabricated on each of the first side surface and the second side surface is located on one side of the blasthole. The second side surface is sprayed with speckles. A plurality of foil-type resistance strain gauges are provided on the first side surface. The energy release port of the micro phase change cracking device is provided in the blasthole, with the portion extending from the blasthole on the same side as the first side surface, for performing supercritical carbon dioxide phase change pneumatic loading on the PMMA sheet.

[0008] The high-speed camera is opposite to the second side surface and is used to record an image of the second side surface. The ultra-dynamic strain testing system is electrically connected to the foil resistance strain gauge and is used to obtain the cracking strain and cracking time of the crack. The digital image processing system is electrically connected to the high-speed camera and is used to obtain the displacement field of the surface of the PMMA thin plate based on the image, thereby obtaining the strain field of the surface of the PMMA thin plate, comparing the cracking strain and cracking time of the crack, and analyzing the crack propagation direction, propagation length, and propagation speed.

[0009] Furthermore, the non-through structural surface is a blasthole-connected structural surface, the blasthole-connected structural surface is directly connected to the blasthole, and the length of the blasthole-connected structural surface is less than the minimum crack length in the pre-cracking test of the PMMA sheet without the structural surface;

[0010] The long side direction of the foil resistance strain gauge is perpendicular to the extension direction of the blasthole communication type structural surface, and is arranged in parallel and densely at the end of the blasthole communication type structural surface.

[0011] Furthermore, a plurality of foil-type resistance strain gauges are provided in parallel on both sides of the blasthole communication type structural surface, and the long side direction of the foil-type resistance strain gauge is parallel to the extension direction of the blasthole communication type structural surface.

[0012] Furthermore, the non-through structural surface is a blasthole non-connected structural surface, the blasthole non-connected structural surface is not connected to the blasthole, and the distance between the blasthole non-connected structural surface and the blasthole is less than the minimum crack length in the pre-cracking test of the PMMA sheet without the structural surface;

[0013] The line connecting the midpoint of the non-connected structural surface of the blasthole and the center of the blasthole is perpendicular to the non-connected structural surface of the blasthole. The long side direction of the foil resistance strain gauge is perpendicular to the extension direction of the non-connected structural surface of the blasthole, and is arranged in parallel and densely at both ends of the non-connected structural surface of the blasthole.

[0014] Furthermore, a plurality of foil-type resistance strain gauges are provided in parallel on both sides of the non-connected structural surface of the blasthole, and the long side direction of the foil-type resistance strain gauge is parallel to the extension direction of the non-connected structural surface of the blasthole.

[0015] Furthermore, the distance between the end of the non-connected structural surface of the blasthole and the center of the blasthole is less than the maximum length of the crack in the pre-cracking test of the PMMA sheet.

[0016] An embodiment of the present invention further provides a method for obtaining expansion parameters of a non-penetrating structural surface under the action of CO2 phase change pneumatics, comprising the following steps:

[0017] S1 prefabricates a square PMMA sheet, drills a hole in the middle of the PMMA sheet to form a blasthole, and uses laser cutting technology to prefabricate a non-through structural surface;

[0018] S2 provides a plurality of foil-type resistance strain gauges arranged in parallel on one side of the PMMA sheet having the non-through structural surface, and sprays speckles on the other side of the PMMA sheet;

[0019] S3 uses a micro phase change cracker to perform supercritical carbon dioxide phase change pneumatic loading on the prefabricated PMMA sheet;

[0020] S4 uses a high-speed camera to record the changes on the surface of the PMMA sheet in the observation area, and records the entire process of crack initiation, expansion, and penetration;

[0021] S5 uses foil resistance strain gauges and ultra-dynamic strain testing system to obtain crack opening strain and cracking time;

[0022] S6: Based on the changes in the second side surface of the PMMA sheet, a digital image processing system is used to obtain the displacement field of the surface of the PMMA sheet, and then the strain field of the surface of the PMMA sheet is obtained. The cracking strain and cracking time of the crack are compared to analyze the crack propagation direction, propagation length and propagation speed.

[0023] Furthermore, step S3 includes:

[0024] S31 assembles the micro phase change cracker, and after the assembly is completed, uses a filling device to fill it with liquid carbon dioxide. After the filling is completed, the sealing of the micro phase change cracker is tested, and after the test is completed, it is connected to the excitation device;

[0025] S32: completely inserting the energy-discharging head of the micro phase change cracker into the blasthole, and using the excitation device to excite the micro phase change cracker to perform supercritical carbon dioxide phase change pneumatic loading on the PMMA sheet.

[0026] Furthermore, in step S5, in the strain variation time curve measured by the foil resistance strain gauge, the strain corresponding to the transition point where the strain value changes from nonlinear growth to linear growth is the cracking strain.

[0027] Furthermore, step S6 includes:

[0028] A high-speed camera was used to record the speckle patterns of the second side surface of the PMMA sheet before and after deformation. A digital image processing system was used to discretize the speckle patterns into digital grayscale images. A correlation operation was then performed on the two digital grayscale images to obtain the extreme points of the correlation coefficient, and then the corresponding displacement and deformation information was obtained. The crack initiation strain and cracking time of the crack were compared to analyze the crack propagation direction, length, and speed.

[0029] The beneficial effects of the technical solution provided by the embodiment of the present invention are as follows: a non-through structural surface is provided on the first side of the PMMA sheet, and a foil resistance strain gauge is provided on the first side to enable dynamic strain testing, and a non-through structural surface and speckle are provided on the second side to enable digital image acquisition. The displacement field of the PMMA sheet during the test is obtained by a high-speed camera combined with a digital image processing system, and the strain field on the surface of the PMMA sheet can be obtained after processing. The cracking strain and cracking time of the crack are obtained by comparison with the ultra-dynamic strain testing system, and the expansion length, direction and expansion speed of the non-through structural surface under the action of carbon dioxide phase change pneumatics are obtained through comprehensive processing. This experimental method can obtain the key parameters for the expansion of the prefabricated non-through structural surface of the PMMA plate under the action of supercritical carbon dioxide phase change pneumatics, which is helpful for the study of the carbon dioxide phase change pneumatic-dynamic rock breaking mechanism. This test method can simultaneously perform digital image testing and strain testing, with high efficiency, low cost and strong feasibility. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] Figure 1 This is a structural diagram of an embodiment of a device for acquiring expansion parameters of a non-penetrating structural surface under the action of CO2 phase change pneumatics provided by the present invention;

[0031] Figure 2 yes Figure 1 A partial schematic diagram of a micro-phase change cracker inserted into a blasthole;

[0032] Figure 3 yes Figure 1 Schematic diagram of a non-through structural surface (the non-through structural surface is a non-connected structural surface of a blasthole) and a foil resistance strain gauge on the first side surface of the PMMA thin plate;

[0033] Figure 4 yes Figure 1 Schematic diagram of a non-penetrating structural surface (the non-penetrating structural surface is a blasthole connectivity structural surface) and a foil resistance strain gauge provided on the first side surface of the PMMA thin plate.

[0034] In the figure: 1-micro phase change cracker, 2-non-penetrating structural surface, 3-foil resistance strain gauge, 4-first side surface, 5-second side surface, 6-high-speed camera, 7-digital image processing system, 8-ultra-dynamic strain testing system, 9-fill light device, 10-annular rubber pad, 11-blast hole, 12-energy discharge port. DETAILED DESCRIPTION

[0035] To make the objectives, technical solutions and advantages of the present invention more clear, the embodiments of the present invention will be further described below with reference to the accompanying drawings.

[0036] See Figures 1 to 4 An embodiment of the present invention provides a device for obtaining expansion parameters of non-penetrating structural surfaces under the action of CO2 phase change pneumatics, including a pneumatic loading system, a PMMA thin plate, multiple foil resistance strain gauges 3, a high-speed camera 6, a digital image processing system 7, an ultra-dynamic strain testing system 8 and a fill light device 9.

[0037] The pneumatic loading system includes a micro phase change fracturing device 1, a filling device, a storage device and an excitation device. The storage device is used to store liquid carbon dioxide, the filling device is used to fill the liquid carbon dioxide into the micro phase change fracturing device 1, and the excitation device is used to perform phase change pneumatic loading on the liquid carbon dioxide. This is existing technology and therefore will not be described in detail.

[0038] The PMMA sheet is made of PMMA material with a high degree of transparency. The specimen was produced using a modeling system comprising measuring tools, cutting tools, and drilling tools. The PMMA sheet has a first side surface 4 and a second side surface 5, facing each other. A blasthole 11 is drilled through the center. The first side surface 4 is prefabricated using laser cutting technology to form a non-through structural surface 2 located on one side of the blasthole 11. The second side surface 5 is spray-painted with multiple circular speckles, each with a diameter of 0.25 mm to 0.5 mm.

[0039] The energy release port 12 of the micro phase change cracker 1 is located within the blasthole 11 and is used to perform supercritical carbon dioxide phase change pneumatic loading on the PMMA sheet. When drilling the blasthole 11, the wall of the blasthole 11 must be intact to prevent damage and cracking of the PMMA sheet caused by drilling the blasthole 11. An annular rubber gasket 10 is provided between the sidewall of the blasthole 11 and the energy release port 12 of the micro phase change cracker 1 to seal the gap between the sidewall of the blasthole 11 and the micro phase change cracker 1. The thickness of the annular rubber gasket 10 is no greater than the vertical distance between the first side surface 4 and the second side surface 5 and the energy release port 12, respectively, to ensure that the annular rubber gasket 10 does not affect the energy release of the micro phase change cracker 1.

[0040] In order to avoid the influence of the boundary of the PMMA sheet on the cracking influence range, the thickness of the PMMA sheet is greater than the sum of twice the thickness of the annular rubber pad 10 and the diameter of the energy discharge port 12 of the micro phase change fracture device 1, and the width of the PMMA sheet is 50-70 times the radius of the blasthole 11, which can avoid the influence of the boundary of the PMMA sheet on the cracking influence range.

[0041] Based on the positional relationship between the non-through structural surface 2 and the blasthole 11, the non-through structural surface 2 is divided into a blasthole-connected structural surface and a blasthole-disconnected structural surface. The blasthole-connected structural surface is directly connected to the blasthole 11, while the blasthole-disconnected structural surface is not connected to the blasthole 11. A pre-crack test was conducted on a PMMA sheet without a structural surface to obtain the minimum and maximum crack lengths at which cracks appeared in the PMMA sheet.

[0042] See Figure 4 When the non-through structural surface 2 is a blasthole-connected structural surface, the length of the blasthole-connected structural surface is less than the minimum crack length in the pre-cracking test of the PMMA thin plate without a structural surface, which can ensure that the tip of the connected structural surface can continue to expand forward under the action of gas-dynamics.

[0043] Multiple foil strain gauges 3 are disposed on the first side surface 4. Some of these foil strain gauges 3 have their long sides perpendicular to the direction of extension of the blasthole interconnecting structural surface and are densely packed parallel to the ends of the blasthole interconnecting structural surface. Another portion of these foil strain gauges 3 have their long sides parallel to the direction of extension of the blasthole interconnecting structural surface and are densely packed parallel to both sides of the blasthole interconnecting structural surface. This allows for testing the strain on both sides of the blasthole interconnecting structural surface, helping to reveal the mechanism of tip cracking of the interconnecting structural surface under aerodynamic action.

[0044] See Figure 3When the non-through structural surface 2 is a blasthole non-connected structural surface, the distance between the non-blasthole non-connected structural surface and the blasthole 11 is less than the minimum crack length in the pre-cracking test of the PMMA sheet without a structural surface, ensuring that the non-connected structural surface is affected by the aerodynamic effect. Multiple non-blasthole non-connected structural surfaces are arranged at equal intervals, the line connecting the midpoint of the non-blasthole non-connected structural surface and the center of the blasthole 11 is perpendicular to the non-blasthole non-connected structural surface, and the distance between the end of the non-blasthole non-connected structural surface and the center of the blasthole 11 is less than the minimum crack length in the pre-cracking test of the PMMA sheet, ensuring that the non-blasthole non-connected structural surface is within the cracking influence range.

[0045] Multiple foil strain gauges 3 are positioned on the first side surface 4. Some of these foil strain gauges 3 have their long sides perpendicular to the direction of extension of the non-connected blasthole surface and are densely packed in parallel at both ends of the non-connected blasthole surface. Another portion of these foil strain gauges 3 have their long sides parallel to the direction of extension of the connected blasthole surface and are densely packed in parallel on both sides of the connected blasthole surface. Testing the strain along the line connecting the blasthole 11 and the center of the non-connected blasthole surface helps reveal the mechanism of tip cracking of the non-connected blasthole surface under aerodynamic action.

[0046] The fill light device 9 is opposite to the second side surface 5 and is used to illuminate the second side surface 5. The high-speed camera 6 is opposite to the second side surface 5 and is used to record an image of the second side surface 5. The ultra-dynamic strain testing system 8 is electrically connected to the foil resistance strain gauge 3 and is used to obtain the crack cracking strain and cracking time. The digital image processing system 7 is electrically connected to the high-speed camera 6 and is used to obtain the displacement field of the PMMA sheet surface based on the image, thereby obtaining the strain field of the PMMA sheet surface, comparing the crack cracking strain and cracking time, and analyzing the crack propagation direction, propagation length, and propagation speed. The ultra-dynamic strain testing system 8 includes a resistance strain gauge, a bridge box, a dynamic strain acquisition instrument, a dynamic analyzer, and a computer. This is prior art and will not be described in detail here.

[0047] An embodiment of the present invention further provides a method for obtaining expansion parameters of a non-penetrating structural surface under the action of CO2 phase change pneumatics, comprising the following steps:

[0048] S1 prefabricates a square PMMA sheet, drills a hole in the middle of the PMMA sheet to form a blasthole 11, and uses laser cutting technology to prefabricate a non-through structural surface 2;

[0049] S2 provides a plurality of foil-type resistance strain gauges 3 arranged in parallel on one side of the PMMA sheet having the non-through structural surface 2, and sprays speckles on the other side of the PMMA sheet;

[0050] S3 uses a micro phase change cracker 1 to perform supercritical carbon dioxide phase change pneumatic loading on the prefabricated PMMA sheet;

[0051] Specifically, S31 assembles the micro phase change cracker 1, and after the assembly is completed, uses a filling device to fill it with liquid carbon dioxide. After the filling is completed, the sealing of the micro phase change cracker 1 is tested, and after the test is completed, it is connected to the excitation device;

[0052] S32: completely inserting the energy release head of the micro phase change cracker 1 into the blasthole 11; and utilizing the excitation device to excite the micro phase change cracker 1 to perform supercritical carbon dioxide phase change pneumatic loading on the PMMA sheet.

[0053] S4 uses a high-speed camera 6 to record the changes in the surface of the PMMA sheet in the observation area, recording the entire process of crack initiation, expansion, and penetration;

[0054] S5 uses the foil resistance strain gauge 3 and the ultra-dynamic strain testing system 8 to obtain the cracking strain and cracking time of the crack; in the strain change time curve measured by the foil resistance strain gauge 3, the strain corresponding to the conversion point where the strain value changes from nonlinear growth to linear growth is the cracking strain.

[0055] S6: Based on the changes in the second side surface 5 of the PMMA sheet, the digital image processing system 7 is used to obtain the displacement field of the surface of the PMMA sheet, and then the strain field of the surface of the PMMA sheet is obtained. The cracking strain and cracking time of the crack are compared to analyze the crack propagation direction, propagation length and propagation speed.

[0056] Specifically, a high-speed camera 6 is used to record the speckle patterns of the second side surface of the PMMA sheet before and after deformation. A digital image processing system 7 is used to discretize the speckle patterns into digital grayscale images. A correlation operation is then performed on the two digital grayscale images to obtain the extreme value points of the correlation coefficient, and then the corresponding displacement and deformation information is obtained. The crack initiation strain and cracking time are compared to analyze the crack propagation direction, length, and speed.

[0057] In the technical solution provided by this invention, a non-through structural surface 2 is provided on the first side 4 of a PMMA sheet. A foil resistance strain gauge 3 is installed on this first side 4 to enable dynamic strain testing, while a speckle pattern is provided on the second side 5 to enable digital image acquisition. A high-speed camera 6, combined with a digital image processing system 7, captures the displacement field of the PMMA sheet during testing. This processing yields the strain field on the PMMA sheet's surface. This is then compared with the crack initiation strain and cracking time obtained by an ultra-dynamic strain testing system 8. This comprehensive analysis yields the extension length, direction, and velocity of the non-through structural surface 2 under the action of carbon dioxide phase change pneumatics. This testing method is highly efficient, cost-effective, and highly feasible.

[0058] In this document, directional terms such as front, back, top, and bottom are defined based on the positions of components in the accompanying drawings and relative to each other, and are intended only for clarity and convenience in describing the technical solution. It should be understood that the use of these directional terms should not limit the scope of protection claimed in this application.

[0059] In the absence of conflict, the above embodiments and features in the embodiments may be combined with each other.

[0060] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. A method for obtaining expansion parameters of non-penetrating structural surfaces under the action of CO2 phase change pneumatics, characterized in that: The device comprises an acquisition device, wherein the acquisition device comprises a PMMA thin plate, a micro phase change cracker, a plurality of foil resistance strain gauges, a high-speed camera, a digital image processing system and an ultra-dynamic strain testing system; The PMMA sheet has a first side surface and a second side surface facing each other, a blasthole drilled through the middle, and a non-through structural surface prefabricated on each of the first side surface and the second side surface is located on one side of the blasthole. The second side surface is sprayed with speckles. A plurality of foil-type resistance strain gauges are provided on the first side surface. The energy release port of the micro phase change cracking device is provided in the blasthole, with the portion extending from the blasthole on the same side as the first side surface, for performing supercritical carbon dioxide phase change pneumatic loading on the PMMA sheet. The non-through structural surface is a blasthole-connected structural surface, the blasthole-connected structural surface is directly connected to the blasthole, and the length of the blasthole-connected structural surface is less than the minimum crack length in the pre-cracking test of the PMMA sheet without the structural surface; The foil resistance strain gauge is perpendicular to the extension direction of the blasthole communication type structural surface and is arranged parallel and densely at the end of the blasthole communication type structural surface; The high-speed camera is opposite to the second side surface and is used to record an image of the second side surface. The ultra-dynamic strain testing system is electrically connected to the foil resistance strain gauge and is used to obtain the cracking strain and cracking time of the crack. The digital image processing system is electrically connected to the high-speed camera and is used to obtain the displacement field of the surface of the PMMA thin plate based on the image, thereby obtaining the strain field of the surface of the PMMA thin plate, comparing the cracking strain and cracking time of the crack, and analyzing the crack propagation direction, propagation length, and propagation speed. The acquisition method comprises the following steps: S1 prefabricates a square PMMA sheet, drills a hole in the middle of the PMMA sheet to form a blasthole, and uses laser cutting technology to prefabricate a non-through structural surface; S2 provides a plurality of foil-type resistance strain gauges arranged in parallel on one side of the PMMA sheet having the non-through structural surface, and sprays speckles on the other side of the PMMA sheet; S3 uses a micro phase change cracker to perform supercritical carbon dioxide phase change pneumatic loading on the prefabricated PMMA sheet; S4 uses a high-speed camera to record the changes on the surface of the PMMA sheet in the observation area, and records the entire process of crack initiation, expansion, and penetration; S5 uses foil resistance strain gauges and ultra-dynamic strain testing system to obtain crack opening strain and cracking time; S6: Based on the changes in the second side surface of the PMMA sheet, a digital image processing system is used to obtain the displacement field of the surface of the PMMA sheet, and then the strain field of the surface of the PMMA sheet is obtained. The cracking strain and cracking time of the crack are compared to analyze the crack propagation direction, propagation length and propagation speed.

2. The method for obtaining expansion parameters of non-penetrating structural surfaces under the action of CO2 phase change pneumatics according to claim 1, characterized in that: A plurality of foil-type resistance strain gauges are provided in parallel on both sides of the blasthole communication type structural surface, and the long side direction of the foil-type resistance strain gauge is parallel to the extension direction of the blasthole communication type structural surface.

3. The method for obtaining expansion parameters of non-penetrating structural surfaces under the action of CO2 phase change pneumatics according to claim 1, characterized in that: The non-through structural surface is a blasthole non-connected structural surface, the blasthole non-connected structural surface is not connected to the blasthole, and the distance between the blasthole non-connected structural surface and the blasthole is less than the minimum crack length in the pre-cracking test of the PMMA sheet without the structural surface; The line connecting the midpoint of the non-connected structural surface of the blasthole and the center of the blasthole is perpendicular to the non-connected structural surface of the blasthole. The long side direction of the foil resistance strain gauge is perpendicular to the extension direction of the non-connected structural surface of the blasthole, and is arranged in parallel and densely at both ends of the non-connected structural surface of the blasthole.

4. The method for obtaining expansion parameters of non-penetrating structural surfaces under the action of CO2 phase change pneumatics according to claim 3, characterized in that: A plurality of foil resistance strain gauges are provided in parallel on both sides of the non-connected blasthole structure surface, and the long side direction of the foil resistance strain gauge is parallel to the extension direction of the non-connected blasthole structure surface.

5. The method for obtaining expansion parameters of non-penetrating structural surfaces under the action of CO2 phase change pneumatics according to claim 3, characterized in that: The distance between the end of the non-connected structural surface of the blasthole and the center of the blasthole is less than the maximum length of the crack in the pre-cracking test of the PMMA sheet.

6. The method for obtaining expansion parameters of non-penetrating structural surfaces under the action of CO2 phase change pneumatics according to claim 1, characterized in that: Step S3 includes: S31 assembles the micro phase change cracker, and after the assembly is completed, uses a filling device to fill it with liquid carbon dioxide. After the filling is completed, the sealing of the micro phase change cracker is tested, and after the test is completed, it is connected to the excitation device; S32: completely inserting the energy-discharging head of the micro phase change cracker into the blasthole, and using the excitation device to excite the micro phase change cracker to perform supercritical carbon dioxide phase change pneumatic loading on the PMMA sheet.

7. The method for obtaining expansion parameters of non-penetrating structural surfaces under the action of CO2 phase change pneumatics according to claim 1, characterized in that: In step S5, in the strain variation time curve measured by the foil resistance strain gauge, the strain corresponding to the transition point where the strain value changes from nonlinear growth to linear growth is the cracking strain.

8. The method for obtaining expansion parameters of non-penetrating structural surfaces under the action of CO2 phase change pneumatics according to claim 1, characterized in that: Step S6 includes: A high-speed camera was used to record the speckle patterns of the second side surface of the PMMA sheet before and after deformation. A digital image processing system was used to discretize the speckle patterns into digital grayscale images. A correlation operation was then performed on the two digital grayscale images to obtain the extreme points of the correlation coefficient, and then the corresponding displacement and deformation information was obtained. The crack initiation strain and cracking time of the crack were compared to analyze the crack propagation direction, length, and speed.

Images