A concrete pile crack monitoring device and a monitoring method thereof

Abstract

The application discloses a concrete pile crack monitoring device and a monitoring method thereof, and relates to the technical field of concrete pile foundation crack monitoring. The device comprises a signal generating module, a signal collecting module and a piezoelectric ceramic sheet. The signal generating module comprises a signal generating device and an amplifying device, and the signal generating device and the amplifying device are electrically connected. The piezoelectric ceramic sheet is fixed on a steel reinforcement cage. The positive electrode of the piezoelectric ceramic sheet is connected to one end of a positive electrode lead wire. The other end of the positive electrode lead wire, which is away from the piezoelectric ceramic sheet, can be electrically connected to the amplifying device and the signal collecting module respectively. The negative electrode of the piezoelectric ceramic sheet is connected to one end of a negative electrode lead wire. The other end of the negative electrode lead wire, which is away from the piezoelectric ceramic sheet, can be electrically connected to the amplifying device and the signal collecting module respectively. The monitoring method comprises preparing the piezoelectric ceramic sheet, pouring the concrete pile, initial measurement and calibration and active monitoring. The application can accurately reflect whether the crack exists, the position of the crack from the sensor and the crack width change by only setting one piezoelectric ceramic sheet.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of concrete pile crack monitoring, and particularly relates to a concrete pile crack monitoring device and a monitoring method thereof. BACKGROUND

[0002] The foundation is a key load-bearing component in the building structure, which bears the vertical static load and dynamic load such as wind load, earthquake load transmitted by the upper structure, and plays an important role in supporting the upper structure and ensuring the normal use and operation of the structure in the life cycle. However, crack damage is widespread in concrete structures, and pile foundation as a key load-bearing component is no exception. Serious cracks can deteriorate the strength and stability of the concrete structure, damage its integrity and impermeability, greatly reduce the bearing capacity of the structure, and endanger the safe operation of the overall structure; slight cracks can affect the durability of the pile foundation, and may subsequently develop into cracks that endanger the safety of the upper structure. In order to avoid damage to the upper structure without any warning, the demand for actively monitoring the cracks of the concrete pile foundation arises at the historic moment. Through monitoring the cracks, the initial damage can be discovered in time to provide data for subsequent related decisions such as reinforcement, repair, and even demolition, thereby maintaining the normal and safe operation of the overall structure, prolonging the service life of the structure and reducing the life cycle cost.

[0003] At present, common pile foundation health monitoring methods include corrosion degree monitoring using resistance probes and pH, ion probes, crack and strain monitoring using fiber Bragg gratings, crack monitoring using electromagnetic waves, and crack loss monitoring using piezoelectric ceramics as a representative of ultrasonic wave means. Recently, piezoelectric intelligent materials represented by piezoelectric ceramics have been increasingly studied in the field of civil engineering health monitoring. They have the advantages of easy processing, light weight, low cost, high bandwidth, and can realize real-time monitoring of the structure. In particular, piezoelectric ceramics have become a research hotspot in the field of crack damage monitoring of concrete structures. Piezoelectric effect is an important characteristic of piezoelectric materials: positive piezoelectric effect refers to the relative movement of positive and negative charges inside the piezoelectric element to produce polarization when mechanical deformation is applied to the piezoelectric element, resulting in the appearance of bound charges with opposite signs on the two surfaces of the element, and the charge density is proportional to the external force, which reflects the ability of piezoelectric materials to convert mechanical energy into electrical energy; conversely, the inverse piezoelectric effect refers to the relative displacement of positive and negative charges inside the piezoelectric element due to the application of voltage on the two surfaces of the piezoelectric element, which causes the deformation of the piezoelectric element, reflecting the ability of piezoelectric materials to convert electrical energy into mechanical energy. By utilizing the piezoelectric effect, piezoelectric materials can be made into sensors with signal transmission and signal reception dual functions. By burying the sensors in the concrete pile foundation component, the crack damage of the component can be monitored, and the changes in the ultrasonic waves received by the sensors before and after the component is damaged can be used to infer the damage.

[0004] The prior art needs a pair of piezoelectric ceramic sensors as a transmitting end and a receiving end respectively, both of which need to be intact to work normally, which means a high failure probability; and the two piezoelectric ceramic sensors need to be arranged on the steel bar net respectively, which is difficult to arrange; in addition, the prior art mainly monitors whether a crack exists and the crack development width, but cannot monitor the specific depth of the crack position.

[0005] Therefore, there is an urgent need in the art for a concrete pile crack monitoring device and a monitoring method thereof to solve the above problems. SUMMARY

[0006] The purpose of the present application is to provide a concrete pile crack monitoring device and a monitoring method thereof to solve the above technical problems in the prior art, which can accurately reflect whether a crack exists, the crack distance from the sensor and the crack development width change by only setting one piezoelectric ceramic sheet, has good stability and durability, and has less manual workload and lower damage probability.

[0007] To achieve the above purpose, the present application provides the following solutions:

[0008] The present application discloses a concrete pile crack monitoring device, comprising a signal generating module, a signal collecting module and a piezoelectric ceramic sheet, the signal generating module comprises a signal generating device and an amplifying device, the signal generating device and the amplifying device are electrically connected, the piezoelectric ceramic sheet is fixed on a steel cage, the positive electrode of the piezoelectric ceramic sheet is connected to one end of a positive electrode lead wire, the other end of the positive electrode lead wire away from the piezoelectric ceramic sheet can be electrically connected to the amplifying device and the signal collecting module respectively, the negative electrode of the piezoelectric ceramic sheet is connected to one end of a negative electrode lead wire, the other end of the negative electrode lead wire away from the piezoelectric ceramic sheet can be electrically connected to the amplifying device and the signal collecting module respectively.

[0009] Preferably, the signal generating device is a waveform generator, and the amplifying device is a voltage amplifier.

[0010] Preferably, the signal collecting module is a personal computer, and the personal computer comprises a signal acquisition card, which is used for signal acquisition.

[0011] Preferably, the positive electrode lead wire and the negative electrode lead wire are both electromagnetic shielding wires.

[0012] Preferably, waterproof layers are arranged on both sides of the piezoelectric ceramic sheet, and the waterproof layers are made of epoxy resin.

[0013] Preferably, a protective layer is arranged on the side of the waterproof layer away from the piezoelectric ceramic sheet, and the protective layer is made of mortar.

[0014] The application discloses a monitoring method of a concrete pile crack monitoring device, and comprises the following steps.

[0015] Step one, piezoelectric ceramic sheet preparation: an anode wire and a cathode wire are welded on the anode and cathode of the piezoelectric ceramic sheet respectively; a waterproof layer is applied on the two sides of the piezoelectric ceramic sheet, and then the piezoelectric ceramic sheet is dried; and then a protective layer is poured on the two sides of the piezoelectric ceramic sheet;

[0016] Step two, concrete pile pouring: the piezoelectric ceramic sheet is fixed on the upper part of the steel reinforcement cage, the anode wire and the cathode wire are led out along the steel reinforcement cage, the steel reinforcement cage is sunk into the pile foundation hole, and the concrete is poured;

[0017] Step three, initial measurement and calibration: after the reinforced concrete pile is finally cured, the actual wave speed v is measured by using an ultrasonic wave speed instrument, the anode wire and the cathode wire are connected with an amplification device and a signal collection module respectively, an isolated wave is generated by using a signal generator, and the wave path is calculated by using the time delay t0 of the transmitted wave and the reflected wave;

[0018] Step four, active monitoring: after a period of time, an isolated wave is transmitted, and a reflected signal is received; if the time delay t changes, it means that a crack appears at a certain position of the lower part of the pile foundation, the crack position s can be calculated by using the time delay and the wave speed, and the reflected wave amplitude A is recorded; after a period of time, if the time delay t does not change but the amplitude changes, it means that the proportion of ultrasonic wave transmission and reflection changes, that is, the crack development width changes.

[0019] The application has the following technical effects compared with the prior art.

[0020] The application can transmit an isolated wave by using a signal generation module, collect relevant data by using a signal collection module, and analyze whether a crack exists, the position of the crack from the sensor, and the crack development width change by using the collected relevant data, and has good stability and durability.

[0021] In addition, since only one piezoelectric ceramic sheet is arranged in the application, the artificial workload is smaller, and the damage probability is lower. DETAILED DESCRIPTION

[0022] In order to more clearly illustrate the technical solutions in the embodiments of the application or the prior art, the following will briefly introduce the drawings needed to be used in the embodiments. Obviously, the drawings in the following description only show some embodiments of the application, and for those skilled in the art, other drawings can also be obtained from these drawings without creative labor.

[0023] Figure 1 It is a structural schematic diagram of the concrete pile crack monitoring device in the embodiments of the application.

[0024] Figure 2 This refers to the signal characteristics of the intact state of the concrete pile in the embodiments of the present invention;

[0025] Figure 3 This is a schematic diagram of a concrete pile with cracks according to an embodiment of the present invention;

[0026] Figure 4 The signal characteristics of a crack state in the embodiments of the present invention;

[0027] In the diagram: 1-Signal generation module; 2-Signal collection module; 3-Piezoelectric ceramic sheet; 4-Electromagnetic shielding wire; 5-Ultrasonic wave. Detailed Implementation

[0028] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0029] The purpose of this invention is to provide a concrete pile crack monitoring device and method to solve the technical problems existing in the prior art. It only requires a piezoelectric ceramic plate to accurately reflect the existence of cracks, the position of cracks from the sensor, and the changes in crack width. It has good stability and durability, and requires less manual work and has a lower probability of damage.

[0030] To make the above-mentioned objects, features and advantages of the present invention more apparent and understandable, the present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments.

[0031] Example 1

[0032] like Figure 1 As shown, this embodiment provides a concrete pile crack monitoring device, including a signal generation module 1, a signal collection module 2, and a piezoelectric ceramic sheet 3. The signal generation module 1 includes a signal generating device and an amplification device, which are electrically connected. The amplification device amplifies the signal intensity and increases the propagation distance of the ultrasonic wave. The piezoelectric ceramic sheet 3 is fixed to the reinforcing cage, specifically placed horizontally along its thickness direction. The positive electrode of the piezoelectric ceramic sheet 3 is connected to one end of a positive electrode wire. The end of the positive electrode wire away from the piezoelectric ceramic sheet 3 is split into two, each electrically connected to the amplification device and the signal collection module 2, respectively. The negative electrode of the piezoelectric ceramic sheet 3 is connected to one end of a negative electrode wire. The end of the negative electrode wire away from the piezoelectric ceramic sheet 3 is also split into two, each electrically connected to the amplification device and the signal collection module 2, respectively.

[0033] In actual use, a solitary wave is emitted by the signal generating module 1, and then the signal collecting module 2 is used to collect the signal, and the existence of the crack, the position of the crack from the sensor, and the change in the width of the crack can be calculated and analyzed according to the collected data.

[0034] In this embodiment, the signal generating device uses an existing waveform generator to emit a solitary wave. The amplification device is a voltage amplifier, which amplifies the signal strength and increases the propagation distance of the ultrasonic wave 5.

[0035] In this embodiment, the signal collecting module 2 is a personal computer (also known as a personal computer or PC), which includes a signal acquisition card for collecting signals and performing noise reduction processing through the personal computer. The specific conditions of the crack can be determined by the time delay and amplitude change of the reflected wave.

[0036] In this embodiment, the positive and negative leads are both electromagnetic shielding wires 4, which are used to transmit the emitted and reflected signals and effectively avoid interference from other electromagnetic signals.

[0037] In this embodiment, the upper and lower surfaces of the piezoelectric ceramic sheet 3 are provided with a 0.5mm-thick waterproof layer made of epoxy resin, which prevents water from coming into contact with the piezoelectric ceramic sheet 3.

[0038] In this embodiment, a 10mm-thick protective layer made of high-grade mortar is provided on the side of the waterproof layer away from the piezoelectric ceramic sheet 3, which protects the piezoelectric ceramic sheet 3 from damage caused by external stones or other objects.

[0039] Embodiment Two

[0040] The monitoring method of the concrete pile crack monitoring device provided in this embodiment is based on the concrete pile crack monitoring device disclosed in Embodiment One, and includes the following steps:

[0041] Step One: Prepare the piezoelectric ceramic sheet 3. Weld the positive and negative leads to the positive and negative electrodes of the piezoelectric ceramic sheet 3, respectively. Apply a 0.5mm-thick waterproof layer to the upper and lower surfaces of the piezoelectric ceramic sheet 3 and let it dry. Then, pour a 10mm-thick protective layer on both sides of the piezoelectric ceramic sheet 3.

[0042] Step Two: Pour the concrete pile. Fix the piezoelectric ceramic sheet 3 horizontally along the thickness direction at the upper part of the steel reinforcement cage, specifically at the 1 / 3 position of the pile height (1 / 3 from the top). The ends of the positive and negative leads away from the piezoelectric ceramic sheet 3 are led out along the steel reinforcement cage. Sink the steel reinforcement cage into the pile foundation hole and pour the concrete.

[0043] Step 3, Initial Calibration: After the reinforced concrete pile has fully set, the actual wave velocity v is measured using an ultrasonic 5-velocity meter. In general, it is approximately 3000 m / s in concrete. The positive and negative leads are connected to the amplification device and signal collection module 2, respectively. An isolated wave is generated by the signal generator. The wave path is calculated using the time delay t0 of the transmitted and received reflected waves. Theoretically, it should be twice the distance from the piezoelectric ceramic plate 3 to the pile bottom, i.e., 4 / 3 times the pile length. An ultrasonic wave propagating 40 meters in concrete will gradually weaken to 1 / 1000 of its amplitude. An input amplitude of 50 volts can still receive an echo of 50 millivolts, which is within the identifiable range. Therefore, the applicable maximum pile length is 30 meters.

[0044] Step 4, Active Monitoring: Monitor at intervals by emitting an isolated wave and receiving the reflected signal. If the time delay t changes, it indicates a crack has appeared at a certain point in the lower part of the pile foundation. The crack location s can be calculated using the time delay and wave velocity, and the amplitude A of the reflected wave can be recorded. Monitor again at intervals. If the time delay t remains unchanged but the amplitude changes, it indicates a change in the ratio of ultrasonic wave transmission and reflection, meaning the crack width has changed.

[0045] Example 3

[0046] like Figures 1-4 As shown in the figure, this embodiment provides actual working data of a monitoring method for a concrete pile crack monitoring device, including the following steps:

[0047] First, crack monitoring was carried out on a bored pile with a diameter of 0.6 meters and a length of 30 meters. The concrete grade was C30, the main reinforcement was HRB400, and the stirrups were HPB300.

[0048] Step 1: Preparation of piezoelectric ceramic sheet 3: Select a 40×40×0.6 mm square PZT-5 piezoelectric ceramic sheet. Take two 11-meter-long electromagnetic shielding wires 4 as the positive and negative conductors, respectively, and weld one end of each conductor to both sides of the piezoelectric ceramic sheet 3. Apply a 0.5 mm thick epoxy resin waterproof layer to both sides of the piezoelectric ceramic sheet 3 and let it stand in a cool, ventilated place for 1 day to dry and harden. Using a custom mold, pour a 10 mm thick M35 mortar protective layer, place it in a curing chamber, cure for 1 day, demold, and then cure for another 7 days.

[0049] Step 2, Concrete Pile Casting: After drilling is completed on site, the piezoelectric ceramic plate 3 is tied to the reinforcing cage, 20 meters from the bottom of the pile and 10 meters from the ground; two electromagnetic shielding wires 4 are led upwards along the reinforcing cage. The reinforcing cage is then lowered into the pile hole, and concrete is poured, waiting 28 days for it to fully harden.

[0050] Step three, initial calibration: using the ultrasonic 5-speed instrument to measure the actual wave speed, which is 3000 m / s; using MATLAB software to generate an isolated sine wave with an amplitude of 5V, a frequency of 10 kHz, and a magnification of 10 times; connecting the electromagnetic shielding wire 4 and the signal generation module 1 and the signal collection module 2, the signal generation module 1 emits an isolated wave, and the signal collection module 2 receives the reflected wave and filters it, and verifies whether the echo time delay t0 is The intact state of the concrete pile is shown in Figure 1 The signal characteristics of the intact state are shown in Figure 2 If the time delay t is too low, there may be cracks.

[0051] Step four, active monitoring: after a period of time, the second monitoring is performed, the electromagnetic shielding wire 4 is connected with the signal generation module 1 and the signal collection module 2, an isolated sine wave is emitted with an amplitude of 5V, a frequency of 10 kHz, and a magnification of 10 times; if the time delay is unchanged, it can be considered that no new cracks are generated; if the time delay is reduced, the specific position of the crack can be calculated; if the time delay t1 is 0.0067 seconds in this monitoring, then s1=v×t1 / 2=3000 m / s×0.0067 s / 2=10 m, the crack distance from the piezoelectric ceramic sheet 3 is 10 m, i.e. 20 m from the ground. The crack state of the concrete pile is shown in Figure 3 The signal characteristics of the crack state are shown in Figure 4 At the same time, the amplitude A1 is recorded.

[0052] If in the third monitoring, t2=t1, and A2 is larger than A1, it indicates that the reflected energy increases and the transmitted energy decreases, which means that the ultrasonic wave 5 is more and more unable to pass through the crack, i.e. the crack width is qualitatively judged to be larger.

[0053] In the specification, specific examples are applied to explain the principles and implementation modes of the present application, and the above examples are only used to help understand the method of the present application and its core idea; at the same time, for those skilled in the art, according to the idea of the present application, the specific implementation mode and application range will be changed. In view of the above, the content of the specification should not be understood as a limitation of the present application.

Claims

1. A monitoring method for a concrete pile crack monitoring device, characterized in that, The invention includes a concrete pile crack monitoring device, comprising a signal generation module, a signal collection module, and a piezoelectric ceramic plate. The signal generation module includes a signal generating device and an amplification device, which are electrically connected. The piezoelectric ceramic plate is fixed to a reinforcing cage. The positive electrode of the piezoelectric ceramic plate is connected to one end of a positive electrode wire, and the end of the positive electrode wire away from the piezoelectric ceramic plate can be electrically connected to both the amplification device and the signal collection module. The negative electrode of the piezoelectric ceramic plate is connected to one end of a negative electrode wire, and the end of the negative electrode wire away from the piezoelectric ceramic plate can be electrically connected to both the amplification device and the signal collection module. Includes the following steps: Step 1, Preparation of piezoelectric ceramic sheet: Solder the positive electrode wire and the negative electrode wire to the positive electrode and negative electrode of the piezoelectric ceramic sheet respectively; apply a waterproof layer to both sides of the piezoelectric ceramic sheet and let it dry; then cast a protective layer on both sides of the piezoelectric ceramic sheet. Step 2, pour concrete pile: Fix the piezoelectric ceramic sheet to the upper part of the reinforcing cage, lead the positive and negative wires out along the reinforcing cage, sink the reinforcing cage into the pile foundation hole, and pour concrete. Step 3, Initial Measurement and Calibration: After the reinforced concrete pile has set, use an ultrasonic velocimeter to measure the actual wave velocity v. Connect the positive and negative conductors to the amplification device and the signal collection module, respectively. Generate an isolated wave through the signal generator. Calculate the wave path by the time delay t0 of the transmitted wave and the received reflected wave. Step 4, Active Monitoring: Monitor at intervals by transmitting an isolated wave and receiving the reflected signal. If the time delay t changes, it indicates that a crack has appeared at a certain point in the lower part of the pile foundation. The location s of the crack can be calculated by the time delay and wave velocity, and the amplitude of the reflected wave A can be recorded. Monitor at another interval. If the time delay t remains unchanged but the amplitude changes, it indicates that the ratio of ultrasonic transmission and reflection has changed, that is, the crack width has changed.

2. The monitoring method of the concrete pile crack monitoring device according to claim 1, characterized in that: The signal generating device is a waveform generator, and the amplification device is a voltage amplifier.

3. The monitoring method of the concrete pile crack monitoring device according to claim 1, characterized in that: The signal acquisition module is a personal computer, which includes a signal acquisition card used to acquire signals.

4. The monitoring method of the concrete pile crack monitoring device according to claim 1, characterized in that: Both the positive and negative conductors are electromagnetically shielded wires.

5. The monitoring method of the concrete pile crack monitoring device according to claim 1, characterized in that: The piezoelectric ceramic sheet has a waterproof layer on both sides, and the waterproof layer is made of epoxy resin.

6. The monitoring method of the concrete pile crack monitoring device according to claim 5, characterized in that: The waterproof layer has a protective layer on the side away from the piezoelectric ceramic sheet, and the protective layer is made of mortar.

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