Rotary drilling rig segmented constant ground pressure drilling method, system and rotary drilling rig

Abstract

This invention discloses a segmented constant ground pressure drilling method, system, and rotary drilling rig. The method includes: when the rotary drilling rig is in a first working condition, maintaining a constant drill bit ground pressure by adjusting the winch pull; wherein, the first working condition refers to a condition where the drill bit ground pressure is not greater than the sum of the drill rod weight and the drill bit weight; when the rotary drilling rig is in a second working condition, maintaining a constant drill bit ground pressure by adjusting the force provided by the pressure cylinder; wherein, the second working condition refers to a condition where the drill bit ground pressure is not less than the sum of the drill rod weight and the drill bit weight, and not greater than the sum of the drill rod weight, the power head weight, and the drill bit weight. This invention can control the rotary drilling rig to maintain a constant pressure within a relatively wide range, meeting the ground pressure requirements for drilling under various working conditions of the rotary drilling rig.

Description

Technical Field

[0001] This invention belongs to the field of rotary drilling rig technology, specifically relating to a segmented constant ground pressure drilling method, system, and rotary drilling rig. Background Technology

[0002] Rotary drilling rigs are foundation construction machinery, widely used in the ground piling industry. The technology is relatively mature. They primarily rely on the weight of the drill rod, drill bit, power head, pressure from the hydraulic cylinder, and winch tension to create downward pressure on the ground. This force is known in the industry as axial ground pressure. Under this axial pressure, the drill bit penetrates the rock, while the power head drives the drill rod to rotate the drill bit, generating a cutting torque on the ground. Under the action of rotation (torque), the rock is sheared and broken along the bottom of the hole. Under the action of ground pressure and cutting torque, the drill bit continuously penetrates downwards during rotation. Therefore, under the combined action of axial and horizontal forces, the rock at the bottom of the hole is continuously broken in spiral layers. Due to the complexity of the geological formations, the axial ground pressure of rotary drilling needs to operate within a relatively wide range. Furthermore, to ensure a more stable drilling torque, the ground pressure needs to be controlled relatively steadily. The main problems with existing technical solutions include: 1. Non-constant pressure drilling, where the ground pressure is constantly changing, resulting in large fluctuations in cutting torque. Sudden increases in torque pose a risk of stuck drill bit, while excessively low torque leads to energy waste; 2. The pressurizing cylinder suspends the power head G2 for vertical movement. For safety reasons, a pressurizing balance valve is often installed on the pressurizing cylinder. Due to the opening characteristics of the pressurizing balance valve, a surge in ground pressure under certain working conditions is not conducive to pressurization in rotary drilling, causing large fluctuations in the power head torque; The constant ground pressure control range has blind spots in the following ranges, making quantitative and stable control impossible: Low pressure zone ① F≤G1+G3, Medium pressure zone ② G1+G3≤F≤G1+G2+G3, where F represents the drill bit's ground pressure, G1 represents the drill rod weight, G2 represents the power head weight, and G3 represents the drill bit weight. Summary of the Invention

[0003] To address the shortcomings of existing technologies, this invention provides a segmented constant ground pressure drilling method, system, and rotary drilling rig, which can control the rotary drilling rig to maintain a constant pressure within a relatively wide range, meeting the ground pressure requirements for drilling under various working conditions.

[0004] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0005] Firstly, a method for constant ground pressure drilling with a rotary drilling rig is provided, comprising: when the rotary drilling rig is in a first working condition, maintaining a constant ground pressure on the drill bit by adjusting the winch tension; wherein, the first working condition refers to a working condition in which the ground pressure on the drill bit is not greater than the sum of the weight of the drill rod and the weight of the drill bit; when the rotary drilling rig is in a second working condition, maintaining a constant ground pressure on the drill bit by adjusting the force provided by the pressure cylinder; wherein, the second working condition refers to a working condition in which the ground pressure on the drill bit is not less than the sum of the weight of the drill rod and the weight of the drill bit, and not greater than the sum of the weight of the drill rod, the weight of the power head, and the weight of the drill bit.

[0006] Furthermore, the step of maintaining constant drill bit pressure on the ground by adjusting winch tension includes: collecting drill bit pressure on the ground; determining the difference between drill bit pressure on the ground and a set target pressure on the ground; when the difference is greater than a set deviation value, sending a control signal to the solenoid valve at the control end of the floating valve to open the floating valve, thereby connecting the working oil port A at the lifting end of the winch motor with the working oil port B at the lowering end, and reducing the winch tension.

[0007] Furthermore, the opening of the floating valve and the opening time are determined based on the detected winch tension.

[0008] Furthermore, the set deviation value ranges from 0.5 tons to 2 tons.

[0009] Furthermore, the method of maintaining constant ground pressure of the drill bit by adjusting the winch tension includes: setting a first pressure regulating valve, which is used to control the oil pressure between the load end of the winch balance valve and the working oil port A of the lifting end of the winch motor, thereby adjusting the winch tension.

[0010] Furthermore, the first pressure regulating valve is a combination valve, including a first electro-proportional relief valve, a first electro-hydraulic directional valve, and a first hydraulically controlled check valve; the outlet of the first electro-hydraulic directional valve is connected to the inlet of the first hydraulically controlled check valve and the inlet of the first electro-proportional relief valve; the outlet of the first hydraulically controlled check valve is connected between the load end of the winch balance valve and the working port A of the lifting end of the winch motor; the outlet of the first electro-proportional relief valve is connected to the oil tank; the first electro-hydraulic directional valve is used to deliver hydraulic oil with a set pressure through the first hydraulically controlled check valve to the lifting end of the winch motor when it is open; the first electro-proportional relief valve is used to control the overflow pressure to adjust the winch pulling force.

[0011] Furthermore, the first pressure regulating valve includes only a first electro-proportional relief valve. The inlet of the first electro-proportional relief valve is connected between the load end of the winch balance valve and the working oil port A of the lifting end of the winch motor. The outlet of the first electro-proportional relief valve is connected to the oil tank. The first electro-proportional relief valve is used to control the overflow pressure to regulate the winch tension.

[0012] Furthermore, the first pressure regulating valve is a combination valve, including a first electro-proportional relief valve and a first electrically controlled shut-off valve. The outlet of the first electro-proportional relief valve is connected to the inlet of the first electrically controlled shut-off valve, and the outlet of the first electrically controlled shut-off valve is connected between the load end of the hoisting balance valve and the working oil port A of the hoisting motor.

[0013] Furthermore, the method of maintaining a constant drill bit pressure on the ground by adjusting the force provided by the pressurizing cylinder includes: setting a second pressure regulating valve, which is connected in parallel to the lifting end of the pressurizing cylinder, for adjusting the force provided by the pressurizing cylinder.

[0014] Furthermore, the second pressure regulating valve is a combination valve, including a second electro-proportional relief valve, a second electro-pneumatic directional valve, and a second hydraulically controlled check valve; the outlet of the second electro-pneumatic directional valve is connected to the inlet of the second hydraulically controlled check valve and the inlet of the second electro-proportional relief valve; the outlet of the second hydraulically controlled check valve is connected to the lifting end of the pressurizing cylinder through a pressure balancing valve; the outlet of the second electro-proportional relief valve is connected to the oil tank; the second electro-pneumatic directional valve is used to deliver hydraulic oil with a set pressure through the second hydraulically controlled check valve to the lifting end of the pressurizing cylinder when it is open; the second electro-proportional relief valve is used to control the overflow pressure to regulate the force provided by the pressurizing cylinder.

[0015] Furthermore, the second pressure regulating valve includes only a second electro-proportional relief valve. The inlet of the second electro-proportional relief valve is connected to the lifting end of the pressurizing cylinder through a pressurizing balance valve, and the outlet of the second electro-proportional relief valve is connected to the oil tank. The second electro-proportional relief valve is used to control the overflow pressure, thereby regulating the force provided by the pressurizing cylinder.

[0016] Furthermore, the second pressure regulating valve is a combination valve, including a second electro-proportional relief valve and a second electro-hydraulic shut-off valve. The outlet of the second electro-proportional relief valve is connected to the inlet of the second electro-hydraulic shut-off valve, and the outlet of the second electro-hydraulic shut-off valve is connected to the lifting end of the pressure cylinder through a pressure balancing valve.

[0017] Secondly, a constant ground pressure drilling system for a rotary drilling rig is provided, comprising: a first drilling control module, used to maintain a constant ground pressure on the drill bit by adjusting the winch tension when the rotary drilling rig is in a first working condition; wherein, the first working condition refers to a working condition in which the ground pressure on the drill bit is not greater than the sum of the weight of the drill rod and the weight of the drill bit; and a second drilling control module, used to maintain a constant ground pressure on the drill bit by adjusting the force provided by the pressurizing cylinder when the rotary drilling rig is in a second working condition; wherein, the second working condition refers to a working condition in which the ground pressure on the drill bit is not less than the sum of the weight of the drill rod and the weight of the drill bit, and not greater than the sum of the weight of the drill rod, the weight of the power head, and the weight of the drill bit.

[0018] Thirdly, a rotary drilling rig is provided, wherein the rotary drilling rig is equipped with a constant ground pressure drilling system as described in the second aspect.

[0019] Compared with the prior art, the beneficial effects achieved by the present invention are as follows: When the rotary drilling rig is in the first working condition, the ground pressure of the drill bit is kept constant by adjusting the winch tension; wherein, the first working condition refers to the working condition in which the ground pressure of the drill bit is not greater than the sum of the weight of the drill rod and the weight of the drill bit; when the rotary drilling rig is in the second working condition, the ground pressure of the drill bit is kept constant by adjusting the tension of the pressurizing cylinder; wherein, the second working condition refers to the working condition in which the ground pressure of the drill bit is not less than the sum of the weight of the drill rod and the weight of the drill bit, and not greater than the sum of the weight of the drill rod, the weight of the power head and the weight of the drill bit; the present invention can control the rotary drilling rig to maintain a constant pressure within a relatively wide range, meeting the ground pressure requirements of the rotary drilling rig under various working conditions. Attached Figure Description

[0020] Figure 1 This is a schematic diagram of the control principle of a constant ground pressure drilling method for rotary drilling rigs provided in Embodiment 1 of the present invention;

[0021] Figure 2 This is a schematic diagram of the control logic for a constant ground pressure drilling method using a rotary drilling rig, provided in Embodiment 1 of the present invention.

[0022] Figure 3 This is a schematic diagram of the control principle of a constant ground pressure drilling method for rotary drilling rigs provided in Embodiment 2 of the present invention. Figure 1 ;

[0023] Figure 4 This is a schematic diagram of the control principle of a constant ground pressure drilling method for rotary drilling rigs provided in Embodiment 2 of the present invention. Figure 2 ;

[0024] Figure 5 This is a schematic diagram of the control principle of a constant ground pressure drilling method for rotary drilling rigs provided in Embodiment 3 of the present invention;

[0025] In the diagram: 1. Hoist motor; 2. Floating valve; 3. First pressure regulating valve; 31. First electro-proportional relief valve; 32. First electro-optical directional valve; 33. First hydraulic check valve; 34. First electro-optical shut-off valve; 4. Hoist balance valve; 5. Pressurizing cylinder; 6. Second pressure regulating valve; 61. Second electro-proportional relief valve; 62. Second electro-optical directional valve; 63. Second hydraulic check valve; 7. Pressurizing balance valve. Detailed Implementation

[0026] The present invention will be further described below with reference to the accompanying drawings. The following embodiments are only used to more clearly illustrate the technical solution of the present invention, and should not be used to limit the scope of protection of the present invention.

[0027] It should be noted that in the description of this invention, the terms "front," "rear," "left," "right," "upper," "lower," "inner," and "outer," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. These terms are used only for the convenience of describing the invention and do not require the invention to be constructed and operated in a specific orientation; therefore, they should not be construed as limitations on the invention. The terms "front," "rear," "left," "right," "upper," and "lower" used in the description of this invention refer to the directions shown in the accompanying drawings, while the terms "inner" and "outer" refer to directions toward or away from the geometric center of a specific component, respectively.

[0028] In existing technologies, constant pressure drilling schemes exist for working areas with high requirements for drill bit-to-ground pressure F (the force ultimately applied to the ground by the drill bit, called ground pressure, F=F1+G1+G2+G3-F2, where F1 represents the force provided by the pressurized cylinder, which can be positive or negative, i.e., different directions, manifested as pressure or tension; F2 represents the winch tension; G1 represents the weight of the drill rod; G2 represents the weight of the power head; and G3 represents the weight of the drill bit). Specifically, in the high-pressure zone ③, G1+G2+G3<F. However, when the drill bit-to-ground pressure F is in the following ranges, there is a blind zone, making quantitative and stable control impossible: low-pressure zone ① F≤G1+G3, medium-pressure zone ② G1+G3≤F≤G1+G2+G3. This invention provides the following solutions for low-pressure and medium-pressure zone working conditions.

[0029] Example 1:

[0030] A constant ground pressure drilling method for rotary drilling rigs involves maintaining a constant ground pressure on the drill bit by adjusting the winch tension when the rotary drilling rig is in its first working condition.

[0031] The first working condition refers to the condition where the pressure of the drill bit on the ground is not greater than the sum of the weight of the drill rod and the weight of the drill bit, i.e., F≤G1+G3; this condition is commonly seen in special occasions such as gravel construction and interlocking pile construction, where the drill rod needs to be suspended during drilling.

[0032] like Figure 1 , Figure 2 As shown, a floating valve 2 is connected in series between the lifting end working oil port A and the lowering end working oil port B of the hoisting motor 1. The floating valve 2 is used to achieve controllable connection between the lifting end working oil port A and the lowering end working oil port B of the hoisting motor 1.

[0033] When the solenoid valve Y1 at the control end of the floating valve 2 is energized, the floating valve 2 opens. The pressure exchange between the lifting end working port A and the lowering end working port B of the hoisting motor 1 is controlled by adjusting the energizing time of solenoid valve Y1; this time is very brief. The main unit is equipped with a sensor capable of monitoring the magnitude of the hoisting force F2. The opening of the floating valve 2 and the duration of its opening are determined by the magnitude of the hoisting force F2 that needs to be controlled.

[0034] At this point, the drill bit's pressure on the ground, F = F1 + G1 + G2 + G3 - F2. Since the pressurizing cylinder is not activated, F1 and G2 balance and cancel each other out, therefore F = G1 + G3 - F2. This embodiment does not require additional hardware; it achieves the drill bit's pressure adjustment scheme solely through closed-loop control. Its main features include a set target pressure on the ground, F', a winch pull force, F2, and the opening of a floating valve. When the drill bit's pressure on the ground, F, falls below the set target pressure, F', reaching a set deviation value, the solenoid valve Y1 at the control end of the floating valve 2 is energized, causing F2 to decrease, thereby increasing F.

[0035] Maintaining a constant pressure between the drill bit and the ground by adjusting the winch tension specifically includes:

[0036] Collect the ground pressure of the drill bit;

[0037] Determine the difference between the drill bit's pressure on the ground and the set target pressure on the ground, F'.

[0038] When the difference is greater than the set deviation value, a control signal is sent to the control end solenoid valve Y1 of the floating valve 2 to open the floating valve 2, thereby connecting the lifting end working oil port A of the hoisting motor 1 with the lowering end working oil port B, reducing the hoisting tension F2.

[0039] The set deviation value ranges from 0.5 tons to 2 tons. In this invention, it is set to 1 ton, but can be changed to other control targets as needed.

[0040] Example 2:

[0041] A constant ground pressure drilling method for rotary drilling rigs involves maintaining a constant ground pressure on the drill bit by adjusting the winch tension when the rotary drilling rig is in its first working condition.

[0042] The first working condition refers to the condition where the pressure of the drill bit on the ground is not greater than the sum of the weight of the drill rod and the weight of the drill bit, i.e., F≤G1+G3; this condition is commonly seen in special occasions such as gravel construction and interlocking pile construction, where the drill rod needs to be suspended during drilling.

[0043] When F ≤ G1 + G3 is required, the ground pressure F = G1 + G3 - F2, therefore the winch pulling force F2 needs to be adjustable. Figure 3 As shown, a first pressure regulating valve 3 is provided. This valve controls the oil pressure between the load end of the winch balance valve 4 and the working port A of the lifting end of the winch motor 1, thereby regulating the winch pulling force F2. The main function of the winch balance valve 4 is to convert the weight of the load into winch pulling force, while ensuring a smooth lowering process. A one-way oil replenishment valve is provided at the lowering end of the winch motor 1. Its main function is to replenish oil to the lowering end of the winch motor during lowering.

[0044] The first pressure regulating valve 3 is a combination valve, including a first electro-proportional relief valve 31, a first electro-pneumatic directional valve 32, and a first hydraulic check valve 33; the outlet of the first electro-pneumatic directional valve 32 is connected to the inlet of the first hydraulic check valve 33 and the inlet of the first electro-proportional relief valve 31; the outlet of the first hydraulic check valve 33 is connected between the load end of the hoist balance valve 4 and the working oil port A of the hoist motor 1; the outlet of the first electro-proportional relief valve 31 is connected to the oil tank.

[0045] The solenoid valve Y6 at the control end of the first electro-proportional relief valve 31 is used to control the current change of the first electro-proportional relief valve 31, thereby controlling the overflow pressure of the first electro-proportional relief valve 31 and thus adjusting the hoisting force F2. The solenoid valve Y5 at the control end of the first electro-proportional directional valve 32 is used to control the opening of the first electro-proportional directional valve 32, allowing pressurized oil to flow from oil port P to oil port B, thereby opening the first electro-proportional directional valve 32 and delivering hydraulic oil with a set pressure to the lifting end of the hoisting motor 1 through the first hydraulically controlled check valve 33.

[0046] When the solenoid valve Y5 at the control end of the first electrically controlled directional valve 32 is energized, the first hydraulically controlled check valve 33 opens. At this time, the solenoid valve Y6 at the control end of the first electro-proportional relief valve 31 controls the pressure at the lifting end, thereby adjusting the hoisting force F2 to a predetermined range. This allows the ground pressure to be controlled within a certain range.

[0047] This invention relates to a scheme in which a first pressure regulating valve 3 is connected in parallel between the load end of the hoisting balance valve 4 and the hoisting motor 1 to control the hoisting load. The combination of the first hydraulically controlled check valve 33 and the first electrically controlled directional valve 32 is mainly for safety considerations and can be implemented in other ways.

[0048] For example 1: The first electrically controlled directional valve 32 and the first hydraulically controlled check valve 33 can be cancelled; safety can be ensured by setting the overflow pressure of the first electro-proportional relief valve 31.

[0049] For example 2: Figure 4 As shown, a first electrically controlled shut-off valve 34 is used to replace the first electrically controlled directional valve 32 and the first hydraulically controlled check valve 33. The outlet of the first electro-proportional relief valve 31 is connected to the inlet of the first electrically controlled shut-off valve 34, and the outlet of the first electrically controlled shut-off valve 34 is connected between the load end of the hoisting balance valve 4 and the working oil port A of the hoisting motor 1.

[0050] Example 3:

[0051] A constant ground pressure drilling method for rotary drilling rigs, wherein when the rotary drilling rig is in the second working condition, the ground pressure of the drill bit is kept constant by adjusting the force provided by the pressure cylinder.

[0052] The second working condition is the light load working condition. The second working condition refers to the working condition in which the pressure of the drill bit on the ground is not less than the sum of the weight of the drill pipe and the weight of the drill bit, and not greater than the sum of the weight of the drill pipe, the weight of the power head and the weight of the drill bit, that is, G1+G3≤F≤G1+G2+G3.

[0053] When G1+G3≤F≤G1+G2+G3 is required, the ground pressure F=G1+G3+G2-F1. Therefore, the force F1 provided by the pressurized hydraulic cylinder can be adjusted. Figure 5 As shown, a second pressure regulating valve 6 is provided, which is connected in parallel to the lifting end of the pressurizing cylinder 5, and is used to regulate the force provided by the pressurizing cylinder 5.

[0054] The second pressure regulating valve 6 is a combination valve, including a second electro-proportional relief valve 61, a second electro-pneumatic directional valve 62, and a second hydraulic check valve 63; the outlet of the second electro-pneumatic directional valve 62 is connected to the inlet of the second hydraulic check valve 63 and the inlet of the second electro-proportional relief valve 61; the outlet of the second hydraulic check valve 63 is connected to the lifting end of the pressurizing cylinder 5 through a pressurizing balance valve 7; and the outlet of the second electro-proportional relief valve 61 is connected to the oil tank.

[0055] The second electrically controlled directional valve 62 is used to deliver hydraulic oil with a set pressure to the lifting end of the pressurizing cylinder 5 through the second hydraulically controlled check valve 63 when it is open; the second electro-proportional relief valve 61 is used to control the relief pressure to adjust the force provided by the pressurizing cylinder 5.

[0056] When the solenoid valve Y3 at the control end of the second electrically controlled directional valve 62 is energized, the second hydraulically controlled check valve 63 opens. At this time, the control end Y2 of the second electro-proportional relief valve 61 controls the pressure at the lifting end, thereby adjusting the pulling force F1 of the pressurizing cylinder 5, which can control the pressure to the ground within a certain range.

[0057] In this invention, a second pressure regulating valve 6 is connected in parallel between the pressure balancing valve 7 and the pressure cylinder 5 to control the load lifted by the pressure cylinder 5. The combination of the second hydraulically controlled check valve 63 and the second electrically controlled directional valve 62 is mainly for safety considerations and can be implemented in other ways.

[0058] For example, 3: The second hydraulic check valve 63 and the second electric directional valve 62 can be removed, and safety can be ensured by setting the overflow pressure of the second electro-proportional relief valve 61.

[0059] For example 4: The second pressure regulating valve 6 is a combination valve, including a second electro-proportional relief valve 61 and a second electro-operated shut-off valve. The outlet of the second electro-proportional relief valve 61 is connected to the inlet of the second electro-operated shut-off valve, and the outlet of the second electro-operated shut-off valve is connected to the lifting end of the pressure cylinder 5 through the pressure balancing valve 7.

[0060] Example 4:

[0061] This embodiment combines the technical solutions of Embodiments 2 and 3, that is, the first pressure regulating valve 3 and the second pressure regulating valve 6 are the same pressure regulating valve. Under different working conditions, by switching the oil supply direction, the pressure regulating valve can supply oil to the winch motor 1 or the pressurizing cylinder 5.

[0062] Example 5:

[0063] Based on Embodiments 1 to 4, this embodiment provides a constant ground pressure drilling system for a rotary drilling rig, including:

[0064] The first drilling control module is used to maintain a constant ground pressure of the drill bit by adjusting the winch tension when the rotary drilling rig is in the first working condition; wherein, the first working condition refers to the working condition in which the ground pressure of the drill bit is not greater than the sum of the weight of the drill rod and the weight of the drill bit.

[0065] The second drilling control module is used to maintain a constant drill bit pressure on the ground by adjusting the force provided by the pressurizing cylinder when the rotary drilling rig is in the second working condition. The second working condition refers to a working condition in which the drill bit pressure on the ground is not less than the sum of the weight of the drill rod and the weight of the drill bit, and not greater than the sum of the weight of the drill rod, the weight of the power head and the weight of the drill bit.

[0066] Example 6:

[0067] This embodiment provides a rotary drilling rig, which is equipped with a constant ground pressure drilling system as described in Embodiment 5.

[0068] The rotary drilling rig of this invention can control the continuous change of ground pressure within the medium and low pressure range, adapting to more working conditions; it can stabilize the ground pressure output, thereby making the torque and speed fluctuations of the power head smooth, improving work efficiency, reducing equipment fuel consumption, and greatly reducing the operator's workload.

[0069] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the technical principles of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A method for constant ground pressure drilling with a rotary drilling rig, characterized in that, include: When the rotary drilling rig is in its first working condition, the ground pressure F of the drill bit is kept constant by adjusting the winch tension F2. The first working condition refers to the condition where the ground pressure F of the drill bit is not greater than the sum of the weight of the drill rod G1 and the weight of the drill bit G3, i.e., F ≤ G1 + G3. When the pressure cylinder is not activated, the force F1 provided by the pressure cylinder is balanced and canceled out by the weight of the power head G2, resulting in F = G1 + G3 - F2. Collect the ground pressure F of the drill bit; Determine the difference between the drill bit's pressure on the ground F and the set target pressure on the ground F'; When the difference is greater than the set deviation value, a control signal is sent to the solenoid valve at the control end of the floating valve to open the floating valve, thereby connecting the working oil port A at the lifting end of the hoisting motor with the working oil port B at the lowering end, reducing the hoisting tension. Alternatively, a first pressure regulating valve (3) can be set up to control the oil pressure between the load end of the winch balance valve (4) and the working oil port A of the lifting end of the winch motor (1), thereby regulating the winch tension. When the rotary drilling rig is in the second working condition, the force F1 provided by the pressure cylinder is adjusted to keep the drill bit pressure on the ground constant. The second working condition refers to the condition where the drill bit pressure on the ground F is not less than the sum of the weight of the drill rod G1 and the weight of the drill bit G3, and is not greater than the sum of the weight of the drill rod G1, the weight of the power head G2 and the weight of the drill bit G3, that is, G1+G3≤F≤G1+G2+G3, and the ground pressure F=G1+G3+G2-F1. At this time, a second pressure regulating valve (6) is set, which is connected in parallel to the lifting end of the pressurizing cylinder (5) to regulate the force provided by the pressurizing cylinder (5).

2. The constant ground pressure drilling method for rotary drilling rigs according to claim 1, characterized in that, The opening of the floating valve and the duration of its opening are determined by the magnitude of the winch tension F2 that needs to be controlled.

3. The constant ground pressure drilling method for rotary drilling rigs according to claim 1, characterized in that, The set deviation value ranges from 0.5 tons to 2 tons.

4. The constant ground pressure drilling method for rotary drilling rigs according to claim 1, characterized in that, The first pressure regulating valve (3) is a combination valve, including a first electro-proportional relief valve (31), a first electro-controlled directional valve (32), and a first hydraulically controlled check valve (33); the outlet of the first electro-controlled directional valve (32) is connected to the inlet of the first hydraulically controlled check valve (33) and the inlet of the first electro-proportional relief valve (31); the outlet of the first hydraulically controlled check valve (33) is connected between the load end of the winch balance valve (4) and the working port A of the lifting end of the winch motor (1); the outlet of the first electro-proportional relief valve (31) is connected to the oil tank. The first electrically controlled directional valve (32) is used to deliver hydraulic oil with a set pressure to the lifting end of the winch motor (1) through the first hydraulically controlled check valve (33) when it is open; the first electro-proportional relief valve (31) is used to control the relief pressure to adjust the winch tension.

5. The constant ground pressure drilling method for rotary drilling rigs according to claim 1, characterized in that, The first pressure regulating valve (3) includes only the first electro-proportional relief valve (31). The inlet of the first electro-proportional relief valve (31) is connected between the load end of the winch balance valve (4) and the working port A of the lifting end of the winch motor (1). The outlet of the first electro-proportional relief valve (31) is connected to the oil tank. The first electro-proportional relief valve (31) is used to control the overflow pressure to adjust the winch tension.

6. The constant ground pressure drilling method for rotary drilling rigs according to claim 1, characterized in that, The first pressure regulating valve (3) is a combination valve, including a first electro-proportional relief valve (31) and a first electro-controllable shut-off valve (34). The outlet of the first electro-proportional relief valve (31) is connected to the inlet of the first electro-controllable shut-off valve (34), and the outlet of the first electro-controllable shut-off valve (34) is connected between the load end of the hoisting balance valve (4) and the working port A of the hoisting motor (1).

7. The constant ground pressure drilling method for rotary drilling rigs according to claim 1, characterized in that, The second pressure regulating valve (6) is a combination valve, including a second electro-proportional relief valve (61), a second electro-pneumatic directional valve (62), and a second hydraulic check valve (63); the outlet of the second electro-pneumatic directional valve (62) is connected to the inlet of the second hydraulic check valve (63) and the inlet of the second electro-proportional relief valve (61); the outlet of the second hydraulic check valve (63) is connected to the lifting end of the pressurizing cylinder (5) through a pressurizing balance valve (7); the outlet of the second electro-proportional relief valve (61) is connected to the oil tank; The second electrically controlled directional valve (62) is used to deliver hydraulic oil with a set pressure to the lifting end of the pressurizing cylinder (5) through the second hydraulically controlled check valve (63) when it is open; the second electro-proportional relief valve (61) is used to control the relief pressure to adjust the force provided by the pressurizing cylinder (5).

8. The constant ground pressure drilling method for rotary drilling rigs according to claim 1, characterized in that, The second pressure regulating valve (6) includes only the second electro-proportional relief valve (61). The inlet of the second electro-proportional relief valve (61) is connected to the lifting end of the pressurizing cylinder (5) through the pressurizing balance valve (7). The outlet of the second electro-proportional relief valve (61) is connected to the oil tank. The second electro-proportional relief valve (61) is used to control the overflow pressure to regulate the force provided by the pressurizing cylinder (5).

9. The constant ground pressure drilling method for rotary drilling rigs according to claim 1, characterized in that, The second pressure regulating valve (6) is a combination valve, including a second electro-proportional relief valve (61) and a second electro-operated shut-off valve. The outlet of the second electro-proportional relief valve (61) is connected to the inlet of the second electro-operated shut-off valve, and the outlet of the second electro-operated shut-off valve is connected to the lifting end of the pressure cylinder (5) through the pressure balancing valve (7).

10. A constant ground pressure drilling system for a rotary drilling rig, characterized in that, include: The first drilling control module is used to maintain a constant drill bit pressure on the ground F by adjusting the winch pull force F2 when the rotary drilling rig is in the first working condition. The first working condition refers to the condition where the drill bit pressure on the ground F is not greater than the sum of the drill rod weight G1 and the drill bit weight G3, i.e., F ≤ G1 + G3. When the pressure cylinder is not activated, the force F1 provided by the pressure cylinder balances and cancels out the weight G2 of the power head, resulting in F = G1 + G3 - F2. Collect the ground pressure F of the drill bit; Determine the difference between the drill bit's pressure on the ground F and the set target pressure on the ground F'; When the difference is greater than the set deviation value, a control signal is sent to the solenoid valve at the control end of the floating valve to open the floating valve, thereby connecting the working oil port A at the lifting end of the hoisting motor with the working oil port B at the lowering end, reducing the hoisting tension. Alternatively, a first pressure regulating valve (3) can be set up to control the oil pressure between the load end of the winch balance valve (4) and the working oil port A of the lifting end of the winch motor (1), thereby regulating the winch tension. The second drilling control module is used to maintain the constant ground pressure F of the drill bit by adjusting the force F1 provided by the pressure cylinder when the rotary drilling rig is in the second working condition. The second working condition refers to the working condition in which the ground pressure F of the drill bit is not less than the sum of the weight of the drill rod G1 and the weight of the drill bit G3, and is not greater than the sum of the weight of the drill rod G1, the weight of the power head G2 and the weight of the drill bit G3, that is, G1+G3≤F≤G1+G2+G3, and the ground pressure F=G1+G3+G2-F1. At this time, a second pressure regulating valve (6) is set, which is connected in parallel to the lifting end of the pressurizing cylinder (5) to regulate the force provided by the pressurizing cylinder (5).

11. A rotary drilling rig, characterized in that, The rotary drilling rig is equipped with a constant ground pressure drilling system as described in claim 10.

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