A carbon dioxide phase change directional pressure relief fracturing device for tunneling and its use method

Abstract

The present invention provides a carbon dioxide phase change directional pressure relief fracturing device for excavation and a method for using the same. The fracturing device includes a liquid storage pipe for storing liquid carbon dioxide, a filling valve, a heater and an explosion relief head; the explosion relief head includes an explosion relief pipeline of a Y-shaped structure, including a first pipeline, a second pipeline and a third pipeline that are interconnected, one end of the first pipeline is connected to the liquid storage pipe, the other end of the first pipeline is obliquely connected to the head end of the second pipeline and the third pipeline, the ends of the second pipeline and the third pipeline face the free surface of the tunnel to be excavated, the ends of the second pipeline and the third pipeline are explosion relief ports, carbon dioxide gas is vented through the explosion relief ports, and the angle between the explosion relief port and the borehole axis is less than 90°. The fracturing device is fixed in an inverted manner in the borehole, so that the explosion relief direction can impact the borehole wall along an oblique angle during the explosion process, and has the advantage that the shock wave is released toward the orifice along the reflection angle, thereby solving the problem of the stability of the existing fracturing device in the borehole. It not only reduces energy loss, but also eliminates the risk of fracturing device recoil.

Description

Technical Field

[0001] The invention belongs to the technical field of fracturing blasting devices, and in particular relates to a carbon dioxide phase change directional pressure relief fracturing device for tunneling and a use method thereof. Background Art

[0002] In the process of tunnel excavation in coal mines, except for medium and large mines equipped with fully-mechanized excavators, most small mines still mainly use explosive blasting for excavation. Due to the particularity of the excavation working face environment, explosive blasting will produce spark leakage and huge energy detonation waves. Once the gas in the excavation working face exceeds the limit, the spark leakage of explosives can easily cause a gas explosion accident. Especially for the protruding coal seam, the detonation wave generated by the explosives can easily induce a major coal and gas outburst accident. At the same time, the gunpowder inspection process after the blasting also has certain risks.

[0003] In order to improve the safety of the blasting process, technicians began to use carbon dioxide fracturing devices as blasting equipment for the excavation working face. The principle is to use the physical properties of carbon dioxide to pressurize and liquefy the gaseous carbon dioxide on the ground, and then bring it underground and heat it to instantly vaporize it, expanding its volume 600 times. When the gas pressure in the liquid storage pipe reaches a certain value, the high-pressure vaporized carbon dioxide gas instantly breaks through the rupture piece and sprays out from the venting hole of the venting head, producing a blasting fracturing effect. Only non-flammable inert gas carbon dioxide is involved in the entire blasting process, and no external flame is generated.

[0004] When using a carbon dioxide fracturing device, it is necessary to drill holes and dig a groove of a certain depth on the surface of a rock or mountain, and then put the carbon dioxide fracturing device into the groove. Since the vent holes of the carbon dioxide fracturing device are generally set on the side wall of the fracturing device, after the blasting is completed, the broken stones in the groove of the rock mass will cover the fracturing device, making it more difficult to clean the broken stones, which seriously affects the recovery of the carbon dioxide fracturing device in the groove, resulting in a longer blasting process cycle and affecting the blasting mining efficiency. In addition, due to the following reasons, the existing fracturing devices are Figure 5 When the explosion-relief head shown (the part marked with a solid circle line) is venting, the explosion-relief direction (the area shown with a dotted line) has almost no angle with the free surface and is arranged vertically, i.e., in an L-shape, causing the vertically reflected shock wave to return to the explosion-relief port along the original path, offsetting a portion of the output gas energy and reducing the gas energy utilization rate. In addition, the debris produced by the blasting is carried by the shock wave and accumulated on the surface of the fracturing device, making it difficult to crush and throw out the debris.

[0005] Therefore, it is necessary to provide an improved technical solution to address the above-mentioned deficiencies in the prior art. Summary of the invention

[0006] The purpose of the present invention is to provide a directional pressure relief fracturing device for tunneling and a method of using the same, so as to overcome the problems of low gas energy utilization rate, poor blasting effect, large recovery resistance of the carbon dioxide fracturing device, long blasting engineering period, etc. during use of the above-mentioned existing carbon dioxide fracturing devices.

[0007] In order to achieve the above object, the present invention provides the following technical solutions:

[0008] A carbon dioxide phase change directional pressure relief fracturing device for tunneling, comprising:

[0009] A liquid storage tube for storing liquid carbon dioxide;

[0010] A filling valve, the filling valve is connected to the liquid storage tube and is used to fill the liquid storage tube body with liquid carbon dioxide;

[0011] A heater, used for heating the liquid storage pipe to gasify the liquid carbon dioxide and increase the gas pressure in the liquid storage pipe;

[0012] An explosion relief head, the explosion relief head includes an explosion relief pipeline, the explosion relief pipeline is a Y-shaped structure, including a first pipeline, a second pipeline and a third pipeline that are interconnected, one end of the first pipeline is connected to a liquid storage pipe, the other end of the first pipeline is obliquely connected to the head ends of the second pipeline and the third pipeline, the ends of the second pipeline and the third pipeline face the free surface of the tunnel to be excavated, the ends of the second pipeline and the third pipeline are explosion relief ports, the explosion relief ports are used to relieve the carbon dioxide gas pressure, and the angle between the explosion relief port and the borehole axis is less than 90°.

[0013] Furthermore, the explosion relief head also includes a constant pressure energy relief sheet, which is arranged between the first pipeline and the liquid storage tube and is used to control the carbon dioxide gas to rush to the explosion relief port. The constant pressure energy relief sheet is used to seal the liquid storage tube and control the impact pressure, and can be used together with different models of heaters and liquid storage tubes to achieve different fracture strengths.

[0014] Furthermore, a sealing gasket is provided between the filling valve and the liquid storage tube for sealing the inlet of the liquid storage tube.

[0015] Furthermore, the angle between the explosion vent and the borehole axis is 30° to 60°.

[0016] Furthermore, the angle between the explosion vent and the borehole axis is calculated as follows:

[0017]

[0018] Where: α is the angle between the explosion vent and the borehole axis, °;

[0019] l1 is the distance between the blasting point and the orifice, m;

[0020] W max is the maximum value of the minimum resistance line, m.

[0021] Furthermore, the maximum value calculation formula of the minimum resistance line is:

[0022]

[0023] Where: W max is the maximum value of the minimum resistance line, m;

[0024] P is the bursting pressure of the carbon dioxide fracturing device, MPa;

[0025] g is the acceleration due to gravity, 9.8 m / s 2 ;

[0026] d is the drilling diameter, mm;

[0027] t is the blasting time, s;

[0028] γ is the specific gravity of rock, t / m 3 ;

[0029] u is the impact velocity of the blasting gas, m / s.

[0030] Furthermore, the maximum value of the minimum resistance line is 1m <W max <1.5m.

[0031] To achieve the above object, the present invention also provides a method for using a carbon dioxide phase change directional pressure relief fracturing device for tunneling, the method comprising the following steps:

[0032] Step 1, installing a cracking device;

[0033] Step 2, after step 1 is completed, the liquid storage tube is filled with liquid carbon dioxide by controlling the filling valve;

[0034] Step 3, inverting at least one fracturing device along the axial direction of the borehole into the borehole of the tunnel to be excavated, wherein the inverted placement means that the explosion relief port of the Y-shaped structure is facing the free surface of the tunnel to be excavated, and the angles between the explosion relief port and the free surface of the inner wall of the borehole and the free surface of the tunnel to be excavated are 30° to 60°;

[0035] Step 4, heating by controlling the heater to gasify the liquid carbon dioxide in the liquid storage tube;

[0036] Step 5, when the set pressure is reached, the carbon dioxide gas breaks through the constant pressure energy release plate and sprays outward along the explosion release port to cause explosion and cracking.

[0037] Furthermore, in step 3, the firing lines of multiple groups of borehole fracturers are connected by detonating cables to achieve simultaneous detonation of multiple groups of boreholes.

[0038] Furthermore, the method of use further comprises step 6, cleaning and recovering the fracturing device after step 5 for reuse.

[0039] Compared with the closest prior art, the technical solution provided by the present invention has the following excellent effects:

[0040] The venting head of the existing carbon dioxide fracturing device is L-shaped, and the vertical angle between the venting direction and the free surface of the hole wall is 90°, while the venting head of the carbon dioxide fracturing device in the present invention is Y-shaped, and the angle between the venting direction and the free surface of the hole wall is 30°~60°. The Y-shaped setting can make the gas direction of the blasting high-pressure carbon dioxide oblique to the hole wall, avoiding the gas shock wave acting on the hole wall at a right angle and then reflecting at a right angle along the original path, which causes the impact energy to be offset and weakened. The present invention greatly reduces the local loss of right-angle blasting and significantly improves the utilization rate of the carbon dioxide high-pressure gas energy.

[0041] The present invention fixes the carbon dioxide fracturing device in the borehole in an inverted manner, with the gas-filling end located deep in the borehole, i.e., the front end, and the explosion-relief head located at the borehole opening, i.e., the rear end. This is exactly the opposite of the traditional placement method. The explosion-relief gas impacts the borehole wall in the oblique direction of the borehole opening, and has the advantage of releasing the shock wave toward the borehole along the reflection angle. This eliminates the problem of gas impacting the bottom of the hole and then recoil-punching the fracturing device in the traditional placement method, prevents the recoil gas from flushing the fracturing device out of the hole, and solves the problem that the existing fracturing device is difficult to stabilize in the hole. The invention not only reduces energy loss, but also eliminates the risk of fracturing device recoil.

[0042] The carbon dioxide fracturing device in the present invention is placed on the excavation working face and arranged in order in the fracturing hole, the hole mouth is blocked with a sealing material, and by placing the fracturing device in reverse and the explosion relief head of the carbon dioxide fracturing device in a Y shape, the angle between the explosion relief direction of the carbon dioxide fracturing device and the free surface of the tunnel excavation is also 30° to 60°. On the basis of improving the gas energy utilization rate and reducing the risk of fracturing device recoil, the reverse shock wave can also throw the crushed stone produced by the blasting from the angle gap in the borehole, which not only has the advantages of blasting fracturing, but also can realize the purpose of real-time and rapid throwing out of coal and rock fragments in the excavation tunnel, reducing the complex process of repeated removal of blasting waste. BRIEF DESCRIPTION OF THE DRAWINGS

[0043] The drawings constituting a part of the present application are used to provide a further understanding of the present invention. The exemplary embodiments of the present invention and their descriptions are used to explain the present invention and do not constitute an improper limitation of the present invention. Among them:

[0044] Figure 1This is a schematic diagram of the structure of a carbon dioxide fracturing device in an embodiment of the present invention;

[0045] Figure 2 A schematic diagram of a carbon dioxide fracturing device connected and installed according to the present invention during blasting;

[0046] Figure 3 It is a schematic axial cross-sectional view of the explosion venting head of the carbon dioxide fracturing device in an embodiment of the present invention;

[0047] Figure 4 It is the arrangement diagram of blastholes during tunnel excavation of the present invention;

[0048] Figure 5 It is a structural schematic diagram of an existing carbon dioxide fracturing device.

[0049] In the figure: 1. filling valve; 2. sealing gasket; 3. heater; 4. liquid storage tube; 5. explosion relief head; 501. first pipeline; 502. second pipeline; 503. third pipeline; 504. constant pressure energy relief plate; 6. tunnel to be excavated; 7. borehole; 8. carbon dioxide fracturing device; 9. sealing material; 10. free surface of tunnel to be excavated; 11. free surface of inner wall of borehole; 12. built-in wire. DETAILED DESCRIPTION

[0050] The technical solutions in the embodiments of the present invention are described clearly and completely below. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. All other embodiments obtained by ordinary technicians in this field based on the embodiments of the present invention belong to the scope of protection of the present invention.

[0051] The present invention will be described in detail below with reference to the accompanying drawings and in combination with embodiments. It should be noted that the embodiments and features in the embodiments of the present invention can be combined with each other without conflict.

[0052] In engineering blasting, the minimum resistance line refers to the direction in which the rock resistance is the smallest during blasting. In this direction, the rock movement speed is the highest and the blasting effect is the most concentrated. Therefore, the minimum resistance line is the dominant direction of the blasting effect and the dominant direction of the throwing effect. Therefore, the minimum resistance line is a very important parameter that can directly affect the blasting volume per meter of drilling, the throwing distance and the fragmentation effect of the block size.

[0053] In engineering blasting, the shortest distance from the center or center of gravity of the explosive package to the nearest free surface is usually called the minimum resistance line, which is usually represented by W. The size of the minimum resistance line depends on the requirements of the blasting project, the terrain conditions and the arrangement of the explosive packages. The direction of the minimum resistance line is the direction with the least rock resistance and the direction most likely to produce flying rocks. The minimum resistance line varies depending on the nature of the rock, the blasting material and the blasting form.

[0054] The revised calculation formula of the minimum resistance line is as follows:

[0055]

[0056] Where: W max is the maximum value of the minimum resistance line, m;

[0057] P is the bursting pressure, MPa;

[0058] g is the acceleration due to gravity, 9.8 m / s 2 ;

[0059] d is the drilling diameter, mm;

[0060] t is the blasting time, s;

[0061] γ is the specific gravity of rock, t / m 3 ;

[0062] u is the impact velocity of the blasting gas, m / s.

[0063] The calculation formula of blasting gas impact velocity u is as follows:

[0064]

[0065] Where: Q is the flow rate of carbon dioxide gas rushing out of the explosion vent, m 3 / s;

[0066] S is the gas outlet area after the CO2 fracturing device is installed in the borehole, which is the inner surface area of ​​the borehole minus the outer surface area of ​​the CO2 fracturing device, m 2 ;

[0067] r is the outer diameter of the carbon dioxide fracturing device.

[0068] In this embodiment, the length l of the carbon dioxide fracturing device used is 800 mm, the outer diameter r of the carbon dioxide fracturing device is 51 mm, and considering the spatial arrangement of the excavation working face, the inner diameter d of the borehole where the carbon dioxide fracturing device is placed is 73 mm. The maximum value of the blasting pressure P of the carbon dioxide fracturing device is 216 MPa, the blasting action time t is 20 ms, and the rock specific gravity is 1.2 to 2.8 t / m 3 , the explosion gas impact velocity u is about 2×10 6 m / s.

[0069] According to the above-mentioned minimum resistance line modified formula, and taking into account the uneven specific gravity of the rock, it can be calculated that the maximum value interval of the minimum resistance line when the carbon dioxide fracturing device is acting is 1m <W max <1.5m (such as 1.2m, 1.3m, 1.4m, 1.45m, 1.49m).

[0070] The free surface refers to the interface between the blasted rock mass and the air. The resistance of the rock in the free surface direction is the smallest. Therefore, after the rock is blasted, its energy is released toward the free surface, causing the detonation wave to first break through the free surface, breaking the rock or even throwing it out. max When the fracturing device has a certain inclination angle α, the spacing of the drilling holes can be expanded, and a good effect of blasting and throwing coal and rock can be achieved, reducing the construction workload. Therefore, the blasting port of the blasting head has a certain angle with the free surface of the tunnel to be excavated, so that the coal and rock fragments can be thrown out together with the shock wave during the fracturing process.

[0071] at this time:

[0072]

[0073] Where: α is the angle between the explosion vent and the borehole axis, °;

[0074] l1 is the length from the blasting point to the orifice, m.

[0075] Combined with W max and l1, the length of l1 is determined according to the length of the borehole l. When l is greater than 1m, the length of l1 is not less than 0.5m; when l is greater than 2.5m, the length of l1 is not less than 1.0m. Therefore, the optimal value range of α in engineering practice is 30° to 60° (such as 30°, 35°, 45°, 50°, 55°, 60°), so that the explosion vent and the fracturing device are arranged in a Y-shaped manner.

[0076] According to the above-mentioned fracturing mechanism, the present invention has made structural improvements to the existing fracturing device. The structure of the carbon dioxide fracturing device of the present invention is as follows: Figure 1 As shown, the carbon dioxide fracturing device 8 includes a filling valve, a sealing gasket, a heater, a liquid storage pipe and a venting head.

[0077] The liquid storage tube body 4 is used to store liquid carbon dioxide; as another embodiment, the liquid storage tube may also be a liquid storage tank, which can achieve safe storage of liquid carbon dioxide.

[0078] The filling valve 1 is fixedly connected to the liquid storage tube 4 through the sealing gasket 2, and the liquid carbon dioxide is filled into the liquid storage tube 4 by controlling the valve opening and closing state of the filling valve 1. The sealing gasket 2 ensures the sealing of the air inlet of the liquid storage tube.

[0079] The heater 3 heats the liquid storage pipe 4, and the liquid carbon dioxide absorbs heat and vaporizes, and the gas pressure in the liquid storage pipe 4 increases. When the gas pressure in the liquid storage pipe 4 exceeds the set pressure of the constant pressure energy release plate 504, the high-pressure carbon dioxide gas is ejected along the explosion-release port to realize the energy release blasting operation.

[0080] Explosion venting head 5, the explosion venting head is a Y-shaped structure such as Figure 1 and Figure 3 As shown, the explosion relief head includes an explosion relief pipeline and a constant pressure energy relief sheet 504. The explosion relief pipeline includes a first pipeline 501, a second pipeline 502 and a third pipeline 503 which are interconnected. The first pipeline 501, the second pipeline 502 and the third pipeline 503 form a Y-shaped structure. A constant pressure energy relief sheet 504 is provided at one end of the first pipeline 501. The first pipeline 501 is connected to the liquid storage pipe 4 through the constant pressure energy relief sheet 504. When the gas pressure in the liquid storage pipe 4 reaches a certain value, the gasified carbon dioxide will break through the constant pressure energy relief sheet 504 and then rush to the tunnel through the explosion relief pipeline of the Y-shaped structure. The other end of the first pipeline 501 is connected to the head end of the second pipeline 502 and the head end of the third pipeline 503. The ends of the second pipeline 502 and the third pipeline 503 are close to and face the free surface of the tunnel to be excavated, and the explosion is vented through the ends of the second pipeline 502 and the third pipeline 503.

[0081] The ends of the second pipeline 502 and the third pipeline 503 close to the free surface of the tunnel to be excavated are the explosion relief direction of the explosion relief head 5, and the explosion relief direction forms a Y-shaped structure with the first pipeline 501 and the liquid storage pipe 4, such as Figure 1 As shown, the radial direction of the first pipeline 501 of the explosion-proof head 5 is perpendicular to the free surface 10 of the tunnel to be excavated. Due to the adjusted and improved Y-shaped arrangement structure of the carbon dioxide fracturing device 8, the explosion-proof direction of the explosion-proof head 5 forms a certain angle with the axial direction of the borehole 7, that is, the angle between the explosion-proof direction of the explosion-proof head 5 of the carbon dioxide fracturing device 8 and the free surface 11 of the inner wall of the borehole is θ1, and the angle between the explosion-proof direction of the explosion-proof head 5 and the free surface 10 of the tunnel to be excavated is θ2. By adjusting θ1 and θ2, the direction of the explosion-proof port is consistent with the minimum resistance line of the tunnel surface to be excavated, which can ensure that the rock is smoothly ejected after the carbon dioxide fracturing device 8 performs blasting and fracturing.

[0082] The method of using the carbon dioxide fracturing device 8 of the present invention at the head of the excavation working face comprises the following steps:

[0083] Step 1, construction preparation:

[0084] 1. According to the area of ​​the tunnel 6 to be excavated and the effective radius of the single carbon dioxide fracturing hole, the fracturing holes should be arranged reasonably. Figure 4For example, the effective radius h1 of single-hole fracturing of carbon dioxide is 0.4m. Under the premise of ensuring that the coal and rock between the two boreholes can be completely fractured and blasted by the high-pressure carbon dioxide gas, the maximum spacing h2 between the boreholes is 0.8m. Therefore, the left-right and top-bottom spacings between each two adjacent boreholes in the three rows of boreholes below the excavation section are set to h2=0.8m; considering that the tunnel section is "arched", the fracturing boreholes arranged in the upper semicircular area should be on a semicircular arc with the center hole of the first row as the center and h1 as the radius of 0.4m, and ensure that the straight-line spacing between the fracturing boreholes on the arc and their adjacent fracturing boreholes is less than h2=0.8m; in order not to destroy the cross-sectional contour line of the excavation tunnel, the vertical distance h3 of the peripheral fracturing boreholes from the cross-sectional contour line of the tunnel is greater than h1=0.4m, and is set to 0.5m in this embodiment.

[0085] 2. According to the designed drilling parameters, select a drilling rig with matching performance and construct fracture-inducing holes one by one.

[0086] 3. First, assemble the filling valve 1, the sealing gasket 2, the heater 3, the liquid storage tube 4, and the explosion relief head 5 into a carbon dioxide fracturing device; then, by controlling the valve head state of the filling valve 1 to open, liquid carbon dioxide is filled into the carbon dioxide fracturing device 8. After the filling and installation are completed, the carbon dioxide fracturing device 8 is transported to the tunnel to be excavated 6, and the carbon dioxide fracturing device 8 is axially inverted and placed in the borehole 7. Specifically, the filling valve 1 is placed close to the depth of the borehole, one end of the explosion relief head and the explosion relief port are close to the free surface 10 of the tunnel to be excavated, the borehole axis is parallel to the free surface 11 of the inner wall of the borehole, and the free surface 11 of the inner wall of the borehole is perpendicular to the free surface 10 of the tunnel to be excavated. The angles between the explosion relief port and the free surface of the inner wall of the borehole and the free surface of the tunnel to be excavated are 30° to 60° respectively.

[0087] like Figure 2 As shown, in order to achieve a deeper blasting effect in one blasting, at least two installed carbon dioxide fracturing devices 8 can be connected end to end, and the two or more groups of carbon dioxide fracturing devices 8 can be made conductive through the built-in conductor 12; then the carbon dioxide fracturing devices in multiple boreholes are electrically connected using a detonating cable, and the borehole 7 is effectively sealed with a sealing material 9, and the sealing material 9 can be made of yellow mud or polyurethane.

[0088] Step 2, controlled blasting:

[0089] A plurality of built-in conductors 12 are connected to a mining detonator through a detonating cable. The mining detonator is used for detonation. The high-pressure carbon dioxide gas generated by the blasting of the carbon dioxide fracturing device 8 directly acts on the wall of the fracturing borehole 7 along the direction of the explosion hole. Figure 2As shown, the angle θ2 between the explosion vent of the fracturing device and the free surface 10 of the tunnel to be excavated can eliminate the defect of the reflected wave offsetting the gas energy when the explosion vent releases the shock wave vertically to the hole wall. Under the action of heating, the liquid carbon dioxide in the liquid storage tube 4 gradually gasifies. When the gas pressure in the liquid storage tube 4 breaks through the set pressure of the constant pressure energy release plate 504, the high-pressure carbon dioxide gas is smoothly ejected along the explosion vent. The explosion vent head with a Y-shaped structure can reduce the impact of the reflected wave, reduce the gas energy loss, and ensure that the explosion vent direction is toward the free surface 10 of the tunnel to be excavated, promote the high-energy gas to efficiently crush the coal and rock, and use the reflected shock wave gas to carry the gravel out of the tunnel. In addition, during the blasting process, due to the inverted placement of the carbon dioxide fracturing device 8, the recoil effect generated after the high-pressure gas is released to impact the hole wall will recoil the fracturing device to the depth of the borehole 7, effectively preventing the fracturing device from being flushed out of the hole by the shock wave, reducing energy loss, and improving the safety factor of fracturing.

[0090] Step 3, Recover the Fracturator:

[0091] Clean up the rubble, take out the fracturing device, clean it for reuse. Since the fracturing device in the present invention is a physical blasting device, the fracturing device itself is not damaged and can be reused. This also saves the cost of the next blasting to a certain extent, and reduces the interference of on-site residues during tunnel excavation.

[0092] In summary, in order to make the carbon dioxide fracturing device 8 better applied in tunnel excavation, the present invention studies the fracturing mechanism of the carbon dioxide fracturing device 8, and with the help of the explosion relief head 5 with adjustable explosion relief direction, the fracturing device is placed in reverse, and the explosion relief direction is set at a certain angle θ2 with the free surface 10 of the tunnel to be excavated for blasting, so as to achieve the dual effects of excavation blasting and crushing coal and rock and quickly throwing out coal and rock fragments. The explosion relief port of the carbon dioxide phase change fracturing device of the present invention has a certain angle with the central axis of the borehole 7, and is distributed in a Y shape, eliminating the energy impact defect of the existing L-shaped explosion relief port, greatly reducing the local loss of right-angle blasting, and improving the energy utilization rate of carbon dioxide gas. At the same time, the inverted fracturing device is adopted to effectively prevent the fracturing device from being washed out of the hole by the shock wave, solve the problem that the fracturing device is difficult to fix, and eliminate the risk of the fracturing device being washed out of the hole.

[0093] 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 are within the scope of protection of the pending claims of the present invention.

Claims

1. A carbon dioxide phase change directional pressure relief fracturing device for tunneling, characterized in that: The fracturing device comprises: A liquid storage tube, used for storing carbon dioxide liquid; A filling valve, the filling valve is connected to the liquid storage tube and is used to fill the liquid storage tube with liquid carbon dioxide; A heater, used for heating the liquid storage pipe to gasify the liquid carbon dioxide and increase the gas pressure in the liquid storage pipe; An explosion relief head, the explosion relief head includes an explosion relief pipeline, the explosion relief pipeline is a Y-shaped structure, including a first pipeline, a second pipeline and a third pipeline that are interconnected, one end of the first pipeline is connected to a liquid storage pipe, the other end of the first pipeline is obliquely connected to the head ends of the second pipeline and the third pipeline, the ends of the second pipeline and the third pipeline face the free surface of the tunnel to be excavated, the ends of the second pipeline and the third pipeline are explosion relief ports, and the explosion relief ports are used to relieve the pressure of carbon dioxide gas; The angle between the explosion vent and the borehole axis is 30° to 60°; The angle between the explosion vent and the borehole axis is calculated as follows: ； Where: is the angle between the explosion vent and the borehole axis, °; l 1 is the distance between the blasting point and the orifice, m; is the maximum value of the minimum resistance line, m; The maximum value calculation formula of the minimum resistance line is: ； Where: is the maximum value of the minimum resistance line, m; is the bursting pressure of the carbon dioxide fracturing device, MPa; is the acceleration due to gravity, 9.8m / s 2 ; is the drilling diameter, mm; is the blasting action time, s; is the specific gravity of rock, t / m 3 ; is the impact velocity of the blasting gas, m / s; The maximum value of the minimum resistance line is 1m< <1.5m.

2. The carbon dioxide phase change directional pressure relief fracturing device for tunneling according to claim 1, characterized in that: The explosion relief head also includes a constant pressure energy relief sheet, which is arranged between the first pipeline and the liquid storage tube and is used to control the carbon dioxide gas to rush to the explosion relief port.

3. The carbon dioxide phase change directional pressure relief fracturing device for tunneling according to claim 2 is characterized in that: A sealing gasket is provided between the filling valve and the liquid storage tube for sealing the inlet of the liquid storage tube.

4. A method for using the carbon dioxide phase change directional pressure relief fracturing device for tunneling as claimed in any one of claims 1 to 3, characterized in that: The method of use comprises the following steps: Step 1, installing a cracking device; Step 2, after step 1 is completed, liquid carbon dioxide is filled into the liquid storage tube by controlling the filling valve; Step 3, inverting at least one fracturing device along the axial direction of the borehole into the borehole of the tunnel to be excavated, wherein the inverted placement means that the explosion relief port of the Y-shaped structure is facing the free surface of the tunnel to be excavated, and the angle between the explosion relief port and the axis of the rotating hole is 30° to 60°; Step 4, heating by controlling the heater to gasify the liquid carbon dioxide in the liquid storage tube; Step 5, when the set pressure is reached in the liquid storage pipe, the carbon dioxide gas breaks through the constant pressure energy release plate and sprays outward along the explosion release port to cause explosion and fracturing.

5. The method for using the carbon dioxide phase change directional pressure relief fracturing device for tunneling according to claim 4, characterized in that: In step 3, the firing lines of the multiple groups of borehole fracturers are connected via detonating cables.

6. The method for using the carbon dioxide phase change directional pressure relief fracturing device for tunneling according to claim 4, characterized in that: The method of use further comprises step 6, cleaning and recovering the fracturing device after step 5 for reuse.

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