A detection device and method for permafrost
By using a double-layer sealing structure and pressurized gas medium correction technology, the problems of sealing structure failure and inaccurate resonance frequency identification during permafrost coring were solved, thus achieving stable coring of permafrost.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- CHINA ENERGY CONSTR GRP HEILONGJIANG ELECTRIC POWER DESIGN INST CO LTD
- Filing Date
- 2026-05-21
- Publication Date
- 2026-07-31
AI Technical Summary
In the process of core sampling in permafrost regions, existing technologies are prone to failure and pressure loss due to the sealing structure. Under ultrasonic vibration, the resonant frequency under pressure cannot be accurately identified, leading to the destruction of the rock core along the layered fracture surface.
It adopts a double-layer sealing structure and pressurized gas medium correction technology. The inner hard sealing ring bears the pressure, while the outer elastic sealing ring absorbs vibration. The asymmetrical arrangement of the cutting edge group disperses the cutting force. The pressure chamber maintains the in-situ pressure, which coordinates the depressurization and vibration reduction process.
It achieves airtightness assurance under ultrasonic vibration environment, accurately identifies pressurized resonance frequency, reduces the risk of core failure along layered fracture surface, and avoids bubble expansion and stress concentration.
Smart Images
Figure CN122236389B_ABST
Abstract
Description
Technical Field
[0001] This invention relates to the field of permafrost exploration, and more specifically, to a detection device and method for permafrost. Background Technology
[0002] In the shallow aerated permafrost layer of permafrost regions, layered fissures that are nearly parallel to the slope are commonly developed. The spacing between the layered fissures usually varies from 10 to 50 millimeters. The surface of the layered fissures is filled with ice or air, and the gas such as methane trapped in the pores is enriched and distributed along the surface of the layered fissures in the form of bubbles.
[0003] Existing coring technologies for this type of frozen soil mainly employ pressure-balanced air cushion coring and resonance-avoided ultrasonic cutting techniques. Pressure-balanced air cushion coring uses a sealed chamber to maintain pressure to suppress bubble expansion, while resonance-avoided ultrasonic cutting techniques use frequency sweep detection to identify the resonance frequency and adjust the operating frequency to avoid resonance damage.
[0004] However, the existing technology has the following drawbacks: First, conventional single-layer sealing structures are difficult to withstand both static pressure loads and dynamic vibration displacements at the same time. They are prone to failure and pressure relief under ultrasonic vibration environments, which causes the pressure chamber to be unable to maintain its in-situ pressure. The expansion of bubbles causes the rock core to crack and break along the layered fracture surface. Second, frequency sweep detection under normal pressure does not consider the influence of pressurized gas on the propagation characteristics of sound waves. The identified resonant frequency shifts under pressurized conditions, making it impossible to accurately avoid the actual resonance range. This results in resonant vibration causing the ice filling material on the layered fracture surface to shear off or the air fracture to expand and penetrate. Summary of the Invention
[0005] This invention provides a detection device and method for permafrost, solving the technical problems in related technologies such as the easy failure and pressure release of sealing structures under ultrasonic vibration environment, the inability of conventional frequency sweep detection to accurately identify the actual resonance frequency under pressure environment, and the easy destruction and disintegration of gas-bearing layered fracture permafrost cores along the layered fracture surface during the core extraction process.
[0006] This invention provides a detection device for permafrost, comprising a drill rod, a sealed pressure chamber unit, an ultrasonic vibration cutting unit, and a pressure control unit; The upper end of the drill rod is connected to the ground rotating equipment connection end, and an axially extending gas channel is opened inside the rod, which runs through the drill rod. The sealed pressure chamber unit includes a core cylinder wall, a top cap, a bottom sealing lip, and a double-layer sealing structure. The core cylinder wall forms a cavity to accommodate the rock core. The top cap is fixedly installed on the top of the core cylinder wall by a threaded connection. A double-layer sealing structure is set between the top cap and the core cylinder wall. The bottom sealing lip is fixedly installed on the inner side of the bottom end of the core cylinder wall by an annular clamping seat. The bottom sealing lip forms a dynamic sealing contact with the side of the rock core entering the pressure chamber. The upper end of the core tube wall is fixed to the lower end of the drill rod by a threaded connection, forming a transmission path for rotational power and axial load. The lower port of the gas channel extends to the top cap position of the core tube. The double-layer sealing structure includes an inner hard sealing ring and an outer elastic sealing ring. The inner hard sealing ring and the outer elastic sealing ring are arranged in series along the axial direction at the joint between the top cap and the core tube wall. The ultrasonic vibration cutting unit includes an ultrasonic transducer, an amplitude transformer, a drill bit base, and a cutting edge assembly. The ultrasonic transducer is installed on the core cylinder wall through a vibration isolation support structure. The upper end of the amplitude transformer is fixedly connected to the vibration output end of the ultrasonic transducer, and the lower end of the amplitude transformer is fixedly connected to the drill bit base. The cutting edge assembly is fixedly installed on the lower end face of the drill bit base. The pressure control unit includes an inflation and pressure relief valve, a chamber pressure sensor, and a ground controller. The upper port of the gas channel inside the drill pipe is connected to the ground pressure gas source through a rotary joint. The lower port of the gas channel inside the drill pipe extends to the top cap and is connected to the air inlet of the inflation and pressure relief valve. The air outlet of the inflation and pressure relief valve is connected to the pressure chamber. The chamber pressure sensor is installed on the side wall of the top cap. The ground controller receives the pressure signal from the chamber pressure sensor and controls the opening of the inflation and pressure relief valve.
[0007] Preferably, the inner hard sealing ring is a metal annular seal, and the inner hard sealing ring forms a metal-to-metal hard contact with the lower end face of the top cap and the upper end face of the core tube wall; the outer elastic sealing ring is an O-ring made of fluororubber, and the outer elastic sealing ring is installed in an annular groove opened on the outer periphery of the top cap, the depth of the annular groove being less than the wire diameter of the O-ring.
[0008] Preferably, the bottom sealing lip is an integral elastic lip made of polyurethane material, and the edge of the bottom sealing lip is inclined towards the inside of the pressure chamber to form a tapered closing structure facing the inside of the pressure chamber.
[0009] Preferably, the bottom sealing lip is a combined structure, comprising a metal skeleton and an elastic lip. The metal skeleton is annular and fixed to the annular clamping seat by screws, and the elastic lip is fixed to the inner edge of the metal skeleton and extends into the pressure chamber.
[0010] Preferably, the cutting edge assembly includes three cutting edges, with angular intervals of 100 degrees, 120 degrees, and 140 degrees along the circumferential direction, respectively, and the installation height difference of each cutting edge along the axial direction is between 0.1 mm and 0.5 mm.
[0011] Preferably, it also includes an acoustic wave detection unit, which includes an acoustic wave emitting probe, an acoustic wave receiving probe, and a signal processing module. The acoustic wave emitting probe and the acoustic wave receiving probe are installed on the lower outer circumferential surface of the core cylinder wall through a fixed bracket. The signal processing module receives the reflected wave electrical signal output by the acoustic wave receiving probe, analyzes the reflected wave spectrum characteristics to identify the resonance frequency range, and corrects the resonance frequency range according to the pressure signal of the chamber pressure sensor.
[0012] Preferably, the signal processing module has a built-in pressurized gas medium correction data table, which records the sound wave propagation speed correction coefficients corresponding to different pressure values. The signal processing module obtains the correction coefficients by looking up the table based on the real-time pressure value fed back by the chamber pressure sensor.
[0013] Preferably, a temperature sensor is also provided on the inner side of the core cylinder wall, and the pressurized gas medium correction data table is a two-dimensional pressure-temperature table. The signal processing module looks up the correction coefficient in the table based on the combination of pressure and temperature values.
[0014] Preferably, it also includes a vibration monitoring unit, which includes a vibration sensor and a vibration control module. The vibration sensor is fixedly installed at the middle node position of the amplitude transformer. The vibration control module receives the vibration signal output by the vibration sensor. When an abnormal increase in vibration amplitude is detected, the drive power frequency of the ultrasonic transducer is adjusted to switch to a preset alternative safe frequency.
[0015] This invention also proposes a method for detecting permafrost, which involves using the aforementioned permafrost detection device and includes the following steps: S1: Start the ground rotating equipment to drive the drill rod to rotate, and at the same time start the ultrasonic transducer to work at the set safe frequency and amplitude; S2: Under the combined action of rotational motion and axial vibration, the cutting edge group of the drill bit body cuts into the frozen soil layer; S3: The rock core produced by cutting gradually enters the pressure chamber during the drilling process. The bottom sealing lip forms a dynamic seal with the side of the rock core, and the gas pressure inside the pressure chamber exerts pressure constraint on the surface of the rock core. S4: The vibration sensor collects the vibration signal of the drill bit base in real time, and the vibration control module monitors the trend of vibration amplitude change.
[0016] If the vibration control module detects an abnormally increasing trend in the vibration amplitude and determines that the current frequency is close to the actual resonance frequency of the rock core, the vibration control module will switch the working frequency of the ultrasonic transducer to the alternative safe frequency by adjusting the drive power frequency of the ultrasonic transducer, and continue drilling operations. S5: After the core is fully inside the pressure chamber, drilling stops. The pressurized gas inside the pressure chamber continues to exert pressure on the surface of the core to maintain the stability of the bubbles inside the core.
[0017] S6: During the process of lifting the drill pipe to retrieve the core, the air pressure relief valve releases the pressure in the pressure chamber in stages. The release process is divided into multiple stages. After releasing part of the pressure in each stage, it is paused and the next stage is entered after the internal stress of the core is redistributed, until the core is completely retrieved.
[0018] The beneficial effects of this invention are as follows: This invention separates the pressure-bearing and vibration-absorbing functions through a double-layer sealing structure. The inner hard sealing ring bears the pressure load, while the outer elastic sealing ring absorbs vibration displacement, solving the technical problem of easy failure and pressure leakage of the sealing structure under ultrasonic vibration environment, and ensuring the airtightness of the pressure chamber under vibration environment. The pressurized gas medium correction compensates for the influence of pressurized gas on the sound wave propagation speed, solving the technical problem of the resonance frequency identified by normal pressure sweep frequency detection shifting under pressurized environment, and achieving accurate avoidance of the ultrasonic transducer operating frequency from the actual resonance frequency range under pressurized environment. The asymmetrical arrangement of the cutting edge group disperses the cutting force in the spatial and temporal dimensions, reducing the risk of inducing resonance of the layered fracture surface. By maintaining a gas pressure constraint that matches the in-situ formation pressure in the pressure chamber, the expansion of bubbles distributed along the layered fracture surface inside the rock core is suppressed, avoiding the disintegration of the rock core along the layered fracture surface caused by the expansion of bubbles and the cracking of the ice matrix. The phased lifting process of coordinated pressure release and vibration reduction avoids stress concentration caused by rapid unloading, reducing the risk of rock core damage along the layered fracture surface during lifting. Attached Figure Description
[0019] Figure 1 This is a half-sectional structural diagram of a permafrost detection device according to the present invention. Figure 2 This is the invention Figure 1 The main view; Figure 3 This is the invention Figure 2 A magnified view of part A in the middle; Figure 4 This is the invention Figure 2 A magnified view of part B in the middle; Figure 5 This is a schematic diagram of the molding structure of the pressure chamber of the present invention; Figure 6 This is a schematic diagram of the integral bottom sealing lip of the present invention; Figure 7 This is a schematic diagram of the combined bottom sealing lip structure of the present invention; Figure 8 This is a schematic diagram of the end face structure of the drill bit base of the present invention.
[0020] In the diagram: 100, drill pipe; 110, rod body; 120, chuck; 130, gas passage; 140, inflation and pressure relief valve; 200, sealed pressure chamber unit; 210, core tube wall; 220, top cap; 230, bottom sealing lip; 231, metal frame; 232, elastic lip; 233, annular clamping seat; 240, inner hard sealing ring; 250, outer elastic sealing ring; 260, ultrasonic transducer; 261, transducer housing; 262, piezoelectric ceramic stack; 263, vibration output end; 264, amplitude transformer; 300, ultrasonic vibration cutting unit; 310, drill bit base; 320, cutting edge assembly; 400, ground rotating equipment connection end; 500, acoustic detection unit. Detailed Implementation
[0021] The subject matter described herein will now be discussed with reference to exemplary embodiments. It should be understood that these embodiments are discussed only to enable those skilled in the art to better understand and implement the subject matter described herein, and changes may be made to the function and arrangement of the discussed elements without departing from the scope of this specification. Various processes or components may be omitted, substituted, or added as needed in the examples. Furthermore, features described in some examples may be combined in other examples.
[0022] like Figures 1-8 As shown in the embodiment, a permafrost detection device for pressure balance and resonance avoidance in gas-bearing layered fractured permafrost is proposed, comprising at least a sealed pressure chamber unit 200, an ultrasonic vibration cutting unit 300, and a pressure control unit. The sealed pressure chamber unit 200 provides a closed space to maintain in-situ pressure, the ultrasonic vibration cutting unit 300 provides vibration energy for cutting the permafrost and avoids resonance frequencies, and the pressure control unit adjusts the internal pressure of the sealed pressure chamber unit 200 to match the formation pressure corresponding to the sampling depth.
[0023] The drill pipe 100 serves as the system reference for the entire device. The upper end of the drill pipe 100's body 110 is rotatably connected to the ground rotating equipment connection end 400 via a chuck 120, receiving rotational power and axial load. An axially extending gas channel 130 is formed inside the body 110, running the entire length of the drill pipe 100. The upper end of the gas channel 130 is connected to a ground pressure gas source, and the lower end extends to the top cap 220 of the core sampler. The upper end of the core sampler wall 210 is threadedly connected to the lower end of the drill pipe 100, forming a path for transmitting rotational power and axial load.
[0024] The sealed pressure chamber unit 200 includes a core tube wall 210, a top cap 220, a bottom sealing lip 230, and a double-layer sealing structure. The above components enclose the pressure chamber.
[0025] The core sampling cylinder wall 210 has a cylindrical structure, and a cavity is formed inside the core sampling cylinder wall 210 to accommodate the rock core. The core sampling cylinder wall 210 bears the radial load generated by the air pressure inside the pressure chamber. The top cap 220 is fixedly installed on the top of the core sampling cylinder wall 210 by a threaded connection, and a double-layer sealing structure is set between the top cap 220 and the core sampling cylinder wall 210. The bottom sealing lip 230 is fixedly installed on the inner side of the bottom end of the core sampling cylinder wall 210 by an annular clamping seat 233, and the annular clamping seat 233 is fixed to the core sampling cylinder wall 210 by screws. The bottom sealing lip 230 forms a dynamic sealing contact with the side of the rock core entering the pressure chamber. The pressure chamber is a closed space enclosed by the inner wall surface of the core sampling cylinder wall 210, the lower end surface of the top cap 220, and the inner edge surface of the bottom sealing lip 230.
[0026] The double-layer sealing structure includes an inner hard sealing ring 240 and an outer elastic sealing ring 250, which are arranged axially in series at the joint between the top cap 220 and the core tube wall 210. The inner hard sealing ring 240 is located inside the joint, directly facing the pressure chamber, and bears the pressure load generated by the internal air pressure. The outer elastic sealing ring 250 is located outside the inner hard sealing ring 240, facing the external environment, and undergoes elastic deformation during ultrasonic vibration to absorb vibration displacement. The inner hard sealing ring 240 and the outer elastic sealing ring 250 are functionally separate; the inner hard sealing ring 240 is dedicated to pressure sealing, while the outer elastic sealing ring 250 is dedicated to absorbing minute relative displacements caused by vibration. The inner hard sealing ring 240 and the outer elastic sealing ring 250 work together to ensure the airtightness of the pressure chamber under vibration conditions.
[0027] In some embodiments, the inner hard sealing ring 240 is a metal annular seal. The inner hard sealing ring 240 forms a metal-to-metal hard contact with the lower end face of the top cap 220 and the upper end face of the core tube wall 210, and achieves airtightness through the precision machining of the metal surfaces.
[0028] In some embodiments, the outer elastic sealing ring 250 is an O-ring made of fluororubber. The outer elastic sealing ring 250 is installed in an annular groove opened on the outer periphery of the top cover 220. The depth of the annular groove is less than the wire diameter of the O-ring, so that the O-ring undergoes pre-compression deformation in the installed state. The elastic margin provided by the pre-compression deformation is used to compensate for the axial displacement generated by ultrasonic vibration.
[0029] Furthermore, in order to adapt to the low-temperature permafrost environment, the outer elastic sealing ring 250 is made of low-temperature fluororubber or silicone rubber. The glass transition temperature of the outer elastic sealing ring 250 is lower than the temperature of the core sampling operation environment, ensuring that the outer elastic sealing ring 250 still has elastic deformation ability at low temperatures.
[0030] The bottom sealing lip 230 forms a dynamic seal with the side of the core entering the pressure chamber. During the process of the core moving upward relative to the core tube into the pressure chamber, the lip edge of the bottom sealing lip 230 remains in contact with the side of the core and allows relative sliding, while preventing the gas inside the pressure chamber from leaking downward.
[0031] like Figure 6 As shown, in some embodiments, the bottom sealing lip 230 is an integral elastic lip. The bottom sealing lip 230 is made of polyurethane material and has an elastic lip edge 232. The elastic lip edge 232 of the bottom sealing lip 230 is inclined towards the inside of the pressure chamber, forming a tapered constriction structure facing the inside of the pressure chamber. The air pressure inside the pressure chamber acts on the back of the elastic lip edge 232 of the bottom sealing lip 230, causing the elastic lip edge 232 of the bottom sealing lip 230 to press against the side of the rock core. The higher the pressure, the tighter the seal.
[0032] like Figure 7 As shown, in some embodiments, the bottom sealing lip 230 is a composite structure, comprising a metal skeleton 231 and an elastic lip 232. The metal skeleton 231 is annular and fixed to the annular clamping seat 233 by screws; the elastic lip 232 is fixed to the inner edge of the metal skeleton 231, extends into the pressure chamber and contacts the side of the rock core. The metal skeleton 231 provides structural support, and the elastic lip 232 provides sealing contact; the composite structure balances structural strength and sealing performance.
[0033] The ultrasonic vibration cutting unit 300 includes an ultrasonic transducer 260, an amplitude transformer 264, a drill bit base 310, and a cutting edge assembly 320, which is used to convert electrical energy into mechanical vibration and transmit it to the cutting edge assembly 320 to achieve vibration cutting.
[0034] The ultrasonic transducer 260 includes a transducer housing 261, a piezoelectric ceramic stack 262, and a vibration isolation support structure. The transducer housing 261 is mounted to the core barrel wall 210 via the vibration isolation support structure, which includes an annular vibration isolation pad and a fixing clamp. The annular vibration isolation pad is located between the transducer housing 261 and the fixing clamp, which is connected to the core barrel wall 210 by screws. The annular vibration isolation pad reduces the energy transmitted from the transducer housing 261's vibration to the core barrel wall 210. The piezoelectric ceramic stack 262 is installed inside the transducer housing 261 and receives alternating electrical signals via a cable, converting electrical energy into axial high-frequency mechanical vibration. The transducer housing 261 also includes a vibration output end 263, which performs high-frequency reciprocating motion relative to the transducer housing 261 along the axial direction, outputting vibration energy.
[0035] The upper end of the amplitude transformer 264 is fixedly connected to the vibration output end 263 of the ultrasonic transducer 260, and the lower end of the amplitude transformer 264 is fixedly connected to the drill bit base 310. The amplitude transformer 264 is used to amplify the vibration amplitude output by the vibration output end 263 of the ultrasonic transducer 260 and transmit the amplified vibration to the drill bit base 310.
[0036] In some embodiments, the amplitude transformer 264 is fixed to the vibration output end 263 of the ultrasonic transducer 260 by a threaded connection, and the threaded connection surface is pre-tightened to withstand high-frequency alternating loads.
[0037] In some embodiments, the amplitude transformer 264 and the drill bit base 310 are connected by a tapered interference fit. The friction provided by the interference fit transmits torque while ensuring the continuity of vibration transmission.
[0038] The drill bit body 310 is fixedly connected to the end of the luffing head 264 and vibrates together with the luffing head 264, while also bearing the rotational torque transmitted by the drill rod 100. The lower end face of the drill bit body 310 is the cutting working surface, and the cutting edge assembly 320 is fixedly installed on the lower end face of the drill bit body 310.
[0039] The cutting edge assembly 320 includes multiple cutting edges, each of which is fixed to the lower end face of the drill bit base 310 by brazing or mechanical chucks and is distributed along the circumferential direction. The cutting edge assembly 320 adopts an asymmetrical arrangement, with the circumferential position and axial height of each cutting edge being different, so that the vibration phases of each cutting edge are staggered during the vibration process.
[0040] like Figure 8 As shown, in some embodiments, the cutting edge group 320 includes three cutting edges, which are spaced at 100 degrees, 120 degrees, and 140 degrees angularly along the circumferential direction, forming an asymmetrical arrangement with uneven angular distribution. The uneven distribution of each cutting edge in the circumferential direction makes the periodic excitation acting on the rock core during the cutting process non-uniform, avoiding the formation of regular periodic excitation on the layered fracture surface.
[0041] In some embodiments, the installation height of each cutting edge varies along the axial direction, with the height difference ranging from 0.1 mm to 0.5 mm. This height difference causes the contact time between each cutting edge and the frozen soil to be asynchronous, further disrupting the concentrated distribution of vibration energy over time.
[0042] Furthermore, in order to reduce the impact of the vibration amplitude of a single cutting edge on the layered fracture surface, the axial height difference and circumferential angle difference of each cutting edge are combined to form a spiral progressive layout, so that the cutting force is evenly distributed in the spatial and temporal dimensions.
[0043] The pressure control unit includes a gas passage 130 inside the drill pipe 100, an inflation and depressurization valve 140, a chamber pressure sensor, and a ground controller, which are used to control the gas pressure inside the pressure chamber.
[0044] The gas passage 130 inside the drill pipe 100 is an axial channel formed inside the drill pipe 100. The upper port of the gas passage 130 is connected to the ground pressure gas source through a rotary joint, and the lower port of the gas passage 130 extends to the top cap 220 and is connected to the air inlet of the inflation and depressurization valve 140. High-pressure gas provided by the ground pressure gas source is delivered to the pressure chamber through the gas passage 130 inside the drill pipe 100.
[0045] The inflation / pressure relief valve 140 is threadedly installed on the top cover 220. The air inlet of the inflation / pressure relief valve 140 is connected to the lower port of the gas passage 130 inside the drill pipe 100 via a high-pressure hose, and the air outlet of the inflation / pressure relief valve 140 is connected to the pressure chamber. The inflation / pressure relief valve 140 controls the rate at which gas enters the pressure chamber and the rate at which gas is released from the pressure chamber.
[0046] In some embodiments, the inflation and depressurization valve 140 is an electromagnetic proportional valve, which adjusts the valve opening by controlling the current to achieve continuous adjustment of the inflation rate and depressurization rate.
[0047] In some embodiments, the inflation and pressure relief valve 140 includes two independent valve bodies: an inflation valve and a pressure relief valve. The inflation valve controls the gas to enter the pressure chamber, and the pressure relief valve controls the gas to be released from the pressure chamber. The inflation valve and the pressure relief valve are controlled separately to achieve independent regulation of the inflation and pressure relief processes.
[0048] The chamber pressure sensor is installed on the side wall of the top cover 220 via a threaded connection, with the sensing surface of the chamber facing the inside of the pressure chamber, for real-time monitoring of the gas pressure inside the pressure chamber. The pressure signal from the chamber pressure sensor is transmitted to the ground controller via a cable.
[0049] The ground controller receives the pressure signal from the chamber pressure sensor and controls the opening of the inflation and depressurization valve 140 according to the preset target pressure value to achieve automatic adjustment of the pressure chamber pressure.
[0050] In order to identify the resonant frequency range of the permafrost layer before drilling, the detection device for pressure balance and resonance avoidance of permafrost containing air-layered fractured permafrost also includes an acoustic detection unit 500.
[0051] The acoustic wave detection unit 500 includes an acoustic wave emitting probe, an acoustic wave receiving probe, and a signal processing module. The acoustic wave emitting probe and the acoustic wave receiving probe are mounted on the lower outer circumferential surface of the core sampling cylinder wall 210 via a fixed bracket. The fixed bracket is connected to the core sampling cylinder wall 210 by screws, and the working surfaces of the acoustic wave emitting probe and the acoustic wave receiving probe face the frozen soil layer to be sampled.
[0052] The acoustic wave transmitting probe emits a swept-frequency acoustic signal into the frozen soil layer to be sampled, with the swept frequency range covering the possible resonant frequency range of the frozen soil's layered cracks. The acoustic wave receiving probe receives the reflected wave signal from the frozen soil layer and converts the reflected wave signal into an electrical signal for output.
[0053] The signal processing module receives the reflected wave electrical signal output by the acoustic wave receiving probe, analyzes the reflected wave spectrum characteristics, and identifies the frequency range that causes the peak amplitude response as the resonant frequency range. The signal processing module also receives the pressure signal from the chamber pressure sensor and corrects the identified resonant frequency range based on the influence of the gas pressure inside the pressure chamber on the sound wave propagation speed.
[0054] In some embodiments, the signal processing module incorporates a pressurized gas medium correction data table, which records the sound wave propagation velocity correction coefficients corresponding to different pressure values. The signal processing module retrieves the correction coefficients from the table based on the real-time pressure values fed back by the chamber pressure sensor, and multiplies the resonant frequency range identified under normal pressure by the correction coefficients to obtain the calibrated resonant frequency range under pressurized conditions.
[0055] Furthermore, to improve the correction accuracy, a temperature sensor is also installed on the inner side of the core barrel wall 210. The temperature sensor is fixed to the inner wall of the core barrel wall 210 by a clamp. The signal processing module also receives the temperature signal from the temperature sensor. The pressurized gas medium correction data table is a two-dimensional pressure-temperature table. The correction coefficient is obtained by looking up the table based on the combination of pressure and temperature values.
[0056] Furthermore, in order to monitor the vibration status in real time and make dynamic adjustments during the drilling process, the detection device for pressure balance and resonance avoidance of permafrost containing gas-bearing layered fractured permafrost also includes a vibration monitoring unit.
[0057] The vibration monitoring unit includes a vibration sensor and a vibration control module. The vibration sensor is fixedly installed at the middle node of the amplitude transformer 264 with screws, and moves with the vibrating component to collect vibration amplitude and frequency signals in real time.
[0058] The vibration control module receives vibration signals output by the vibration sensor and analyzes the trend of vibration amplitude changes. When the vibration control module detects an abnormal increase in vibration amplitude, it determines that the current operating frequency is close to the actual resonance frequency of the layered fractures in the rock core. The vibration control module then adjusts the drive power frequency of the ultrasonic transducer 260 to switch the operating frequency of the ultrasonic transducer 260 to a preset alternative safe frequency.
[0059] In some embodiments, the vibration control module stores multiple alternative safety frequencies, each of which is outside the calibration resonant frequency range and maintains a frequency interval between them. When the preferred safety frequency fails, the vibration control module switches to the next alternative safety frequency in sequence.
[0060] Based on the aforementioned permafrost detection device, the following detection process is implemented. Specifically, the permafrost detection method includes the following steps: Step 1: Resonance Frequency Detection Before drilling begins, the acoustic wave transmitting probe emits a swept-frequency acoustic signal into the frozen soil layer to be sampled, and the acoustic wave receiving probe receives the reflected signal. The signal processing module analyzes the reflected spectrum, identifies the frequency range that causes the peak amplitude response, and determines the resonant frequency range under normal pressure.
[0061] In some embodiments, the frequency range of the swept acoustic signal is from 10 kHz to 50 kHz, covering the typical resonant frequency range of layered fractured permafrost.
[0062] Step 2: Pre-pressurize the chamber The in-situ formation pressure value corresponding to the sampling target depth is calculated to determine the target pressure of the pressure chamber. The ground controller controls the ground pressure gas source to inject pressurized gas into the pressure chamber through the gas channel 130 inside the drill pipe 100. The inflation and depressurization valve 140 controls the inflation rate, and the chamber pressure sensor monitors the pressure of the pressure chamber in real time. When the pressure of the pressure chamber reaches the target pressure value, the ground controller controls the inflation and depressurization valve 140 to close, completing the pre-pressurization of the pressure chamber.
[0063] In some embodiments, the inflation process is divided into multiple stages. After each stage, a portion of the pressure is introduced and then paused until the pressure in the pressure chamber stabilizes before proceeding to the next stage, in order to avoid temperature fluctuations caused by rapid inflation affecting the sealing performance.
[0064] Step 3: Resonance Frequency Correction The signal processing module queries the pressurized gas medium correction data table based on the actual pressure value after the pressure chamber is pre-pressurized to obtain the sound wave propagation velocity correction coefficient. The normal pressure resonant frequency range identified in step one is multiplied by the correction coefficient to obtain the calibrated resonant frequency range under pressurized conditions.
[0065] Step 4: Vibration Parameter Setting Based on the calibrated resonance frequency range, the operating frequency of the ultrasonic transducer 260 is set. The operating frequency of the ultrasonic transducer 260 is selected as a safe frequency outside the calibrated resonance frequency range. At the same time, an upper limit value for the vibration amplitude is set, which does not exceed the allowable elastic deformation range of the outer elastic sealing ring 250.
[0066] In some embodiments, the interval between the safety frequency and the boundary of the calibration resonant frequency range is not less than two kilohertz to provide a safety margin for frequency drift.
[0067] Step 5: Vibratory cutting drilling The ground rotation equipment is activated to drive the drill rod 100 to rotate, and simultaneously the ultrasonic transducer 260 is activated to operate at the set safe frequency and amplitude. Under the combined action of rotational motion and axial vibration, the cutting edge assembly 320 of the drill bit body 310 cuts into the permafrost layer. The rock core produced by cutting gradually enters the pressure chamber during drilling. The bottom sealing lip 230 forms a dynamic seal with the side of the rock core, and the gas pressure inside the pressure chamber exerts pressure constraint on the surface of the rock core.
[0068] The vibration sensor collects the vibration signal of the drill bit base 310 in real time, and the vibration control module monitors the trend of vibration amplitude change.
[0069] Step Six: Abnormal Vibration Response If the vibration control module detects an abnormally increasing trend in the vibration amplitude and determines that the current frequency is close to the actual resonance frequency of the rock core, the vibration control module will switch the operating frequency of the ultrasonic transducer 260 to the alternative safe frequency by adjusting the drive power frequency of the ultrasonic transducer 260, and continue drilling operations.
[0070] Step 7: Core sealing and pressure maintenance Once the core sample is fully inside the pressure chamber, drilling stops. The pressurized gas inside the pressure chamber continuously applies pressure to the surface of the core sample, maintaining the stability of the air bubbles inside.
[0071] Step 8: Collaborative Enhancement During the process of retrieving the core sample from the drill pipe 100, the ground controller controls the inflation and pressure relief valve 140 to release the pressure in the pressure chamber in stages. The release process is divided into multiple stages, with each stage pausing after releasing a portion of the pressure to allow the internal stress of the core sample to redistribute before proceeding to the next stage. The vibration control module synchronously controls the ultrasonic transducer 260 to gradually reduce the vibration amplitude, with the decay rhythm of the vibration amplitude matching the pressure release rhythm, until the vibration finally stops.
[0072] In some embodiments, the decompression process is divided into three to five stages, each stage releasing 20% to 33% of the target pressure in the pressure chamber, with an interval of 10 to 30 seconds between stages.
[0073] This embodiment separates the pressure-bearing and vibration-absorbing functions through a double-layer sealing structure. The inner hard sealing ring 240 bears the gas pressure load inside the pressure chamber through metal-to-metal hard contact, while the outer elastic sealing ring 250 absorbs the axial displacement generated by ultrasonic vibration through elastic deformation. Therefore, it solves the technical problem of easy failure and pressure leakage of the sealing structure under ultrasonic vibration environment. The functional separation of the double-layer sealing structure means that the inner hard sealing ring 240 does not need to take into account elastic deformation, and can focus on ensuring the sealing surface accuracy and contact pressure; the outer elastic sealing ring 250 does not need to bear the main pressure load, and can focus on providing sufficient elastic deformation margin.
[0074] This embodiment uses pressurized gas medium correction to make the resonance frequency identification results obtained by acoustic wave detection applicable to pressurized pressure chamber conditions. The signal processing module corrects the resonance frequency range identified under normal pressure conditions based on the actual pressure value of the pressure chamber, compensating for the influence of pressurized gas medium on the sound wave propagation speed. Therefore, the operating frequency of the ultrasonic transducer 260 can accurately avoid the actual resonance frequency range of the core layered fractures under pressurized conditions, preventing resonance vibration from causing the ice filling material on the layered fracture surface to shear off or the air fractures to expand and penetrate.
[0075] This embodiment uses an asymmetrical arrangement of the cutting edge group 320 to stagger the vibration phases of each cutting edge. The positional differences of each cutting edge in the circumferential and axial directions result in asynchronous contact times and positions between each cutting edge and the frozen soil. The cutting force is distributed in a dispersed manner in both spatial and temporal dimensions, thus avoiding the formation of regular periodic excitation on the layered fracture surface of the rock core and reducing the risk of inducing resonance in the layered fracture surface.
[0076] This embodiment applies continuous gas pressure constraint to the surface of the core entering the pressure chamber. The gas pressure constraint matches the in-situ formation pressure of the core, thus suppressing the expansion of bubbles distributed along the layered fracture surface inside the core and preventing the core from disintegrating along the layered fracture surface due to the expansion and cracking of the ice matrix.
[0077] This implementation method uses a coordinated decompression and vibration attenuation lifting process to divide the pressure release and vibration decay into multiple stages and carry them out simultaneously. Each stage releases part of the pressure and reduces part of the vibration amplitude, with a stress redistribution interval between stages. Therefore, it avoids stress concentration caused by rapid unloading and reduces the risk of core damage along the layered fracture surface during the lifting process.
[0078] The embodiments of the present invention have been described above. However, the embodiments are not limited to the specific implementation methods described above. The specific implementation methods described above are merely illustrative and not restrictive. Those skilled in the art can make more equivalent embodiments under the guidance of the present embodiments, and all of them are within the protection scope of the present embodiments.
[0079] The embodiments of the present invention have been described above, but the present invention is not limited to the specific embodiments described above. The specific embodiments described above are merely illustrative and not restrictive. Those skilled in the art can make many other forms under the guidance of the present invention, all of which are within the protection scope of the present invention.
Claims
1. A device for detecting permafrost, characterized in that, Includes drill pipe, sealed pressure chamber unit, ultrasonic vibration cutting unit, and pressure control unit; The upper end of the drill rod is connected to the ground rotating equipment connection end, and an axially extending gas channel is opened inside the rod, which runs through the drill rod. The sealed pressure chamber unit includes a core cylinder wall, a top cap, a bottom sealing lip, and a double-layer sealing structure. The core cylinder wall forms a cavity to accommodate the rock core. The top cap is fixedly installed on the top of the core cylinder wall by a threaded connection. A double-layer sealing structure is set between the top cap and the core cylinder wall. The bottom sealing lip is fixedly installed on the inner side of the bottom end of the core cylinder wall by an annular clamping seat. The bottom sealing lip forms a dynamic sealing contact with the side of the rock core entering the pressure chamber. The upper end of the core tube wall is fixed to the lower end of the drill rod by a threaded connection, forming a transmission path for rotational power and axial load. The lower port of the gas channel extends to the top cap position of the core tube. The double-layer sealing structure includes an inner hard sealing ring and an outer elastic sealing ring. The inner hard sealing ring and the outer elastic sealing ring are arranged in series along the axial direction at the joint between the top cap and the core tube wall. The ultrasonic vibration cutting unit includes an ultrasonic transducer, an amplitude transformer, a drill bit base, and a cutting edge assembly. The ultrasonic transducer is installed on the core cylinder wall through a vibration isolation support structure. The upper end of the amplitude transformer is fixedly connected to the vibration output end of the ultrasonic transducer, and the lower end of the amplitude transformer is fixedly connected to the drill bit base. The cutting edge assembly is fixedly installed on the lower end face of the drill bit base. The pressure control unit includes an inflation and pressure relief valve, a chamber pressure sensor, and a ground controller. The upper port of the gas channel inside the drill pipe is connected to the ground pressure gas source through a rotary joint. The lower port of the gas channel inside the drill pipe extends to the top cap and is connected to the air inlet of the inflation and pressure relief valve. The air outlet of the inflation and pressure relief valve is connected to the pressure chamber. The chamber pressure sensor is installed on the side wall of the top cap. The ground controller receives the pressure signal from the chamber pressure sensor and controls the opening of the inflation and pressure relief valve.
2. A device for detecting permafrost according to claim 1, characterized in that The inner hard sealing ring is a metal annular seal, and the inner hard sealing ring forms a metal-to-metal hard contact with the lower end face of the top cap and the upper end face of the core tube wall; the outer elastic sealing ring is an O-ring made of fluororubber, and the outer elastic sealing ring is installed in the annular groove opened on the outer periphery of the top cap, and the depth of the annular groove is less than the wire diameter of the O-ring.
3. The apparatus of claim 1, wherein the apparatus is configured to be placed in permafrost. The bottom sealing lip is an integral elastic lip made of polyurethane material. The edge of the bottom sealing lip is inclined towards the inside of the pressure chamber, forming a tapered constriction structure facing the inside of the pressure chamber.
4. A permafrost detection device according to claim 1, characterized in that, The bottom sealing lip is a composite structure, consisting of a metal skeleton and an elastic lip. The metal skeleton is annular and fixed to the annular pressure seat with screws. The elastic lip is fixed to the inner edge of the metal skeleton and extends into the pressure chamber.
5. The apparatus of claim 1, wherein The cutting edge assembly includes three cutting edges, with circumferential angular intervals of 100 degrees, 120 degrees, and 140 degrees, respectively. The installation height difference of each cutting edge along the axial direction is between 0.1 mm and 0.5 mm.
6. The apparatus of claim 1, wherein, It also includes an acoustic wave detection unit, which includes an acoustic wave emitting probe, an acoustic wave receiving probe, and a signal processing module. The acoustic wave emitting probe and the acoustic wave receiving probe are installed on the lower outer circumferential surface of the core cylinder wall through a fixed bracket. The signal processing module receives the reflected wave electrical signal output by the acoustic wave receiving probe, analyzes the reflected wave spectrum characteristics to identify the resonance frequency range, and corrects the resonance frequency range according to the pressure signal of the chamber pressure sensor.
7. A device for detecting permafrost according to claim 6, characterised in that The signal processing module has a built-in pressurized gas medium correction data table, which records the sound wave propagation speed correction coefficients corresponding to different pressure values. The signal processing module looks up the correction coefficients in the table based on the real-time pressure value fed back by the chamber pressure sensor.
8. A permafrost detection device according to claim 7, characterized in that, A temperature sensor is also installed on the inner side of the core cylinder wall. The pressurized gas medium correction data table is a two-dimensional pressure-temperature table. The signal processing module looks up the correction coefficient based on the combination of pressure and temperature values.
9. The apparatus of claim 1, wherein, It also includes a vibration monitoring unit, which includes a vibration sensor and a vibration control module. The vibration sensor is fixedly installed at the middle node position of the amplitude transformer. The vibration control module receives the vibration signal output by the vibration sensor. When an abnormal increase in vibration amplitude is detected, the drive power frequency of the ultrasonic transducer is adjusted to switch to a preset alternative safe frequency.
10. A method of detecting permafrost, characterized by, The detection of permafrost using a detection device as described in any one of claims 1-9 includes the following steps: S1: Start the ground rotating equipment to drive the drill rod to rotate, and at the same time start the ultrasonic transducer to work at the set safe frequency and amplitude; S2: Under the combined action of rotational motion and axial vibration, the cutting edge group of the drill bit body cuts into the frozen soil layer; S3: The rock core produced by cutting gradually enters the pressure chamber during the drilling process. The bottom sealing lip forms a dynamic seal with the side of the rock core, and the gas pressure inside the pressure chamber exerts pressure constraint on the surface of the rock core. S4: The vibration sensor collects the vibration signal of the drill bit base in real time, and the vibration control module monitors the trend of vibration amplitude change. If the vibration control module detects an abnormally increasing trend in the vibration amplitude and determines that the current frequency is close to the actual resonance frequency of the rock core, the vibration control module will switch the working frequency of the ultrasonic transducer to the alternative safe frequency by adjusting the drive power frequency of the ultrasonic transducer, and continue drilling operations. S5: After the core is completely inside the pressure chamber, drilling stops. The pressurized gas inside the pressure chamber continues to exert pressure on the surface of the core to maintain the stability of the bubbles inside the core. S6: During the process of lifting the drill pipe to retrieve the core, the air pressure relief valve releases the pressure in the pressure chamber in stages. The release process is divided into multiple stages. After releasing part of the pressure in each stage, it is paused and the next stage is entered after the internal stress of the core is redistributed, until the core is completely retrieved.