阅读说明：本技术 一种用于钻探的扩孔钻具及其扩孔方法 (Hole expanding drilling tool for drilling and hole expanding method thereof ) 是由 刘春� 周福宝 朱少廷 谷嘉兴 孔祥毅 于 2019-10-12 设计创作，主要内容包括：一种用于钻探的扩孔钻具及其扩孔方法,在钻具主体中安装有圆柱销(9),扩孔刀(10)可旋转地安装在圆柱销的前侧,在钻具主体前部的管道侧壁上开设有可供扩孔刀旋进旋出的通孔,在扩孔刀内部开设气水通道Ⅱ(7),在扩孔刀的一侧设置有气水分支通道(14)；在圆柱销的后部设置有用来限制扩孔刀旋转角度的限位结构,包括限位块(8)、限位杆(8.1),在限位杆内部开设气水通道Ⅰ(15),气水通道Ⅰ的前端安装有可伸缩软管(5)的后端,可伸缩软管前端连接气水通道Ⅱ上的进水口。本发明结构简单,操作方便,在不需要改变扩孔刀长度的情况下,可以适应不同扩孔直径的需求,能够降低瓦斯抽采时间,提高瓦斯抽采效率。(A hole expanding drilling tool for drilling and a hole expanding method thereof are disclosed, wherein a cylindrical pin (9) is installed in a drilling tool main body, a hole expanding cutter (10) is rotatably installed on the front side of the cylindrical pin, a through hole for the hole expanding cutter to screw in and out is formed in the side wall of a pipeline in the front part of the drilling tool main body, an air-water channel II (7) is formed in the hole expanding cutter, and an air-water branch channel (14) is formed in one side of the hole expanding cutter; be provided with the limit structure who is used for restricting reamer rotation angle at the rear portion of cylindric lock, including stopper (8), gag lever post (8.1), set up air water passageway I (15) inside the gag lever post, the rear end of scalable hose (5) is installed to the front end of air water passageway I, and the water inlet on the air water passageway II is connected to scalable hose front end. The invention has simple structure and convenient operation, can meet the requirements of different reaming diameters under the condition of not changing the length of the reaming cutter, can reduce the gas extraction time and improve the gas extraction efficiency.)

1. The utility model provides a reaming drilling tool for probing, including screwed joint (1) of being connected with the drilling rod, drilling tool main part (3), PDC drill bit (6), the front end installation PDC drill bit (6) of drilling tool main part (3), rear end connection screwed joint (1) of drilling tool main part (3), a serial communication port, drilling tool main part (3) are hollow structure, install cylindric lock (9) in drilling tool main part (3), reamer (10) rotatably install the front side at cylindric lock (9), set up the through-hole that can supply reamer (10) to revolve into and screw out on the pipeline lateral wall of drilling tool main part (3) front portion, set up inside air water passageway II (7) that supply compressed air and high-pressure rivers to pass through in reamer (10), be provided with at least one air water branch passageway (14) that communicate with air water passageway II (7) in the coal seam, the effect that the reaming section of high-pressure rivers through air water branch passageway (14) and drilling tool main part (3) formed The hole expanding cutter (10) is reversely screwed out of the through hole by force; a limiting structure used for limiting the rotation angle of the reaming cutter is arranged at the rear part of the cylindrical pin (9), the limiting structure comprises a limiting block (8) with a forward opening and a limiting rod (8.1) integrally connected with the limiting block (8), the outer diameter of the limiting block (8) is matched with the side wall of the cavity of the cutter main body (3), the span of the limiting block (8) is larger than the outer diameter of the cylindrical pin (9), a spring (4) matched with the outer diameter of the limiting rod is sleeved on the limiting rod (8.1), and a baffle (16) used for preventing the spring (4) from moving forwards is arranged in the cavity at the rear part of the cylindrical pin (9); the rear end of gag lever post (8.1) is provided with shaft shoulder (8.2) that are used for preventing the rear end of spring (4) to pop out, is equipped with air water passageway I (15) that supply compressed air and high-pressure rivers pass through in gag lever post (8.1) inside, the stiff end of scalable hose (5) rear end is connected to the front end of air water passageway I (15), and the water inlet on air water passageway II (7) is connected to the scalable section of scalable hose (5) front end, and high-pressure rivers flow out from air water branch passage (14) behind threaded joint (1), air water passageway I (15), scalable hose (5), the water inlet on air water passageway II (7), air water passageway II (7) in proper order.

2. A reamer tool for drilling according to claim 1, wherein the rotation of the reamer (10) is in the range of 0-90 °.

3. a reamer tool for drilling according to claim 1 or 2, wherein the gas-water branch passage (14) is in vertical communication with the gas-water passage ii (7).

4. A reamer tool for drilling according to claim 1 or 2, wherein a diamond compact (11) is mounted on both the reamer (10) and the PDC bit (6).

5. a reamer tool for drilling according to claim 3, wherein a sealing ring (12) is provided at the connection of the shoulder (8.2) and the spring (4).

6. a reamer tool for drilling according to claim 3, wherein a spring guard (13) is provided between the spring (4) and the inner wall of the tool body (3).

7. A reamer tool for drilling according to claim 3, wherein a collar (2) is mounted at the rear end of the stop rod (8.1).

8. a method of reaming a reamer tool for drilling, comprising the steps of:

firstly, a high-pressure water tail is arranged at the tail part of a drill rod to provide high-pressure water flow, a spring (4) is ensured to be always in a contraction state under the action of the externally connected high-pressure water flow, a cylindrical pin (9) is completely surrounded by a limiting block (8) under the action of the contraction force of the spring to limit the opening of a reaming cutter (10), and a drilling tool is used as a common drill bit to normally perform drilling operation;

When the drill rod drills to a section needing hole expanding, the water pressure of high-pressure water flow is reduced, the spring (4) expands to enable the limiting block (8) to move backwards, meanwhile, the high-pressure water flow sequentially passes through the joint (1), the air-water channel I (15), the telescopic hose (5), the water inlet on the air-water channel II (7), the air-water channel II (7) and the air-water branch channel (14) and then flows out, the high-pressure water flow passing through the air-water branch channel (14) and an acting force formed by the coal seam hole expanding section of the drill tool main body (3) enable the hole expanding cutter (10) to reversely screw out of the through hole, the drill rod is controlled to slowly rotate by the rotary machine, the opening angle of the hole expanding cutter (10) is slowly increased until the hole expanding cutter; when the opening angle of the broaching cutter (10) needs to be reduced, the water pressure of high-pressure water flow is increased, the generated action force acts on the rear end of the limiting block (8) to contract the spring (4), the limiting block (8) moves forwards, the opening angle of the broaching cutter (10) is gradually reduced under the limitation of the limiting block (8), and the broaching diameter is correspondingly reduced;

thirdly, after reaming is finished, stopping supplying high-pressure water flow, pulling back the drilling machine, and automatically closing the reaming cutter (10) under the action of the common drilling wall; and taking out the drilling tool, and cleaning the drilling tool by using water for next use.

9. a method of reaming a reamer tool for drilling according to claim 8, wherein the high pressure water flow is related to the reamer (10) deployment angle and reaming radius by:

the stress area S of the limiting rod (8.1) meets the formula (1)

In the formula: l is the diameter of the acting surface of the limiting rod under the action of high-pressure water flow;

L₁the diameter of the gas-water channel;

The acting force F on the limiting rod (8.1) satisfies the formula (2)

In the formula: p is the water pressure of the high-pressure water flow;

length L of spring (4) after force application₃Satisfies the formula (3))

in the formula: f is the friction between the limiting structure and the drilling tool main body;

k is the elastic coefficient of the spring;

The distance of the limiting block (8) beyond the reamer (10) meets the formula (4)

in the formula: l is₂Is the length of the spring;

L₄The vertical distance between the cylindrical pin and the limiting block is the unstressed vertical distance of the spring;

The theoretical angle alpha developed when the water pressure of the high-pressure water flow of the broaching tool (10) is P meets the formula (5)

In the formula: l is₅the length of the inner diameter of the limiting block;

considering that when the limiting block (8) is acted by high-pressure water flow, an angle correction coefficient beta is introduced due to the on-way resistance loss of the high-pressure water flow flowing into the air-water branch channel (14) from the drill rod and the gravity of the expanding cutter (10), the expanded angle of the expanding cutter (10) when the water pressure of the high-pressure water flow is P meets the formula (6)

α_m＝αβ (6)

In the formula: alpha is alpha_mthe expanding angle of the expanding knife is changed;

alpha is the expanding theoretical angle of the reamer;

Beta is an angle correction coefficient;

The expanding length of the expanding cutter (10), namely the expanding radius R when the water pressure of the high-pressure water flow is P, meets the formula (7)

R＝hsinα_m (7)

In the formula: h is the length of the reamer.

Technical Field

the invention relates to a hole expanding drilling tool for drilling, in particular to a hole expanding drilling tool for drilling and a hole expanding method thereof, and belongs to the technical field of coal mine gas extraction.

Background

Along with the improvement of the coal mining level in China, the coal mining gradually extends to the deep part, the geological structure of the deep coal bed is more complex, the gas content and the gas pressure of the coal bed are obviously increased, and many low gas mines with middle-shallow burial depth are converted into high gas mines.

The permanent measure of the gas disaster of the high gas mine is gas extraction. 70% of national key coal mines in China are high gas mines, and most of the coal mines are low-permeability coal beds, so that the gas extraction time is greatly increased, the extraction rate and the extraction amount of mine gas are seriously hindered, and the succession of mine production is influenced. For a single high-gas low-permeability coal seam without a mining protective layer, the permeability of the coal seam is improved by means of a method for relieving pressure in the seam and increasing the permeability, and then a reasonable extraction method is adopted to reduce the content of the analyzable gas in the coal seam to a specified index.

In order to effectively solve the problem of gas extraction of a low-permeability coal seam, a series of enhanced permeability-increasing technologies, such as deep-hole presplitting blasting, hydraulic punching, fracturing, slotting and the like, have been successively researched, and the common point of the measures is that the external high energy disturbs the coal body to form cracks, expand the internal surface area of a drainage hole and further increase the permeability of the coal seam. However, the disturbance of high energy to the coal body is easy to induce and protrude, which puts high requirements on a mine ventilation system and safety protection measures adopted in the construction process. Therefore, the anti-reflection measures have certain adaptability, the anti-reflection measures are carefully selected, part of anti-reflection technologies are complex in construction process and have great influence on mine operation environment, and the anti-reflection technology cannot be applied to all coal seams and has certain limitation in popularization and application.

disclosure of Invention

The invention aims to provide a reaming drilling tool for drilling and a reaming method thereof, which have the advantages of simple structure and convenience in operation, can meet the requirements of different reaming diameters under the condition of not changing the length of a reaming cutter, can reduce the gas extraction time, and can improve the gas extraction efficiency.

In order to achieve the purpose, the invention provides a reaming drilling tool for drilling, which comprises a threaded joint connected with a drill rod, a drilling tool main body and a PDC (polycrystalline diamond compact) drilling bit, wherein the PDC drilling bit is installed at the front end of the drilling tool main body, the rear end of the drilling tool main body is connected with the threaded joint, the drilling tool main body is of a hollow structure, a cylindrical pin is installed in the drilling tool main body, a reaming cutter is rotatably installed on the front side of the cylindrical pin, a through hole for the reaming cutter to screw in and out is formed in the side wall of a pipeline at the front part of the drilling tool main body, an air-water channel II for compressed air and high-pressure water to pass through is formed in the reaming cutter, at least one air-water branch channel communicated with the air-water channel II is arranged on one side of the reaming cutter, and the reaming cutter is reversely; the rear part of the cylindrical pin is provided with a limiting structure for limiting the rotation angle of the reaming cutter, the limiting structure comprises a limiting block with a forward opening and a limiting rod integrally connected with the limiting block, the outer diameter of the limiting block is matched with the side wall of the cavity of the cutter main body, the span of the limiting block is larger than the outer diameter of the cylindrical pin, the limiting rod is sleeved with a spring matched with the outer diameter of the limiting rod, a baffle plate for preventing the spring from moving forward is arranged in the cavity at the rear part of the cylindrical pin, and the inner diameter of the baffle plate is smaller than the outer diameter of; the rear end of gag lever post is provided with the shaft shoulder that is used for preventing the rear end of spring from popping out, is equipped with the air water passageway I that supplies compressed air and high-pressure rivers to pass through in gag lever post inside, the stiff end of scalable hose rear end is connected to the front end of air water passageway I, and the water inlet on the scalable section connection air water passageway II of scalable hose front end, high-pressure rivers flow from air water branch passageway behind water inlet, the air water passageway II on screwed joint, air water passageway I, scalable hose, air water passageway II in proper order.

In order to meet the requirement of the hole expanding diameter, the rotating range of the hole expanding cutter is set to be 0-90 degrees, and the change of the hole expanding diameter is met through the rotating angle of the hole expanding cutter.

The high-pressure water flow flowing out of the gas-water branch channel and the action force formed by the coal seam reaming section of the drilling tool main body enable the reaming cutter to reversely screw out the through hole.

The reaming cutter is a cutter for reaming and can be used for crushing underground coal seams, because the hardness of coal in the coal seams is inconsistent and gangue is carried in the coal seams, the reaming cutter with high wear resistance and long service life is needed, and in order to meet the hardness requirements of the reaming cutter and the PDC drill bit, diamond composite sheets are selected to be arranged on the reaming cutter and the PDC drill bit.

In order to seal the spring and prevent the spring from leaking water, the sealing ring is arranged at the joint of the shaft shoulder and the spring.

in order to protect the spring, prevent the spring from being damaged and prolong the service life of the spring, a spring protection ring is arranged between the spring and the inner wall of the drilling tool main body.

in order to prevent the spring force from being overlarge to pop out the left end of the limiting structure, the rear end of the limiting rod is provided with a check ring.

a method of reaming a reamer tool for drilling, comprising the steps of:

firstly, a high-pressure water tail is arranged at the tail part of a drill rod to provide high-pressure water flow, a spring is ensured to be always in a contraction state under the action of the externally connected high-pressure water flow, a cylindrical pin is completely surrounded by a limiting block under the action of the contraction force of the spring to limit the opening of a reaming cutter, and a drilling tool is used as a common drill bit to normally perform drilling operation;

When the drill rod drills to a section needing hole expanding, the water pressure of high-pressure water flow is reduced, the spring expands to enable the limiting block to move backwards, meanwhile, the high-pressure water flow sequentially passes through the joint, the air-water channel I, the telescopic hose, the water inlet on the air-water channel II, the air-water channel II and the air-water branch channel and then flows out, the high-pressure water flow passing through the air-water branch channel and the coal seam hole expanding section of the drill body form acting force to enable the hole expanding cutter to reversely rotate out of the through hole, the drill rod is controlled to slowly rotate by the rotary machine, the opening angle of the hole expanding cutter is slowly increased until the hole expanding cutter; when the opening angle of the reaming cutter needs to be reduced, the water pressure of high-pressure water flow is increased, the generated action force acts on the rear end of the limiting block to contract the spring, the limiting block moves forwards, the opening angle of the reaming cutter is gradually reduced under the limitation of the limiting block, and the reaming diameter is correspondingly reduced;

After reaming is finished, stopping supplying high-pressure water flow, pulling back the drilling machine, and automatically closing the reaming cutter under the action of the common drilling wall; and taking out the drilling tool, and cleaning the drilling tool by using water for next use.

The relationship between the high-pressure water flow and the expanding angle and the expanding radius of the expanding cutter is as follows:

the stress area S of the limiting rod satisfies the formula (1)

In the formula: l is the diameter of the acting surface of the limiting rod under the action of high-pressure water flow;

L₁The diameter of the gas-water channel;

The acting force F on the limiting rod satisfies the formula (2)

in the formula: p is the water pressure of the high-pressure water flow;

Length L of spring after force is applied₃satisfy formula (3)

in the formula: f is the friction between the limiting structure and the drilling tool main body;

k is the elastic coefficient of the spring;

the distance of the limiting block beyond the reamer satisfies the formula (4)

In the formula: l is₂Is the length of the spring;

L₄The vertical distance between the cylindrical pin and the limiting block is the unstressed vertical distance of the spring;

the theoretical angle alpha of the expanding knife when the water pressure of the high-pressure water flow is P satisfies the formula (5)

In the formula: l is₅The length of the inner diameter of the limiting block;

When the limiting block is under the action of high-pressure water flow, an angle correction coefficient beta is introduced due to the on-way resistance loss of the high-pressure water flow flowing into the air-water branch channel from the drill rod and the gravity of the broaching tool, so that the unfolded angle of the broaching tool when the water pressure of the high-pressure water flow is P meets the formula (6)

α_m＝αβ (6)

In the formula: alpha is alpha_mThe expanding angle of the expanding knife is changed;

Alpha is the expanding theoretical angle of the reamer;

Beta is an angle correction coefficient;

The expanding length of the expanding cutter when the water pressure of the high-pressure water flow is P, namely the expanding radius R, meets the formula (7)

R＝h sinα_m (7)

in the formula: h is the length of the reamer.

Compared with the prior art, the reaming cutter and the limiting structure for limiting the rotation angle of the reaming cutter are arranged in the drilling tool main body, the air-water channel II for compressed air and high-pressure water flow to pass through is formed in the reaming cutter, at least one air-water branch channel communicated with the air-water channel II is arranged on one side of the reaming cutter, and the reaming cutter is reversely screwed out of the through hole through the acting force formed by the high-pressure water flow of the air-water branch channel and the coal seam reaming section of the drilling tool main body; a gas-water channel I for high-pressure water flow to pass through is formed in the limiting rod, and the high-pressure water flow sequentially passes through the joint, the gas-water channel I, the telescopic hose, the water inlet on the gas-water channel II, the gas-water channel II and the gas-water branch channel and then flows out; through the structure, when the drilling tool is used as a common drill bit to normally perform drilling operation, the spring is ensured to be always in a shrinkage state under the action of an externally connected high-pressure water flow, the limiting block completely surrounds the cylindrical pin under the action of the shrinkage force of the spring to limit the opening of the reaming cutter, when the drilling rod drills to a section needing reaming, the water pressure of the high-pressure water flow is reduced, the spring expands to enable the limiting block to move backwards, meanwhile, the high-pressure water flow sequentially passes through the joint, the air-water channel I, the telescopic hose, the water inlet on the air-water channel II, the air-water channel II and the air-water branch channel and then flows out, the reaming cutter reversely rotates out of the through hole under the action force formed by the high-pressure water flow of the air-water branch channel and the coal seam reaming section of the drilling tool main body; when the opening angle of the reaming cutter needs to be reduced, the water pressure of high-pressure water flow is increased, the generated action force acts on the rear end of the limiting block to contract the spring, the limiting block moves forwards, the opening angle of the reaming cutter is gradually reduced under the limitation of the limiting block, and the reaming diameter is correspondingly reduced; the invention has simple structure and convenient operation, can meet the requirements of different reaming diameters under the condition of not changing the length of the reaming cutter, can reduce the gas extraction time and improve the gas extraction efficiency.

Drawings

FIG. 1 is a schematic structural view of the present invention;

FIG. 2 is a schematic view of the reamer of the present invention fully restrained by a stop;

FIG. 3 is a first state view of the reamer of the invention being restrained by a stop;

FIG. 4 is a second state of the reamer of the invention as constrained by the stop;

fig. 5 is a schematic view of the reamer of the invention fully open.

In the figure: 1. screwed joint, 2, retaining ring, 3, drilling tool main part, 4, spring, 5, scalable hose, 6, PDC drill bit, 7, air water passageway II, 8, stopper, 8.1, gag lever post, 8.2, shaft shoulder, 9, cylindric lock, 10, reamer, 11, the compound piece of diamond, 12, sealing washer, 13, spring guard circle, 14, air water branch passageway, 15, air water passageway I, 16, baffle.

Detailed Description

The invention will be further explained with reference to the drawings.

as shown in fig. 1, a reamer for drilling comprises a threaded joint 1 connected with a drill rod, a drill body 3, a PDC drill bit 6, the PDC drill bit 6 is mounted at the front end of the drill body 3, the threaded joint 1 is connected at the rear end of the drill body 3, the drill body 3 is a hollow structure, a cylindrical pin 9 is installed in the drill body 3, a reamer 10 is rotatably installed at the front side of the cylindrical pin 9, a through hole for the reamer 10 to screw in and out is arranged on the side wall of the pipeline at the front part of the drilling tool main body 3, an air-water channel II 7 for compressed air and high-pressure water flow to pass through is arranged in the reamer 10, one side of the reamer 10 is provided with at least one air-water branch channel 14 communicated with the air-water channel II 7, the reaming cutter 10 is reversely screwed out of the through hole by the acting force formed by the high-pressure water flow passing through the gas-water branch passage 14 and the coal seam reaming section of the drilling tool main body 3; a limiting structure used for limiting the rotation angle of the reamer is arranged at the rear part of the cylindrical pin 9 and comprises a limiting block 8 with a forward opening and a limiting rod 8.1 integrally connected with the limiting block 8, in order to prevent the limiting structure from rotating in the drilling tool main body, the limiting rod 8.1 is circumferentially positioned, the outer diameter of the limiting block 8 is matched with the side wall of the cavity of the drilling tool main body 3, the span of the limiting block 8 is larger than the outer diameter of the cylindrical pin 9, a spring 4 matched with the outer diameter of the limiting rod 8.1 is sleeved on the limiting rod 8.1, a baffle 16 used for preventing the spring 4 from moving forwards is arranged in the cavity at the rear part of the cylindrical pin 9, and the inner diameter of the baffle 16 is smaller than the; the rear end of gag lever post 8.1 is provided with the shaft shoulder 8.2 that is used for preventing spring 4's rear end from popping out, is equipped with the air water passageway I15 that supplies compressed air and high-pressure rivers to pass through inside gag lever post 8.1, the stiff end of 5 rear ends of scalable hose is connected to the front end of air water passageway I15, and the water inlet on air water passageway II 7 is connected to the scalable section of 5 front ends of scalable hose, and high-pressure rivers flow out from air water branch passage 14 behind threaded joint 1, air water passageway I15, scalable hose 5, the water inlet on air water passageway II 7, air water passageway II 7 in proper order.

the rotating range of the expanding cutter 10 is 0-90 degrees.

The gas-water branch channel 14 is vertically communicated with the gas-water channel II 7.

The diamond compact 11 is mounted on both the reamer 10 and the PDC bit 6.

A sealing ring 12 is arranged at the joint of the shaft shoulder 8.2 and the spring 4.

A spring guard 13 is provided between the spring 4 and the inner wall of the tool body 3.

a retainer ring 2 is arranged at the rear end of the limiting rod 8.1.

As shown in fig. 1-5, a method of reaming a reamer tool for drilling, comprising the steps of:

Firstly, a high-pressure water tail is arranged at the tail part of a drill rod to provide high-pressure water flow, the spring 4 is ensured to be always in a contraction state under the action of the externally connected high-pressure water flow, the limiting block 8 completely surrounds the cylindrical pin 9 under the action of the contraction force of the spring to limit the opening of the reaming cutter 10, and the drilling tool is used as a common drill bit to normally perform drilling operation;

when the drill rod drills to a section needing hole expanding, the water pressure of high-pressure water flow is reduced, the spring 4 expands to enable the limiting block 8 to move backwards, meanwhile, the high-pressure water flow sequentially passes through the joint 1, the air-water channel I15, the telescopic hose 5, the water inlet on the air-water channel II 7, the air-water channel II 7 and the air-water branch channel 14 and then flows out, the high-pressure water flow passing through the air-water branch channel 14 and an acting force formed by the coal seam hole expanding section of the drilling tool main body 3 enable the hole expanding cutter 10 to reversely screw out a through hole, the rotary machine is controlled to slowly rotate the drill rod, the opening angle of the hole expanding cutter 10 is slowly increased until the hole expanding cutter; when the opening angle of the reamer 10 needs to be reduced, the water pressure of high-pressure water flow is increased, the generated action force acts on the rear end of the limiting block 8 to contract the spring 4, the limiting block 8 moves forwards, the opening angle of the reamer 10 is gradually reduced under the limitation of the limiting block 8, and the reaming diameter is correspondingly reduced;

thirdly, after reaming is finished, stopping supplying high-pressure water flow, pulling back the drilling machine, and automatically closing the reaming cutter 10 under the action of the common drilling wall; and taking out the drilling tool, and cleaning the drilling tool by using water for next use.

The relationship between the high-pressure water flow and the expanding angle and the expanding radius of the expanding cutter 10 is as follows:

The stress area S of the limiting rod 8.1 meets the formula (1)

In the formula: l is the diameter of the acting surface of the limiting rod under the action of high-pressure water flow;

L₁the diameter of the gas-water channel;

The acting force F on the limiting rod 8.1 satisfies the formula (2)

In the formula: p is the water pressure of the high-pressure water flow;

Length L of spring 4 after being stressed₃Satisfy formula (3)

in the formula: f is the friction between the limiting structure and the drilling tool main body;

k is the elastic coefficient of the spring;

the distance of the limiting block 8 beyond the reamer 10 satisfies the formula (4)

in the formula: l is₂is the length of the spring;

L₄The vertical distance between the cylindrical pin and the limiting block is the unstressed vertical distance of the spring;

the theoretical angle α of the expanding cutter 10 when the water pressure of the high-pressure water flow is P satisfies the formula (5)

In the formula: l is₅The length of the inner diameter of the limiting block;

Considering that when the limiting block 8 is acted by the high-pressure water flow, an angle correction coefficient beta is introduced due to the on-way resistance loss of the high-pressure water flow flowing into the air-water branch channel 14 from the drill rod and the gravity of the expanding cutter 10, and the expanding angle of the expanding cutter 10 when the water pressure of the high-pressure water flow is P meets the formula (6)

α_m＝αβ (6)

In the formula: alpha is alpha_mthe expanding angle of the expanding knife is changed;

Alpha is the expanding theoretical angle of the reamer;

beta is an angle correction coefficient;

the expanding length of the reamer 10 when the water pressure of the high-pressure water flow is P, that is, the reaming radius R, satisfies the formula (7)

R＝h sinα_m (7)

In the formula: h is the length of the reamer.