Construction method for controlling differential settlement of new and old bridge widening connection

Abstract

This invention provides a construction method for controlling differential settlement at the connection between old and new bridges during widening. This invention relates to the field of building construction technology and includes the following specific operations: On-site investigation and design optimization: Verifying the geological conditions of the connection section between the old and new bridges, the structural condition of the old bridge, and the current settlement status; measuring the elevation of the old bridge using a level; and determining the foundation reinforcement range, grouting parameters, and compensation device layout scheme based on the geological survey report; When the differential settlement reaches a preset first threshold, the adjustable bearing can be fine-tuned by starting the screw jack via the PLC controller; when the differential settlement reaches a preset second threshold, grouting of the reinforcement layer is initiated, achieving dual compensation in conjunction with the adjustable bearing adjustment; when the preset threshold for differential settlement is less than the first threshold, the bidirectional self-locking nut of the adjustable bearing is locked, stopping active compensation. Through a high-precision active compensation system, the problem of cracks and damage caused by uneven settlement at the connection between the old and new bridges is fundamentally avoided.

Description

Technical Field

[0001] This invention relates to the field of building construction technology, specifically a construction method for controlling differential settlement during the connection between old and new bridge widening. Background Technology

[0002] Alluvial plains are vast, flat areas formed by the continuous deposition of silt carried by rivers over countless years as they reach the gentler middle and lower reaches of the river. As the water flow slows, the silt gradually settles and accumulates, eventually creating fertile, deep-soiled fields with dense river networks and low-lying terrain over millions of years. These areas are not only the cradle of human civilization (such as the Yellow River and Yangtze River basins), but also, due to their superior farming conditions and potential flood risks, have become densely populated and agriculturally developed core regions. Alluvial plains are widely characterized by soft soil layers such as silt, silty clay, and fine sand. These types of foundations exhibit engineering characteristics such as low bearing capacity, high compressibility, and long settlement periods.

[0003] In bridge widening and expansion projects, the old bridge has completed most of its settlement and stabilized after long-term operation, while the new bridge will experience new settlement due to the compression of the soft soil foundation during the construction and operation phases, resulting in a significant settlement difference between the old and new bridges. If the settlement difference is not effectively controlled, it will cause cracks, leakage, or even structural damage in the connection section, seriously affecting the overall load-bearing performance and operational safety of the bridge. Summary of the Invention

[0004] The purpose of this invention is to provide a construction method for controlling differential settlement between new and old bridges during the widening and connection phases. This method aims to solve the problem that in the existing technology, new bridges will experience new settlement due to the compression of soft soil foundations during the construction and operation phases, resulting in a significant settlement difference between the new and old bridges. If the settlement difference is not effectively controlled, it will cause cracks, leakage, or even structural damage in the connection section.

[0005] To achieve the above objectives, the present invention adopts the following technical solution: the construction method for controlling differential settlement between the old and new sections of a bridge widening project includes the following steps: S1, On-site investigation and design optimization: Review the geological conditions of the connection section between the old and new bridges, the structural status of the old bridge and the current settlement status, use a level to measure the elevation of the old bridge body, and determine the foundation reinforcement range, grouting parameters and compensation device layout scheme in conjunction with the geological investigation report. S2, Foundation Co-treatment: Before the construction of the new bridge foundation, the integrity of the old bridge abutment and beam structure is tested, and any cracks or damage are repaired. The settlement stability of the old bridge foundation is assessed. If the settlement is not yet stable, the old bridge needs to be preloaded to improve the compactness of the foundation soil. S3, Installation of compensation device: Concrete base is poured on the old bridge abutment and the foundation of the new bridge, adjustable bearing is installed on the concrete base, and the superstructure of the new bridge is installed on the upper end of the adjustable bearing. S4, New bridge construction: Wet joints are reserved at the junction of the new and old bridges to allow for adjustment space for settlement compensation. Wet joints are poured with compensating shrinkage steel fiber concrete, and reinforcement is added to the splice joints and connection parts. S5, Settlement Co-control System Deployment: During the construction and operation phases, a settlement monitoring sensor network is deployed on the top of the old bridge abutment, the top surface of the new bridge foundation, the bottom of the beam, and deep in the foundation. The output end of the settlement monitoring sensor network, the adjustment drive device of the adjustable support, and the controller of the grouting device used for foundation reinforcement grouting are all connected to the PLC control module. S6, Real-time monitoring and dynamic compensation: The settlement data of the new and old bridges are acquired in real time through the settlement monitoring sensor network. The PLC control module calculates the real-time differential settlement value. When the real-time differential settlement value reaches the preset first threshold, the PLC control module generates the first control command to drive the adjustable bearing to perform vertical displacement compensation. When the real-time differential settlement value reaches the preset second threshold, the PLC control module generates the second control command to start the grouting device to perform pressure grouting compensation on the foundation. When the real-time differential settlement value is less than the preset first threshold and has been stable for 7 consecutive days, the bidirectional self-locking nut of the adjustable bearing is locked to stop active compensation. S7, Connection Section: After the settlement stabilizes, the wet joint is subjected to secondary grouting treatment to ensure a tight connection. The flatness and structural cracks of the connection section between the new and old bridges are tested to ensure that the design requirements are met. The adjustable bearing is subjected to hot-dip galvanizing for corrosion protection. The bearing capacity is retested 7 days after the grouting reinforcement layer is cured. S8, Acceptance and Operation and Maintenance Monitoring: Submit construction records, monitoring data reports, and test reports, conduct special acceptance, monitor settlement data once a week during the first 3 months of bridge operation, and monitor once a quarter thereafter, continuously track settlement stability, and conduct corrosion inspection and functional verification of the compensation device once a year.

[0006] Preferably, in step S2, the specific steps of the foundation grouting reinforcement include: arranging grouting holes in a quincunx pattern in the foundation and abutment backfill area of ​​the new and old bridge connection section, with a hole spacing of 1.5-2m, a hole diameter of φ100-150mm, and a hole depth penetrating from the soft soil layer to the hard plastic silty clay layer; using a double-layer sleeve structure to prevent hole wall collapse; installing a grout diffuser at the bottom to expand the grout diffusion range; and grouting pressure of 0.5~0.8Mpa.

[0007] Preferably, in step S3, the concrete base has dimensions of 500×500×100mm, with pre-drilled holes for fixing bolts, and the top surface levelness deviation of the base is ≤0.2mm / m.

[0008] Preferably, in step S3, the adjustable support includes a support top plate, a hydraulic coarse adjustment unit, a spiral fine adjustment unit, and a support bottom plate arranged from top to bottom; Adjustable supports are evenly distributed transversely along the bottom of the beam of the new and old bridge connection section, with a spacing of 2-3m. The bottom plate of the support is fixed on the concrete base. After adjusting the levelness of the adjustable support, the top plate of the support is installed and fits against the bottom of the new bridge body.

[0009] Preferably, in step S5, the PLC control module first controls the hydraulic coarse adjustment unit to perform preliminary displacement compensation, and then controls the spiral fine adjustment unit to perform precise displacement compensation, so that the differential settlement value returns to the allowable range.

[0010] Preferably, in step S4, the strength grade of the shrinkage-compensating steel fiber concrete is one grade higher than that of the original structure, it is vibrated and compacted during the pouring process, and the curing time is ≥14 days; The depth of the rebar installation is ≥10d, where d is the diameter of the rebar.

[0011] Preferably, in step S6, the first threshold value for the compensation settlement difference is preset to be 0.5-2mm, and the adjustable support is fine-tuned by starting the screw fine-tuning unit through the PLC controller. The second threshold for compensating for differential settlement is preset to be 2-5mm. Grouting of the grouting reinforcement layer is initiated, and dual compensation is achieved by adjusting the adjustable support. The grouting volume is 0.5-1.0m³ per meter. If the preset threshold for the compensation settlement difference is ≤0.5mm and remains stable for 7 consecutive days, the bidirectional self-locking nut of the adjustable support is locked to stop active compensation.

[0012] Preferably, the settlement monitoring sensor network includes fiber Bragg grating sensors and hydrostatic levels.

[0013] An active control system for differential settlement between old and new bridge widening connections, used to implement a construction method for controlling differential settlement between old and new bridge widening, includes a settlement monitoring sensor network deployed on the top of the old bridge abutment, the top surface of the new bridge foundation, the bottom of the beam, and the depth of the foundation, for real-time monitoring of settlement data; Adjustable supports, installed on the base, are used to support and adjust the vertical displacement of the superstructure of the new bridge; The foundation grouting reinforcement pipeline is connected to the foundation around and between the new and old bridge foundations for pressure grouting. The PLC control module is communicatively connected to the settlement monitoring sensor network, the drive device of the adjustable bearing, and the control valve of the foundation grouting reinforcement. The PLC control module is configured to: receive and process data from the settlement monitoring sensor network, calculate differential settlement values, and, when the differential settlement value triggers a preset threshold, issue control commands to the drive device of the adjustable bearing or the control valve of the foundation grouting reinforcement. Preferably, the PLC control module has pre-set control logic including a PID control algorithm, which is used to optimize and generate the control instructions based on historical data and real-time trends of differential settlement.

[0014] The beneficial effects are: 1. When the differential settlement reaches the preset first threshold, the screw jack can be started by the PLC controller to fine-tune the adjustable support. When the differential settlement reaches the preset second threshold, the grouting reinforcement layer is started. Combined with the adjustment of the adjustable support, dual compensation is achieved. When the preset threshold of differential settlement is less than the first threshold, the bidirectional self-locking nut of the adjustable support is locked to stop the active compensation. Through the high-precision active compensation system, the problem of cracks and damage caused by uneven settlement at the connection between the old and new bridges is fundamentally avoided.

[0015] 2. Through a closed-loop control system of "monitoring-analysis-compensation", the new and old bridges can deform and share the load on the soft soil foundation, which greatly eliminates the structural safety hazards caused by differential settlement and ensures the long-term traffic safety and service life of the bridges. Attached Figure Description

[0016] Figure 1 This is a schematic diagram of the construction process of the present invention. Detailed Implementation

[0017] The specific embodiments of the present invention will be further described below with reference to the accompanying drawings.

[0018] The core of the construction method for controlling differential settlement at the connection between old and new bridges during bridge widening lies in the integrated closed-loop control system of "active monitoring and dynamic compensation". By deploying a high-precision monitoring network and adjustable bearing compensation devices at the connection between the old and new bridges, the differential settlement is detected in real time and compensation actions are automatically triggered, thereby achieving millimeter-level precise control of differential settlement. The entire process is deeply integrated with the bridge widening construction flow, including old bridge assessment, foundation pretreatment, compensation system installation, new bridge construction, real-time compensation, and final connection.

[0019] like Figure 1 As shown, the steps include: S1, On-site Investigation and Design Optimization: First, a precise leveling measurement was conducted to determine the current settlement stability of the old bridge. Simultaneously, a detailed geological survey was carried out on the foundation of the widened section to clarify the thickness and distribution of soft soil layers (such as silt and silty clay). Based on this data, the grouting reinforcement range and grouting parameters were designed, and the location and number of adjustable bearings and monitoring points were determined. The geological conditions of the connection section between the old and new bridges, the structural condition of the old bridge, and the current settlement status were reviewed. A level was used to measure the elevation of the old bridge structure. Combined with the geological survey report, the foundation reinforcement range, grouting parameters, and compensation device layout scheme were determined. This embodiment... The materials used include P.O42.5 ordinary Portland cement (compliant with GB175-2007 standard), water glass with a modulus of 2.8-3.2 (used for preparing two-component grout), industrial-grade bentonite modifier to improve grout fluidity and stability, C40-C50 shrinkage-compensating steel fiber reinforced concrete, HRB400 grade steel bars, adjustable supports (including hydraulic jacks and screw jacks), geological drilling rig (XY-100 type), grouting pump (3SNS type), high-precision fiber optic settlement sensor (accuracy ±0.01mm), hydrostatic level (DS05 type), PLC controller (programmable logic controller), and data acquisition instrument. The equipment was calibrated and debugged before entering the site. S2, Foundation Co-treatment: Before the construction of the new bridge foundation, inspect the structural integrity of the old bridge abutments and beams, repair any cracks or damage, clean the top of the old bridge abutments of debris and laitance, grind them smooth, and pour a 50mm thick C30 fine aggregate concrete leveling layer, ensuring its flatness deviation is ≤3mm / m, providing a solid foundation for the bearing installation. Assess the settlement stability of the old bridge foundation. If the settlement is not yet stable, preloading treatment of the old bridge is required to improve the compaction of the foundation soil (if the thickness of the sediment at the pile bottom exceeds the specification requirements (friction piles ≤0.15d, d...). (Pile diameter), after cleaning the sediment using high-pressure water jetting, grouting reinforcement is carried out at the pile bottom. In the soft soil foundation below the new bridge foundation and the connection section between the old and new bridges, grouting holes are arranged in a quincunx pattern (hole spacing 1.5-2m, hole diameter φ100-150mm, hole depth penetrating the soft soil layer to the hard plastic silty clay layer). The grouting pipe adopts a double-layer sleeve structure (inner grouting pipe + outer protective pipe) to prevent the hole wall from collapsing. A grout diffuser is installed at the bottom to expand the grout diffusion range. The grout is prepared using cement-water glass double-liquid grout for pressure grouting. The grouting pressure is controlled at 0.5-0.8MPa to fill the soil pores and improve the foundation bearing capacity to no less than 150kPa. After the new bridge superstructure is installed, sandbags and water bags are used to preload the structure with a load equivalent to 1.1 times the design load, which continues until the settlement rate is ≤0.3mm / d. The preloading time is 3-5 months to eliminate most of the post-construction settlement. S3, Compensation Device Installation: A C40 concrete base (500×500×100mm) is poured on the old bridge abutment and the foundation of the new bridge. Pre-drilled bolt holes are provided for the base. The horizontal deviation of the base top surface is ≤0.2mm / m. Adjustable supports are installed on the concrete base. The new bridge superstructure is then installed on top of the adjustable supports. These adjustable supports have dual functions: hydraulically driven large-stroke coarse adjustment (0-100mm) and screw-driven high-precision fine adjustment (accuracy ±0.1mm). The adjustable support includes, from top to bottom, a support top plate, a hydraulic coarse adjustment unit, a screw-driven fine adjustment unit, and a support bottom plate. The adjustable unit is used for large-stroke displacement compensation, and the screw fine-tuning unit is used for millimeter-level precision displacement compensation. Adjustable supports are evenly distributed transversely along the bottom of the beam of the new and old bridge connection section, with a spacing of 2-3m. The bottom plate of the adjustable support is fixed to the concrete base. After adjusting the levelness of the adjustable support, the top plate of the adjustable support is installed and fitted to the bottom of the new bridge body. The load-bearing capacity of a single adjustable support is ≥500kN, and the lifting stroke is 0-100mm. The hydraulic jack realizes rapid coarse adjustment, and the screw jack realizes high-precision fine adjustment (accuracy ±0.1mm). After installation, the reliability of the locking device is tested to ensure that there is no displacement under load. S4, New Bridge Erection: Install the hollow slabs or box girders of the new bridge using conventional processes, ensuring the installation elevation of the beams deviates from that of the old bridge by ≤5mm. Reserve a wet joint (50-80cm wide) at the junction of the new and old bridges to allow for adjustment space for settlement compensation. The wet joints are poured using shrinkage-compensating steel fiber concrete, with a strength grade one level higher than the original structure. The concrete is vibrated and compacted during pouring, and the curing time is ≥14 days. Add reinforcement to the splice joints and connection points. The steel reinforcement is connected to the old and new bridges using a rebar anchoring process, with an anchoring depth ≥10d (d is the diameter of the rebar). The pull-out resistance meets the design requirements. S5, Deployment of Settlement Co-control System: During the construction and operation phases, fiber optic settlement sensors (accuracy ±0.01mm) network (≥3 per connection section) and hydrostatic level (accuracy ±0.1mm) are deployed at key locations such as the top of the old bridge abutment, the top surface of the new bridge foundation, the bottom of the beam, and deep in the foundation. All sensors are connected to the PLC data acquisition and control system, with the sampling frequency set to 1 time / hour. The linkage response performance is tested by simulating settlement scenarios to ensure that a compensation command can be triggered within 30 seconds when the settlement difference is ≥2mm. S6, Real-time monitoring and dynamic compensation: Sensors continuously collect settlement data at a frequency of 1 time / hour. Settlement data of the new and old bridges are obtained in real time through the settlement monitoring sensor network. The PLC control module calculates the real-time differential settlement value. When the real-time differential settlement value reaches the preset first threshold (0.5-2mm), the PLC control module generates the first control command to drive the screw jack in the adjustable bearing to perform vertical displacement compensation by fine-tuning the bearing and compensating for the settlement difference. When the real-time differential settlement value reaches the preset second threshold (>2mm or settlement rate exceeds 0.3mm / d), the PLC control module generates the second control command to start the grouting device and combine it with the adjustable bearing to adjust the foundation for pressure grouting compensation. The grouting amount is 0.5-1.0m³ per meter. When the real-time differential settlement value is less than the preset first threshold (≤0.5mm) and has been stable for 7 consecutive days, the bidirectional self-locking nut of the adjustable bearing is locked to stop active compensation. S7, Connection Section: After the settlement stabilizes, the wet joint is subjected to secondary grouting to ensure a tight connection. A semi-rigid connection method is adopted, allowing a certain degree of relative deformation to reduce the impact of uneven settlement on the connection. The flatness of the connection section between the new and old bridges is tested (deviation ≤3mm / 3m), the settlement difference (≤0.5mm), and structural cracks (no visible cracks). The bearing capacity of the foundation is tested to be ≥150kPa, meeting the design requirements. The adjustable bearings are hot-dip galvanized for corrosion protection (galvanizing amount ≥600g / m²). The bearing capacity is retested after 7 days of curing of the grouting reinforcement layer. S8, Acceptance and Operation Monitoring: Submit construction records, monitoring data reports, test reports and other materials, conduct special acceptance, monitor settlement data once a week during the first 3 months of bridge operation, and monitor once a quarter thereafter, continuously track settlement stability, and conduct corrosion inspection and functional verification of the compensation device once a year.

[0020] An active control system for differential settlement during bridge widening and connection between old and new bridges is disclosed. This system includes a settlement monitoring sensor network deployed at the top of the old bridge abutments, the top surface of the new bridge foundation, the bottom of the beams, and the depth of the foundation for real-time settlement monitoring; adjustable bearings installed on the foundation to support and adjust the vertical displacement of the new bridge superstructure; grouting reinforcement pipelines connected to the foundations surrounding and between the old and new bridge foundations for pressure grouting; and a PLC control module communicatively connected to the settlement monitoring sensor network, the drive unit of the adjustable bearings, and the control valve for the grouting reinforcement. The PLC control module is configured to receive and process data from the settlement monitoring sensor network, calculate the differential settlement value, and issue control commands to the drive unit of the adjustable bearings or the control valve for the grouting reinforcement when the differential settlement value triggers a preset threshold.

[0021] The PLC control module has pre-set control logic including a PID control algorithm, which is used to optimize and generate control commands based on historical data and real-time trends of differential settlement.

[0022] The embodiments of the present invention described above do not constitute a limitation on the scope of protection of the present invention. The basic concept of the present invention lies in fundamentally avoiding the problems of cracks and damage caused by uneven settlement at the junction of new and old bridges through a high-precision active compensation system. This ensures that the new and old bridges can deform and share the load on soft soil foundations, greatly eliminating structural safety hazards caused by differential settlement and guaranteeing the long-term traffic safety and service life of the bridges. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the scope of protection of the claims of the present invention.

Claims

1. A construction method for controlling differential settlement between old and new bridge widening sections, characterized by: Includes the following steps: S1, On-site investigation and design optimization: Review the geological conditions of the connection section between the old and new bridges, the structural status of the old bridge and the current settlement status, use a level to measure the elevation of the old bridge body, and determine the foundation reinforcement range, grouting parameters and compensation device layout scheme in conjunction with the geological investigation report. S2, Foundation Co-treatment: Before the construction of the new bridge foundation, the integrity of the old bridge abutment and beam structure is tested, and any cracks or damage are repaired. The settlement stability of the old bridge foundation is assessed. If the settlement is not yet stable, the old bridge needs to be preloaded to improve the compactness of the foundation soil. S3, Installation of compensation device: Concrete base is poured on the old bridge abutment and the foundation of the new bridge, adjustable bearing is installed on the concrete base, and the superstructure of the new bridge is installed on the upper end of the adjustable bearing. S4, New bridge construction: Wet joints are reserved at the junction of the new and old bridges to allow for adjustment space for settlement compensation. Wet joints are poured with compensating shrinkage steel fiber concrete, and reinforcement is added to the splice joints and connection parts. S5, Settlement Co-control System Deployment: During the construction and operation phases, a settlement monitoring sensor network is deployed on the top of the old bridge abutment, the top surface of the new bridge foundation, the bottom of the beam, and deep in the foundation. The output end of the settlement monitoring sensor network, the adjustment drive device of the adjustable support, and the controller of the grouting device used for foundation reinforcement grouting are all connected to the PLC control module. S6, Real-time monitoring and dynamic compensation: The settlement data of the new and old bridges are acquired in real time through the settlement monitoring sensor network. The PLC control module calculates the real-time differential settlement value. When the real-time differential settlement value reaches the preset first threshold, the PLC control module generates the first control command to drive the adjustable bearing to perform vertical displacement compensation. When the real-time differential settlement value reaches the preset second threshold, the PLC control module generates the second control command to start the grouting device to perform pressure grouting compensation on the foundation. When the real-time differential settlement value is less than the preset first threshold and has been stable for 7 consecutive days, the bidirectional self-locking nut of the adjustable bearing is locked to stop active compensation. S7, Connection Section: After the settlement stabilizes, the wet joint is subjected to secondary grouting treatment to ensure a tight connection. The flatness and structural cracks of the connection section between the new and old bridges are tested to ensure that the design requirements are met. The adjustable bearing is subjected to hot-dip galvanizing for corrosion protection. The bearing capacity is retested 7 days after the grouting reinforcement layer is cured. S8, Acceptance and Operation and Maintenance Monitoring: Submit construction records, monitoring data reports, and test reports, conduct special acceptance, monitor settlement data once a week during the first 3 months of bridge operation, and monitor once a quarter thereafter, continuously track settlement stability, and conduct corrosion inspection and functional verification of the compensation device once a year.

2. The construction method for controlling differential settlement at the connection between old and new bridge widening sections according to claim 1, characterized in that, In step S2, the specific steps of the foundation grouting reinforcement include: arranging grouting holes in a quincunx pattern in the foundation and abutment backfill area of ​​the new and old bridge connection section, with a hole spacing of 1.5-2m, a hole diameter of φ100-150mm, and a hole depth penetrating from the soft soil layer to the hard plastic silty clay layer, using a double-layer sleeve structure to prevent hole wall collapse; installing a grout diffuser at the bottom to expand the grout diffusion range, and grouting pressure of 0.5~0.8Mpa.

3. The construction method for controlling differential settlement at the connection between old and new bridge widening sections according to claim 1, characterized in that, In step S3, the concrete base has dimensions of 500×500×100mm, with pre-drilled bolt holes for fixing the support, and the top surface of the base has a horizontal deviation of ≤0.2mm / m.

4. The construction method for controlling differential settlement at the connection between old and new bridge widening sections according to claim 3, characterized in that, In step S3, the adjustable support includes a support top plate, a hydraulic coarse adjustment unit, a spiral fine adjustment unit, and a support bottom plate arranged from top to bottom; Adjustable supports are evenly distributed transversely along the bottom of the beam of the new and old bridge connection section, with a spacing of 2-3m. The bottom plate of the support is fixed on the concrete base. After adjusting the levelness of the adjustable support, the top plate of the support is installed and fits against the bottom of the new bridge body.

5. The construction method for controlling differential settlement at the connection between old and new bridge widening sections according to claim 4, characterized in that, In step S5, the PLC control module first controls the hydraulic coarse adjustment unit to perform preliminary displacement compensation, and then controls the spiral fine adjustment unit to perform precise displacement compensation, so that the differential settlement value returns to the allowable range.

6. The construction method for controlling differential settlement at the connection between old and new bridge widening sections according to claim 1, characterized in that, In step S4, the strength grade of the shrinkage-compensating steel fiber concrete is one grade higher than that of the original structure. During the pouring process, it is vibrated to ensure compaction, and the curing time is ≥14 days. The depth of the rebar installation is ≥10d, where d is the diameter of the rebar.

7. The construction method for controlling differential settlement at the connection between old and new bridge widening sections according to claim 1, characterized in that, In step S6, the first threshold value for the compensation settlement difference is preset to be 0.5-2mm, and the adjustable support is fine-tuned by starting the screw fine-tuning unit through the PLC controller. The second threshold for the compensation settlement difference is preset to be 2-5mm. Grouting of the grouting reinforcement layer is started, and dual compensation is achieved by adjusting the adjustable support. The grouting volume is 0.5-1.0m³ per meter. If the preset threshold for the compensation settlement difference is ≤0.5mm and remains stable for 7 consecutive days, the bidirectional self-locking nut of the adjustable support is locked to stop active compensation.

8. The construction method for controlling differential settlement at the connection between old and new bridge widening sections according to claim 1, characterized in that, The settlement monitoring sensor network includes fiber optic grating sensors and hydrostatic levels.

9. An active control system for differential settlement at the connection between old and new bridge widening sections, as described in any one of claims 1-8, characterized in that, This includes a settlement monitoring sensor network, which is deployed on the top of the old bridge abutments, the top surface of the new bridge foundation, the bottom of the beams, and deep into the foundation, for real-time monitoring of settlement data; Adjustable supports, installed on the base, are used to support and adjust the vertical displacement of the superstructure of the new bridge; The foundation grouting reinforcement pipeline is connected to the foundation around and between the new and old bridge foundations for pressure grouting. The PLC control module is communicatively connected to the settlement monitoring sensor network, the drive device of the adjustable support, and the control valve of the foundation grouting reinforcement. The PLC control module is configured to receive and process the data of the settlement monitoring sensor network, calculate the differential settlement value, and issue a control command to the drive device of the adjustable support or the control valve of the foundation grouting reinforcement when the differential settlement value triggers a preset threshold.

10. The active control system for differential settlement at the connection between old and new bridge width extensions according to claim 9, characterized in that, The PLC control module is pre-loaded with control logic including a PID control algorithm, which is used to optimize and generate the control commands based on historical data and real-time trends of differential settlement.

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