Pile bottom sediment thickness intelligent detection device and method based on impact resilience

Abstract

The invention belongs to the technical field of cast-in-situ bored pile construction quality detection, and discloses an intelligent pile bottom sediment thickness detection device and method based on impact resilience. The device comprises a ground control and data processing system and an underground detection system which are connected through a cable, wherein an electromagnetic hammer capable of generating controllable impact, a reset spring, a probe and a multi-parameter sensor are arranged in the detection system. According to the method, the sediment surface is recognized through probe lowering and posture adjustment by means of tentative impact, then mechanical data are collected through formal impact, a sediment-bearing stratum interface is intelligently recognized based on a pressure-displacement curve inflection point, and the sediment thickness is calculated. According to the invention, high-precision, high-efficiency and non-damage detection of the thickness of the sediment at the pile bottom is realized.

Description

Technical Field

[0001] This invention relates to the field of drilling pile construction quality testing technology, and more specifically, to an intelligent detection device and method for pile bottom sediment thickness based on impact rebound. Background Technology

[0002] Drilled piles are widely used in various engineering foundations. However, after drilling, a weak sediment layer composed of drill cuttings, mud sediment, and other materials often remains at the bottom of the pile. This sediment layer significantly reduces the bearing capacity of the pile tip, increases the risk of settlement, and seriously affects the safety and durability of the pile foundation. Current standards impose strict limits on the thickness of the sediment layer at the pile bottom.

[0003] Currently, commonly used methods for detecting sediment thickness mainly include the hammer test, sediment analyzer method, and core drilling method. The hammer test relies on the operator's feel, which is highly subjective and has low accuracy; the sediment analyzer method involves expensive equipment and requires on-site calibration, resulting in high costs; while the core drilling method has high accuracy, it is a destructive testing method, which is inefficient, costly, and only suitable for sampling verification. In addition, the depth measurement of traditional methods is easily affected by factors such as steel cable tension and pile hole inclination, leading to benchmark deviations and further affecting the detection accuracy.

[0004] Therefore, there is an urgent need to develop an intelligent detection technology and equipment for pile bottom sediment thickness that is highly accurate, adaptable, efficient, and cost-effective. Summary of the Invention

[0005] (a) Purpose of the invention This invention aims to overcome the shortcomings of existing technologies and provide an intelligent detection device and method for pile bottom sediment thickness based on impact rebound, which has high detection accuracy, good stability, simple operation, and is suitable for mud environments.

[0006] (II) Technical Solution To achieve the above objectives, the present invention adopts the following technical solution: An intelligent detection device for pile bottom sediment thickness based on impact rebound includes a dynamic impact detection system and a ground control and data processing system; The dynamic impact detection system is connected to the winch in the ground control and data processing system via a steel cable, and is electrically connected to the instrument control box in the ground control and data processing system via a cable. The dynamic impact detection system includes a sealed protective housing, and an adaptive impact component and a multi-parameter sensing component disposed within the sealed protective housing; The adaptive impact assembly includes an electromagnetic hammer, a return spring, and a probe arranged coaxially, with the electromagnetic hammer connected to the probe via the return spring. The multi-parameter sensing component includes a pressure sensor for detecting impact pressure, a displacement sensor for detecting rebound displacement, and a tilt sensor for detecting attitude. The ground control and data processing system includes the winch, the instrument control box, and the data processing unit, which is communicatively connected to the instrument control box.

[0007] Furthermore, the electromagnetic hammer includes an electromagnetic coil and an impact hammer; the return spring is a cylindrical helical compression spring, with its two ends fixed to the bottom of the impact hammer and the top of the probe, respectively; the bottom end of the probe is a hemispherical structure with a non-stick coating sprayed on its surface.

[0008] Furthermore, the pressure sensor is built into the cylindrical mounting hole at the top of the probe; the displacement sensor is a differential transformer type displacement sensor, with its fixed end connected to the impact hammer and its moving end connected to the probe through a directional connector, and the sensing rod of the displacement sensor passes through the inner space of the return spring.

[0009] Furthermore, the sealed protective shell is a cylindrical body with a spiral guide groove on its outer surface and a buffer pad layer on its inner wall; both ends of the sealed protective shell are provided with sealed joints for threading the steel cable and the electric cable.

[0010] Furthermore, the winch is equipped with a depth encoder; the data processing unit is configured to receive depth signals from the depth encoder, attitude signals from the tilt sensor, and mechanical signals from the pressure sensor and displacement sensor, and to compensate and correct the mechanical signals based on the attitude signals.

[0011] The present invention also provides a method for detecting the thickness of sediment at the bottom of a pile, using the aforementioned detection device, comprising the following steps: S1. Lowering and Attitude Adjustment: Lower the dynamic impact detection system into the pile hole, and adjust the attitude of the device to be horizontal according to the data of the tilt sensor; S2. Sludge surface identification: During the probe lowering process, the electromagnetic hammer is controlled to perform a trial impact; if the peak pressure P detected by the pressure sensor is greater than the first preset threshold and the rebound displacement S detected by the displacement sensor is less than the second preset threshold, it is determined that the probe is in contact with the sludge surface and the current depth is recorded as the sludge surface depth H1. S3. Formal Impact and Data Acquisition: At the depth H1, control the electromagnetic hammer to perform at least one formal impact, and simultaneously acquire and record the peak pressure P and rebound displacement S of each impact. S4. Interface identification and thickness calculation: Based on multiple sets of (P, S) data, draw pressure-displacement relationship curves, identify the inflection points where the slope of the curve changes abruptly, determine the impact event that occurs at the inflection point as the probe touching the bearing layer interface, and record the corresponding depth as the bearing layer interface depth H2; calculate the sediment thickness h according to the formula h=H1-H2.

[0012] Furthermore, in step S1, adjusting the device attitude to horizontal means adjusting the horizontal attitude angle detected by the tilt sensor to a range of no more than ±4°.

[0013] Furthermore, in step S4, if the calculated sediment thickness h is an invalid value, the impact energy of the electromagnetic hammer is automatically adjusted, and steps S3 and S4 are repeated.

[0014] Furthermore, at least three detection points are selected on the bottom plane of the pile, and steps S1 to S4 are repeated to obtain multiple sediment thickness measurements. After removing outliers, the arithmetic mean is calculated as the final detection result.

[0015] (III) Beneficial Effects Compared with the prior art, the present invention has the following beneficial effects: 1. The dynamic impact rebound principle is innovatively applied to the detection of sediment at the bottom of piles. By analyzing the pressure-displacement relationship curve obtained from the formal impact, and utilizing the significant difference in the impact response (curve slope) between the sediment layer and the bearing layer, the objective and accurate identification of the interface is achieved.

[0016] 2. The device has a compact structure and a sealed protective shell design with anti-adhesion and flow guiding functions, making it suitable for the mud environment in pile holes; multi-parameter synchronous acquisition and attitude fusion correction technology effectively eliminates interference from tilting, steel cable tension and other factors, significantly improving detection accuracy and reliability.

[0017] 3. The detection method is highly intelligent, with automatic attitude adjustment, surface recognition, adaptive energy adjustment and multi-point verification functions. It is easy to operate, has high detection efficiency, and reduces reliance on human experience.

[0018] 4. This method is a non-destructive testing method with moderate cost. It can be widely used in the quality control of various types of bored pile construction and has important engineering practical value and promotion prospects. Attached Figure Description

[0019] To more clearly illustrate the technical solutions in the embodiments of the present 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 present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort, wherein: Figure 1This is a schematic diagram of the overall structure of the device of the present invention inside the pile hole.

[0020] Figure 2 This is a schematic diagram of the internal structure of the dynamic impact detection system of the present invention.

[0021] Figure 3 for Figure 2 Bottom view of the impact hammer.

[0022] Figure 4 for Figure 2 Top view of the probe.

[0023] Figure 5 This is an assembly diagram of the impact hammer, return spring, and probe.

[0024] Figure 6 A schematic diagram of the sealed protective shell and its surface spiral guide grooves.

[0025] Figure 7 This is a schematic diagram of the structure of an electromagnetic coil.

[0026] In the diagram: 1. Dynamic impact detection system; 2. Steel cable; 3. Winch; 4. Pile hole; 5. Sediment; 6. Cable; 7. Instrument control box; 8. Data processing unit; 9. Sealed protective shell; 10. Impact hammer; 11. Electromagnetic coil; 12. Return spring; 13. Probe; 14. Pressure sensor; 15. Displacement sensor; 16. Real-time tilt sensor; 17. Buffer pad; 18. Spiral guide channel; 19. Fixing sleeve; 20. Lifting lug; 21. Annular boss; 22. Wire; 23. Iron core; 24. Annular groove; 25. Cylindrical mounting hole. Detailed Implementation

[0027] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0028] The terms "first," "second," etc., used in the specification and claims of this invention are used to distinguish similar objects and not to describe a specific order or sequence. It should be understood that such data can be interchanged where appropriate so that embodiments of the invention can be implemented in orders other than those illustrated or described herein, and the objects distinguished by "first," "second," etc., are generally of the same class and the number of objects is not limited; for example, a first object can be one or more. Furthermore, in the specification and claims, "and / or" indicates at least one of the connected objects, and the character " / " generally indicates that the preceding and following objects are in an "or" relationship.

[0029] like Figure 1 As shown in the figure, the intelligent pile bottom sediment thickness detection device based on impact rebound provided in this embodiment of the invention mainly consists of two parts: a dynamic impact detection system 1 and a ground control and data processing system. The dynamic impact detection system 1 is connected to the ground system via steel cable 2 and cable 6.

[0030] like Figure 2 As shown, the core of the dynamic impact detection system 1 includes an adaptive impact component, a multi-parameter sensing component, and a sealed protective shell 9. It adopts a cylindrical integrated design with an outer diameter of 80-120 mm and a total length of 300-400 mm. The sealed protective shell 9 has rounded transitions at both ends to reduce mud disturbance during lowering.

[0031] The adaptive impact assembly consists of an electromagnetic hammer, a return spring 12, and a probe 13 connected in series coaxially.

[0032] The electromagnetic hammer consists of an electromagnetic coil 11 and an impact hammer 10. The impact hammer 10 is a cylindrical structure, coaxially arranged with the detection system, made of electrical pure iron, with a diameter of 40-60 mm, a length of 80-120 mm, and a weight of 1-2 kg. The electromagnetic coil 11 is formed by winding an iron core 23 with a wire 22, and is driven by a pulse current output from the ground control and data processing system, driving the impact hammer to move axially.

[0033] The return spring 12 is a high-strength spring steel compression spring, coaxially adapted with the electromagnetic hammer and probe 13, and its two ends are respectively welded and fixed to the annular boss 21 at the lower end of the impact hammer 10 (see...). Figure 3 , Figure 5 (as shown) and the annular groove 24 at the upper end of the probe 13 (see) Figure 2 , Figure 5 As shown in the figure, after the impact, the impact hammer 10 can be quickly reset to achieve continuous impact detection.

[0034] The probe 13 is made of hard alloy, with a hemispherical bottom and a spherical diameter of 40-60 mm. Its surface is coated with polytetrafluoroethylene. The main body of the probe 13 is 50-70 mm long, and a cylindrical connecting section is provided at the top for fixing to the return spring 12, ensuring uniform transmission of the impact load. A cylindrical mounting hole 25 is provided at the top of the probe 13 (see...). Figure 4 As shown in the figure, it is used to install pressure sensor 14.

[0035] A multi-parameter sensing component is used to synchronously and accurately acquire mechanical parameters, equipment attitude data, and contact status signals during the impact process. This component includes a pressure sensor 14, an LVDT miniature displacement sensor 15, and a MEMS real-time tilt sensor 16. The pressure sensor 14 is built into the cylindrical mounting hole 25 on the top of the probe 13. It is a piezoelectric pressure sensor that acquires the peak impact load with a range of 0-100kN. When the impact hammer 10 impacts the probe 13 and the probe 13 contacts the sediment 5, the reaction force of the sediment 5 on the probe 13 is transmitted to the pressure sensor 14 through the probe 13 and the impact hammer 10. The "maximum reaction force value" captured by the sensor is the peak impact pressure, directly reflecting the instantaneous bearing capacity of the sediment 5.

[0036] The displacement sensor 15 has a range of 0-50 mm and a sampling frequency of ≥10kHz. The installation method is as follows: an axial installation channel is reserved inside the return spring 12; the fixed end of the sensor is threadedly connected to the mounting base at the center of the protrusion 21 on the lower end face of the impact hammer 14; the moving end is hinged to the connecting section at the center of the upper end face of the probe 13 via a universal joint. When the electromagnetic hammer impacts, it pushes the probe 13 downwards, compressing the spring 12, and the moving end of the sensor moves downwards synchronously with the probe 13. After impact, the sediment 5 rebounds, pushing the probe 13 upwards to reset, and the moving end moves upwards synchronously with the probe 13. The sensor outputs the rebound displacement Sr by detecting the relative displacement change between the fixed end and the moving end.

[0037] The real-time tilt sensor 16 is fixed to the middle of the inner wall of the sealed protective shell 9. It is a MEMS tilt sensor that collects the horizontal attitude angle of the detection system and can feed back the attitude data to the data processing unit in real time. The intelligent tilt correction algorithm automatically completes the mechanical signal deviation compensation and vertical depth calibration.

[0038] like Figure 6As shown, the sealed protective shell 9 is a 316L stainless steel cylindrical body with a wall thickness of 5-8 mm. Brass sealing joints are installed at both ends of the shell for threading and fixing the steel cable 2 and the cable 6, respectively. The outer surface of the sealed protective shell 9 is machined with a spiral guide groove 18, and the inner wall is lined with a buffer pad layer 17. The buffer pad layer 17 is a nitrile rubber buffer pad, which reduces vibration interference of the components during impact and ensures the stability of the sensing data. The spiral guide groove 18 has a pitch of 20-30 mm and a groove depth of 1-2 mm, which reduces mud resistance during lowering and prevents the shell from getting stuck due to mud adsorption.

[0039] The outer surface of the sealed protective shell 9 is coated with polytetrafluoroethylene to further reduce the amount of mud adhering.

[0040] The sealed protective shell 9 has a fixed sleeve 19 inside, and the electromagnetic hammer and probe 13 are inside the fixed sleeve 19, so that the movement trajectory is kept on the same axis.

[0041] The sealed protective housing 9 has brass sealing connectors (not labeled in the figure) at both ends for sealing the inserted steel cable 2 and cable 6. The structure of the electromagnetic coil 11 is as follows. Figure 7 As shown, it is constructed by winding wire 22 around iron core 23.

[0042] The ground control and data processing system, serving as the control center and data processing core of the device, mainly includes steel cable 2, cable 6, winch 3, instrument control box 7, and data processing unit 8. The steel cable 2 is made of high-strength galvanized steel wire rope, with one end fixed to the top lug 20 of the sealed protective shell 9 of the dynamic impact detection system via a shackle, and the other end wound around the winch 3 to control the lowering depth of the detection system.

[0043] The cable 6 is a waterproof and wear-resistant shielded cable with an outer diameter of 6-8 mm. It is arranged in parallel with the steel cable 2. One end passes through the sealed joint and is connected to the multi-parameter sensing component and electromagnetic hammer. The other end is connected to the instrument control box 7 to realize the transmission of control signals and the feedback of sensing data.

[0044] The winch 3 is equipped with a high-precision absolute depth encoder and an electromagnetic braking device, which can precisely control the lowering speed and stopping position of the detection system, ensuring that the probe accurately contacts the surface of the sediment 5 at the bottom of the pile. The instrument control box 7 has a built-in power supply module, an electromagnetic hammer drive module, and a signal conditioning module, which outputs a stable DC power supply to achieve precise control of impact energy and impact frequency. The data processing unit 8 consists of a computer, dedicated software, and a data storage module.

[0045] The detection method of this invention is operated according to the following steps: Device installation and commissioning: After the bored pile is completed and before the concrete is poured, connect and fix the dynamic impact detection system to the steel cable 2 and the cable 6, check the sealing performance of the protective shell 9, the signal transmission stability of the sensing components, and the impact reset performance of the electromagnetic hammer; start the system through the instrument control box 7, set parameters such as the trial impact energy and the formal impact energy, and complete the preparation work.

[0046] After preparation, the winch 3 is operated to lower the dynamic impact detection system 1 into the pile hole 4. Based on the lowering length fed back by the depth encoder and the drilling rod depth record of the pile hole, the probe 13 is sent to the predetermined position at the bottom of the pile (above the estimated upper surface of the sediment), and the lowering is stopped. The data processing unit 8 monitors the data of the tilt sensor 16 in real time. If the horizontal attitude angle of the detection system exceeds ±4°, the attitude of the device is adjusted by fine-tuning the winch 3 or gently shaking the steel cable 2 until the attitude angle meets the requirements.

[0047] During the lowering process, a trial impact mode is initiated. A small current is applied to the electromagnetic coil 11 to drive the impact hammer 10 downwards, and the energy is transferred to the probe 13 via the return spring 12. The pressure sensor 14 and displacement sensor 15 collect the peak pressure P and rebound displacement S, respectively. If P is greater than a set threshold and S is less than a set threshold, it is determined that the probe 13 has contacted the surface of the sediment 5, and the vertical depth measured and corrected by the depth encoder at this point is recorded as H1.

[0048] Subsequently, the system switched to the formal impact mode, impacting with higher energy. The peak pressure P and rebound displacement S of each impact were simultaneously collected and recorded. Multiple sets of (P, S) data were plotted as pressure-displacement curves. Due to the loose sediment layer and low rebound modulus, the initial segment of the curve was relatively flat; when the impact penetrated the sediment layer and reached the underlying hard bearing layer, the rebound modulus increased sharply, causing a sudden change in the curve slope and forming a distinct inflection point. The software automatically identified this inflection point and recorded the corresponding depth as the bearing layer interface depth H2. Sediment thickness h = H1 - H2.

[0049] If h < 0 or h > 200 mm (the maximum limit specified in the standard), it is determined that the impact energy is insufficient or the interface identification is abnormal. The calculated result h is invalid, and the system automatically increases the impact energy and re-measures.

[0050] To ensure the reliability of the results, at least three evenly distributed test points at the bottom of the pile are selected to repeat the above measurement to obtain multiple sediment thickness data. After removing outliers, the average value is taken as the final test result to ensure the accuracy of the test. If the thickness exceeds the specification limit, it can be reported to the construction unit for sediment cleaning. After cleaning, the above test process is repeated until the specification requirements are met.

[0051] It should be noted that, in this document, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or apparatus. Unless otherwise specified, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the process, method, article, or apparatus that includes that element.

[0052] Furthermore, it should be noted that the scope of the methods and systems in the embodiments of the present invention is not limited to performing functions in the order shown or discussed, but may also include performing functions substantially simultaneously or in the reverse order, depending on the functions involved. For example, the described methods may be performed in a different order than described, and various steps may be added, omitted, or combined. In addition, features described with reference to certain examples may be combined in other examples.

[0053] The embodiments of the present invention have been described above with reference to the accompanying drawings. However, 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 without departing from the spirit and scope of the claims, and all of these forms are within the protection scope of the present invention.

Claims

1. An intelligent detection device for pile bottom sediment thickness based on impact rebound, characterized in that, Includes a dynamic impact detection system and a ground control and data processing system; The dynamic impact detection system is connected to the winch in the ground control and data processing system via a steel cable, and is electrically connected to the instrument control box in the ground control and data processing system via a cable. The dynamic impact detection system includes a sealed protective housing, and an adaptive impact component and a multi-parameter sensing component disposed within the sealed protective housing; The adaptive impact assembly includes an electromagnetic hammer, a return spring, and a probe arranged coaxially, with the electromagnetic hammer connected to the probe via the return spring. The multi-parameter sensing component includes a pressure sensor for detecting impact pressure, a displacement sensor for detecting rebound displacement, and a tilt sensor for detecting attitude. The ground control and data processing system includes the winch, the instrument control box, and the data processing unit, which is communicatively connected to the instrument control box.

2. The intelligent detection device for pile bottom sediment thickness based on impact rebound according to claim 1, characterized in that, The electromagnetic hammer includes an electromagnetic coil and an impact hammer; the return spring is a cylindrical helical compression spring, with its two ends fixed to the bottom of the impact hammer and the top of the probe, respectively; the bottom of the probe is a hemispherical structure with a non-stick coating sprayed on its surface.

3. The intelligent detection device for pile bottom sediment thickness based on impact rebound according to claim 2, characterized in that, The pressure sensor is built into the cylindrical mounting hole at the top of the probe; the displacement sensor is a differential transformer type displacement sensor, with its fixed end connected to the impact hammer and its moving end connected to the probe through a directional connector, and the sensing rod of the displacement sensor passes through the inner space of the return spring.

4. The intelligent detection device for pile bottom sediment thickness based on impact rebound according to claim 1, characterized in that, The sealed protective shell is a cylindrical body with a spiral guide groove on its outer surface and a buffer pad layer on its inner wall; both ends of the sealed protective shell are provided with sealed joints for threading the steel cable and the electric cable.

5. The intelligent detection device for pile bottom sediment thickness based on impact rebound according to claim 1, characterized in that, The winch is equipped with a depth encoder; the data processing unit is configured to receive a depth signal from the depth encoder, an attitude signal from the tilt sensor, and a mechanical signal from the pressure sensor and the displacement sensor, and to compensate and correct the mechanical signal based on the attitude signal.

6. A method for detecting the thickness of sediment at the bottom of a pile, characterized in that, The intelligent detection device for pile bottom sediment thickness based on impact rebound as described in any one of claims 1 to 5 includes the following steps: S1. Lowering and Attitude Adjustment: Lower the dynamic impact detection system into the pile hole, and adjust the attitude of the device to be horizontal according to the data of the tilt sensor; S2. Sludge surface identification: During the probe lowering process, the electromagnetic hammer is controlled to perform a trial impact; if the peak pressure P detected by the pressure sensor is greater than the first preset threshold and the rebound displacement S detected by the displacement sensor is less than the second preset threshold, it is determined that the probe is in contact with the sludge surface and the current depth is recorded as the sludge surface depth H1. S3. Formal Impact and Data Acquisition: At the depth H1, control the electromagnetic hammer to perform at least one formal impact, and simultaneously acquire and record the peak pressure P and rebound displacement S of each impact. S4. Interface identification and thickness calculation: Based on multiple sets of (P, S) data, draw pressure-displacement relationship curves, identify inflection points where the slope of the curve changes abruptly, determine the impact event that occurs at the inflection point as the probe touching the bearing layer interface, and record the corresponding depth as the bearing layer interface depth H2; calculate the sediment thickness h according to the formula h=H1-H2.

7. The method according to claim 6, characterized in that, In step S1, adjusting the device attitude to horizontal means adjusting the horizontal attitude angle detected by the tilt sensor to a range of no more than ±4°.

8. The method according to claim 6, characterized in that, In step S4, if the calculated sediment thickness h is an invalid value, the impact energy of the electromagnetic hammer is automatically adjusted, and steps S3 and S4 are repeated.

9. The method according to claim 6, characterized in that, Select at least three detection points on the bottom plane of the pile, repeat steps S1 to S4 to obtain multiple sediment thickness measurements, remove outliers and calculate the arithmetic mean as the final detection result.

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