A microwave drill bit for deep hard rock borehole-wall-borehole-end drilling while drilling fracturing and a method of use

Abstract

A kind of deep hard rock hole wall-hole end while drilling fracturing microwave drill bit and method, including microwave drill bit, microwave drill bit is successively equipped with support frame front plate, metal sleeve and water inlet ring, metal sleeve is connected with the rotary drive I installed on support frame front plate, microwave drill bit is connected with microwave mode converter and microwave shunt II respectively, microwave mode converter and microwave shunt II are connected with microwave shunt I by rectangular waveguide respectively, microwave shunt I is successively connected microwave rotary joint, fixed waveguide and microwave generating device, microwave rotary joint is connected with the rotary drive II installed on support frame rear plate;Support frame front plate, support frame rear plate and microwave generating device are installed on the equipment mobile platform of fixed base, counterforce support of fixed base is connected between support frame front plate by driving, the present application realizes hard rock fast drilling while hole wall rock mass fracturing release stress, improves the efficiency of microwave stress release technology.

Description

Technical Field

[0001] This invention belongs to the field of geotechnical engineering and mining engineering technology, specifically relating to a microwave drill bit and its method for fracturing the borehole wall and borehole tip in deep hard rock. Background Technology

[0002] Rockburst refers to the sudden release of elastic deformation energy accumulated in stress concentration areas of underground rock masses under excavation and other disturbances, causing the surrounding rock to burst and eject towards the open. Especially as underground engineering progresses to deeper levels, the stress level continuously increases, and the geological environment of the rock mass becomes more complex, making the hazards of rockbursts more severe. Therefore, stress release in high-stress areas is necessary to reduce the risk of rockbursts. Currently, the commonly used stress release method is drilling in high-stress areas. However, drilling is labor-intensive and generates dust and noise, which does not meet environmental protection requirements. Furthermore, improper drilling parameters can lead to difficulty in controlling the stress release effect; excessive drilling can compromise the strength of the surrounding rock, while insufficient drilling can result in poor stress release.

[0003] Microwave-induced fracturing of hard rock is a promising new stress relief technology with advantages such as environmental friendliness and precise fracturing. The method involves first drilling a hole using a conventional drilling rig, then removing the drill rod and inserting a coaxial microwave heater into the hole. Microwaves are emitted around the hole wall, generating numerous cracks. The desired stress relief effect is achieved by adjusting the applied microwave power and time, significantly reducing stress relief within the rock mass. However, this method has some drawbacks: First, conventional drilling rigs are slow when drilling into hard rock; second, it adds an extra step compared to conventional drilling for stress relief; third, drilling first and then inserting the coaxial microwave heater can lead to size mismatches. A hole diameter that is too small or not straight will prevent the heater from being inserted, while a hole diameter that is too large will affect fracturing efficiency.

[0004] Therefore, there is an urgent need to develop equipment that can simultaneously perform drilling and stress release operations, and at the same time achieve simultaneous fracturing of hard rock at the drilling front end to improve drilling efficiency. This would solve the problems of complex procedures, mismatched drilling size, and slow drilling speed in hard rock caused by microwave stress release technology, and enable the promotion and application of microwave stress release technology in engineering. Summary of the Invention

[0005] The purpose of this invention is to provide a microwave drill bit and its method for fracturing the borehole wall and borehole tip in deep hard rock, which can achieve rapid drilling of hard rock while simultaneously fracturing the borehole wall to release stress.

[0006] A microwave drill bit for fracturing deep hard rock borehole walls and borehole ends during drilling includes a microwave drill bit. From back to front, a support frame front plate, a metal sleeve, and a water inlet ring are sequentially mounted on the microwave drill bit. The outer wall of the metal sleeve is connected to a transmission gear of a rotary drive I mounted on the support frame front plate via a gear sleeve. The end face of the metal sleeve and the support frame front plate are in contact with rolling steel balls. The rear end of the microwave drill bit is connected to a microwave mode converter and a microwave splitter II. The microwave mode converter is connected to the microwave output terminal I of the microwave splitter I via a rectangular waveguide, enabling microwave transmission from the rectangular waveguide to a hard coaxial waveguide. The microwave splitter II is connected to the microwave output terminal II of the microwave splitter I via a rectangular waveguide. The microwave input terminal I of the microwave splitter I is connected to one end of a microwave rotary joint. The other end of the microwave rotary joint is connected to one end of a fixed waveguide. The other end of the fixed waveguide is connected to a microwave generator mounted on a moving platform. The joint is located in the through hole at the top of the rear plate of the support frame and rotates within the through hole. The outer wall of the microwave rotary joint is connected to the transmission gear of the rotary drive II mounted on the rear plate of the support frame via a gear sleeve. The microwave rotary joint can achieve lossless rotary transmission of microwaves from the fixed waveguide while rotating itself. The bottom ends of the front plate and the rear plate of the support frame are fixedly mounted on the equipment moving platform. The equipment moving platform is mounted on the fixed base via a directional slide rail. The fixed base is fixed to the ground with screws. A reaction support is fixedly mounted on the right side of the upper surface of the fixed base. The front plate of the support frame and the reaction support are hinged together by a tunneling drive. The tunneling drive passes through the rear plate of the support frame. There are two tunneling drives, which are symmetrically arranged around the rigid coaxial waveguide. The tunneling drive pushes the front plate of the support frame forward through the reaction force of the reaction support, thereby driving the rigid coaxial waveguide to drill forward and simultaneously driving the structure on the equipment moving platform to move forward synchronously.

[0007] The microwave drill bit includes an alloy drill bit. The front end of the alloy drill bit is serrated and contacts the rock mass. The rear end is connected to the front end of a hard coaxial waveguide via a thread. The hard coaxial waveguide acts as a drill rod to provide thrust. The hard coaxial waveguide includes an outer conductor and an inner conductor. The outer conductor is a hollow metal cylinder, and the inner conductor is a solid metal cylinder. The inner conductor is coaxially mounted inside the outer conductor, forming a gap between them. Microwaves are transmitted through this gap. The rear end of the outer conductor is connected to a microwave mode converter.

[0008] Two through holes are drilled axially in the inner conductor of the rigid coaxial waveguide. The through holes are symmetrically arranged around the center of the cross-section of the inner conductor. Soft coaxial waveguides are installed in each through hole, and the diameter of the soft coaxial waveguide is smaller than the radius of the rigid metal inner conductor. The front end of the soft coaxial waveguide passes through the inner conductor of the rigid coaxial waveguide and the alloy drill bit and is connected to the microwave radiator. The front end of the microwave radiator is fitted with a ceramic sleeve fixed to the end face of the alloy drill bit. Microwaves are transmitted through the soft coaxial waveguide, pass through the ceramic sleeve, and then radiate into the rock mass. The ceramic sleeve is transparent to microwaves and its height is less than that of the cutting head. Its function is to prevent drilled rock cuttings from entering the soft coaxial waveguide. The rear end of the soft coaxial waveguide extends to the outside of the inner conductor of the rigid coaxial waveguide and connects to one end of the microwave splitter II.

[0009] The rigid coaxial waveguide outer conductor cuts three hole wall cracks to release microwaves from the rigid coaxial waveguide into the rock mass around the hole wall. In order to ensure that the hole wall cracks can efficiently cut the electromagnetic field, the hole wall cracks are not parallel to the axial and annular directions of the rigid coaxial waveguide, but are arranged in a cross pattern. The crack length is 1 / 4 to 1 / 2 wavelength, and the distance between two adjacent cracks is 1 / 4 to 1 / 2 wavelength.

[0010] A water inlet ring is arranged on the outer wall of the rigid coaxial waveguide. The water inlet ring is a hollow metal sleeve without an inner wall surface. The water inlet ring is embedded in the annular groove on the outer wall of the rigid coaxial waveguide. The connection between the water inlet ring and the annular groove is sealed with rubber. The upper and lower ends of the water inlet ring have two circular holes, which serve as the water outlet and water inlet, respectively. The circular holes are connected to the cooling water tank at the front end of the equipment moving platform through rigid metal water pipes. The water inlet ring advances synchronously with the rigid coaxial waveguide in the horizontal direction, but does not rotate. The rigid coaxial waveguide has two circular holes symmetrically opened along the center surface of the annular groove, which are connected to the cooling channels drilled along the outer conductor of the rigid coaxial waveguide and the alloy drill bit. Cooling water in the cooling water tank flows into the water inlet ring from the water inlet, passes through the cooling channels, and flows out from the water outlet to the cooling water tank.

[0011] The microwave splitter I includes a microwave input terminal I and two microwave output terminals, namely microwave output terminal I and microwave output terminal II. The microwave input terminal I is divided into ten branches, nine of which converge to the microwave output terminal I, and the other branch is connected to the microwave output terminal II. The transmission of microwaves in the branch is controlled by a branch switch, thereby realizing the power distribution between the microwave output terminal I and the microwave output terminal II. The branch switch is an aluminum metal plate.

[0012] The microwave shunt II includes a microwave input terminal II and two microwave output terminals III. The two microwave output terminals III are respectively connected to a soft coaxial waveguide, and the microwave input terminal II is connected to the microwave output terminal II of the microwave shunt I.

[0013] A method for using a microwave drill bit that induces fracturing at the borehole wall and borehole tip in deep hard rock includes the following steps:

[0014] Step 1: Drill a monitoring hole at a distance of 10 - 20 m from the drilling hole, and arrange an in-hole radar damage monitoring device in the monitoring hole. The radar damage monitoring device includes a cylindrical rod body, and a radar signal sensor is arranged at the front end of the cylindrical rod body, which can monitor the rock mass fracture information at a distance above the borehole diameter direction and transmit it to the computer through the signal line in the cylindrical rod body. By moving the radar damage monitoring device axially in the monitoring hole, the crack information around the drilling hole at different drilling depths can be measured;

[0015] Step 2: Select a blank control drilling hole, open the cooling water inlet, start the rotation drive I and rotation drive II 17 and the tunneling drive, do not turn on the microwave generating device, fix the propulsion speed V0 and the drilling speed R0, and monitor the curve of the propulsion force T0 during the propulsion process with respect to the drilling depth. Use the in-hole radar damage monitoring device to test the crack information around the blank control drilling hole;

[0016] Step 3: Select the microwave drilling hole, open the cooling water inlet, start the rotation drive I, rotation drive II and the tunneling drive, open the ten branches of the microwave splitter I, and at the same time turn on the microwave generating device. The microwave power increases continuously. Monitor the microwave reflection power through the reflection power meter, ensure that the microwave reflection coefficient does not exceed the critical reflection power A of the equipment, fix the propulsion speed V0. When the microwave power reaches the maximum value, monitor the propulsion force T1 during the propulsion process and the crack information around the drilling hole;

[0017] Step 4: If at this time the propulsion force T1 < T0 and the number of cracks around the drilling hole increases compared to the condition without microwave, continue to work with these parameters;

[0018] Step 5: If the propulsion force T1 = T0 but the number of cracks around the drilling hole increases, first turn off the microwave generating device and the tunneling drive, and then turn off one branch connected to the microwave output terminal I. This is to increase the proportion of the microwave power allocated to the output terminal II. Turn on the microwave generating device and the tunneling drive, and continuously increase the power, ensure that the microwave reflection coefficient does not exceed the critical reflection power A of the equipment, monitor the propulsion force T1 and the crack information around the drilling hole. If it is impossible to simultaneously achieve T1 < T0 and an increase in the number of cracks around the drilling hole, continue to newly turn off one branch connected to the microwave output terminal I and repeat the operation of Step 5 until T1 < T0 and an increase in the number of cracks around the drilling hole are achieved;

[0019] Step 6: If under the conditions of Step 4 and Step 5, it is still impossible to simultaneously achieve T1 < T0 and an increase in the number of cracks around the drilling hole, reduce the propulsion speed to ensure an increase in the irradiation time for each point, and repeat the operations of Steps 4 - 6 until T1 < T0 and an increase in the number of cracks around the drilling hole are simultaneously achieved.

[0020] The beneficial effects of the present invention adopting the above technical solutions are:

[0021] (1) The structure of the dual-antenna microwave tunneling drill bit is adopted. The hard coaxial waveguide is used as the drill rod. The outer conductor of the hard coaxial waveguide cuts the cross-hole wave slot to release microwaves. The soft coaxial waveguide passes through the inner conductor of the hard coaxial waveguide. This design enables the simultaneous release of microwaves to fracture the rock mass at the front end of the drill bit and the side wall of the drill rod. This not only greatly reduces the difficulty and time of drilling into deep hard rock, but also achieves the effect of high stress release on the side wall. It integrates the originally separate drilling work and microwave stress release work into one, greatly reducing the construction cycle.

[0022] (2) As drilling progresses, the structure of synchronous microwave stress release on the drill rod sidewall avoids the problem of mismatch between the drill hole size and the size of the microwave coaxial waveguide in the hole when drilling first and then microwave cracking of the hole wall. The perfect fit between the drill hole size and the coaxial waveguide not only avoids equipment installation problems, but also greatly reduces microwave dissipation in the air and improves microwave cracking efficiency.

[0023] (3) By switching the branch in the power shunt, the power of the drill bit front end and the drill rod sidewall can be adjusted, so as to achieve the most effective use of microwave power. Attached Figure Description

[0024] Figure 1 The present invention provides an overall structural diagram of a microwave drill bit for drilling-induced fracturing of the borehole wall and borehole tip in deep hard rock.

[0025] Figure 2 This invention relates to a dual-antenna microwave drill bit structure for a microwave drill bit that causes cracking during drilling in deep hard rock boreholes.

[0026] Figure 3 Cross-sectional view of a dual-antenna microwave drill bit for deep hard rock borehole wall-hole end fracture during drilling.

[0027] Figure 4 A schematic diagram of a microwave drill bit for drilling-induced cracking of the borehole wall and borehole tip in deep hard rock.

[0028] Figure 5 The present invention provides a front view of the water inlet ring of a microwave drill bit for drilling-induced fracturing of the borehole wall and borehole tip in deep hard rock.

[0029] Figure 6 This invention provides a microwave shunt I structure for a microwave drill bit that causes fracturing during drilling in deep hard rock boreholes.

[0030] Figure 7 A schematic diagram of the operation of a microwave drill bit for fracturing the borehole wall and borehole tip in deep hard rock according to the present invention.

[0031] 1-Rock strata, 2-Hard coaxial waveguide, 3-Metal sleeve, 4-Microwave mode converter, 5-Rectangular waveguide, 6-Microwave shunt II, 7-Microwave shunt I, 8-Microwave selection joint, 9-Reflection power meter, 10-Fixed waveguide, 11-Microwave generator, 12-Water inlet ring, 13-Cooling water tank, 14-Front plate of support frame, 15-Rotary drive I, 16-Tunneling drive, 17-Rotary drive II, 18-Rear plate of support frame, 19-Equipment moving platform, 20-Fixed base, 21-Reaction support, 2 2-Alloy drill bit, 23-Hard coaxial waveguide outer conductor, 24-Soft coaxial waveguide, 25-Hard coaxial waveguide inner conductor, 26-Outlet, 27-Cooling channel, 28-Inlet, 29-Microwave, 30-Cutting head, 31-Hole wall crack, 32-Groove, 33-Microwave input terminal I, 34-Branch, 35-Branch switch, 36-Microwave output terminal I, 37-Microwave output terminal II, 38-Monitoring hole, 39-Hole radar damage monitoring device, 40-Radar signal sensor, 41-Crack, 42-Drill hole. Detailed Implementation

[0032] The present invention will now be described in further detail with reference to the accompanying drawings and embodiments.

[0033] like Figures 1 to 7As shown, a microwave drill bit for deep hard rock borehole wall-end fracturing during drilling includes a microwave drill bit. From back to front, a support frame front plate 14, a metal sleeve 3, and a water inlet ring 12 are sequentially mounted on the microwave drill bit. The outer wall of the metal sleeve 3 is connected to a transmission gear of a rotary drive I 15 mounted on the support frame front plate 14 via a gear sleeve. The end face of the metal sleeve 3 contacts the support frame front plate 14 using rolling steel balls. The rear end of the microwave drill bit is connected to a microwave mode converter 4 and a microwave splitter II 6, respectively. The microwave mode converter 4 is connected to the microwave... The microwave output terminal I36 of the splitter I7 is connected to the microwave mode converter 4, which enables microwave transmission from the rectangular waveguide 5 to the rigid coaxial waveguide 2. The microwave splitter II6 is connected to the microwave output terminal II37 of the microwave splitter I7 via the rectangular waveguide 5. The microwave input terminal I33 of the microwave splitter I7 is connected to one end of the microwave rotary joint 8. The other end of the microwave rotary joint 8 is connected to one end of the fixed waveguide 10. The other end of the fixed waveguide 10 is connected to the microwave generator 11 mounted on the equipment moving platform 19. The microwave rotary joint 8 is positioned... The microwave rotating joint 8 rotates within the through hole at the top of the rear plate 18 of the support frame. Its outer wall is connected to the transmission gear of the rotating drive II 17 mounted on the rear plate 18 of the support frame via a gear sleeve. The microwave rotating joint 8 can achieve lossless rotational transmission of microwaves from the fixed waveguide 10 while rotating itself. The bottom ends of the front plate 14 and the rear plate 18 of the support frame are fixedly mounted on the equipment moving platform 19. The equipment moving platform 19 is mounted on the fixed base 20 via a directional slide rail. The base 20 is fixed to the ground with screws. A reaction support 21 is fixedly installed on the right side of the upper surface of the base 20. The front plate 14 of the support frame and the reaction support 21 are hinged together by a tunneling drive 16. The tunneling drive 16 passes through the rear plate 18 of the support frame. There are two tunneling drives 16, which are symmetrically arranged around the rigid coaxial waveguide 2. The tunneling drive 16 pushes the front plate 14 of the support frame forward through the reaction force of the reaction support 21, thereby driving the rigid coaxial waveguide 2 to drill forward. At the same time, it drives the structure on the equipment moving platform 19 to move forward synchronously.

[0034] The microwave drill bit is a dual-antenna microwave tunneling drill bit, including an alloy drill bit 22. The front end of the alloy drill bit 22 is serrated and contacts the rock mass 1. The rear end is connected to the front end of a hard coaxial waveguide 2 via a thread. The hard coaxial waveguide 2 acts as a drill rod to provide thrust. The hard coaxial waveguide 2 includes a hard coaxial waveguide outer conductor 23 and a hard coaxial waveguide inner conductor 25. The hard coaxial waveguide outer conductor 23 is a hollow metal cylinder, and the hard coaxial waveguide inner conductor 25 is a solid metal cylinder. The hard coaxial waveguide inner conductor 25 is coaxially installed inside the hard coaxial waveguide outer conductor 23, forming a gap between the hard coaxial waveguide outer conductor 23 and the hard coaxial waveguide inner conductor 25. Microwaves are transmitted through the gap between the hard coaxial waveguide outer conductor 23 and the hard coaxial waveguide inner conductor 25. The rear end of the hard coaxial waveguide outer conductor 23 is connected to a microwave mode converter 4.

[0035] The rigid coaxial waveguide inner conductor 25 has two through holes drilled along the axial direction. The through holes are symmetrically arranged along the center of the cross-section of the rigid coaxial waveguide inner conductor 25. A soft coaxial waveguide 24 is installed in each through hole, and the diameter of the soft coaxial waveguide 24 is smaller than the radius of the rigid metal inner conductor 25. The front end of the soft coaxial waveguide 24 passes through the rigid coaxial waveguide inner conductor 25 and the alloy drill bit 22 and is connected to the microwave radiator. The front end of the microwave radiator is fitted with a ceramic sleeve fixed to the end face of the alloy drill bit 22. The microwave is transmitted through the soft coaxial waveguide 24 and radiates into the rock mass after passing through the ceramic sleeve. The ceramic sleeve is transparent to the microwave and its height is smaller than that of the cutting head. Its function is to prevent the drilled rock cuttings from entering the soft coaxial waveguide 24. The rear end of the soft coaxial waveguide 24 extends to the outside of the rigid coaxial waveguide inner conductor 25 and is connected to one end of the microwave splitter II 6.

[0036] The rigid coaxial waveguide 2 is located in the through hole at the top of the front plate 14 of the support frame and rotates within the through hole of the front plate 14 of the support frame. A metal sleeve 3 with a gear sleeve is arranged on the outer wall of the rigid coaxial waveguide 2, and the inner wall of the metal sleeve 3 is fixedly connected to the rigid coaxial waveguide 2.

[0037] The rotation speeds of the rotary drive I15 and rotary drive II17 are kept at the same. Rotary drive I15 drives the metal sleeve 3 to rotate, and rotary drive II17 drives the microwave rotary joint 8 to rotate, which in turn drives the rigid coaxial waveguide 2, the soft coaxial waveguide 24, the microwave mode converter 4, the rectangular waveguide 5, and the microwave splitters I7 and II6 to rotate together.

[0038] The rigid coaxial waveguide outer conductor 23 cuts three hole wall cracks 31 to release the microwaves 29 of the rigid coaxial waveguide 2 into the rock mass around the hole wall. In order to ensure that the hole wall cracks 31 can efficiently cut the electromagnetic field, the hole wall cracks 31 are not parallel to the rigid coaxial waveguide 2 in the axial and annular directions, but are arranged in a cross pattern. The crack length is 1 / 4 to 1 / 2 wavelength, and the distance between two adjacent cracks is 1 / 4 to 1 / 2 wavelength.

[0039] The rigid coaxial waveguide 2 has a water inlet ring 12 arranged on its outer wall. The water inlet ring 12 is a hollow metal sleeve without an inner wall surface. The water inlet ring 12 is embedded in the annular groove 32 on the outer wall of the rigid coaxial waveguide 2. The connection between the water inlet ring 12 and the annular groove 32 is sealed with rubber. The upper and lower ends of the water inlet ring 12 have two circular holes, which serve as the water outlet 26 and the water inlet 28, respectively. The circular holes are connected to the cooling water tank 13 at the front end of the equipment moving platform 19 through rigid metal water pipes. The water inlet ring 12 advances synchronously with the rigid coaxial waveguide 2 in the horizontal direction, but does not rotate. The rigid coaxial waveguide 2 has two circular holes symmetrically opened along the center surface of the annular groove 32 and is connected to the cooling channel 27 drilled along the outer conductor 23 of the rigid coaxial waveguide and the alloy drill bit 22. Cooling water in the cooling water tank 13 flows into the water inlet ring 12 from the water inlet 28, passes through the cooling channel 27, and flows out from the water outlet 28 to the cooling water tank 13.

[0040] The microwave splitter I7 includes a microwave input terminal I33 and two microwave output terminals, namely microwave output terminal I36 and microwave output terminal II37. The microwave input terminal I33 is divided into ten branches 34, of which nine branches 34 converge to the microwave output terminal I36, and the other branch 34 is connected to the microwave output terminal II37. The transmission of microwaves in the branch 34 is controlled by a branch switch 35, thereby realizing the power distribution between the microwave output terminal I36 and the microwave output terminal II37. The branch switch 35 is an aluminum metal plate.

[0041] The microwave shunt II6 includes a microwave input terminal II and two microwave output terminals III. The two microwave output terminals III are respectively connected to the soft coaxial waveguide 24, and the microwave input terminal II is connected to the microwave output terminal II37 of the microwave shunt I7.

[0042] A method for using a microwave drill bit that induces fracturing at the borehole wall and borehole tip in deep hard rock includes the following steps:

[0043] Step 1: Drill a monitoring hole 38 with a depth of L1m and a diameter of 50cm at a distance of 10-20m from borehole 42. Install an in-hole radar damage monitoring device 39 inside the monitoring hole 38. The radar damage monitoring device 39 includes a cylindrical rod with a radar signal sensor 40 at the front end of the cylindrical rod. It can monitor rock fracture information at a distance of more than 20m in the borehole diameter direction and transmit it to the computer through the signal line inside the cylindrical rod. By moving the radar damage monitoring device 39 along the axial direction of the monitoring hole 38, the crack information around borehole 42 can be measured at different drilling depths.

[0044] Step 2: Select a blank control borehole 42, open the cooling water inlet 28, start the rotary drive I 15, the rotary drive II 17 and the tunneling drive 16, do not turn on the microwave generating device 11, fix the propulsion speed V0 and the drilling speed R0. The propulsion speed V0 and the drilling speed R0 are selected as the parameters commonly used for deep hard rock drilling. Drill to a depth of L2m, where the drilling depth L2 is less than the monitoring hole depth L1. Monitor the curve of the propulsion force T0 during the propulsion process against the drilling depth, and use the borehole radar damage monitoring device 39 to test the crack 41 information around the blank control borehole;

[0045] Step 3: Select the microwave borehole 42, open the cooling water inlet 28, start the rotary drive I 15, the rotary drive II 17 and the tunneling drive 16, open the ten branches 34 of the microwave splitter I 7, and at the same time turn on the microwave generating device 11. Continuously increase the microwave power, monitor the microwave reflection power through the reflection power meter 9, ensure that the microwave reflection coefficient does not exceed the critical reflection power A of the equipment, fix the propulsion speed V0. When the microwave power reaches the maximum value, monitor the propulsion force T1 during the propulsion process and the crack 41 information around the borehole;

[0046] Step 4: If at this time the propulsion force T1 < T0 and the number of cracks 41 around the borehole 42 increases compared to the condition without microwave, continue to work with these parameters;

[0047] Step 5: If the propulsion force T1 = T0 but the number of cracks 41 around the borehole 42 increases, first turn off the microwave generating device 11 and the tunneling drive 16, then turn off one branch 34 connected to the microwave output terminal I 36. This is to increase the proportion of the microwave power allocated to the output terminal II 37. Turn on the microwave generating device 11 and the tunneling drive 16, continuously increase the power, ensure that the microwave reflection coefficient does not exceed the critical reflection power A of the equipment, monitor the propulsion force T1 and the crack 41 information around the borehole 42. If it is impossible to simultaneously achieve T1 < T0 and an increase in the number of cracks 41 around the borehole 42, continue to newly turn off one branch 34 connected to the microwave output terminal I 36 and repeat the operation in Step 5 until T1 < T0 and an increase in the number of cracks 41 around the borehole 42 are achieved;

[0048] Step 6: If under the conditions of Step 4 and Step 5, it is still impossible to simultaneously achieve T1 < T0 and an increase in the number of cracks 41 around the borehole 42, reduce the propulsion speed to ensure an increase in the irradiation time for each point, and repeat the operations in Steps 4 - 6 until T1 < T0 and an increase in the number of cracks 41 around the borehole 42 are simultaneously achieved.

Claims

1. A microwave drill bit for fracturing the borehole wall and borehole tip in deep hard rock, characterized in that, The device includes a microwave drill bit, on which a support frame front plate, a metal sleeve, and a water inlet ring are sequentially mounted from back to front. The outer wall of the metal sleeve is connected to the transmission gear of the rotary drive I mounted on the support frame front plate via a gear sleeve. The metal sleeve and the end face of the support frame front plate are in contact with rolling steel balls. The rear end of the microwave drill bit is connected to a microwave mode converter and a microwave splitter II. The microwave mode converter is connected to the microwave output terminal I of the microwave splitter I via a rectangular waveguide. The microwave mode converter can realize the transmission of microwaves from the rectangular waveguide to the rigid coaxial waveguide. The microwave splitter II is connected to the microwave output terminal II of the microwave splitter I via a rectangular waveguide. The microwave input terminal I of the microwave splitter I is connected to one end of a microwave rotary joint, and the other end of the microwave rotary joint is connected to one end of a fixed waveguide. The other end of the fixed waveguide is connected to a microwave generator mounted on the equipment's moving platform. The microwave rotary joint is located within a through hole at the top of the rear plate of the support frame and rotates within this through hole. The outer wall of the microwave rotary joint is connected to a transmission gear of the rotary drive II mounted on the rear plate of the support frame via a gear sleeve. The microwave rotary joint can achieve lossless rotation of microwaves from the fixed waveguide while rotating itself. The transmission mechanism is as follows: The bottom ends of the front and rear plates of the support frame are fixedly installed on the equipment moving platform. The equipment moving platform is installed on a fixed base via directional slide rails. The fixed base is fixed to the ground with screws. A reaction support is fixedly installed on the right side of the upper surface of the fixed base. The front plate of the support frame and the reaction support are hinged together by a tunneling drive. The tunneling drive passes through the rear plate of the support frame. There are two tunneling drives, which are symmetrically arranged around the rigid coaxial waveguide. The tunneling drive pushes the front plate of the support frame forward through the reaction force of the reaction support, thereby driving the rigid coaxial waveguide to drill forward, and simultaneously driving the structure on the equipment moving platform to move forward synchronously.

2. The microwave drill bit for fracturing deep hard rock borehole walls and borehole ends as described in claim 1, characterized in that: The microwave drill bit includes an alloy drill bit. The front end of the alloy drill bit is serrated and contacts the rock mass. The rear end is connected to the front end of a hard coaxial waveguide via a thread. The hard coaxial waveguide acts as a drill rod to provide thrust. The hard coaxial waveguide includes an outer conductor and an inner conductor. The outer conductor is a hollow metal cylinder, and the inner conductor is a solid metal cylinder. The inner conductor is coaxially mounted inside the outer conductor, forming a gap between them. Microwaves are transmitted through this gap. The rear end of the outer conductor is connected to a microwave mode converter.

3. The microwave drill bit for fracturing deep hard rock borehole walls and borehole ends as described in claim 2, characterized in that: Two through holes are drilled axially in the inner conductor of the rigid coaxial waveguide. The through holes are symmetrically arranged around the center of the cross-section of the inner conductor. Soft coaxial waveguides are installed in each through hole, and the diameter of the soft coaxial waveguide is smaller than the radius of the rigid metal inner conductor. The front end of the soft coaxial waveguide passes through the inner conductor of the rigid coaxial waveguide and the alloy drill bit and is connected to the microwave radiator. The front end of the microwave radiator is fitted with a ceramic sleeve fixed to the end face of the alloy drill bit. Microwaves are transmitted through the soft coaxial waveguide, pass through the ceramic sleeve, and then radiate into the rock mass. The ceramic sleeve is transparent to microwaves and its height is less than that of the cutting head. Its function is to prevent drilled rock cuttings from entering the soft coaxial waveguide. The rear end of the soft coaxial waveguide extends to the outside of the inner conductor of the rigid coaxial waveguide and connects to one end of the microwave splitter II.

4. The microwave drill bit for fracturing the borehole wall and borehole tip in deep hard rock as described in claim 3, characterized in that: The rigid coaxial waveguide outer conductor cuts three hole wall cracks to release microwaves from the rigid coaxial waveguide into the rock mass around the hole wall. In order to ensure that the hole wall cracks can efficiently cut the electromagnetic field, the hole wall cracks are not parallel to the axial and annular directions of the rigid coaxial waveguide, but are arranged in a cross pattern. The crack length is 1 / 4 to 1 / 2 wavelength, and the distance between two adjacent cracks is 1 / 4 to 1 / 2 wavelength.

5. A microwave drill bit for fracturing deep hard rock borehole walls and borehole ends as described in claim 1, characterized in that: A water inlet ring is arranged on the outer wall of the rigid coaxial waveguide. The water inlet ring is a hollow metal sleeve without an inner wall surface. The water inlet ring is embedded in the annular groove on the outer wall of the rigid coaxial waveguide. The connection between the water inlet ring and the annular groove is sealed with rubber. The upper and lower ends of the water inlet ring have two circular holes, which serve as the water outlet and water inlet, respectively. The circular holes are connected to the cooling water tank at the front end of the equipment moving platform through rigid metal water pipes. The water inlet ring advances synchronously with the rigid coaxial waveguide in the horizontal direction, but does not rotate. The rigid coaxial waveguide has two circular holes symmetrically opened along the center surface of the annular groove, which are connected to the cooling channels drilled along the outer conductor of the rigid coaxial waveguide and the alloy drill bit. Cooling water in the cooling water tank flows into the water inlet ring from the water inlet, passes through the cooling channels, and flows out from the water outlet to the cooling water tank.

6. The microwave drill bit for fracturing deep hard rock borehole walls and borehole ends as described in claim 1, characterized in that: The microwave splitter I includes a microwave input terminal I and two microwave output terminals, namely microwave output terminal I and microwave output terminal II. The microwave input terminal I is divided into ten branches, nine of which converge to the microwave output terminal I, and the other branch is connected to the microwave output terminal II. The transmission of microwaves in the branch is controlled by a branch switch, thereby realizing the power distribution between the microwave output terminal I and the microwave output terminal II. The branch switch is an aluminum metal plate.

7. A microwave drill bit for fracturing deep hard rock borehole walls and borehole ends as described in claim 1, characterized in that: The microwave shunt II includes a microwave input terminal II and two microwave output terminals III. The two microwave output terminals III are respectively connected to a soft coaxial waveguide, and the microwave input terminal II is connected to the microwave output terminal II of the microwave shunt I.

8. The method of using a microwave drill bit for fracturing the borehole wall and borehole tip in deep hard rock according to claim 1, characterized in that, Includes the following steps: Step 1: Drill a monitoring hole 10-20m away from the borehole. Install an in-hole radar damage monitoring device inside the monitoring hole. The radar damage monitoring device includes a cylindrical rod with a radar signal sensor at the front end of the cylindrical rod. It can monitor rock fracture information above the borehole diameter and transmit it to a computer through a signal line inside the cylindrical rod. By moving the radar damage monitoring device along the axial direction of the monitoring hole, crack information around the borehole can be measured at different drilling depths. Step 2: Select a blank control borehole, open the cooling water inlet, start the rotary drive I and rotary drive II (17) and the tunneling drive, do not turn on the microwave generating device, fix the propulsion speed V0 and the drilling speed R0, monitor the curve of the propulsion force T0 during the propulsion process against the drilling depth, and use the borehole radar damage monitoring device to test the crack information around the blank control borehole; Step 3: Select the microwave borehole, open the cooling water inlet, start the rotary drive I and rotary drive II and the tunneling drive, open the ten branches of the microwave splitter I, and at the same time turn on the microwave generating device. Continuously increase the microwave power, monitor the microwave reflection power through the reflection power meter, ensure that the microwave reflection coefficient does not exceed the critical reflection power A of the equipment, fix the propulsion speed V0, and when the microwave power reaches the maximum value, monitor the propulsion force T1 during the propulsion process and the crack information around the borehole; Step 4: If at this time the propulsion force T1 < T0 and the number of cracks around the borehole increases compared to the condition without microwave, then continue to work with these parameters; Step 5: If the propulsion force T1 = T0 but the number of cracks around the borehole increases, first turn off the microwave generating device and the tunneling drive, and then turn off one branch connected to the microwave output terminal I. This is to increase the proportion of the microwave power allocated to the output terminal II. Turn on the microwave generating device and the tunneling drive, continuously increase the power, ensure that the microwave reflection coefficient does not exceed the critical reflection power A of the equipment, monitor the propulsion force T1 and the crack information around the borehole. If it is impossible to simultaneously achieve T1 < T0 and an increase in the number of cracks around the borehole, then continue to newly turn off one branch connected to the microwave output terminal I and repeat the operation in Step 5 until T1 < T0 and an increase in the number of cracks around the borehole are achieved; Step 6: If under the conditions of Step 4 and Step 5, it is still impossible to simultaneously achieve T1 < T0 and an increase in the number of cracks around the borehole, reduce the propulsion speed to ensure an increase in the irradiation time for each point, and repeat the operations in Steps 4 - 6 until T1 < T0 and an increase in the number of cracks around the borehole are simultaneously achieved.

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