A built-in confining pressure measuring device for restraining a concrete structure and a confining pressure quantification monitoring method

Abstract

This invention belongs to the field of civil engineering structural monitoring technology, and discloses a built-in confining pressure measuring device and a method for quantitative monitoring of confined concrete structures. It solves the problems of indirect confining pressure acquisition, large measurement errors, and difficulty in accurately characterizing the failure stage in existing technologies. The device includes data acquisition and analysis equipment, a vertical protective support structure, a confining pressure measuring unit, and an external constraint component. The external constraint component is located on the outside of the vertical protective support structure, and core concrete is poured inside the vertical protective support structure. The confining pressure measuring unit is located on the inside of the vertical protective support structure and connected to the data acquisition and analysis equipment. The confining pressure measuring unit includes a micro pressure gauge, a circumferential protective structure, and an auxiliary force transmission and leveling device. The bottom of the circumferential protective structure is in contact with the inner wall of the vertical protective support structure, and the auxiliary force transmission and leveling device is located on the pressure-bearing surface of the micro pressure gauge. This invention enables direct and continuous monitoring of confining pressure in confined concrete structures.

Description

Technical Field

[0001] This invention belongs to the field of civil engineering structure monitoring technology, and particularly relates to a built-in confining pressure measuring device and a method for quantitative monitoring of confining pressure in confined concrete structures. Background Technology

[0002] During the stress process, confined concrete structures experience lateral expansion or contraction of the core concrete, while external confining members exert radial restraint, placing the core concrete in a triaxial stress state. The level of confining pressure and its development directly affect the load-bearing capacity, deformation performance, ductility characteristics, and failure mode of confined concrete structures. Therefore, confining pressure is a core and key factor in studying the stress performance and confinement mechanism of confined concrete structures.

[0003] In the existing technology, the acquisition of confining pressure of confined concrete structures is mostly carried out by external surface strain testing, theoretical conversion, empirical formula inversion or numerical simulation indirect analysis. Although the above methods can reflect the confinement effect to a certain extent, they still have the following shortcomings: (1) The existing methods mostly measure the surface strain of the external confining member or the indirect derivation results, which are difficult to directly reflect the confining pressure level at the measuring point of the monitoring object; (2) In the initial stage of stress, the transition stage and the failure stage, the confining pressure change has obvious nonlinear and abrupt characteristics, and the traditional external strain method is difficult to accurately characterize its evolution law throughout the process; (3) If the pressure sensor is directly placed inside the confining system, the measurement accuracy is easily affected by factors such as difficulty in fixing the sensor, poor surface fitting, uneven local stress transmission and random contact of aggregate particles; (4) The supporting member used to install the sensor itself has a certain stiffness, which may have an additional confining effect on the core concrete, thereby interfering with the actual confining pressure monitoring results.

[0004] Therefore, there is an urgent need to provide a built-in confining pressure measurement device and a quantitative monitoring method for confining pressure that can directly measure, continuously monitor, and monitor the entire process of confining pressure in confined concrete structures, so as to overcome the shortcomings of existing technologies, such as indirect acquisition of confining pressure, large measurement errors, and difficulty in accurately characterizing the failure stage. Summary of the Invention

[0005] One objective of this invention is to provide a built-in confining pressure measuring device for constrained concrete structures, which effectively solves the problems of indirect acquisition of confining pressure, large measurement errors, and difficulty in accurately characterizing the failure stage in the prior art.

[0006] To solve the above-mentioned technical problems, the technical solution adopted by the present invention is as follows: An embedded confining pressure measuring device for confining concrete structures includes a data acquisition and analysis device, a vertical protective support structure, a confining pressure measuring unit, and an external constraint component. The external constraint component is located on the outside of the vertical protective support structure, and the interior of the vertical protective support structure is filled with core concrete. The confining pressure measuring unit is located on the inner wall of the vertical protective support structure and connected to the data acquisition and analysis device. The confining pressure measuring unit includes a micro pressure gauge, a circumferential protective structure, and an auxiliary force transmission and leveling device. The circumferential protective structure is located on the outside of the micro pressure gauge, and its bottom is in contact with the inner wall of the vertical protective support structure. The auxiliary force transmission and leveling device is located on the pressure-bearing surface of the micro pressure gauge.

[0007] Furthermore, the vertical protective support structure has non-through interval slots along the vertical direction, and the interval slots are filled with low-rigidity material.

[0008] Furthermore, the confining pressure measurement unit is installed at a predetermined monitoring position on the vertical protective support structure. The predetermined monitoring position is a part of the monitoring object that is subjected to greater force, a part where the cross-section changes, or a part where the constraint effect changes.

[0009] Furthermore, there are multiple confining pressure measuring units, each set at the same horizontal height and evenly distributed circumferentially on the same horizontal cross section.

[0010] Furthermore, an assembly gap is reserved between the circumferential protective structure and the micro pressure gauge, and epoxy resin adhesive, elastic filler material or gasket is used for filling and limiting treatment.

[0011] Furthermore, the auxiliary force transmission and leveling device employs elastic shims, flexible shims, or compressible leveling layers that match the size of the micro pressure gauge, to ensure that the radial force applied by the core concrete is uniformly transmitted to the micro pressure gauge.

[0012] Furthermore, the external constraint component is made of fiber composite material winding layer, metal sleeve, fiber composite material sleeve or polymer material constraint cylinder.

[0013] Furthermore, the low-stiffness material is a foamed filler or an elastic sealing material.

[0014] Another objective of this invention is to provide a method for quantitative monitoring of confining pressure in confined concrete structures, employing the built-in confining pressure measuring device for confined concrete structures described in the above embodiments, comprising the following steps: S1, preparing a vertical protective support structure and opening interval slots in the vertical protective support structure, then filling the interval slots with a low-stiffness material; S2, setting an external constraint member on the outside of the vertical protective support structure; S3, installing a confining pressure measuring unit at a predetermined monitoring position on the inner wall of the vertical protective support structure, the micro pressure gauge of the confining pressure measuring unit being connected to a data acquisition and analysis device; S4, sealing the bottom of the vertical protective support structure. S5. Before the object is subjected to force, the micro pressure gauge is calibrated to establish the correspondence between the output electrical signal and the pressure value. S6. During the stress process of the monitored object, the confining pressure electrical signal and the corresponding axial load, axial stress or axial strain data are collected synchronously according to the preset time interval or preset sampling frequency, and the confining pressure electrical signal is continuously recorded. S7. The confining pressure value at each monitoring position is calculated based on the confining pressure electrical signal, and the development curve of the entire confining pressure process and the correspondence between the confining pressure and the axial load, axial stress or axial strain are formed.

[0015] Furthermore, in step S2, the external constraint components are installed on the outside of the vertical protective support structure by means of wrapping, pasting, fitting, prefabricating wrapping, or combination installation.

[0016] Compared with the prior art, the beneficial technical effects of the present invention are: (1) The present invention sets the circumferential protective structure, micro pressure gauge and auxiliary force transmission leveling device between the inner wall of the vertical protective support structure and the core concrete, which can sense the radial action applied to the measuring point when the core concrete is subjected to force and generates lateral expansion or contraction, and obtain the confining pressure information at the corresponding measuring point after calibration. Compared with the corresponding transformation calculation method, it has stronger directness and higher accuracy, and can obtain the whole process development information of confining pressure from the elastic stage to the final failure stage.

[0017] (2) By setting up a low-stiffness, low-modulus vertical protective support structure and a spacer groove structure, the present invention enables the vertical protective support structure to meet the installation and fixing requirements of the confining pressure measurement unit while reducing the additional constraint effect on the core concrete, thereby reducing the interference on the confining pressure monitoring results.

[0018] (3) By setting a protective shell with an arc-shaped fitting surface at the bottom and an auxiliary force transmission and leveling device, the present invention can improve the force transmission state on the arc-shaped installation interface, so that the radial force applied by the core concrete can be transmitted to the micro pressure gauge more evenly, reducing the measurement error of confining pressure caused by poor surface fitting, local aggregate protrusion, random particle contact and uneven surface, thereby improving the accuracy of confining pressure acquisition.

[0019] (4) By reasonably limiting the size of the micro pressure gauge and optimizing the assembly interval and processing method between the circumferential protection structure and the micro pressure gauge, this invention can avoid the problem of difficult installation and arrangement caused by the micro pressure gauge being too large, and also avoid the problems of unstable force, swaying and offset, local gaps and discontinuous stress transmission caused by the size being too small or the assembly interval being too large, thereby further improving the installation reliability and measurement stability of the confining pressure measurement unit.

[0020] (5) The present invention can realize continuous monitoring and full-process characterization of confining pressure in confined concrete structures. A single micro pressure gauge can obtain the full-process development curve of confining pressure at the corresponding measuring point; when multiple micro pressure gauges are set, the full-process development curve of confining pressure at each measuring point at different circumferential positions can also be obtained, which can be used to analyze the evolution characteristics of confining pressure and its circumferential distribution law.

[0021] (6) This invention is not limited to a single type of external constraint component and has a wide range of applications. It can be used for direct quantitative monitoring of confining pressure of confined concrete structures or monitoring objects under fiber composite material constraints, sleeve constraints and other external constraints. It can also provide a basis for the study of mechanical properties of confined concrete structures, stress mechanism analysis and the establishment of related constitutive models. Attached Figure Description

[0022] Figure 1 This is a schematic diagram of the overall structure of the built-in confining pressure measuring device of the present invention, wherein the arrow indicates the pressure direction of the monitored object.

[0023] Figure 2 This is a schematic diagram of the vertical protective support structure of the present invention.

[0024] Figure 3 This is an exploded structural diagram of the confining pressure measuring unit of the present invention.

[0025] Figure 4 This is a schematic diagram of the installation arrangement of the confining pressure measuring unit of the present invention.

[0026] Figure 5 This is a cross-sectional view of the confined concrete monitoring object in Example 2.

[0027] Figure 6 This is a schematic diagram of the longitudinal structure of the confined concrete monitoring object in Example 2.

[0028] Explanation of reference numerals in the attached drawings: Data acquisition and analysis equipment-1; Vertical protective support structure-2; Confining pressure measurement unit-3; External constraint component-4; Core concrete-5; Spacing groove-6; Miniature pressure gauge-7; Circumferential protective structure-8; Auxiliary force transmission and leveling device-9; Wire lead-out hole-10; Low stiffness material-11. Detailed Implementation

[0029] Example 1: A built-in confining pressure measuring device for confined concrete structures, such as Figure 1 As shown, the system includes a data acquisition and analysis device 1, a vertical protective support structure 2, a confining pressure measurement unit 3, and an external constraint member 4. The vertical protective support structure 2 provides a foundation for the installation and fixing of the confining pressure measurement unit 3 and a foundation for the installation of the external constraint member 4. Specifically, the external constraint member 4 is located on the outside of the vertical protective support structure 2 during use (i.e., the external constraint member 4 only needs to be located on the outside of the vertical protective support structure 2 when the device is actually monitoring or under stress), providing circumferential constraint on the core concrete 5. The core concrete 5 is poured inside the vertical protective support structure 2. The confining pressure measurement unit 3 is located on the inner wall of the vertical protective support structure 2, between the vertical protective support structure 2 and the core concrete 5. The confining pressure measurement unit 3 is electrically connected to the data acquisition and analysis device 1. When the core concrete 5 is subjected to force and undergoes lateral expansion or contraction, the miniature pressure gauge 7 in the confining pressure measurement unit 3 senses the radial force applied by the core concrete 5 and converts it into an electrical signal, which is transmitted to the data acquisition and analysis device 1. The electrical signal is calibrated and converted into the confining pressure value at the monitoring location.

[0030] like Figure 2 As shown, the vertical protective support structure 2 can be a PVC cylinder, a polymer thin-walled cylinder, a composite material thin-walled cylinder, or other low-stiffness, low-modulus thin-walled cylindrical structure. In this embodiment, the vertical protective support structure 2 uses a low-stiffness, low-modulus PVC cylinder as the mounting carrier for the confining pressure measurement unit 3 and provides a supporting foundation for the external constraint member 4. The vertical protective support structure 2 has an inner diameter of 200mm, a wall thickness of 3mm, and a height of 600mm. Since the vertical protective support structure 2 itself has a certain stiffness, if it is directly subjected to stress in the form of a complete cylinder, it may form an additional constraint on the core concrete 5, thereby affecting the confining pressure monitoring results. Therefore, non-through interval slots 6 are opened along the axial direction on the vertical protective support structure 2. The width of the interval slots 6 is 3-10mm, the length is 70%-95% of the height of the vertical protective support structure 2, the depth of the slots is the same as or close to the wall thickness of the vertical protective support structure 2, and ungrooved areas are reserved at the upper and lower ends of the vertical protective support structure 2. In this embodiment, the width of the spacer groove 6 is 5mm, the length is 500mm, the groove depth is the same as or close to the wall thickness of the PVC cylinder, and 50mm ungrooved areas are reserved at the upper and lower ends of the vertical protective support structure 2 to ensure the overall formability and installation stability of the vertical protective support structure 2.

[0031] like Figure 2As shown, the spacer groove 6 is filled with a low-stiffness material 11, preferably a foamed filler (a foamed filler material that can be filled into the spacer groove 6 to form a low-stiffness filling effect, including foam adhesive, foam filler, etc.) or an elastic sealing material. Through the above arrangement, the vertical protective support structure 2 can reduce its additional constraint effect on the core concrete 5 while meeting the installation and fixing requirements of the confining pressure measuring unit 3 and the external constraint member 4.

[0032] like Figure 3 As shown, the confining pressure measurement unit 3 includes a miniature pressure gauge 7, a circumferential protective structure 8, and an auxiliary force transmission leveling device 9. The miniature pressure gauge 7 can be any of a resistance strain gauge pressure sensor, a bridge pressure sensor, or a micromechanical pressure sensor, and is connected to the data acquisition and analysis device 1 via wires. The data acquisition and analysis device 1 includes a signal acquisition unit, a signal transmission module, and a computer terminal, used for acquiring, recording, storing, displaying, and analyzing the confining pressure electrical signal. Generally, the miniature pressure gauge 7 has a cylindrical structure with a diameter of 10-25 mm and a height of 4-10 mm to ensure that the miniature pressure gauge 7 can be installed within the circumferential protective structure 8, while also considering installation space, force transmission stability, and confining pressure measurement accuracy. When the size of the miniature pressure gauge 7 is too large, it is not conducive to its installation and arrangement within the circumferential protective structure 8, and may adversely affect the local stress state; when the size of the miniature pressure gauge 7 is too small, it is not conducive to the stable sensing and transmission of the radial action applied by the core concrete 5. In this embodiment, the miniature pressure gauge 7 is a cylindrical metal-cased miniature pressure gauge with its pressure-bearing surface facing the core concrete 5. It has a diameter of 17 mm, a height of 7 mm, and a range of 0–25 MPa.

[0033] A circumferential protective structure 8 is disposed on the outer periphery of the miniature pressure gauge 7. In this embodiment, the circumferential protective structure 8 serves as a protective shell. Since the inner wall of the vertical protective support structure 2 is arc-shaped, while the mounting surface of the miniature pressure gauge 7 is typically flat, direct installation could easily result in localized gaps, leading to uneven stress transmission. Therefore, an arc-shaped contact surface matching the curvature of the inner wall of the vertical protective support structure 2 is provided at the bottom of the circumferential protective structure 8 to reduce the contact gap between the miniature pressure gauge 7 and the inner wall of the vertical protective support structure 2, thereby improving the uniformity of stress transmission. The body of the circumferential protective structure 8 is made of stainless steel with a thickness of 3mm, thereby improving the overall stress stability of the confining pressure measurement unit 3.

[0034] The inner dimensions of the circumferential protective structure 8 are adapted to the outer dimensions of the miniature pressure gauge 7, and an assembly gap is reserved between the inner wall of the circumferential protective structure 8 and the outer side of the miniature pressure gauge 7. In this embodiment, the assembly gap is 0.2–1.0 mm, and can be filled and limited using epoxy resin, elastic filler material, or thin gaskets. This design prevents the miniature pressure gauge 7 from being difficult to install into the circumferential protective structure 8 due to excessive tightness, and also prevents the miniature pressure gauge 7 from shaking, shifting, experiencing localized gaps, or discontinuous stress transmission during stress transmission due to an excessively large assembly gap, thereby improving the stability and accuracy of confining pressure measurement.

[0035] Furthermore, the random distribution of aggregates within the concrete can easily lead to localized simultaneous contact between the micro pressure gauge 7 and the surrounding structure, thus affecting the accurate transmission and sensing of radial forces. To mitigate this impact, an auxiliary force transmission and leveling device 9 is installed on the pressure-bearing surface of the micro pressure gauge 7. This auxiliary force transmission and leveling device 9 uses an elastic rubber pad matching the size of the micro pressure gauge 7 and is fixed to the pressure-bearing surface of the micro pressure gauge 7 by adhesive bonding. It improves the force transmission state between the core concrete 5 and the micro pressure gauge 7, allowing the radial force applied by the core concrete 5 to be transmitted more evenly to the micro pressure gauge 7. This reduces bias errors caused by localized aggregate protrusions, random particle contact, or surface unevenness, thereby improving the accuracy of confining pressure acquisition.

[0036] like Figure 4 As shown, the confining pressure measurement unit 3 is installed at a predetermined monitoring position on the vertical protective support structure 2. The predetermined monitoring position is a location where the monitored object experiences significant stress, where the cross-section changes, where the constraint effect changes significantly, or other areas requiring focused monitoring. In this embodiment, the confining pressure measurement unit 3 is installed 150mm from the top of the monitored object. Figure 4 As shown, in this embodiment, there are four confining pressure measurement units 3, each located at the same horizontal height and evenly distributed circumferentially on the same horizontal cross-section. To facilitate wire lead-out, wire lead-out holes 10 are provided at corresponding positions on the vertical protective support structure 2. That is, in this embodiment, a confining pressure measurement unit 3 and its corresponding wire lead-out hole 10 are provided every 90° along the circumference to achieve single-point and multi-point quantitative monitoring of confining pressure.

[0037] The miniature pressure gauge 7 in a single confining pressure measurement unit 3 is used to measure the confining pressure at the corresponding measuring point. When multiple confining pressure measurement units 3 are set, each miniature pressure gauge 7 can measure the confining pressure at different circumferential positions to characterize the distribution of confining pressure in the circumferential direction or obtain the entire process development curve of confining pressure at different measuring points.

[0038] During installation, first assemble the confining pressure measuring unit 3, then glue it to the inner wall of the vertical protective support structure 2 using epoxy resin adhesive, and lead the wires out through the wire lead-out hole 10. To ensure a tight fit between the confining pressure measuring unit 3 and the inner wall of the vertical protective support structure 2, transparent tape can be used for additional fixation after gluing, and pressure should be applied to the corresponding positions. Allow it to stand for 24 hours before proceeding to the next step.

[0039] In this embodiment, a fiber composite winding layer is used as the external constraint member 4. Specifically, the fiber composite fabric is impregnated with a resin system and then wound around the outside of the vertical protective support structure 2, forming the external constraint member 4 after curing. Different winding layers and winding angles can be selected according to application requirements. In addition, the external constraint member 4 can also be a metal sleeve, a fiber composite sleeve, a polymer material constraint cylinder, or other external constraint members 4 that can provide circumferential constraint to the core concrete 5. This embodiment achieves built-in direct quantitative monitoring of the confining pressure of the confined concrete structure by setting up the vertical protective support structure 2, the spacer groove 6, and the confining pressure measurement unit 3.

[0040] The working principle of this embodiment is as follows: Under stress, the core concrete 5 gradually expands or contracts laterally. Since the core concrete 5 is in direct contact with the auxiliary force transmission and leveling device 9 in the confining pressure measurement unit 3, the radial force generated by the core concrete 5 is transmitted to the micro pressure gauge 7 via the auxiliary force transmission and leveling device 9. The micro pressure gauge 7 converts the sensed radial force into an electrical signal, which is transmitted to the data acquisition and analysis device 1 via a wire. After calibration, the electrical signal is converted into the confining pressure value at each measuring point; when multiple confining pressure measurement units 3 are set, the confining pressure at each measuring point at different circumferential positions can be characterized respectively.

[0041] Compared with the traditional method of calculating confining pressure by external surface strain, this embodiment does not rely on complex theoretical conversions and can more directly reflect the development law of confining pressure at each measuring point of the confined concrete structure; when a multi-point arrangement is adopted, the distribution characteristics of confining pressure at different circumferential positions can be further analyzed.

[0042] Example 2: A method for quantitative monitoring of confining pressure in a confined concrete structure, using the built-in confining pressure measuring device described in Example 1, includes the following steps: S1, preparing a vertical protective support structure 2, and opening a spacer groove 6 in the axial direction of the vertical protective support structure 2, and then filling the spacer groove 6 with a low-stiffness material 11.

[0043] S2. An external restraint member 4 is installed on the outside of the vertical protective support structure 2. The external restraint member 4 can be installed on the outside of the vertical protective support structure 2 by means of wrapping, pasting, fitting, prefabrication, or combination installation.

[0044] S3. When the external constraint component 4 is a fiber composite material winding layer that needs to be cured, after it is cured, the confining pressure measurement unit 3 is installed at the predetermined monitoring position on the inner wall of the vertical protective support structure 2, and the wire is led out and fixed before curing. When the external constraint component 4 is a metal sleeve, polymer sleeve or other prefabricated component, the confining pressure measurement unit 3 can be arranged at the corresponding monitoring position after its installation, and the wire is led out, fixed and cured.

[0045] S4. At the bottom of the enclosed vertical protective support structure 2, core concrete 5 is poured inside the vertical protective support structure 2 and cured to form a confined concrete monitoring object, such as... Figure 5 and Figure 6 As shown; the ends of the molded monitoring object are trimmed to meet the monitoring and stress requirements.

[0046] S5. When using the monitoring object for quantitative monitoring of confining pressure, first connect the miniature pressure gauge 7 in the confining pressure measurement unit 3 to the data acquisition and analysis device 1 through a wire, and then collect the electrical signal output by the miniature pressure gauge 7 through the signal acquisition unit in the data acquisition and analysis device 1.

[0047] Before applying force, the miniature pressure gauge 7 is calibrated to establish a calibration curve or conversion relationship between the output electrical signal and the pressure value.

[0048] S6. Place the monitored object in a stress-bearing device or environment. During the stress process, the data acquisition and analysis device 1 synchronously acquires and records the confining pressure electrical signal and the corresponding axial load, axial stress, or axial strain data according to a preset time interval or preset sampling frequency, covering the entire stress process of the monitored object. The preset time interval or preset sampling frequency can be set according to the stress stage of the monitored object, the rate of change of confining pressure, and the monitoring accuracy requirements.

[0049] S7. As the monitored object is subjected to stress, the core concrete 5 gradually expands or contracts laterally. The micro pressure gauge 7 senses the radial force generated and converts it into an electrical signal, which is then synchronously acquired and recorded by the data acquisition and analysis device 1. Based on the acquired confining pressure electrical signal, the confining pressure value at each monitoring location is calculated, and a confining pressure development curve for the entire process is generated, along with the corresponding relationship between confining pressure and axial load, axial stress, or axial strain.

[0050] When multiple confining pressure measurement units 3 are set, confining pressure development curves at different circumferential positions can be generated. During the rapid change of confining pressure, the preset time interval can be shortened or the preset sampling frequency can be increased; during the slow change of confining pressure, the preset time interval can be extended or the preset sampling frequency can be decreased.

[0051] Of course, the above description is not intended to limit the present invention, and the present invention is not limited to the examples given above. Any changes, modifications, additions or substitutions made by those skilled in the art within the scope of the present invention should also fall within the protection scope of the present invention.

Claims

1. An in-situ confining pressure measuring device for use in restraining a concrete structure, characterized by, This includes data acquisition and analysis equipment, vertical protective support structure, confining pressure measurement unit, and external constraint components; The external constraint member is located on the outside of the vertical protective support structure, the interior of the vertical protective support structure is filled with core concrete, and the confining pressure measurement unit is located on the inner wall of the vertical protective support structure and connected to the data acquisition and analysis equipment. The confining pressure measurement unit includes a miniature pressure gauge, a circumferential protective structure, and an auxiliary force transmission and leveling device. The circumferential protective structure is located on the outside of the miniature pressure gauge, and the bottom of the circumferential protective structure is in contact with the inner wall of the vertical protective support structure. The auxiliary force transmission and leveling device is located on the pressure-bearing surface of the miniature pressure gauge.

2. The built-in confining pressure measuring device for a concrete structure according to Claim 1, wherein The vertical protective support structure has non-through slots along its vertical direction, and the slots are filled with low-rigidity material.

3. The built-in confining pressure measuring device for a concrete structure according to Claim 1, wherein The confining pressure measurement unit is installed at a predetermined monitoring position on the vertical protective support structure. The predetermined monitoring position is the part of the monitoring object that is subjected to greater force, the part where the cross-section changes, or the part where the constraint changes.

4. The built-in confining pressure measuring device for a concrete structure according to Claim 3, characterized by There are multiple confining pressure measurement units, each set at the same horizontal height and evenly distributed circumferentially on the same horizontal cross section.

5. The built-in confining pressure measuring device for constrained concrete structures according to claim 1, characterized in that, An assembly gap is reserved between the circumferential protective structure and the miniature pressure gauge, and epoxy resin glue, elastic filler material or gasket is used for filling and limiting treatment.

6. The built-in confining pressure measuring device for constrained concrete structures according to claim 1, characterized in that, The auxiliary force transmission and leveling device uses elastic shims, flexible shims, or compressible leveling layers that match the size of the micro pressure gauge to uniformly transmit the radial force applied by the core concrete to the micro pressure gauge.

7. The built-in confining pressure measuring device for constrained concrete structures according to claim 1, characterized in that, The external constraint component is made of fiber composite material winding layer, metal sleeve, fiber composite material sleeve or polymer material constraint cylinder.

8. The built-in confining pressure measuring device for constrained concrete structures according to claim 2, characterized in that, The low-stiffness material is a foamed filler or an elastic sealing material.

9. A method for quantitative monitoring of confining pressure in confined concrete structures, characterized in that, The built-in confining pressure measuring device according to any one of claims 1-8 includes the following steps: S1. Prepare a vertical protective support structure and open a spacer groove on the vertical protective support structure, and then fill the spacer groove with a low-stiffness material. S2. Install external restraint components on the outside of the vertical protective support structure; S3. Install a confining pressure measurement unit at a predetermined monitoring position on the inner wall of the vertical protective support structure. The miniature pressure gauge of the confining pressure measurement unit is connected to the data acquisition and analysis equipment. S4. At the bottom of the closed vertical protective support structure, core concrete is poured inside the vertical protective support structure and cured to form a confined concrete monitoring object; S5. Before applying force, calibrate the micro pressure gauge to establish the correspondence between the output electrical signal and the pressure value. S6. During the stress process of the monitored object, the confining pressure signal and the corresponding axial load, axial stress or axial strain data are collected synchronously according to the preset time interval or preset sampling frequency, and the confining pressure signal is continuously recorded. S7. Based on the confining pressure electrical signal, the confining pressure value at each monitoring location is calculated, and a confining pressure development curve for the entire process is generated, as well as the corresponding relationship between confining pressure and axial load, axial stress, or axial strain.

10. The method for quantitative monitoring of confining pressure in confined concrete structures according to claim 9, characterized in that, In step S2, the external constraint components are installed on the outside of the vertical protective support structure by means of wrapping, pasting, fitting, prefabricating wrapping or combination installation.

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