Long-term monitoring sensor for support force of pile bottom of cast-in-place pile and implantation method thereof

Abstract

This invention discloses a long-term monitoring sensor for the bottom support force of cast-in-place piles and its implantation method, belonging to the field of cast-in-place pile technology. A base is placed into a pre-drilled hole in the rock surface below the cast-in-place pile. Then, electricity is supplied to a conductive wire via a circuit board, activating an elastic expansion body by heating it. The expanded elastic expansion body's upper and lower ends respectively abut against the bottom of a plunger and the bottom surface of the base's receiving hole, allowing the top of the plunger to extend upwards into the still-uncured concrete of the cast-in-place pile. The elastic expansion body ensures the bottom surface of the base is tightly pressed against the bottom surface of the pre-drilled hole. After the concrete solidifies, the plunger of the monitoring sensor is firmly fixed to the bottom of the cast-in-place pile. When the cast-in-place pile is subjected to force, the vertical support force is transmitted from the plunger to a pressure sensor. The pressure sensor converts the pressure signal into an electrical signal and transmits it to an integrated circuit board, facilitating long-term monitoring of the cast-in-place pile's support force and achieving continuous long-term monitoring of the pile's support force.

Description

Technical Field

[0001] This invention relates to the field of cast-in-place pile technology, and in particular to a long-term monitoring sensor for the bottom support force of cast-in-place piles and its implantation method. Background Technology

[0002] In the current field of cast-in-place pile engineering testing, traditional strain testing technology has obvious limitations. Its testing accuracy is easily affected by various factors such as the density of the pile concrete, construction disturbance, and testing environment. It often results in a large deviation between the test results and the actual support force of the pile, making it difficult to accurately reflect the true working state of the pile and posing potential risks to the project quality assessment.

[0003] Meanwhile, in order to make up for the shortcomings of traditional testing technologies, some projects have to adopt methods such as static pressure pile testing or core sampling testing. Static pressure pile testing equipment requires a large investment and has a long testing cycle, which greatly increases the cost of project testing. Core sampling testing is a destructive test that will damage the structural integrity of the cast-in-place pile and affect the safety of the project. Moreover, neither of the two testing methods can achieve long-term continuous monitoring of the support force of the cast-in-place pile. Summary of the Invention

[0004] The present invention aims to solve the technical problems existing in the above-mentioned related technologies, and proposes a long-term monitoring sensor for the bottom support force of cast-in-place piles and its implantation method, so as to facilitate long-term monitoring of the support force of cast-in-place piles and realize long-term continuous monitoring of the support force of cast-in-place piles.

[0005] According to a first aspect of the present invention, a long-term monitoring sensor for the pile bottom support force of cast-in-place piles includes:

[0006] The base has a receiving hole at the top, and the base is used to be inserted into a reserved hole in the rock surface below the cast-in-place pile;

[0007] A plunger slides up and down through the receiving hole, with the top of the plunger extending above the base. The plunger has an installation cavity inside, and the top of the plunger is used to extend into the bottom of the grouting pile.

[0008] A sealing ring is disposed between the outer side wall of the plunger and the inner side wall of the receiving hole, and the sealing ring seals the gap between the plunger and the receiving hole;

[0009] An elastic expansion body is disposed in the receiving hole. The elastic expansion body is located below the plunger. The elastic expansion body is an electro-crosslinked prepolymer. After being activated by electric heating, the elastic expansion body changes from a liquid state to a solid elastomer and expands its own volume. The expanded elastic expansion body pushes the plunger and the base away from each other.

[0010] A pressure sensor is located at the bottom of the plunger, and the pressure sensor abuts against the elastic expansion body;

[0011] A circuit board is disposed in the mounting cavity. The circuit board is electrically connected to the pressure sensor. The circuit board is provided with a power-conducting wire that extends into the receiving hole and is electrically connected to the elastic expansion body.

[0012] The long-term monitoring sensor for the bottom support force of cast-in-place piles according to embodiments of the present invention has at least the following beneficial effects: When the monitoring sensor is placed in a pre-drilled hole in the rock surface below the cast-in-place pile, and the first batch of concrete is injected into the pile, the sensor is entirely within the pre-drilled hole, preventing the injected concrete from squeezing and damaging it. After the first batch of concrete is injected, electricity is supplied to the conductive wire via the circuit board, activating the elastic expansion body by heating it. This causes the elastic expansion body to change from a liquid state to a solid elastic body and expand its volume. The expanded elastic expansion body then abuts against the bottom of the plunger and the bottom surface of the base receiving hole at its upper and lower ends, respectively. The plunger's top extends upwards into the still-uncured concrete of the cast-in-place pile. The sealing ring prevents the elastic expansion body in the receiving hole from leaking outwards and also prevents external liquids from entering the receiving hole and contaminating the elastic expansion body. The elastic expansion body ensures that the bottom surface of the base is tightly attached to the bottom surface of the reserved hole. After the concrete has solidified, the plunger of the monitoring sensor is firmly fixed to the bottom of the cast-in-place pile. When the cast-in-place pile is under stress, the vertical support force is transmitted from the plunger to the pressure sensor. The pressure sensor converts the pressure signal into an electrical signal and transmits it to the integrated circuit board to facilitate long-term monitoring of the support force of the cast-in-place pile, thus achieving long-term continuous monitoring of the support force of the cast-in-place pile.

[0013] According to some embodiments of the present invention, the elastic expander comprises a prepolymer and a conductive filler, wherein the prepolymer and the conductive filler are uniformly mixed.

[0014] According to some embodiments of the present invention, the prepolymer is a polyurethane prepolymer.

[0015] According to some embodiments of the present invention, the long-term monitoring sensor for the pile bottom support force of the cast-in-place pile further includes:

[0016] An electrical connection wire is electrically connected to the circuit board, extending upwards from the plunger to above the grouting pile.

[0017] According to some embodiments of the present invention, the long-term monitoring sensor for the pile bottom support force of the cast-in-place pile further includes:

[0018] A protective tube is hinged to the outer wall of the plunger, the protective tube protrudes outward from the plunger, and the electrical connection wire passes through the protective tube.

[0019] The long-term monitoring sensor for the pile bottom support force of the grouting pile also includes:

[0020] The terminal is electrically connected to the circuit board via the electrical connection line, and the circuit board sends the pressure value measured by the pressure sensor to the terminal in real time.

[0021] According to some embodiments of the present invention, the long-term monitoring sensor for the pile bottom support force of the cast-in-place pile further includes:

[0022] An inclination sensor is disposed in the mounting cavity, and the inclination sensor is used to measure the angle at which the plunger tilts as the grouting pile tilts.

[0023] According to some embodiments of the present invention, the long-term monitoring sensor for the pile bottom support force of the cast-in-place pile further includes:

[0024] A strain sensor is located on top of the plunger.

[0025] According to some embodiments of the present invention, the long-term monitoring sensor for the pile bottom support force of the cast-in-place pile further includes:

[0026] A displacement sensor is disposed between the plunger and the receiving hole, and the displacement sensor measures the distance the plunger moves relative to the receiving hole.

[0027] According to a second aspect of the present invention, a method for implanting a long-term monitoring sensor for the bottom support force of a cast-in-place pile is provided for implanting the long-term monitoring sensor for the bottom support force of a cast-in-place pile as described in the above embodiments. The implantation method includes:

[0028] Drill a pre-reserved hole in the rock surface below the cast-in-place pile;

[0029] The long-term monitoring sensor for the pile bottom support force of the cast-in-place pile is placed in the reserved hole, and the bottom surface of the base is in contact with the bottom surface of the reserved hole;

[0030] Concrete is injected into the cast-in-place pile, and electricity is supplied to the elastic expansion body through the energized conductor to change the elastic expansion body from a liquid state to a solid elastic body;

[0031] After the elastic expansion body expands, it pushes the plunger upward into the concrete, and after the elastic expansion body expands, it pushes the bottom surface of the base to fit tightly against the bottom surface of the reserved hole.

[0032] The method for implanting a long-term monitoring sensor for the bottom support force of a cast-in-place pile according to an embodiment of the present invention has at least the following beneficial effects: Before the cast-in-place pile is filled with concrete, a pre-drilled hole is drilled in the rock surface below it, and the monitoring sensor is placed in the pre-drilled hole in the rock surface below the cast-in-place pile. The first batch of concrete is then injected into the cast-in-place pile. Since the monitoring sensor is entirely within the pre-drilled hole, the injected concrete can prevent it from being crushed or damaged. After the first batch of concrete is injected, electricity is supplied to the power-conducting wire through the circuit board, activating the elastic expansion body by heating it with the power-conducting wire. This causes the elastic expansion body to change from a liquid state to a solid elastic body and expand its volume. The expanded elastic expansion body then presses against the upper and lower ends of the wire. The bottom of the plunger is connected to the bottom surface of the base receiving hole, allowing the top of the plunger to extend upwards into the uncured concrete of the cast-in-place pile. The sealing ring prevents the elastic expansion body in the receiving hole from leaking outwards and also prevents external liquids from entering the receiving hole and contaminating the elastic expansion body. The elastic expansion body ensures that the bottom surface of the base is tightly attached to the bottom surface of the reserved hole. After the concrete has solidified, the plunger of the monitoring sensor is firmly fixed to the bottom of the cast-in-place pile. When the cast-in-place pile is under stress, the vertical support force is transmitted from the plunger to the pressure sensor. The pressure sensor converts the pressure signal into an electrical signal and transmits it to the integrated circuit board to facilitate long-term monitoring of the support force of the cast-in-place pile, achieving long-term continuous monitoring of the support force of the cast-in-place pile. Attached Figure Description

[0033] Figure 1 This is a schematic diagram of the structure of a long-term monitoring sensor for the bottom support force of a cast-in-place pile according to an embodiment of the present invention;

[0034] Figure 2 This is a cross-sectional schematic diagram of a long-term monitoring sensor for the bottom support force of a cast-in-place pile according to an embodiment of the present invention;

[0035] Figure 3 This is a flowchart of a method for implanting a long-term monitoring sensor for the bottom support force of a cast-in-place pile according to an embodiment of the present invention.

[0036] Reference numerals: base 100, receiving hole 110, plunger 200, mounting cavity 210, sealing ring 300, elastic expansion body 400, pressure sensor 500, protective tube 600, strain sensor 700, displacement sensor 800. Detailed Implementation

[0037] Embodiments of the present invention are described in detail below. Examples of these embodiments are shown in the accompanying drawings, wherein the same or similar reference numerals denote the same or similar elements or elements having the same or similar functions throughout. The embodiments described below with reference to the accompanying drawings are exemplary and are only used to explain the present invention, and should not be construed as limiting the present invention.

[0038] In the description of this invention, it should be understood that the terms front, back, up, down, axial, circumferential, etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the drawings. They are only for the convenience of describing this invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limiting this invention.

[0039] In the description of this invention, "multiple" means two or more; "greater than," "less than," and "exceeding" are understood to exclude the stated number; "above," "below," and "within" are understood to include the stated number. The use of "first" and "second" in the description is merely for distinguishing technical features and should not be construed as indicating or implying relative importance, or implicitly indicating the number of indicated technical features, or implicitly indicating the order of the indicated technical features.

[0040] In the description of this invention, it should be noted that terms such as "set up," "install," and "connect" should be interpreted broadly, and those skilled in the art can reasonably determine the specific meaning of the above terms in this invention in conjunction with the specific content of the technical solution.

[0041] The technical solution of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the embodiments described below are some embodiments of the present invention, not all embodiments.

[0042] In the current field of cast-in-place pile engineering testing, traditional high-strain and low-strain testing technologies have obvious limitations. Their testing accuracy is easily affected by various factors such as the density of the pile concrete, construction disturbance, and testing environment. Often, the test results deviate significantly from the actual support force of the pile, making it difficult to accurately reflect the true working state of the pile and posing potential risks to the project quality assessment.

[0043] At the same time, in order to make up for the shortcomings of traditional testing technologies, some projects have to adopt methods such as static pressure pile testing or core sampling testing. Static pressure pile testing equipment requires a large investment and has a long testing cycle, which greatly increases the cost of project testing. Core sampling testing is a destructive test that will damage the integrity of the pile structure and affect the safety of the project. Moreover, neither of the two testing methods can achieve continuous monitoring of the support force of the cast-in-place pile.

[0044] To address the aforementioned industry pain points, this invention innovatively proposes corresponding technical solutions and, through a comprehensive technical approach, achieves continuous quality and safety monitoring of the support force of cast-in-place piles throughout their entire lifecycle, from the construction stage to the later operation and use stage. This effectively fills the gap in existing technologies and provides a brand-new solution for the quality control of cast-in-place pile projects.

[0045] Reference Figures 1 to 2 As shown, the present invention provides a long-term monitoring sensor for the bottom support force of cast-in-place piles.

[0046] The long-term monitoring sensor for the bottom support force of cast-in-place piles includes a base 100, a plunger 200, a sealing ring 300, an elastic expansion body 400, a pressure sensor 500, a circuit board, an electrical connection wire, a terminal, a protective tube 600, an inclination sensor, a strain sensor 700, and a displacement sensor 800.

[0047] The base 100 has a top-open receiving hole 110. The plunger 200 is divided into an upper section and a lower section in the vertical direction. The lower section of the plunger 200 is slidably disposed in the receiving hole 110. The lower section of the plunger 200 can move up and down along the receiving hole 110. The upper section of the plunger 200 has a mounting cavity 210 inside. The circuit board and the tilt sensor are disposed in the mounting cavity 210. The tilt sensor is electrically connected to the circuit board and sends the measured tilt information to the circuit board.

[0048] A sealing ring 300 is provided at the top of the receiving hole 110, and the sealing ring 300 closes the gap between the lower outer wall of the plunger 200 and the inner wall of the receiving hole 110.

[0049] An elastic expansion body 400 is disposed in the receiving hole 110, and the elastic expansion body 400 is an electro-crosslinked prepolymer.

[0050] Electro-crosslinked prepolymers are a class of functional material systems that use liquid prepolymers as the core, with the addition of conductive fillers, crosslinking agents, and functional additives. Triggered by a low-voltage electrical signal, the prepolymer molecules undergo a crosslinking reaction through electrothermal (Joule heating) or electro-redox reactions, forming a three-dimensional network structure accompanied by controllable volume expansion, ultimately solidifying into a solid (elastomer / rigid body). The core characteristics of electro-crosslinked prepolymers are "room-temperature liquid state, electro-curing, and controllable expansion." They require no external auxiliary conditions such as high temperature, high pressure, or light exposure; the curing speed, expansion rate, and post-curing properties can be precisely controlled using only low-voltage electricity, making them suitable for various applications such as large-volume molding, gap filling, and sealing.

[0051] The "electric curing + volume expansion" characteristics of electro-crosslinked prepolymer rely on two core processes: "electro-induced heat generation triggering crosslinking reaction" and "foaming agent assisted expansion". The whole process is divided into four continuous stages, each stage working together to ultimately achieve the transformation from liquid to solid.

[0052] Phase 1: Construction of conductive pathways (triggering prerequisites).

[0053] One of the core components of electro-crosslinked prepolymers is conductive filler (such as conductive carbon black, graphene, metal powder, etc.), which enables the originally insulating liquid prepolymer to form a continuous conductive path.

[0054] At room temperature, the conductive filler is uniformly dispersed in the prepolymer system to form a homogeneous liquid composite of "prepolymer + conductive filler". When electricity is applied, the current passes through the conductive filler to form a closed loop. According to Joule's law, the current will generate heat (Joule heating) when it flows in the conductive medium. The heat is uniformly transferred to the entire system, causing the internal temperature of the system to rise rapidly to 40~60℃ (low temperature flexibility range), providing triggering conditions for subsequent crosslinking and foaming reactions.

[0055] Key points: The content and dispersibility of conductive filler directly affect the Joule heating efficiency. Generally, the filler addition amount is 5% to 15%. The more uniform the dispersion, the more stable the heat generation, avoiding local overheating or insufficient heat generation.

[0056] Second stage: Electro-induced cross-linking reaction (solidification of the core).

[0057] The main components of the electro-crosslinked prepolymer are a liquid prepolymer (containing unreacted active groups) and a crosslinking agent. Joule heating triggers an irreversible chemical crosslinking reaction between the two, which is the core process for achieving the "liquid → solid" transformation.

[0058] Third stage: Volume expansion (functional characteristics).

[0059] The volume expansion of the electro-crosslinked prepolymer mainly relies on the low-temperature foaming agent (such as azodicarbonamide ADC, sodium bicarbonate, etc.) added to the system, which proceeds simultaneously with the crosslinking reaction to achieve "simultaneous curing and expansion".

[0060] Phase 4: Finalization and shaping (final state).

[0061] Once the crosslinking reaction is complete, the three-dimensional network structure is fully formed, and the tiny bubbles generated by the decomposition of the foaming agent are firmly fixed in the network structure and cannot escape; the system stops expanding, the volume is permanently fixed, and finally a "closed-cell elastic foamed solid" or "rigid foamed solid" is formed, completing the entire electro-crosslinking process.

[0062] The core logic of the entire process is: power on → conductive filler generates heat → triggers cross-linking and foaming → cross-linking forms a network to fix the bubbles → curing and molding. The entire process requires no external intervention and can be precisely controlled solely through electrical signals.

[0063] In this embodiment, the prepolymer is specifically a polyurethane prepolymer.

[0064] Therefore, before the monitoring sensor is installed at the bottom of the grouting pile, the elastic expansion body 400 is stored in the receiving hole 110 in liquid form, and the liquid elastic expansion body 400 is sealed between the receiving hole 110, the lower section of the plunger 200 and the sealing ring 300.

[0065] The pressure sensor 500 is located at the bottom of the lower section of the plunger 200. The plunger 200 has a channel for routing wires inside, which connects the bottom of the plunger 200 and the mounting cavity 210. The pressure sensor 500 is electrically connected to the circuit board of the mounting cavity 210 through the wires. The pressure sensor 500 is a piezoelectric ceramic sensor. The top of the plunger 200 directly contacts the concrete at the bottom of the pile. When the cast-in-place pile is under force, it will squeeze the plunger 200 downward. The vertical support force of the plunger 200 will be transmitted to the pressure sensor 500 at the bottom. The pressure sensor 500 converts the pressure signal into an electrical signal and transmits it to the integrated circuit board.

[0066] The strain sensor 700 is located at the top of the upper section of the plunger 200. The channel inside the plunger 200 is also connected to the top of the plunger 200. The strain sensor 700 is electrically connected to the circuit board of the mounting cavity 210 through a wire. The strain sensor 700 sends the measured strain data to the circuit board. The strain sensor 700 adopts an array-type passive sonar sensor (piezoelectric ceramic array). The strain sensor 700 collects the strain data of the cast-in-place pile, optimizes the traditional two-way feedback of strain detection to single-way feedback, and optimizes the traditional single linear detection to array scanning, which greatly improves the accuracy and data completeness of strain detection.

[0067] The displacement sensor 800 is disposed between the lower section of the plunger 200 and the inner wall of the receiving hole 110. The displacement sensor 800 includes a Hall sensor and a magnet. The Hall sensor is electrically connected to the circuit board. The Hall sensor is disposed on the outer wall of the lower section of the plunger 200, and the magnet is disposed on the inner wall of the receiving hole 110. When the lower section of the plunger 200 moves relative to the receiving hole 110, the Hall sensor moves relative to the magnet, thereby reading the displacement data in real time and sending the displacement data to the circuit board. Based on the displacement data, the vertical upward or downward displacement of the cast-in-place pile can be calculated.

[0068] The outer wall of the plunger 200 is provided with a groove, and the bottom end of the protective tube 600 is hinged to the inner wall of the groove. The protective tube 600 rotates around the horizontal axis, and after the protective tube 600 rotates downward by 90°, the outer wall of the protective tube 600 abuts against the bottom wall of the groove, thereby causing the protective tube 600 to open outward perpendicular to the plunger 200.

[0069] The electrical connection wire passes through the protective tube 600 and extends into the mounting cavity 210 inside the plunger 200. The electrical connection wire is electrically connected to the circuit board. The circuit board transmits the collected monitoring data outward through the electrical connection wire. The electrical connection wire is provided with a protective layer to prevent the electrical connection wire from being squeezed and corroded by concrete.

[0070] The terminal is electrically connected to the circuit board via an electrical connection cable. The circuit board sends the collected monitoring data to the terminal in real time, so that the monitoring data of the cast-in-place pile can be obtained from the terminal in real time.

[0071] The circuit board integrates various monitoring data such as pressure, displacement, strain, and tilt angle, and transmits the monitoring data to the terminal through electrical connection lines to realize real-time display, storage and analysis of monitoring data, providing data support for the long-term stability assessment of the pile bottom support force of cast-in-place piles.

[0072] Before implanting the monitoring sensor, a pre-drilled hole needs to be drilled in the rock surface below the cast-in-place pile. The diameter of the pre-drilled hole is larger than the diameter of the monitoring sensor to ensure that the monitoring sensor can be easily placed into the pre-drilled hole. Since the elastic expansion body 400 has not yet been activated and expanded, the distance between the lower section of the plunger 200 and the bottom wall of the receiving hole 110 is small, ensuring that the plunger 200 can fall completely into the pre-drilled hole. When the first bucket of concrete is injected into the cast-in-place pile, the concrete falls downwards to prevent the falling concrete from directly impacting the monitoring sensor and causing damage to the monitoring sensor. It also ensures that the position of the monitoring sensor is fixed in the receiving hole 110, avoiding data distortion caused by changes in the position of the monitoring sensor.

[0073] After the first batch of concrete is poured, the elastic expansion body 400 is energized by the power-conducting wires on the circuit board. The elastic expansion body 400 is activated and changes from a liquid state to a solid elastic body. The volume of the elastic expansion body 400 increases and gradually pushes up the plunger 200, causing the plunger 200 to move upward relative to the base 100, and then inserting the plunger 200 into the concrete that has not yet solidified.

[0074] First, because the uncured concrete is quite heavy, ordinary elastic bodies cannot be used to support the plunger 200. It is necessary to ensure that the upward expansion force of the elastic expansion body 400 can push the plunger 200 into the uncured concrete and that it remains stationary during the curing process. Second, after pushing the plunger 200 upward, it is also necessary to maintain its rebound capability. After the cured pile moves relative to the rock surface due to external forces, the plunger 200 can move accordingly with the pile, keeping the top of the plunger 200 in contact with the bottom of the pile. Third, the elastic expansion body 400 needs to be activated as needed, and it is necessary to ensure that the elastic expansion body 400 is activated only after the concrete is injected into the pile. Fourth, because the volume of the receiving hole 110 is small, it is difficult to install a linear drive device that can provide sufficient thrust in a confined space.

[0075] In summary, the elastic expansion body 400 needs to be selected from the electro-crosslinked prepolymer of this embodiment, which can be activated at any time by energizing, and the elastic expansion body 400 can provide sufficient support force after changing from liquid to elastic solid to ensure that the plunger 200 is inserted into the uncured concrete.

[0076] The base 100 is placed into the pre-drilled hole in the rock surface below the cast-in-place pile, and the first batch of concrete is injected into the pile. Since the monitoring sensor is entirely within the pre-drilled hole, the injected concrete prevents it from being crushed or damaged. After the first batch of concrete is injected, power is supplied to the conductive wire via the circuit board. This heats and activates the elastic expansion body 400, causing it to transform from a liquid to a solid elastic body and expand. The expanded elastic expansion body 400 then abuts against the bottom of the plunger 200 and the bottom surface of the receiving hole 110 of the base 100, respectively, allowing the top of the plunger 200 to extend upwards into the still-uncured concrete of the cast-in-place pile. The sealing ring 300 can prevent the elastic expansion body of the receiving hole 110 from leaking outward. The sealing ring 300 can also prevent external liquids from entering the receiving hole 110 and contaminating the elastic expansion body 400. The elastic expansion body 400 makes the bottom surface of the base 100 fit tightly against the bottom surface of the reserved hole. After the concrete solidifies, the plunger 200 of the monitoring sensor is firmly fixed to the bottom of the cast-in-place pile. When the cast-in-place pile is under force, the vertical support force is transmitted from the plunger 200 to the pressure sensor 500. The pressure sensor 500 converts the pressure signal into an electrical signal and transmits it to the integrated circuit board to facilitate long-term monitoring of the support force of the cast-in-place pile and realize long-term continuous monitoring of the support force of the cast-in-place pile.

[0077] After the sensor is installed and fixed, when the cast-in-place pile is formed and subjected to force, the various detection elements inside the sensor work together to achieve long-term monitoring of the pile bottom support force and related parameters. The specific principle is as follows.

[0078] Support force monitoring: The pressure sensor 500, which is in contact with the top of the electro-crosslinked prepolymer material, transmits the vertical support force to the pressure sensor 500 when the grouting pile is under force. The pressure sensor 500 converts the pressure signal into an electrical signal and transmits it to the integrated circuit board.

[0079] Displacement monitoring: A telescopic structure is provided between the plunger 200 of the sensor and the base 100. The telescopic dimension is read in real time by the displacement sensor 800. The amount of upward or downward displacement of the cast-in-place pile in the vertical direction can be calculated based on the telescopic dimension data.

[0080] Strain monitoring at the top of the pile: The strain sensor 700 at the top of the plunger 200 is an array-type passive sonar sensor (piezoelectric ceramic array), which can collect strain data at the top of the grouting pile. It optimizes the traditional two-way feedback of strain detection into one-way feedback and the traditional single-linear detection into array scanning, which greatly improves the accuracy and data completeness of strain detection.

[0081] Data processing and transmission: The integrated circuit board (including tilt sensor) inside the plunger 200 integrates various monitoring data such as pressure, displacement, strain, and tilt angle, and transmits the data to the terminal through wires to realize the real-time display, storage and analysis of monitoring data, providing data support for the long-term stability assessment of the pile bottom support force of cast-in-place piles.

[0082] The purpose of this invention is to overcome the shortcomings of existing pile bottom support force monitoring technology and provide a long-term monitoring sensor for pile bottom support force, achieving the following core objectives.

[0083] A robust and rigid connection is achieved between the sensor and the concrete at the bottom of the cast-in-place pile and the pre-reserved hole on the rock surface below the pile, preventing sensor displacement and damage during concrete pouring and ensuring the stability of long-term monitoring.

[0084] The strain detection mode has been optimized by changing the traditional two-way feedback to single-way feedback and the single linear detection to array scanning, which greatly improves the detection accuracy and data completeness.

[0085] Improve the sensor's protective structure to avoid damage to the sensor and wires from the impact of concrete pouring and moisture, thereby extending the sensor's service life.

[0086] It integrates multiple detection functions and simultaneously collects key parameters such as pile bottom support force, vertical displacement, pile inclination angle and pile top strain to achieve long-term comprehensive monitoring of pile bottom support force.

[0087] Easy to install, simplifying the installation process, reducing construction difficulty, and ensuring accurate sensor installation.

[0088] Piston 200: The overall structure is hollow, with an integrated circuit board inside. The integrated circuit board is equipped with an inclination sensor to collect pile inclination data and transmit all monitoring data to the terminal. The top of the plunger 200 is equipped with a strain sensor 700, which is a set of piezoelectric ceramic array passive sonar sensors to collect strain data at the top of the cast-in-place pile, optimizing the traditional strain detection mode. The bottom of the plunger 200 contacts the elastic expansion body 400, and the contact surface is equipped with a pressure sensor 500, which is a piezoelectric ceramic sensor to test the pile bottom support force. A sealing ring 300 is provided between the plunger 200 and the receiving hole 110 of the base 100 to achieve waterproof protection and prevent water from entering the sensor during concrete pouring and damaging the electronic components.

[0089] Base 100: Used to tightly connect with the pre-reserved hole on the rock surface below the bottom of the cast-in-place pile. The base 100 and the plunger 200 cooperate to form a telescopic structure. The telescopic dimension data is read by the displacement sensor 800, and then the vertical displacement of the pile body (floating or sinking) is calculated. The base 100 is designed to adapt to the size of the pre-reserved hole on the rock surface below the bottom of the cast-in-place pile to ensure a tight and stable connection.

[0090] Core material: The sensor has a pre-reserved elastic expansion body 400, which is an electro-crosslinked prepolymer. This material can be activated by passing electricity through a wire. After activation, it changes from a liquid state to a solid elastic body and expands to push the plunger 200 to extend to a preset length, providing power for a firm connection between the sensor and the concrete and the reserved hole.

[0091] Protective tube 600: It adopts a special design to resist the impact of concrete pouring and avoid damage to the top of the sensor by pressure; the wire is placed inside the concrete, and the structural design of the protective tube 600 can effectively protect the wire and ensure that the wire is unobstructed.

[0092] Compared with the prior art, the present invention has the following significant advantages and can effectively solve the defects of existing monitoring technologies.

[0093] The connection is firm and the monitoring is stable: the expansion and change of the elastic expansion body 400 of the electro-crosslinked prepolymer material after being activated by electricity pushes the plunger 200 into the concrete and rigidly connects with the concrete. The base 100 is tightly connected to the reserved hole on the rock surface to avoid sensor displacement and loosening, and ensure the stability of data acquisition during long-term monitoring without external interference.

[0094] High detection accuracy and good data completeness: The pile top strain detection mode is optimized, and an array-type passive sonar sensor is used to realize single-pass feedback and array scanning, replacing the traditional double-pass feedback and single-linear detection, which greatly improves the strain detection accuracy; at the same time, it integrates multi-parameter monitoring functions such as pressure, displacement, and inclination angle, realizing comprehensive acquisition of parameters related to pile bottom support force, and significantly improving data completeness.

[0095] Excellent protective performance and long service life: A sealing ring 300 is provided between the base 100 and the plunger 200 to achieve good waterproof protection; the protective tube 600 is designed to withstand the impact of concrete pouring, avoiding damage to the sensor and wires; the wires are placed inside the concrete, further improving the protective effect, effectively extending the service life of the sensor, and meeting the needs of long-term monitoring.

[0096] Easy to install and compatible with construction techniques: Convenient installation simplifies the installation process and reduces construction difficulty; the design features such as ample wiring allowance and 90-degree lateral opening when the plunger is lifted, making it compatible with concrete pouring processes, avoiding damage to sensors and wiring during construction, and ensuring installation quality.

[0097] Highly practical and widely applicable: It can be widely used for long-term monitoring of pile bottom support force in various cast-in-place pile foundation projects, such as buildings, bridges, and rail transit. It can provide accurate and comprehensive monitoring data for the safe operation of structures and has extremely high engineering practical value.

[0098] Reference Figure 3 As shown, the present invention provides a method for implanting a sensor for long-term monitoring of the bottom support force of a cast-in-place pile.

[0099] The implantation method is used to implant the long-term monitoring sensor of the pile bottom support force of the cast-in-place pile in the above embodiment into the bottom of the cast-in-place pile. The implantation method includes the following steps.

[0100] Step S100: Drill a pre-reserved hole in the rock surface below the cast-in-place pile;

[0101] Step S200: Place the long-term monitoring sensor for the bottom support force of the cast-in-place pile into the reserved hole, with the bottom surface of the base 100 fitting against the bottom surface of the reserved hole.

[0102] Step S300: Concrete is injected into the cast-in-place pile, and the elastic expansion body 400 is energized through the energizing conductor to change the elastic expansion body 400 from a liquid state to a solid elastic body.

[0103] In step S400, after the elastic expansion body 400 expands, it pushes the plunger 200 upward into the concrete. After the elastic expansion body 400 expands, it pushes the bottom surface of the base 100 to fit tightly against the bottom surface of the reserved hole.

[0104] Design a pre-drilled hole in the rock surface below the bottom of the cast-in-place pile, with the hole size matching the sensor base 100; check the performance of each sensor component to ensure that the pressure sensor 500, strain sensor 700, displacement sensor 800, tilt sensor, and integrated circuit board are working properly; check the state of the elastic expansion body 400 to ensure that it is in a liquid and activatable state; prepare the data receiving terminal and complete the equipment debugging.

[0105] Sensor installation: Grab the sensor and accurately insert it into the pre-drilled hole in the rock surface below the bottom of the cast-in-place pile. Adjust the sensor position to ensure that the sensor base is 100% fully fitted into the rock surface, and that the sensor is securely installed without any looseness.

[0106] Wiring arrangement: The sensor wires are laid with a large margin, and the wires are laid along the inside of the pile to ensure smooth wiring without tangling or pulling; check the wire connection points to ensure that the connection is firm and to avoid poor contact affecting power-on activation and data transmission.

[0107] Sensor activation: After the first batch of punched concrete is poured, power is immediately supplied to the elastic expansion body 400 inside the sensor through the wire. The voltage is controlled within the preset range to activate the electro-crosslinked prepolymer material. The sensor's expansion and contraction state is observed to ensure that the electro-crosslinked prepolymer material expands and completes its phase change. The plunger 200 is pushed to extend to the preset length, so that one end of the plunger 200 is embedded in the uncured concrete, and the base 100 is tightly connected to the reserved hole. At this time, the protective tube 600 is opened laterally by 90 degrees due to the frictional resistance of the concrete and the lateral traction of the wire, protecting the wire from pressure damage.

[0108] Concrete solidification and sensor fixation: After the concrete of the cast-in-place pile has solidified, the plunger 200 forms a rigid connection with the concrete, the base 100 remains tightly connected with the reserved hole, the sensor is fixed and installed, and enters the long-term monitoring state.

[0109] Long-term monitoring: After the cast-in-place pile is formed and subjected to force, various components within the sensors begin to work in concert: pressure sensor 500 collects the pressure signal corresponding to the pile bottom support force, displacement sensor 800 collects the expansion and contraction dimension data of the plunger and base (converted displacement), tilt sensor collects the pile tilt angle data, and strain sensor 700 collects the pile top strain data; all monitoring data are integrated through an integrated circuit board and transmitted to the terminal via wires. The terminal analyzes, stores, and displays the data, providing real-time feedback on the long-term changes in the pile bottom support force, thus providing a basis for engineering safety assessment.

[0110] The embodiments of the present invention have been described in detail above with reference to the accompanying drawings. However, the present invention is not limited to the above embodiments. Within the knowledge possessed by those skilled in the art, various changes can be made without departing from the spirit of the present invention.

Claims

1. A long-term monitoring sensor for the bottom support force of cast-in-place piles, characterized in that, include: The base has a receiving hole at the top, and the base is used to be inserted into a reserved hole in the rock surface below the cast-in-place pile; A plunger slides up and down through the receiving hole, with the top of the plunger extending above the base. The plunger has an installation cavity inside, and the top of the plunger is used to extend into the bottom of the grouting pile. A sealing ring is disposed between the outer side wall of the plunger and the inner side wall of the receiving hole, and the sealing ring seals the gap between the plunger and the receiving hole; An elastic expansion body is disposed in the receiving hole. The elastic expansion body is located below the plunger. The elastic expansion body is an electro-crosslinked prepolymer. After being activated by electric heating, the elastic expansion body changes from a liquid state to a solid elastomer and expands its own volume. The expanded elastic expansion body pushes the plunger and the base away from each other. A pressure sensor is located at the bottom of the plunger, and the pressure sensor abuts against the elastic expansion body; A circuit board is disposed in the mounting cavity, the circuit board is electrically connected to the pressure sensor, the circuit board is provided with a power-conducting wire, the power-conducting wire extends into the receiving hole, and the power-conducting wire is electrically connected to the elastic expansion body; A displacement sensor is disposed between the plunger and the receiving hole, and the displacement sensor measures the distance the plunger moves relative to the receiving hole.

2. The long-term monitoring sensor for the pile bottom support force of cast-in-place piles according to claim 1, characterized in that, The elastic expander includes a prepolymer and a conductive filler, wherein the prepolymer and the conductive filler are uniformly mixed.

3. The long-term monitoring sensor for the pile bottom support force of cast-in-place piles according to claim 2, characterized in that, The prepolymer is a polyurethane prepolymer.

4. The long-term monitoring sensor for the bearing capacity of cast-in-place piles according to claim 1, characterized in that, The long-term monitoring sensor for the pile bottom support force of the grouting pile also includes: An electrical connection wire is electrically connected to the circuit board, extending upwards from the plunger to above the grouting pile.

5. The long-term monitoring sensor for the pile bottom support force of cast-in-place piles according to claim 4, characterized in that, The long-term monitoring sensor for the pile bottom support force of the grouting pile also includes: A protective tube is hinged to the outer wall of the plunger, the protective tube protrudes outward from the plunger, and the electrical connection wire passes through the protective tube.

6. The long-term monitoring sensor for the pile bottom support force of cast-in-place piles according to claim 5, characterized in that, The long-term monitoring sensor for the pile bottom support force of the grouting pile also includes: The terminal is electrically connected to the circuit board via the electrical connection line, and the circuit board sends the pressure value measured by the pressure sensor to the terminal in real time.

7. The long-term monitoring sensor for the pile bottom support force of cast-in-place piles according to claim 1, characterized in that, The long-term monitoring sensor for the pile bottom support force of the grouting pile also includes: An inclination sensor is disposed in the mounting cavity, and the inclination sensor is used to measure the angle at which the plunger tilts as the grouting pile tilts.

8. The long-term monitoring sensor for the pile bottom support force of cast-in-place piles according to claim 1, characterized in that, The long-term monitoring sensor for the pile bottom support force of the grouting pile also includes: A strain sensor is located on top of the plunger.

9. A method for implanting a sensor for long-term monitoring of the bearing capacity at the bottom of a cast-in-place pile, characterized in that, For implanting a long-term monitoring sensor for the pile bottom support force of a cast-in-place pile as described in any one of claims 1 to 8, the implantation method includes: Drill a pre-reserved hole in the rock surface below the cast-in-place pile; The long-term monitoring sensor for the pile bottom support force of the cast-in-place pile is placed in the reserved hole, and the bottom surface of the base is in contact with the bottom surface of the reserved hole; Concrete is injected into the cast-in-place pile, and electricity is supplied to the elastic expansion body through the energized conductor to change the elastic expansion body from a liquid state to a solid elastic body; After the elastic expansion body expands, it pushes the plunger upward into the concrete, and after the elastic expansion body expands, it pushes the bottom surface of the base to fit tightly against the bottom surface of the reserved hole.

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