A local fracturing pressure relief and modification device for deep hard rock engineering and its use method

Abstract

The present invention discloses a local fracturing pressure relief and modification device for deep hard rock engineering and a method for using the device. The device is composed of a plunger-type fracturing rod, a high-pressure water pump, a motor, an external water source, a hydraulic system and an external power supply; the plunger-type fracturing rod is composed of a plunger splitting rod body and a plunger-type hydraulic fracturing unit, a high-pressure water jet unit and a rotary controller. When the device is working, the plunger pressurization and the high-pressure water jet work simultaneously, causing the rock on the borehole wall to crack and expand under the combined action of tensile stress and water pressure, forming a fracture zone around the rock mass to be excavated, inducing regional stress and energy release and hard rock modification. The present invention has the advantages of simple structure, easy operation, strong controllability, high operating precision, and higher efficiency of pressure relief effect on hard rock.

Description

Technical Field

[0001] The present invention relates to the field of deep mining of hard rock deposits and the field of rock burst disaster prevention and control in deep hard rock engineering, and in particular to a local fracturing pressure relief and modification device for deep hard rock engineering and a use method thereof. Background Art

[0002] With the progress and development of society, human beings have an increasingly urgent need for space and resources. Underground rock engineering projects such as tunnels, hydropower stations, waste storage, and mines are gradually extending deep into the earth. However, with the rapid advancement of rock engineering projects into the depths, rock burst disasters frequently occur, which are manifested as the violent release of rock energy and the high-speed ejection of rock fragments from the air surface, seriously threatening the safety of workers and equipment.

[0003] Compared with other engineering disasters, the occurrence of deep engineering rockburst disasters has its own particularity, which is mainly reflected in: (1) the hard and brittle characteristics of deep hard rock (high energy storage capacity and high rockburst tendency); (2) the high stress and high energy storage of the rock mass caused by the great burial depth provide the energy source for rockburst; (3) the strong disturbance caused by drilling and blasting excavation is the key inducing factor of rockburst. The prevention and control of rockburst follows the principle of "prevention first, prevention and control combined". At present, the main ideas for preventing rockburst are stress (energy) regulation, rock mass modification, and power source optimization (short footage weak blasting, mechanical excavation, etc.). The specific measures mainly include pressure relief blasting, drilling pressure relief holes, hydraulic fracturing, water injection, etc., which have achieved certain results, but there are still many disadvantages. For example, pressure relief blasting itself will cause disturbance of the surrounding rock and waste of explosives; the effect of drilling pressure relief holes is minimal in practice; for deep hard rock, hydraulic fracturing requires extremely high water pressure, safety is difficult to guarantee, and the expansion of fracturing cracks is difficult to control. At the same time, the sealing effect is required to be high, which is difficult to achieve; water injection has been widely used in coal mines, but due to the density of hard rock, the effective injection depth is difficult to guarantee. In addition, patent CN111927470 B invented a microwave-assisted pressure relief method for deep hard rock engineering, which uses microwave waveguides to introduce microwave radiation energy into the bottom of the borehole and irradiate the rock mass to produce cracks, inducing energy release; patent CN113217009 B authorizes a microwave gain type CO2 phase change pressure relief method for preventing rock bursts. The above two methods require the use of microwave equipment, which consumes a lot of energy and has poor fracturing efficiency, which is contrary to the green economy principle advocated by modern industry.

[0004] Therefore, in order to cope with the threat of rock burst disasters caused by the further increase in the burial depth of deep hard rock engineering, it is urgent to invent a safe, efficient and economical rock burst prevention and control method and equipment. Summary of the invention

[0005] In view of the problems existing in the above-mentioned prior art, the present invention discloses a local fracturing and pressure relief and hard rock modification device for deep hard rock engineering and a method for using the same, and the present invention adopts the following technical solutions to achieve the above-mentioned problems:

[0006] The present invention provides a local fracturing, pressure relief and modification device for deep hard rock engineering, which is composed of a plunger-type fracturing rod, a high-pressure water pump, an electric motor, an external water source, a hydraulic system and an external power supply; the plunger-type fracturing rod is composed of a plunger splitting rod body and a plunger-type hydraulic fracturing unit, a high-pressure water jet unit and a rotation controller; the plunger-type splitting rod is connected to the high-pressure water pump through a high-pressure water pipe, the high-pressure water pump provides high-pressure water for the high-pressure water jet unit, the plunger-type splitting rod is connected to the hydraulic system through an oil inlet pipe and an oil return pipe, the hydraulic system provides hydraulic power for the plunger-type hydraulic fracturing unit, and the external power supply and the electric motor provide driving force for the high-pressure water pump.

[0007] Furthermore, one end of the plunger-type fracturing rod body is provided with two symmetrically arranged water injection ports, an oil inlet pipe, an oil return pipe and a hollow lifting rod, a flat cavity is provided in one end of the plunger-type fracturing rod body close to the water injection port, plunger placement grooves sunken into the rod body are evenly arranged on the plunger-type fracturing rod body, and arc-shaped nozzle rotation grooves are symmetrically arranged on both sides of the plunger placement groove; an oil injection cavity and a water injection cavity are provided inside the plunger-type fracturing rod body, the water injection cavity is isolated from the oil injection cavity and the plunger placement groove to prevent seepage, the oil injection cavity is connected to the hydraulic system through the oil inlet pipe and the oil return pipe, the oil inlet pipe and the oil return pipe are respectively installed with control valves, and the water injection port is connected to the high-pressure water pump through a high-pressure water pipe.

[0008] Furthermore, the plunger type hydraulic fracturing unit comprises a plunger top block and a plunger push rod, the plunger top block and the plunger push rod are installed in the plunger placement groove, the plunger push rod is connected and fixed to the tail of the plunger top block, a spring is connected between the tail of the plunger push rod and the plunger type fracturing rod body, the tail of the plunger push rod isolates the plunger placement groove close to the oil injection cavity to form an oil chamber, the oil injection cavity and the oil chamber are connected through an oil inlet, the plunger push rod is in anti-seepage and sealed coupling contact with the plunger placement groove, and the plunger push rod can drive the plunger top block to move in the plunger placement groove under the power of the hydraulic oil; when the plunger type hydraulic fracturing unit is working, the hydraulic system is turned on, the oil inlet pipe control valve is opened, and the oil return pipe control valve is closed, and the hydraulic oil enters the oil chamber through the oil inlet pipe, the oil injection cavity and the oil inlet, The plunger push rod and the plunger top block are pushed toward the borehole rock wall, the spring is stretched, and the plunger top block acts on the borehole rock wall to apply pressure to the borehole rock wall for fracturing; when the fracturing pressure relief is completed, the return oil pipe control valve is opened, the oil inlet pipe control valve is closed, the hydraulic system is depressurized, and the hydraulic oil is discharged through the return oil pipe. The plunger top block and the plunger push rod are then retracted into the plunger placement groove under the action of the spring contraction.

[0009] Furthermore, the high-pressure water jet unit includes a nozzle, which is evenly fixedly connected to the water injection cavity. The nozzle corresponds to the position of the arc-shaped nozzle rotation groove on the plunger splitting rod body one by one, and the nozzle extends out of the plunger splitting rod body through the nozzle rotation groove. When the high-pressure water jet unit is working, the nozzle is rotated to the fracture damage area of ​​the hole wall, and the high-pressure pump is turned on to allow water from the external water source to enter the water injection cavity through the high-pressure water pipe and the water injection port, and the high-pressure water beam is sprayed from the nozzle to impact the fracture damage area of ​​the hole wall, thereby promoting the generation and expansion of cracks.

[0010] Furthermore, the rotary controller includes a control gear, a gear shaft and a matching motor. The control gear is installed in the cavity inside the plunger-type fracturing rod. The control gear is connected and fixed to one end of the gear shaft. The gear shaft passes through a hollow lifting rod. The other end of the gear shaft is connected to the matching motor. The control gear is connected to the rotating tooth root on the water injection cavity through a chain. When the nozzle needs to be rotated, the matching motor is started, and the control gear, chain and rotating tooth root are driven to rotate through the gear shaft, thereby driving the water injection cavity and the nozzle to rotate. When the nozzle rotates to the designed hole wall fracture damage area, the matching motor is turned off and the nozzle is fixed. The matching motor is a small motor, and the connection between the matching motor and the gear shaft is detachable. When the device of the present invention is working, the matching motor can be always installed on the gear shaft, and can also be installed on the gear shaft when the nozzle needs to be rotated. When the nozzle does not need to rotate, the matching motor is removed.

[0011] Furthermore, the water injection cavity is symmetrically arranged on both sides of the plunger splitting rod body, and the water injection cavity and the water injection port are tightly connected through a rotating bearing; rotating bearings are installed at equal intervals between the water injection cavity and the plunger splitting rod body, the outer side of the rotating bearing is fixed to the plunger splitting rod body, the water injection cavity passes through the rotating bearing, and a rotating tooth root is installed and fixed on the outer side of the water injection cavity near the water injection port.

[0012] Furthermore, a dust ring is nested on the outside of the plunger top block, a cylinder sleeve is nested on the outside of the dust ring, and sealing rings are nested on the outsides of the plunger top block and the plunger push rod, respectively.

[0013] Furthermore, a sealing ring is provided inside the water injection port to ensure a tight connection between the high-pressure water pipe and the water injection port.

[0014] Preferably, six plunger top blocks and nozzles are evenly arranged in the plug splitting rod body.

[0015] Furthermore, a method for using a local fracturing pressure relief and modification device for deep hard rock engineering comprises the following steps:

[0016] Step 1: Arrange drilling holes in the rock mass to be excavated;

[0017] Step 2, connecting and assembling the fracturing pressure relief and modification device, determining the working direction of the plunger top block according to the design and placing the plunger type fracturing rod at the designed position in the borehole;

[0018] Step 3, start the matching motor, rotate the nozzle to the fracture damage area of ​​the borehole wall, and fix the nozzle; start the fracturing pressure relief and modification device, and the plunger pressurization and high-pressure water jet work simultaneously. During the fracturing process, the direction of the nozzle is continuously rotated to adjust the direction, so that the rock on the borehole wall is cracked and expanded under the combined action of tensile stress and water pressure, and a fracture zone is formed around the rock mass to be excavated, inducing regional stress and energy release and hard rock modification;

[0019] Step 4: When the fracturing pressure relief is completed, turn off the high-pressure water pump, the motor and the external power supply, open the oil return pipe control valve, close the oil inlet pipe control valve, relieve the pressure of the hydraulic system, and discharge the hydraulic oil through the oil return pipe. The plunger top block and the plunger push rod are then retracted into the plunger placement groove under the action of the spring contraction, and then the plunger-type fracturing rod is pulled out of the drill hole to end the fracturing pressure relief operation.

[0020] Beneficial Effects

[0021] Compared with the prior art, the present invention has the following beneficial effects:

[0022] (1) Simple structure and easy operation. Compared with the existing technologies such as pressure relief blasting, pressure relief hole drilling, hydraulic fracturing, patent CN 111927470B and patent CN113217009B, the equipment and construction method provided by the present invention are simpler and easier to operate.

[0023] (2) Stronger controllability and higher precision. Compared with pressure relief blasting, the equipment and construction method provided by the present invention can control the blasting vibration hazards to a lower level; compared with drilling pressure relief holes, hydraulic fracturing, patent CN 111927470 B and patent CN113217009B, the equipment and construction method provided by the present invention can break rocks in a more directional manner and achieve the expected pressure relief effect.

[0024] (3) The pressure relief effect on hard rock is more efficient. The equipment and construction method provided by the present invention utilize the tensile stress field created by the pressure of the plunger top block to form a fracture damage zone and the weakening effect of water on the rock, so that the rock mass of the borehole wall breaks under the combined action of tensile stress and water weakening. Compared with the existing plunger-type splitting equipment technology, under the same conditions, to achieve the same hard rock fracturing effect, the plunger top block of the equipment provided by the present invention needs to apply less compressive stress to the borehole rock wall, that is, the equipment and construction method provided by the present invention will be more efficient and safe for hard rock fracturing, and also overcome the problem that the existing plunger-type splitting equipment may not be able to effectively split hard rock for pressure relief. At the same time, during the fracturing pressure relief process, the high-pressure water nozzle can be dynamically adjusted to promote the development and expansion of cracks, and the fracturing pressure relief effect is better.

[0025] (4) In addition to effectively preventing rockburst disasters, efficient induction of fracture in hard rock can also reduce the consumption of explosives required for drilling and blasting tunneling and improve engineering safety; it can also effectively improve the cuttability of regional rock mass, providing favorable conditions for non-explosive mechanized tunneling.

[0026] The technical solution of the present invention is further described in detail below through the accompanying drawings and specific implementation methods. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 It is a schematic diagram of a local fracturing, pressure relief and modification device for deep hard rock engineering provided by an embodiment of the present invention;

[0028] Figure 2 It is a front view of a plunger-type fracturing rod in a local fracturing pressure relief and modification device for deep hard rock engineering provided by an embodiment of the present invention;

[0029] Figure 3 It is a top view of a plunger-type fracturing rod in a local fracturing pressure relief and modification device for deep hard rock engineering provided by an embodiment of the present invention;

[0030] Figure 4 It is an AA cross-sectional view of a plunger-type fracturing rod in a local fracturing pressure relief and modification device for deep hard rock engineering provided by an embodiment of the present invention;

[0031] Figure 5 It is a schematic diagram of the connection and installation of a plunger top block and a plunger push rod in a local fracturing pressure relief and modification device for deep hard rock engineering provided by an embodiment of the present invention;

[0032] Figure 6 It is a BB cross-sectional view and CC, DD partial schematic view of a plunger-type fracturing rod in a local fracturing pressure relief and modification device for deep hard rock engineering provided by an embodiment of the present invention;

[0033] Figure 7It is a structural schematic diagram of a rotation controller in a local fracturing pressure relief and modification device for deep hard rock engineering provided by an embodiment of the present invention;

[0034] Figure 8 It is a schematic diagram of the working principle of a local fracturing pressure relief and modification device for deep hard rock engineering provided by an embodiment of the present invention;

[0035] Fig. 9 It is a schematic diagram of a local fracturing, pressure relief and modification device for deep hard rock engineering provided by an embodiment of the present invention when in use.

[0036] Numbers in the figure: 1—plunger-type fracturing rod, 2—high-pressure water pump, 3—motor, 4—external water source, 5—hydraulic system, 6—external power supply, 7—matching motor, 101—plunger-type fracturing rod body, 102—plunger top block, 103—water injection port, 104—oil inlet pipe, 105—oil return pipe, 106—drill hole, 107—lifting rod, 108—nozzle, 109—oil injection cavity, 110—oil inlet, 111—oil chamber, 112—dustproof ring, 113—sealing ring, 114—cylinder sleeve, 115—plunger push rod, 116—sealing ring, 117—water injection cavity, 118—plunger placement groove, 119—nozzle rotation groove, 120—rotating bearing, 121—rotating bearing, 122—rotating tooth root, 123—bearing ball, 124—rotation controller, 125—chain, 126—gear shaft, 127—control valve, 128—control valve, 129—control gear, 130—spring. DETAILED DESCRIPTION

[0037] The following will clearly and completely describe the technical solutions of various embodiments of the present invention in conjunction with the accompanying drawings. Obviously, the described embodiments are only 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 ordinary technicians in this field without making creative work are within the scope of protection of the present invention.

[0038] like Figures 1 to 9 As shown, a local fracturing, pressure relief and modification device for deep hard rock engineering provided by the present invention is composed of a plunger-type fracturing rod 1, a high-pressure water pump 2, a motor 3, an external water source 4, a hydraulic system 5 and an external power supply 6; the plunger-type fracturing rod 1 is composed of a plunger splitting rod body 101 and a plunger-type hydraulic fracturing unit, a high-pressure water jet unit and a rotation controller 124; the plunger-type splitting rod 1 is connected to the high-pressure water pump 2 through a high-pressure water pipe, the high-pressure water pump 2 provides high-pressure water for the high-pressure water jet unit, the plunger-type splitting rod 1 is connected to the hydraulic system 5 through an oil inlet pipe and an oil return pipe, the hydraulic system 5 provides hydraulic power for the plunger-type hydraulic fracturing unit, and the external power supply 6 and the motor 3 provide power for the high-pressure water pump 2.

[0039] One end of the plunger-type fracturing rod body 101 is provided with two symmetrically arranged water injection ports 103, an oil inlet pipe 104, an oil return pipe 105 and a hollow lifting rod 107. A flat cavity is provided in one end of the plunger-type fracturing rod body 101 near the water injection port 103. The plunger-type fracturing rod body 101 is evenly provided with plunger placement grooves 118 sunken into the rod body. Arc-shaped nozzle rotation grooves 119 are symmetrically provided on both sides of the plunger placement grooves 118. The plunger-type fracturing rod body 101 is provided with an oil injection cavity 109 and a water injection cavity 117. The water injection cavity 117 is provided inside the plunger-type fracturing rod body 101. The oil injection cavity 109 and the plunger placement groove 118 are isolated from each other and prevented from seeing through. The oil injection cavity 109 is connected to the hydraulic system 5 through the oil inlet pipe 104 and the oil return pipe 105. The oil inlet pipe 104 and the oil return pipe 105 are respectively installed with a control valve 127 and a control valve 128. The water injection port 103 is connected to the high-pressure water pump 2 through a high-pressure water pipe.

[0040] The plunger type hydraulic fracturing unit comprises a plunger top block 102 and a plunger push rod 115. The piston top block 102 is connected and fixed to the tail of the piston top block 102. The piston top block 102 and the piston push rod 115 are installed in the piston placement groove 118. A spring 130 is connected between the tail of the piston push rod 115 and the piston type fracturing rod body 101. The tail of the piston push rod 115 isolates the side of the piston placement groove 118 close to the oil injection cavity 109 to form an oil chamber 111. The oil injection cavity 109 and the oil chamber 111 are connected through the oil inlet 110. The piston push rod 115 is in anti-seepage and sealed coupling contact with the piston placement groove 118, and the piston push rod 115 can drive the piston top block 102 to move in the piston placement groove 118 under the power of the hydraulic oil. When the plunger type hydraulic fracturing unit is working, the hydraulic system 5 is turned on, the oil inlet pipe control valve 127 is opened, and the oil return pipe control valve 128 is closed. The hydraulic oil passes through the oil inlet pipe 104, The oil injection channel 109 and the oil inlet 110 enter the oil chamber 111, pushing the plunger push rod 115 and the plunger top block 102 to move toward the borehole rock wall, the spring 130 is stretched, and the plunger top block 102 acts on the borehole rock wall to apply pressure to the borehole rock wall for fracturing; when the fracturing pressure relief is completed, the return oil pipe control valve 128 is opened, the oil inlet pipe control valve 127 is closed, the hydraulic system 5 is depressurized, and the hydraulic oil is discharged through the return oil pipe 105, and the plunger top block 102 and the plunger push rod 115 are then retracted into the plunger placement groove 118 under the action of the contraction of the spring 130.

[0041] The high-pressure water jet unit includes a nozzle 108, which is evenly fixedly connected to the water injection cavity 117. The nozzle 108 corresponds to the arc-shaped nozzle rotation groove 119 on the plunger splitting rod body 101 in one-to-one position, and the nozzle 108 extends out of the plunger splitting rod body 101 through the nozzle rotation groove 119. When the high-pressure water jet unit is working, the nozzle 108 is rotated to the fracture damage area of ​​the hole wall, and the high-pressure pump 2 is turned on to allow water in the external water source 4 to enter the water injection cavity 117 through the high-pressure water pipe and the water injection port 103, and the high-pressure water beam is sprayed from the nozzle 108 to impact the fracture damage area of ​​the hole wall, thereby promoting the generation and expansion of cracks.

[0042] The rotation controller 124 includes a control gear 129, a gear shaft 126 and a matching motor 7. The control gear 129 is installed in the cavity of the plunger-type fracturing rod 1. The control gear 129 is connected and fixed to one end of the gear shaft 126. The gear shaft 126 passes through the hollow lifting rod 107. The other end of the gear shaft 126 is connected to the matching motor 7. The control gear 129 is connected to the rotating tooth root 122 on the water injection channel 117 through a chain 125. When the nozzle 108 needs to be rotated, the matching motor 7 is started, and the control gear 129, the chain 125 and the rotating tooth root 122 are driven to rotate through the gear shaft 126, thereby driving the water injection channel 117 and the nozzle 108. When the nozzle 108 rotates to the designed hole wall fracture damage area, the matching motor 7 is turned off and the nozzle 108 is fixed.

[0043] A dust ring 112 is nested outside the plunger top block 102 , a cylinder sleeve 114 is nested outside the dust ring 112 , and sealing rings 113 are nested outside the plunger top block 102 and the plunger push rod 115 , respectively.

[0044] The water injection channel 117 is symmetrically arranged on both sides of the plunger splitting rod body 101, and the water injection channel 117 is tightly connected to the water injection port 103 through a rotating bearing 121. Rotating bearings 120 are installed at equal intervals between the water injection channel 117 and the plunger splitting rod body 101. The outer side of the rotating bearing 120 is fixed to the plunger splitting rod body 101, and the water injection channel 117 passes through the rotating bearing 120. A rotating tooth root 122 is installed and fixed on the outer side of the water injection channel 117 near the water injection port 103.

[0045] A sealing ring 116 is disposed inside the water injection port 103 to ensure a tight connection between the high-pressure water pipe and the water injection port 103 .

[0046] Six plunger top blocks 102 and nozzles 108 are evenly arranged in the plug splitting rod body 101 .

[0047] The method for using the local fracturing pressure relief and modification device for deep hard rock engineering provided by the present invention is characterized by comprising the following steps:

[0048] Step 1, arranging a borehole 106 in the rock mass to be excavated;

[0049] Step 2: Connect and assemble the fracturing pressure relief and modification device, determine the working direction of the plunger top block 102 according to the design, and place the plunger type fracturing rod 1 at the designed position in the borehole 106;

[0050] Step 3, start the matching motor 7, rotate the nozzle 108 to the fracture damage area of ​​the borehole wall, and fix the nozzle 108; start the fracturing pressure relief and modification device, and the plunger pressurization and high-pressure water jet work simultaneously. During the fracturing process, the direction of the nozzle 108 is continuously rotated and adjusted, so that the rock on the borehole wall is cracked and expanded under the combined action of tensile stress and water pressure, and a fracture zone is formed around the rock mass to be excavated, inducing regional stress and energy release and hard rock modification;

[0051] Step 4: When the fracturing pressure relief is completed, the high-pressure water pump 2, the motor 3 and the external power supply 6 are turned off, the return oil pipe control valve 128 is opened, the oil inlet pipe control valve 127 is closed, the hydraulic system 5 is depressurized, and the hydraulic oil is discharged through the return oil pipe 105. The plunger top block 102 and the plunger push rod 115 are then retracted into the plunger placement groove 118 under the action of the contraction of the spring 130, and then the plunger-type fracturing rod 1 is pulled out from the drilled hole 106, and the fracturing pressure relief operation is completed.

[0052] The above description is only a preferred specific implementation manner of the present invention, but the protection scope of the present invention is not limited thereto. Any technician familiar with the technical field can make equivalent replacements or changes according to the technical scheme and inventive concept of the present invention within the technical scope disclosed by the present invention, which should be covered by the protection scope of the present invention.

Claims

1. A local fracturing, pressure relief and modification device for deep hard rock engineering, characterized by: It is composed of a plunger-type fracturing rod, a high-pressure water pump, an electric motor, an external water source, a hydraulic system and an external power supply; the plunger-type fracturing rod is composed of a plunger-type splitting rod body and a plunger-type hydraulic fracturing unit, a high-pressure water jet unit and a rotation controller; the plunger-type splitting rod body is connected to the high-pressure water pump through a high-pressure water pipe, the high-pressure water pump provides high-pressure water for the high-pressure water jet unit, the plunger-type splitting rod body is connected to the hydraulic system through an oil inlet pipe and an oil return pipe, the hydraulic system provides hydraulic power for the plunger-type hydraulic fracturing unit, and the external power supply and the electric motor provide driving force for the high-pressure water pump; One end of the plunger splitting rod body is provided with two symmetrically arranged water injection ports, an oil inlet pipe, an oil return pipe and a hollow lifting rod; a flat cavity is provided in one end of the plunger splitting rod body close to the water injection port; plunger placement grooves sunken into the rod body are evenly arranged on the plunger splitting rod body, and arc-shaped nozzle rotation grooves are symmetrically provided on both sides of the plunger placement groove; an oil injection cavity and a water injection cavity are provided inside the plunger splitting rod body; the water injection cavity is isolated from the oil injection cavity and the plunger placement groove to prevent seepage; the oil injection cavity is connected to the hydraulic system through the oil inlet pipe and the oil return pipe; control valves are respectively installed on the oil inlet pipe and the oil return pipe; the water injection port is connected to the high-pressure water pump through a high-pressure water pipe; The plunger type hydraulic fracturing unit comprises a plunger top block and a plunger push rod, the plunger push rod is connected and fixed to the tail of the plunger top block, the plunger top block and the plunger push rod are installed in the plunger placement groove, a spring is connected between the tail of the plunger push rod and the plunger type splitting rod body, the tail of the plunger push rod isolates the plunger placement groove close to the oil injection cavity to form an oil chamber, the oil injection cavity and the oil chamber are connected through an oil inlet, the plunger push rod is in anti-seepage and sealed coupling contact with the plunger placement groove, and the plunger push rod can drive the plunger top block to move in the plunger placement groove under the power of the hydraulic oil; the plunger type hydraulic fracturing When the unit is working, the hydraulic system is turned on, the oil inlet pipe control valve is opened, and the return pipe control valve is closed. The hydraulic oil enters the oil chamber through the oil inlet pipe, the oil injection cavity and the oil inlet, pushing the plunger push rod and the plunger top block to move toward the borehole rock wall. The spring is stretched, and the plunger top block acts on the borehole rock wall to apply pressure to the borehole rock wall for fracturing. When the fracturing pressure relief is completed, the return oil pipe control valve is opened, the oil inlet pipe control valve is closed, the hydraulic system is depressurized, and the hydraulic oil is discharged through the return oil pipe. The plunger top block and the plunger push rod are then retracted into the plunger placement groove under the action of the spring contraction.

2. A local fracturing, pressure relief and modification device for deep hard rock engineering according to claim 1, characterized in that: The high-pressure water jet unit comprises a nozzle, which is evenly fixedly connected to the water injection cavity, and the nozzle corresponds to the position of the arc-shaped nozzle rotation groove on the plunger-type splitting rod body one by one, and the nozzle extends out of the plunger-type splitting rod body through the nozzle rotation groove; when the high-pressure water jet unit is working, the nozzle is rotated to the fracture damage area of ​​the hole wall, and the high-pressure pump is turned on to allow water in the external water source to enter the water injection cavity through the high-pressure water pipe and the water injection port, and the high-pressure water beam is sprayed from the nozzle to impact the fracture damage area of ​​the hole wall, thereby promoting the generation and expansion of cracks.

3. A local fracturing, pressure relief and modification device for deep hard rock engineering according to claim 1, characterized in that: The rotary controller comprises a control gear, a gear shaft and a matching motor. The control gear is installed in a cavity in the plunger-type fracturing rod. The control gear is connected and fixed to one end of the gear shaft. The gear shaft passes through a hollow lifting rod. The other end of the gear shaft is connected to the matching motor. The control gear is connected to a rotating tooth root on the water injection cavity through a chain. When the nozzle needs to be rotated, the matching motor is started, and the control gear, the chain and the rotating tooth root are driven to rotate through the gear shaft, thereby driving the water injection cavity and the nozzle to rotate. When the nozzle rotates to the designed hole wall fracture damage area, the matching motor is turned off and the nozzle is fixed.

4. A local fracturing, pressure relief and modification device for deep hard rock engineering according to claim 1, characterized in that: The water injection cavity is symmetrically arranged on both sides of the plunger-type splitting rod body, and the water injection cavity is tightly connected with the water injection port through a rotary bearing; rotary bearings are installed at equal intervals between the water injection cavity and the plunger-type splitting rod body, the outer side of the rotary bearing is fixed to the plunger-type splitting rod body, the water injection cavity passes through the rotary bearing, and a rotary tooth root is installed and fixed on the outer side of the water injection cavity near the water injection port.

5. The local fracturing, pressure relief and modification device for deep hard rock engineering according to claim 1, characterized in that: A dustproof ring is nested on the outside of the plunger top block, a cylinder sleeve is nested on the outside of the dustproof ring, and sealing rings are nested on the outsides of the plunger top block and the plunger push rod respectively.

6. The local fracturing, pressure relief and modification device for deep hard rock engineering according to claim 1, characterized in that: A sealing ring is arranged inside the water injection port to ensure a tight connection between the high-pressure water pipe and the water injection port.

7. The local fracturing, pressure relief and modification device for deep hard rock engineering according to claim 1, characterized in that: The plunger top blocks and nozzles are evenly arranged in six in the plunger type splitting rod body.

8. A method for using a local fracturing, pressure relief and modification device for deep hard rock engineering according to any one of claims 1 to 7, characterized in that The following steps are involved: Step 1: Arrange drilling holes in the rock mass to be excavated; Step 2, connecting and assembling the fracturing pressure relief and modification device, determining the working direction of the plunger top block according to the design and placing the plunger type fracturing rod at the designed position in the borehole; Step 3, start the matching motor, rotate the nozzle to the fracture damage area of ​​the borehole wall, and fix the nozzle; start the fracturing pressure relief and modification device, and the plunger pressurization and high-pressure water jet work simultaneously. During the fracturing process, the direction of the nozzle is continuously rotated to adjust the direction, so that the rock on the borehole wall is cracked and expanded under the combined action of tensile stress and water pressure, and a fracture zone is formed around the rock mass to be excavated, inducing regional stress and energy release and hard rock modification; Step 4: When the fracturing pressure relief is completed, turn off the high-pressure water pump, the motor and the external power supply, open the oil return pipe control valve, close the oil inlet pipe control valve, relieve the pressure of the hydraulic system, and discharge the hydraulic oil through the oil return pipe. The plunger top block and the plunger push rod are then retracted into the plunger placement groove under the action of the spring contraction, and then the plunger-type fracturing rod is pulled out of the drill hole to end the fracturing pressure relief operation.

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