A dowel type culvert settlement monitoring point layout system

Abstract

The application discloses a type of embedded tendon formula culvert settlement monitoring point layout system, relates to the technical field of underground structure monitoring of water conservancy projects, and comprises an embedded tendon anchoring main body and a monitoring marker head assembly; the embedded tendon anchoring main body is a coaxial three-layer composite cylindrical structure, and comprises, from inside to outside, a reference core layer integrally formed of invar, a high-strength anchoring layer made of screw thread steel, and a closed-loop corrosion-resistant insulation layer; the monitoring marker head assembly is integrally formed by friction welding with the embedded tendon anchoring main body, is provided with a reference measurement surface at the top, and is provided with a distributed optical fiber sensing array on the inner wall of the anchoring section; signals are transmitted to a signal processing module in the marker head. The application constructs a precise settlement reference transmission system by means of the coaxial three-layer composite embedded tendon anchoring main body and the integrally formed monitoring marker head, realizes full-cycle control of anchoring quality in combination with the distributed optical fiber sensing array in the full anchoring section, and is fully compatible with the complex working conditions of culverts, so that the problems of monitoring distortion and anchoring failure without early warning in the traditional scheme are solved.

Description

Technical Field

[0001] This invention relates to the field of underground structure monitoring technology for water conservancy projects, specifically a system for deploying settlement monitoring points for reinforced culverts. Background Technology

[0002] As core structures for urban drainage, flood control, and water conveyance networks, the structural integrity of culverts directly impacts the operational safety of underground spaces. During long-term service, culverts are highly susceptible to uneven settlement due to multiple factors, including geological changes, variations in superstructure loads, seepage erosion, and disturbances from surrounding construction projects. This can lead to structural cracking, joint leakage, and cross-sectional deformation, among other safety hazards. Settlement deformation monitoring is a crucial aspect of safety management throughout the entire service life of culverts. Rebar-installed monitoring points have become the mainstream method for settlement monitoring due to their ease of construction and minimal disturbance to the main structure. However, with the continuous improvement in the sophistication of underground infrastructure operation and maintenance, the industry is placing higher demands on the measurement accuracy, long-term reliability, and adaptability to complex operating conditions of monitoring points.

[0003] Existing rebar-mounted culvert settlement monitoring points generally employ a separate installation structure for the rebar rod and monitoring head. This results in assembly gaps and coaxiality deviations that cannot be completely eliminated. During long-term service, the interface between the rebar rod and the concrete is prone to creep and micro-slippage, directly disrupting the settlement benchmark transmission path and ultimately leading to persistent systematic biases in the monitoring data. Current solutions can only verify the anchoring effect through post-construction destructive pull-out tests, failing to provide real-time control over the curing state of the anchoring adhesive during construction or early warning of anchoring force attenuation and interface slippage during long-term service. This easily leads to monitoring points failing without timely identification. Furthermore, these solutions lack adaptation and optimization for the special conditions of culverts operating with water and in confined working spaces, resulting in significant disturbance to the main structure during installation and high subsequent maintenance costs. Summary of the Invention

[0004] The purpose of this invention is to overcome the shortcomings of existing technologies and provide a rebar-mounted culvert settlement monitoring point deployment system. This system integrates the coaxial three-layer composite rebar anchoring body with the monitoring head assembly through friction welding, constructing an uninterrupted settlement transfer path from the Invar reference core through the entire length to the mirror reference measurement surface, eliminating assembly gaps and temperature deformation interference. Simultaneously, utilizing a distributed fiber optic grating sensor array covering the entire anchoring section and a dual-core differential temperature self-compensation algorithm, it calculates the actual settlement and anchoring force in real time and provides early warning of anchoring failure based on a graded early warning model. Equipped with a unidirectional grouting channel, streamlined protective shell, and coaxial sleeve-type drilling mechanism, the monitoring points can be minimally invasively deployed in culverts with water, resisting water flow impact and debris collision, and adapting to high humidity corrosion and confined space conditions. This solves the problems of distorted reference transfer, unknown anchoring quality, and poor adaptability to culvert operations with water in traditional solutions.

[0005] To solve the above-mentioned technical problems, the present invention provides the following technical solution: a rebar-type culvert settlement monitoring point deployment system, the system comprising a rebar anchoring body and a monitoring head assembly, wherein the rebar anchoring body is a coaxial three-layer composite cylindrical structure, and from the inside out, a reference core layer, a high-strength anchoring layer, and a corrosion-resistant insulation layer are coaxially arranged sequentially.

[0006] The reference core layer is made of Invar steel and is a single continuous, seamless, integrally formed structure that runs continuously through the entire axial length of the rebar anchoring body.

[0007] The high-strength anchoring layer is made of threaded steel, and its inner wall is interference-fitted with the outer wall of the reference core layer to form a rigid wrap, completely covering the non-exposed section of the reference core layer.

[0008] The anti-corrosion insulation layer is a multi-layer continuous closed-loop structure, covering the entire outer surface of the high-strength anchoring layer without interruption.

[0009] The monitoring head assembly is located at the exposed end of the rebar anchoring body, and the monitoring head assembly and the rebar anchoring body are formed into a metallurgical-grade integrated structure by friction welding.

[0010] The top of the monitoring head assembly is provided with a reference measurement surface, which is a rigid plane with a mirror finish. The reference measurement surface is completely perpendicular to the central axis of the reference core layer. The top of the reference core layer is directly and rigidly attached to the center of the reference measurement surface without any intermediate connecting structure.

[0011] The embedded section of the anchoring body is the anchoring section. The inner wall of the high-strength anchoring layer within the anchoring section is provided with a distributed optical fiber sensor array at equal intervals along the axial direction. The layout range of the distributed optical fiber sensor array covers the entire length of the anchoring section. The signal transmission line of the distributed optical fiber sensor array is fixedly laid along the outer wall of the reference core layer, and the end of the signal transmission line extends to the signal processing module inside the monitoring head assembly.

[0012] Furthermore, the high-strength anchoring layer is made of high-strength construction threaded steel, and the outer wall of the high-strength anchoring layer is provided with a variable cross-section barbed thread structure. The thread tooth height increases linearly from 0.5mm to 2mm along the embedding direction of the anchoring body. The anchoring body is provided with a coaxial one-way grouting channel. The grout inlet of the one-way grouting channel is located on the side wall of the monitoring head assembly. The grout outlets of the one-way grouting channel are arranged at 200mm intervals along the axial direction of the anchoring section. The number of grout outlets is 3 to 5. The arrangement of the grout outlets covers the entire length of the anchoring section. A one-way check valve is provided inside the grout inlet of the one-way grouting channel to prevent the backflow of adhesive.

[0013] Furthermore, the reference core layer adopts a dual-core coaxial differential structure, including a measuring reference core and a compensation reference core that are parallel to each other, made of the same material and of the same specifications; the top of the measuring reference core is rigidly connected to the reference measuring surface, and the bottom of the measuring reference core extends to the end of the anchoring section; the top of the compensation reference core is fixed to the internal cavity of the monitoring head assembly, and the bottom of the compensation reference core is a free-suspension structure that does not contact the anchoring adhesive or concrete; temperature sensing units and strain sensing units are paired and arranged on both the measuring reference core and the compensation reference core at a spacing of 80mm to 120mm.

[0014] Furthermore, the distributed optical fiber sensing array is a fiber Bragg grating sensing array, with 4 to 8 sensing units in the array, and the spacing between adjacent sensing units is 80 mm to 120 mm. Each sensing unit is equipped with one fiber Bragg grating strain gauge, and the strain acquisition resolution is not less than 1 με.

[0015] Furthermore, the anti-corrosion insulation layer is a three-layer gradient closed-loop structure, consisting of a hot-dip galvanized anti-corrosion layer, an epoxy zinc-rich sealing layer, and a nano-polyurea insulation layer from the inside out. The thickness of the hot-dip galvanized anti-corrosion layer is 80μm to 120μm, the thickness of the epoxy zinc-rich sealing layer is 50μm to 80μm, and the thickness of the nano-polyurea insulation layer is 100μm to 150μm. The three-layer structure continuously and completely covers the entire outer surface of the high-strength anchoring layer.

[0016] Furthermore, the flatness of the reference measurement surface is no greater than 0.02 mm; a standardized multi-mode adapter interface is provided on the outer side of the reference measurement surface. The adapter interface adopts a unified coaxial positioning stop and bolt locking structure, which can be matched and docked with leveling measuring pads, hydrostatic leveling sensors, fiber optic grating settlement sensors, and MEMS tilt settlement sensors.

[0017] Furthermore, it also includes a protective shell fitted around the outside of the monitoring head assembly. The protective shell is made of corrosion-resistant metal and has a streamlined biomimetic structure with an arc-shaped flow guide groove on the flow-facing surface. The protective shell has a two-stage elastic buffer mechanism inside, which includes an outer impact-resistant rubber buffer pad and an inner stainless steel cylindrical helical spring buffer assembly. The monitoring head assembly is suspended and installed at the center of the two-stage elastic buffer mechanism. A self-compensating fluororubber sealing ring is provided at the connection between the protective shell and the anchoring body. The sealing ring, the anchoring body, and the protective shell are interference-fitted to form a fully enclosed waterproof cavity.

[0018] Furthermore, the signal processing module incorporates an edge computing unit and a low-frequency wireless transmission unit. The signal transmission end of the low-frequency wireless transmission unit is electrically connected to the high-strength anchoring layer, using the high-strength anchoring layer of the rebar anchoring body as a signal radiating antenna.

[0019] Furthermore, the edge computing unit incorporates a graded early warning model for anchorage failure. This model has two preset anchorage force thresholds. The model calculates the real-time total anchorage force based on the axial strain data of the entire anchorage section collected by the distributed fiber optic sensor array. When the real-time total anchorage force is lower than 70% to 85% of the rated design anchorage force of the rebar anchorage body, a first-level early warning is triggered. When it is lower than 50% to 65% of the rated design anchorage force, a second-level early warning is triggered.

[0020] Furthermore, it also includes a coaxial sleeve-type drilling mechanism that matches the rebar anchoring body. The inner diameter of the sleeve of the coaxial sleeve-type drilling mechanism is clearance-fitted with the outer diameter of the rebar anchoring body. A water-swellable rubber sealing ring is provided at the front end of the sleeve, and axially continuous depth scale markings are provided on the side wall of the sleeve. The clearance between the inner diameter of the sleeve and the outer diameter of the rebar anchoring body on one side is 0.2mm to 0.5mm.

[0021] Compared with existing technologies, this reinforced concrete culvert settlement monitoring point deployment system has the following advantages:

[0022] I. This invention constructs a seamless settlement benchmark transmission system by using a coaxial three-layer composite rebar anchoring body, in conjunction with a metallurgically integrated monitoring head assembly. The benchmark core, made of Invar steel, runs the entire axial length of the rebar anchoring body, avoiding the benchmark deformation interference caused by the thermal expansion and contraction of ordinary steel. The integrated structure completely eliminates assembly gaps and coaxiality deviations caused by split installations. The top of the benchmark core is directly and rigidly attached to the benchmark measurement surface without intermediate connecting structures, ensuring a 1:1 accurate transmission of settlement deformation of the culvert structure. This solves the problem of benchmark transmission distortion in traditional solutions and effectively reduces the deviation of the monitoring system.

[0023] II. This invention achieves closed-loop control of rebar anchoring quality throughout its entire service life by embedding a distributed optical fiber sensor array covering the entire length of the anchoring section, in conjunction with the edge computing unit built into the signal processing module. The sensor array can collect axial strain data at different locations in the anchoring section in real time. During the construction phase, the curing state of the anchoring adhesive and the anchoring effect can be determined by the strain change pattern, eliminating the need for destructive pull-out tests. During long-term service, it can capture the attenuation of anchoring force, interface micro-slippage, and the development of concrete micro-cracks in real time, and issue early warning signals in advance in conjunction with a graded early warning model, avoiding the problem of monitoring data distortion caused by monitoring point failure.

[0024] Third, this invention, through its matching unidirectional grouting channel, streamlined protective shell, and coaxial sleeve-type drilling mechanism, is fully adaptable to the complex service and operating environment of culverts. The unidirectional grouting channel can simultaneously complete anchoring, water-stopping, and sealing operations after rebar installation. Combined with the coaxial sleeve-type drilling mechanism, it allows for minimally invasive installation in culverts operating with water, without requiring water outages or shutdowns, resulting in minimal disturbance to the main structure. The streamlined protective shell achieves self-cleaning and anti-siltation with the help of water flow, the dual-stage buffer structure resists impacts from debris, the fully enclosed sealing structure is suitable for high-humidity immersion conditions, and the multi-mode adapter interface is compatible with various mainstream monitoring equipment, eliminating the need for repeated deployment of monitoring points.

[0025] Other advantages, objectives and features of the invention will be set forth in part in the description which follows, and in part will be apparent to those skilled in the art from the following examination or study, or may be learned from the practice of the invention. Attached Figure Description

[0026] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the accompanying drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are merely some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without any creative effort.

[0027] Figure 1 This is a schematic diagram showing the overall structure and core features of the rebar-reinforced culvert settlement monitoring point deployment system of the present invention.

[0028] Figure 2 This is a flowchart of the on-site minimally invasive deployment operation of the deployment system of the present invention;

[0029] Figure 3 This is a flowchart illustrating the monitoring, correction, and graded early warning process of the deployment system during long-term service of this invention. Detailed Implementation

[0030] To further illustrate the technical means and effects of the present invention in achieving its intended purpose, the following detailed description of the specific implementation methods, structures, features, and effects of the present invention, in conjunction with the accompanying drawings and preferred embodiments, is provided below.

[0031] This embodiment discloses a specific implementation of a rebar-type culvert settlement monitoring point deployment system. Addressing the problems of distorted reference transmission, uncontrollable anchoring quality, and poor adaptability to complex working conditions in existing culvert settlement monitoring points, it adopts a core structure of a coaxial three-layer composite rebar anchoring body combined with an integrated molded monitoring head. Combined with a distributed fiber optic sensing monitoring system across the entire anchoring section, it achieves accurate monitoring of culvert settlement deformation and full lifecycle management of anchoring quality, making it adaptable to the complex service and operating environments of culverts.

[0032] The rebar-anchored culvert settlement monitoring point deployment system of this embodiment consists of six parts: the rebar anchoring body, the monitoring target assembly, the distributed fiber optic sensor array, the signal processing module, the supporting protection mechanism, and the supporting operating mechanism. Its overall structure and core feature relationships are as follows: Figure 1 As shown in the diagram. The rebar anchoring main body is the main load-bearing and benchmark transmission structure of the system, the monitoring head assembly is the benchmark carrier for measuring settlement deformation, the distributed fiber optic sensor array is the core for monitoring the anchoring status, the signal processing module is the core unit for data acquisition and analysis, the supporting protective mechanism provides protection for the system's long-term service, and the supporting operating mechanism provides construction conditions for the system's on-site deployment.

[0033] The main body of the rebar anchoring adopts a coaxial three-layer composite cylindrical structure. From the inside to the outside, a reference core layer, a high-strength anchoring layer, and an anti-corrosion insulation layer are set coaxially. The three-layer structure is coaxially integrally formed without relative displacement, ensuring the stability of the reference transmission.

[0034] The reference core layer is made of Invar steel, a single continuous, seamless, integrally formed structure that runs continuously along the entire axial length of the rebar anchoring body. Invar steel has an extremely low coefficient of linear expansion, minimizing its axial deformation under varying ambient temperatures, thus preventing reference offset caused by temperature changes and eliminating interference from temperature deformation on settlement monitoring results at the material level. The reference core layer employs a dual-core coaxial differential structure, comprising a parallel, identical material and specification measurement reference core and a compensation reference core. The top of the measurement reference core is rigidly connected to the reference measurement surface of the monitoring head assembly, while the bottom extends to the end of the anchoring section of the rebar anchoring body, participating in the transmission of settlement deformation throughout the entire process. The top of the compensation reference core is fixed to the internal cavity of the monitoring head assembly, while the bottom is a free-suspension structure, not in contact with the anchoring adhesive or concrete, and unaffected by anchoring stress or structural deformation. It is used solely to collect pure material deformation data caused by ambient temperature changes, providing reference data for temperature self-compensation calculations. Temperature sensing units and strain sensing units are paired on both the measurement reference core and the compensation reference core. The two sets of sensing units are arranged at equal intervals of 80mm to 120mm along the axial direction of the reference core, which can simultaneously collect real-time temperature and axial strain data of the two reference cores, providing original data support for subsequent settlement correction.

[0035] The high-strength anchoring layer uses high-strength structural threaded steel. Its inner wall and the outer wall of the reference core layer are interference-fitted to form a rigid enclosure, completely covering the non-exposed section of the reference core layer, providing overall structural strength and anchoring force for the rebar anchoring body. The outer wall of the high-strength anchoring layer features a variable cross-section barbed thread structure. The thread tooth height linearly increases from 0.5mm to 2mm along the embedding direction of the rebar anchoring body. The thread tooth height is smaller at the bottom of the hole to accommodate the narrow space at the bottom of the borehole, while the thread tooth height is larger at the opening to match the stress distribution of the anchoring section. After the anchoring adhesive cures, it forms a multi-level mechanical locking structure with the adhesive, and together with the chemical bonding force of the adhesive, forms a composite anchoring system. This improves the bonding strength between the rebar anchoring body and the concrete structure, preventing interface slippage during long-term service. The high-strength anchoring layer has a coaxial one-way grouting channel inside. The grout inlet of the one-way grouting channel is located on the side wall of the monitoring head assembly. The grout outlets are arranged at 200mm intervals along the axial direction of the anchoring section, with 3 to 5 outlets in total. The arrangement of the outlets covers the entire length of the anchoring section, which can ensure that the anchoring adhesive evenly fills the entire borehole space during grouting. A one-way check valve is installed inside the grout inlet of the one-way grouting channel to prevent the adhesive from flowing back after grouting and to ensure the compactness of the grout filling.

[0036] The anti-corrosion insulation layer has a multi-layer continuous closed-loop structure, covering the entire outer surface of the high-strength anchoring layer without interruption. The anti-corrosion insulation layer adopts a three-layer gradient closed-loop structure, consisting of a hot-dip galvanized anti-corrosion layer, an epoxy zinc-rich sealing layer, and a nano-polyurea insulation layer from the inside out. The thickness of the hot-dip galvanized anti-corrosion layer is 80μm–120μm, the epoxy zinc-rich sealing layer is 50μm–80μm, and the nano-polyurea insulation layer is 100μm–150μm. This three-layer structure continuously and completely covers the entire outer surface of the high-strength anchoring layer, isolating it from corrosive media and stray currents within the culvert, thus extending the service life of the rebar anchoring body.

[0037] The monitoring head assembly is located at the exposed end of the rebar anchoring body, forming a metallurgically integrated structure with the rebar anchoring body through friction welding. The welded joint surface has no assembly gaps or relative sliding displacement, completely eliminating assembly errors and reference transmission breakpoints inherent in split installation structures. A reference measuring surface is located on the top of the monitoring head assembly. This surface is a mirror-finished rigid plane with a flatness of no more than 0.02mm, ensuring a tight fit with the monitoring equipment and eliminating measurement errors caused by contact gaps. The reference measuring surface is completely perpendicular to the central axis of the reference core layer, and the top of the reference core layer is directly and rigidly fitted to the center of the reference measuring surface without any intermediate transfer structures. This ensures that the settlement deformation of the culvert structure can be proportionally and without deviation transmitted to the reference measuring surface through the rebar anchoring body, eliminating transmission errors caused by intermediate transfer structures. A standardized multi-mode adapter interface is set on the outer side of the reference measurement surface. The adapter interface adopts a unified coaxial positioning stop and bolt locking structure, which can be matched with various mainstream settlement monitoring equipment such as leveling rod pads, hydrostatic level sensors, fiber optic settlement sensors, and MEMS tilt settlement sensors. There is no need to replace the main anchoring body; only the adapter component needs to be replaced to achieve rapid switching between different monitoring schemes. The internal cavity of the monitoring head assembly houses a signal processing module. The signal processing module is electrically connected to the signal transmission line of the distributed fiber optic sensor array, the temperature sensing unit and strain sensing unit of the reference core layer, and can complete the acquisition, analysis, storage and transmission of raw data.

[0038] A distributed fiber optic sensor array is deployed along the inner wall of the high-strength anchorage layer within the anchorage section of the rebar anchorage body. It is evenly spaced along the axial direction of the anchorage section, covering its entire length. The distributed fiber optic sensor array is a fiber Bragg grating sensor array, containing 4–8 axially arranged sensing units. The spacing between adjacent sensing units is 80mm–120mm. Each sensing unit corresponds to a fiber Bragg grating strain gauge, which can independently acquire axial strain data of the rebar at the corresponding location in the anchorage section. The strain acquisition resolution is no less than 1με, accurately capturing micro-strain changes at the anchorage interface. The signal transmission line of the distributed fiber optic sensor array is fixedly arranged axially along the outer wall of the reference core layer. The end of the signal transmission line extends to the signal processing module inside the monitoring head assembly, transmitting the acquired strain data to the signal processing module in real time. The sensor array adopts a distributed deployment method covering the entire anchorage section, which can completely capture the distribution of bonding stress at different depths of the anchorage section, avoiding the problem that single-point sensors cannot identify local anchorage failures, and providing complete raw data support for anchorage force calculation and failure early warning.

[0039] The signal processing module integrates an edge computing unit and a low-frequency wireless transmission unit. The edge computing unit incorporates a dual-core differential temperature self-compensation calculation formula, a real-time total anchoring force calculation formula for the anchoring section, and an anchoring failure classification and early warning model, enabling real-time processing and analysis of raw data. The signal transmission end of the low-frequency wireless transmission unit is electrically connected to the high-strength anchoring layer. Using the high-strength anchoring layer of the rebar anchoring body as a signal radiating antenna, it can penetrate reinforced concrete structures to achieve wireless transmission of monitoring data without the need for additional transmission cables.

[0040] The dual-core differential temperature self-compensation calculation formula is used to eliminate the interference of axial deformation of the rebar caused by temperature changes, and to calculate the true vertical settlement of the culvert structure. The core logic of the formula is to subtract the rebar deformation caused by temperature changes from the original measured displacement values ​​collected by the monitoring equipment, and then add the pure temperature deformation correction value collected by the compensation reference core, finally obtaining the true settlement after eliminating temperature interference. The expression of the calculation formula is:

[0041] ;

[0042] in is the actual vertical settlement of the culvert structure, and is the final output of the formula; The original measured displacement value of the reference measurement surface collected by the monitoring equipment includes the superimposed value of structural settlement deformation and temperature deformation; is the coefficient of linear expansion of the Invar reference core, and is the inherent physical parameter of the Invar material; L is the effective reference transfer length of the Invar reference core, that is, the total length of the reference core from the end of the anchoring section to the reference measurement surface; The ambient temperature change of the reference core during the monitoring period is collected in real time by the temperature sensing unit. To compensate for the real-time axial strain value of the reference core, the strain sensing unit on the reference core is used to collect the data in real time, including only the pure material deformation strain caused by temperature changes. This calculation formula completely eliminates the interference of ambient temperature changes on the settlement monitoring results, ensuring the accuracy of the monitoring results under extreme temperature difference environments.

[0043] The formula for calculating the real-time total anchorage force of the anchorage segment is used to inversely calculate the real-time total anchorage force of the rebar anchorage segment based on strain data collected by a distributed sensor array, thus achieving real-time control of anchorage quality. The core logic of the calculation formula is to calculate the real-time total anchorage force of the anchorage segment by combining the average strain value across the entire anchorage segment with the elastic modulus and effective cross-sectional area of ​​the high-strength anchorage layer. The expression of the calculation formula is:

[0044] ;

[0045] in is the real-time total anchorage force of the rebar anchorage segment, and is the final output result of the formula; The elastic modulus of the high-strength anchoring layer is denoted as , and the inherent physical parameters of the high-strength structural threaded steel are denoted as . is the effective cross-sectional area of ​​the high-strength anchoring layer, and is the nominal cross-sectional area of ​​the high-strength anchoring layer; n is the total number of sensing units in the distributed fiber optic sensing array within the anchoring section; i is the sequence number of the sensing unit, which takes the value from 1 to n, a positive integer, corresponding to the sensing unit at different depths within the anchoring section. The axial strain value of the rebar, acquired in real time by the i-th sensing unit, reflects the bond stress distribution at the interface between the rebar and concrete at the corresponding location. Using this calculation formula, the total anchorage force of the rebar anchorage segment can be obtained in real time without destructive pull-out tests, enabling real-time monitoring of the anchorage quality throughout its entire lifecycle.

[0046] The anchorage failure classification and early warning model has two preset anchorage force thresholds. The model compares the calculated real-time total anchorage force with the preset thresholds. When the real-time total anchorage force is lower than 70% to 85% of the rated design anchorage force of the rebar anchorage, a first-level early warning is triggered. When it is lower than 50% to 65% of the rated design anchorage force, a second-level early warning is triggered. This achieves early warning of anchorage failure. The threshold settings match the safety factor requirements of rebar anchorage in the concrete structure design code and are suitable for the safety management needs of the engineering site.

[0047] The supporting protective mechanism is a protective shell fitted onto the outside of the monitoring head assembly. The shell is made of corrosion-resistant metal and features a streamlined, biomimetic structure. An arc-shaped flow guide channel on the flow-facing surface automatically flushes away silt and debris from the shell surface using the impact force of the water flow within the culvert, preventing the monitoring points from being covered by silt. The protective shell contains a two-stage elastic buffer mechanism, consisting of an outer impact-resistant rubber buffer pad and an inner stainless steel cylindrical helical spring buffer assembly. The monitoring head assembly is suspended and installed at the center of this mechanism, resisting the direct impact of large debris within the culvert and preventing damage to the reference measurement surface. A self-compensating fluororubber sealing ring is installed at the connection between the protective shell and the anchoring body. This sealing ring, along with the anchoring body and the protective shell, forms a fully enclosed waterproof cavity, preventing moisture and corrosive media from entering the protective shell and ensuring the long-term stable operation of the monitoring head assembly.

[0048] The supporting operating mechanism is a coaxial sleeve-type drilling mechanism that matches the main body of the rebar anchoring. The inner diameter of the sleeve of the coaxial sleeve-type drilling mechanism is clearance-fitted with the outer diameter of the main body of the rebar anchoring. The clearance on one side of the inner diameter of the sleeve and the outer diameter of the main body of the rebar anchoring is 0.2mm to 0.5mm. This ensures that the main body of the rebar anchoring is smoothly inserted into the sleeve and controls the amount of grout overflow during grouting. The front end of the sleeve is equipped with a water-swellable rubber sealing ring, and the side wall of the sleeve is equipped with axially continuous depth markings to accurately control the drilling depth. During the drilling operation, the sealing ring at the front end of the sleeve automatically expands when it comes into contact with water, blocking the channel between the borehole and the water inside the culvert, preventing water and silt from flowing into the working face during the drilling process, and enabling operation in water. After drilling is completed, there is no need to remove the sleeve. The main body of the rebar anchoring is directly inserted into the sleeve, and the grouting operation is completed through the one-way grouting channel. This enables minimally invasive installation of culverts that are in service in water, without the need to stop water supply or operation, and with minimal disturbance to the main structure of the culvert.

[0049] The on-site minimally invasive deployment process of this system is as follows: Figure 2 As shown, the specific steps are as follows: First, the pre-set monitoring points in the culvert are laid out and positioned to determine the drilling location and axis, ensuring that the drilling axis is parallel to the direction of gravity and the verticality deviation is controlled within 0.5°. Then, a coaxial sleeve drilling mechanism is used to complete the drilling operation, with the drilling depth consistent with the designed length of the anchoring section. After drilling, high-pressure air is used in conjunction with a cleaning brush to clean the dust, debris, and accumulated water inside the hole, ensuring the hole wall is clean and free of floating dust. The anchoring body is then inserted into the drilled hole, and the verticality of the anchoring body is readjusted to ensure... The axis of the reference core layer is parallel to the direction of gravity. Anchoring adhesive and water-stopping sealing material are injected through a one-way grouting channel. The grouting pressure is controlled between 0.2MPa and 0.4MPa. The three processes of anchoring, water-stopping and sealing are completed in one grouting. The grouting pressure ensures that the adhesive completely fills the gap between the drill holes, without voids or air bubbles. During the curing process of the anchoring adhesive, the curing stress data is collected in real time through a distributed fiber optic sensor array to judge the curing status of the anchoring adhesive and the anchoring quality. After the anchoring quality meets the standard, the protective shell is installed to complete the deployment of monitoring points.

[0050] The monitoring, correction, and graded early warning process during the long-term service of the system is as follows: Figure 3As shown, specifically: when the culvert structure experiences settlement deformation, the deformation is synchronously transmitted to the reference measurement surface of the monitoring head component through the anchoring body of the rebar rigidly anchored to the structure. The vertical displacement data of the reference measurement surface is collected by the external monitoring equipment to obtain the original measured displacement value. At the same time, the temperature sensing unit and strain sensing unit of the reference core layer synchronously collect temperature and strain data, and the distributed optical fiber sensing array synchronously collects the axial strain data of the anchoring section. All raw data are transmitted to the signal processing module in real time. The signal processing module performs temperature correction on the original measured displacement value through the dual-core differential temperature self-compensation calculation formula to obtain the true vertical settlement of the culvert structure. The real-time total anchoring force of the anchoring section is calculated through the real-time total anchoring force calculation formula, and the early warning judgment is completed through the anchoring failure classification early warning model. Finally, the processed monitoring data and early warning signal are transmitted to the ground monitoring platform through the low-frequency wireless transmission unit to complete a complete monitoring cycle.

[0051] This embodiment solves the problems of distorted reference transmission and lack of early warning for anchorage failure in traditional culvert settlement monitoring points by combining an integrated coaxial reference transmission structure with a full life-cycle anchorage monitoring system. It can be adapted to various complex working conditions such as water-bearing service, high humidity and high corrosion, and confined spaces. It can be applied to settlement and deformation monitoring scenarios of various underground enclosed structures such as water conservancy culverts, urban drainage culverts, underground integrated pipe corridors, and underground box culverts.

[0052] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention in any way. Although the present invention has been disclosed above with reference to preferred embodiments, it is not intended to limit the present invention. Any person skilled in the art can make some modifications or alterations to the above-disclosed technical content to create equivalent embodiments without departing from the scope of the present invention. Any simple modifications, equivalent changes and alterations made to the above embodiments based on the technical essence of the present invention without departing from the scope of the present invention shall still fall within the scope of the present invention.

Claims

1. A system for deploying settlement monitoring points in a reinforced culvert, characterized in that, The system includes a rebar anchoring body and a monitoring head assembly. The rebar anchoring body is a coaxial three-layer composite cylindrical structure, with a reference core layer, a high-strength anchoring layer, and an anti-corrosion insulation layer coaxially arranged from the inside to the outside. The reference core layer is made of Invar steel and is a single continuous, seamless, integrally formed structure that runs continuously through the entire axial length of the rebar anchoring body. The high-strength anchoring layer is made of threaded steel, and its inner wall is interference-fitted with the outer wall of the reference core layer to form a rigid wrap, completely covering the non-exposed section of the reference core layer. The anti-corrosion insulation layer is a multi-layer continuous closed-loop structure, covering the entire outer surface of the high-strength anchoring layer without interruption. The monitoring head assembly is located at the exposed end of the rebar anchoring body, and the monitoring head assembly and the rebar anchoring body are formed into a metallurgical-grade integrated structure by friction welding. The top of the monitoring head assembly is provided with a reference measurement surface, which is a rigid plane with a mirror finish. The reference measurement surface is completely perpendicular to the central axis of the reference core layer. The top of the reference core layer is directly and rigidly attached to the center of the reference measurement surface without any intermediate connecting structure. The embedded section of the anchoring body is the anchoring section. The inner wall of the high-strength anchoring layer within the anchoring section is provided with a distributed optical fiber sensor array at equal intervals along the axial direction. The layout range of the distributed optical fiber sensor array covers the entire length of the anchoring section. The signal transmission line of the distributed optical fiber sensor array is fixedly laid along the outer wall of the reference core layer, and the end of the signal transmission line extends to the signal processing module inside the monitoring head assembly.

2. The submerged culvert settlement monitoring point deployment system according to claim 1, characterized in that, The high-strength anchoring layer is made of high-strength construction threaded steel. The outer wall of the high-strength anchoring layer is provided with a variable cross-section barbed thread structure. The thread tooth height increases linearly from 0.5mm to 2mm along the embedding direction of the anchoring body. The anchoring body is provided with a coaxial one-way grouting channel. The grout inlet of the one-way grouting channel is located on the side wall of the monitoring head assembly. The grout outlets of the one-way grouting channel are arranged at 200mm intervals along the axial direction of the anchoring section. The number of grout outlets is 3 to 5. The arrangement of the grout outlets covers the entire length of the anchoring section. A one-way check valve is provided inside the grout inlet of the one-way grouting channel to prevent the backflow of adhesive.

3. The submerged culvert settlement monitoring point deployment system according to claim 1, characterized in that, The reference core layer adopts a dual-core coaxial differential structure, including a measuring reference core and a compensation reference core that are parallel to each other, made of the same material and of the same specifications. The top of the measuring reference core is rigidly connected to the reference measuring surface, and the bottom of the measuring reference core extends to the end of the anchoring section. The top of the compensation reference core is fixed to the internal cavity of the monitoring head assembly, and the bottom of the compensation reference core is a free-suspension structure that does not contact the anchoring adhesive or concrete. Temperature sensing units and strain sensing units are paired and arranged on both the measuring reference core and the compensation reference core at a spacing of 80mm to 120mm.

4. The submerged culvert settlement monitoring point deployment system according to claim 1, characterized in that, The distributed optical fiber sensing array is a fiber Bragg grating sensing array. The number of sensing units in the sensing array is 4 to 8, and the spacing between adjacent sensing units is 80 mm to 120 mm. Each sensing unit is equipped with one fiber Bragg grating strain gauge, and the strain acquisition resolution is not less than 1 με.

5. The submerged culvert settlement monitoring point deployment system according to claim 1, characterized in that, The anti-corrosion insulation layer has a three-layer gradient closed-loop structure, consisting of a hot-dip galvanized anti-corrosion layer, an epoxy zinc-rich sealing layer, and a nano-polyurea insulation layer from the inside out. The thickness of the hot-dip galvanized anti-corrosion layer is 80μm to 120μm, the thickness of the epoxy zinc-rich sealing layer is 50μm to 80μm, and the thickness of the nano-polyurea insulation layer is 100μm to 150μm. The three-layer structure continuously and completely covers the entire outer surface of the high-strength anchoring layer.

6. The submerged culvert settlement monitoring point deployment system according to claim 1, characterized in that, The flatness of the reference measurement surface is no greater than 0.02 mm; a standardized multi-mode adapter interface is set on the outer side of the reference measurement surface. The adapter interface adopts a unified coaxial positioning stop and bolt locking structure, which can be matched and docked with leveling measuring pads, static leveling sensors, fiber optic grating settlement sensors, and MEMS tilt settlement sensors.

7. The submerged culvert settlement monitoring point deployment system according to claim 1, characterized in that, It also includes a protective shell fitted around the outside of the monitoring head assembly. The protective shell is made of corrosion-resistant metal and has a streamlined biomimetic structure with an arc-shaped flow guide groove on the flow-facing surface. The protective shell is equipped with a two-stage elastic buffer mechanism, which includes an outer impact-resistant rubber buffer pad and an inner stainless steel cylindrical helical spring buffer assembly. The monitoring head assembly is suspended and installed at the center of the two-stage elastic buffer mechanism. A self-compensating fluororubber sealing ring is provided at the connection between the protective shell and the anchoring body. The sealing ring, the anchoring body, and the protective shell are interference-fitted to form a fully enclosed waterproof cavity.

8. The submerged culvert settlement monitoring point deployment system according to claim 1, characterized in that, The signal processing module has a built-in edge computing unit and a low-frequency wireless transmission unit. The signal transmission end of the low-frequency wireless transmission unit is electrically connected to the high-strength anchoring layer, and the high-strength anchoring layer of the rebar anchoring body serves as the signal radiating antenna.

9. The submerged culvert settlement monitoring point deployment system according to claim 8, characterized in that, The edge computing unit has a built-in anchorage failure graded early warning model. The anchorage failure graded early warning model has two preset anchorage force thresholds. The model calculates the real-time total anchorage force based on the axial strain data of the entire anchorage section collected by the distributed optical fiber sensor array. When the real-time total anchorage force is lower than 70% to 85% of the rated design anchorage force of the anchorage body, a first-level early warning is triggered. When it is lower than 50% to 65% of the rated design anchorage force, a second-level early warning is triggered.

10. The submerged culvert settlement monitoring point deployment system according to claim 1, characterized in that, It also includes a coaxial sleeve drilling mechanism that matches the main body of the rebar anchoring. The inner diameter of the sleeve of the coaxial sleeve drilling mechanism is clearance-fitted with the outer diameter of the main body of the rebar anchoring. A water-swellable rubber sealing ring is provided at the front end of the sleeve, and axially continuous depth scale markings are provided on the side wall of the sleeve. The clearance between the inner diameter of the sleeve and the outer diameter of the main body of the rebar anchoring is 0.2mm to 0.5mm on one side.

Images