Optical fiber detection sensor for thickness of sediment at bottom of drill hole

Abstract

The invention provides a drill hole bottom sediment thickness optical fiber detection sensor, and belongs to the field of measuring equipment. The equipment comprises a plurality of optical fiber detection devices, a first fixed disc, a static sounding device, a second fixed disc, a reading instrument and a control optical fiber demodulator, wherein the optical fiber detection devices comprise strain optical fibers. According to the equipment, the sediment layer and the supporting layer are judged through the static sounding device, the sediment thickness is detected through the strain optical fiber, and the judgment precision and the detection precision are high. In addition, the sediment thickness can be judged through the optical fiber demodulator and the reading instrument only by putting the equipment into the pile hole, and the equipment can be repeatedly used, is simple to operate and is low in cost.

Description

Technical Field

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

[0002] During the construction of pile foundation projects, quicksand and gravel that fall during drilling will cause the deposition of hole-forming slag. During the lowering of the steel cage, the collapse of the hole will further increase the amount of sediment. The strength of the sediment is low and the compressibility is high. 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 during the actual load-bearing stage, causing shear damage and reducing the bearing capacity of the pile. Therefore, in actual construction, the thickness of the sediment must be measured, but it is impossible to manually measure the thickness of the sediment at the bottom of the pile. Therefore, many devices for detecting the thickness of the sediment have emerged.

[0003] For example, Chinese patent document CN109518739B discloses a sediment thickness detector that uses the state of the contactor when it is in contact with 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 is less practical 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, the device is a manual reading device, which will produce certain reading errors.

[0005] Chinese patent document CN215261552U discloses a sediment thickness detector, which 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, and the device needs to be pulled out before it can be judged.

[0007] Chinese patent document CN111677022B discloses a sediment thickness detection device before cast-in-place pile construction, which measures sediment thickness through threaded rods and drill bits, torque mechanisms, threaded rods, polished rods, drill bits, etc. However, the structure needs to be assembled when in use, which delays progress and there are errors in manual readings.

[0008] The above list is only part of the detection equipment. At present, the methods for measuring sediment thickness are mainly divided into hammer equipment, ultrasonic equipment and manual sampling equipment. The hammer equipment determines the top surface position of the sediment by the operator's feel. In the specific operation, the human factor has a greater impact and the measurement accuracy is poor. The ultrasonic equipment uses sound wave conversion to measure the sediment thickness. The measurement result is relatively accurate, but the cost of using ultrasonic equipment is too high and not suitable for large-scale use. The manual sampling equipment is to hang the sampling box to the bottom of the hole after the hole is cleaned, and measure the thickness of the slag settled in the box before pouring. This method is cumbersome to operate and has a large number of uncertainties.

[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 detection sensor for 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 prior art, and the purpose is to achieve accurate detection of sediment thickness during pile foundation construction in view of the defects of the prior art.

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

[0012] A fiber optic detection sensor for sediment thickness at the bottom of a borehole, comprising 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 is parallel to the second fixed disk and both are coaxial with the static penetration device; n fiber optic detection through holes are evenly distributed on the first fixed disk, and a static penetration through hole is located at the center of the first fixed disk; a through hole is opened at the center of the second fixed disk;

[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 reading instrument is connected to the three data lines respectively, and the three data lines pass through the three line protection sleeves from top to bottom and are connected to the inside of the static penetration device;

[0014] The optical fiber detection device includes a strain optical fiber, two wire protection sleeves, a bracket, a protection tube, a spring and a stainless steel column; the protection tube is a cylindrical structure with two capped sides, and its lower part 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-type, consisting of a main board, an upper horizontal plate and a middle horizontal plate in a vertical direction, and is fixed in the protection tube by welding the upper horizontal plate to the inner wall of the protection 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 protection tube and is screwed to the second fixed plate; the strain optical fiber passes through a wire protection sleeve, a protection 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, the first fixed plate is also evenly distributed with n wire holes, 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 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 at the lower part of the second fixed 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 sensor for detecting the thickness of sediment at the bottom of a borehole, and uses a static penetration device to determine the sediment layer and the bearing layer with high determination accuracy.

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

[0022] (3) The 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. 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 the device share a strain optical fiber, which reduces the error caused by optical fiber fusion splicing 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 1It is a schematic 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 It is a schematic diagram of the structure of a static penetration device in an embodiment of the present invention.

[0027] Figure 4 Schematic diagram of the structure of the first fixed disk 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. optical fiber 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. optical fiber 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 is described in detail below with reference to the accompanying drawings and embodiments.

[0032] Figure 1 is a schematic diagram of the structure of an optical fiber detection sensor in an embodiment of the present invention, Figure 2 is a schematic structural diagram of an optical fiber detection device in an embodiment of the present invention, Figure 3 is a schematic structural diagram of a static penetration device in an embodiment of the present invention, Figure 4 is a schematic diagram of the structure of the first fixed disk in an embodiment of the present invention, Figure 5 is a 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 drawings, the present invention provides a fiber optic detection sensor for 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 is parallel to the second fixed disk 6, and both are coaxial with the static penetration device 5. The first fixed disk 2 is evenly distributed with n fiber optic detection through holes 12, a static penetration hole 13 located at the center of the first fixed disk 2, and a through hole 19 is opened at the center of the second fixed disk 6;

[0034] 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 plate 2 and the second fixed plate 6 in sequence through the static penetration hole 13 and the through hole 19, and is fixed to the first fixed plate 2 by welding. The reading instrument 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 inside of the static penetration 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, the through hole 19 is slightly larger than the static penetration hole 13, and the three wire protection sleeves 7 are kept in parallel. The CLD-3 static penetration instrument produced by Rugao Engineering Survey Machinery Factory was selected. The static penetration instrument has a simple structure, is lightweight, and is easy to carry. It is used for soft soil, general clay soil, and loose to medium-dense sand layers. It is currently the most widely used lightweight static penetration device in China. In this static penetration instrument, the three data lines are used to measure pore pressure, end resistance, and friction resistance respectively.

[0037] The optical fiber detection device 1 includes a strain optical fiber 4, two wire protective 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 sides, and its lower part 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 main board 23, an upper horizontal plate 21 and a middle horizontal plate 22 in a vertical direction, and is fixed in 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, and 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 protective sleeve 7, a protective tube 9 and another wire protective sleeve 7 from top to bottom in turn to reach the outside of the optical fiber detection device 1, and when passing through the main board 23, it is attached to the side of the main board 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 formed on the second fixing plate 6 , and an external thread corresponding to the threaded hole 20 is formed 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 fixed plate 2, and the n optical fiber detection devices 1 share one 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 the thickness of sediment 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) is parallel to the second fixed disk (6) and both are coaxial with the static penetration device (5); the first fixed disk (2) is evenly distributed with n optical fiber detection through holes (12) and a static penetration through hole (13) located at the center of the first fixed disk (2); and the second fixed disk (6) is provided with a through hole (19) at the center; 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 plate (2) and the second fixed plate (6) in sequence through the static penetration hole (13) and the through hole (19), and is fixed to the first fixed plate (2) by welding. The reading instrument 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 inside 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 sides, the lower part of which passes through the first fixed plate (2) through the optical fiber detection through hole (12) and is fixedly connected to the first fixed plate (2) by welding; the bracket (8) is an inverted F-shaped structure, consisting of a main board (23) in a vertical direction, an upper horizontal board (21) and a middle horizontal board (22), and is connected to the protection tube (9) through the upper horizontal board (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 sediment thickness at the bottom of a borehole according to claim 1, characterized in that: The first fixing plate (2) is also provided with n wire-through holes (14) evenly distributed thereon, 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-through holes (14), and the tail of the strain optical fiber (4) is free.

3. The optical fiber detection sensor for sediment thickness at the bottom of a borehole 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 means of a cable tie (3).

4. The optical fiber detection sensor for sediment thickness 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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