Assembly type pier column for alpine region and construction method

Abstract

The application discloses a fabricated pier column for high-cold regions and a construction method, relates to the technical field of building construction, and is composed of cofferdams on the two sides of a river bank, a pier structure in the cofferdams, a trestle bridge on the top of the pier, and four groups of lifting gantries with the same structure. The pier structure comprises a bridge span structure at the bottom of the trestle bridge, a bent cap at the bottom surface of the bridge span, and pier columns on the two sides of the bent cap; the lifting gantries are provided with gantry supports, and the lifting bridge surface between the gantries is arranged on the trestle bridge supports and flush with the top surface of the trestle bridge. The application can solve the construction problem of the pier column in the river channel in the high-cold region, and has the advantages of structural safety, construction efficiency and durability, and is suitable for special working conditions such as low temperature, freezing and thawing, and ice damage, and can improve the construction quality and operation safety.

Description

Technical Field

[0001] This invention relates to the field of building construction technology, and in particular to prefabricated piers and construction methods for use in high-altitude and cold regions. Background Technology

[0002] In high-altitude and cold regions, seasonal rivers often have sandy riverbeds. During the flood season, the water flow is intense, and ice floes and floating debris collide frequently. Traditional piers are prone to damage due to insufficient burial depth and poor erosion resistance. Conventional steel temporary bridge piers are difficult to meet the deep burial requirements, and the longitudinal beam structure cannot simultaneously withstand heavy construction loads and traffic needs, resulting in insufficient longitudinal stability.

[0003] Welding and concrete construction are prone to defects in low-temperature environments. Prefabricated connections have low precision and weak overall integrity, making them unsuitable for conditions involving ice damage, scour, and heavy loads. Existing piers are mostly cast-in-place, resulting in long construction cycles, significant weather-related limitations, and difficulties in quickly adjusting structural elevations during flood seasons, posing significant safety risks. There is an urgent need for a prefabricated, scour-resistant, low-temperature-resistant pier technology that allows for rapid construction and emergency control. Summary of the Invention

[0004] The purpose of this invention is to solve the problems existing in the prior art and to propose a prefabricated pier for use in high-altitude and cold regions.

[0005] To address the problems existing in the prior art, the present invention adopts the following technical solution: Prefabricated piers for high-altitude and cold regions include a pair of cofferdams, which are distributed on both sides of the riverbank. Each cofferdam contains a pier structure, and each pier structure is topped with a trestle bridge. A first lifting gantry, a second lifting gantry, a third lifting gantry, and a fourth lifting gantry are sequentially arranged between the pair of trestle bridges. The bridge pier structure includes a bridge span structure, a cap beam, and a pair of pier columns. The bridge span structure is installed on the bottom surface of the trestle bridge, the cap beam is installed on the bottom surface of the bridge span structure, and a pair of pier columns are fixedly installed on both sides of the bottom surface of the cap beam. The No. 1, No. 2, No. 3, and No. 4 lifting gantry have the same structure. The No. 1 lifting gantry includes a pair of gantry, and a trestle support is fixedly installed between the pair of gantry. Lifting bridge surfaces are respectively installed between the No. 1 and No. 2 lifting gantry, and between the No. 3 and No. 4 lifting gantry. The bottom surfaces of each lifting bridge surface are supported on the corresponding side of the trestle support, and the top surfaces of the pair of lifting bridge surfaces are flush with the top surfaces of the pair of trestle supports.

[0006] Preferably, a pair of wet joints are provided on the front and rear sides of the bridge span structure, a leveling layer is laid on the top surface of the bridge span structure, a waterproof layer is laid on the top surface of the leveling layer, and a paving layer is laid on the top surface of the waterproof layer.

[0007] Preferably, a pair of pad stones are fixedly provided on both sides of the top surface of the cap beam, and a pair of supports are fixedly provided on the top surface of each pad stone. A pair of load-bearing seats are fixedly provided on both sides of the bottom surface of the bridge span structure, and each load-bearing seat is nested on the support on the corresponding side.

[0008] Preferably, a tie beam is fixedly provided between the pair of piers, a pile cap is fixedly provided at the bottom of each pier, and a pile is fixedly provided at the corner of the bottom surface of each pile cap.

[0009] Preferably, a pair of anti-collision piers are fixedly installed on the left and right sides of the top surface of the bridge span structure, and a pair of stop blocks are fixedly installed at the left and right ends of the cap beam.

[0010] Preferably, a lifting beam is installed between the tops of the pair of gantry frames, and a pair of limiting through holes are provided on both sides of the top surface of the lifting beam.

[0011] Preferably, threaded steel bars are fixedly installed at the four corners of the top surface of the lifting bridge deck, and each threaded steel bar is inserted upward into the limiting through hole on the corresponding side.

[0012] Preferably, a pair of jacks are fixedly installed on both sides of the top surface of the lifting beam, and the top of each jack is fixedly connected to the top of the threaded steel bar on the corresponding side.

[0013] Preferably, lifting and dismantling plates are installed at all four corners of the top surface of the lifting bridge deck.

[0014] This invention also proposes a construction method for prefabricated piers in high-altitude and cold regions, comprising the following steps: Step 1: Riverbed pretreatment and positioning layout Ice-breaking and dredging equipment was used to break the ice cover and surface frozen soil layer in the river channel, and to clear floating debris, ice blocks and weak silt layers from the riverbed. For sandy riverbeds, rock dumping and vibration compaction are carried out, and graded crushed stone with a particle size of 5-30cm is dumped to form an erosion-resistant bearing layer with a thickness of not less than 80cm. Local scour pits are backfilled and leveled with bagged crushed stone. GPS-RTK and total station were used for joint layout to accurately locate the center of the pile foundation and the outline of the cofferdam, guide piles and elevation control points were set up, and the riverbed scour settlement during the ice period and flood season was re-measured. Step 2: Installation of Deep-Buried Prefabricated Steel Casing A combination of high-power vibratory hammer and crawler crane is used to install thickened spiral ribbed steel casing with a wall thickness of 16-20mm. Spiral anti-impact ribs are installed on the outer wall with a rib height of 15cm and a spacing of 50cm. The casing is buried at a depth that penetrates the sandy soil scour layer and enters a relatively stable soil layer by no less than 3.0m. The top of the casing is 1.5 to 2.0m above the design water level during the flood season, and it also serves as an ice rafting anti-collision device and a construction guide. The casing is equipped with transverse steel supports and diagonal tie rods to form a spatial truss system, which is connected by low-temperature high-strength bolts to avoid on-site welding; The gap between the outer side of the casing and the riverbed is backfilled with graded sand and gravel and cement grout, which is then grouted and solidified to form an anti-erosion coating layer to prevent the sandy soil from seeping and hollowing out. Step 3: Assemble and sink the prefabricated double-walled cofferdam The cofferdam is a prefabricated, segmented, double-walled steel cofferdam. The segments are connected by sealing strips, positioning pins, and high-strength bolts. The inner wall is equipped with a thermal insulation layer made of polyurethane foam with a thickness of 5cm. The cofferdam is prefabricated in 2 to 3 sections. The bottom section is equipped with a cutting edge structure and an anti-scouring skirt. The outer wall is welded with ice-cutting blades and anti-collision stiffening ribs, and the inner wall is pre-embedded with prestressed anchors and connecting components. The floating and symmetrical water injection sinking process is adopted. The cofferdam is equipped with multiple layers of internal support and a detachable steel truss. The tilt is monitored synchronously and the deviation is controlled to be ≤1 / 200. After the cofferdam is sunk to the design elevation of the riverbed, the bottom is sealed with underwater early-strength concrete, and low-temperature early-strength agent and antifreeze agent are added, with grade C30 and antifreeze grade F300; The top of the cofferdam is equipped with an elevation adjustment device, which combines hydraulic jacking and pad blocks. During the flood season, the elevation of the cofferdam and the piers can be quickly adjusted to avoid flood erosion. Step 4: Pile foundation construction and prefabrication and assembly of pile caps The casing is formed by rotary drilling and air lift reverse circulation. The mud uses a low temperature insulation circulation system with temperature control ≥10℃ to prevent freezing and hole collapse due to sandy soil. The steel cages are prefabricated in sections at the factory and connected on site using cold extrusion sleeves to avoid low-temperature welding defects. The pile foundation concrete adopts heated mixing, heat-insulated transportation and duct pouring. The raw materials are heated to 50℃, and the temperature of the concrete entering the formwork is ≥15℃. Temperature monitoring is carried out throughout the process. The foundation adopts a prefabricated assembly structure, which is prefabricated in sections in the factory, using C40 high-performance concrete with frost resistance F300 and impermeability P10, and pre-reserved prestressed ducts and shear tenons. After dewatering and clearing the foundation inside the cofferdam, precast foundation blocks are hoisted in, and low-temperature epoxy mortar with a thickness of 2cm is laid at the joints. Vertical prestressing tendons are then tensioned, and low-temperature early-strength grouting material is used for grouting the ducts. Step 5: Prefabrication and assembly of pier segments The piers are hollow prefabricated segments, each 3-6m high, with an internal steel core tube made of Q355ND low-temperature steel and an outer wall of high-performance concrete. The segment end face is equipped with multi-level shear-resistant tenon grooves and sealing water-stop strips, and pre-embedded through-type prestressed pipes and heat-insulating electric heating wires for low-temperature curing. Large crawler cranes and guide positioning frames are used to lift the segments, and low-temperature durable epoxy adhesive is applied to the joints. After precise alignment, the segments are temporarily fixed. After the entire pier column is assembled, the prestressed tendons are tensioned along the entire length, and the low-temperature, low-relaxation steel strands are used to achieve segmental integration, with a tensioning temperature of ≥-10℃. The outer side of the pier is equipped with a prefabricated ice-pump anti-collision ring, a rubber buffer layer and a steel shell, and the bottom is fixed to the top of the cofferdam to resist the impact of ice pies. Step Six: Low Temperature Protection and Quality Control A fully enclosed heat-insulating shed was erected around the cofferdam and piers, equipped with heat pumps and electric blankets to maintain the construction environment temperature at ≥5℃. Key processes such as concrete joints, prestressing tensioning, and grouting are concentrated during the high-temperature period of daytime to avoid extreme low temperatures and snowy weather. Wireless temperature sensors are used to monitor the temperature inside the concrete, inside the insulation shed, and in the environment in real time, and the heating system is automatically adjusted accordingly. The steel structure connections and prestressed anchorage areas are coated with antifreeze and anticorrosion coatings, and sealed with polyurea and epoxy to prevent freeze-thaw corrosion. Step 7: Cofferdam Removal and Riverbed Protection After the pier reaches its design strength, the prestress is released in stages, and the internal supports and top adjustment devices are removed. The cofferdam was constructed using segmented cutting and dismantling, with bolted connections being dismantled first for reuse. Prefabricated anti-scouring plates, precast concrete blocks and geotextiles are laid around the riverbed, covering an area of ​​5 to 8 meters around the pier, to prevent scouring during the flood season. Clean the river channel, restore the riverbed topography, and install ice-drainage diversion facilities to reduce the impact of ice damage; Step 8: Monitoring and Dynamic Regulation Deploy automated monitoring systems for: riverbed scour, pier settlement, tilting, ice melt impact force, temperature stress, and prestress loss; Real-time monitoring and early warning during the flood and ice seasons allow for rapid adjustment of pier elevations and reinforcement of ice-resistant structures to ensure safety.

[0015] Compared with the prior art, the beneficial effects of the present invention are: 1. In this invention, it is adapted to high-altitude and cold working conditions. Structures such as cofferdams and insulation layers can block river water and resist freeze-thaw erosion. Anti-collision rings and scour-resistant bearing layers can cope with ice floe impacts and riverbed scouring, avoid structural damage, and extend service life. 2. In this invention, the structure has strong stability, with components such as piers, tie beams, and pile caps working together to bear the load. Flexible connections and prestressed design buffer temperature deformation and load impact, effectively controlling displacement and adapting to soft foundations and complex stress scenarios in cold regions. 3. In this invention, construction is efficient and convenient. It adopts a factory prefabrication and on-site assembly mode to avoid low-temperature welding defects. It is equipped with low-temperature construction technology and monitoring system to achieve rapid construction. Moreover, the components can be reused, reducing construction costs. In summary, this invention can solve the construction problems of river piers in high-altitude and cold regions, taking into account structural safety, construction efficiency and durability, and is suitable for special working conditions such as low temperature, freeze-thaw and ice damage in high-altitude and cold regions, thereby improving construction quality and operational safety. Attached Figure Description

[0016] The accompanying drawings, which are included to provide a further understanding of the invention and form part of this application, illustrate exemplary embodiments of the invention and, together with their description, serve to explain the invention and do not constitute an undue limitation thereof. In the drawings: Figure 1 This is a schematic diagram of the overall structure of the present invention; Figure 2 This is a schematic diagram of the cross-section of the steel temporary bridge and the gantry before lifting according to the present invention; Figure 3 For the present invention Figure 2 Enlarged view of point A in the middle; Figure 4 This is a schematic diagram of the side of the steel temporary bridge and the gantry before lifting according to the present invention; Figure 5 This is a schematic diagram of the cross-section and gantry of the steel temporary bridge after lifting according to the present invention; Figure 6 This is a schematic diagram of the bridge pier structure of the present invention; Figure 7 This is an exploded view of the bridge pier structure of the present invention; Figure 8 This is a schematic diagram showing the distribution of the No. 2 and No. 3 lifting gantry frames of the present invention; Figure 9 This is a schematic diagram showing the distribution of the cofferdam and pier structures of the present invention; The numbers in the diagram are as follows: 100, trestle bridge support; 101, lifting gantry No. 1; 102, lifting gantry No. 2; 103, lifting gantry No. 3; 104, lifting gantry No. 4; 200, gantry; 201, lifting bridge deck; 202, lifting demolition slab; 203, lifting crossbeam; 204, rebar; 205, jack; 206, trestle bridge support; 300, cofferdam; 301, pier structure; 302, cap beam; 303, pier column; 304, tie beam; 305, pier cap; 306, pile; 307, stop block; 308, pad stone; 309, bearing; 310, load-bearing seat; 311, bridge span structure; 312, crash barrier; 313, wet joint; 314, leveling layer; 315, waterproof layer; 316, pavement layer. Detailed Implementation

[0017] The technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings of the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments.

[0018] Example 1: This example provides prefabricated piers for use in high-altitude and cold regions. See [link / reference]. Figures 1 to 9 Specifically, it includes a pair of cofferdams 300, which are distributed on both sides of the riverbank. The cofferdams 300 are used to block the river water and provide a dry and safe working environment for the construction and installation of the internal bridge pier structure 301. They are suitable for river construction conditions in cold regions. Each cofferdam 300 is equipped with a bridge pier structure 301. The bridge pier structure 301 serves as the core load-bearing body of the prefabricated pier column 303, bearing the load of the upper support bridge 100 and the gantry structure, and ensuring the stability of the overall structure. Each pier structure 301 has a support bridge 100 installed on its top. The support bridge 100 provides an installation foundation for the No. 1 to No. 4 lifting gantry frames and is flush with the lifting bridge deck 201 to form a complete passage and operation surface. Between a pair of support bridges 100, the No. 1 lifting gantry frame 101, the No. 2 lifting gantry frame 102, the No. 3 lifting gantry frame 103 and the No. 4 lifting gantry frame 104 are arranged in sequence. The pier structure 301 includes a bridge span structure 311, a cap beam 302, and a pair of piers 303. The bridge span structure 311 is installed on the bottom surface of the trestle bridge 100. The bridge span structure 311 bears the upper load and transfers it to the cap beam 302. It is a key load-bearing component connecting the piers 303 and the bridge deck. The cap beam 302 is installed on the bottom surface of the bridge span structure 311. The cap beam 302 bears the upper load and evenly transfers it to the piers 303 on both sides, coordinating the force on the piers 303. A pair of piers 303 are fixedly installed on both sides of the bottom surface of the cap beam 302. The piers 303 serve as vertical load-bearing components and transfer the upper load to the abutment 305. The No. 1 lifting gantry 101, the No. 2 lifting gantry 102, the No. 3 lifting gantry 103, and the No. 4 lifting gantry 104 have the same structure and together constitute the lifting operation system to realize the prefabricated lifting and installation of the bridge deck 201, which is suitable for the rapid construction needs of high-altitude and cold regions. The No. 1 lifting gantry 101 includes a pair of gantry 200. The gantry 200 provides support for the lifting beam 203 and the trestle support 206 and is the vertical load-bearing skeleton for the lifting operation. The trestle support 206 is fixedly installed between the pair of gantry 200. The trestle support 206 is used to overlap and support the lifting bridge deck 201 to ensure that the lifting bridge deck 201 is installed firmly and is flush with the top surface of the trestle 100. Lifting bridge decks 201 are respectively set between lifting gantry 101 and lifting gantry 102, and between lifting gantry 103 and lifting gantry 104. The lifting bridge decks 201 and the support bridges 100 form a through operation platform. Prefabricated lifting assembly can be achieved through the lifting structure. The bottom surfaces of each lifting bridge deck 201 are erected on the corresponding side of the bridge support 206, and the top surfaces of a pair of lifting bridge decks 201 are flush with the top surfaces of a pair of support bridges 100.

[0019] It should be noted that: such as Figure 6 and Figure 7 As shown, a pair of anti-collision piers 312 are fixedly installed on the left and right sides of the top surface of the bridge span structure 311. The anti-collision piers 312 serve as anti-collision protection, protecting the bridge span structure 311 from impact damage under complex working conditions in cold regions. A pair of wet joints 313 are opened on the front and rear sides of the bridge span structure 311. The wet joints 313 are used for the connection and pouring between the bridge span structures 311, improving the integrity of the prefabricated pier columns 303. A leveling layer 314 is laid on the top surface of the bridge span structure 311. 314 achieves leveling of the bridge deck base, providing a flat base surface for the subsequent laying of the waterproof layer 315 and the pavement layer 316. The waterproof layer 315 is laid on the top surface of the leveling layer 314. The waterproof layer 315 prevents water from seeping into the interior of the bridge span structure 311, resists freeze-thaw erosion in cold regions, and extends the service life of the structure. The pavement layer 316 is laid on the top surface of the waterproof layer 315. The pavement layer 316 serves as the bridge deck service layer, bearing traffic and operational loads, and is suitable for the low temperature and wear-resistant use requirements in cold regions. A pair of stop blocks 307 are fixedly installed at both ends of the cap beam 302. The stop blocks 307 restrict the lateral displacement of the bridge span structure 311 and improve the displacement stability of the prefabricated structure in cold regions. A pair of pad stones 308 are fixedly installed on both sides of the top surface of the cap beam 302. The pad stones 308 provide a flat support surface for the support 309 and distribute the force on the support 309. A pair of supports 309 are fixedly installed on the top surface of each pad stone 308. The supports 309 and the load-bearing seats 310 are nested together to realize the flexible connection between the bridge span structure 311 and the cap beam 302, buffering the temperature deformation and load impact in cold regions. A pair of load-bearing seats 310 are fixedly installed on both sides of the bottom surface of the bridge span structure 311. Each load-bearing seat 310 is nested on the support 309 on the corresponding side. The load-bearing seats 310 and the support 309 are nested together to transfer the load of the bridge span structure 311 to the support 309. A tie beam 304 is fixedly installed between a pair of piers 303. The tie beam 304 enhances the integrity of the piers 303 and improves the structural resistance to lateral pressure in cold regions. A pile cap 305 is fixedly installed at the bottom of each pier 303. The pile cap 305 bears the load of the pier 303 and evenly transfers it to the lower piles 306, thereby improving the structural stability. A pile 306 is fixedly installed at the bottom corner of each pile cap 305. The piles 306 penetrate into the foundation and transfer all the upper load to the bearing layer of the foundation, which is suitable for soft foundation conditions in cold regions.

[0020] In the specific implementation process, such as Figure 2 and Figure 5 As shown, a lifting beam 203 is installed between the tops of a pair of gantry frames 200. It is placed when lifting is needed and left empty at other times. The lifting beam 203 provides an installation carrier for the jacks 205 and the threaded steel bars 204. It is the core force transmission component for lifting operations. A pair of limiting through holes are opened on both sides of the top surface of the lifting beam 203. Threaded steel bars 204 are fixedly installed at the four corners of the top surface of the lifting bridge deck 201. Each threaded steel bar 204 is inserted upward into the limiting through hole on the corresponding side. A pair of jacks 205 are fixedly installed on both sides of the top surface of the lifting beam 203. The jacks 205 provide lifting power to realize the prefabricated lifting of the bridge deck 201. The top of each jack 205 is fixedly connected to the top of the corresponding threaded steel bar 204. Lifting removal plates 202 are installed at the four corners of the top surface of the lifting bridge deck 201. The lifting removal plates 202 are removed during the lifting operation to reserve space for the lifting operation and not affect the implementation of the lifting operation.

[0021] Example 2: Based on Example 1, this example also proposes a construction method for prefabricated piers in high-altitude and cold regions, including the following steps: Step 1: Riverbed pretreatment and positioning layout Ice-breaking and dredging equipment was used to break the ice cover and surface frozen soil layer in the river channel, and to clear floating debris, ice blocks and weak silt layers from the riverbed. For sandy riverbeds, rock dumping and vibration compaction are carried out, and graded crushed stone with a particle size of 5-30cm is dumped to form an erosion-resistant bearing layer with a thickness of not less than 80cm. Local scour pits are backfilled and leveled with bagged crushed stone. GPS-RTK and total station were used for joint layout to accurately locate the center of the pile foundation and the 300mm outline of the cofferdam. Guide piles and elevation control points were set up, and the riverbed scour settlement during the ice period and flood season was re-measured. Step 2: Installation of Deep-Buried Prefabricated Steel Casing A combination of high-power vibratory hammer and crawler crane is used to install thickened spiral ribbed steel casing with a wall thickness of 16-20mm. Spiral anti-impact ribs are installed on the outer wall with a rib height of 15cm and a spacing of 50cm. The casing is buried at a depth that penetrates the sandy soil scour layer and enters a relatively stable soil layer by no less than 3.0m. The top of the casing is 1.5 to 2.0m above the design water level during the flood season, and it also serves as an ice rafting anti-collision device and a construction guide. The casing is equipped with transverse steel supports and diagonal tie rods to form a spatial truss system, which is connected by low-temperature high-strength bolts to avoid on-site welding; The gap between the outer side of the casing and the riverbed is backfilled with graded sand and gravel and cement grout, which is then grouted and solidified to form an anti-erosion coating layer to prevent the sandy soil from seeping and hollowing out. Step 3: Assemble and sink the prefabricated double-walled cofferdam at a depth of 300 mm. The 300 cofferdam adopts a factory-prefabricated segmented double-walled steel cofferdam. The segments are connected by sealing strips, positioning pins and high-strength bolts. The inner wall is equipped with a heat insulation layer, polyurethane foam, with a thickness of 5cm. The cofferdam is prefabricated in 2 to 3 sections, with the bottom section equipped with a cutting edge structure and an anti-scouring skirt. The outer wall is welded with ice-cutting blades and anti-collision stiffening ribs, and the inner wall is pre-embedded with prestressed anchors and connecting components. The floating and symmetrical water injection sinking process is adopted. The cofferdam is equipped with multiple layers of internal support within 300 mm, and a detachable steel truss is installed. The tilt is monitored simultaneously and the deviation is controlled to be ≤1 / 200. After the cofferdam is sunk to the design elevation of the riverbed, the bottom is sealed with underwater early-strength concrete, and low-temperature early-strength agent and antifreeze agent are added, with grade C30 and antifreeze grade F300; The top of the cofferdam 300 is equipped with an elevation adjustment device, which combines hydraulic jacking and pad blocks. During the flood season, the elevation of the cofferdam 300 and the pier 303 can be quickly adjusted to avoid flood erosion. Step 4: Pile foundation construction and 305 precast assembly of pile caps The casing is formed by rotary drilling and air lift reverse circulation. The mud uses a low temperature insulation circulation system with temperature control ≥10℃ to prevent freezing and hole collapse due to sandy soil. The steel cages are prefabricated in sections at the factory and connected on site using cold extrusion sleeves to avoid low-temperature welding defects. The pile foundation concrete adopts heated mixing, heat-insulated transportation and duct pouring. The raw materials are heated to 50℃, and the temperature of the concrete entering the formwork is ≥15℃. Temperature monitoring is carried out throughout the process. The 305 foundation adopts a prefabricated assembly structure, which is prefabricated in sections in the factory, using C40 high-performance concrete, with frost-resistant F300 and impermeable P10, and pre-reserved prestressed ducts and shear tenons. After dewatering and clearing the foundation within 300 meters of the cofferdam, 305 precast foundation pieces were hoisted in, and the joints were laid with low-temperature epoxy mortar with a thickness of 2cm. The vertical prestressing tendons were then tensioned, and low-temperature early-strength grouting material was used for grouting the ducts. Step 5: Prefabrication and assembly of pier segment 303 Pier 303 adopts hollow prefabricated segments, which are prefabricated in the factory. Each segment is 3 to 6 meters high, with an internal steel core tube made of Q355ND low-temperature steel and an outer wall of high-performance concrete. The segment end face is equipped with multi-level shear-resistant tenon grooves and sealing water-stop strips, and pre-embedded through-type prestressed pipes and heat-insulating electric heating wires for low-temperature curing. Large crawler cranes and guide positioning frames are used to lift the segments, and low-temperature durable epoxy adhesive is applied to the joints. After precise alignment, the segments are temporarily fixed. After the entire pier column 303 is assembled, the prestressed tendons and low-temperature, low-relaxation steel strands are tensioned as a whole to achieve segmental integration, with a tensioning temperature ≥-10℃; The outer side of pier 303 is equipped with a prefabricated ice-pump anti-collision ring, a rubber buffer layer and a steel shell, and the bottom is fixedly connected to the top of cofferdam 300 to resist the impact of ice plenums. Step Six: Low Temperature Protection and Quality Control A fully enclosed heat-insulating shed was erected around the cofferdam 300 and pier 303, equipped with warm air cannons and electric blankets to maintain the construction environment temperature ≥5℃. Key processes such as concrete joints, prestressing tensioning, and grouting are concentrated during the high-temperature period of daytime to avoid extreme low temperatures and snowy weather. Wireless temperature sensors are used to monitor the temperature inside the concrete, inside the insulation shed, and in the environment in real time, and the heating system is automatically adjusted accordingly. The steel structure connections and prestressed anchorage areas are coated with antifreeze and anticorrosion coatings, and sealed with polyurea and epoxy to prevent freeze-thaw corrosion. Step 7: Removal of the 300mm cofferdam and riverbed protection After the pier column 303 reaches the design strength, the prestress is released in stages, and the internal support and top adjustment device are removed. The 300mm cofferdam was cut and dismantled in sections, with bolted connections being dismantled first for reuse. Prefabricated anti-scouring plates, precast concrete blocks and geotextiles are laid around the riverbed, covering an area of ​​5 to 8 meters around the pier, to prevent scouring during the flood season. Clean the river channel, restore the riverbed topography, and install ice-drainage diversion facilities to reduce the impact of ice damage; Step 8: Monitoring and Dynamic Regulation Deploy automated monitoring systems for: riverbed scour, settlement and tilting of pier 303, ice floe impact force, temperature stress, and prestress loss; Real-time monitoring and early warning during the flood and ice seasons, rapid adjustment of the pier elevation to 303 meters, and reinforcement of ice-resistant structures to ensure safety.

[0022] The above description is only a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any equivalent substitutions or modifications made by those skilled in the art within the scope of the technology disclosed in the present invention, based on the technical solution and inventive concept of the present invention, should be covered within the scope of protection of the present invention.

Claims

1. A prefabricated pier for use in high-altitude and cold regions, comprising a pair of cofferdams (300), characterized in that: A pair of cofferdams (300) are distributed on both sides of the riverbank. Each cofferdam (300) is equipped with a pier structure (301). A trestle bridge (100) is installed on the top of each pier structure (301). A first lifting gantry (101), a second lifting gantry (102), a third lifting gantry (103), and a fourth lifting gantry (104) are arranged between the pair of trestle bridges (100). The bridge pier structure (301) includes a bridge span structure (311), a cap beam (302), and a pair of piers (303). The bridge span structure (311) is installed on the bottom surface of the trestle bridge (100). The cap beam (302) is installed on the bottom surface of the bridge span structure (311), and a pair of piers (303) are fixedly installed on both sides of the bottom surface of the cap beam (302). The No. 1 lifting gantry (101), No. 2 lifting gantry (102), No. 3 lifting gantry (103), and No. 4 lifting gantry (104) have the same structure. The No. 1 lifting gantry (101) includes a pair of gantry (200), and a trestle support (206) is fixedly provided between the pair of gantry (200). Lifting bridge surfaces (201) are respectively provided between the No. 1 lifting gantry (101) and the No. 2 lifting gantry (102), and between the No. 3 lifting gantry (103) and the No. 4 lifting gantry (104). The bottom surfaces of each lifting bridge surface (201) are supported on the corresponding side of the trestle support (206), and the top surfaces of the pair of lifting bridge surfaces (201) are flush with the top surfaces of the pair of trestle supports (100).

2. The prefabricated pier for high-altitude and cold regions according to claim 1, characterized in that: A pair of wet joints (313) are provided on the front and rear sides of the bridge span structure (311). A leveling layer (314) is laid on the top surface of the bridge span structure (311). A waterproof layer (315) is laid on the top surface of the leveling layer (314). A paving layer (316) is laid on the top surface of the waterproof layer (315).

3. The prefabricated pier for high-altitude and cold regions according to claim 1, characterized in that: A pair of pad stones (308) are fixedly installed on both sides of the top surface of the cap beam (302). A pair of supports (309) are fixedly installed on the top surface of each pad stone (308). A pair of load-bearing seats (310) are fixedly installed on both sides of the bottom surface of the bridge span structure (311). Each load-bearing seat (310) is nested on the support (309) on the corresponding side.

4. The prefabricated pier for high-altitude and cold regions according to claim 1, characterized in that: A tie beam (304) is fixedly provided between a pair of piers (303), and a pile cap (305) is fixedly provided at the bottom end of each pier (303), and a pile (306) is fixedly provided at the bottom corner of each pile cap (305).

5. The prefabricated pier for high-altitude and cold regions according to claim 1, characterized in that: A pair of anti-collision piers (312) are fixedly installed on the left and right sides of the top surface of the bridge span structure (311), and a pair of stop blocks (307) are fixedly installed at the left and right ends of the cap beam (302).

6. The prefabricated pier for high-altitude and cold regions according to claim 1, characterized in that: A lifting beam (203) is installed between the tops of a pair of gantry frames (200), and a pair of limiting through holes are provided on both sides of the top surface of the lifting beam (203).

7. The prefabricated pier for high-altitude and cold regions according to claim 6, characterized in that: The top surface of the lifting bridge deck (201) is fixedly provided with threaded steel bars (204) at the four corners, and each threaded steel bar (204) is inserted upward into the limiting through hole on the corresponding side.

8. The prefabricated pier for high-altitude and cold regions according to claim 7, characterized in that: A pair of jacks (205) are fixedly installed on both sides of the top surface of the lifting beam (203), and the top of each jack (205) is fixedly connected to the top of the threaded steel (204) on the corresponding side.

9. The prefabricated pier for high-altitude and cold regions according to claim 1, characterized in that: Lifting and dismantling plates (202) are installed at the four corners of the top surface of the lifting bridge deck (201).

10. The construction method for prefabricated piers in high-altitude and cold regions according to any one of claims 1-9, characterized in that, Includes the following steps: Step 1: Riverbed pretreatment and positioning layout Ice-breaking and dredging equipment was used to break the ice cover and surface frozen soil layer in the river channel, and to clear floating debris, ice blocks and weak silt layers from the riverbed. For sandy riverbeds, rock dumping and vibration compaction are carried out, and graded crushed stone with a particle size of 5-30cm is dumped to form an erosion-resistant bearing layer with a thickness of not less than 80cm. Local scour pits are backfilled and leveled with bagged crushed stone. GPS-RTK and total station were used for joint layout to accurately locate the center of the pile foundation and the outline of the cofferdam (300), guide piles and elevation control points were set up, and the riverbed scour settlement during the ice period and flood season was re-measured; Step 2: Installation of Deep-Buried Prefabricated Steel Casing A combination of high-power vibratory hammer and crawler crane is used to install thickened spiral ribbed steel casing with a wall thickness of 16-20mm. Spiral anti-impact ribs are installed on the outer wall with a rib height of 15cm and a spacing of 50cm. The casing is buried at a depth that penetrates the sandy soil scour layer and enters a relatively stable soil layer by no less than 3.0m. The top of the casing is 1.5 to 2.0m above the design water level during the flood season, and it also serves as an ice rafting anti-collision device and a construction guide. The casing is equipped with transverse steel supports and diagonal tie rods to form a spatial truss system, which is connected by low-temperature high-strength bolts to avoid on-site welding; The gap between the outer side of the casing and the riverbed is backfilled with graded sand and gravel and cement grout, which is then grouted and solidified to form an anti-erosion coating layer to prevent the sandy soil from seeping and hollowing out. Step 3: Assemble and sink the prefabricated double-walled cofferdam (300). The cofferdam (300) adopts a factory-prefabricated segmented double-walled steel cofferdam. The segments are connected by sealing strips, positioning pins and high-strength bolts. The inner wall is equipped with a heat insulation layer, polyurethane foam, with a thickness of 5cm. The cofferdam (300) is prefabricated in 2 to 3 sections. The bottom section is equipped with a cutting edge structure and an anti-scouring skirt. The outer wall is welded with ice-cutting blades and anti-collision stiffening ribs. The inner wall is pre-embedded with prestressed anchors and connecting components. The floating and symmetrical water injection sinking process is adopted. The cofferdam (300) is equipped with multi-layer internal support and detachable steel truss. The tilt is monitored synchronously and the deviation is controlled to be ≤1 / 200. After the cofferdam (300) is sunk to the design elevation of the riverbed, the bottom is sealed with underwater early-strength concrete, and low-temperature early-strength agent and antifreeze agent are added, with grade C30 and antifreeze grade F300; The top of the cofferdam (300) is equipped with an elevation adjustment device, which is a combination of hydraulic jacking and pad blocks. During the flood season, the elevation of the cofferdam (300) and the pier (303) can be quickly adjusted to avoid flood erosion. Step 4: Pile foundation construction and prefabrication and assembly of pile cap (305) The casing is formed by rotary drilling and air lift reverse circulation. The mud uses a low temperature insulation circulation system with temperature control ≥10℃ to prevent freezing and hole collapse due to sandy soil. The steel cages are prefabricated in sections at the factory and connected on site using cold extrusion sleeves to avoid low-temperature welding defects. The pile foundation concrete adopts heated mixing, heat-insulated transportation and duct pouring. The raw materials are heated to 50℃, and the temperature of the concrete entering the formwork is ≥15℃. Temperature monitoring is carried out throughout the process. The foundation (305) adopts a prefabricated assembly structure, which is prefabricated in sections in the factory, using C40 high-performance concrete, with frost-resistant F300 and impermeable P10, and pre-stressed ducts and shear tenons. After the cofferdam (300) is pumped out and the foundation is cleared, the precast foundation (305) blocks are hoisted, the joints are laid with low-temperature epoxy mortar with a thickness of 2cm, the vertical prestressing tendons are tensioned, and the duct grouting uses low-temperature early strength grouting material. Step 5: Prefabrication and assembly of pier (303) segments The pier (303) adopts hollow prefabricated segments, which are prefabricated in the factory. Each segment is 3 to 6 meters high, with an internal steel core tube made of Q355ND low temperature steel and an outer wall of high performance concrete. The segment end face is equipped with multi-level shear-resistant tenon grooves and sealing water-stop strips, and pre-embedded through-type prestressed pipes and heat-insulating electric heating wires for low-temperature curing. Large crawler cranes and guide positioning frames are used to lift the segments, and low-temperature durable epoxy adhesive is applied to the joints. After precise alignment, the segments are temporarily fixed. After the entire pier column (303) is assembled, the prestressed tendons are tensioned along the entire length, and the low-temperature, low-relaxation steel strands are used to achieve segmental integration. The tensioning temperature is ≥-10℃. The outer side of the pier (303) is equipped with a prefabricated ice chute anti-collision ring, a rubber buffer layer and a steel shell, and the bottom is fixed to the top of the cofferdam (300) to resist the impact of ice chute; Step Six: Low Temperature Protection and Quality Control A fully enclosed heat preservation shed was erected around the cofferdam (300) and the pier (303), equipped with a heat pump and electric blankets to maintain the construction environment temperature ≥5℃; Key processes such as concrete joints, prestressing tensioning, and grouting are concentrated during the high-temperature period of daytime to avoid extreme low temperatures and snowy weather. Wireless temperature sensors are used to monitor the temperature inside the concrete, inside the insulation shed, and in the environment in real time, and the heating system is automatically adjusted accordingly. The steel structure connections and prestressed anchorage areas are coated with antifreeze and anticorrosion coatings, and sealed with polyurea and epoxy to prevent freeze-thaw corrosion. Step 7: Cofferdam (300) removal and riverbed protection After the pier (303) reaches the design strength, the prestress is released in stages, and the internal support and top adjustment device are removed. The cofferdam (300) is cut and dismantled in sections, with bolted connections being dismantled first for reuse. Prefabricated anti-scouring plates, precast concrete blocks and geotextiles are laid around the riverbed, covering an area of ​​5 to 8 meters around the pier, to prevent scouring during the flood season. Clean the river channel, restore the riverbed topography, and install ice-drainage diversion facilities to reduce the impact of ice damage; Step 8: Monitoring and Dynamic Regulation Deploy automated monitoring systems for: riverbed scour, pier (303) settlement, tilting, ice floe impact force, temperature stress, and prestress loss; Real-time monitoring and early warning during the flood and ice seasons, rapid adjustment of the pier (303) elevation, and reinforcement of the ice-resistant structure to ensure safety.

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