Integrated reverse construction process for deep cutting cast-in-place overbridge piles

Abstract

The invention discloses a deep cutting cast-in-place overbridge pile integrated reverse construction process, which adopts a process of firstly constructing, then excavating and integrating, and comprises the following specific steps: step 1, leveling and positioning the original ground; 2, pile and column integrated segmented pouring is carried out; 3, a low-position support is erected; 4, constructing an upper structure; 5, reverse earthwork excavation and form removal are carried out; and step 6, protection and monitoring. The construction method has the following advantages that firstly, excavation is conducted after construction is conducted, original 20-30 m high support construction is converted into low support operation, and the overall stability and construction safety of the support are greatly improved; 2, parallel operation of bridge substructure construction and large-scale earthwork excavation of the roadbed is realized, and absolute limitation of the excavation progress of the roadbed is avoided; and 3, the lease and transportation costs of pipe fittings, fasteners and reinforcing materials required by the ultrahigh bracket are obviously reduced. And 4, temporary site leveling and large-scale sloping for erecting a high bracket are reduced, and the stability of the undisturbed geology is protected.

Description

Technical Field

[0001] This invention relates to the field of bridge construction, specifically to a reverse construction process for an integrated pile and column structure for cast-in-place overpasses in deep road cuts. Background Technology

[0002] Existing bridge construction generally follows the sequence of "first excavating the roadbed, then constructing the substructure pile foundations and piers, and finally erecting the scaffolding to construct the superstructure".

[0003] Current technology has shortcomings: In deep road cut terrain, if this logic is followed, the construction scaffolding must be erected from the lower road surface after excavation, which causes the height of the scaffolding to increase sharply with the excavation depth, significantly increasing the input of turnover materials and the risk of collapse.

[0004] Reasons for the shortcomings: The construction sequence did not match the terrain characteristics, and the original earth and rock were not used as a construction support platform. Summary of the Invention

[0005] Therefore, to address the aforementioned shortcomings, this invention provides a reverse construction process for integrated pile and column construction of cast-in-place overpasses in deep road cuts. The technical problems to be solved are: 1. Risk of excessively high scaffolding: Traditional methods typically involve excavating the earthwork to the road surface elevation before constructing the bridge substructure. For high-pier overpasses, this results in excessively high scaffolding height after excavation, making stability control extremely difficult. 2. Lengthy construction period: Conventional procedures require waiting for large-scale earthwork excavation in the road cut before bridge construction can begin, causing the substructure and roadbed engineering to be out of sync. 3. Potential slope stability risks: Excavating before construction results in long-term slope exposure, and the overlapping of high-pier construction and roadbed excavation poses significant safety hazards.

[0006] This invention is implemented by constructing a reverse construction process for integrated pile and column construction of a cast-in-place overpass in deep road cuts. The key feature of this process is that it adopts a "construction first, excavation later, integrated" approach, with the specific steps as follows: Step 1, Leveling and positioning of the original ground: Before large-scale excavation of earth and rock, the original terrain is used as a construction platform; Step 2: Integrated segmented casting of piles and columns: Drilling process: Utilizing the original ground height, drilling is carried out along the same centerline according to the design requirements for pile diameter and pier diameter; Template installation: The pier template is pre-assembled on the ground and hoisted into the hole as a whole. Triangular limit clips are required at the junction of the pier and the pile foundation, and small steel (channel 20) is set at the lower end of the pier as temporary support. After the verticality is adjusted, sand is poured on the outside of the pier template to fix the template and prevent it from being affected during the excavation process. Post-casting embedded tie beam: Since the tie beam can only be constructed using the post-casting method, it is necessary to pre-embed the sleeve during the reinforcement construction. The sleeve is a Class I sleeve, and the pre-embedding is carried out according to the design reinforcement position.

[0007] Reinforcing cage extension: The bottom of the pile is cleaned with bricks using a rotary drilling machine. After cleaning, the reinforcing bars are installed. The reinforcing bars are processed in sections, and the processing method is the same as that for other pile foundations. Integrated casting: Concrete construction is carried out using the tremie pipe method; Step 3, Low-level scaffolding erection: After the substructure construction is completed, the box girder construction scaffolding is erected directly on the original ground (or a platform after shallow slope cutting). At this time, the scaffolding height is only the height from the bottom of the box girder to the original ground, which is much lower than the conventional method; Step 4, Superstructure construction: Complete the reinforcement binding, prestressing tensioning, and staged concrete pouring of the cast-in-place box girder (bottom web first, then top slab). Step 5, reverse earthwork excavation and formwork removal: After the main structure of the overpass reaches the design strength and is demolded, the earthwork below is excavated in layers. After excavating to the design elevation, the pier formwork is removed, the remaining earthwork is excavated (pier finishing), and finally the ground beam is poured. Step 6, Protection and Monitoring: During the excavation process, the existing piers are used as monitoring points, and the release of soil around the piers is monitored for safety.

[0008] This invention has the following advantages: 1. Significantly reduced safety risks: By constructing the substructure before excavation, the original 20-30 meter high-support construction is transformed into low-support operation, greatly improving the overall stability of the support and construction safety. 2. Shortened overall project duration: It enables parallel operation of bridge substructure construction and large-scale earthwork excavation of the roadbed, eliminating the absolute limitation of the roadbed excavation progress. 3. Reduced construction costs: It significantly reduces the rental and transportation costs of pipe fittings, fasteners, and reinforcement materials required for ultra-high supports. 4. Environmentally friendly: It reduces the need for temporary site leveling and large-scale slope excavation for high supports, protecting the stability of the original geological conditions. Attached Figure Description

[0009] Figures 1-2 This is a detailed schematic diagram of the template installation. Figure 3 This is a schematic diagram of a "low-height" support structure built using the original ground surface. Detailed Implementation

[0010] The following will be combined with the appendix Figures 1-3This invention will be described in detail, and the technical solutions in the embodiments of this invention will be clearly and completely described. Obviously, the described embodiments are only some embodiments of this invention, and not all embodiments. Based on the embodiments of this invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this invention.

[0011] This invention provides a reverse construction process for integrated pile and column construction of cast-in-place overpasses in deep road cuts. This process adopts a "construction first, excavation later, integrated" approach, with the specific steps as follows: Step 1, Leveling and positioning of the original ground: Before large-scale excavation of earth and rock, the original terrain is used as a construction platform; Step 2: Integrated segmented casting of piles and columns: Drilling process: Utilizing the original ground height, drilling is carried out along the same centerline according to the design requirements for pile diameter and pier diameter; Template installation: The pier template is pre-assembled on the ground and hoisted into the hole as a whole. Triangular limit clips are required at the junction of the pier and the pile foundation, and small steel (channel 20) is set at the lower end of the pier as temporary support. After the verticality is adjusted, sand is poured on the outside of the pier template to fix the template and prevent it from being affected during the excavation process. Post-casting embedded tie beam: Since the tie beam can only be constructed using the post-casting method, it is necessary to pre-embed the sleeve during the reinforcement construction. The sleeve is a Class I sleeve, and the pre-embedding is carried out according to the design reinforcement position.

[0012] Reinforcing cage extension: The bottom of the pile is cleaned with bricks using a rotary drilling machine. After cleaning, the reinforcing bars are installed. The reinforcing bars are processed in sections, and the processing method is the same as that for other pile foundations. Integrated casting: Concrete construction is carried out using the tremie pipe method; Step 3, Low-level scaffolding erection: After the substructure construction is completed, the box girder construction scaffolding is erected directly on the original ground (or a platform after shallow slope cutting). At this time, the scaffolding height is only the height from the bottom of the box girder to the original ground, which is much lower than the conventional method; Step 4, Superstructure construction: Complete the reinforcement binding, prestressing tensioning, and staged concrete pouring of the cast-in-place box girder (bottom web first, then top slab). Step 5, reverse earthwork excavation and formwork removal: After the main structure of the overpass reaches the design strength and is demolded, the earthwork below is excavated in layers. After excavating to the design elevation, the pier formwork is removed, the remaining earthwork is excavated (pier finishing), and finally the ground beam is poured. Step 6, Protection and Monitoring: During the excavation process, the existing piers are used as monitoring points, and the release of soil around the piers is monitored for safety.

[0013] The social benefits and use value obtained by this invention patent are described below; I. Social Benefits (I) Strengthening Construction Safety and Ensuring Life and Property Safety: Traditional deep-cut bridge construction relies on 20-30 meter high scaffolding operations. The stability of these scaffoldings is greatly affected by factors such as terrain and load, easily leading to scaffolding collapses, falls from heights, and other safety accidents, posing a serious threat to the lives of construction workers and project property. This invention, through a reverse process of "laying the scaffolding first and then excavating," transforms high-scaffolding operations into low-scaffolding operations, significantly improving the overall stability of the scaffolding and reducing safety risks from the source of construction. This not only effectively reduces the incidence of safety accidents, protects the personal safety of construction workers, and avoids economic losses and adverse social impacts caused by safety accidents, but also strengthens the industry's concept of safe construction, promotes the improvement of safety standards in the bridge construction field, and creates a safe and standardized construction environment.

[0014] (II) Implementing Green Construction Concepts and Protecting the Ecological Environment: Traditional high-support construction requires large-scale temporary site leveling and slope grading, which easily damages the original geological structure and causes ecological problems such as soil erosion and landslides. This is especially true in ecologically sensitive areas, where the disturbance to the surrounding ecological environment is more pronounced. This invention uses the original ground (or a shallow slope-cutting platform) as the construction foundation, reducing the scope of temporary site leveling and large-scale slope grading operations, maximizing the protection of the stability of the original geological surface, and reducing damage to the surrounding soil and vegetation. At the same time, process optimization reduces the use of materials such as ultra-high support pipes and fasteners, indirectly reducing energy consumption and pollutant emissions during material production and transportation, contributing to the construction of eco-friendly projects, and achieving coordinated development of construction and ecological protection.

[0015] (III) Promoting Technological Innovation and Enhancing Construction Standardization: This invention innovatively proposes a reverse construction process integrating piles and columns for cast-in-place bridges in deep road cuts, breaking through the traditional "excavation before construction" model and solving the industry pain point of mutual constraints between roadbed excavation and bridge substructure construction. Its key technologies, such as "integrated segmented casting of piles and columns," "post-cast pre-embedding of tie beams," and "reverse earthwork excavation," provide a completely new construction approach and technical paradigm for similar cast-in-place bridge projects in deep road cuts. Through the promotion and application of this process, it can drive the iterative upgrading of construction technologies within the industry, promote construction companies to optimize construction processes and enhance technical reserves, drive bridge construction towards high efficiency, standardization, and refinement, and enhance the core competitiveness of my country's bridge construction industry.

[0016] (iv) Reducing construction disturbance and ensuring the order of surrounding production and life: In traditional construction, the erection of high supports and large-scale earthwork excavation easily generate dust and noise pollution, and the construction period is long, causing significant interference to the lives of surrounding residents, traffic and the operation of surrounding facilities. This invention reduces the time of construction disturbance to the surrounding environment by shortening the total construction period and optimizing the construction process; the low support operation and reverse excavation method reduce the amount of construction noise and dust generated, effectively alleviating the conflict between construction and surrounding production and life, ensuring the normal life order of surrounding residents and traffic safety, and improving the social acceptance of the project construction.

[0017] II. Use Value (I) Reducing Construction Costs and Enhancing Project Economic Benefits: This invention achieves cost savings in construction from multiple dimensions, creating significant economic value for the project. On the one hand, low-support construction replaces high-support construction, significantly reducing the rental, transportation, and installation costs of pipe fittings, fasteners, and reinforcement materials required for ultra-high supports, thus lowering material costs and transportation energy consumption. On the other hand, the parallel operation of bridge substructure construction and large-scale earthwork excavation of the roadbed breaks the absolute limitation of roadbed excavation progress on the overall construction, shortens the total project duration, and reduces idle costs and management expenses for labor and machinery. Simultaneously, the reverse excavation process avoids rework costs and losses caused by accidents such as high-support collapse and slope landslides, further enhancing the project's profitability. It is particularly suitable for large-scale deep-cut bridge projects, where the cost-saving effect is even more pronounced.

[0018] (II) Optimizing the construction process and improving construction efficiency: This invention restructures the construction process through technological innovation, solving the problems of poor coordination and limited progress in traditional construction. The leveling and positioning of the original ground provides a stable foundation for subsequent construction. The integrated segmented pouring process for piles and columns achieves efficient connection between pile foundation and pier construction. Operations such as overall formwork hoisting and segmented processing of reinforcing cages improve construction accuracy and efficiency. The erection of low-level supports does not require waiting for the completion of roadbed excavation and can be seamlessly integrated with the construction of the superstructure. Reverse earthwork excavation is carried out after the main structure is stable, avoiding cross-construction interference. The entire process is tightly integrated and logically clear, significantly improving construction efficiency and ensuring the project is completed ahead of schedule or on time, laying the foundation for early commissioning. It has irreplaceable value, especially in key projects with tight deadlines.

[0019] (III) Enhancing Adaptability to Working Conditions and Expanding Application Scenarios: This invention is designed specifically for the characteristics of cast-in-place overpass construction in deep road cuts, effectively adapting to the bridge construction needs under complex geological conditions. Traditional methods are easily limited by terrain in cast-in-place overpass construction in deep road cuts, resulting in high construction difficulty and risk. This invention, however, utilizes low-profile supports erected on the original ground surface, combined with integrated pile-column construction and reverse excavation, eliminating the need for large-scale terrain modification and adapting to deep road cut projects of varying depths and geological types. Its application scenarios cover bridge construction in mountainous and hilly areas, including overpasses and cross-line bridges in transportation infrastructure such as highways and railways, providing a reliable technical solution for bridge construction under complex conditions and expanding the application scope of bridge construction technology.

[0020] (IV) Strengthening Construction Management and Improving Project Quality: This invention provides strong guarantees for project quality through refined construction design and process control. In the integrated pile-column construction, the use of triangular limiters and temporary steel channels ensures the connection accuracy between the pier and the pile foundation. The use of Class I sleeves for precise positioning in the post-cast pre-embedded tie beams improves the reliability of structural connections. The concrete tremie method, prestressing tensioning, and staged pouring process ensure the quality of the superstructure concrete and the structural stability. During excavation, the already formed piers are used as monitoring points to safely monitor the soil release process, which can promptly detect and address geological deformation and other issues, avoiding potential quality hazards. This technology can effectively improve the overall quality of bridge engineering, extend the service life of the project, reduce later maintenance costs, and provide a guarantee for the long-term stable operation of transportation infrastructure.

[0021] The above description of the disclosed embodiments enables those skilled in the art to make or use the invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the invention. Therefore, the invention is not to be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A reverse construction process for integrated pile and column construction of cast-in-place overpass in deep road cuts, characterized in that; This process involves construction followed by excavation, and is an integrated process. The specific steps are as follows: Step 1, Leveling and positioning of the original ground: Before large-scale excavation of earth and rock, the original terrain is used as a construction platform; Step 2: Integrated segmented casting of piles and columns: Drilling process: Utilizing the original ground height, drilling is carried out along the same centerline according to the design requirements for pile diameter and pier diameter; Template installation: The pier template is pre-assembled on the ground and hoisted into the hole as a whole. Triangular limit clips are required at the junction of the pier and the pile foundation, and small steel (channel 20) is set at the lower end of the pier as temporary support. After the verticality is adjusted, sand is poured on the outside of the pier template to fix the template and prevent it from being affected during the excavation process. Post-casting embedded tie beam: Since the tie beam can only be constructed by post-casting during the casting process, it is necessary to embed sleeves during the reinforcement construction. Class I sleeves are used and embedded according to the design reinforcement position. Reinforcing cage extension: The bottom of the pile is cleaned with bricks using a rotary drilling machine. After cleaning, the reinforcing bars are installed. The reinforcing bars are processed in sections, and the processing method is the same as that for other pile foundations. Integrated casting: Concrete construction is carried out using the tremie pipe method; Step 3, Low-level scaffolding erection: After the substructure construction is completed, the box girder construction scaffolding is erected directly on the original ground or on a platform after shallow slope cutting; at this time, the height of the scaffolding is only the height from the bottom of the box girder to the original ground, which is much lower than the conventional scheme. Step 4, Superstructure construction: Complete the reinforcement binding, prestressing tensioning, and staged concrete pouring of the cast-in-place box girder (bottom web first, then top slab). Step 5, reverse earthwork excavation and formwork removal: After the main structure of the overpass reaches the design strength and is demolded, the earthwork below is excavated in layers. After excavating to the design elevation, the pier formwork is removed, the remaining earthwork is excavated, and finally the ground beam is poured. Step 6, Protection and Monitoring: During the excavation process, the existing piers are used as monitoring points, and the release of soil around the piers is monitored for safety.

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