A construction method for splicing joints between old and new roads

Abstract

This invention relates to a construction method for joints between new and old roads, comprising the following steps: S1, prefabrication of hollow slabs; S2, construction of rock-socketed piles; S3, revetment repair and retaining wall construction; S4, cap beam construction; S5, beam and slab hoisting; S6, construction of retaining beams and cantilever slabs; S7, construction of sleeper beams and roadbed plates; S8, external corrosion protection of concrete. It features convenient construction, structural strength meeting actual design and usage requirements, uniform stress distribution, high integrity, and effectively reduces the destructive impact of uneven settlement.

Description

Technical Field

[0001] This invention relates to the field of road construction technology, and in particular to a construction method for splicing joints between new and old roads. Background Technology

[0002] The conventional approach to widening and renovating old coastal roads involves splicing existing roads with reclaimed land. However, with changes in national land reclamation policies, this method has become increasingly undesirable due to its detrimental effects on ecological development and the marine environment. Furthermore, these old roads no longer meet the needs of current traffic flow, the surrounding environment, and economic development. Traditional highway bridge designs fail to consider the corrosive effects of seawater on steel reinforcement, wave erosion, typhoons, surges, uneven settlement after splicing with the existing road, and the earth pressure exerted on the bridge by the old road revetment. This invention is based on the aforementioned research background and aims to provide a construction method for splicing joints between old and new roads to meet practical needs.

[0003] Based on the project's service life, traffic capacity, and geological environment, traditional prestressed slab bridges can meet the requirements, and the span can be increased to 20 meters per span, reducing project costs and time. To achieve a balance, traditional highway bridges are being developed using existing construction techniques, innovating and boldly experimenting. Conventional wharf and hydraulic engineering design features are being integrated into the highway design, combining cross-disciplinary and cross-industry approaches. Widening is being achieved using a "trestle"-like structure, which both meets social traffic needs and protects the marine ecosystem. Summary of the Invention

[0004] In view of the above-mentioned defects in the existing technology, the purpose of the present invention is to provide a construction method for splicing joints between new and old roads, which has the characteristics of convenient construction, structural strength that can meet the actual design and use needs, uniform stress, high integrity, and effectively reducing the destructive impact of uneven settlement.

[0005] To achieve the above objectives, the present invention employs the following technical solution:

[0006] A construction method for splicing joints between old and new roads is disclosed. This method utilizes coastal embedded rock pile foundations in conjunction with cap beams, slab beams, and roadbed plates designed for wharves and hydraulic engineering. While repairing the old revetment, a rubble concrete retaining wall is added. The retaining wall capping adopts an L-shaped design, fully fitting the retaining beam section, and is equipped with a rubber waterstop. The surface pavement layer is a two-layer design: a lower layer of conventional plain concrete and an upper layer of reinforced concrete panel, forming an integral whole with the old road base. A sleeper beam is installed at the edge of the old roadbed's driving lane to integrate the old road with the new bridge, ensuring uniform stress distribution and reducing damage caused by uneven settlement. The method includes the following steps: S1, hollow slab prefabrication; S2, embedded rock pile construction; S3, revetment repair and retaining wall construction; S4, cap beam construction; S5, slab beam hoisting; S6, retaining beam and cantilever slab construction; S7, sleeper beam and roadbed plate construction; S8, external concrete corrosion protection.

[0007] As a further optimization of the above scheme, the specific process of hollow slab prefabrication in step S1 includes:

[0008] The precast pedestals for hollow slabs are constructed using C20 reinforced concrete, 10-20cm thick, and feature an inverted arch as per design requirements. After the concrete reaches a certain strength, a 10mm steel plate is placed over the pedestal surface. The steel plate is then fixed to the pedestal concrete by drilling holes and injecting epoxy resin. Before precast slab construction, the concrete mix design and various material tests are conducted and approved by the engineer. Based on the actual conditions, a comprehensive comparison is made to determine the pouring sequence for the precast slab concrete. During construction, a horizontal layered and longitudinally segmented continuous pouring process is adopted, with each layer not exceeding 30cm in thickness. First, pour the base slab, then the web and top slab. Concrete is poured using a centralized mixing plant, transported by concrete mixer trucks, and pumped by concrete delivery pumps. A combined vibration process using attached vibrators mounted on side formwork and immersion vibrators is employed. For the lower part of the web, attached vibrators are used in conjunction with immersion vibrators; for the upper and middle parts of the web, immersion vibrators are used; and for the top slab, immersion vibrators are used. Each vibration point must be vibrated until the concrete in that area is compacted. After the slab concrete pouring is complete, cover it with burlap sacks for protection, avoiding direct sunlight and exposure to the atmosphere. Direct contact should be made, and water curing should be carried out for 7-14 days; the steel bars inside the hollow slab should be tensioned, and the steel strands should be tensioned when the concrete strength reaches more than 90% of the design strength; grouting should be carried out as soon as possible after tensioning, and debris and water should be removed from the ducts before grouting; after the steel strands are tensioned, the steel strands outside the anchorage should be cut off with a grinding wheel, and then sealed with epoxy mortar to prevent water leakage; vacuum grouting should be carried out with silicate cement grout, and the strength, consistency, water-cement ratio, bleeding rate, and expansion agent dosage of the grout should be controlled according to the requirements of the construction technical specifications and test standards; the grouting sequence should be as follows. The grouting process should proceed from bottom to top, with strict control of the water-cement ratio during grouting. Each duct should be grouted in one continuous operation without interruption to ensure a dense and reliable grout. Grouting should begin at one end of each duct, with the grout injected through the grouting port until the grout sprayed from the outlet at the other end meets the specifications. Pressure should then be maintained for 3 to 5 minutes before closing the valve to complete the grouting. After grouting, the grouting valve can only be removed after the cement grout has initially set. The reinforcing bars at the bottom of the hollow slab beam should be coated with cement mortar containing a rust inhibitor. The precast slabs can only be lifted and moved after the specimen strength meets the specifications following grouting.

[0009] As a further optimization of the above scheme, the specific process of rock-socketed pile construction in step S2 includes:

[0010] ① Steel platform construction

[0011] According to geological survey data, the construction site is located by the sea and is affected by tides daily. Since there is no pile cap, a steel platform combined with impact bored piles will be used for construction. The main support system of the cast-in-place pile platform uses φ114×3.5mm steel pipe piles, arranged in a grid pattern with a longitudinal and transverse spacing of 1500-2000mm. The longitudinal and transverse bracing uses 8# channel steel for connection. A continuous scissor brace is installed longitudinally, and a diagonal brace is installed every four rows transversely in a crisscross pattern. On the seaward side, each row uses 8# channel steel for diagonal bracing, with the base inserted 200mm into the rock layer or supported by existing rock grooves, and encased with 500*500*500mm concrete. The top surface of the steel pipes is welded with 16# channel steel and corbels, serving as the main load-bearing beams. 6mm steel plates are laid throughout the construction area and pedestrian walkways.

[0012] ② Pile foundation construction

[0013] Because rock-socketed piles are used, the embedment depth into the moderately weathered layer must be ≥2D, and the pile length must be >9 meters, where D is the design diameter of the enlarged end of the rock-socketed pile. To ensure construction quality and improve construction efficiency, the following construction methods are adopted:

[0014] Due to construction on the steel platform, 8-10mm thick steel casings were used, with the casings fully embedded in the rock. The top surface of the casing was more than 1 meter above the highest tide level to avoid the impact of waves. Because pile driving was carried out on the tidal flats, the coastal rock strata varied greatly and were quite sloping. To ensure the verticality of the pile body, the verticality of the crosshairs of the pile hole was checked every 1 meter of drilling, and the impact drill bit teeth were observed. Significant wear was promptly repaired to prevent borehole deviation. Rock samples were taken three times daily and preserved. These samples were then analyzed in conjunction with the supervisor and geological surveyor to determine the embedment depth. A double-cleaning method using a slag-removing cylinder combined with mud circulation was employed for cleaning the pile foundation holes. Because the pile foundations used fully embedded steel casings, shrinkage-compensating concrete was used to ensure a tight bond with the steel casing.

[0015] As a further optimization of the above scheme, the specific process of revetment repair and retaining wall construction in step S3 includes:

[0016] The old revetment was built with dry-laid rubble masonry. Its demolition and repair posed a huge hazard to the existing road. During the actual construction, a combination of segmented demolition and temporary rigid support was adopted. The demolished part was promptly used for the construction of a new reinforced concrete retaining wall. The new retaining wall was made of rubble masonry concrete and used a combination of steel formwork and internal steel support. The wall was constructed in segments, with each layer not exceeding 1.5 meters in height. When the wall strength reached 75%, the backfill was carried out in a timely manner.

[0017] As a further optimization of the above scheme, the specific process of constructing the cap beam in step S4 includes:

[0018] The cap beam adopts a U-shaped design, requiring the precast slab reinforcement and the cap beam reinforcement to form an integral whole to resist surge forces. During the construction of the cap beam, it is poured in sections. The lower cap beam part is poured first. After the beam slab is hoisted and the beam slab hinge joint is poured, the retaining beam and the bridge deck pavement cantilever slab reinforcement are tied and then poured together to ensure that they share the load and avoid different stress distributions.

[0019] As a further optimization of the above scheme, the specific process of beam and slab hoisting construction in step S5 includes:

[0020] Based on the beam length and weight, and combined with the on-site hoisting position and angle, the beams were hoisted. The beam hoisting was carried out using a combination of two 50T self-propelled cranes and two beam transport vehicles.

[0021] As a further optimization of the above scheme, the specific process for constructing the retaining beam and cantilever slab in step S6 includes:

[0022] ① Retaining beam construction

[0023] The cast-in-place surface layer reinforcement is anchored into the retaining beam, and the retaining beam reinforcement is anchored into the cap beam. The cast-in-place surface layer, retaining beam, and cap beam concrete are poured simultaneously to form an integral structure. The retaining beam is set at both ends of the precast hollow slab, which serves to protect the precast beam slab and also plays a role in adjusting the bridge alignment. Rubber waterstops are used to seal between the bridge deck and the newly built capping, and a cement crushed stone cushion layer and asphalt concrete pavement are laid on top.

[0024] ②Cantilever slab

[0025] An expansion joint is set in the middle of the cantilever slab. Support scaffolding is fully installed under the cantilever slab, and 80mm special-shaped steel expansion devices are pre-embedded before concrete pouring. The pre-embedded bars of the expansion devices are embedded along the bridge direction. During installation, the pre-embedded bars are welded to the anchor bars of the expansion devices, and the length of the single-sided weld is not less than 14cm. The depth of the expansion device groove must reach the solid concrete surface of the beam slab or back wall. The reserved groove is filled with CF50 steel fiber concrete, in which the steel fiber volume ratio is 0.8% and compacted. A layer of φ8 cold-rolled ribbed steel mesh is added to the top surface, with a net protective layer of 2cm for the steel bars. The end of the special-shaped steel expansion device extends 2cm beyond the outside of the crash barrier.

[0026] As a further optimization of the above scheme, the specific process for constructing the sleeper beam and roadbed plate in step S7 includes:

[0027] After all pipelines, roadbed, and subbase construction of the road section are completed, the construction of the roadbed slab and sleeper beams will begin. The roadbed slab is required to be 6 meters per block, and the reinforcing steel should be φ16 steel bars laid in a double layer and in both directions to ensure good overall stress. During construction, the steel bars should be spliced ​​as much as possible to avoid increasing the shear resistance.

[0028] As a further optimization of the above scheme, the specific process of concrete external corrosion protection construction in S8 includes:

[0029] Before construction, the concrete surface is treated. Honeycomb and other defects are repaired with cement mortar of the same mix ratio. The surface is cleaned of any non-adherent substances with a steel trowel. On-site construction is carried out by roller coating. To ensure uniform thickness, the roller is applied in the same direction. During construction, the paint film thickness is checked with a thickness gauge to control the thickness and ensure uniformity.

[0030] The construction method for splicing joints between old and new roads according to the present invention has the following beneficial effects:

[0031] 1. The core of the construction method adopted in this application is the coastal embedded rock pile foundation combined with the wharf, the cap beam and beam slab of the hydraulic design, plus the unique roadbed base plate, which provides a guarantee for the splicing construction of the semi-road slab bridge. The existing roadside is an old revetment. In order to ensure the splicing line shape and the strength of the splicing joint, a rubble concrete retaining wall is added while repairing the old revetment. The retaining wall cap is set in an L shape, which is completely attached to the retaining beam and a rubber waterstop is installed. The surface pavement layer is a two-layer design. The lower layer is conventional plain concrete and the upper layer is reinforced concrete panel, which forms an integral whole with the old road base. A sleeper beam is installed under the edge of the old roadbed carriageway to make the old road and the new bridge form an integral whole, so as to evenly distribute the stress and reduce the damage caused by uneven settlement.

[0032] 2. The construction method adopted in this application requires thorough research during the design and construction process. Based on local hydrological data, geological survey data, climate conditions, and factors such as the chloride ion content of the sea area, traffic load, and social environment, the advantages of combining hydraulic engineering, wharf, and highway bridges are utilized in the design and construction of the semi-slab bridge splicing. In the design and construction, the advantages of wharf short-span beams and rigid abutments for wave resistance and bridge deck protection are integrated into the semi-slab bridge splicing design and construction. The advantages of marine concrete and chloride ion-resistant external corrosion protection commonly used in hydraulic engineering are also incorporated into the semi-slab bridge splicing design and construction, improving structural durability. Furthermore, the roadbed design involves constructing a new longitudinal sleeper beam on the old road and adding a layer of reinforced concrete slab across the entire splicing section, effectively controlling the damage to the road surface caused by uneven settlement between the new spliced ​​bridge and the old road. In addition, the bridge design uses fully enclosed rock-embedded piles, effectively controlling pile quality, pile load-bearing capacity, and bridge settlement. Attached Figure Description

[0033] Appendix Figure 1 This is a schematic diagram of the cap beam section in the construction method for the splicing joint of old and new roads in this invention.

[0034] Appendix Figure 2 This is a construction drawing of the retaining beam in the construction method for the splicing joint of old and new roads in this invention.

[0035] Appendix Figure 3 This is a diagram showing the layout of pre-embedded reinforcing bars during the construction of cantilever slabs in the new and old road splice joint construction method of this invention.

[0036] Appendix Figure 4 This is a detailed drawing of the installation of the expansion joint device during the construction of the cantilever slab in the new and old road splice joint construction method of the present invention.

[0037] Appendix Figure 5 This is a schematic diagram of the road surface before modification in the construction method of the splicing joint of the old and new roads in this invention.

[0038] Appendix Figure 6 This is a schematic diagram of the modified road surface in the construction method for the splicing joint of old and new roads in this invention. Detailed Implementation

[0039] The following is in conjunction with the appendix Figure 1-6 This invention provides a detailed description of a construction method for splicing joints between old and new roads.

[0040] A construction method for splicing joints between old and new roads is disclosed. This method utilizes coastal embedded rock pile foundations in conjunction with cap beams, slab beams, and roadbed plates designed for wharves and hydraulic engineering. While repairing the old revetment, a rubble concrete retaining wall is added. The retaining wall capping adopts an L-shaped design, fully fitting the retaining beam section, and is equipped with a rubber waterstop. The surface pavement layer is a two-layer design: a lower layer of conventional plain concrete and an upper layer of reinforced concrete panel, forming an integral whole with the old road base. A sleeper beam is installed at the edge of the old roadbed's driving lane to integrate the old road with the new bridge, ensuring uniform stress distribution and reducing damage caused by uneven settlement. The method includes the following steps: S1, hollow slab prefabrication; S2, embedded rock pile construction; S3, revetment repair and retaining wall construction; S4, cap beam construction; S5, slab beam hoisting; S6, retaining beam and cantilever slab construction; S7, sleeper beam and roadbed plate construction; S8, external concrete corrosion protection.

[0041] The specific process for hollow slab prefabrication in step S1 includes:

[0042] The precast pedestals for hollow slabs are constructed using C20 reinforced concrete, 10-20cm thick, and feature an inverted arch as per design requirements. After the concrete reaches a certain strength, a 10mm steel plate is placed over the pedestal surface. The steel plate is then fixed to the pedestal concrete by drilling holes and injecting epoxy resin. Before precast slab construction, the concrete mix design and various material tests are conducted and approved by the engineer. Based on the actual conditions, a comprehensive comparison is made to determine the pouring sequence for the precast slab concrete. During construction, a horizontal layered and longitudinally segmented continuous pouring process is adopted, with each layer not exceeding 30cm in thickness. First, pour the base slab, then the web and top slab. Concrete is poured using a centralized mixing plant, transported by concrete mixer trucks, and pumped by concrete delivery pumps. A combined vibration process using attached vibrators mounted on side formwork and immersion vibrators is employed. For the lower part of the web, attached vibrators are used in conjunction with immersion vibrators; for the upper and middle parts of the web, immersion vibrators are used; and for the top slab, immersion vibrators are used. Each vibration point must be vibrated until the concrete in that area is compacted. After the slab concrete pouring is complete, cover it with burlap sacks for protection, avoiding direct sunlight and exposure to the atmosphere. Direct contact should be made, and water curing should be carried out for 7-14 days; the steel bars inside the hollow slab should be tensioned, and the steel strands should be tensioned when the concrete strength reaches more than 90% of the design strength; grouting should be carried out as soon as possible after tensioning, and debris and water should be removed from the ducts before grouting; after the steel strands are tensioned, the steel strands outside the anchorage should be cut off with a grinding wheel, and then sealed with epoxy mortar to prevent water leakage; vacuum grouting should be carried out with silicate cement grout, and the strength, consistency, water-cement ratio, bleeding rate, and expansion agent dosage of the grout should be controlled according to the requirements of the construction technical specifications and test standards; the grouting sequence should be as follows. The grouting process should proceed from bottom to top, with strict control of the water-cement ratio during grouting. Each duct should be grouted in one continuous operation without interruption to ensure a dense and reliable grout. Grouting should begin at one end of each duct, with the grout injected through the grouting port until the grout sprayed from the outlet at the other end meets the specifications. Pressure should then be maintained for 3 to 5 minutes before closing the valve to complete the grouting. After grouting, the grouting valve can only be removed after the cement grout has initially set. The reinforcing bars at the bottom of the hollow slab beam should be coated with cement mortar containing a rust inhibitor. The precast slabs can only be lifted and moved after the specimen strength meets the specifications following grouting.

[0043] The specific process for constructing the rock-socketed piles in step S2 includes:

[0044] ① Steel platform construction

[0045] According to geological survey data, the construction site is located by the sea and is affected by tides daily. Since there is no pile cap, a steel platform combined with impact bored piles will be used for construction. The main support system of the cast-in-place pile platform uses φ114×3.5mm steel pipe piles, arranged in a grid pattern with a longitudinal and transverse spacing of 1500-2000mm. The longitudinal and transverse bracing uses 8# channel steel for connection. A continuous scissor brace is installed longitudinally, and a diagonal brace is installed every four rows transversely in a crisscross pattern. On the seaward side, each row uses 8# channel steel for diagonal bracing, with the base inserted 200mm into the rock layer or supported by existing rock grooves, and encased with 500*500*500mm concrete. The top surface of the steel pipes is welded with 16# channel steel and corbels, serving as the main load-bearing beams. 6mm steel plates are laid throughout the construction area and pedestrian walkways.

[0046] ② Pile foundation construction

[0047] Because rock-socketed piles are used, the embedment depth into the moderately weathered layer must be ≥2D, and the pile length must be >9 meters, where D is the design diameter of the enlarged end of the rock-socketed pile. To ensure construction quality and improve construction efficiency, the following construction methods are adopted:

[0048] Due to construction on the steel platform, 8-10mm thick steel casings were used, with the casings fully embedded in the rock. The top surface of the casing was more than 1 meter above the highest tide level to avoid the impact of waves. Because pile driving was carried out on the tidal flats, the coastal rock strata varied greatly and were quite sloping. To ensure the verticality of the pile body, the verticality of the crosshairs of the pile hole was checked every 1 meter of drilling, and the impact drill bit teeth were observed. Significant wear was promptly repaired to prevent borehole deviation. Rock samples were taken three times daily and preserved. These samples were then analyzed in conjunction with the supervisor and geological surveyor to determine the embedment depth. A double-cleaning method using a slag-removing cylinder combined with mud circulation was employed for cleaning the pile foundation holes. Because the pile foundations used fully embedded steel casings, shrinkage-compensating concrete was used to ensure a tight bond with the steel casing.

[0049] The specific process for revetment repair and retaining wall construction in step S3 includes:

[0050] The old revetment was built with dry-laid rubble masonry. Its demolition and repair posed a huge hazard to the existing road. During the actual construction, a combination of segmented demolition and temporary rigid support was adopted. The demolished part was promptly used for the construction of a new reinforced concrete retaining wall. The new retaining wall was made of rubble masonry concrete and used a combination of steel formwork and internal steel support. The wall was constructed in segments, with each layer not exceeding 1.5 meters in height. When the wall strength reached 75%, the backfill was carried out in a timely manner.

[0051] The specific process for constructing the cap beam in step S4 includes:

[0052] The cap beam adopts a U-shaped design, requiring the precast slab reinforcement and the cap beam reinforcement to form an integral whole to resist surge forces. During the construction of the cap beam, it is poured in sections. The lower cap beam part is poured first. After the beam slab is hoisted and the beam slab hinge joint is poured, the retaining beam and the bridge deck pavement cantilever slab reinforcement are tied and then poured together to ensure that they share the load and avoid different stress distributions.

[0053] The specific process for beam and slab hoisting in step S5 includes:

[0054] Based on the beam length and weight, and combined with the on-site hoisting position and angle, the beams were hoisted. The beam hoisting was carried out using a combination of two 50T self-propelled cranes and two beam transport vehicles.

[0055] The specific process for constructing the retaining beam and cantilever slab in step S6 includes:

[0056] ① Retaining beam construction

[0057] The cast-in-place surface layer reinforcement is anchored into the retaining beam, and the retaining beam reinforcement is anchored into the cap beam. The cast-in-place surface layer, retaining beam, and cap beam concrete are poured simultaneously to form an integral structure. The retaining beam is set at both ends of the precast hollow slab, which serves to protect the precast beam slab and also plays a role in adjusting the bridge alignment. Rubber waterstops are used to seal between the bridge deck and the newly built capping, and a cement crushed stone cushion layer and asphalt concrete pavement are laid on top.

[0058] ②Cantilever slab

[0059] An expansion joint is set in the middle of the cantilever slab. Support scaffolding is fully installed under the cantilever slab, and 80mm special-shaped steel expansion devices are pre-embedded before concrete pouring. The pre-embedded bars of the expansion devices are embedded along the bridge direction. During installation, the pre-embedded bars are welded to the anchor bars of the expansion devices, and the length of the single-sided weld is not less than 14cm. The depth of the expansion device groove must reach the solid concrete surface of the beam slab or back wall. The reserved groove is filled with CF50 steel fiber concrete, in which the steel fiber volume ratio is 0.8% and compacted. A layer of φ8 cold-rolled ribbed steel mesh is added to the top surface, with a net protective layer of 2cm for the steel bars. The end of the special-shaped steel expansion device extends 2cm beyond the outside of the crash barrier.

[0060] The specific process for constructing the sleeper beam and roadbed plate in step S7 includes:

[0061] After all pipelines, roadbed, and subbase construction of the road section are completed, the construction of the roadbed slab and sleeper beams will begin. The roadbed slab is required to be 6 meters per block, and the reinforcing steel should be φ16 steel bars laid in a double layer and in both directions to ensure good overall stress. During construction, the steel bars should be spliced ​​as much as possible to avoid increasing the shear resistance.

[0062] The specific process for concrete external corrosion protection construction in S8 includes:

[0063] Before construction, the concrete surface is treated. Honeycomb and other defects are repaired with cement mortar of the same mix ratio. The surface is cleaned of any non-adherent substances with a steel trowel. On-site construction is carried out by roller coating. To ensure uniform thickness, the roller is applied in the same direction. During construction, the paint film thickness is checked with a thickness gauge to control the thickness and ensure uniformity.

[0064] The above description is merely a preferred embodiment of the present invention. The present invention is not limited to the above-described embodiments. Any modifications, equivalent substitutions, or improvements made within the spirit and principles of this disclosure, as long as they achieve the same technical effects, should be included within the scope of protection of this disclosure and fall under the protection scope of the present invention. Within the protection scope of the present invention, the technical solutions and / or implementation methods can have various modifications and variations.

Claims

1. A method for constructing a new-old road splice joint, characterized by: This construction method utilizes coastal embedded rock pile foundations in conjunction with the wharf, hydraulic engineering design of cap beams, slab beams, and roadbed slabs. While repairing the old revetment, a rubble concrete retaining wall is added. The retaining wall's coping is L-shaped, fully integrated with the retaining beam, and fitted with a rubber waterstop. The surface pavement has a two-layer design: a lower layer of conventional plain concrete and an upper layer of reinforced concrete slab, forming a unified structure with the old roadbed. Sleeper beams are installed at the edge of the old roadbed's driveway to ensure the original old road and the new bridge are integrated, resulting in even stress distribution and reduced stress. The damage caused by uneven settlement is mitigated by constructing a new longitudinal continuous sleeper beam on the old road and adding a layer of reinforced concrete slab across the entire cross-section of the spliced ​​section. This effectively controls the damage to the road surface caused by uneven settlement between the newly constructed spliced ​​bridge and the old road. The method includes the following steps: S1, prefabrication of hollow slabs; S2, construction of rock-socketed piles; S3, revetment repair and retaining wall construction; S4, cap beam construction; S5, beam and slab hoisting; S6, construction of retaining beams and cantilever slabs; S7, sleeper beam and roadbed plate construction; S8, external anti-corrosion treatment of concrete. The specific process of step S2 includes: ① Steel platform construction According to geological survey data, the construction site is located by the sea and is affected by tides daily. Since there is no pile cap, a steel platform combined with impact bored piles will be used for construction. The main support system of the cast-in-place pile platform uses φ114×3.5mm steel pipe piles, arranged in a grid pattern with a longitudinal and transverse spacing of 1500-2000mm. The longitudinal and transverse bracing uses 8# channel steel for connection. A continuous scissor brace is installed longitudinally, and a diagonal brace is installed every four rows transversely in a crisscross pattern. On the seaward side, each row uses 8# channel steel for diagonal bracing, with the base inserted 200mm into the rock layer or supported by existing rock grooves, and encased with 500*500*500mm concrete. The top surface of the steel pipes is welded with 16# channel steel and corbels, serving as the main load-bearing beams. 6mm steel plates are laid throughout the construction area and pedestrian walkways. ② Pile foundation construction Because rock-socketed piles are used, the embedment depth into the moderately weathered layer must be ≥2D, and the pile length must be >9 meters, where D is the design diameter of the enlarged end of the rock-socketed pile. To ensure construction quality and improve construction efficiency, the following construction methods are adopted: Due to construction on a steel platform, 8-10mm thick steel casings were used, with the casings fully embedded in the rock. The top surface of the casing was more than 1 meter above the highest tide level to avoid the impact of waves. Because pile driving was carried out on tidal flats, the coastal rock strata varied greatly and were quite sloping. To ensure the verticality of the piles, the verticality of the crosshairs of the pile hole was checked every 1 meter of drilling, and the impact drill bit teeth were observed. Significant wear was promptly repaired to prevent deviation from the target hole. Rock samples were taken three times daily and preserved. These samples were then analyzed in conjunction with the supervisor and geological surveyor to determine the embedment depth. A double-cleaning method using a slag-removing cylinder combined with mud circulation was employed for cleaning the pile foundation holes. Because the pile foundations used fully embedded steel casings, shrinkage-compensating concrete was used to ensure a tight bond with the steel casing. The specific procedure of the step S3 comprises: the old bulkhead is built by dry masonry, and there is a great hidden danger to the existing road during the demolition and modification, in the actual construction, the segmented demolition combined with the temporary rigid support is adopted, the new retaining wall reinforced concrete is constructed in time after the demolition, the new retaining wall is built by the combination of the steel formwork and the internal steel support, the wall is constructed in sections, the height of each layer is not more than 1.5 meters, and the wall body strength reaches 75% in time, and the back filling of the wall body is carried out in time; The specific procedure of the step S4 comprises: the bent cap is designed in the shape of Chinese character "K", the prefabricated plate steel and the bent cap steel are required to form an integral whole to resist the surge force, during the construction of the bent cap, the segmented pouring is adopted, the lower bent cap part is poured first, the beam and slab are hoisted and completed, the hinged joint of the beam and slab is poured and completed, and the steel binding of the retaining beam and the cantilevered slab of the bridge deck is completed, and then the pouring is carried out together to guarantee the common stress and avoid the different stress distribution; The specific procedure of the beam and slab hoisting construction in the step S5 comprises: According to the length and weight of the beam and slab, the hoisting position and angle of the beam and slab are combined to hoist the beam and slab, wherein the beam and slab hoisting is combined by two 50T self-propelled cranes and two beam transport vehicles; The specific procedure of the retaining beam and cantilevered slab construction in the step S6 comprises: ① Retaining beam construction The surface layer steel of the cast-in-place is anchored into the retaining beam, the retaining beam steel is anchored into the bent cap, the cast-in-place surface layer, the retaining beam and the bent cap concrete are poured at the same time to form an integral structure; the retaining beam is arranged at the two ends of the prefabricated hollow slab to protect the prefabricated beam plate and also bear the function of adjusting the bridge line type; the rubber waterstop is used between the bridge deck and the newly built coping to seal, and the cement macadam cushion and the asphalt concrete pavement are arranged on the upper part; ② Cantilevered slab The expansion joint is arranged in the middle of the cantilevered slab, the support scaffold is arranged under the cantilevered slab, and the 80-shaped steel expansion device is pre-buried, and then the concrete is poured; the expansion device pre-buried steel is pre-buried in the bridge direction, the pre-buried steel is welded with the expansion device anchor steel during the installation, the single-sided weld length is not less than 14cm, the depth of the expansion device slot must reach the beam plate or the solid concrete surface of the back wall, the CF50 steel fiber concrete is filled and tamped in the reserved slot, a layer of φ8 cold-rolled ribbed steel mesh is arranged on the top surface, the steel net protection layer is 2cm, and the end of the shaped steel expansion device is extended out of the outer side of the crash barrier by 2cm.

2. The method for constructing a joint between a new road and an old road according to claim 1, characterized in that: The specific procedure of the hollow slab prefabrication in the step S1 comprises: The pedestal of the hollow slab is prefabricated with C20 reinforced concrete structure, thickness of 10-20 cm, and is provided with reverse arch according to design requirements. After the concrete reaches a certain strength, 10 mm steel plate is covered on the surface of the pedestal, and the steel plate is fixed by punching and grouting epoxy resin with the concrete of the pedestal. Before the prefabricated slab construction, the mix proportion design of the concrete and various material tests are performed and approved by the engineer, and the pouring sequence of the prefabricated slab concrete is determined by comprehensive comparison according to the actual situation. In the construction, the horizontal layered and longitudinal segmented continuous pouring process is adopted, the layer thickness is not greater than 30 cm, the bottom plate is poured first, then the web plate and the top plate are poured. The concrete is poured by using centralized mixing of the mixing station, transportation of the concrete tank truck and pumping of the concrete delivery pump. The lower part of the web plate concrete is vibrated by using the attached vibrator installed on the side mold, combined with the inserted vibrator, the middle and upper parts of the web plate are vibrated by using the inserted vibrator, and the top plate concrete is vibrated by using the inserted vibrator. For each vibration position, the concrete must be vibrated until the concrete at the position is compacted. After the pouring of the slab body concrete is completed, the concrete is protected by laying the burlap bag to avoid direct contact with sunlight and atmosphere, and is maintained by watering for 7-14 days. The steel reinforcement in the hollow slab is tensioned, and the steel strand tensioning is performed when the concrete strength reaches more than 90% of the design strength. After the tensioning is completed, the grouting is performed as soon as possible, and the hole and accumulated water are removed before the grouting. After the steel strand tensioning is completed, the steel strand outside the anchor is cut off by using the grinder, and then is closed by using the epoxy mortar to prevent water leakage. The vacuum grouting is performed by using the Portland cement slurry, and the strength, consistency, water-cement ratio, bleeding rate and expansion agent content of the mortar are controlled according to the requirements in the construction technical specification and test standard. The grouting sequence is from bottom to top, and the water-cement ratio is strictly controlled during the grouting. Each hole is grouted once, and cannot be interrupted to ensure compactness and reliability. Each bundle of holes starts grouting from one end of the grouting hole, and the mortar is grouted from the grouting port until the mortar sprayed from the other end of the grouting port meets the specification requirements, and then the pressure is maintained for 3-5 minutes, and then the valve is closed to end the grouting. After the grouting is completed, the grouting valve can be removed after the cement mortar is initially set. The reserved steel reinforcement at the bottom of the hollow slab beam is coated with cement mortar with rust inhibitor.

3. The method of claim 2, wherein: The specific process of the construction of the sleeper beam and the roadbed plate in the step S7 includes: After the construction of all pipelines, roadbeds and cushion layers of the road part is completed, the construction of the roadbed plate and the sleeper beam is started. The roadbed plate is required to be 6 meters per block, and the steel reinforcement is required to be double-layer and double-directional to ensure good overall stress. The steel reinforcement should be avoided to be lapped as much as possible to avoid improving the shear performance.

4. The method of claim 3, wherein: The specific process of the concrete external corrosion prevention construction in the S8 includes: Before the construction, the surface of the concrete is treated, the honeycomb is repaired with the same proportion cement mortar, and the surface non-adhesion is cleaned with a sharp knife. The on-site construction is performed by using the rolling method. In order to ensure the uniform thickness, the rolling construction is performed in the same direction. During the construction, the paint film thickness is checked by using the thickness gauge to control the thickness and ensure the uniformity.

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