A drilling apparatus and method for undisturbed soil cold sampling

Abstract

The application discloses a drilling device and a drilling method for frozen sampling of undisturbed soil, and relates to the technical field of drilling equipment. In the application, the diameter of the drilling unit can be telescopic adjusted through the variable-diameter adjusting unit. In the initial drilling stage, the diameter of the drilling unit can be first increased through the variable-diameter adjusting unit, so that a channel hole with a larger diameter can be drilled. After drilling reaches the sampling depth, the diameter of the drilling unit can be reduced through the variable-diameter adjusting unit, so that a sampling hole with a smaller diameter can be drilled through the drilling unit. Therefore, the subsequent sampling tool and the sample soil column can be conveniently and barrier-free taken out, and it is not necessary to replace the drill bit with different diameters during the drilling process, so that the drilling process is more convenient and fast. The wall protection unit is arranged in the drill bit part. When the drilling unit rotates and moves downward, the wall protection unit can compact and smooth the inner wall of the hole drilled by the drilling unit, so that the stability of the inner wall of the hole is improved, and the collapse and deformation of the hole wall are prevented.

Description

Technical Field

[0001] This invention belongs to the field of drilling equipment technology, and more specifically, relates to a drilling device and a drilling method for undisturbed soil freezing sampling. Background Technology

[0002] In geotechnical engineering investigation, obtaining deep, undisturbed soil samples is crucial for analyzing the physical and mechanical properties of soil layers. For soft soil layers, sensitive clay or sandy soil layers, conventional mechanical drilling can easily disturb the soil mass. Therefore, the freezing sampling method is often used, which utilizes the freezing force between the frozen soil and the surrounding strata to extract the soil sample intact.

[0003] The commonly used method for cryogenic sampling is direct liquid nitrogen injection. The specific operation is as follows: First, a drilling rig is used to drill to the target depth (e.g., 10m), forming a borehole with a diameter of about 110-130mm; then, the drill rod is raised, and a freezing tube with a closed bottom is lowered to the bottom of the hole; liquid nitrogen (boiling point -196℃) is injected into the freezing tube through the pipeline. The liquid nitrogen vaporizes inside the tube, and the cold energy is conducted through the metal tube wall, causing the soil around the tube wall to gradually freeze, eventually forming a frozen ring-shaped soil column, which is frozen together with the freezing tube; finally, the drill rod is raised, and the ring-shaped soil sample is taken out. To extract the ring-shaped soil column without obstruction, a large-diameter drill bit is first used to drill a large-diameter channel hole. When drilling reaches the sampling depth, the drill rod and drill bit need to be lifted, and a smaller-diameter drill bit needs to be used to drill a sampling hole that fits the outer diameter of the freezing pipe. Because the drill bit needs to be changed during the drilling process, the drilling process is quite cumbersome and greatly reduces drilling efficiency. On the other hand, when drilling in soft soil layers, sensitive clay or sandy soil layers, the soft soil layer makes the drilled hole wall prone to collapse and deformation. This not only easily affects the integrity of the soil column but may also hinder the movement and transportation of the freezing pipe and soil column, making it impossible to complete the sampling process smoothly. Summary of the Invention

[0004] In view of the problems in the related technologies, the present invention proposes a drilling device and a drilling method for undisturbed soil freezing sampling, so as to overcome the above-mentioned technical problems existing in the existing related technologies.

[0005] To solve the above-mentioned technical problems, the present invention is achieved through the following technical solution: The present invention is a drilling device, including a drilling drive unit and a drill head. The drilling drive unit can drive the drill head to perform lifting and rotating movements simultaneously, so that the drill head can drill downwards. The drill bit includes a drilling unit, a diameter adjustment unit, and a wall protection unit. The drilling unit can drill holes when drilling downwards. The diameter adjustment unit can adjust the diameter of the drilling unit to adjust the diameter of the hole drilled by the drilling unit. The wall protection unit can compact and smooth the inner wall of the hole drilled by the drilling unit when rotating downwards. Moreover, the wall protection unit can synchronously extend and retract with the drilling unit when the diameter adjustment unit adjusts the diameter of the drilling unit, so that the diameter of the wall protection unit is always adapted to the diameter of the drilling unit.

[0006] Preferably, the drilling unit includes a spindle, the top end of which is provided with a connector for connecting to the drilling drive unit, and the bottom end of which is fixedly mounted with a pilot drill bit; The outer ring of the spindle is circumferentially equipped with multiple drilling units, which can surround to form a conical drilling structure. The pilot drill bit is located at the tip of the conical drilling structure. The variable diameter adjustment unit can drive the multiple drilling units to rotate and move along the pilot drill bit to adjust the inclination angle of the drilling units, thereby adjusting the diameter of the conical drilling structure.

[0007] Preferably, the drilling unit includes a bottom support plate and a support plate. The bottom support plate is fixedly installed on the top surface of the pilot drill bit. The bottom end of the support plate is rotatably connected to the bottom support plate through a connecting shaft. The top end of the support plate is drivenly connected to a diameter adjustment unit. The diameter adjustment unit can drive the support plate to rotate around the connecting shaft as a fulcrum. A toothed plate is fixedly installed on the outer side of the support plate, and the outer surface of the toothed plate is provided with drilling teeth.

[0008] Preferably, the variable diameter adjustment unit includes a telescopic drive component and multiple guide grooves. The multiple guide grooves are circumferentially distributed on the side wall of the main shaft, and each guide groove corresponds to a multiple drilling unit. The telescopic drive component is fixedly installed inside the main shaft, and a sliding block is fixedly installed at the telescopic end of the telescopic drive component. A toothed plate adjusting rod is rotatably installed on the outer ring of the sliding block. One end of the toothed plate adjusting rod extends to the outside of the main shaft through the guide groove and is rotatably installed with a toothed plate adjusting shaft. The toothed plate adjusting shaft is rotatably connected to the top end of the support plate.

[0009] Preferably, the wall protection unit includes a plurality of scrapers corresponding one-to-one with the toothed plates. The bottom end of the scraper is rotatably mounted on the corresponding toothed plate adjusting shaft, and the top end of the scraper is rotatably mounted on the scraper adjusting shaft. A scraper adjusting rod is rotatably mounted on the scraper adjusting shaft. One end of the scraper adjusting rod passes through the guide groove and is rotatably connected to the sliding block. The scraper adjusting rod and the toothed plate adjusting rod are of the same length and are arranged in parallel.

[0010] Preferably, the scraper includes a positioning plate, the upper and lower ends of which are rotatably connected to the scraper adjustment shaft and the toothed plate adjustment shaft, respectively. A positioning bracket is fixedly installed on the positioning plate, and a telescopic groove is provided inside the positioning bracket. A slider is slidably installed inside the telescopic groove. An elastic support member is installed at the inner end of the slider. A connecting plate extending to the outside of the positioning bracket is fixedly installed at the outer end of the slider. A flexible scraper strip is fixedly installed on the connecting plate.

[0011] Preferably, the drill bit further includes a telescopic protective cover, which covers and is disposed outside the drilling unit, the diameter adjustment unit, and the wall protection unit to isolate and protect the drilling unit, the diameter adjustment unit, and the wall protection unit. The telescopic protective cover is provided with an opening for the drilling unit and the wall protection unit to pass through. The opening is sealed to the side wall of the drilling unit and the wall protection unit by a sealing strip. The telescopic protective cover can extend and retract synchronously when the diameter adjustment unit drives the drilling unit and the wall protection unit to extend and retract, so that the telescopic protective cover can always be tightly attached to the outside of the drilling unit and the wall protection unit. The telescopic protective cover includes an integrated drill bit protective cover and a spindle protective cover. The drill bit protective cover covers the outside of the drilling unit and the wall protection unit, and the spindle protective cover covers the outside of the guide groove on the spindle. The drill bit protective cover has multiple openings. The inner side of the drill bit protective cover is fixedly installed with a positioning buckle that can be engaged with the connecting shaft inside the drilling unit and the wall protection unit. The top of the spindle protective cover is provided with a positioning ring sleeve that is fixedly fitted on the spindle. The inner sides of both the drill bit protective cover and the spindle protective cover are provided with bending grooves.

[0012] Preferably, the drilling device further includes a PCM sleeve, which includes a sleeve part made of phase change buffer material. The top end of the sleeve part is provided with a connector for connecting to the drilling drive part. The sleeve part can expand and abut against the hole drilled by the drill bit when inflated. The interior of the sleeve part can be filled with liquid nitrogen so that the liquid nitrogen can cool and freeze the soil around the hole after being buffered by the sleeve part wall. The sleeve includes an inner protective layer, an intermediate buffer layer, and an outer protective layer. The inner and outer protective layers are made of flexible films, and the intermediate buffer layer is made of a phase change material. An inflation port and a liquid nitrogen delivery port that communicate with the inside of the sleeve are fixedly installed on the connector.

[0013] Preferably, the drilling drive unit includes a bracket and multiple drill rods. A lifting slide rail and a lifting drive component are fixedly installed on the bracket. A lifting seat is slidably installed on the lifting slide rail. The lifting drive component can drive the lifting seat to slide up and down along the lifting slide rail. A drive motor that can drive the drill rods to rotate is installed on the lifting seat. Multiple drill rods can be sequentially spliced ​​to form a long guide rod structure.

[0014] This invention also discloses a drilling method for undisturbed soil freezing sampling, the specific steps of which are as follows: First, the diameter of the drilling unit and the wall protection unit is increased by adjusting the diameter adjustment unit. Then, the drill head is driven to rotate downward and drill through the drilling drive unit. At this time, the drilling unit rotates downward to drill, while the wall protection unit compacts and smooths the inner wall of the hole drilled by the drilling unit during the downward rotation. When the drill bit reaches the sampling depth, the diameter of the drilling unit and the wall protection unit are reduced by adjusting the diameter adjustment unit. Then, the drill bit continues to rotate downward and drill through the drilling drive unit to drill the sampling hole through the drilling unit. At the same time, the wall protection unit compacts and smooths the inner wall of the sampling hole during the downward rotation. After the sampling hole is drilled, the diameter of the drilling unit and the wall protection unit is further adjusted and reduced by the diameter adjustment unit so that the diameter of the drilling unit and the wall protection unit is smaller than the inner diameter of the sampling hole. Finally, the drill bit is lifted and removed by the drilling drive unit to complete the drilling process.

[0015] The present invention has the following beneficial effects: 1. In this invention, the diameter of the drilling unit can be adjusted by means of a variable diameter adjustment unit. In the initial stage of drilling, the diameter of the drilling unit can be increased by means of the variable diameter adjustment unit, so that a channel hole with a larger diameter can be drilled. After the drilling reaches the sampling depth, the diameter of the drilling unit can be decreased by means of the variable diameter adjustment unit, so that a sampling hole with a smaller diameter can be drilled through the drilling unit. This facilitates the unobstructed removal of subsequent sampling tools and sample soil columns without the need to change to different diameter drill bits during the drilling process, making the drilling process more convenient and faster, and improving drilling efficiency and sampling efficiency.

[0016] 2. In this invention, a wall-protecting unit is provided inside the drill bit. The wall-protecting unit can compact and smooth the inner wall of the hole drilled by the drilling unit when it rotates and moves downward with the drilling unit, thereby improving the stability of the inner wall of the hole and preventing the hole wall from collapsing and deforming due to the soft soil layer. This not only helps to improve the integrity of the soil sampling column, but also facilitates the movement and transportation of the soil sampling column, ensuring the smooth completion of the sampling process. Moreover, when the diameter adjustment unit adjusts the diameter of the drilling unit, the wall-protecting unit can synchronously extend and retract with the drilling unit, so that the diameter of the wall-protecting unit always matches the diameter of the drilling unit, so that the wall-protecting unit can always compact and smooth the inner wall of the hole drilled by the drilling unit, thereby improving the drilling stability.

[0017] 3. In this invention, a telescopic protective cover isolates and protects the drilling unit, the diameter adjustment unit, and the wall protection unit, preventing sand and debris generated during drilling from entering their interiors and thus blocking them. This ensures smooth telescopic adjustment of the drilling unit, diameter adjustment unit, and wall protection unit. Furthermore, the telescopic protective cover can extend and retract synchronously with the diameter adjustment unit while driving the drilling unit and wall protection unit to extend and retract, ensuring that the telescopic protective cover always fits tightly against the outside of the drilling unit and wall protection unit, thereby improving the protective effect on the drilling unit and wall protection unit.

[0018] 4. This invention incorporates a sampling sleeve made of phase change material (PCM). Leveraging the latent heat storage characteristics of PCM, a constant-temperature thermal buffer layer is constructed between the liquid nitrogen cold source and the soil. Utilizing the PCM's characteristic of maintaining a constant temperature during phase change, the ultra-low temperature of liquid nitrogen (-196℃) is converted into a controllable, slightly below-freezing temperature (-3℃ to -5℃). This allows the soil around the sleeve to undergo initial consolidation under constant-temperature conditions, forming a dense frozen shell. This frozen shell eliminates the driving force for moisture migration caused by the thermal gradient of the initial freezing process and blocks pore channels, providing a physical barrier for the subsequent deep freezing stage (a sudden temperature drop after PCM depletion). Even if the temperature difference increases in the second stage, moisture from the unfrozen outer area cannot cross this barrier to reach the freezing front, thus fundamentally inhibiting the formation of ice lenses. This prevents soil volume expansion (frost heave) caused by ice lenses, which would disrupt the original connections between soil particles, leading to layered cracks, increased porosity, altered permeability, and loss of representativeness in the soil sample. This improves the accuracy of subsequent testing data.

[0019] Of course, any product implementing this invention does not necessarily need to achieve all of the advantages described above at the same time. Attached Figure Description

[0020] To more clearly illustrate the technical solutions of the embodiments of the invention, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0021] Figure 1 This is a three-dimensional structural diagram of the drilling device of the present invention; Figure 2 For the present invention Figure 1 A magnified structural diagram at point A; Figure 3 This is a three-dimensional structural diagram of the drilling drive unit of the present invention; Figure 4This is one of the three-dimensional structural schematic diagrams of the drill bit of the present invention; Figure 5 This is a second three-dimensional structural schematic diagram of the drill bit of the present invention; Figure 6 For the present invention Figure 5 A magnified structural diagram at point B; Figure 7 This is the third three-dimensional structural schematic diagram of the drill bit of the present invention; Figure 8 For the present invention Figure 7 A magnified structural diagram at point C; Figure 9 This is a schematic diagram of the drill bit tooth plate of the present invention when unfolded; Figure 10 This is a schematic diagram of the structure of the drill bit tooth plate of the present invention during retraction; Figure 11 This is a three-dimensional structural diagram of the telescopic protective cover of the present invention; Figure 12 For the present invention Figure 11 A magnified structural diagram at point D; Figure 13 This is a schematic diagram of the connection structure between the drilling drive unit and the PCM sleeve of the present invention; Figure 14 This is a three-dimensional structural diagram of the PCM sleeve of the present invention; Figure 15 This is a schematic diagram of the internal structure of the PCM sleeve of the present invention; Figure 16 For the present invention Figure 15 A magnified structural diagram at point E; Figure 17 This is a three-dimensional structural diagram of the PCM sleeve sampling process of the present invention; Figure 18 This is a top-view cross-sectional structural diagram of the PCM sleeve of the present invention.

[0022] In the diagram: 1. Drilling drive unit; 11. Drill rod; 12. Support; 13. Lifting seat; 14. Lifting slide rail; 15. Lifting drive component; 2. Drill head; 21. Spindle; 22. Connector; 23. Pilot drill bit; 24. Tooth plate; 25. Scraper; 26. Telescopic protective cover; 27. Guide groove; 28. Sliding block; 29. ​​Telescopic drive component; 210. Bottom support plate; 211. Support plate; 212. Tooth plate adjusting shaft; 213. Tooth plate adjusting rod; 214. Scraper adjusting shaft; 215. Scraper adjusting rod; 2501 2502 Flexible scraper; 2503 Positioning plate; 2504 Positioning bracket; 2505 Telescopic slide; 2506 Slider; 2507 Elastic support; 2508 Connecting plate; 2609 Drill bit guard; 26000 Spindle guard; 26001 Opening; 26002 Positioning buckle; 26003 Bending groove; 36004 PCM sleeve; 31 Sleeve part; 32 Joint part; 33 Inflation interface; 34 Liquid nitrogen delivery interface; 3101 Inner protective layer; 3102 Intermediate buffer layer; 3103 Outer protective layer. Detailed Implementation

[0023] Many specific details are set forth in the following description in order to provide a full understanding of the invention. However, the invention may also be practiced in other ways different from those described herein, and those skilled in the art can make similar extensions without departing from the spirit of the invention. Therefore, the invention is not limited to the specific embodiments disclosed below.

[0024] Secondly, the term "one embodiment" or "embodiment" as used herein refers to a specific feature, structure, or characteristic that may be included in at least one implementation of the present invention. The phrase "in one embodiment" appearing in different places in this specification does not necessarily refer to the same embodiment, nor is it a single or selective embodiment that is mutually exclusive with other embodiments.

[0025] Example 1 Please see Figure 1 , Figure 9 , Figure 10 As shown, this embodiment is a drilling device, including a drilling drive unit 1 and a drill head 2. The drilling drive unit 1 can drive the drill head 2 to perform lifting and rotating movements simultaneously, so that the drill head 2 can drill downwards. The drill head 2 includes a drilling unit, a diameter adjustment unit, and a wall protection unit. The drilling unit can drill holes when drilling downwards. The diameter adjustment unit can adjust the diameter of the drilling unit to adjust the diameter of the hole drilled by the drilling unit. The wall protection unit can compact and smooth the inner wall of the hole drilled by the drilling unit when rotating downwards. Moreover, the wall protection unit can synchronously extend and retract with the drilling unit when the diameter adjustment unit adjusts the diameter of the drilling unit, so that the diameter of the wall protection unit is always adapted to the diameter of the drilling unit.

[0026] When drilling for cryogenic sampling in soft geological conditions, the diameter of the drilling unit and the wall protection unit is first increased by adjusting the diameter adjustment unit. Then, the drill head 2 is driven downward by the drilling drive unit 1 to rotate and drill. At this time, the drilling unit rotates downward to drill the hole, while the wall protection unit compacts and smooths the inner wall of the hole drilled by the drilling unit during its downward rotation. When the drill head 2 reaches the sampling depth, the diameter of the drilling unit and the wall protection unit is reduced by adjusting the diameter adjustment unit. Then, the drill head 2 continues to rotate downward by the drilling drive unit 1 to drill the sampling hole through the drilling unit. At the same time, the wall protection unit compacts and smooths the inner wall of the sampling hole during its downward rotation. After the sampling hole is drilled, the diameter of the drilling unit and the wall protection unit is further reduced by adjusting the diameter adjustment unit so that the diameter of the drilling unit and the wall protection unit is smaller than the inner diameter of the sampling hole. Finally, the drill head 2 is lifted upward by the drilling drive unit 1 to complete the drilling process.

[0027] In the initial stage of drilling, the diameter of the borehole unit can be increased by adjusting the diameter of the borehole unit, thereby drilling a larger diameter channel hole. After drilling reaches the sampling depth, the diameter of the borehole unit can be decreased by adjusting the diameter of the borehole unit again, so as to drill a smaller diameter sampling hole. This facilitates the unimpeded removal of subsequent sampling tools and soil sample columns without the need to change drill bits of different diameters during the drilling process, making the drilling process more convenient and faster, and improving drilling and sampling efficiency. The wall protection unit compacts and smooths the inner wall of the hole drilled by the borehole unit, thereby improving the stability of the inner wall of the hole and preventing the collapse and deformation of the borehole wall due to the soft soil layer. This not only helps to improve the integrity of the soil sample column, but also facilitates the movement and transportation of the soil sample column, ensuring the smooth completion of the sampling process. Moreover, the wall protection unit can expand and contract synchronously with the borehole unit when the diameter of the borehole unit is adjusted by the diameter adjustment unit, so that the diameter of the wall protection unit is always adapted to the diameter of the borehole unit.

[0028] Example 2 Please see Figure 1 , Figure 3 As shown, the difference between this embodiment and the above embodiment is that the drilling drive unit 1 includes a bracket 12 and a plurality of drill rods 11. A lifting slide rail 14 and a lifting drive component 15 are fixedly installed on the bracket 12. A lifting seat 13 is slidably installed on the lifting slide rail 14. The lifting drive component 15 can drive the lifting seat 13 to slide up and down along the lifting slide rail 14. A drive motor that can drive the drill rods 11 to rotate is installed on the lifting seat 13. The plurality of drill rods 11 can be spliced ​​together in sequence to form a long guide rod structure. During drilling, the drill head 2 is installed at the bottom of the drill rod 11. The drill rod 11 is driven to rotate by the drive motor, which in turn drives the drill head 2 to rotate synchronously. At the same time, the lifting drive component 15 (which adopts a hydraulic telescopic shaft) drives the lifting seat 13 to slide downward along the lifting slide rail 14, so as to drive the drive motor, drill rod 11 and drill head 2 to move downward synchronously, so that the drill head 2 can gradually drill downward. In the subsequent drilling process, new drill rods 11 can be continuously added between the top drill rod 11 and the drill head 2, so that multiple drill rods 11 can be spliced ​​together to form a long guide rod structure, thereby increasing the drilling depth of the drill head 2.

[0029] Example 3 Please see Figure 1 , Figure 2 , Figures 4-10 As shown, the difference between this embodiment and the above embodiment is that the drilling unit includes a spindle 21, the top end of the spindle 21 is provided with a connector 22 for connecting with the drilling drive unit 1, and the bottom end of the spindle 21 is fixedly installed with a pilot drill bit 23; multiple drilling units are circumferentially installed on the outer ring of the spindle 21, and the multiple drilling units can surround to form a conical drilling structure, and the pilot drill bit 23 is located at the cone tip of the conical drilling structure. The diameter adjustment unit can drive the multiple drilling units to rotate and move along the pilot drill bit 23 to adjust the inclination angle of the drilling units, thereby adjusting the diameter of the conical drilling structure.

[0030] During drilling, the pilot drill bit 23 and multiple drilling units surround and form a conical drilling structure to carry out drilling. The fixed pilot drill bit 23 first cuts into the formation and plays a guiding role, opening a drilling channel for the subsequent conical drilling structure in advance, which can reduce the drilling resistance of the conical drilling structure and improve the stability of drilling.

[0031] Furthermore, the drilling unit includes a bottom support plate 210 and a support plate 211. The bottom support plate 210 is fixedly installed on the top surface of the pilot drill bit 23. The bottom end of the support plate 211 is rotatably connected to the bottom support plate 210 via a connecting shaft. The top end of the support plate 211 is drively connected to the diameter adjustment unit. The diameter adjustment unit can drive the support plate 211 to rotate around the connecting shaft as the fulcrum. A toothed plate 24 is fixedly installed on the outer side of the support plate 211. The outer surface of the toothed plate 24 is provided with drilling teeth. The diameter adjustment unit includes a telescopic drive component 29 and multiple guide slots. 27. Multiple guide grooves 27 are arranged in a circular pattern on the side wall of the main shaft 21, and each guide groove 27 corresponds to a drilling unit. The telescopic drive component 29 is fixedly installed inside the main shaft 21, and a sliding block 28 is fixedly installed at the telescopic end of the telescopic drive component 29. A toothed plate adjusting rod 213 is rotatably installed on the outer ring of the sliding block 28. One end of the toothed plate adjusting rod 213 extends to the outside of the main shaft 21 through the guide groove 27 and is rotatably installed with a toothed plate adjusting shaft 212. The toothed plate adjusting shaft 212 is rotatably connected to the top end of the support plate 211.

[0032] The telescopic drive component 29 is a hydraulic telescopic shaft or an electric telescopic shaft. The telescopic drive component 29 can drive the sliding block 28 to slide up and down in the main shaft 21. When the sliding block 28 slides down, the sliding block 28 pushes the upper end of the support plate 211 outward through the toothed plate adjusting rod 213. At this time, the support plate 211 rotates outward with the bottom connecting shaft as the fulcrum, and drives the toothed plate 24 to rotate outward, thereby increasing the diameter of the conical drilling structure formed by multiple toothed plates 24, so that the diameter of the hole that the conical drilling structure can drill is increased. When the sliding block 28 slides upward, the sliding block 28 pulls the upper end of the support plate 211 inward through the toothed plate adjusting rod 213. At this time, the support plate 211 rotates inward with the bottom connecting shaft as the fulcrum, and drives the toothed plate 24 to rotate inward, thereby reducing the diameter of the conical drilling structure formed by multiple toothed plates 24, so that the diameter of the hole that the conical drilling structure can drill is reduced.

[0033] Example 4 Please see Figure 1 , Figure 2 , Figures 5-12 As shown, the difference between this embodiment and the above embodiment is that the wall protection unit includes multiple scrapers 25 corresponding to the toothed plates 24 one by one. The bottom end of the scraper 25 is rotatably mounted on the corresponding toothed plate adjusting shaft 212, and the top end of the scraper 25 is rotatably mounted on the scraper adjusting shaft 214. A scraper adjusting rod 215 is rotatably mounted on the scraper adjusting shaft 214. One end of the scraper adjusting rod 215 passes through the guide groove 27 and is rotatably connected to the sliding block 28. The scraper adjusting rod 215 and the toothed plate adjusting rod 213 have the same length and are arranged in parallel.

[0034] When the sliding block 28 moves up and down, and the tilt angle of the toothed plate 24 is adjusted by the toothed plate adjusting rod 213, the toothed plate adjusting rod 213 simultaneously pushes and pulls the bottom end of the scraper 25 so that the bottom end of the scraper 25 and the top end of the toothed plate 24 are in the same vertical line. At the same time, the sliding block 28 pushes and pulls the upper end of the scraper 25 through the scraper adjusting rod 215. Since the scraper adjusting rod 215 and the toothed plate adjusting rod 213 are of the same length and are set in parallel, a parallelogram structure is formed between the scraper 25, the main shaft 21, the scraper adjusting rod 215 and the toothed plate adjusting rod 213. This ensures that the scraper 25 remains parallel to the main shaft 21 (the drilled hole) during the adjustment process, so that the scraper 25 can always maintain stable contact with the hole wall, thereby improving the scraping and compaction effect of the scraper 25 on the hole wall.

[0035] Furthermore, the scraper 25 includes a positioning plate 2502. The upper and lower ends of the positioning plate 2502 are rotatably connected to the scraper adjustment shaft 214 and the toothed plate adjustment shaft 212, respectively. A positioning bracket 2503 is fixedly installed on the positioning plate 2502. A telescopic groove 2504 is provided inside the positioning bracket 2503. A slider 2505 is slidably installed inside the telescopic groove 2504. An elastic support member 2506 is installed abutting against the inner end of the slider 2505. A connecting plate 2507 extending to the outside of the positioning bracket 2503 is fixedly installed on the outer end of the slider 2505. A flexible scraper strip 2501 is fixedly installed on the connecting plate 2507.

[0036] The outer edge of the flexible scraper 2501 extends to the outermost part of the top of the toothed plate 24, and the outer diameter of the wall protection unit composed of multiple flexible scrapers 2501 is slightly larger than the inner diameter of the hole drilled by the toothed plate 24. This allows the flexible scraper 2501 to elastically abut against the inner wall of the hole under the elastic force of the elastic support 2506, thereby improving the scraping and compaction effect of the flexible scraper 2501 on the inner wall of the hole when it rotates.

[0037] Furthermore, the drill bit 2 also includes a telescopic protective cover 26. The telescopic protective cover 26 covers and is disposed outside the drilling unit, the diameter adjustment unit, and the wall protection unit to isolate and protect them, preventing sand and debris generated during drilling from entering their interiors. This prevents the drilling unit, diameter adjustment unit, and wall protection unit from being blocked, ensuring smooth telescopic adjustment. The telescopic protective cover 26 has an opening 2603 for the drilling unit and wall protection unit to pass through, allowing the drilling unit... The toothed plate 24 and the scraper 25 inside the wall protection unit can extend to the outside through the opening 2603 for drilling and wall protection. The opening is sealed to the side wall of the drilling unit and the wall protection unit through a sealing strip to improve the protective effect of the telescopic protective cover 26 and prevent sand and soil debris generated during drilling from entering the interior of the telescopic protective cover 26 through the opening. The telescopic protective cover 26 can also be adjusted synchronously when the diameter adjustment unit drives the drilling unit and the wall protection unit to adjust their extension and retraction, so that the telescopic protective cover 26 can always be tightly attached to the outside of the drilling unit and the wall protection unit, thereby improving the protective effect of the drilling unit and the wall protection unit.

[0038] Specifically, the telescopic protective cover 26 includes an integrated drill bit protective cover 2601 and a spindle protective cover 2602. The drill bit protective cover 2601 covers the outside of the drilling unit and the wall protection unit, and the spindle protective cover 2602 covers the outside of the guide groove 27 on the spindle 21. The drill bit protective cover 2601 has multiple openings 2603. The inner side of the drill bit protective cover 2601 is fixedly installed with a positioning buckle 2604 that can be engaged with the connecting shaft in the drilling unit and the wall protection unit. The top of the spindle protective cover 2602 is provided with a positioning ring sleeve that is fixedly fitted on the spindle 21. The inner sides of both the drill bit protective cover 2601 and the spindle protective cover 2602 are provided with bending grooves 2605.

[0039] The drill bit guard 2601 has vertically arranged bending grooves 2605 on its inner wall, and multiple bending grooves 2605 are evenly and equidistantly distributed along the circumference of the drill bit guard 2601. This allows the drill bit guard 2601 to synchronously contract and extend through the bending grooves 2605 on its inner wall under the action of the positioning buckle 2604 when the drilling unit and the wall protection unit are adjusted. The spindle guard 2602 has an annular groove on its inner wall, and multiple annular grooves are evenly and equidistantly distributed along the radial direction of the spindle guard 2602. This allows the sliding block 28 to move up and down, and the positioning buckle 2604 at the upper end to drive the lower end of the spindle guard 2602 to extend downward or contract and fold upward.

[0040] Example 5 Please see Figures 13-18 As shown, the difference between this embodiment and the above embodiment is that the drilling device also includes a PCM sleeve 3. The PCM sleeve 3 includes a sleeve part 31 made of phase change buffer material. The top end of the sleeve part 31 is provided with a connector part 32 for connecting with the drilling drive part 1. The sleeve part 31 can expand and abut against the hole drilled by the drill head 2 when inflated. The inside of the sleeve part 31 can be filled with liquid nitrogen so that the liquid nitrogen can cool and freeze the soil around the hole after being buffered by the sleeve wall of the sleeve part 31. During the freezing and sampling of soft soil using liquid nitrogen, the initial temperature of the frozen soil is typically 5-15℃ (affected by the geothermal gradient), while the temperature of liquid nitrogen is -196℃, resulting in a temperature difference exceeding 200℃. According to thermodynamic theory, the rate of water migration is proportional to the temperature gradient. This huge temperature difference leads to a sharp increase in suction at the freezing front, driving pore water in the unfrozen area to migrate rapidly towards the freezing front. Experiments show that under these conditions, the water migration rate can reach several millimeters per hour, far exceeding the soil freezing rate. This causes a large accumulation of water in front of the freezing front. During the freezing process, the temperature needs to slowly decrease from the initial temperature to below -5℃, traversing the abrupt phase transition range of -1℃ to -5℃. Within this range, the pore water in the soil begins to freeze, but at a slower rate (because the cold energy needs to be slowly conducted through the already frozen layer). The accumulated water forms a continuous ice layer (ice lens) at the freezing front, with a thickness ranging from several millimeters to several centimeters. The formation of ice lenses causes soil volume expansion (frost heave), disrupting the original bonds between soil particles, resulting in layered cracks, increased void ratio, and altered permeability in the soil sample, completely losing its original representativeness. Subsequent laboratory tests (such as triaxial compression and permeability tests) will show results that deviate significantly from the true values.

[0041] In this embodiment, a sleeve 31 made of phase change material is provided. By utilizing the latent heat storage characteristics of the phase change material, a constant temperature thermal buffer layer is constructed between the liquid nitrogen cold source and the soil. By utilizing the characteristic that the temperature of the phase change material remains constant during the phase change process, the ultra-low temperature of liquid nitrogen (-196℃) is converted into a controllable constant temperature (-3℃ to -5℃) slightly below the freezing point. This allows the soil around the outer ring of the sleeve to complete the initial consolidation under constant temperature conditions, forming a dense frozen shell. This frozen shell eliminates the driving force for water migration caused by the thermal gradient of the initial freezing and blocks the pore channels, providing a physical barrier for the subsequent deep freezing stage (the temperature drops sharply after the PCM is depleted). Even if the temperature difference increases in the second stage, the water in the outer unfrozen area cannot cross this barrier to reach the freezing front, thereby fundamentally inhibiting the formation of ice lenses. This prevents the soil volume from expanding (frost heave) due to the formation of ice lenses, which would damage the original connection between soil particles, causing the soil sample to have layered cracks, increased void ratio, and changed permeability, losing its original representativeness and improving the accuracy of subsequent detection data.

[0042] Specifically, the sleeve portion 31 includes an inner protective layer 3101, an intermediate buffer layer 3102, and an outer protective layer 3103. The inner protective layer 3101, the intermediate buffer layer 3102, and the outer protective layer 3103 are all made of flexible film. The intermediate buffer layer 3102 is made of phase change material (PCM). An inflation port 33 and a liquid nitrogen delivery port 34 that communicate with the inside of the sleeve portion 31 are fixedly installed on the connector portion 32. The flexible film is a multi-layer composite film. The inner layer (the side in contact with the intermediate buffer layer 3102) is a polytetrafluoroethylene (PTFE) film, which has excellent low-temperature resistance and chemical inertness and does not adhere to PCM. The middle layer is a polyimide (PI) film, which provides high strength and high toughness and a wide temperature range (-269℃ to +300℃). The outer layer (the side in contact with the soil) is a reinforced silicone film, which has good flexibility and wear resistance and can adapt to irregular pore walls. The intermediate buffer layer 3102 uses organic PCMs as phase change materials, such as paraffins (mixtures of n-alkanes) and fatty acids, which have the advantages of low supercooling, chemical stability, and non-corrosiveness. The phase change temperature can be precisely controlled by adjusting the carbon chain length. For example, the phase change temperature of tetradecane (C14H30) is about 5.5℃, which can be lowered to -3℃ by compounding it with hexadecane and other materials.

[0043] Alternatively, inorganic PCMs, such as hydrated salts, have high latent heat of phase change but are prone to supercooling and phase separation. Nucleating agents and thickeners need to be added.

[0044] Alternatively, composite PCM can be used: PCM is adsorbed into a porous matrix (such as expanded graphite or diatomaceous earth) to form a shaped composite phase change material, which can prevent leakage and improve thermal conductivity. Composite PCM with a thermal conductivity ≥0.5 W / (m·K) is preferred.

[0045] It is also equipped with three sets of temperature detection sensors, among which, Sensor 1: Attached to the outer surface of the outer film of the sleeve part 31 (detects the temperature of the interface between the sleeve part 31 and the soil, used to determine whether the phase change platform of the PCM inside the sleeve part 31 has ended).

[0046] Sensor 2: Pre-embedded in the soil near sleeve part 31 (5cm, 10cm away from the hole wall, etc., to monitor the advance of the freezing front. When the temperature at 15cm away from the hole wall drops to -5℃, freezing is considered complete).

[0047] Sensor 3: Attached to the inner wall of sleeve 31 (monitors the temperature of the liquid nitrogen chamber to determine whether the liquid nitrogen supply is normal and whether the PCM is depleted).

[0048] During sampling, the sleeve 31 is connected to the drill rod 11 via the connector 32, the air inlet 33 is connected to the air pump via the air inlet pipe, and the liquid nitrogen delivery inlet 34 is connected to the liquid nitrogen storage tank via the pipe. The sleeve 31 is lowered into the sampling hole via the drill rod 11. Compressed air is slowly injected into the inner cavity of the sleeve 31 via the air pump, and the sleeve 31 gradually expands with air so that the outer wall of the sleeve 31 is tightly attached to the hole wall of the sampling hole. Open the liquid nitrogen supply line valve on the liquid nitrogen storage tank and begin injecting liquid nitrogen into the sleeve section 31 at a small flow rate (e.g., 3 L / min). Monitor the temperature sensor: observe the temperature change of the PCM layer (sensor one). When the temperature drops to the phase transition point (e.g., -3℃) and remains constant, it indicates that the PCM has begun a phase transition and entered the thermal buffer stage. Record the start time of the phase transition. During this stage, the flow rate should be kept low, and the temperature difference should be controlled within 8-10℃ to allow the soil attached to the sleeve section 31 to freeze slowly, forming a dense frozen shell (approximately 1-2 cm thick). The goal of this stage is to establish a physical barrier, rather than pursuing a deep freezing depth.

[0049] During the PCM phase transition (approximately 20-30 minutes, depending on the thickness of the intermediate buffer layer 3102), the soil slowly freezes at a temperature difference of approximately 8°C. The internal temperature of the soil is monitored (sensor 2), and the progress of the freezing front is observed. At this time, the internal temperature of the soil should decrease slowly without any obvious abrupt change. During this stage, the liquid nitrogen flow rate can be finely adjusted based on the sensor data to prolong the phase transition time (the frozen shell formed during this stage will gradually block the pore channels, preparing for the subsequent stages).

[0050] When the temperature of the PCM layer (sensor 1) continues to decrease (below the phase transition point), it indicates that the latent heat of the PCM has been exhausted, and the sensible heat cooling stage has begun. At this point, the liquid nitrogen flow rate can be appropriately increased (e.g., 10 L / min) to accelerate the freezing rate. Since a dense ice layer has formed on the surface, the water migration channels are blocked, and the internal soil will not be disturbed. Continue freezing until the target freezing radius is reached (usually 15-20 cm). Refer to the data from sensor 2; when the temperature at 15 cm from the borehole wall drops below -5℃, freezing is considered complete. (Although the temperature difference increases in the second stage (-5℃ → -196℃), since a dense frozen shell has been formed in the first stage, the water migration channels in the outer unfrozen area are cut off, so no new ice lenses will be generated).

[0051] After deep freezing reaches the target freezing radius (temperature drops below -5℃ at 15cm from the borehole wall), the liquid nitrogen valve is closed. The frozen soil column is then separated from the surrounding strata using a rotary shearing method, as follows: 1. Static Equilibrium: After turning off the liquid nitrogen, allow the soil column to stand for 1-2 minutes to stabilize the temperature field and eliminate thermal stress. At the same time, monitor the freezing front temperature (sensor 2) to ensure that it is still within the range of -1℃ to -5℃ (if it is higher than -1℃, the static time can be shortened appropriately; if it is lower than -5℃, the static time can be extended appropriately).

[0052] 2. Apply torsional torque: Apply a slow, continuous torsional torque to drill pipe 11 via the drive motor. The initial torque should be small (e.g., 500 N·m), gradually increasing while monitoring torque changes.

[0053] 3. Shear fracture judgment: When the torque reaches a certain peak and then suddenly drops, it indicates that the connection at the frozen front has been sheared off. At this time, drill pipe 11 can rotate freely at a certain angle (usually 5-15°).

[0054] 4. Axial pre-tension: While rotating or after rotation, apply a slight upward pre-tension force (e.g., 5-10 kN) to drill rod 11 and check if the soil column has completely separated. If the lifting force increases significantly, pause and continue rotating until complete separation. After separation, gently lift the drill rod up and down; if there is no significant change in resistance, it indicates complete separation.

[0055] Finally, the drill rod 11 is lifted, and the frozen soil sample, along with the sleeve 31, is pulled out of the borehole to obtain the original frozen soil sample.

[0056] Example 6 This embodiment discloses a drilling method for undisturbed soil freezing sampling, the specific steps of which are as follows: First, the diameter of the drilling unit and the wall protection unit is increased by adjusting the diameter adjustment unit. Then, the drill head 2 is driven to rotate downward by the drilling drive unit 1. At this time, the drilling unit rotates downward to drill, while the wall protection unit compacts and smooths the inner wall of the hole drilled by the drilling unit during the downward rotation. When the drill bit 2 drills to the sampling depth, the diameter of the drilling unit and the wall protection unit is reduced by adjusting the diameter adjustment unit. Then, the drill bit 2 continues to rotate downward and drill through the drilling drive unit 1 to drill out the sampling hole through the drilling unit. At the same time, the wall protection unit compacts and smooths the inner wall of the sampling hole during the downward rotation. After the sampling hole is drilled, the diameter of the drilling unit and the wall protection unit is further adjusted and reduced by the diameter adjustment unit so that the diameter of the drilling unit and the wall protection unit is smaller than the inner diameter of the sampling hole. Finally, the drill head 2 is lifted and removed by the drilling drive unit 1 to complete the drilling process.

[0057] In the description of this specification, references to terms such as "an embodiment," "example," "specific example," etc., indicate that a specific feature, structure, material, or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of the invention. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples.

[0058] It should be noted that, for the sake of simplicity, the foregoing method embodiments are all described as a series of actions. However, those skilled in the art should understand that the present invention is not limited to the described order of actions, because according to the present invention, some steps can be performed in other orders or simultaneously. Furthermore, those skilled in the art should also understand that the embodiments described in the specification are all optional embodiments, and the actions and modules involved are not necessarily essential to the present invention.

Claims

1. A drilling apparatus, comprising a drilling drive unit and a drill head, characterized in that: The drilling drive unit can drive the drill bit to perform both lifting and rotating movements simultaneously, so that the drill bit can drill downwards. The drill bit includes a drilling unit, a diameter adjustment unit, and a wall protection unit. The drilling unit can drill holes when drilling downwards. The diameter adjustment unit can adjust the diameter of the drilling unit to adjust the diameter of the hole drilled by the drilling unit. The wall protection unit can compact and smooth the inner wall of the hole drilled by the drilling unit when rotating downwards. Moreover, the wall protection unit can synchronously extend and retract with the drilling unit when the diameter adjustment unit adjusts the diameter of the drilling unit, so that the diameter of the wall protection unit is always adapted to the diameter of the drilling unit. The drilling unit includes a spindle, the top of which is provided with a connector for connecting to the drilling drive unit. Multiple drilling units are circumferentially mounted on the outer ring of the spindle, and the multiple drilling units can surround each other to form a conical drilling structure. The drilling unit includes a bottom support plate and a support plate. The bottom end of the support plate is rotatably connected to the bottom support plate via a connecting shaft. The top end of the support plate is connected to a variable diameter adjustment unit. The variable diameter adjustment unit can drive the support plate to rotate around the connecting shaft as a fulcrum. A toothed plate is fixedly installed on the outer side of the support plate, and the outer side of the toothed plate is provided with drilling teeth. The variable diameter adjustment unit includes a telescopic drive component and multiple guide grooves. The multiple guide grooves are arranged in a circular pattern on the side wall of the main shaft, and each guide groove corresponds to a multiple drilling unit. The telescopic drive component is fixedly installed inside the main shaft, and a sliding block is fixedly installed at the telescopic end of the telescopic drive component. A toothed plate adjusting rod is rotatably installed on the outer ring of the sliding block. One end of the toothed plate adjusting rod extends to the outside of the main shaft through the guide groove and is rotatably installed with a toothed plate adjusting shaft. The toothed plate adjusting shaft is rotatably connected to the top end of the support plate. The wall protection unit includes multiple scrapers that correspond one-to-one with the toothed plates. The bottom end of each scraper is rotatably mounted on a corresponding toothed plate adjusting shaft, and the top end of each scraper is rotatably mounted on a scraper adjusting shaft. A scraper adjusting rod is rotatably mounted on the scraper adjusting shaft. One end of the scraper adjusting rod passes through a guide groove and is rotatably connected to a sliding block. The scraper adjusting rod and the toothed plate adjusting rod are of the same length and are arranged in parallel.

2. The drilling device according to claim 1, characterized in that: A pilot drill bit is fixedly installed at the bottom end of the main shaft; and the pilot drill bit is located at the tip of the conical drilling structure. The variable diameter adjustment unit can drive multiple drilling units to rotate and move along the pilot drill bit to adjust the inclination angle of the drilling units, thereby adjusting the diameter of the conical drilling structure.

3. A drilling device according to claim 2, characterized in that: The bottom support plate is fixedly installed on the top surface of the pilot drill bit.

4. A drilling device according to claim 3, characterized in that: The scraper includes a positioning plate, the upper and lower ends of which are rotatably connected to the scraper adjustment shaft and the toothed plate adjustment shaft, respectively. A positioning bracket is fixedly installed on the positioning plate. A telescopic groove is provided inside the positioning bracket. A slider is slidably installed inside the telescopic groove. An elastic support member is installed on the inner side of the slider. A connecting plate extending to the outside of the positioning bracket is fixedly installed on the outer side of the slider. A flexible scraper strip is fixedly installed on the connecting plate.

5. A drilling device according to claim 1, characterized in that: The drill bit also includes a telescopic protective cover, which covers and is disposed outside the drilling unit, the diameter adjustment unit, and the wall protection unit to isolate and protect them. The telescopic protective cover has an opening for the drilling unit and the wall protection unit to pass through. The opening is sealed to the side wall of the drilling unit and the wall protection unit by a sealing strip. The telescopic protective cover can extend and retract synchronously when the diameter adjustment unit drives the drilling unit and the wall protection unit to extend and retract, so that the telescopic protective cover can always be tightly attached to the outside of the drilling unit and the wall protection unit.

6. A drilling device according to claim 1, characterized in that: The drilling device also includes a PCM sleeve, which includes a sleeve part made of phase change buffer material. The top end of the sleeve part is provided with a connector for connecting with the drilling drive unit, so that the sleeve part can be lowered into the hole drilled by the drill bit via the drilling drive unit. The sleeve part can expand and abut against the hole drilled by the drill bit when inflated, and the interior of the sleeve part can be filled with liquid nitrogen, so that the liquid nitrogen can cool and freeze the soil around the hole after being buffered by the sleeve part wall.

7. A drilling apparatus according to any one of claims 1-6, characterized in that: The drilling drive unit includes a bracket and multiple drill rods. A lifting slide rail and a lifting drive component are fixedly installed on the bracket. A lifting seat is slidably installed on the lifting slide rail. The lifting drive component can drive the lifting seat to slide up and down along the lifting slide rail. A drive motor that can drive the drill rods to rotate is installed on the lifting seat. Multiple drill rods can be sequentially spliced ​​to form a long guide rod structure.

8. A drilling method for undisturbed soil cryogenic sampling, using the drilling apparatus as described in any one of claims 1-7, characterized in that, The specific steps are as follows: First, the diameter of the drilling unit and the wall protection unit is increased by adjusting the diameter adjustment unit. Then, the drill head is driven to rotate downward and drill through the drilling drive unit. At this time, the drilling unit rotates downward to drill, while the wall protection unit compacts and smooths the inner wall of the hole drilled by the drilling unit during the downward rotation. When the drill bit reaches the sampling depth, the diameter of the drilling unit and the wall protection unit is reduced by adjusting the diameter adjustment unit. Then, the drill bit continues to rotate downward by the drilling drive unit to drill a sampling hole with a smaller diameter at the bottom of the already drilled channel hole. At the same time, the wall protection unit compacts and smooths the inner wall of the sampling hole during the downward rotation. After the sampling hole is drilled, the diameter of the drilling unit and the wall protection unit is further adjusted and reduced by the diameter adjustment unit so that the diameter of the drilling unit and the wall protection unit is smaller than the inner diameter of the sampling hole. Finally, the drill bit is lifted and removed by the drilling drive unit to complete the drilling process.

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