Reconstruction structure of old bridge based on existing river bank protection and construction method thereof

Abstract

This invention provides a bridge renovation structure and construction method based on existing riverbank revetments. The renovation structure, based on the existing riverbank revetment, includes existing pile foundations, vertical retaining structures, abutments, bridge abutments, and revetment reinforcement structures. The abutments are constructed on the top surface of the retained area below the vertical retaining structures after the upper part of the vertical retaining structures is removed. The top surface of the abutments is not higher than the river's design water level. The bridge abutments are located above the abutments and are used to erect the bridge deck box girders. The revetment reinforcement structure includes newly constructed reinforcing pile foundations and prestressed anchor cables deployed in the retained area below the vertical retaining structures. This invention maximizes the use of existing riverbank revetments in the overall bridge load-bearing capacity, solves the renovation construction problem when space is limited on both sides of urban rivers, optimizes the river's cross-section, improves flood control capacity, reduces construction risks, and increases renovation efficiency.

Description

Technical Field

[0001] This invention belongs to the field of bridge engineering technology, specifically relating to the structural renovation and upgrading of cross-river bridges adapted to urban river space constraints, and particularly to an old bridge renovation structure and its construction method that utilizes existing riverbank protection to achieve synergistic stress distribution. Background Technology

[0002] With the continuous advancement of urbanization, the urban river-crossing bridges built in the early stages, mainly including single-span or multi-span simply supported beam bridges, are gradually facing a dual challenge: on the one hand, the explosive growth of urban traffic flow means that the technical standards, load-bearing capacity, and traffic efficiency of the old bridges can no longer meet the current needs of urban arterial roads, making bridge renovation and upgrading an inevitable choice to alleviate regional traffic pressure and ensure traffic safety; on the other hand, relatively mature development patterns have formed on both sides of urban rivers, with densely distributed high-rise residential communities, commercial facilities, and underground pipelines, resulting in extremely scarce land resources and very limited space available for bridge construction.

[0003] Traditional urban bridge reconstruction projects typically employ a "demolition and reconstruction + slope excavation" model. This involves first demolishing the old bridge structure, then extensively excavating from the riverbed to the ground on both sides, and finally pouring in a new gravity-type abutment structure. However, this approach has significant technical drawbacks: First, it has poor spatial adaptability, as slope excavation requires a large amount of land on both sides of the river, and there is currently insufficient space around the existing river, making construction highly impractical. Second, it poses significant safety risks, as extensive excavation easily creates high slopes, resulting in not only a large amount of excavation work and a long construction period, but also the potential for slope instability and collapse, directly threatening the stability of nearby building foundations, the safety of building structures, and the integrity of surrounding underground pipelines, green spaces, and other municipal facilities. Third, it causes significant environmental disruption, with noise and dust pollution generated during construction significantly interfering with the river's ecological environment and residents' daily lives. Furthermore, it is inefficient, with cumbersome excavation, support, earthwork removal, and backfilling processes leading to a lengthy construction period, making it difficult to meet the urgent needs of urban traffic reconstruction.

[0004] Therefore, given the limited space on both sides of urban waterways and the sensitive surrounding environment, traditional bridge renovation technologies are no longer adequate for actual engineering needs. There is an urgent need for a new bridge renovation structure and construction method that can make full use of existing resources, reduce the scale of excavation, lower construction risks, and improve construction efficiency. Summary of the Invention

[0005] This invention addresses the shortcomings of existing technologies by providing a bridge renovation structure and construction method based on existing riverbank revetments. This renovation structure is mainly designed for the renovation of small bridges spanning rivers in cities, maximizing the use of existing riverbank revetments in the overall load-bearing capacity of the bridge, solving the renovation construction problem when space is limited on both sides of urban rivers, optimizing the river's cross-section, improving flood discharge capacity, reducing construction risks, and increasing renovation efficiency.

[0006] To achieve the above-mentioned technical objectives, this invention provides a bridge renovation structure based on existing riverbank protection, mainly targeting the abutment area of ​​simple bridges in urban waterways. The renovation structure is based on the existing riverbank protection structure, which includes existing pile foundations and vertical retaining structures. The renovation structure includes a pier cap, abutment, and bank reinforcement structure. The pier cap is constructed on the top surface of the retained area below the vertical retaining structure after the upper part of the vertical retaining structure is removed. The bottom surface of the pier cap is tightly connected to the retained area below the vertical retaining structure through a rebar reinforcement connection structure. The top surface of the pier cap is not higher than the design water level of the river. The abutment is located above the pier cap and is used to erect the bridge deck box girder.

[0007] The revetment reinforcement structure includes newly constructed reinforcing piles and prestressed anchor cables installed in the reserved area below the vertical retaining structure. The prestressed anchor cables are driven obliquely into the water-facing surface of the reserved area below the vertical retaining structure, and their anchoring sections extend into the bedrock layer of the revetment area. The newly constructed reinforcing piles are located below the pile cap and together with the existing piles, support the pile cap.

[0008] A further technical solution of the present invention: the combined vertical bearing capacity R of the existing pile foundation and the newly built reinforcing pile foundation should be greater than the total vertical load F transmitted by the bridge superstructure; the specific formula is as follows: ;

[0009] In the formula, This represents the sum of the vertical bearing capacities of all existing pile foundations. n 旧 Ra represents the total number of existing pile foundations, and Ra represents the vertical bearing capacity of a single existing pile foundation. This represents the sum of the vertical bearing capacities of all newly constructed and reinforced pile foundations. n 新 Rb represents the total number of newly constructed reinforcing piles, and Rb represents the vertical bearing capacity of a single newly constructed reinforcing pile. is the pile group effect coefficient, usually taken as 0.7 to 1.0; G is the permanent load; Q is the variable load;

[0010] The permanent load G and the variable load Q are both taken in accordance with the requirements of the "General Specifications for Design of Highway Bridges and Culverts" or the "Specifications for Design of Urban Bridges".

[0011] The preferred technical solution of the present invention is as follows: the modified structure is located in the abutment modification area at both ends of the bridge deck box girder, the modified structures at both ends are the same, and are constructed based on the revetment structures on both sides of the river channel; the two ends of the bridge deck box girder are respectively installed on the abutments on the corresponding sides by supports, and bridge approach slabs are respectively provided at both ends of the bridge deck box girder.

[0012] The preferred technical solution of the present invention is as follows: the newly built reinforcing piles are evenly distributed with the existing piles, and the pile spacing and pile length of the newly built reinforcing piles are the same as those of the existing piles; both the newly built reinforcing piles and the existing piles are made of reinforced concrete cast-in-place piles, and the pile bottom is embedded in the bedrock layer to a depth of ≥5 times the pile diameter.

[0013] The preferred technical solution of this invention is as follows: the lower reserved area of ​​the vertical support structure is made to have an anti-slip stability coefficient Kc≥1.3 and an anti-overturning stability coefficient K0≥1.5 by adding prestressed anchor cables; the horizontal spacing of the prestressed anchor cables is 2-4m, the vertical spacing is 2-3m, and the anchor cable inclination angle θ is 15-30°; the prestressed anchor cables are divided into a free section and an anchoring section, the length of the free section is ≥5m, and the anchoring section extends into the stable moderately weathered / slightly weathered rock base; the anchor hole positioning deviation of the prestressed anchor cables is not greater than 20mm, the drilling inclination deviation is not greater than 2%, and the drilling depth exceeds the design length of the anchor rod by not less than 0.5m.

[0014] The preferred technical solution of the present invention is as follows: the top surface of the pier is flush with the design water level of the river channel, and the rebar reinforcement connection structure includes a roughened contact surface between the new and old structures and multiple rebars. After roughening the top surface of the area reserved at the bottom of the vertical support structure, multiple rebar holes are opened. The lower part of the rebar is inserted into the corresponding rebar hole, and the rebar hole is filled with modified epoxy or modified vinyl ester structural rebar adhesive. The upper part of the multiple rebars extends to the concrete pouring area of ​​the pier and is integrated with the pier during concrete pouring.

[0015] This invention also provides a construction method for the renovation of old bridges based on existing riverbank revetments. The renovation mainly targets the transformation of existing low-standard, simple bridges in urban waterways. Riverbank revetments are constructed on both sides of the urban waterway, and the renovation structure is built upon the existing revetment structure. The specific construction steps are as follows:

[0016] S1. Demolition of the old bridge structure; demolition of the existing low-standard bridge deck structure, lightweight abutments, and original bridge piers in the river channel.

[0017] S2. Determine the number of newly constructed reinforcement piles; obtain the vertical compressive bearing capacity Ra of the existing piles in the riverbank protection structure through static load tests, and determine the number of existing piles n. 旧 Then calculate the total vertical bearing capacity of all existing pile foundations. The minimum composite vertical bearing capacity R of the pile group is determined based on the total vertical load F transmitted by the bridge superstructure. The composite vertical bearing capacity R of the pile group satisfies: R≧F.

[0018] The minimum total vertical bearing capacity of newly constructed reinforced pile foundations is calculated using the following formula. :

[0019] ;

[0020] This is the group pile effect coefficient, typically taken as 0.7 to 1.0;

[0021] ,

[0022] n 新 Rb represents the total number of newly constructed reinforcing piles, and Rb represents the vertical bearing capacity of a single newly constructed reinforcing pile.

[0023] And based on the calculated total minimum vertical bearing capacity of the newly constructed reinforced pile foundation. The number of new reinforcement piles will be determined based on the site conditions.

[0024] S3. Construction of new reinforced pile foundations; On the existing ground surface, the new reinforced pile foundations are measured and positioned according to the design requirements. The new reinforced pile foundations are constructed using bored cast-in-place pile technology to ensure that the depth of the pile bottom embedded in the bedrock layer is ≥ 5 times the pile diameter; The part above the design elevation of the pile top is treated as an empty pile.

[0025] S4. Bank protection renovation and foundation pit excavation; The existing riverbank protection structure is divided into a retained area at the bottom of the vertical support structure and a demolition area at the top of the vertical support structure, with the design height of the bottom surface of the pier as the dividing line. The design height of the bottom surface of the pier is equal to the design water level of the river channel minus the thickness of the pier. The upper demolition area of ​​the vertical support structure is demolished to the design height of the bottom surface of the pier. Simultaneously, the upper backfill is excavated to the design elevation of the bottom surface of the pier. Based on the surrounding construction conditions and the excavation depth, the slope excavation or vertical excavation after retaining pile support is selected.

[0026] S5. Reinforcement of the lower retaining area of ​​the vertical retaining structure; Prestressed anchor cables are installed on the water-facing sidewall of the lower retaining area of ​​the vertical retaining structure to ensure that the anti-slip stability coefficient Kc ≥ 1.3 and the anti-overturning stability coefficient K0 ≥ 1.5; The horizontal spacing of the prestressed anchor cables is 2-4m, the vertical spacing is 2-3m, and the anchor cable inclination angle θ is 15-30°; The prestressed anchor cables are divided into a free section and an anchoring section. The length of the free section is ≥ 5m, and the anchoring section extends into the stable moderately weathered / slightly weathered rock base. After the anchor cables are tensioned to the design value, the anchor head is sealed with fine stone concrete.

[0027] S6. Foundation pouring construction: The contact surface between the lower part of the vertical retaining structure and the foundation is roughened, loose soil and construction debris are removed, rebar holes are drilled on the roughened surface and rebars are inserted, and rebar adhesive is filled in; after the contact surface between the new and old structures is moistened, an interface agent is applied, and foundation concrete is poured according to the design requirements.

[0028] S7. Bridge abutment and roadbed backfilling construction; construct bridge abutments and bearings, and backfill the area behind the abutments with crushed stone soil in layers and compact it with a compaction degree ≥96%;

[0029] S8. Construction of the bridge superstructure: The bridge approach slabs and superstructure box girders are constructed in sequence to complete the overall bridge structure construction.

[0030] A preferred technical solution of the present invention: In step S2, the newly constructed reinforcing piles are evenly distributed with the existing piles, and the pile spacing and pile length of the newly constructed reinforcing piles are the same as those of the existing piles, then Rb=Ra; and the number of newly constructed reinforcing piles n is calculated according to the formula. 新 The minimum value; the total vertical load F transmitted by the bridge superstructure in step S2 is calculated according to the following formula:

[0031]

[0032] In the formula, G is the permanent load; Q is the variable load;

[0033] The permanent load G and the variable load Q are both taken in accordance with the requirements of the "General Specifications for Design of Highway Bridges and Culverts" or the "Specifications for Design of Urban Bridges"; the permanent load includes the bridge's self-weight, prestress, and soil and water pressure; the variable load includes vehicle load, pedestrian load, temperature load, wind load, and seismic load.

[0034] The preferred technical solution of the present invention is as follows: In step S5, the anchor hole positioning deviation of the prestressed anchor cable is no more than 20mm, the drilling inclination deviation is no more than 2%, and the drilling depth exceeds the design length of the anchor rod by no less than 0.5m; grouting is performed using the bottom-hole return grouting method, with the grouting pressure controlled at 0.6-1.0MPa. Before the initial setting of the normal pressure grouting, a high-pressure grouting pump is used to perform secondary grouting at a pressure of 2.0-4.0MPa; after constructing the reinforced concrete anchor pier, prestressing tensioning and locking are performed. After the anchor cable is tensioned to the design value, C30 non-shrink fine stone concrete is used to complete the anchor head sealing.

[0035] The preferred technical solution of the present invention is as follows: the reinforcing bars implanted in step S6 are HRB400 ribbed steel bars, the spacing between the reinforcing bars is 0.2 to 0.5 m, the implantation depth is ≥0.5 m, the shear strength of the adhesive bonding is ≥11 MPa, and the compressive strength is ≥50 MPa.

[0036] This invention involves dismantling existing low-grade bridge structures within river channels, evaluating the load-bearing capacity and durability of existing riverbank revetments, and proposing a bridge reconstruction structure based on the synergistic force-bearing capacity of the riverbank revetments. This structure fully utilizes the vertical retaining structure of the riverbank revetments and existing pile foundations as the core components of the foundation beneath the bridge abutment, further reinforcing the pile foundations. Simultaneously, the lower vertical retaining structure is tightly connected to the upper abutment through steel reinforcement inserted at the interface between the old and new structures, achieving synergistic force-bearing capacity between the old and new structures to meet the overall load-bearing requirements of high-grade cross-river bridges. This invention utilizes the existing vertical revetment structure of urban river channels as the basis for synergistic force-bearing capacity, integrating the existing structure with newly added reinforcing pile foundations to form a stable bridge load-bearing system, thereby improving the technical standards and load-bearing capacity of urban cross-river bridges.

[0037] Compared with the prior art, the present invention can achieve the following beneficial effects:

[0038] (1) High space utilization and significantly reduced construction risks: This invention makes full use of the existing riverbank protection structure as a component of the bridge foundation, eliminating the need for large-scale slope excavation from the riverbed to the original ground as in traditional schemes. This avoids the safety hazards of high slope instability and collapse from the root, effectively protects the stability of the foundation of nearby buildings and the integrity of surrounding municipal facilities, and is perfectly suited to the scenario of limited space and scarce land resources on both sides of urban river channels.

[0039] (2) The project is green and efficient, and the engineering benefits are outstanding. By maximizing the use of the existing revetment and pile foundation structure, the amount of engineering work, material usage and construction difficulty of foundation construction are reduced, and the recycling of engineering resources is realized. At the same time, the cumbersome procedures such as large-scale excavation, foundation pit support, earthwork transportation and backfilling in the traditional scheme are eliminated, the construction cycle is shortened by more than 30%, and the costs of earthwork engineering, support engineering and indirect costs such as machinery rental and labor are greatly reduced, resulting in significant economic benefits.

[0040] (3) It has little ecological impact and meets the requirements of green infrastructure. The reduced excavation scale reduces construction noise and dust pollution, and reduces interference with the river's ecological environment and residents' normal life. After the old bridge structure that encroached on the water crossing section was demolished, the river's flood discharge space was optimized, and the flood control safety guarantee capacity was improved, which meets the dual needs of ecological environmental protection and flood control and disaster reduction.

[0041] (4) It is highly adaptable and has a wide range of applications. It is not only suitable for the renovation of bridges on both sides of urban rivers where the development is mature and space is limited, but also allows for flexible adjustment of reinforcement schemes according to the actual conditions of riverbank protection. It can also supplement slope protection design for areas without bank protection, adapt to different river environments and bridge grade requirements, and provide reliable technical support for the renovation and upgrading of various urban cross-river bridges. It has broad application prospects. Attached Figure Description

[0042] Figure 1This is a longitudinal section view of the old bridge renovation structure in this invention;

[0043] Figure 2 This is a longitudinal section view of the bridge structure during the renovation of the old bridge in this invention;

[0044] Figure 3 for Figure 2 Plan layout of the Zhongzhong Old Bridge renovation structure;

[0045] Figure 4 Detailed diagram of rebar installation for the connection between the old and new structures.

[0046] Attached reference numerals: 1-Existing pile foundation; 2-Vertical retaining structure; 201-Preserved area below the vertical retaining structure; 202-Demolition area above the vertical retaining structure; 3-Design water level of the river channel; 4-Prestressed anchor cable; 5-Rebar reinforcement connection structure; 501-Roughened surface of the contact between the old and new structures; 502-Rebar installation; 503-Rebar hole; 6-Pile cap; 7-Abutment; 701-Support; 8-Bridge approach slab; 9-Bridge deck box girder; 10-Newly built reinforcing pile foundation; 11-Lightweight abutment of the original bridge; 12-Original bridge pier. Detailed Implementation

[0047] The present invention will be further described below with reference to the accompanying drawings and embodiments. Figures 1 to 4 All accompanying drawings are simplified versions of embodiments and are intended only to clearly and concisely illustrate the embodiments of the present invention. The technical solutions shown in the drawings below are specific solutions of embodiments of the present invention and are not intended to limit the scope of the claimed invention. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without inventive effort are within the scope of protection of the present invention.

[0048] In the description of this invention, it should be understood that the terms "upper," "lower," "inner," "outer," "left," "right," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings, or the orientation or positional relationship commonly used when the product of this invention is in use, or the orientation or positional relationship commonly understood by those skilled in the art. They are only used to facilitate the description of this invention and to simplify the description, and are not intended to indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this invention.

[0049] Example 1 provides a bridge renovation structure based on existing riverbank revetments, primarily targeting the abutment area of ​​simple bridges in urban waterways. The renovation structure is located in the abutment renovation areas at both ends of the bridge deck box girder 9. The renovation structures at both ends are identical and are constructed based on the revetment structures on both sides of the river. Figures 1 to 4As shown, the existing riverbank revetment structure includes existing pile foundations 1 and vertical retaining structure 2. The modified structure includes a pier cap 6, abutments 7, and revetment reinforcement structure. The pier cap 6 is constructed on the top surface of the lower retained area 201 of the vertical retaining structure after the upper area of ​​the vertical retaining structure 2 is removed. The bottom surface of the pier cap 6 is tightly connected to the lower retained area 201 of the vertical retaining structure through a rebar reinforcement connection structure 5. The top surface of the pier cap 6 is flush with the design water level line 3 of the river channel. The abutment 7 is located above the pier cap 6 and is used to erect the bridge deck box girder 9. The two ends of the bridge deck box girder 9 are respectively installed on the corresponding abutments 7 via supports 701. Bridge approach slabs 8 are respectively provided at both ends of the bridge deck box girder 9. Figure 4 As shown, the rebar reinforcement connection structure 5 includes a roughened contact surface 501 between the new and old structures and multiple rebars 502. After roughening the top surface of the reserved area 201 at the bottom of the vertical support structure, multiple rebar holes 503 are opened. The lower part of the rebars 502 is inserted into the corresponding rebar holes 503, and the rebar holes 503 are filled with modified epoxy or modified vinyl ester structural rebar adhesive. The upper part of the multiple rebars 502 extends to the concrete pouring area of ​​the foundation 6 and is integrated with the foundation 6 during concrete pouring. The roughening treatment of the contact surface between the new and old structures allows the new and old concrete structures to form an organic whole. The roughening depth of the contact surface 501 is 5cm, and the spacing is 10cm. After roughening the surface, HRB400 ribbed steel bars are used for rebar installation, with a rebar spacing of 0.2-0.5m and an insertion depth of ≥0.5m.

[0050] In the embodiments, such as Figures 1 to 3 As shown, the revetment reinforcement structure includes newly built reinforcing piles 10 and prestressed anchor cables 4 installed in the lower reserved area 201 of the vertical retaining structure. The prestressed anchor cables 4 are driven obliquely into the water-facing surface of the lower reserved area 201 of the vertical retaining structure, and their anchoring sections extend into the bedrock layer of the revetment area. The newly built reinforcing piles 10 are located below the pile cap 6 and together with the existing piles 1, they support the pile cap 6. The lower retaining area 201 of the vertical support structure is reinforced with prestressed anchor cables 4 to achieve a slip resistance stability coefficient Kc ≥ 1.3 and an overturning stability coefficient K0 ≥ 1.5. The prestressed anchor cables 4 have a lateral spacing of 2-4m, a vertical spacing of 2-3m, and an anchor cable inclination angle θ of 15-30°. The prestressed anchor cables 4 are divided into a free section and an anchoring section. The length of the free section is ≥ 5m, and the anchoring section extends into the stable moderately weathered / slightly weathered rock base. The anchor hole positioning of the prestressed anchor cables 4 deviates from the design by no more than 20mm, the drilling inclination deviation is no more than 2%, and the drilling depth exceeds the design length of the anchor rod by no less than 0.5m.

[0051] In the embodiments, such as Figure 3As shown, the newly constructed reinforcing piles 10 are evenly distributed in conjunction with the existing piles 1, and the pile spacing and length of the newly constructed reinforcing piles 10 are the same as those of the existing piles 1. Both the newly constructed reinforcing piles 10 and the existing piles 1 are reinforced concrete cast-in-place piles, with the pile bottom embedded in the bedrock layer to a depth ≥ 5 times the pile diameter. The combined vertical bearing capacity R of the pile group of the existing piles 1 and the newly constructed reinforcing piles 10 should be greater than the total vertical load F transmitted by the bridge superstructure; the specific formula is as follows:

[0052]

[0053] In the formula, This represents the sum of the vertical bearing capacities of all existing pile foundations. n 旧 Ra represents the total number of existing pile foundations, and Ra represents the vertical bearing capacity of a single existing pile foundation.

[0054] This represents the sum of the vertical bearing capacities of all newly constructed and reinforced pile foundations. n 新 Rb represents the total number of newly constructed reinforcing piles, and Rb represents the vertical bearing capacity of a single newly constructed reinforcing pile.

[0055] is the pile group effect coefficient, usually taken as 0.7 to 1.0; G is the permanent load; Q is the variable load;

[0056] The permanent load G and the variable load Q are both taken in accordance with the requirements of the "General Specifications for Design of Highway Bridges and Culverts" or the "Specifications for Design of Urban Bridges".

[0057] Example 2 provides a construction method for the renovation of an old bridge based on existing riverbank protection, as described in Example 1. The renovation primarily targets existing low-standard, simple bridges in urban waterways. These waterways have riverbank protection structures on both sides, consisting of pile foundations and vertical retaining structures. The pile foundations are typically reinforced concrete cast-in-place piles, and the vertical retaining structures are gravity retaining walls. The renovation structure is constructed based on the existing riverbank protection structure. The original bridge piers 12 of the existing low-standard bridge structure are located within the waterway on the water-facing side of the riverbank protection structure. The specific construction steps are as follows:

[0058] S1. Demolition of the old bridge structure; demolish the existing low-standard bridge deck structure, the original bridge abutment 11, and the original bridge piers 12 in the river channel, while accurately preserving the existing pile foundations 1 of the existing riverbank protection structure to avoid damaging the existing effective structure; by demolishing the existing structure in the river channel, eliminate the safety hazards of encroaching on the water passage section and affecting the flood discharge of the river channel.

[0059] S2. The number of newly constructed reinforcing piles is determined by calculation; the vertical compressive bearing capacity Ra of the existing pile foundation 1 of the riverbank protection structure is obtained through static load tests, and the number n of the existing pile foundation 1 is determined. 旧 Then calculate the total vertical bearing capacity of all existing pile foundations. The minimum composite vertical bearing capacity R of the pile group is determined based on the total vertical load F transmitted by the bridge superstructure. The composite vertical bearing capacity R of the pile group satisfies: R≧F.

[0060] The minimum total vertical bearing capacity of newly constructed reinforced pile foundations is calculated using the following formula. :

[0061] ;

[0062] This is the group pile effect coefficient, typically taken as 0.7 to 1.0;

[0063] ,

[0064] n 新 Rb represents the total number of newly constructed reinforcing piles, and Rb represents the vertical bearing capacity of a single newly constructed reinforcing pile.

[0065] The number of newly constructed reinforcement piles is determined based on the above technical formulas and the actual construction site conditions.

[0066] In Example 2, the newly constructed reinforcing piles 10 are evenly distributed with the existing piles 1, and the pile spacing and pile length of the newly constructed reinforcing piles 10 are the same as those of the existing piles 1. Therefore, Rb = Ra; and the number of newly constructed reinforcing piles n is calculated according to the formula. 新 The minimum value; then, in conjunction with the specific construction site design, the location of the newly built reinforcement pile foundation 10; the total vertical load F transferred by the bridge superstructure in step S2 is calculated according to the following formula:

[0067]

[0068] In the formula, G is the permanent load; Q is the variable load;

[0069] The permanent load G and the variable load Q are both taken in accordance with the requirements of the "General Specifications for Design of Highway Bridges and Culverts" or the "Specifications for Design of Urban Bridges"; the permanent load includes the bridge's self-weight, prestress, and soil and water pressure; the variable load includes vehicle load, pedestrian load, temperature load, wind load, and seismic load.

[0070] S3. Construction of new reinforced pile foundation 10; On the existing ground surface, measure and locate the new reinforced pile foundation 10 according to the design requirements, and construct the new reinforced pile foundation 10 using the bored cast-in-place pile technology, ensuring that the depth of the pile bottom embedded in the bedrock layer is ≥ 5 times the pile diameter, and ensuring that the composite vertical bearing capacity of the pile group of the new reinforced pile foundation 10 meets the design requirements in step S2. The part above the design elevation of the pile top is treated as an empty pile.

[0071] S4. Bank protection renovation and foundation pit excavation; The existing riverbank protection structure's vertical retaining structure 2 is divided into a lower retaining structure retention area 201 and an upper retaining structure demolition area 202, with the design height of the bottom surface of the pier 6 as the dividing line. The design height of the bottom surface of the pier is equal to the design water level of the river channel minus the thickness of the pier. The upper demolition area 202 of the vertical retaining structure is demolished to the design height of the bottom surface of the pier 6, and the upper backfill is excavated simultaneously to the design elevation of the bottom surface of the pier 6. Based on the surrounding construction conditions and excavation depth, the slope excavation or vertical excavation with retaining pile support is selected.

[0072] S5. Reinforcement of the lower retaining area of ​​the vertical retaining structure; constructing prestressed anchor cables 4 on the water-facing sidewall of the lower retaining area of ​​the vertical retaining structure to ensure that the anti-slip stability coefficient Kc ≥ 1.3 and the anti-overturning stability coefficient K0 ≥ 1.5 of the lower retaining area 201; accurately measuring and marking the anchor cable hole position, elevation, and inclination angle; monitoring the hole position and inclination angle in real time during the anchor cable drilling process; the lateral spacing of the prestressed anchor cables 4 is 2-4m, the vertical spacing is 2-3m, and the anchor cable inclination angle θ is 15-30°; the prestressed anchor cables 4 are divided into a free section and an anchored section, the length of the free section is ≥ 5m, and the length of the anchored section is ≥ 5m. The foundation is constructed from stable moderately weathered / slightly weathered rock. The anchor hole positioning deviation of the prestressed anchor cable 4 is no more than 20mm from the design, the borehole inclination deviation is no more than 2%, and the borehole depth exceeds the designed anchor length by no less than 0.5m. Grouting is performed using the bottom-mounted grouting method, with grouting pressure controlled at 0.6–1.0 MPa. Before the initial setting of the atmospheric pressure grout, a secondary grouting is performed using a high-pressure grouting pump at a pressure of 2.0–4.0 MPa. After constructing the reinforced concrete anchor pier, prestressing tensioning and locking are carried out. Prestressing tensioning is performed in two stages. After the anchor cable is tensioned to the design value, the anchor head is sealed using C30 non-shrink fine aggregate concrete. Prestressed anchor cable reinforcement increases the structure's horizontal anti-slip force and vertical friction force.

[0073] S6. Foundation Construction: The contact surface between the retained area 201 at the bottom of the vertical retaining structure and the foundation 6 is roughened to form a roughened surface with a depth of 5cm and a spacing of 10cm. Loose soil and construction debris are removed. Rebar holes 503 are drilled on the roughened surface, ensuring the hole walls are intact without cracks or honeycomb. Threaded steel bars with a diameter of 25-32mm are inserted at a spacing of 0.2-0.5m and an insertion depth ≥0.5m. The surface is then filled with anchoring adhesive, ensuring the adhesive adheres evenly to the steel bar surface without air bubbles. After impregnating the contact surface between the new and old structures, an interface agent is applied, followed by the pouring of the foundation concrete. The anchoring adhesive should have a bond shear strength ≥11MPa and a compressive strength ≥50MPa. The anchoring adhesive should be water-resistant, acid and alkali-resistant, and freeze-thaw resistant.

[0074] S7. Construction of bridge abutment and roadbed backfilling; Construction of bridge abutment 7 and bearing 701, with crushed stone soil backfilled in layers and compacted to a compaction degree ≥96%.

[0075] S8. Construction of the bridge superstructure; the bridge approach slab 8 and the bridge deck box girder 9 are constructed in sequence to complete the overall bridge structure construction.

[0076] After demolishing the upper part of the vertical retaining structure, the existing riverbank revetment pile foundation and vertical retaining structure can be assessed for technical condition, bearing capacity, and durability to determine their compatibility and durability as a bridge reconstruction structure after reinforcement. Based on the test results, reinforcement treatment can be carried out in conjunction with the aforementioned reinforcement structure. The structural testing evaluates the bearing capacity and durability of the existing riverbank revetment structure; the testing includes technical condition assessment, bearing capacity, and durability testing. In the technical condition assessment, the foundation components to be used should be of grade ≥3, with a technical condition score ≥60 points, and free from fatal defects such as main reinforcement corrosion loss >10%, through cracks in components, and foundation slippage.

[0077] In the load-bearing capacity test, the vertical compressive bearing capacity Ra of the existing bridge piles needs to be obtained through static load test. The residual deformation after unloading should be ≤20% of the measured deformation to ensure that the actual load-bearing capacity of the existing structure can meet the superstructure load requirements after the bridge is renovated.

[0078] Durability testing includes concrete carbonation depth and protective layer thickness. Pile integrity testing is classified as Class I or II. The durability level is ≥ Class C (medium or above). The remaining service life after structural modification is determined, and the service life requirements of the modified bridge structure must be met.

[0079] The above description is merely one embodiment of the present invention, and while it is detailed and specific, it should not be construed as limiting the scope of the invention. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of the present invention, and these modifications and improvements all fall within the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be determined by the appended claims.

Claims

1. A bridge renovation structure based on existing riverbank protection, mainly targeting the abutment area of ​​simple bridges in urban waterways, characterized by: The modified structure is based on the existing riverbank protection structure, which includes existing pile foundations (1) and vertical retaining structure (2). The modified structure includes a pier (6), abutment (7) and bank reinforcement structure. The pier (6) is constructed on the top surface of the lower retained area (201) of the vertical retaining structure after the upper area of ​​the vertical retaining structure (2) is removed. The bottom surface of the pier (6) is closely connected to the lower retained area (201) of the vertical retaining structure through a rebar reinforcement connection structure (5). The top surface of the pier (6) is not higher than the design water level line (3) of the river. The abutment (7) is located above the pier (6) and is used to erect the bridge deck box girder (9). The revetment reinforcement structure includes newly built reinforcing piles (10) and prestressed anchor cables (4) installed in the lower reserved area (201) of the vertical retaining structure. The prestressed anchor cables (4) are driven into the water from the water-facing surface of the lower reserved area (201) of the vertical retaining structure, and their anchoring sections extend into the bedrock layer of the revetment area. The newly built reinforcing piles (10) are located below the pile cap (6) and together with the existing piles (1), they support the pile cap (6).

2. The old bridge renovation structure based on existing riverbank protection as described in claim 1, characterized in that: The combined vertical bearing capacity R of the existing pile foundation (1) and the newly built reinforcing pile foundation (10) should be greater than the total vertical load F transmitted by the bridge superstructure; the specific formula is as follows: ； In the formula, This represents the sum of the vertical bearing capacities of all existing pile foundations. n 旧 Ra represents the total number of existing pile foundations, and Ra represents the vertical bearing capacity of a single existing pile foundation. This represents the sum of the vertical bearing capacities of all newly constructed and reinforced pile foundations. n 新 Rb represents the total number of newly constructed reinforcing piles, and Rb represents the vertical bearing capacity of a single newly constructed reinforcing pile. is the pile group effect coefficient, usually taken as 0.7 to 1.0; G is the permanent load; Q is the variable load; The permanent load G and the variable load Q are both taken in accordance with the requirements of the "General Specifications for Design of Highway Bridges and Culverts" or the "Specifications for Design of Urban Bridges".

3. A bridge renovation structure based on existing riverbank protection as described in claim 1 or 2, characterized in that: The modified structure is located in the abutment modification area at both ends of the bridge deck box girder (9). The modified structures at both ends are the same and are constructed based on the revetment structures on both sides of the river. The two ends of the bridge deck box girder (9) are respectively installed on the abutment (7) on the corresponding side through the support (701). Abutment approach plates (8) are provided at both ends of the bridge deck box girder (9).

4. A bridge renovation structure based on existing riverbank protection as described in claim 1 or 2, characterized in that: The newly built reinforced pile foundation (10) is evenly distributed with the existing pile foundation (1), and the pile spacing and pile length of the newly built reinforced pile foundation (10) are the same as those of the existing pile foundation (1); both the newly built reinforced pile foundation (10) and the existing pile foundation (1) are reinforced concrete cast-in-place piles, and the pile bottom is embedded in the bedrock layer to a depth ≥ 5 times the pile diameter.

5. A bridge renovation structure based on existing riverbank protection as described in claim 1 or 2, characterized in that: The lower retaining area (201) of the vertical support structure is reinforced with prestressed anchor cables (4) to achieve a sliding stability coefficient Kc≥1.3 and an overturning stability coefficient K0≥1.

5. The prestressed anchor cables (4) have a lateral spacing of 2-4m, a vertical spacing of 2-3m, and an anchor cable inclination angle θ of 15-30°. The prestressed anchor cables (4) are divided into a free section and an anchoring section. The length of the free section is ≥5m, and the anchoring section extends into the stable moderately weathered or slightly weathered rock base. The anchor hole positioning of the prestressed anchor cables (4) deviates from the design by no more than 20mm, the drilling inclination deviation is no more than 2%, and the drilling depth exceeds the anchor rod design length by no less than 0.5m.

6. A bridge renovation structure based on existing riverbank protection as described in claim 1 or 2, characterized in that: The top surface of the foundation (6) is flush with the design water level line (3) of the river channel. The rebar reinforcement connection structure (5) includes a roughened surface (501) for contact between the new and old structures and multiple rebars (502). After roughening the top surface of the area (201) at the bottom of the vertical support structure, multiple rebar holes (503) are opened. The lower part of the rebar (502) is inserted into the corresponding rebar hole (503), and the rebar hole (503) is filled with modified epoxy or modified vinyl ester structural rebar adhesive. The upper part of the multiple rebars (502) extends to the concrete pouring area of ​​the foundation (6) and is integrated with the foundation (6) when the concrete is poured.

7. A construction method for the renovation of an old bridge based on an existing riverbank revetment as described in any one of claims 1 to 6, characterized in that, The renovation of old bridges mainly targets the existing low-standard and simple bridges in urban waterways. The waterways have existing revetment structures on both sides, and the renovation project will be based on these existing revetment structures. The specific construction steps are as follows: S1. Demolition of the old bridge structure; demolition of the existing low-standard bridge deck structure, lightweight abutments, and original bridge piers in the river channel. S2. Determine the number of newly constructed reinforcement piles; obtain the vertical compressive bearing capacity Ra of the existing piles in the riverbank protection structure through static load tests, and determine the number of existing piles n. 旧 Then calculate the total vertical bearing capacity of all existing pile foundations. The minimum composite vertical bearing capacity R of the pile group is determined based on the total vertical load F transmitted by the bridge superstructure. The composite vertical bearing capacity R of the pile group satisfies: R≧F. The minimum total vertical bearing capacity of newly constructed reinforced pile foundations is calculated using the following formula. : ； This is the group pile effect coefficient, typically taken as 0.7 to 1.0; ， n 新 Rb represents the total number of newly constructed reinforcing piles, and Rb represents the vertical bearing capacity of a single newly constructed reinforcing pile. And based on the calculated total minimum vertical bearing capacity of the newly constructed reinforced pile foundation. The number of new reinforcement piles will be determined based on the site conditions. S3. Construction of new reinforced pile foundations; On the existing ground surface, the new reinforced pile foundations are measured and located according to the design requirements. The new reinforced pile foundations are constructed using bored cast-in-place pile technology to ensure that the depth of the pile bottom embedded in the bedrock layer is ≥ 5 times the pile diameter; The part above the design elevation of the pile top is treated as an empty pile. S4. Bank protection renovation and foundation pit excavation; The existing riverbank protection structure is divided into a retained area at the bottom of the vertical support structure and a demolition area at the top of the vertical support structure, with the design height of the bottom surface of the pier as the dividing line. The design height of the bottom surface of the pier is equal to the design water level of the river channel minus the thickness of the pier. The upper demolition area of ​​the vertical support structure is demolished to the design height of the bottom surface of the pier. Simultaneously, the upper backfill is excavated to the design elevation of the bottom surface of the pier. Based on the surrounding construction conditions and the excavation depth, the slope excavation or vertical excavation after retaining pile support is selected. S5. Reinforcement of the lower retaining area of ​​the vertical retaining structure; Prestressed anchor cables are installed on the water-facing sidewall of the lower retaining area of ​​the vertical retaining structure to ensure that the anti-slip stability coefficient Kc ≥ 1.3 and the anti-overturning stability coefficient K0 ≥ 1.5; The horizontal spacing of the prestressed anchor cables is 2-4m, the vertical spacing is 2-3m, and the anchor cable inclination angle θ is 15-30°; The prestressed anchor cables are divided into a free section and an anchoring section. The length of the free section is ≥ 5m, and the anchoring section extends into the stable moderately weathered or slightly weathered rock base. After the anchor cables are tensioned to the design value, the anchor head is sealed with fine stone concrete. S6. Foundation pouring construction: The contact surface between the lower part of the vertical retaining structure and the foundation is roughened, loose soil and construction debris are removed, rebar holes are drilled on the roughened surface and rebars are inserted, and rebar adhesive is filled in; after the contact surface between the new and old structures is moistened, an interface agent is applied, and foundation concrete is poured according to the design requirements. S7. Bridge abutment and roadbed backfilling construction; construct bridge abutments and bearings, and backfill the area behind the abutments with crushed stone soil in layers and compact it with a compaction degree ≥96%; S8. Construction of the bridge superstructure: The bridge approach slabs and bridge deck box girders are constructed in sequence to complete the overall bridge structure construction.

8. A construction method for renovating an old bridge based on existing riverbank protection structures according to claim 7, characterized in that: In step S2, the newly constructed reinforcing piles are evenly distributed with the existing piles, and the spacing and length of the newly constructed reinforcing piles are the same as those of the existing piles. Therefore, Rb = Ra; and the number of newly constructed reinforcing piles n is calculated according to the formula. 新 The minimum value; The total vertical load F transmitted by the bridge superstructure in step S2 is calculated according to the following formula: ； In the formula, G is the permanent load; Q is the variable load; The permanent load G and the variable load Q are both taken in accordance with the requirements of the "General Specifications for Design of Highway Bridges and Culverts" or the "Specifications for Design of Urban Bridges"; wherein, the permanent load includes the bridge's self-weight, prestress, and soil and water pressure; the variable load includes vehicle load, pedestrian load, temperature load, wind load, and seismic load.

9. A construction method for renovating an old bridge based on existing riverbank protection structures according to claim 7, characterized in that: In step S5, the anchor hole positioning deviation of the prestressed anchor cable shall not exceed 20mm, the drilling inclination deviation shall not exceed 2%, and the drilling depth shall exceed the design length of the anchor rod by not less than 0.5m. Grouting shall be carried out using the bottom-hole return grouting method, with the grouting pressure controlled at 0.6-1.0MPa. Before the initial setting of the normal pressure grouting, a high-pressure grouting pump shall be used to perform secondary grouting at a pressure of 2.0-4.0MPa. Subsequently, prestressing tensioning and locking shall be carried out. After the anchor cable is tensioned to the design value, the anchor head shall be sealed with C30 non-shrink fine aggregate concrete.

10. A construction method for the renovation of an old bridge based on an existing riverbank revetment, as described in claim 7, characterized in that: The reinforcing bars implanted in step S6 are HRB400 ribbed steel bars, with a spacing of 0.2 to 0.5 m, an implantation depth of ≥0.5 m, a shear strength of ≥11 MPa for the adhesive bond, and a compressive strength of ≥50 MPa.

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