A detecting device and method for the thickness of sediment at the bottom of cast-in-place pile holes

Abstract

The present invention relates to the technical field of underground engineering, and specifically discloses a detection device and method for the thickness of sediment at the bottom of a cast-in-place pile hole, including a measuring cake, and a limiting tube is arranged at the top end of the measuring cake; a measuring rod assembly, the measuring rod assembly includes a measuring needle, the measuring needle is slidably installed on the inner wall of the limiting tube, a limiting sleeve is installed at the top end of the measuring needle, a support rod is installed at the top end of the limiting sleeve, and a connecting ring is fixedly installed at the top end of the support rod, and the connecting ring is used to connect a steel wire rope; a limiting box, a plurality of variable-diameter square boxes are fixedly installed on the opposite outer walls of the limiting box, and a first limiting plate is installed through and slidably between the adjacent side walls of the variable-diameter square box and the limiting box. The present invention has a self-weight pressing type measuring needle, eliminating the need for a power device, reducing production costs, having a counterweight regulation function, being highly adaptable to the sediment at the bottom of the pile hole, and improving the stability of the detection device.

Description

Technical Field

[0001] The present invention relates to the technical field of underground engineering, and particularly relates to a detection device and method for the thickness of sediment at the bottom of a cast-in-place pile hole. Background Art

[0002] The sediment at the bottom of a cast-in-place pile hole refers to the sediment left during the drilling and cleaning process, which is not carried away by the circulating mud and is generally coarser particles. The sediment thickness is the height of the sediment layer. The existence of sediment greatly affects the compressive bearing capacity of the cast-in-place concrete pile or causes the settlement of the building to exceed the design requirements. Therefore, the construction and inspection specifications of cast-in-place piles have strict regulations on the sediment thickness. Generally, the sediment thickness should not exceed 50 - 200 mm, and the detection accuracy is less than 10 mm.

[0003] The sounding weight method, the sounding cone method, and the cake and needle sounding method have differences. In the sounding weight method, the sounding weight is lowered to the bottom of the hole through a sounding rope, and the position of the top surface of the sediment is detected by hand feeling. Then, based on the hole depth measured during drilling, the depth from the top surface of the sediment to the hole opening is subtracted from the hole depth to obtain the sediment thickness, and its measurement accuracy is limited. The cake and needle sounding method measures the position of the top surface of the sediment through a cake and the position from the cake to the bottom of the hole through a needle, and the depth difference between the two is used to obtain the sediment thickness. The depth of the measured pile hole can reach dozens of meters to hundreds of meters. Since it is a two-time measurement and the distance is measured through a sounding rope, affected by the tension of the sounding rope and the cumulative error of the two-time measurement, the final measurement accuracy of the sediment thickness is limited, and the measurement time is long.

[0004] Currently, there is a device that combines a cake and a needle by using electromechanics. After the cake reaches the top surface of the sediment, the upper host sends an instruction to press the needle into the sediment through a power device. Although the pressing depth of the needle, that is, the sediment thickness, can be automatically measured, the equipment cost of the power device for pressing the needle is relatively high, and the components of the power device are easily damaged by vibration and impact. Summary of the Invention

[0005] To solve the above problems existing in the prior art, the present invention provides a detection device and method for the thickness of sediment at the bottom of a cast-in-place pile hole, which can solve the problems raised in the above background art.

[0006] The object of the present invention can be achieved by the following technical solutions:

[0007] A detection device for the thickness of sediment at the bottom of a cast-in-place pile hole, comprising:

[0008] A cake, with a limit tube provided at the top end of the cake;

[0009] Probe assembly, the probe assembly includes a probe needle, the probe needle is slidably installed on the inner wall of the limit tube, a limit sleeve is installed at the top end of the probe needle, a support rod is installed at the top end of the limit sleeve, and a connecting ring is fixedly installed at the top end of the support rod. The connecting ring is used to connect the steel wire rope;

[0010] Limit box, a plurality of variable-diameter square boxes are fixedly installed on the opposite outer walls of the limit box. A first limit plate is installed through and slidably between the adjacent side walls of the variable-diameter square box and the limit box. One end of the first limit plate located in the variable-diameter square box is fixedly installed with a U-shaped frame, and a magnetic attraction block is fixedly installed on the inner wall of the U-shaped frame. A bistable electromagnet is arranged on the inner wall of the variable-diameter square box. There is a distance between the bistable electromagnet and the magnetic attraction block. Two first springs are arranged between the end of the magnetic attraction block close to the bistable electromagnet and the inner wall of the variable-diameter square box. Electric control components are arranged on both opposite sides of the probe assembly;

[0011] Support assembly, the support assembly includes four limit rods, the limit rods are fixedly installed on the top end of the measuring cake, the limit rods are installed through and slidably connected with the limit box, a round plate is arranged at the top end of the limit rods, a damping layer is arranged on the outer wall of the limit rods, and an elastic support structure is arranged between the bottom end of the limit box and the limit rods;

[0012] Counterweight blocks, a plurality of counterweight blocks are all slidably sleeved on the side wall of the support rod. A limit groove is arranged at the bottom end of the counterweight block. The first limit plate is matched with the limit groove. The outer diameter of the connecting ring is smaller than the inner diameter of the counterweight block;

[0013] Limit component, the limit component is used to limit the probe assembly.

[0014] Preferably, a through hole is arranged at the bottom end of the measuring cake, and the diameter of the through hole of the measuring cake is set to be the same as the inner diameter of the probe assembly.

[0015] Preferably, the electric control component includes a battery component, the battery component is fixedly installed on the outer wall of one side of the limit box, the battery component is electrically connected to the three bistable electromagnets on the same side of the limit box, and a PLC controller is arranged on the outer shell of the battery component. The PLC controller is used to control the plurality of bistable electromagnets on the same side of the limit box.

[0016] Preferably, the elastic support structure includes a support ring, the support ring is fixedly sleeved on the side wall of the limit rod, a second spring is installed at the top end of the support ring, the second spring is sleeved on the limit rod, and a sliding ring is installed at the top end of the second spring. The top end of the sliding ring is in close contact with the bottom end of the limit box.

[0017] Preferably, the limiting component includes two bases fixedly installed at the top of the cake measuring device. A support block is fixedly installed at the top of the base, and two rail seats are fixedly installed at the top of the base. A slider is slidably installed between the two rail seats. The support block is located at one end of the base away from the measuring rod assembly. A second limiting plate is arranged on one side of the slider close to the measuring rod assembly, and the second limiting plate is slidably clamped with the measuring needle. A T-shaped rod is fixedly installed on one side of the slider close to the support block, and the T-shaped rod penetrates through and is slidably connected to the slider. An elastic support assembly is arranged between the support block and the slider.

[0018] Preferably, a plurality of clamping grooves are arranged in an array on the side wall of the measuring needle. The cross-section of the clamping groove of the measuring needle is trapezoidal, the inclined surface of the trapezoidal cross-section of the clamping groove of the measuring needle faces upward, and the cross-section of the second limiting plate is trapezoidal.

[0019] Preferably, the elastic support assembly includes a third spring sleeved on the side wall of the T-shaped rod. Limiting rings are installed at both ends of the third spring, and the limiting rings are slidably sleeved on the T-shaped rod.

[0020] Preferably, two limiting holes are arranged on the side wall of the limiting tube, and the limiting holes are matched with the adjacent second limiting plates.

[0021] A detection method for the thickness of bottom sediment in a cast-in-place pile hole includes the following steps:

[0022] S1. Before placing it into the pile hole, place the device on a flat ground so that the measuring needle is perpendicular to the cake measuring device, and the bottom end of the measuring needle is flush with the bottom surface of the cake measuring device. Determine the number of counterweight blocks according to the nature of the bottom sediment in the hole. Through the PLC controller, the battery assembly cooperates with the bistable electromagnet to increase the magnetic force on the magnetic attraction block, the first spring is compressed, and the magnetic attraction block, U-shaped frame and first limiting plate slide synchronously in the variable-diameter square box to cancel the limit on the adjacent counterweight blocks and adjust the number of effective counterweight blocks;

[0023] S2. Lift the steel wire rope to pull up the connecting ring and place the device into the pile hole. When the cake measuring device is on the surface of the bottom sediment in the hole, it is supported by the sediment. Release the steel wire rope, and the measuring needle passes through the central through hole of the cake measuring device and inserts into the bottom of the hole. At the same time, the measuring needle pushes the second limiting plate to drive the slider to slide between the two rail seats, and the third spring is compressed between the slider and the support block;

[0024] S3. Lift the steel wire rope again to pull the device out of the pile hole. At the same time, the counterweight block presses against the top wall of the limiting box, the slider resets under the action of the third spring, the second limiting plate inserts into the clamping groove of the measuring needle to fix the measuring needle, and the length of the measuring needle protruding from the bottom surface of the cake measuring device is measured, which is the thickness of the sediment.

[0025] Preferably, in S2, when the test cake just touches the surface of the bottom sediment in the hole, the limit box and the four sliding rings slide downward between the four limit rods synchronously. The damping layer on the side wall of the limit rod frictions with the limit box to consume kinetic energy. The second spring compresses between the sliding ring and the support ring, playing a role in damping the device and improving the stability of the detection device.

[0026] The beneficial effects of the present invention are as follows:

[0027] 1. By setting the limit component, the beneficial effect that can be obtained is the test cake. A limit tube is provided at the top of the test cake. The measuring rod component includes a measuring needle, and the measuring needle is slidably installed on the inner wall of the limit tube. A limit sleeve is installed at the top of the measuring needle, a support rod is installed at the top of the limit sleeve, and a connecting ring is fixedly installed at the top of the support rod. The connecting ring is used to connect the steel wire rope. The support component includes four limit rods, and the limit rods are fixedly installed at the top of the test cake. The limit rods penetrate and are slidably connected with the limit box. A round plate is provided at the top of the limit rod, a damping layer is provided on the outer wall of the limit rod, an elastic support structure is provided between the bottom end of the limit box and the limit rod. A plurality of counterweight blocks are all slidably sleeved on the side wall of the support rod. A limit groove is provided at the bottom end of the counterweight block. The first limit plate matches the limit groove. The outer diameter of the connecting ring is smaller than the inner diameter of the counterweight block. The limit component is used to limit the measuring rod component;

[0028] Place the device on a flat ground so that the measuring needle is perpendicular to the test cake, and the bottom end of the measuring needle is flush with the bottom surface of the test cake. Lift the steel wire rope to pull up the connecting ring, and place the device into the pile hole. When the test cake is on the surface of the bottom sediment at the bottom of the hole, the test cake is supported by the sediment. Loosen the steel wire rope, and the measuring needle passes through the central through hole of the test cake and inserts into the bottom of the hole. At the same time, the measuring needle pushes the second limit plate, driving the slider to slide between the two rail seats, and the third spring compresses between the slider and the support block. Lift the steel wire rope again and pull the device out of the pile hole. Measure the length of the measuring needle protruding from the bottom surface of the test cake, which is the thickness of the sediment. It has a self-weight pressing type measuring needle, eliminating the power device and reducing the production cost.

[0029] 2. By setting the counterweight block, the beneficial effect that can be obtained is that a plurality of variable-diameter square boxes are fixedly installed on the opposite outer walls of the limit box. A first limit plate is installed through and slidably between the adjacent side walls of the variable-diameter square box and the limit box. A U-shaped frame is fixedly installed at one end of the first limit plate located in the variable-diameter square box. A magnetic attraction block is fixedly installed on the inner wall of the U-shaped frame. A bistable electromagnet is provided on the inner wall of the variable-diameter square box. There is a gap between the bistable electromagnet and the magnetic attraction block. Two first springs are provided between the end of the magnetic attraction block close to the bistable electromagnet and the inner wall of the variable-diameter square box. Electric control components are provided on both opposite sides of the measuring rod component;

[0030] According to the properties of the sediment at the bottom of the hole, the number of counterweight blocks is determined. Through the PLC controller, the battery assembly cooperates with the bistable electromagnet to increase the magnetic force on the magnetic attraction block. The first spring is compressed, and the magnetic attraction block, U-shaped frame, and first limiting plate slide synchronously in the variable-diameter square box, canceling the limit on the adjacent counterweight blocks and adjusting the number of effective counterweight blocks, having a counterweight regulation function and strong adaptability to the sediment at the bottom of the pile hole.

[0031] 3. By setting the support assembly and the elastic support structure, the beneficial effect that can be obtained is that the elastic support structure includes a support ring. The support ring is fixedly sleeved on the side wall of the limiting rod. A second spring is installed at the top of the support ring. The second spring is sleeved on the limiting rod. A sliding ring is installed at the top of the second spring. The top of the sliding ring is in close contact with the bottom end of the limiting box.

[0032] When the measuring cake just touches the surface of the sediment at the bottom of the hole, the limiting box and the four sliding rings slide downward synchronously between the four limiting rods. The damping layer on the side wall of the limiting rod consumes kinetic energy by friction with the limiting box, and the second spring is compressed between the sliding ring and the support ring, playing a role in damping the device and improving the stability of the detection device. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] For the convenience of those skilled in the art to understand, the present invention will be further described below with reference to the accompanying drawings.

[0034] Figure 1 is the overall structural schematic diagram of the present invention;

[0035] Figure 2 is the installation structure diagram of the counterweight block and the support rod in the present invention;

[0036] Figure 3 is the installation structure diagram of the limiting box in the present invention;

[0037] Figure 4 is the installation structure diagram of the bistable electromagnet and the variable-diameter square box in the present invention;

[0038] Figure 5 is the installation structure diagram of the first limiting plate and the U-shaped frame in the present invention;

[0039] Figure 6 is the installation structure diagram of the elastic support structure in the present invention;

[0040] Figure 7 is the installation structure diagram of the elastic support assembly in the present invention;

[0041] Figure 8 is the installation structure diagram of the T-shaped rod in the present invention.

[0042] Description of the reference numerals:

[0043] In the figure: 1, measuring cake; 11, limiting tube; 12, limiting hole; 2, measuring rod assembly; 21, measuring needle; 22, limiting sleeve; 23, support rod; 24, connecting ring; 3, limiting box; 31, variable-diameter square box; 32, first limiting plate; 33, U-shaped frame; 34, magnetic attraction block; 35, bistable electromagnet; 36, first spring; 37, battery assembly; 38, PLC controller; 41, limiting rod; 42, round plate; 43, support ring; 44, second spring; 45, sliding ring; 5, counterweight; 51, limiting groove; 6, limiting assembly; 61, base; 62, support block; 63, rail seat; 64, slider; 65, second limiting plate; 66, stop block; 67, T-shaped rod; 68, third spring; 69, limiting ring. Detailed implementation manner

[0044] To further elaborate on the technical means and effects adopted by the present invention to achieve the predetermined invention purpose, the following describes in detail the specific implementation manner, structure, features and their effects of the present invention in combination with the accompanying drawings and preferred embodiments. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts belong to the scope of protection of the present invention.

[0045] In the description of the present application, it should be understood that the orientation or positional relationship indicated by terms such as "inside", "outside", etc. is based on the orientation or position shown in the drawings, and is only for the convenience of describing the present application and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, a specific orientation structure and operation, and therefore should not be construed as a limitation to the present application.

[0046] Refer to Figures 1-8 , a detection device and method for the thickness of sediment at the bottom of a cast-in-place pile hole disclosed in the present invention, including a measuring cake 1. A limiting tube 11 is provided at the top end of the measuring cake 1. Two limiting holes 12 are provided on the side wall of the limiting tube 11. A through hole is provided at the bottom end of the measuring cake 1. The diameter of the through hole of the measuring cake 1 is the same as the inner diameter of the measuring rod assembly 2;

[0047] The measuring rod assembly 2 includes a measuring needle 21. The measuring needle 21 is slidably installed on the inner wall of the limiting tube 11. A limiting sleeve 22 is installed at the top end of the measuring needle 21. A support rod 23 is installed at the top end of the limiting sleeve 22. A connecting ring 24 is fixedly installed at the top end of the support rod 23. The connecting ring 24 is used to connect the steel wire rope;

[0048] The limit box 3, on both opposite outer walls of the limit box 3, a plurality of variable-diameter square boxes 31 are fixedly installed. A first limit plate 32 is installed through and slidably between the adjacent side walls of the variable-diameter square box 31 and the limit box 3. One end of the first limit plate 32 located inside the variable-diameter square box 31 is fixedly installed with a U-shaped frame 33. A magnetic attraction block 34 is fixedly installed on the inner wall of the U-shaped frame 33. A bistable electromagnet 35 is arranged on the inner wall of the variable-diameter square box 31. There is a gap between the bistable electromagnet 35 and the magnetic attraction block 34. Between the end of the magnetic attraction block 34 close to the bistable electromagnet 35 and the inner wall of the variable-diameter square box 31, two first springs 36 are arranged. On both opposite sides of the measuring rod assembly 2, an electric control assembly is arranged. The electric control assembly includes a battery assembly 37. The battery assembly 37 is fixedly installed on one outer wall of the limit box 3. The battery assembly 37 is electrically connected to the three bistable electromagnets 35 on the same side of the limit box 3. A PLC controller 38 is arranged on the outer shell of the battery assembly 37. The PLC controller 38 is used to control the multiple bistable electromagnets 35 on the same side of the limit box 3;

[0049] The support assembly, the support assembly includes four limit rods 41. The limit rods 41 are fixedly installed at the top of the measuring cake 1. The limit rods 41 are installed through and slidably connected with the limit box 3. A round plate 42 is arranged at the top of the limit rods 41. A damping layer is arranged on the outer wall of the limit rods 41. An elastic support structure is arranged between the bottom end of the limit box 3 and the limit rods 41. The elastic support structure includes a support ring 43. The support ring 43 is fixedly sleeved on the side wall of the limit rod 41. A second spring 44 is installed at the top of the support ring 43. The second spring 44 is sleeved on the limit rod 41. The top of the second spring 44 is installed with a sliding ring 45. The top of the sliding ring 45 is in fit with the bottom end of the limit box 3;

[0050] The counterweight 5, a plurality of counterweights 5 are all slidably sleeved on the side wall of the support rod 23. The outer diameter of the connecting ring 24 is smaller than the inner diameter of the counterweight 5. A limit groove 51 is arranged at the bottom end of the counterweight 5. The first limit plate 32 is matched with the limit groove 51;

[0051] The limit component 6 is used to limit the measuring rod component 2. The limit component 6 includes two bases 61 which are fixedly installed at the top end of the measuring cake 1. A support block 62 is fixedly installed at the top end of the base 61. Two rail seats 63 are fixedly installed at the top end of the base 61. A slider 64 is slidably installed between the two rail seats 63. The support block 62 is located at one end of the base 61 away from the measuring rod component 2. A second limit plate 65 is arranged on the side of the slider 64 close to the measuring rod component 2. The second limit plate 65 is slidably clamped with the measuring needle 21. The limit hole 12 matches the adjacent second limit plate 65. A plurality of clamping grooves distributed in an array are arranged on the side wall of the measuring needle 21. The cross section of the clamping groove of the measuring needle 21 is trapezoidal. The inclined surface of the trapezoidal cross section of the clamping groove of the measuring needle 21 faces upward. The cross section of the second limit plate 65 is trapezoidal. A T-shaped rod 67 is fixedly installed on the side of the slider 64 close to the support block 62. The T-shaped rod 67 penetrates through and is slidably connected with the slider 64. An elastic support component is arranged between the support block 62 and the slider 64. The elastic support component includes a third spring 68. The third spring 68 is sleeved on the side wall of the T-shaped rod 67. Limit rings 69 are installed at both ends of the third spring 68. The limit rings 69 are slidably sleeved on the T-shaped rod 67.

[0052] The present invention also discloses a detection method for the thickness of bottom sediment in a cast-in-place pile hole, including the following steps:

[0053] S1. Before placing it into the pile hole, place the device on a flat ground so that the measuring needle 21 is perpendicular to the measuring cake 1, and the bottom end of the measuring needle 21 is flush with the bottom surface of the measuring cake 1. Determine the number of counterweight blocks 5 according to the nature of the bottom sediment in the hole. Through the PLC controller 38, the battery assembly 37 cooperates with the bistable electromagnet 35 to increase the magnetic force on the magnetic attraction block 34. The first spring 36 is compressed. The magnetic attraction block 34, the U-shaped frame 33 and the first limit plate 32 slide synchronously in the variable-diameter square box 31 to cancel the limit on the adjacent counterweight blocks 5 and adjust the number of effective counterweight blocks 5.

[0054] S2. Lift the steel wire rope to pull up the connecting ring 24 and place the device into the pile hole. When the measuring cake 1 is on the surface of the bottom sediment in the hole, the measuring cake 1 is supported by the sediment. Release the steel wire rope. The measuring needle 21 passes through the central through hole of the measuring cake 1 and inserts into the bottom of the hole. At the same time, the measuring needle 21 pushes the second limit plate 65 to drive the slider 64 to slide between the two rail seats 63, and the third spring 68 is compressed between the slider 64 and the support block 62.

[0055] S3. Lift the steel wire rope again to pull the device out of the pile hole. At the same time, the counterweight block 5 abuts against the top wall of the limit box 3. The slider 64 resets under the action of the third spring 68. The second limit plate 65 inserts into the clamping groove of the measuring needle 21 to fix the measuring needle 21. The length of the measuring needle 21 protruding from the bottom surface of the measuring cake 1 is measured, which is the thickness of the sediment.

[0056] Preferably, in S2, when the test cake 1 just touches the surface of the bottom sediment in the hole, the limit box 3 and the four sliding rings 45 slide downward between the four limit rods 41 synchronously. The damping layer on the side wall of the limit rod 41 consumes kinetic energy by friction with the limit box 3, and the second spring 44 is compressed between the sliding ring 45 and the support ring 43, playing a role in damping the device and improving the stability of the detection device.

[0057] The above are only the preferred embodiments of the present invention, and do not impose any form of limitation on the present invention. Although the present invention has been disclosed above with the preferred embodiments, it is not intended to limit the present invention. Any person skilled in the art can make some changes or modifications to equivalent embodiments by using the disclosed technical content within the scope of the technical solution of the present invention. However, as long as it does not depart from the technical solution content of the present invention, any brief modifications, equivalent changes and modifications made to the above embodiments based on the technical essence of the present invention still fall within the scope of the technical solution of the present invention.

Claims

1. A device for detecting the thickness of sediment at the bottom of a bored pile hole, characterized in that: include: A measuring cake (1), wherein a limiting tube (11) is provided at the top of the measuring cake (1); A measuring rod assembly (2), the measuring rod assembly (2) comprising a measuring needle (21), the measuring needle (21) being slidably mounted on the inner wall of the limiting tube (11), a limiting sleeve (22) being mounted on the top end of the measuring needle (21), a supporting rod (23) being mounted on the top end of the limiting sleeve (22), a connecting ring (24) being fixedly mounted on the top end of the supporting rod (23), and the connecting ring (24) being used for connecting a steel wire rope; A limit box (3), wherein a plurality of diameter-changing square boxes (31) are fixedly installed on the outer walls on both sides facing each other of the limit box (3), a first limit plate (32) is penetrated and slidably installed between the adjacent side walls of the diameter-changing square box (31) and the limit box (3), a U-shaped frame (33) is fixedly installed on one end of the first limit plate (32) located in the diameter-changing square box (31), a magnetic block (34) is fixedly installed on the inner wall of the U-shaped frame (33), a bistable electromagnet (35) is arranged on the inner wall of the diameter-changing square box (31), a spacing is left between the bistable electromagnet (35) and the magnetic block (34), two first springs (36) are arranged between one end of the magnetic block (34) close to the bistable electromagnet (35) and the inner wall of the diameter-changing square box (31), and electric control components are arranged on both sides facing each other of the measuring rod assembly (2); A support assembly, the support assembly comprising four limit rods (41), the limit rods (41) being fixedly mounted on the top end of the test cake (1), the limit rods (41) being penetrated and slidably connected to the limit box (3), the top end of the limit rods (41) being provided with a circular plate (42), the outer wall of the limit rods (41) being provided with a damping layer, and an elastic support structure being provided between the bottom end of the limit box (3) and the limit rods (41); A counterweight block (5), wherein a plurality of the counterweight blocks (5) are slidably sleeved on the side wall of the support rod (23), a limiting groove (51) is provided at the bottom end of the counterweight block (5), the first limiting plate (32) matches the limiting groove (51), and the outer diameter of the connecting ring (24) is smaller than the inner diameter of the counterweight block (5); A limit assembly (6), the limit assembly (6) is used to limit the position of the measuring rod assembly (2), the limit assembly (6) comprises two bases (61), and the bases (61) are fixedly mounted on the top of the measuring cake (1).

2. A device for detecting the thickness of sediment at the bottom of a bored pile hole according to claim 1, characterized in that: A through hole is provided at the bottom end of the measuring cake (1), and the diameter of the through hole of the measuring cake (1) is the same as the inner diameter of the measuring rod assembly (2).

3. A device for detecting the thickness of sediment at the bottom of a bored pile hole according to claim 1, characterized in that: The electric control component comprises a battery component (37), the battery component (37) is fixedly mounted on an outer wall of one side of the limit box (3), the battery component (37) is electrically connected to three bistable electromagnets (35) on the same side of the limit box (3), and a PLC controller (38) is provided on the housing of the battery component (37), and the PLC controller (38) is used to control the multiple bistable electromagnets (35) on the same side of the limit box (3).

4. A device for detecting the thickness of sediment at the bottom of a bored pile hole according to claim 1, characterized in that: The elastic support structure comprises a support ring (43), the support ring (43) being fixedly sleeved on the side wall of the limiting rod (41), a second spring (44) being mounted on the top end of the support ring (43), the second spring (44) being sleeved with the limiting rod (41), a sliding ring (45) being mounted on the top end of the second spring (44), the top end of the sliding ring (45) being fitted with the bottom end of the limiting box (3).

5. A device for detecting the thickness of sediment at the bottom of a bored pile hole according to claim 1, characterized in that: A support block (62) is fixedly mounted on the top of the base (61), two rail seats (63) are fixedly mounted on the top of the base (61), a slider (64) is slidably mounted between the two rail seats (63), the support block (62) is located at an end of the base (61) away from the measuring rod assembly (2), a second limit plate (65) is arranged on a side of the slider (64) close to the measuring rod assembly (2), the second limit plate (65) is slidably engaged with the measuring needle (21), a T-shaped rod (67) is fixedly mounted on a side of the slider (64) close to the support block (62), the T-shaped rod (67) and the slider (64) are penetrated and slidably connected, and an elastic support assembly is arranged between the support block (62) and the slider (64).

6. A device for detecting the thickness of sediment at the bottom of a bored pile hole according to claim 5, characterized in that: The side wall of the measuring needle (21) is provided with a plurality of clamping grooves distributed in an array, the clamping groove of the measuring needle (21) has a trapezoidal cross section, the inclined surface of the trapezoidal cross section of the clamping groove of the measuring needle (21) is arranged upward, and the cross section of the second limiting plate (65) is arranged in a trapezoidal shape.

7. A device for detecting the thickness of sediment at the bottom of a bored pile hole according to claim 5, characterized in that: The elastic support assembly comprises a third spring (68), the third spring (68) being sleeved on the side wall of the T-shaped rod (67), and limiting rings (69) are installed on both ends of the third spring (68), and the limiting rings (69) are slidably sleeved with the T-shaped rod (67).

8. A device for detecting sediment thickness at the bottom of a bored pile hole according to claim 5, characterized in that: The side wall of the limiting tube (11) is provided with two limiting holes (12), and the limiting holes (12) match the adjacent second limiting plates (65).

9. A method for detecting the thickness of sediment at the bottom of a bored pile hole, applied to the device for detecting the thickness of sediment at the bottom of a bored pile hole as claimed in claim 7, characterized in that: The following steps are involved: S1. Before the device is placed in the pile hole, the device is placed on a flat ground so that the measuring needle (21) is perpendicular to the measuring cake (1) and the bottom end of the measuring needle (21) is flush with the bottom surface of the measuring cake (1). The number of counterweights (5) is determined according to the nature of the sediment at the bottom of the hole. Through the PLC controller (38), the battery assembly (37) cooperates with the bistable electromagnet (35) to increase the magnetic force on the magnetic suction block (34), the first spring (36) is compressed, and the magnetic suction block (34), the U-shaped frame (33) and the first limit plate (32) slide synchronously on the variable diameter square box (31), cancel the limit on the adjacent counterweights (5), and adjust the number of effective counterweights (5); S2, lift the steel wire rope and pull up the connecting ring (24), put the device into the pile hole, when the measuring cake (1) is located on the surface of the sediment at the bottom of the hole, the measuring cake (1) is supported by the sediment, loosen the steel wire rope, and the measuring needle (21) passes through the central through hole of the measuring cake (1) and is inserted into the bottom of the hole. At the same time, the measuring needle (21) pushes the second limit plate (65), driving the slider (64) to slide between the two rail seats (63), and the third spring (68) is compressed between the slider (64) and the support block (62); S3, lift the wire rope again and pull the device out of the pile hole. At the same time, the counterweight (5) presses against the top wall of the limit box (3), the slider (64) is reset under the action of the third spring (68), the second limit plate (65) is inserted into the clamping groove of the measuring needle (21), the measuring needle (21) is fixed, and the length of the measuring needle (21) protruding from the bottom surface of the measuring cake (1) is measured to be the sediment thickness.

10. A method for detecting sediment thickness at the bottom of a bored pile hole according to claim 9, characterized in that: In S2, when the test cake (1) just contacts the surface of the sediment at the bottom of the hole, the limit box (3) and the four sliding rings (45) slide downwards synchronously between the four limit rods (41), the damping layer on the side wall of the limit rod (41) and the limit box (3) frictionally consume kinetic energy, and the second spring (44) is compressed between the sliding ring (45) and the support ring (43), which has a vibration reduction effect on the device, thereby improving the stability of the detection device.

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