Fiber optic detection sensor for sediment thickness at the bottom of drilling hole

Abstract

The present invention provides a fiber optic detection sensor for sediment thickness at the bottom of a borehole, belonging to the field of measuring equipment. The device includes multiple fiber optic detection devices, a first fixed disk, a static probing device, a second fixed disk, a reader, and a controlled fiber optic demodulator, wherein the fiber optic detection device includes a strain fiber. The device of the present invention uses the static probing device to determine the sediment layer and the bearing layer, and uses the strain fiber to detect the sediment thickness, with high judgment and detection accuracy. In addition, the present invention only requires the device to be placed in the pile hole, and the fiber optic demodulator and reader can be used to determine the sediment thickness. The device is reusable, simple to operate, and low in cost.

Description

Technical Field

[0001] The present invention relates to the field of measuring equipment, in particular to an optical fiber sensor for detecting the thickness of sediment at the bottom of a borehole. Background Art

[0002] During the construction of pile foundation projects, quicksand and gravel falling during drilling will cause the deposition of drilling slag. During the lowering of the steel cage, the collapse of the hole will further increase the amount of sediment. The sediment has low strength and high compressibility. If the sediment at the bottom of the pile is too thick, the sediment may penetrate into the pile end during the static load test or the actual load-bearing stage, causing shear damage and reducing the bearing capacity of the pile. Therefore, in actual construction, the sediment thickness must be measured. However, it is impossible to manually measure the sediment thickness at the bottom of the pile. Therefore, many devices for detecting the sediment thickness have emerged.

[0003] For example, Chinese patent document CN109518739B discloses a sediment thickness detector that uses the contact state between the contactor and the concrete layer and the sediment layer to display different images, and analyzes the images to determine the sediment thickness. However, the device requires signal transmission and has poor practicality in remote mountainous areas.

[0004] Chinese patent document CN117168270A discloses a sediment thickness detection tool, which inserts a vertical rod into the sediment layer and reads the scale on the surface of the vertical rod to determine the sediment thickness; however, this device uses manual reading, which may result in certain reading errors.

[0005] Chinese patent document CN215261552U discloses a sediment thickness detector that detects sediment thickness by hammering a pull rod so that the conical head of the pull rod hits the bottom of the sediment and reading the scale of the pull rod sinking up and down. However, this device requires manual hammering and is prone to human error.

[0006] Chinese patent document CN118309118A discloses a pile hole sediment thickness detection device, which determines the sediment thickness by setting a measuring tube, a counterweight tube, a groove group and a scale line. The device needs to be pulled out before it can be judged.

[0007] Chinese patent document CN111677022B discloses a device for measuring sediment thickness before cast-in-place pile construction. The device measures sediment thickness using a threaded rod and drill bit, a torque mechanism, a threaded rod, a polished rod, and a drill bit. However, this device requires assembly, which delays progress and introduces errors in manual readings.

[0008] The above list only includes some of the detection equipment. Currently, the main methods for measuring sediment thickness are hammering, ultrasonic, and manual sampling. Hammering relies on the operator's feel to determine the top surface of the sediment. This is subject to significant human influence during operation, resulting in poor measurement accuracy. Ultrasonic equipment uses sound wave conversion to measure sediment thickness, providing relatively accurate results. However, its high cost makes it unsuitable for large-scale use. Manual sampling involves hoisting a sampling box to the bottom of the hole after hole cleaning and measuring the thickness of the sediment deposited within the box before pouring. This method is cumbersome and carries significant uncertainty.

[0009] In summary, existing sediment detection equipment has problems such as low accuracy, high cost, and complicated operation. Based on this, the present invention designs a fiber optic sensor for detecting sediment thickness at the bottom of a borehole. Summary of the Invention

[0010] The technical problem to be solved by the present invention is the defects of the existing technology. The purpose is to achieve accurate detection of sediment thickness during pile foundation construction in view of the defects of the existing technology.

[0011] In order to achieve the above-mentioned purpose, the present invention intends to adopt the following technical solutions.

[0012] A fiber optic sensor for detecting sediment thickness at the bottom of a borehole comprises n fiber optic detection devices, a first fixed disk, a static penetration device, a second fixed disk, a reader, and a fiber optic demodulator; the first fixed disk and the second fixed disk are parallel and coaxial with the static penetration device; the first fixed disk has n fiber optic detection through-holes evenly distributed, and a static penetration through-hole located at the center of the first fixed disk; the second fixed disk has a through-hole at the center;

[0013] The external shape of the static penetration device is cylindrical, and its tail end is conical. The static penetration device passes through the first fixed plate and the second fixed plate in sequence through the static penetration hole and the through hole, and is fixed to the first fixed plate by welding. The reader is connected to three data lines respectively, and the three data lines pass through three wire protection sleeves from top to bottom and enter the interior of the static penetration device.

[0014] The optical fiber detection device includes a strain optical fiber, two wire protection sleeves, a bracket, a protective tube, a spring and a stainless steel column; the protective tube is a cylindrical structure with two capped sides, the lower part of which passes through the first fixed plate through the optical fiber detection through hole and is fixed to the first fixed plate by welding; the bracket is an inverted F-shape, consisting of a vertical main board, an upper horizontal plate and a middle horizontal plate, and is fixed in the protective tube by welding the upper horizontal plate to the inner wall of the protective tube; the upper end of the spring is connected to the middle horizontal plate, and the lower end is connected to the top of the stainless steel cylinder, and the stainless steel cylinder vertically passes through the bottom of the protective tube and is screwed to the second fixed plate; the strain optical fiber passes through a wire protection sleeve, a protective tube and another wire protection sleeve from top to bottom in turn to reach the outside of the optical fiber detection device, and when passing through the main board, it is adhered to the side of the main board facing away from the two horizontal plates;

[0015] The optical fiber demodulator is connected to the strain optical fiber.

[0016] Preferably, n wire-through holes are evenly distributed on the first fixed plate, and the n optical fiber detection devices share one strain optical fiber. Specifically, the head of the strain optical fiber is connected to the optical fiber demodulator, and passes through the n optical fiber detection devices in sequence through the n wire-through holes, and the tail of the strain optical fiber is free.

[0017] Preferably, when the strain optical fiber passes through each optical fiber detection device and reaches the outside thereof, it is fixed to the corresponding stainless steel cylinder by a cable tie.

[0018] Preferably, the length of the static penetration device located below the second fixing plate is at least greater than 2 centimeters.

[0019] Compared with the prior art, the present invention has the following beneficial effects:

[0020] (1) The present invention designs an optical fiber detection sensor for the thickness of sediment at the bottom of a borehole, which determines the sediment layer and the bearing layer through a static penetration device with high determination accuracy.

[0021] (2) This device calculates the sediment thickness by the wavelength change of the optical fiber, and has high detection accuracy.

[0022] (3) This device only needs to be lowered to the bottom of the pile hole, and the time of reaching the bearing layer position is determined by the data of the reading instrument connected to the static penetration device, and the thickness of the sediment is determined by the wavelength change of the optical fiber demodulator when reaching the bearing layer. The device is reusable, simple to operate, and low in cost.

[0023] (4) The n optical fiber detection devices of this device share a strain optical fiber, which reduces the error caused by optical fiber fusion and improves the test accuracy; it reduces the equipment such as optical fiber fusion joints and protective covers, thereby reducing the test cost. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1Schematic diagram of the structure of the optical fiber detection sensor in an embodiment of the present invention.

[0025] Figure 2 Schematic diagram of the structure of an optical fiber detection device in an embodiment of the present invention.

[0026] Figure 3 Schematic diagram of the structure of a static penetration device in an embodiment of the present invention.

[0027] Figure 4 Schematic diagram of the first fixed disk structure in an embodiment of the present invention.

[0028] Figure 5 Schematic diagram of the structure of the second fixed disk in an embodiment of the present invention.

[0029] Figure 6 Schematic diagram of the support structure in an embodiment of the present invention.

[0030] Figure numerals: 1. Fiber optic detection device; 2. First fixed plate; 3. Cable tie; 4. Strain optical fiber; 5. Static sounding device; 6. Second fixed plate; 7. Wire protection cover; 8. Bracket; 9. Protective tube; 10. Spring; 11. Stainless steel column; 12. Fiber optic detection through hole; 13. Static sounding through hole; 14. Wire hole; 15. Data cable; 19. Through hole; 20. Threaded hole; 21. Upper horizontal plate; 22. Middle horizontal plate; 23. Main board. DETAILED DESCRIPTION

[0031] The present invention will be described in detail below with reference to the accompanying drawings and embodiments.

[0032] Figure 1 FIG. 1 is a schematic structural diagram of an optical fiber detection sensor in an embodiment of the present invention. Figure 2 FIG. 1 is a structural diagram of an optical fiber detection device in an embodiment of the present invention. Figure 3 FIG. 1 is a structural diagram of a static penetration device in an embodiment of the present invention. Figure 4 Schematic diagram of the structure of the first fixed disk in an embodiment of the present invention, Figure 5 Schematic diagram of the structure of the second fixed disk in an embodiment of the present invention, Figure 6 Schematic diagram of the support structure in an embodiment of the present invention.

[0033] As can be seen from the above figures, the present invention provides a fiber optic sensor for detecting sediment thickness at the bottom of a borehole, comprising n fiber optic detection devices 1, a first fixed disk 2, a static penetration device 5, a second fixed disk 6, a reader, and a fiber optic demodulator. The first fixed disk 2 and the second fixed disk 6 are parallel and coaxial with the static penetration device 5. The first fixed disk 2 has n fiber optic detection through-holes 12 evenly distributed, a static penetration through-hole 13 located at the center of the first fixed disk 2, and a through-hole 19 located at the center of the second fixed disk 6.

[0034] The CPT device 5 is cylindrical in shape with a conical tail. It passes through the first and second mounting plates 2 and 6, respectively, via the CPT penetration hole 13 and the through hole 19, and is welded to the first mounting plate 2. The reader is connected to three data cables 15, which pass through three cable protection sleeves 7 from top to bottom and into the interior of the CPT device 5.

[0035] In this embodiment, the length of the static penetration device 5 located below the second fixing plate 6 is at least greater than 2 centimeters.

[0036] In this embodiment, through-hole 19 is slightly larger than the static penetration hole 13, and the three wire protection sleeves 7 are maintained in parallel. The CLD-3 static penetration tester, manufactured by Rugao Engineering Survey Machinery Factory, was selected. This tester features a simple, lightweight structure, making it easy to carry. It is suitable for soft soils, general clayey soils, and loose to medium-dense sand layers. It is currently the most widely used lightweight static penetration tester in China. In this tester, the three data lines are used to measure pore pressure, end resistance, and frictional resistance, respectively.

[0037] The optical fiber detection device 1 includes a strain fiber 4, two wire protection sleeves 7, a bracket 8, a protective tube 9, a spring 10, and a stainless steel column 11. The protective tube 9 is a cylindrical structure with two capped ends. Its lower portion passes through the first fixed plate 2 via a fiber detection through hole 12 and is fixed to the first fixed plate 2 by welding. The bracket 8 is an inverted F-shaped structure, consisting of a vertical main plate 23, an upper horizontal plate 21, and a middle horizontal plate 22. It is fixed to the protective tube 9 by welding the upper horizontal plate 21 to the inner wall of the protective tube 9. The upper end of the spring 10 is connected to the middle horizontal plate 22, and the lower end is connected to the top of the stainless steel cylinder 11. The stainless steel cylinder 11 passes vertically through the bottom of the protective tube 9 and is screwed to the second fixed plate 6. The strain fiber 4 passes through a wire protection sleeve 7, a protective tube 9, and another wire protection sleeve 7 from top to bottom to reach the exterior of the optical fiber detection device 1. When passing through the main plate 23, it is adhered to the side of the main plate 23 facing away from the two horizontal plates.

[0038] The optical fiber demodulator is connected to the strain optical fiber 4 .

[0039] In this embodiment, a threaded hole 20 is further provided on the second fixing plate 6 , and an external thread corresponding to the threaded hole 20 is provided at the tail of the stainless steel cylinder 11 for threaded connection between the stainless steel cylinder 11 and the second fixing plate 6 .

[0040] In this embodiment, n wire holes 14 are evenly distributed on the first fixing plate 2, and the n optical fiber detection devices 1 share a strain optical fiber 4. Specifically, the head of the strain optical fiber 4 is connected to the optical fiber demodulator and passes through the n optical fiber detection devices 1 in sequence through the n wire holes 14, and the tail of the strain optical fiber 4 is free.

[0041] In this embodiment, when the strain optical fiber 4 passes through each optical fiber detection device 1 and reaches the outside thereof, it is fixed to the corresponding stainless steel cylinder 11 by a cable tie 3 .

Claims

1. A fiber optic sensor for detecting sediment thickness at the bottom of a borehole, characterized in that: The invention comprises n optical fiber detection devices (1), a first fixed disk (2), a static penetration device (5), a second fixed disk (6), a reader and an optical fiber demodulator; the first fixed disk (2) and the second fixed disk (6) are parallel and coaxial with the static penetration device (5); n optical fiber detection through holes (12) are evenly distributed on the first fixed disk (2) and a static penetration through hole (13) is located at the center of the first fixed disk (2); a through hole (19) is opened at the center of the second fixed disk (6); The external shape of the static penetration device (5) is cylindrical, and its tail end is conical. The static penetration device (5) passes through the first fixed disk (2) and the second fixed disk (6) in sequence through the static penetration hole (13) and the through hole (19), and is fixed to the first fixed disk (2) by welding. The reader is connected to three data lines (15) respectively, and the three data lines (15) pass through three line protection sleeves (7) from top to bottom and are connected to the interior of the static penetration device (5). The optical fiber detection device (1) comprises a strain optical fiber (4), two wire protection sleeves (7), a bracket (8), a protection tube (9), a spring (10) and a stainless steel column (11); the protection tube (9) is a cylindrical structure with two capped ends, the lower portion of which passes through the first fixed plate (2) through the optical fiber detection through hole (12) and is fixed to the first fixed plate (2) by welding; the bracket (8) is an inverted F-shaped structure, consisting of a vertical main plate (23), an upper horizontal plate (21) and a middle horizontal plate (22), and is connected to the protection tube (9) through the upper horizontal plate (21). ) is welded to the inner wall of the protective tube (9); the upper end of the spring (10) is connected to the middle horizontal plate (22), and the lower end is connected to the top of the stainless steel cylinder (11); the stainless steel cylinder (11) vertically passes through the bottom of the protective tube (9) and is screwed to the second fixed plate (6); the strain optical fiber (4) passes through a wire protection sleeve (7), the protective tube (9) and another wire protection sleeve (7) from top to bottom in sequence to reach the outside of the optical fiber detection device (1), and when passing through the main board (23), it is adhered to the side of the main board (23) facing away from the two horizontal plates; The optical fiber demodulator is connected to the strain optical fiber (4).

2. The optical fiber detection sensor for drilling bottom sediment thickness according to claim 1, characterized in that: The first fixed plate (2) is also provided with n wire holes (14) evenly distributed thereon. The n optical fiber detection devices (1) share a strain optical fiber (4). Specifically, the head of the strain optical fiber (4) is connected to the optical fiber demodulator and passes through the n optical fiber detection devices (1) in sequence through the n wire holes (14). The tail of the strain optical fiber (4) is free.

3. The optical fiber detection sensor for drilling bottom sediment thickness according to claim 1, characterized in that: When the strain optical fiber (4) passes through each optical fiber detection device (1) and reaches the outside thereof, it is fixed to the corresponding stainless steel cylinder (11) by a cable tie (3).

4. The optical fiber sensor for detecting the thickness of sediment at the bottom of a borehole according to claim 1, characterized in that: The length of the static penetration device (5) located below the second fixing plate (6) is at least greater than 2 centimeters.

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