A safety system and construction method for thermal combustion phase change expansion of rock in blast holes

Abstract

The present invention discloses a safety system for thermal combustion phase change expansion rock splitting in a rock blast hole, which includes a liquid oxygen storage and delivery device, an in-hole device, and a special detonator; the liquid oxygen storage and delivery device includes a liquid oxygen storage tank and a cryogenic infusion pipe connected thereto; the in-hole device includes a sealed cylindrical fracturing pipe filled with liquid-phase carbon dioxide, a thermal combustion component, and sealing clay, and the fracturing pipe, the thermal combustion component, and the sealing clay are filled in the blast hole in sequence from front to back; the fracturing pipe is a sealed cylindrical steel pipe filled with liquid-phase carbon dioxide; the thermal combustion component includes a cylindrical PVC pipe, a thermal combustion structure, and an excitation component. The present invention realizes rock splitting through thermal combustion phase change expansion in a rock blast hole, does not use detonators, electric igniters, electric firewood igniters, etc. involved in explosive blasting, and does not involve easily manufacturable explosive items, and has the characteristics of no pollution, no explosives, no harmful substances, no explosion shock waves, safety and high efficiency, etc.

Description

Technical Field

[0001] The present invention relates to the technical field of engineering rock fracturing, and in particular, to a safety system and construction method for thermal combustion phase change expansion rock fracturing in a rock blast hole. Background Art

[0002] This utility model application technology patent belongs to the technical field of mechanical industry fracturing devices and blasting industry explosive rock fracturing devices, and particularly relates to application technology construction methods for blasting environmental protection, blasting harmful effects, gas blasting devices and advanced scientific environmental protection.

[0003] With the continuous and rapid development of the Chinese economy and the continuous increase of the urbanization process and industrialization process, construction projects first involve earthwork excavation, and explosives are needed for blasting in earthwork excavation. Using explosives to blast rocks is a highly dangerous operation and will bring harmful gases such as vibrations, shock waves, blasting flying rocks, nitrogen oxides after explosive blasting to the environment, and cause damage to surrounding buildings and structures due to blasting vibrations. After statistics, there are more than a thousand similar cases of the consequences of explosive blasting applications in China every year in terms of damage cases and complaint cases caused by blasting. The destructive effect of explosive blasting produces oscillatory seismic effects; the effect of blasting shock waves, whose explosion can release a huge amount of energy instantly, generating high-temperature and high-pressure gases, causing strong oscillations in the surrounding air. Within a certain range from the explosion center, buildings will be damaged or harmed by the shock waves; the splashing impact effect of blasting fragments and blasting flying rocks causes harm to the environment in a quite large range, and the flying range of the fragments of explosive blasting is usually about 100 - 150m; the thermal effect and fire effect, the explosion temperature is about 2000 - 3000°C, and if the surrounding environment involves combustible gases or explosive gases, secondary disaster effects will be produced.

[0004] Developing a rock splitting device, an application of rock splitting technology, and a technical method for reducing environmental pollution and the impact on the environment is very important and necessary for blasting operation units today. Compared with the current technology of blasting rocks using explosives and detonators, the carbon dioxide phase change expansion rock splitting technology has the characteristics of no high temperature, small vibration, no explosion shock wave, basically no pollution, high cost, wide applicability, and no need for blasting administrative permission and blasting operation approval. However, the existing related technologies increase the cost of rock splitting and blasting, with the cost increasing by more than 120% compared to using explosives and detonators for blasting, and the effect completely fails to reach that of explosive blasting. Using the conventional carbon dioxide phase change expansion rock splitting technology for rock splitting and blasting requires a potassium perchlorate and potassium permanganate detonator, and an "ignition agent, heating tube" excitation structure, and an oxidant and a reductant capable of producing a heat reaction need to be available in advance. Commonly used oxidants include sulfur, potassium nitrate, potassium perchlorate, and potassium permanganate, and commonly used reductants include aluminum powder and carbon powder. Among them, potassium nitrate, potassium perchlorate, and potassium permanganate belong to "explosive precursor control items under the Ministry of Public Security of the People's Republic of China". The heating tube used in the application of the carbon dioxide phase change expansion rock splitting technology has the following disadvantages: one is that it contains explosive precursor control items under the Ministry of Public Security; the second is that the heating energy is insufficient and cannot fully excite the phase change liquid carbon dioxide; the third is that the heating tube has an internal device of an electric match head, and the electric match head belongs to the controlled items of civil explosives. Therefore, a heating device that is safe, reliable, has sufficient energy, does not require explosive precursor control items, and does not require an electric match head is needed to generate expanded gaseous carbon dioxide gas and energy in a safe and reliable manner, and to excite liquid carbon dioxide in the safest and most stable way. Summary of the Invention

[0005] The purpose of the present invention is to provide a safe system and method for internal combustion phase change expansion rock splitting in a rock blast hole, generating carbon dioxide gas through internal combustion and using its energy to phase change liquid carbon dioxide, realizing expansion rock splitting, and achieving the effect of reducing environmental pollution and the impact on environmental damage during the construction of rock splitting and rock breaking, so as to solve the problems raised in the above background technology.

[0006] To achieve the above purpose, the present invention provides the following technical solutions:

[0007] A safe system for internal combustion phase change expansion rock splitting in a rock blast hole includes a liquid oxygen storage and delivery device, an in-hole device, and a special detonator;

[0008] The liquid oxygen storage and delivery device includes a liquid oxygen storage tank and a low-temperature infusion pipe connected thereto;

[0009] The in-hole device includes a sealed cylindrical fracturing tube filled with liquid carbon dioxide, an internal combustion component, and sealing clay. The fracturing tube, internal combustion component, and sealing clay are filled in the blast hole in sequence from front to back;

[0010] The fracturing tube is a sealed cylindrical steel pipe filled with liquid-phase carbon dioxide;

[0011] The thermal combustion assembly includes a cylindrical PVC pipe, a thermal combustion structure, and an excitation assembly; the thermal combustion structure is provided with an oxygen injection pipe and a number of carbon sponges connected to the outside thereof. The carbon sponges are cylinders made of sponge-like carbonaceous substances. There is an equal interval between two adjacent carbon sponges. The carbon sponges are connected in series to the outside of the oxygen injection pipe wall. A number of uniformly distributed liquid oxygen discharge holes are provided on the pipe wall of the oxygen injection pipe at the connection part of the carbon sponges; the excitation assembly is arranged in the PVC pipe and is located on the carbon sponges; the two ends of the PVC pipe are respectively provided with an integrally sealed upper end cover and a lower end cover. The upper end cover is provided with an infusion hole and a conductive hole. Among them, the infusion hole is arranged at the center of the upper end cover, and the conductive hole is arranged on one side of the infusion hole; the length of the oxygen injection pipe is greater than the length of the PVC pipe, and its front end extends to the position of the lower end cover of the PVC pipe. Its rear end extends out of the carbon sponges, passes through the infusion hole of the upper end cover, and is detachably connected to the cryogenic infusion pipe;

[0012] The special detonator is used to control the detonation of the thermal combustion assembly from the outside and is electrically connected to the excitation assembly through a wire passing through the conductive hole;

[0013] During operation, liquid oxygen passes through the liquid oxygen storage tank, the cryogenic infusion pipe, and the oxygen injection pipe, and infiltrates into the carbon sponges through the liquid oxygen discharge holes, causing partial gasification of the liquid oxygen. Then, the special detonator is controlled to make the excitation assembly generate sparks, and the carbon sponges in the PVC pipe burn in a high-oxygen environment. The combustion energy causes the fracturing tube sealed with liquid-phase carbon dioxide to crack and the liquid-phase carbon dioxide to rapidly gasify.

[0014] Here, oxygen is cooled and compressed to become liquid oxygen. Liquid oxygen has the characteristics of supporting combustion and rapid expansion. 1.0 kg of liquid oxygen can instantaneously expand and vaporize into 800 liters of oxygen. The oxygen injection pipe serves to connect several carbonaceous sponges in series and consolidate them. The carbonaceous sponges are made of carbonaceous materials such as carbon black, cotton, sponge, or pulp that can absorb liquid oxygen. They can absorb liquid oxygen and are made into a cylindrical shape. The front end of the oxygen injection pipe is used to connect the carbonaceous sponges in a string-of-gourds manner to form a thermal combustion structure. There is an uncoupled gap between adjacent carbonaceous sponges. The thermal combustion structure is installed in a PVC pipe, and the production length of the carbonaceous sponges matches the length of the PVC pipe. By using liquid oxygen, the carbonaceous substances are instantaneously oxidized to generate a large amount of carbon dioxide and water vapor gas, and at the same time, a large amount of heat energy is released. The generated gas reaches a high temperature, and the energy of the high-temperature gas is quickly absorbed by the liquid-phase carbon dioxide fracturing pipe. The liquid-phase carbon dioxide quickly changes into gaseous carbon dioxide. When the liquid-phase carbon dioxide changes into gaseous carbon dioxide, its volume expands by more than 850 times, thereby generating high-pressure gaseous carbon dioxide gas in the blast hole to produce a gaseous dynamic pressure on the rock mass of the blast hole wall, thus achieving the purpose of gas expansion and rock fracturing, and thus achieving the effect of rock fracturing and the engineering purpose.

[0015] Preferably, the excitation component is located in the middle of the PVC pipe and is fixed on the oxygen injection pipe; the wire includes a positive connection metal wire and a negative connection metal wire. One end of the wire penetrates into the PVC pipe to connect the excitation component, and the other end passes out through the conductive hole to connect to a special detonator; the excitation component uses a nickel-chromium alloy resistance heating wire, and the special detonator uses a high-energy capacitive charging instantaneous discharger; one end of the wire is connected to the nickel-chromium alloy resistance heating wire, the other end extends out of the PVC pipe and to 1500 mm outside the blast hole, and is electrically connected to the high-energy capacitive charging instantaneous discharger. Here, an electric spark is generated in the nickel-chromium alloy resistance heating wire through the conduction of the wire, so that the carbonaceous sponge and oxygen are ignited to generate thermal energy. The thermal energy and high-temperature and high-pressure thermal carbon dioxide gas generated in the hole cause a phase change effect on the liquid-phase carbon dioxide fracturing pipe placed at the bottom of the blast hole. The gaseous carbon dioxide from the phase change of the fracturing pipe and the high-temperature and high-pressure thermal carbon dioxide gas excited by the thermal combustion structure act together on the rock of the blast hole wall, causing the rock to produce a swelling and cracking effect, thus achieving the effect of rock fracturing and the engineering purpose.

[0016] To prevent excessive oxygen and excessive pressure and facilitate the discharge and pressure relief of the vaporized liquid oxygen or super-atmospheric liquid oxygen gas during the liquid oxygen perfusion process, preferably, an exhaust hole is provided on the upper end cover. The exhaust hole and the conductive hole are respectively arranged on both sides of the liquid injection hole. The device in the blast hole also includes a pressure relief exhaust pipe for exhausting gas from the PVC pipe. The front end of the pressure relief exhaust pipe extends to the position of the lower end cover of the PVC pipe, and its rear end extends out of the carbonaceous sponge and out of the PVC pipe through the exhaust hole of the upper end cover.

[0017] To prevent the occurrence of sparks due to collisions or other reasons before excitation and ensure the device life and effect, preferably, the PVC pipe is a freeze-resistant ND-PVC pipe; the low-temperature infusion pipe is a heat-resistant soft rubber pipe wrapped with stainless steel wire; the oxygen injection pipe and the pressure relief exhaust pipe are respectively made of aluminum pipes or copper pipes; the liquid oxygen storage tank is a welded adiabatic low-temperature gas cylinder equipped with an automatic thermal pressurization device, that is, a standard and safe liquid oxygen storage tank that complies with the Special Equipment Safety Law and the Cylinder Safety Technical Supervision Regulations.

[0018] Preferably, the safety system further includes a covering explosion-proof blanket, which is made of tire leather and is used for safety covering protection of the rock splitting plane. The covering explosion-proof blanket has a size of 2.0 m in length and 1.2 m in width and is used for safety covering protection of the rock splitting plane.

[0019] To achieve a better rock splitting effect, preferably, after drilling the blast holes, the length of the PVC pipe is 25% - 30% of the blast hole length, the length of the fracturing pipe is 25% - 30% of the blast hole length, and the length of the stuffing and sealing clay is 25% - 30% of the blast hole length.

[0020] The diameter matching of the fracturing pipe and the PVC pipe should be selected according to the diameter of the drilled blast hole. The diameters of the fracturing pipe and the PVC pipe are both slightly smaller than the diameter of the drilled blast hole. Preferably, the fracturing pipe is a steel pipe with both ends closed. When the blast hole diameter is Φ42 - Φ140 mm, the outer diameter of the PVC pipe is configured to be Φ32 - Φ110 mm, the outer diameter of the fracturing pipe is configured to be Φ32 - Φ110 mm, and both are slightly smaller than the blast hole diameter. The diameter of the oxygen injection pipe is Φ5 - Φ15 mm, and the liquid oxygen discharge holes are evenly arranged at intervals of 100 mm - 250 mm along the axial direction of the oxygen injection pipe.

[0021] To better illustrate the present invention, a construction method using the above-mentioned internal combustion phase change expansion rock splitting safety system in rock blast holes is also provided here, which specifically includes the following steps:

[0022] S1. Fabricate a site operation surface platform and a bench working surface platform suitable for this safety system, that is, after conducting a survey of the rock splitting site and the surrounding environment, safety assessment, and expert demonstration, complete the preparation work for the site working platform trimming.

[0023] S2. Use a drilling machine to drill blast holes on the formed bench working surface platform. The selected diameter parameter of the drilled blast holes is Φ42 - Φ140 mm; the drilling depth L is the sum of the height H of the created rock bench working surface and the extra depth h, that is, the drilling depth L = H + h; the number of blast hole rows n ≤ 2 rows, the number of blast holes m in each row ≤ 12, and the inclination angle of the drilled holes is consistent with and parallel to the slope inclination angle of the created bench surface.

[0024] S3. Place the liquid oxygen storage and infusion device on the site operation surface platform.

[0025] S4. Place the sealed cylindrical fracturing tube of liquid-phase carbon dioxide and the thermal combustion assembly in the blast hole from bottom to top. The oxygen injection tube, pressure relief exhaust pipe, and wire are led out to the outside of the blast hole. Then, backfill the blast hole with blast hole plugging and sealing clay,

[0026] S5. Connect the oxygen injection tube of the thermal combustion assembly to the low-temperature infusion tube of the liquid oxygen storage and delivery device. Liquid oxygen is infused into the PVC tube from the liquid oxygen storage tank through the low-temperature infusion tube and the oxygen injection tube using the in-hole liquid oxygen immersion method. When liquid oxygen is discharged from the pressure relief exhaust pipe nozzle, stop filling the liquid oxygen.

[0027] S6. Electrically connect the wire to the special detonator through the main detonating wire.

[0028] S7. Clean the site of the rock fracturing plane and cover it with a protective safety explosion blanket to provide safety coverage for the on-site operation surface platform and the bench working surface platform; set a safety warning radius at a certain distance; energize and detonate the wire and the detonator.

[0029] To avoid human risks and errors and facilitate accurate matching of the liquid oxygen combustion energy required for the phase change of liquid-phase carbon dioxide into gaseous carbon dioxide through experiments, measurements, observations, and calculations, preferably, in step S3, the liquid oxygen storage and delivery device is equipped with a cavitation venturi tube to regulate the liquid oxygen flow rate, a liquid oxygen pump, a pressure reducing valve, a pressure relief valve, and a device to regulate the liquid oxygen flow rate on the infusion tube. The working pressure at the outlet of the liquid oxygen pump, that is, the infusion pressure, is 1.5 MPa, and the working pressures of the pressure reducing valve and the pressure relief valve of the oxygen storage tank are 2.5 MPa. The volume flow rate of the liquid oxygen injected into the PVC tube is supplied according to 35-45% of the volume capacity of the PVC tube; the liquid oxygen storage tank is placed at the working plane position of the drilling platform and is 10 m away from the drilling position; the liquid oxygen storage capacity V of the liquid oxygen storage tank ≤ 499.0 liters, and the maximum total amount used at one time is less than 300 liters.

[0030] Preferably, one end of the fracturing tube is provided with a pressure reducing valve, a pressure relief valve, and a liquid filling pipe mouth with a one-way valve. The liquid filling pipe mouth is used to pre-fill the fracturing tube with liquid-phase carbon dioxide, and the filling pressure is not greater than 7.0 MPa; the working pressure of the liquid-phase carbon dioxide pre-filled into the fracturing tube is 6.5 MPa - 7.0 MPa. The standard calibration values of the pressure reducing valve and the pressure relief valve of the fracturing tube are greater than 7.5 MPa, and the working pressures of the pressure reducing valve and the pressure relief valve are 7.5 MPa. Here, the pressure reducing valve and the pressure relief valve are used to ensure that the air pressure in the fracturing tube will not be too high, and release the gas in time to ensure safety.

[0031] Compared with the prior art, the beneficial effects of the present invention are as follows: The safety system and construction method for thermal combustion phase change expansion of rock in blast holes of the present invention utilize the rapid expansion of liquid oxygen volume and the rapid combustion of carbon and oxygen. Through the thermal combustion-generated hot carbon dioxide, the liquid carbon dioxide in the liquid-phase carbon dioxide fracturing pipe is gasified and undergoes a phase change and expansion, causing the liquid-phase carbon dioxide fracturing pipe to expand and burst. Through the work done by gas expansion, the expansion pressure of carbon dioxide gas in the blast hole is much greater than the tensile strength of the rock, realizing expansion of the rock. It does not use detonators, electric igniters, electric firewood igniters, etc. used in explosive blasting, and does not involve easily manufacturable explosive items, and has the characteristics of pollution-free, no explosives, no harmful substances, no explosion shock waves, safety and high efficiency. This utility model patent is widely applied in industries such as mining, geological exploration, cement, steel, electricity, subway and tunnel and municipal engineering, underwater engineering, and emergency rescue and disaster relief. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] Figure 1 It is a schematic structural diagram of a rock bench working face according to an embodiment of the present invention;

[0033] Figure 2 It is a schematic structural diagram of the overall structure according to an embodiment of the present invention;

[0034] Figure 3 It is a schematic structural diagram of a thermal combustion component according to an embodiment of the present invention;

[0035] Figure 4 It is a flowchart of oxygen filling according to an embodiment of the present invention;

[0036] Figure 5 It is a schematic structural diagram of a lower end cover according to an embodiment of the present invention;

[0037] Wherein: 11. Liquid oxygen storage tank, 12. Cryogenic infusion pipe, 21. Fracturing pipe, 22. Thermal combustion component, 23. Sealing clay, 24. Pressure relief exhaust pipe, 3. Special initiator, 4. PVC pipe, 41. Upper end cover, 42. Lower end cover, 43. Infusion hole, 44. Conductive hole, 45. Exhaust hole, 5. Oxygen injection pipe, 51. Excretory liquid oxygen hole, 6. Carbonaceous sponge, 71. Heating wire, 72. Wire, 74. Initiation main wire, 8. Blast hole. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0038] Next, the technical solutions in the embodiments of the present invention will be clearly and completely described in conjunction with the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without making creative efforts shall fall within the protection scope of the present invention.

[0039] Refer to Figure 1 - Figure 5As shown in the figure, a safety system for internal combustion phase change expansion rock splitting in a rock blast hole 8 includes a liquid oxygen storage and delivery device, an in-hole device, and a special detonator 3;

[0040] The liquid oxygen storage and delivery device includes a liquid oxygen storage tank 11 and a cryogenic infusion pipe 12 connected thereto;

[0041] The in-hole device includes a sealed cylindrical fracturing pipe 21 filled with liquid-phase carbon dioxide, a thermal combustion assembly 22, and sealing clay 23. The fracturing pipe 21, the thermal combustion assembly 22, and the sealing clay 23 are filled in the blast hole 8 in sequence from front to back; the sealing clay 23 is a clay body formed by adding water to ordinary loess to make it moist;

[0042] The fracturing pipe 21 is a sealed cylindrical steel pipe filled with liquid-phase carbon dioxide;

[0043] The thermal combustion assembly 22 includes a cylindrical PVC pipe 4, a thermal combustion structure, and an excitation assembly; the thermal combustion structure is provided with an oxygen injection pipe 5 and a number of carbonaceous sponges 6 connected to the outside thereof. The carbonaceous sponges 6 are cylinders made of sponge-like carbonaceous substances. There are equal intervals between two adjacent carbonaceous sponges 6. The carbonaceous sponges 6 are connected in series on the outer wall of the oxygen injection pipe 5. A number of uniformly distributed liquid oxygen discharge holes 51 are provided on the wall of the oxygen injection pipe 5 at the connection part of the carbonaceous sponges 6; the excitation assembly is arranged in the PVC pipe 4 and is located on the carbonaceous sponges 6; both ends of the PVC pipe 4 are respectively provided with an integrally sealed upper end cover 41 and a lower end cover 42. The upper end cover 41 is provided with an infusion hole 43 and a conductive hole 44. Among them, the infusion hole 43 is arranged at the center of the upper end cover 41, and the conductive hole 44 is arranged on one side of the infusion hole 43; the length of the oxygen injection pipe 5 is greater than the length of the PVC pipe 4. Its front end extends to the position of the lower end cover 42 of the PVC pipe 4, and its rear end extends out of the carbonaceous sponges 6, passes through the infusion hole 43 of the upper end cover 41, and is detachably connected to the cryogenic infusion pipe 12;

[0044] The special detonator 3 is used to control the detonation of the thermal combustion assembly 22 from the outside and is electrically connected to the excitation assembly through a wire 72 passing through the conductive hole 44;

[0045] During operation, liquid oxygen passes through the liquid oxygen storage tank 11, the cryogenic infusion pipe 12, and the oxygen injection pipe 5, and infiltrates into the carbonaceous sponges 6 through the liquid oxygen discharge holes 51, causing partial gasification of the liquid oxygen. Then, the special detonator 3 is controlled to make the excitation assembly generate a spark. The carbonaceous sponges 6 in the PVC pipe 4 burn violently in a high-oxygen environment, and the combustion energy causes the fracturing pipe 21 storing liquid-phase carbon dioxide in a sealed manner to crack and the liquid-phase carbon dioxide to quickly gasify.

[0046] Here, oxygen is cooled and compressed to become liquid oxygen. Liquid oxygen has the characteristics of supporting combustion and rapid expansion. 1.0 kg of liquid oxygen can instantaneously expand and vaporize into 800 liters of oxygen. The oxygen injection pipe 5 serves to connect several carbonaceous sponges 6 in series and consolidate them. The carbonaceous sponge 6 is made of carbonaceous materials such as carbon black, cotton, sponge, or pulp that can absorb liquid oxygen. It can absorb liquid oxygen and is made into a cylindrical shape. The front end of the oxygen injection pipe 5 connects the carbonaceous sponges 6 in a string-of-gourds manner to form a thermal combustion structure. There are uncoupled spacer gaps between adjacent carbonaceous sponges 6. The thermal combustion structure is placed in the PVC pipe 4, and the manufacturing length of the carbonaceous sponge 6 matches the length of the PVC pipe 4. By using liquid oxygen to instantaneously oxidize carbonaceous substances to generate a large amount of carbon dioxide and water vapor gas, and at the same time release a large amount of heat energy, the generated gas reaches a high temperature. The energy of the high-temperature gas is quickly absorbed by the liquid-phase carbon dioxide fracturing pipe 21. The liquid-phase carbon dioxide quickly changes phase into gaseous carbon dioxide. When the liquid-phase carbon dioxide changes phase into gaseous carbon dioxide, its volume expands by more than 850 times. Thus, high-pressure gaseous carbon dioxide gas is generated in the blast hole 8 to generate gaseous dynamic pressure on the rock mass of the blast hole 8 wall, thereby achieving the purpose of gas expansion and rock fracturing, and thus achieving the effect of rock fracturing and the engineering purpose.

[0047] The excitation component is located in the middle of the PVC pipe 4 and is fixed on the oxygen injection pipe 5. The wire 72 includes positive and negative connecting metal wires. One end penetrates into the PVC pipe 4 to connect the excitation component, and the other end passes out through the conductive hole 44 to connect to the special detonator 3. The excitation component uses a nickel-chromium alloy resistance heating wire 71. The special detonator 3 uses a high-energy capacitive charging instantaneous discharger, which is a 2000-volt high-energy pulse discharger material and belongs to the detonator materials produced in line with national standards. One end of the wire 72 is connected to the nickel-chromium alloy resistance heating wire 71, the other end extends out of the PVC pipe 4 and reaches 1500 mm outside the blast hole 8, and is electrically connected to the high-energy capacitive charging instantaneous discharger. Here, an electric spark is generated in the nickel-chromium alloy resistance heating wire 71 through the conduction of the wire 72, so that the carbonaceous sponge 6 and oxygen are ignited to generate thermal energy. The thermal energy and the high-temperature and high-pressure thermal carbon dioxide gas generated in the hole cause a phase change effect on the liquid-phase carbon dioxide fracturing pipe 21 placed at the bottom of the blast hole 8. The gaseous carbon dioxide after the phase change of the fracturing pipe 21 and the high-temperature and high-pressure thermal carbon dioxide gas excited by the thermal combustion structure act together on the rock of the blast hole 8 wall, causing the rock to produce a swelling fracture effect, thereby achieving the effect of rock fracturing and the engineering purpose.

[0048] To prevent excessive oxygen and pressure and facilitate the discharge and pressure relief of the vaporized liquid oxygen or the liquid oxygen gas under superatmospheric pressure during the perfusion of liquid oxygen, an exhaust hole 45 is provided on the upper end cap 41. The exhaust hole 45 and the conductive hole 44 are respectively arranged on both sides of the liquid infusion hole 43. The device 2 placed inside the blast hole further includes a pressure relief exhaust pipe 24 for exhausting gas from the PVC pipe 4. The front end of the pressure relief exhaust pipe 24 extends to the position of the lower end cap 42 of the PVC pipe 4, its rear end extends out of the carbonaceous sponge 6, and extends out of the PVC pipe 4 through the exhaust hole 45 of the upper end cap 41 to the outside of the PVC pipe 4.

[0049] To prevent the occurrence of sparks due to collisions or other reasons before excitation and ensure the service life and effect of the device, the PVC pipe 4 is made of freeze-resistant ND-PVC pipe; the cryogenic liquid infusion pipe 12 is a heat-resistant flexible rubber pipe wrapped with stainless steel wire; the oxygen injection pipe 5 and the pressure relief exhaust pipe 24 are respectively made of aluminum pipes or copper pipes; the liquid oxygen storage tank 11 is a welded adiabatic cryogenic gas cylinder equipped with an automatic thermal pressurization device, that is, a standard and safe liquid oxygen storage tank 11 that complies with the Special Equipment Safety Law and the Safety Technical Supervision Regulations for Gas Cylinders.

[0050] The safety system further includes a covering explosive quilt. The covering explosive quilt is made of tire leather woven for safety covering and protection of the rock splitting plane. The size of the covering explosive quilt is 2.0 m in length and 1.2 m in width, and is used for safety covering and protection of the rock splitting plane.

[0051] At the construction site of the rock splitting project, the rock splitting work area is a construction rock splitting site with a length of 105 m and a width of 35 m. The project is a foundation pit excavation construction project for a subway marshalling station. The construction method of the internal combustion phase change expansion rock splitting safety system in the rock blast hole 8 is specifically as follows:

[0052] S1. Conduct an investigation, safety assessment, and expert demonstration on the site and surrounding environment of the construction project of this rock splitting project, complete the preparation work for the dressing of the working platform of the site, use mechanical chiseling for leveling, create a rock layer step working surface and a drilling platform plane. The step working surface and the drilling platform plane are 105 m in length and 35 m in width, which is consistent with the area of the construction rock splitting site. The working height of the rock layer step is 9.0 m. The slope angle of the formed step working surface is 85°.

[0053] S2. Use a drilling machine to drill blast holes 8 on the platform with a length of 105 m and a width of 35 m of the created rock working surface. The diameter parameter of the drilled blast holes 8 is Φ90 mm; the depth L of the drilled blast holes 8 is 9.5 m; the number of rows n of the blast holes 8 is 2 rows; the number of holes m in each row of blast holes 8 is 8; the inclination angle of the drilled holes is consistent with and parallel to the slope angle of 85° of the step working surface; the hole spacing of the drilled blast holes 8 is 2.0 m, and the hole row spacing of the drilled blast holes 8 is 1.8 m; the total number of blast holes 8 is 16.

[0054] S3. The liquid oxygen storage and transportation device 1 is placed on a platform with a length of 105 m and a width of 35 m at the on-site working face. The liquid oxygen storage tank 11 is placed at the working plane position of the drilling platform and is 10 m away from the drilling position. The liquid oxygen storage capacity V of the liquid oxygen storage tank 11 is 499.0 liters. Fabricate the in-hole device 2: The diameter of the purchased sealed cylindrical fracturing tube 21 of liquid-phase carbon dioxide and the diameter of the fabricated cylindrical PVC tube 4 are both Φ80 mm; the length of the purchased sealed cylindrical fracturing tube 21 of liquid-phase carbon dioxide is 2.8 m; the length of the cylindrical PVC tube 4 in the fabricated in-hole device 2 is 4.0 m. The oxygen injection tube 5 in the heat combustion structure inside the cylindrical PVC tube 4 is provided with 10 groups of liquid discharge holes with an equal distance of 100 mm, each group of liquid discharge holes includes 2 liquid discharge holes, and the diameter Φ of each liquid discharge hole is 2 mm, that is, 20 liquid discharge holes are set; the carbonaceous sponge 6 in the heat combustion structure inside the cylindrical PVC tube 4 has a diameter Φ of 75 mm and a length of 4.0 m. A total of 5 sections of carbonaceous sponge 6 are designed, the length of each section of carbonaceous sponge 6 is 0.6 m, and the interval gap between each section of carbonaceous sponge 6 is 25 mm.

[0055] S4. Place the sealed cylindrical fracturing tube 21 of liquid-phase carbon dioxide and the heat combustion assembly 22 from the bottom to the top inside the blast hole 8. The oxygen injection tube 5, the pressure relief exhaust pipe 24, and the wire 72 are led out 1.5 m outside the blast hole 8 opening. Then, backfill and tamp the blast hole 8 with the blast hole plugging and sealing clay 23, and the tamping length of the blast hole plugging and sealing clay 23 for the blast hole 8 is 2.7 m. The diameters of the adopted oxygen injection tube 5 and the pressure relief exhaust pipe 24 are Φ8 mm and Φ5 mm respectively. After the above work is completed, connect the oxygen injection tube 5 to the liquid oxygen storage and transportation device 1, and the low-temperature infusion tube 12 fills the in-hole device 2 with liquid oxygen. After observing the liquid oxygen discharged from the nozzle of the pressure relief exhaust pipe 24, stop the liquid oxygen filling work. The liquid oxygen consumption this time is 249.5 liters.

[0056] S6. After the above work is completed, connect the wire 72 to the main detonation wire 74 to the special detonator 3.

[0057] S7. Clean the rock splitting plane site and cover it with explosion-proof covers. Each explosion-proof cover has a size of 2.0 m in length and 1.2 m in width, and conduct safety covering protection for the rock splitting operation surface (including the on-site operation surface platform and the bench working surface platform); set a safety warning radius of 100 m; energize and trigger the wire 72 and the detonator for detonation.

[0058] S8. After detonation, high-temperature heat energy and hot high-pressure carbon dioxide are suddenly generated inside the blast hole 8, achieving the effect of carbon dioxide gas expanding and splitting the rock.

[0059] Taking the experimental sandstone as an example, the specific gravity of the measured rock is 2.91 g / cm3, the compressive strength of the measured rock is 160 MPa, the tensile strength of the measured rock is 4.5 MPa, the static elastic modulus is 86.0 GPa. The dynamic peak pressure of the phase change of liquid carbon dioxide into gaseous carbon dioxide in the experimental measurement of blast hole 8 is 86.7 MPa. The dynamic peak pressure of gaseous carbon dioxide is much greater than the tensile strength of the rock and less than the compressive strength of the rock. Therefore, the high-pressure gaseous carbon dioxide generated in the hole can expand and fracture the rock, achieving the effect of rock fracturing, and at the same time, it will not cause the adverse effect of explosive blasting to crush the rock.

[0060] Due to the powerful explosion shock wave, explosion stress wave, temperature exceeding 3000 °C, and explosion high pressure exceeding 1000 MPa generated by explosive blasting, explosive blasting can crush the rock and produce possible blasting hazard effects. The pressure generated by the phase change of liquid carbon dioxide into gaseous carbon dioxide using the liquid oxygen thermal combustion energy of this device is less than the compressive strength of the rock, and there is no effect of explosion shock wave, only the "tire burst gas shock wave and sound effect". Therefore, its harm to the surrounding environment is much smaller than that of explosive blasting. The rock fracturing by this device will not generate powerful shock waves, vibration waves, harmful and toxic gases, etc. like explosive blasting.

[0061] Although the embodiments of the present invention have been shown and described, for those of ordinary skill in the art, it can be understood that various changes, modifications, substitutions, and variations can be made to these embodiments without departing from the principles and spirit of the present invention. The scope of the present invention is defined by the appended claims and their equivalents.

Claims

1. A safety system for thermal combustion phase change expansion rock splitting in a rock blast hole, characterized in that, It includes a liquid oxygen storage and transportation device, a device placed inside the blast hole, and a special detonator; The liquid oxygen storage and transportation device includes a liquid oxygen storage tank and a cryogenic infusion pipe connected thereto; The device placed inside the blast hole includes a sealed cylindrical fracturing pipe filled with liquid-phase carbon dioxide, a thermal combustion component, and sealing clay. The fracturing pipe, the thermal combustion component, and the sealing clay are filled in the blast hole in sequence from the front to the back; The fracturing pipe is a sealed cylindrical steel pipe filled with liquid-phase carbon dioxide; The thermal combustion component includes a cylindrical PVC pipe, a thermal combustion structure, and an excitation component; the thermal combustion structure is provided with an oxygen injection pipe and a number of carbon sponges connected to the outside thereof. The carbon sponges are cylinders made of sponge-like carbonaceous substances. There are equal intervals between two adjacent carbon sponges. The carbon sponges are connected in series on the outer wall of the oxygen injection pipe. A number of uniformly distributed liquid oxygen discharge holes are provided on the wall of the oxygen injection pipe at the connection part of the carbon sponges; the excitation component is arranged inside the PVC pipe and located on the carbon sponges; one-piece sealed upper and lower end caps are respectively provided at both ends of the PVC pipe. An infusion hole and a conductive hole are provided on the upper end cap. Among them, the infusion hole is arranged at the center of the upper end cap, and the conductive hole is arranged on one side of the infusion hole; the length of the oxygen injection pipe is greater than the length of the PVC pipe. Its front end extends to the position of the lower end cap of the PVC pipe, and its rear end extends out of the carbon sponges, passes through the infusion hole of the upper end cap, and is detachably connected to the cryogenic infusion pipe; The special detonator is used to control the detonation of the thermal combustion component from the outside and is electrically connected to the excitation component through a wire passing through the conductive hole; During operation, liquid oxygen enters the carbon sponges through the cryogenic infusion pipe and the oxygen injection pipe and immerses through the liquid oxygen discharge holes, causing partial gasification of the liquid oxygen. Then, the special detonator is controlled to make the excitation component generate a spark. The carbon sponges inside the PVC pipe burn under a high-oxygen environment, and the combustion energy causes the fracturing pipe sealed with liquid-phase carbon dioxide to crack and the liquid-phase carbon dioxide to rapidly gasify.

2. The security system according to claim 1, wherein The excitation component is located in the middle of the PVC pipe and fixed on the oxygen injection pipe; the wire includes a positive connection metal wire and a negative connection metal wire. One end of the wire penetrates into the PVC pipe to connect the excitation component, and the other end passes through the conductive hole and is connected to the special detonator; the excitation component uses a nickel-chromium alloy resistance heating wire, and the special detonator uses a high-energy capacitive charging instantaneous discharger; one end of the wire is connected to the nickel-chromium alloy resistance heating wire, and the other end extends out of the PVC pipe to the outside of the blast hole and is electrically connected to the high-energy capacitive charging instantaneous discharger.

3. The security system according to claim 1, wherein, An exhaust hole is provided on the upper end cap. The exhaust hole and the conductive hole are respectively arranged on both sides of the infusion hole. The device placed inside the blast hole also includes a pressure relief exhaust pipe for exhausting gas from the PVC pipe. The front end of the pressure relief exhaust pipe extends to the position of the lower end cap of the PVC pipe, and its rear end extends out of the carbon sponges and extends out of the PVC pipe through the exhaust hole of the upper end cap.

4. The security system according to claim 3, wherein The PVC pipe uses a freeze-resistant ND-PVC pipe; the low-temperature infusion pipe uses a heat-resistant soft rubber pipe wrapped with stainless steel wire; the oxygen injection pipe and the pressure relief exhaust pipe respectively use aluminum pipes or copper pipes; the liquid oxygen storage tank uses a welded adiabatic cryogenic gas cylinder with an automatic heating device.

5. The security system according to claim 4, wherein The safety system further includes an explosion covering quilt, and the explosion covering quilt is made of tire leather.

6. The security system according to claim 4, characterized in that, After the blast holes are drilled, the length of the PVC pipe is 25% - 30% of the blast hole length, the length of the fracturing pipe is 25% - 30% of the blast hole length, and the length of the plugging and sealing clay is 25% - 30% of the blast hole length.

7. The security system according to claim 4, characterized in that, The fracturing pipe is a steel pipe with both ends closed. When the blast hole diameter is Φ42 - Φ140mm, the outer diameter of the PVC pipe is configured to be Φ32 - Φ110mm, the outer diameter of the fracturing pipe is configured to be Φ32 - Φ110mm, and both are slightly smaller than the blast hole diameter. The diameter of the oxygen injection pipe is Φ5 - Φ15mm, and the liquid oxygen discharge holes are evenly arranged at intervals of 100mm - 250mm along the axial direction of the oxygen injection pipe.

8. A construction method using the safety system according to any one of claims 3 - 7, specifically including the following steps: S1. Fabricate a site operation surface platform and a bench working surface platform suitable for this safety system. S2. Use a drilling machine to drill blast holes on the formed bench working surface platform. The selected diameter parameter of the drilled blast holes is Φ42 - Φ140mm; the depth L of the drilled blast holes is the sum of the height H of the created rock bench working surface and the excess depth h, that is, the drilling depth L = H + h; the number of rows of blast holes n ≤ 2 rows, the number of blast holes m in each row ≤ 12, and the inclination angle of the drilling is consistent with and parallel to the slope inclination angle of the created bench surface. S3. Place the liquid oxygen storage and delivery device on the site operation surface platform. S4. Place the closed cylindrical fracturing pipe of liquid phase carbon dioxide and the thermal combustion component from the bottom to the top in the blast hole; lead the oxygen injection pipe, the pressure relief exhaust pipe, and the wire out of the blast hole opening; then, backfill the blast hole with blast hole plugging and sealing clay. S5. Connect the oxygen injection pipe of the thermal combustion component to the low-temperature infusion pipe of the liquid oxygen storage and delivery device. Liquid oxygen is infused into the PVC pipe from the liquid oxygen storage tank through the low-temperature infusion pipe and the oxygen injection pipe by the in-hole liquid oxygen immersion method. When liquid oxygen is discharged from the pressure relief exhaust pipe nozzle, stop filling liquid oxygen. S6. Electrically connect the wire to a special detonator through the detonation main line. S7. Clean the fractured rock plane site and cover it with an explosion covering quilt to provide safety covering protection for the site operation surface platform and the bench working surface platform; set a certain distance as the safety warning radius; energize and detonate the wire and the special detonator.

9. The construction method according to claim 8, characterized in that, In step S3, the liquid oxygen storage and transportation device is equipped with a cavitation venturi on the low-temperature infusion pipe, and is configured with a liquid oxygen pump, a pressure reducing valve, a pressure relief valve, and a liquid oxygen flow regulator. The working pressure at the outlet of the liquid oxygen pump, that is, the infusion pressure, is 1.5 MPa. The working pressures of the pressure reducing valve and the pressure relief valve of the liquid oxygen storage and transportation device are 2.5 MPa. The volume flow rate of the liquid oxygen injected into the PVC pipe is supplied according to 35-45% of the volume of the PVC pipe. The liquid oxygen storage tank is placed at the working plane position of the on-site operation surface and is 10 m away from the drilling position. The liquid oxygen storage volume V of the liquid oxygen storage tank is ≤ 499.0 liters, and the maximum total amount used at one time is less than 300 liters. One end of the fracturing pipe is provided with a pressure reducing valve, a pressure relief valve, and a liquid filling pipe orifice with a check valve. The liquid filling pipe orifice is used to pre-fill the fracturing pipe with liquid-phase carbon dioxide, and the filling pressure is not greater than 7.0 MPa. The working pressure of the liquid-phase carbon dioxide pre-filled into the fracturing pipe is 6.5 MPa to 7.0 MPa. The standard calibration values of the pressure reducing valve and the pressure relief valve of the fracturing pipe are greater than 7.5 MPa, and the working pressures of the pressure reducing valve and the pressure relief valve of the fracturing pipe are 7.5 MPa.

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