Rock strength real-time identification system and method based on PDC drill bit drilling parameters

Abstract

The invention provides a rock strength real-time identification system and method based on PDC drill bit drilling parameters. The system comprises a mining full-hydraulic underground drill rig, a hydraulic system, a data acquisition system and an upper computer, power and control are provided through the hydraulic system, the data acquisition system acquires parameters such as the rotating speed of a drill bit and propelling oil pressure in real time, and the upper computer receives, calculates and outputs rock strength. The method comprises the steps that drilling parameters are obtained in real time, and key parameters are calculated after filtering and conversion; a PDC tooth cutting rock mechanical model is established, analysis is carried out in the press-in stage and the rotary cutting stage, and real-time parameters are substituted to calculate the compressive strength, cohesion and internal friction angle of the rock; and integrating the results of the two stages, outputting the rock strength in real time, and identifying the anisotropism of the rock stratum interface and the rock mass. The problem of rock strength identification in a drilling and blasting method is solved, the roadway drilling and blasting process can be optimized, the over-excavation phenomenon is reduced, and the stability of the roadway structure is guaranteed.

Description

Technical Field

[0001] The present invention relates to the technical field of rock property identification, and in particular to a system and method for real-time identification of rock strength based on PDC drill bit drilling parameters. Background Art

[0002] Coal is a black or brownish-black solid, combustible mineral with a dull luster and a brittle texture. Formed from plant debris through geological processes, it is known as the "food of industry." Coal is primarily found in coal seams within the Earth's crust and is a key target of geological exploration. Its primary components include carbon, hydrogen, oxygen, nitrogen, sulfur, and phosphorus, along with smaller amounts of other elements such as chlorine and fluorine. The carbon content is relatively high, generally ranging from 60% to 95%. Coal is an important solid fuel and chemical raw material. Its combustion generates heat for use in power generation, heating, industrial production, and other applications. Processing can also convert it into a variety of chemical products, including coke and coal tar.

[0003] Drilling and blasting is a mainstream technology used in tunnel engineering and mining. By pre-placed explosives in the rock, the energy released by the explosion shatters the rock, enabling rapid tunnel advancement. However, overexcavation occurs in the application of drilling and blasting, manifesting as deviations from the designed tunnel contour. This phenomenon is caused by multiple factors, including geological conditions, drilling accuracy, and blasting parameter compatibility. This engineering deviation leads to increased slag discharge, higher initial support costs, and threats to tunnel structural stability. The key to optimizing tunnel drilling and blasting technology lies in accurately identifying the rock strength of the area to be blasted, which directly determines the selection of blasting parameters and the surrounding rock stability control strategy.

[0004] In view of this, in order to overcome the above technical problems, the present invention proposes a real-time rock strength identification method and system based on PDC drill bit drilling parameters, which solves the above technical problems. Summary of the Invention

[0005] The technical problem to be solved by the present invention is to overcome the above technical defects and provide a real-time rock strength identification system based on PDC drill bit drilling parameters, comprising:

[0006] Fully hydraulic tunnel drilling rig for mining;

[0007] A hydraulic system, providing power and control for the fully hydraulic tunnel drilling rig for mining;

[0008] Data acquisition system, used to collect multiple parameters during the drilling process in real time;

[0009] The host computer receives the sensor data transmitted by the data acquisition system, calculates and outputs the rock strength in real time.

[0010] As preferred in this application, the fully hydraulic tunnel drilling rig for mining includes:

[0011] guide;

[0012] A hydraulic motor is slidably arranged on the guide rail via a guide seat;

[0013] A reducer, the output end of which matches the input end of the hydraulic motor;

[0014] a hydraulic chuck, fixed to the output shaft of the hydraulic motor;

[0015] a drill rod, the fixed end of which is clamped on the hydraulic chuck;

[0016] a drill bit connected to the output end of the drill rod;

[0017] a holder fixed on the guide rail, wherein the drill rod passes through the holder and is in sliding engagement with the holder;

[0018] The hydraulic cylinder is used to drive the guide seat connected to the hydraulic motor to move along the guide rail.

[0019] As preferred in this application, the hydraulic system includes:

[0020] A hydraulic pump A, whose oil inlet is connected to the oil tank, and whose oil outlet is sequentially connected to a three-position four-way manual reversing valve A, a speed regulating valve, and the hydraulic motor; the oil return end of the hydraulic motor is connected back to the oil tank through the three-position four-way manual reversing valve A;

[0021] A hydraulic pump B, whose oil inlet is connected to the oil tank, and whose oil outlet is sequentially connected to a pressure reducing valve, a three-position four-way manual reversing valve B, and the rodless chamber of the hydraulic cylinder. The rod chamber of the hydraulic cylinder is connected back to the oil tank via a two-position three-way manual reversing valve;

[0022] The oil inlet pipeline of the hydraulic chuck is connected in parallel with the inlet of the pressure reducing valve, and its clamping or releasing state is controlled by the two-position three-way manual reversing valve;

[0023] As preferred in this application, the data acquisition system includes:

[0024] A Hall speed sensor is installed on the reducer and is used to calculate the drill bit speed by detecting the pulse signal of the metal bumps on the surface of the drill rod;

[0025] A propulsion oil pressure sensor is connected to the oil return line of the rodless chamber of the hydraulic cylinder through a tee joint, and is used to measure the propulsion oil pressure to indirectly calculate the propulsion force;

[0026] A rotary oil pressure sensor is connected to the oil return line of the hydraulic motor through a tee connector and is used to measure the rotary oil pressure to indirectly calculate the torque;

[0027] A displacement sensor is installed between the guide rail and the reducer, and is used to monitor the axial displacement of the drill bit in real time to calculate the drilling speed;

[0028] a flow sensor installed in the hydraulic motor circuit to measure its flow rate for indirect calculation of torque;

[0029] An acceleration sensor is installed in the hollow part of the drill rod, fixed by a magnet and connected to a data acquisition card for detecting vibration signals;

[0030] The host computer receives data from the Hall speed sensor, propulsion oil pressure sensor, rotation oil pressure sensor (II-61), displacement sensor, flow sensor and acceleration sensor, transmits the data through the data acquisition card, and executes the rock strength identification algorithm.

[0031] As a preferred embodiment of the present application, the oil outlets of the hydraulic pump A and the hydraulic pump B are both provided with overflow pipes connected to the oil tank, and the overflow pipes are provided with overflow valves.

[0032] As a preferred embodiment of the present application, the distance between the probe of the Hall speed sensor and the metal bumps on the surface of the drill rod is 5 mm, and the speed is calculated by counting the high-level pulses triggered by the metal bumps.

[0033] As a preferred embodiment of the present application, the power line and signal line of the acceleration sensor pass through the middle hole of the drill rod and are connected to the data acquisition card through brushes.

[0034] The present application also provides a method for real-time identification of rock strength based on PDC drill bit drilling parameters, comprising the following steps:

[0035] S1: The data acquisition system is used to obtain the parameters of the drill bit during the drilling process, including drill bit speed, propulsion oil pressure, rotation oil pressure, drilling speed, vibration signal, and torque. The data acquisition card is used to filter the signals and perform AD conversion. The data processing module then calculates the drill bit speed, propulsion force, torque, drilling speed, and vibration spectrum characteristics.

[0036] S2: A mechanical model is established based on the rock cutting process of PDC teeth, and the cutting process is divided into two stages: pressing and peeling;

[0037] S3: Perform mechanical analysis on the compression stage and calculate the rock compressive strength by using the real-time collected parameters such as the thrust force and compression area;

[0038] S4: Perform mechanical analysis on the peeling stage, combine the Mohr-Coulomb criterion, and substitute parameters such as torque and axial acceleration to calculate the rock cohesion and internal friction angle;

[0039] S5: The calculation results of the compression stage and the rotary cutting stage are integrated to output the rock strength in real time and identify the heterogeneity of the rock layer interface and rock mass.

[0040] As a priority of this application, the mechanical model calculation formula of the pressing stage in step S3 includes:

[0041]

[0042] The solution is:

[0043] F1=k0σ c B0+μF N1 cosα+μF N2 sinα=kσ c B0

[0044] Where: k0 is the ratio of the actual indentation area to the theoretical indentation area; k5 is the ratio of the wear area to the indentation area; F N 、F N1 、F N2 is the normal force; F f1 、F f2 is the friction force; μ is the friction coefficient; σ c is the compressive strength of rock; A0 is the wear area; B0 is the intrusion area.

[0045] As a priority of this application, the mechanical model calculation formula of the peeling stage in step S4 includes:

[0046]

[0047] According to the Mohr-Coulomb criterion, the relationship between σ and τ can be obtained:

[0048]

[0049] The solution is:

[0050]

[0051] Where: M is the mass of the drill string system; a is the axial acceleration; T is the torque; R is the rotation radius of the PDC tooth; c is the cohesive force; is the internal friction angle.

[0052] Simplifying the formula:

[0053]

[0054] Where: k2, k3, k4, k5 are all simplified coefficients.

[0055] The present invention proposes a method and system for real-time identification of rock strength based on PDC drill bit drilling parameters. The system includes a fully hydraulic tunnel drill for mining, a hydraulic system, a data acquisition system and a host computer. The hydraulic system provides power and control, and the data acquisition system collects parameters such as drill bit speed and propulsion oil pressure in real time. The host computer receives and calculates the output rock strength. The method includes obtaining drilling parameters in real time, calculating key parameters after filtering and conversion; establishing a PDC tooth cutting rock mechanics model, analyzing the pressure-in and rotary cutting stages, and substituting real-time parameters to calculate the rock compressive strength, cohesion and internal friction angle; integrating the results of the two stages, outputting rock strength in real time, and identifying the rock layer interface and rock mass heterogeneity. The present invention solves the problem of rock strength identification in the drilling and blasting method, helps to optimize the tunnel drilling and blasting process, reduce over-excavation, and ensure the stability of the tunnel structure. BRIEF DESCRIPTION OF THE DRAWINGS

[0056] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the following briefly introduces the drawings required for describing the embodiments. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without creative work.

[0057] Figure 1 A schematic diagram of the structure of a fully hydraulic tunnel drill for mining in a real-time rock strength identification system based on PDC drill bit drilling parameters provided by an embodiment of the present invention;

[0058] Figure 2 A schematic diagram of the structure of a fully hydraulic tunnel drill for mining in a real-time rock strength identification system based on PDC drill bit drilling parameters provided by an embodiment of the present invention;

[0059] Figure 3 A schematic diagram of a hydraulic system for a real-time rock strength identification system based on PDC drill bit drilling parameters provided by an embodiment of the present invention;

[0060] Figure 4 A flow chart of a data acquisition system for a real-time rock strength identification method based on PDC drill bit drilling parameters provided by an embodiment of the present invention;

[0061] Figure 5 A schematic diagram of drilling speed feedback adjustment principle of a method for real-time identification of rock strength based on PDC drill bit drilling parameters provided by an embodiment of the present invention;

[0062] Figure 6 A diagram of the rock cutting mechanism of PDC teeth according to a method for real-time identification of rock strength based on PDC drill bit drilling parameters provided by an embodiment of the present invention;

[0063] Figure 7A rock strength identification model diagram of a real-time rock strength identification method based on PDC drill bit drilling parameters provided by an embodiment of the present invention;

[0064] Figure 8 A rock strength recognition effect diagram of a real-time rock strength recognition method based on PDC drill bit drilling parameters provided by an embodiment of the present invention.

[0065] As shown in the figure: Ⅰ-1, guide rail; Ⅰ-2, speed sensor; Ⅰ-3, hydraulic motor; Ⅰ-4, reducer; Ⅰ-5, hydraulic chuck; Ⅰ-6, drill rod; Ⅰ-7, displacement sensor; Ⅰ-8, clamp; Ⅰ-9, drill bit; Ⅱ-1, overflow valve; Ⅱ-2, hydraulic pump A; Ⅱ-21, hydraulic pump B; Ⅱ-3, three-position four-way manual reversing valve A; Ⅱ-31, three-position four-way manual reversing valve B; Ⅱ-4, speed control valve; Ⅱ-5, flow sensor; Ⅱ-6, propulsion oil pressure sensor; Ⅱ-61, rotation oil pressure sensor; Ⅱ-7, pressure reducing valve; Ⅱ-8, hydraulic cylinder; Ⅱ-9, two-position three-way manual reversing valve. DETAILED DESCRIPTION

[0066] The present invention will be described in further detail below with reference to the accompanying drawings.

[0067] The specific embodiments of the present invention are further described below with reference to the accompanying drawings, wherein the same parts are represented by the same reference numerals.

[0068] It should be noted that the words "front", "rear", "left", "right", "up" and "down" used in the following description refer to directions in the accompanying drawings, and the words "inside" and "outside" refer to directions toward or away from the geometric center of a specific component, respectively.

[0069] In order to make the contents of the present invention more clearly understood, the technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present invention.

[0070] Reference Attachment Figure 1 -Attached Figure 6 , a real-time rock strength identification system based on PDC drill bit drilling parameters, including:

[0071] Fully hydraulic tunnel drilling rig for mining;

[0072] A hydraulic system, providing power and control for the fully hydraulic tunnel drilling rig for mining;

[0073] Data acquisition system, used to collect multiple parameters during the drilling process in real time;

[0074] The host computer receives the sensor data transmitted by the data acquisition system, calculates and outputs the rock strength in real time.

[0075] The fully hydraulic tunnel drill for mining is the core executive component of the entire system, and its specific structure is as follows:

[0076] First, guide rail I-1 provides the basic track for the entire drilling rig, ensuring that all components can move in the intended direction. Hydraulic motor I-3 slides on guide rail I-1 via a guide seat. This design allows for flexible linear motion of hydraulic motor I-3 along the guide rail. The output of reducer I-4 mates with the input of hydraulic motor I-3, reducing its speed while increasing torque to meet the demands of drilling operations.

[0077] A hydraulic chuck (I-5) is fixed to the output shaft of hydraulic motor (I-3). It securely holds drill rod (I-6) to prevent it from loosening or falling out during drilling. The fixed end of drill rod (I-6) is clamped to hydraulic chuck (I-5), while its output end is connected to drill bit (I-9), which directly contacts the rock to achieve the drilling operation.

[0078] Clamp I-8 is fixed to guide rail I-1, and the drill rod I-6 passes through clamp I-8 and slides with clamp I-8. Clamp I-8 provides auxiliary support and stability for the drill rod I-6 during the drilling process, preventing excessive vibration during high-speed rotation and propulsion.

[0079] Hydraulic cylinder II-8 is used to drive the guide seat connected to the hydraulic motor I-3 to move along the guide rail I-1. The telescopic movement of hydraulic cylinder II-8 can control the advancement and retreat of the drill bit I-9, thereby achieving precise control of the drilling depth. As a preferred embodiment of this application, the hydraulic system provides power and control for a fully hydraulic tunnel drill rig for mining. Its specific structure and operating principle are as follows:

[0080] Hydraulic pump AⅡ-2 is one of the power sources for the hydraulic system. Its oil inlet is connected to the oil tank, and its oil outlet is connected in sequence to a three-position, four-way manual reversing valve AⅡ-3, a speed regulating valve II-4, and the hydraulic motor I-3. The oil return port of the hydraulic motor I-3 is connected back to the oil tank via the three-position, four-way manual reversing valve AⅡ-3. The three-position, four-way manual reversing valve AⅡ-3 controls the flow of hydraulic oil, thereby changing the rotation direction of the hydraulic motor I-3. The speed regulating valve II-4 adjusts the flow of hydraulic oil entering the hydraulic motor I-3, thereby controlling its speed.

[0081] Hydraulic pump BⅡ-21 is also a key power source for the hydraulic system. Its oil inlet is connected to the fuel tank, and its oil outlet is connected in sequence to pressure-reducing valve II-7, three-position, four-way manual reversing valve BⅡ-31, and the rodless chamber of hydraulic cylinder II-8. The rod chamber of hydraulic cylinder II-8 is connected back to the fuel tank via two-position, three-way manual reversing valve II-9. Pressure-reducing valve II-7 stabilizes the pressure supplied to hydraulic cylinder II-8, ensuring smooth operation. The three-position, four-way manual reversing valve BⅡ-31 controls the extension and retraction direction of hydraulic cylinder II-8. The two-position, three-way manual reversing valve II-9 controls the return oil from the rod chamber of hydraulic cylinder II-8.

[0082] The oil inlet line of hydraulic chuck I-5 is connected in parallel to the inlet of pressure-reducing valve II-7, and its clamping and loosening states are controlled by two-position, three-way manual reversing valve II-9. To clamp drill rod I-6, hydraulic oil enters hydraulic chuck I-5 through two-position, three-way manual reversing valve II-9, achieving the clamping action. To loosen drill rod I-6, the hydraulic oil returns to the tank through two-position, three-way manual reversing valve II-9, releasing hydraulic chuck I-5.

[0083] The hydraulic system's oil pressure generation and regulation mechanism follows Pascal's principle. Input flow is converted into system pressure by hydraulic pumps (II-2, II-21). The oil pressure output by hydraulic pump BII-21 is dynamically regulated by pressure reducing valve II-7. This direct-acting valve features fast response and high regulation accuracy, ensuring stable pressure supply to hydraulic cylinder II-8 and hydraulic chuck I-5. Hydraulic system pressure is determined by the load. The load generated by the machine-rock interaction is fed back to the oil pressure system via hydraulic cylinder II-8, creating a closed-loop pressure control system that adaptively matches drilling speed and thrust, thereby improving drilling efficiency and stability.

[0084] In one embodiment, the data acquisition system is a key part of the entire system. It is responsible for real-time acquisition of various parameters during the drilling process, providing data support for subsequent rock strength identification. Specifically, it includes the following sensors:

[0085] Hall-effect speed sensor I-2, mounted on reducer I-4, calculates the drill bit speed by detecting pulse signals from metal bumps on the surface of drill rod I-6. As drill rod I-6 rotates, the metal bumps periodically pass by the probe of Hall-effect speed sensor I-2, generating pulse signals. By counting the number and time intervals of these pulse signals, the drill rod I-6 speed, and thus the drill bit speed, can be calculated.

[0086] Propulsion oil pressure sensor II-6 is connected to the rodless chamber return line of hydraulic cylinder II-8 via a T-joint. It measures propulsion oil pressure and indirectly calculates propulsion force. During the drilling process, hydraulic cylinder II-8 propels the drill bit forward. The oil pressure in the rodless chamber is related to the propulsion force. By measuring propulsion oil pressure and combining it with relevant hydraulic system parameters, the propulsion force can be indirectly calculated.

[0087] Rotational oil pressure sensor II-61 is connected to the oil return line of hydraulic motor I-3 via a T-connector. It measures the rotational oil pressure and indirectly calculates the torque. As hydraulic motor I-3 rotates, the oil pressure in its return line is related to the torque. By measuring the rotational oil pressure, the torque can be indirectly calculated.

[0088] Displacement sensor I-7 is installed between guide rail I-1 and reducer I-4. It monitors the drill bit's axial displacement in real time to calculate the drilling speed. During the drilling process, the drill bit moves forward along guide rail I-1. Displacement sensor I-7 monitors the drill bit's axial displacement in real time. By calculating the displacement per unit time, the drilling speed can be calculated.

[0089] Flow sensor II-5 is installed in the circuit of hydraulic motor I-3 to measure its flow rate, which is used to indirectly calculate torque. The flow rate of hydraulic motor I-3 is related to torque. By measuring the flow rate and combining it with other hydraulic system parameters, the torque can be indirectly calculated.

[0090] An accelerometer is installed in the hollow of Drill Rod I-6, secured by magnets and connected to a data acquisition card to detect vibration signals. During drilling, Drill Rod I-6 vibrates, and the accelerometer detects these vibration signals in real time and transmits them to the data acquisition card, providing additional information for subsequent rock strength analysis.

[0091] The host computer receives data from Hall effect sensor I-2, propulsion oil pressure sensor II-6, rotary oil pressure sensor II-61, displacement sensor I-7, flow sensor II-5, and acceleration sensor, transmits it via the data acquisition card, and executes the rock strength identification algorithm. The data acquisition card converts the analog signals collected by the sensors into digital signals and transmits them to the host computer, which analyzes and processes these data according to a preset algorithm, thereby achieving real-time identification of rock strength.

[0092] In one embodiment, the oil outlets of hydraulic pumps AⅡ-2 and BⅡ-21 are each equipped with an overflow line connected to the oil tank, and each overflow line is equipped with a relief valve II-1. When the hydraulic system pressure exceeds a set value, relief valve II-1 automatically opens, allowing excess hydraulic oil to flow back to the tank, thereby protecting the hydraulic system and stabilizing system pressure. This design prevents damage to equipment due to excessive hydraulic pressure, ensuring safe and stable operation of the hydraulic system.

[0093] In one embodiment, the distance between the probe of Hall-effect speed sensor I-2 and the metal bumps on the surface of drill rod I-6 is 5 mm. The rotational speed is calculated by counting the high-level pulses triggered by the metal bumps. Setting the distance between the probe and the metal bumps to 5 mm ensures that the sensor can accurately detect the magnetic field changes generated by the metal bumps, thereby generating a stable high-level pulse signal. By counting the number of high-level pulses per unit time, the rotational speed of drill rod I-6 can be calculated. This measurement method is characterized by high accuracy and reliability.

[0094] In one embodiment, the accelerometer's power and signal cables pass through the center hole of drill rod I-6 and are connected to the data acquisition card via brushes. Since the accelerometer is installed in the hollow space of drill rod I-6, to ensure power supply and signal transmission, the power and signal cables are passed through the center hole of drill rod I-6 and connected to the data acquisition card via brushes. The brush design ensures that the power and signal cables remain stably connected to the data acquisition card during drill rod I-6 rotation, preventing data interruptions caused by tangled or broken cables and thus ensuring the proper functioning of the accelerometer.

[0095] The present application also provides a method for real-time identification of rock strength based on PDC drill bit drilling parameters, comprising the following steps:

[0096] S1: The data acquisition system acquires real-time parameters during the drilling process, including drill bit speed, thrust oil pressure, rotary oil pressure, drilling speed, vibration signal, and torque. These parameters serve as essential data for subsequent rock strength identification and are accurately captured in real time by the various sensors in the data acquisition system. The data acquisition card then performs signal filtering and A / D conversion, converting the analog signals collected by the sensors into digital signals and removing noise interference to improve signal quality. The data processing module then calculates drill bit speed, thrust force, torque, drilling speed, and vibration spectrum characteristics, providing accurate parameters for subsequent mechanical analysis and rock strength calculations.

[0097] S2: A mechanical model was established based on the rock-cutting process of PDC cutters, dividing the cutting process into two phases: penetration and rotary cutting. A polycrystalline diamond compact drill bit consists of multiple polycrystalline diamond compacts and a matrix. Because the matrix wear coefficient is much greater than that of the diamond compacts, the force acting on the drill bit is actually the combined force of the loads on multiple cutters. Analyzing the rock-breaking process of a PDC drill bit is essentially analyzing a single cutter. Dividing the PDC cutter's cutting process into two phases, penetration and rotary cutting, more accurately describes the interaction between the PDC cutter and the rock, providing a reasonable model foundation for subsequent mechanical analysis.

[0098] S3: Perform a mechanical analysis of the penetration phase, substituting the real-time collected parameters such as the thrust force and penetration area to calculate the rock compressive strength. During the penetration phase, the PDC teeth press vertically into the rock surface. By establishing the corresponding mechanical equation and substituting the real-time collected parameters such as the thrust force and penetration area, the rock compressive strength can be calculated. The specific calculation formula is as follows:

[0099]

[0100] The solution is:

[0101] F1=k0σ c B0+μF N1 cosα+μF N2 sinα=kσ c B0

[0102] Where: k0 is the ratio of the actual indentation area to the theoretical indentation area; k5 is the ratio of the wear area to the indentation area; F N 、F N1 、F N2 is the normal force; F f1 、F f2 is the friction force; μ is the friction coefficient; σ c is the compressive strength of rock; A0 is the wear area; B0 is the intrusion area.

[0103] According to the established rock strength identification method, the drilling experiment of PDC drill bit was carried out, and the experimental data obtained were subjected to nonlinear fitting according to the identification method. Figure 7 The multivariate nonlinear regression model can be used to know the surface fitting coefficient R 2 =0.8542, the surface fitting priority is higher, and the final formula of the multivariate nonlinear regression model is:

[0104]

[0105] Where: σ c is the rock compressive strength, MPa; F is the total thrust, kN; B0(c1,h) is the single tooth intrusion area, mm 2.

[0106] The fitting coefficient R of the multivariate nonlinear regression model in the figure 2 =0.8542, which shows that the model has a higher fitting preference. In addition, since no tests were conducted on rocks with a compressive strength below 60 MPa, this regression model can only be used to identify rocks with a uniaxial compressive strength greater than 60 MPa.

[0107] S4: Perform mechanical analysis on the rotary cutting stage, and combine the Mohr-Coulomb criterion to substitute parameters such as torque and axial acceleration to calculate the rock cohesion and internal friction angle. During the rotary cutting stage, the PDC teeth cut the rock while rotating. By establishing a mechanical model of the rotary cutting stage and combining it with the Mohr-Coulomb criterion, the relationship between σ and τ can be established, and then the parameters such as torque and axial acceleration can be substituted to calculate the rock cohesion and internal friction angle. As a priority of this application, the calculation formula of the mechanical model of the rotary cutting stage in step S4 includes:

[0108]

[0109] According to the Mohr-Coulomb criterion, the relationship between σ and τ can be obtained:

[0110]

[0111] The solution is:

[0112]

[0113] Where: M is the mass of the drill string system; a is the axial acceleration; T is the torque; R is the rotation radius of the PDC tooth; c is the cohesive force; is the internal friction angle.

[0114] Simplifying the formula:

[0115]

[0116] Where: k2, k3, k4, k5 are all simplified coefficients.

[0117] S5: Integrating the calculation results from the injection and rotary shearing stages, the system outputs real-time rock strength and identifies heterogeneity between rock interfaces and the rock mass. By combining the calculation results from the injection and rotary shearing stages, a more comprehensive and accurate understanding of rock strength characteristics is achieved. Furthermore, based on the changes in rock strength, heterogeneity between rock interfaces and the rock mass can be identified, providing important reference for geological exploration and engineering construction.

[0118] like Figure 8Drilling experiments were conducted in composite rock formations, and predictions were made based on the established rock strength identification method. The figure shows how rock strength changes with changing rock formation properties. The predicted uniaxial compressive strength for the 0-30mm layer in the composite rock sample was 69.88 MPa, with a mean difference of 4.6%, which is close to the actual value and exhibits low dispersion, resulting in good prediction results. The predicted value for the 30-60mm layer was 109.5 MPa, with a mean difference of only 1.13%, but also exhibiting low dispersion, resulting in good identification results. The predicted value for the 60-90mm layer was 130.41 MPa, differing by 13.4 MPa from the actual compressive strength with a difference of 9.32%, but exhibiting high dispersion and significant fluctuations, resulting in good identification results. Drilling experiments in these composite rock formations verified the effectiveness and feasibility of the identification model for composite rock formations.

[0119] Working principle and applicable conditions:

[0120] Under the same thrust and rotational speed, the penetration rate of a PDC drill bit in the same rock type remains constant. However, a sudden increase in penetration rate during testing will increase the cutter engagement area, which is proportional to the thrust. The hydraulic system's oil pressure, determined by the load, ultimately increases. Because a pressure reducing valve is installed in the oil circuit to maintain a constant outlet pressure, the valve increases its opening area, allowing more hydraulic oil to flow back to the tank, thereby maintaining a constant outlet pressure. This reduces the penetration rate and maintains a constant penetration rate.

[0121] There are many types of drilling rigs on the market, and the test results are not applicable to other drilling rigs. Based on the adjustment principle of the drill bit drilling speed, the applicable conditions of the test results are summarized as follows:

[0122] The feed direction is hydraulically driven: the drill rig's axial feed is driven by a hydraulic cylinder, with the propulsion oil pressure regulated by a pressure reducing valve. After the propulsion force is set, the relationship between the propulsion force, rock strength, and drilling speed, as well as the pressure reducing valve's regulation of the outlet oil pressure, controls the hydraulic oil flow in the propulsion cylinder, thereby adjusting the drill bit feed speed. This hydraulic drive method enables precise control of the drill bit feed speed, ensuring stable and accurate drilling operations.

[0123] The test results apply only to cylindrical PDC cutters: The theoretical derivation and experimental work were conducted using cylindrical PDC cutters. The geometric and mechanical models for special-shaped cutters were not derived. Therefore, the test results apply only to cylindrical PDC cutters. Different PDC cutters exhibit varying mechanical properties and rock-breaking performance when cutting rock. Therefore, careful consideration must be given to matching the drill bit type when using this method.

[0124] The no-load speed is greater than the drilling speed during the rock breaking process: Establishing the relationship between rock strength and drilling speed requires eliminating the limitation of flow rate on drilling speed, that is, the no-load speed of the drill bit is greater than the drilling speed of the drill bit in the rock, and in order to prevent the drill bit from getting stuck, the ratio of the no-load speed to the drilling speed should not be too large. This ensures that the drill bit can smoothly cut the rock during the drilling process, avoiding inaccurate data or equipment damage caused by problems such as flow rate limitation or drill sticking. In the description of this specification, the description with reference to the terms "one embodiment", "example", etc. means that the specific features, structures, materials or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the schematic representation of the above terms does not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described may be combined in a suitable manner in any one or more embodiments or examples.

[0125] The present invention and its embodiments are described above. This description is not restrictive. The drawings show only one embodiment of the present invention, and the actual structure is not limited thereto. In short, if a person skilled in the art is inspired by this and, without departing from the purpose of the present invention, designs structures and embodiments similar to this technical solution without inventiveness, they shall fall within the scope of protection of the present invention.

Claims

1. A real-time rock strength identification system based on PDC drill bit drilling parameters, characterized in that: include: Fully hydraulic tunnel drilling rig for mining; A hydraulic system, providing power and control for the fully hydraulic tunnel drilling rig for mining; Data acquisition system, used to collect multiple parameters during the drilling process in real time; The host computer receives the sensor data transmitted by the data acquisition system, calculates and outputs the rock strength in real time.

2. A rock strength real-time identification system based on PDC drill bit drilling parameters according to claim 1, characterized in that: The fully hydraulic tunnel drilling rig for mining comprises: Guide rail (Ⅰ-1); A hydraulic motor (I-3) is slidably arranged on the guide rail (I-1) via a guide seat; A reducer (Ⅰ-4), the output end of which is matched with the input end of the hydraulic motor (Ⅰ-3); A hydraulic chuck (I-5) is fixed on the output shaft of the hydraulic motor (I-3); A drill rod (Ⅰ-6), the fixed end of which is clamped on the hydraulic chuck (Ⅰ-5); A drill bit (I-9), connected to the output end of the drill rod (I-6); A holder (I-8) is fixed on the guide rail (I-1), and the drill rod (I-6) passes through the holder (I-8) and is slidably engaged with the holder (I-8); The hydraulic cylinder (II-8) is used to drive the guide seat connected to the hydraulic motor (I-3) to move along the guide rail (I-1).

3. A rock strength real-time identification system based on PDC drill bit drilling parameters according to claim 1 or 2, characterized in that: The hydraulic system comprises: A hydraulic pump A (II-2), whose oil inlet is connected to the oil tank, and whose oil outlet is sequentially connected to a three-position four-way manual reversing valve A (II-3), a speed regulating valve (II-4) and the hydraulic motor (I-3); the oil return end of the hydraulic motor (I-3) is connected back to the oil tank through the three-position four-way manual reversing valve A (II-3); The oil inlet of the hydraulic pump B (II-21) is connected to the oil tank, and the oil outlet is connected in sequence to the pressure reducing valve (II-7), the three-position four-way manual reversing valve B (II-31), and the rodless chamber of the hydraulic cylinder (II-8). The rod chamber of the hydraulic cylinder (II-8) is connected back to the oil tank through the two-position three-way manual reversing valve (II-9); The oil inlet pipeline of the hydraulic chuck (I-5) is connected in parallel with the inlet of the pressure reducing valve (II-7), and its clamping or releasing state is controlled by the two-position three-way manual reversing valve (II-9).

4. A rock strength real-time identification system based on PDC drill bit drilling parameters according to claim 3, characterized in that: The data acquisition system includes: A Hall speed sensor (I-2) is installed on the reducer (I-4) and is used to calculate the drill bit speed by detecting the pulse signal of the metal bumps on the surface of the drill rod (I-6); A propulsion oil pressure sensor (II-6) is connected to the oil return line of the rodless cavity of the hydraulic cylinder (II-8) through a three-way joint, and is used to measure the propulsion oil pressure to indirectly calculate the propulsion force; A rotary oil pressure sensor (II-61) is connected to the oil return line of the hydraulic motor (I-3) via a three-way connector and is used to measure the rotary oil pressure to indirectly calculate the torque; A displacement sensor (I-7) is installed between the guide rail (I-1) and the reducer (I-4) and is used to monitor the axial displacement of the drill bit in real time to calculate the drilling speed; a flow sensor (II-5), installed in the circuit of the hydraulic motor (I-3) to measure its flow rate for indirect calculation of torque; An acceleration sensor is installed in the hollow of the drill rod (I-6), fixed by a magnet and connected to a data acquisition card for detecting vibration signals; The host computer receives data from the Hall speed sensor (I-2), propulsion oil pressure sensor (II-6), rotation oil pressure sensor (II-61), displacement sensor (I-7), flow sensor (II-5) and acceleration sensor, performs signal filtering and AD conversion through a data acquisition card, and then calculates the drill bit speed, propulsion force, torque, drilling speed and vibration spectrum characteristics through a data processing module. Finally, the host computer software performs rock strength identification.

5. The rock strength real-time identification system based on PDC drill bit drilling parameters according to claim 3 is characterized in that: The oil outlets of the hydraulic pump A (II-2) and the hydraulic pump B (II-21) are both provided with overflow pipelines connected to the oil tank, and the overflow pipelines are provided with overflow valves (II-1).

6. The rock strength real-time identification system based on PDC drill bit drilling parameters according to claim 4 is characterized in that: The distance between the probe of the Hall speed sensor (I-2) and the metal bumps on the surface of the drill rod (I-6) is 5 mm, and the speed is calculated by counting the high-level pulses triggered by the metal bumps.

7. The rock strength real-time identification system based on PDC drill bit drilling parameters according to claim 4 is characterized in that: The power line and signal line of the acceleration sensor pass through the middle hole of the drill rod (I-6) and are connected to the data acquisition card through the brush.

8. A real-time rock strength identification method based on PDC drill bit drilling parameters, characterized in that: The following steps are involved: S1: The data acquisition system acquires the parameters of the drill bit during the drilling process in real time, including drill bit speed, propulsion oil pressure, rotary oil pressure, drilling speed, vibration signal, and torque. The data acquisition card performs signal filtering and AD conversion, and the data processing module calculates the drill bit speed, propulsion force, torque, drilling speed, and vibration spectrum characteristics. S2: A mechanical model is established based on the rock cutting process of PDC teeth, and the cutting process is divided into two stages: pressing and peeling; S3: Perform mechanical analysis on the compression stage and calculate the rock compressive strength by substituting the real-time collected parameters such as propulsion force and compression area; S4: Perform mechanical analysis on the peeling stage, combine the Mohr-Coulomb criterion, and substitute parameters such as torque and axial acceleration to calculate the rock cohesion and internal friction angle; S5: The calculation results of the compression stage and the rotary cutting stage are integrated to output the rock strength in real time and identify the heterogeneity of the rock layer interface and rock mass.

9. The method for real-time identification of rock strength based on PDC drill bit drilling parameters according to claim 8, characterized in that: The calculation formula of the mechanical model in the pressing stage in step S3 includes: The solution is: F1=k0σ c B0+μF N1 cosα+μF N2 sinα=kσ c B0 Where: k0 is the ratio of the actual indentation area to the theoretical indentation area; k5 is the ratio of the wear area to the indentation area; F N 、F N1 、F N2 is the normal force; F f1 、F f2 is the friction force; μ is the friction coefficient; σ c is the compressive strength of rock; A0 is the wear area; B0 is the intrusion area.

10. The method for real-time identification of rock strength based on PDC drill bit drilling parameters according to claim 8, characterized in that: The mechanical model calculation formula of the peeling stage in step S4 includes: According to the Mohr-Coulomb criterion, the relationship between σ and τ can be obtained: The solution is: Where: M is the mass of the drill string system; a is the axial acceleration; T is the torque; R is the rotation radius of the PDC tooth; c is the cohesive force; is the internal friction angle; Simplifying the formula: Where: k2, k3, k4, k5 are all simplified coefficients.

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