Bridge bearing platform construction method

Abstract

The invention discloses a bridge bearing platform construction method which comprises the following steps: excavating a bearing platform pit foundation on the periphery of a pile foundation according to a design drawing and a field geological exploration condition, sequentially leveling a slope surface, inserting and driving soil nails and paving a reinforcing mesh, and then carrying out shotcreting and anchoring operation by adopting C20 shotcreting concrete; annularly cutting the designed elevation position of the pile head of the foundation pile by using a grinding machine; after the bearing platform reinforcement cage is manufactured into the bearing platform reinforcement cage, a cooling structure is installed on the bearing platform reinforcement cage; the manufactured bearing platform steel reinforcement framework is placed at the planned position in the bearing platform pit foundation, and then a pouring model corresponding to the bearing platform structure is installed according to the reference line; and the center main tower bearing platform, the auxiliary piers and the transition pier bearing platform are poured in a layered mode, and after the bearing platforms are maintained, the foundation pit needs to be backfilled with pit foundation excavation earthwork in time. The technical problem that the geological stability is poor when bearing platform construction is carried out on an inclined riverbed surface or a near abrupt slope can be solved, and the temperature in the bearing platform can be controlled.

Description

Technical Field

[0001] The invention belongs to the technical field of bridge construction, and in particular relates to a bridge pedestal construction method. Background Art

[0002] A cap is a structure designed to bear and distribute the loads transmitted by the pier. It connects the piles and columns or piers, and is the reinforced concrete foundation connecting the lower portion of the pier to the top of the pile foundation. Connecting several or even dozens of piles, the cap is one of the most important structures in bridge construction. Its large size and high concrete volume make it a large-volume concrete construction project. Construction of large-volume main pier caps is generally done in layers or in a single pour. Whether this is done in layers or poured in a single pour, the shrinkage and creep effects of concrete significantly impact the cap structure, increasing the scale of foundation construction and making it difficult to control changes in the cap's internal structure. Furthermore, when cap construction is required on a sloping riverbed or on a steep slope, the poor geological stability of these slopes makes construction difficult and dangerous, leading to excessive excavation of the foundation pit slope or significant investment in excavation protection works. This increases the complexity and requirements of large-volume main pier cap construction, significantly increasing construction costs and often significantly impacting the cap's quality and progress. Summary of the Invention

[0003] The present invention aims to provide a bridge abutment construction method that not only addresses the technical issue of poor geological stability during abutment construction on a sloping riverbed or steep slope, but also utilizes staggered cooling pipes to control the internal temperature of the abutment, thereby preventing and improving the occurrence of cracks in the abutment. To achieve the above objectives, the present invention employs the following technical effects:

[0004] According to one aspect of the present invention, a bridge cap construction method is provided, the cap construction method comprising the following steps:

[0005] Step 1: Excavation of the foundation cap. According to the design drawings and on-site geological survey, the foundation cap is excavated around the pile foundation. Two slopes with a slope ratio of at least 1:1 to 1.5 are excavated around the foundation pit. When the excavation reaches the designed pit bottom elevation or the slope boundary, a 20-30 cm thick soil layer is reserved. Then, manual excavation and slope repair are carried out. A drainage ditch is excavated along the excavation edge of the top and bottom of the foundation pit slope. A platform of at least 1-2 m is reserved between the bottom of the slope and the outside of the foundation cap at the bottom of the foundation pit.

[0006] Step 2: Slope protection: Slope leveling, soil nailing, laying steel mesh, and then using C20 shotcrete for anchoring.

[0007] Step 3: Remove the foundation piles. Use a grinding wheel to perform circular cutting at the designed elevation of the foundation pile head to remove the concrete protective layer of the over-filled pile head.

[0008] Step 4: Fabrication of the cap reinforcement skeleton. The fabrication process is as follows: straightening the pile head reinforcement, installing the bottom anti-crack mesh, installing the bottom reinforcement, installing the pile top reinforcement mesh, installing the pile head stirrups, installing the frame reinforcement, installing the top inner reinforcement, installing the side outer reinforcement, installing the top outer reinforcement, installing the tower base embedded reinforcement and the main tower cap frame and pier body embedded segments. After the cap reinforcement skeleton is formed, the cooling structure is installed on the cap reinforcement skeleton.

[0009] Step 5: Install the casting model. Place the prepared cap reinforcement skeleton at the planned position in the cap pit foundation. Then, mark the reference lines for the construction and installation template along the four sides of the cap reinforcement skeleton. Install the casting model corresponding to the cap structure according to the reference lines.

[0010] Step 6: Concrete pouring and curing. The central main tower cap uses C35 concrete, and the other auxiliary piers and transition pier caps use C30 concrete. They are poured layer by layer in the formwork. The thickness of each layer is not less than 35cm. When a layer of concrete is poured, cooling water is gradually supplied to the cooling structure. The cooling water flow rate is increased every 30s-60s. After the entire cap is poured and solidified, the cooling water is withdrawn. Then, the concrete is cured until it reaches the required strength and the formwork is removed.

[0011] Step 7: After the foundation pile maintenance is completed, the foundation pit should be backfilled with excavated soil in time. Before the pier body is constructed, the backfill soil of the foundation pit should be no more than 30cm lower than the foundation pile, and drainage ditches should be excavated around the foundation pile to allow rainwater to be discharged in a targeted manner.

[0012] The above solution is further preferred, wherein the casting model corresponding to the base structure is installed according to the reference line, comprising the following steps:

[0013] First, before installation, clean the stains on the formwork and set support blocks at the bottom and both sides of the frame. Install the formwork on the upper and lower sides of the pedestal respectively. Adjust the verticality and plane position of the formwork so that it is in a straight line horizontally and vertically. Then connect the formwork to the steel bars of the foundation piles through embedded steel bars so that the formwork is engaged in the foundation pit.

[0014] Secondly, standard steel formwork is used to splice the sides of the pedestal, and then the tie rod assembly is used to connect it to the steel frame for precise positioning and fixation. Putty is used to fill and smooth the joints to form the casting model of the pedestal;

[0015] Finally, after the casting model of each pedestal is installed, the plane position and elevation are measured and checked to meet the design and specification requirements, and then concrete is poured into each casting model.

[0016] The above scheme is further preferred, and the layered pouring includes the following steps: first, a 20 cm thick C20 concrete cushion layer is set at the bottom of the pedestal, and then a complete pedestal is poured in layers on the concrete cushion layer, and the top surface of the lower concrete layer should be roughened before pouring the upper concrete layer, and the concrete is laid from the edge of the casting model toward the center. During the laying process, the concrete is vibrated, and the next pouring construction is started after the concrete layer solidifies. The thickness of the layered poured concrete is not less than 35 cm, and the concrete surface is smoothed and pressed at least twice after each layer is poured, and the pouring interval of each layer is controlled within 7 days.

[0017] The above scheme is further preferred, and the chiseling out of the over-filled pile head includes the following steps: first, a 12-20 cm cutting area is planned at the position of the foundation pile head, which is spirally coiled on the outer wall of the pile head; then, a gap is chiseled along the cutting area to a depth to the position of the foundation pile reinforcement, and then the concrete protective layer of the pile head above the gap is peeled off to completely separate the foundation pile reinforcement from the concrete; finally, the reinforcement is bent outward into an arc shape, and the concrete protective layer is chiseled flat until the reinforcement is exposed at the root of the pile head, and then the scattered concrete debris is removed.

[0018] The above scheme is further preferred. In step 2, the soil nails are made of steel bars with a diameter of not less than 16 mm, and the soil nails inserted into the slope are arranged in a plum blossom shape, with a horizontal spacing of not more than 2.0 m and a vertical spacing of not more than 1.5 m. The diameter of the steel bars of the steel mesh is not less than 8 mm and the mesh size is not more than 300 mm × 300 mm.

[0019] The above solution is further preferred in that the bottom anti-cracking mesh is a steel mesh made of φ12 steel bars, and the spacing between the steel bars is more than 10 cm.

[0020] The above solution is further preferred, the thickness of the support pad is not less than 4cm, and the number of support pads arranged is not less than 4 / m 2 , negative deviation of the support pad size is not allowed, and the positive deviation shall not be greater than 5mm.

[0021] The above scheme is further preferred, and the cooling structure includes a cooling pipe assembly 10 arranged and installed along the vertical and horizontal directions along the steel frame of the base and a temperature measuring element arranged in the cooling pipe assembly. The cooling pipe assembly is a pipe formed by welding and enclosing thin steel sheets, and the surface of the thin steel sheet is provided with convex and concave points that are staggered on both sides. The cooling pipe assembly arranged and installed in the horizontal direction is symmetrically provided with a water inlet and a water outlet.

[0022] The above scheme is further preferred, and the cooling pipe assembly includes vertical cooling pipes arranged and installed along the vertical direction inside the base steel frame, and spiral cooling pipes spirally surrounding the base steel frame, and the downwardly adjacent spiral cooling pipes are interconnected through a plurality of vertical cooling pipes, and the spiral cooling pipes on the same plane are respectively equipped with interconnected water inlets, and a water outlet is provided on the spiral cooling pipe on the opposite side of the water inlet.

[0023] The above scheme is further preferred, that the spiral cooling pipe and the vertical cooling pipe are respectively formed by multiple sections of pipes connected in series, each section of the pipe is composed of an outer cooling pipe and an inner cooling pipe sleeved in the outer cooling pipe, a water cooling channel is formed between the outer cooling pipe and the inner cooling pipe, a receiving cavity for placing a temperature measuring element is provided on the inner wall of the inlet end or / and the outlet end of the outer cooling pipe, the inner diameter of the outlet end of the inner cooling pipe is smaller than the inner diameter of the inlet end, a plug joint is provided at the outlet end of the inner cooling pipe, and a transition connection neck is provided between the plug joint and the outlet end of the inner cooling pipe, the inner cooling pipe of each adjacent section of the pipe is plugged into the inlet end of the next section of the inner cooling pipe through the plug joint, and the outlet end of the outer cooling pipe of each adjacent section of the pipe is connected to the inlet end of the next section of the outer cooling pipe by plugging and then welded and sealed.

[0024] In summary, the present invention adopts the above technical solution, and the present invention has the following technical effects:

[0025] (1) The present invention can solve the technical problem of poor geological stability when constructing a foundation on an inclined riverbed or a steep slope, reduce the danger of construction and avoid collapse; when pouring concrete, it can thermally reduce the thermal stress inside the foundation, avoid the risk of cracks, and ensure the structural quality of the concrete foundation structure.

[0026] (2) The present invention uses a cooling structure in which cooling pipes are staggered in vertical and spiral (inclined or horizontal spiral) to control the temperature inside the support. This not only increases the cooling area, but also makes the temperature difference between the surface and the interior of the support not much different. It not only effectively reduces the temperature difference between the inside and the outside, but also prevents and improves the situation where cracks appear on the support. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 It is a construction flow chart of a bridge cap construction method of the present invention;

[0028] Figure 2 This is a construction structure diagram of a bridge cap construction method of the present invention;

[0029] Figure 3 It is a schematic structural diagram of the cooling pipe assembly of the present invention;

[0030] Figure 4 It is an external structural diagram of the cooling pipe of the present invention;

[0031] Figure 5 It is a diagram of the internal structure of the cooling pipe of the present invention;

[0032] In the accompanying drawings, there are a cooling pipe assembly 10, a vertical cooling pipe 10a, a spiral cooling pipe 10b, a temperature measuring element 11, concave and convex points 12, a water inlet 13, a water outlet 14, a receiving cavity 15, an outer cooling pipe 100, an inner cooling pipe 101, a water flow cooling channel 102, a plug connector 103, a neck 104, and a support rib 105. DETAILED DESCRIPTION

[0033] To make the objectives, technical solutions, and advantages of the present invention more clearly understood, the present invention is further described in detail below with reference to the accompanying drawings and by way of preferred embodiments. However, it should be noted that many of the details listed in this specification are merely provided to help the reader gain a thorough understanding of one or more aspects of the present invention, and these aspects of the present invention can be practiced even without these specific details.

[0034] Combine Figure 1 and Figure 2 As shown, according to a bridge pier construction method of the present invention, the pier construction method includes the following steps:

[0035] Step 1: Excavation of the foundation cap. According to the design drawings and on-site geological survey, the foundation cap is excavated around the pile foundation. Two slopes with a slope ratio of at least 1:1 to 1.5 are excavated around the foundation pit. When the excavation reaches the designed pit bottom elevation or the slope boundary, a 20-30 cm thick soil layer is reserved. Then, manual excavation and slope repair are carried out. A drainage ditch is excavated along the excavation edge of the top and bottom of the foundation pit slope. A platform of at least 1-2 m is reserved between the bottom of the slope and the outside of the foundation cap at the bottom of the foundation pit.

[0036] Step 2: Slope protection: The slope surface is leveled, soil nails are inserted, and steel mesh is laid. Then, C20 shotcrete is used for spray anchoring. The soil nails are made of steel bars with a diameter of not less than 16 mm. The soil nails are arranged in a plum blossom shape on the slope, with a horizontal spacing of not more than 2.0 m and a vertical spacing of not more than 1.5 m. The diameter of the steel mesh is not less than 8 mm and the mesh size is not more than 300 mm × 300 mm. The slope surface is protected by soil nail spray anchoring to effectively prevent the slope from collapsing.

[0037] Step 3: Chiseling out the foundation piles. Use a grinding wheel to perform circular cutting at the designed elevation of the foundation pile head to remove the concrete protective layer of the over-filled pile head. Chiseling out the over-filled pile head includes the following steps: first, plan a 12-20cm cutting area at the foundation pile head position, which is spirally coiled around the outer wall of the pile head; then, chisel a gap along the cutting area to the depth of the foundation pile reinforcement position, and then peel off the concrete protective layer of the pile head above the gap to completely separate the foundation pile reinforcement from the concrete; finally, bend the reinforcement outward into an arc shape, and chisel the concrete protective layer flat until the reinforcement is exposed at the root of the pile head, and then remove the scattered concrete debris;

[0038] Step 4: Fabrication of the cap reinforcement skeleton. The fabrication process is as follows: straightening the pile head reinforcement, installing the bottom anti-crack mesh, installing the bottom reinforcement, installing the pile top reinforcement mesh, installing the pile head stirrups, installing the frame reinforcement, installing the top inner reinforcement, installing the side outer reinforcement, installing the top outer reinforcement, installing the tower base embedded reinforcement and the main tower cap frame and pier body embedded segments. After the cap reinforcement skeleton is formed, a cooling structure is installed on the cap reinforcement skeleton. The bottom anti-crack mesh is a steel mesh made of φ12 steel bars, and the steel bar spacing exceeds 10 cm.

[0039] Step 5: Install the casting model. Place the prepared cap reinforcement skeleton at the planned location in the cap pit foundation. Then, mark the reference lines for the construction and installation template along the four sides of the cap reinforcement skeleton. Install the casting model corresponding to the cap structure according to the reference lines. Casting the model includes the following steps:

[0040] First, before installation, clean the stains on the template and set support pads at the bottom and both sides of the frame. The thickness of the support pads should be no less than 4cm, and the number of support pads should be no less than 4 / m 2 , the size of the supporting pad is not allowed to have a negative deviation, and the positive deviation shall not be greater than 5mm; then, the formwork is installed on the upper and lower sides of the pedestal respectively, and the verticality and plane position of the formwork are adjusted so that the horizontal and vertical directions are in a straight line, and the formwork is then connected to the steel bars of the foundation pile through the embedded steel bars so that the formwork is engaged in the foundation pit; secondly, standard steel formwork is used to splice on the side of the pedestal, and then the tie rod assembly is used to connect it to the steel skeleton for precise positioning and fixation, and putty is used to fill and smooth the joints to form the casting model of the pedestal; finally, after the casting model of each pedestal is installed, the plane position and elevation are measured and checked to meet the design and specification requirements, and then concrete is poured in each casting model;

[0041] Step 6: Concrete pouring and curing. The central main tower pedestal adopts C35 concrete, and the other auxiliary piers and transition pier pedestals adopt C30 concrete. They are poured in layers in the formwork. The pouring thickness of each layer is not less than 35cm. When a layer of concrete is poured, cooling water is gradually fed into the cooling structure, and the cooling water flow rate is increased every 30s-60s. According to the temperature difference between the water inlet position, middle position and water outlet position of the cooling structure, the cooling water flow rate is adjusted and the water flow time is increased, thereby increasing and accelerating the cooling effect of the cooling water in the internal structure of the pedestal. According to the temperature difference between the water inlet position, middle position and water outlet position of the cooling structure and the external temperature of the pedestal, the temperature of the cooling water is adjusted, thereby reducing the influence of temperature changes inside and outside the pedestal, which leads to changes in the pedestal structure, thereby reducing the thermal stress inside the pedestal and avoiding the occurrence of cracks. The risk of gaps is eliminated to ensure the structural quality of the concrete cap structure; after the cap is poured as a whole and solidified, the cooling water is withdrawn, and then the formwork is removed after curing until the concrete reaches the required strength; the layered pouring is carried out as follows: first, a 20cm thick C20 concrete cushion is laid at the bottom of the cap, and then the complete cap is poured layer by layer on top of the concrete cushion. The width of the concrete cushion is larger than the width of the cap. Before pouring the upper layer of concrete, the top surface of the lower layer of concrete should be roughened to make the concrete surface cleaner. The concrete is spread from the edge of the casting model toward the center. The concrete is vibrated during the spreading process. The next pouring construction is carried out after the concrete layer solidifies. The thickness of the layered concrete is not less than 35cm. After each layer is poured, the concrete surface is smeared and pressed at least twice, and the pouring interval of each layer is controlled within 7 days;

[0042] Step 7: After the foundation pile maintenance is completed, the foundation pit should be backfilled with excavated soil in time. Before the pier body is constructed, the backfill soil of the foundation pit should be no more than 30 cm lower than the foundation pile, and drainage ditches should be excavated around the foundation pile to allow rainwater to be discharged in a targeted manner to prevent the top surface of the foundation pile from being contaminated by mud and debris.

[0043] In the present invention, Figure 3 、 Figure 4 and Figure 5As shown, the cooling structure includes a cooling pipe assembly 10 arranged and installed along the vertical and horizontal directions inside the base steel frame and a temperature measuring element 11 arranged in the cooling pipe assembly 10. The cooling pipe assembly 10 is a pipe formed by welding thin steel sheets, and the surface of the thin steel sheets is provided with concave and convex points 12 that are staggered on both sides. After the thin steel sheets are enclosed and welded to form the pipe, the thin steel sheets are also coated with a zinc protective layer, and concave and convex points 12 are formed inside and outside the pipe, so that when the cooling water flows in the pipe, the contact area is not only increased, but also the cooling water forms an undulating disturbance during the flow process, thereby changing the water flow state. The cooling pipe assembly 10 arranged and installed in the horizontal direction is symmetrically provided with a water inlet 13 and a water outlet 14; in the present invention, the cooling pipe assembly 10 includes a pipe arranged and installed along the vertical direction inside the base steel frame. The vertical cooling pipes 10a are arranged and installed, and the spiral cooling pipes 10b are spirally wound around the steel frame of the foundation. The downwardly adjacent spiral cooling pipes 10b are interconnected through several vertical cooling pipes 10a. The spiral cooling pipes 10b on the same plane are respectively installed with interconnected water inlets 13, and the spiral cooling pipes 10b on the opposite side of the water inlet 13 are provided with a water outlet 14. When each layer of concrete is poured, cooling water is sent into the water inlet 13 of the topmost spiral cooling pipe 10b in each layer of concrete, and then it is diverted to the vertical cooling pipes 10a and other spiral cooling pipes, and then discharged from the water outlet 14 of the bottommost spiral cooling pipe 10b. During the circuitous flow of cooling water in the cooling pipe, the temperature inside the cooling concrete foundation is adjusted until the concrete foundation is completely solidified.

[0044] In the present invention, Figure 3 、 Figure 4 and Figure 5As shown, the spiral cooling pipe 10b and the vertical cooling pipe 10a are respectively composed of multiple sections of pipes connected in series, each section of the pipe is composed of an outer cooling pipe 100 and an inner cooling pipe 101 arranged in the outer cooling pipe 100, and a water flow cooling channel 102 is formed between the outer cooling pipe 100 and the inner cooling pipe 101. The cooling water exchanges heat with the internal structure of the base through the water flow cooling channel 102 inside the outer cooling pipe 100, thereby achieving the effect of cooling the inside of the base. Support ribs 104 are connected to the side wall between the outer cooling pipe 100 and the inner cooling pipe 101, and a receiving cavity 15 for placing a temperature measuring element 11 is provided on the inner wall of the inlet end or / and the outlet end of the outer cooling pipe 100. The temperature measuring element 11 can be conveniently installed in the receiving cavity 15. When each layer of concrete is poured, multiple outlet ends can be provided on the outer cooling pipe 100 to allow cooling water to flow from the water outlet 101 of the outer cooling pipe 100 of the spiral cooling pipe 10b. 4 is discharged, and the temperature change after the cooling water and the concrete are heat exchanged can be detected by the temperature measuring element 11, so as to measure the temperature change of the concrete foundation. In the present invention, the inner diameter of the outlet end of the inner cooling pipe 101 is smaller than the inner diameter of the inlet end. A plug connector 103 is provided at the outlet end of the inner cooling pipe 101, and a transitional neck 104 is provided between the plug connector 103 and the outlet end of the inner cooling pipe 101. The neck 104 can block the cooling water flowing out of the inner cooling pipe 101 to a certain extent, so that the cooling water inside the inner cooling pipe 101 has a longer time to exchange heat with the cooling water inside the outer cooling pipe 100, slowing down the temperature rise speed of the cooling water inside the outer cooling pipe 100, so that the cooling water inside the outer cooling pipe 100 and the interior of the foundation can fully absorb heat to complete the heat exchange, thereby improving the utilization rate of the coolant; the cooling effect can be fully exerted, and the circulation amount of the cooling water is greatly reduced.

[0045] In the present invention, Figure 3 、 Figure 4 and Figure 5As shown, the inner cooling pipe 101 of each adjacent pipe section is plugged into the inlet end of the inner cooling pipe 101 of the next section through the plug connector 103, and the outlet end of the outer cooling pipe 100 of each adjacent pipe section is connected to the inlet end of the outer cooling pipe 100 of the next section by plugging and then welding and sealing, so that the inner cooling pipe 101 and the outer cooling pipe 100 are always isolated. At the last water outlet 14, the water in the inner cooling pipe 101 and the water in the outer cooling pipe 100 are mixed and discharged. The discharged water is cooled and then sent to the water inlet 13 again to cool the concrete foundation. When there is a large temperature difference between the concrete pedestal structure near the water inlet 13 and the concrete pedestal structure near the water outlet, the temperature difference between the concrete pedestal near the water inlet of the cooling pipe and the concrete pedestal near the water outlet can be reduced by changing the water inlet and water outlet directions of the cooling water; when the outer cooling pipe 100 of the spiral cooling pipe 10b or the outer cooling pipe of the vertical cooling pipe 10a is respectively diverted to the inner cooling pipe 101, the outlet end of the inner cooling pipe 101 is relatively small, so that the cooling water inside the inner cooling pipe 101 is blocked by the neck 104 during the flow process, reducing the flow speed of the cooling water inside the inner cooling pipe 101 and improving the heat exchange effect. The cooling water in the inner cooling pipe 101 can exchange heat with the cooling water with a higher temperature in the outer cooling pipe 100; the cooling water entering the inner cooling pipe 101 During the heat exchange process between water and the water in the external cooling pipe 100, the temperature of the cooling water in the external cooling pipe 100 increases more slowly, and the cooling water in the external cooling pipe 100 can maintain a relatively slow change for a long time, thereby improving the cooling effect of the concrete foundation. At the same time, the temperatures at the positions of the concave and convex points 12 on the internal cooling pipe 101 and the external cooling pipe 100 are also different, which can enable the concave and convex points 12 with higher temperatures to exchange heat with the concave and convex points 12 with lower temperatures, so that the cooling water in the entire cooling assembly can achieve a balanced change, reducing the changes in the internal structure of the foundation due to thermal shrinkage stress changes, and effectively improving the cooling effect of the foundation; when the heat generation is small or the cooling requirements are low, 1-2 water inlets 13 can be opened to feed in cooling water and 1-2 water outlets 14 can be opened to discharge cooling water. The data of the temperature measuring element 11 is connected to the information management platform through a wire to monitor in real time the key temperature control indicators such as the water temperature of the cooling pipe, the core temperature and surface temperature of the pedestal, the cooling rate, and the ambient temperature. Through convenient, information-based, and data-based means, management personnel can control the changes in temperature control indicators during the pedestal casting process in real time. Once the set threshold is exceeded, the platform can immediately send an early warning message to the relevant management personnel so that timely measures can be taken to deal with it.

[0046] The above is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principles of the present invention. These improvements and modifications should also be regarded as within the scope of protection of the present invention.

Claims

1. A bridge cap construction method, characterized in that: The foundation construction method comprises the following steps: Step 1: Excavation of the foundation of the cap pit. According to the design drawings and on-site geological survey, the foundation of the cap pit is excavated outside the pile foundation. Two slopes of at least 1:1 to 1.5 are excavated around the foundation pit. When the excavation is close to the designed pit bottom elevation or the slope boundary, a 20-30 cm thick soil layer is reserved. Then, manual excavation and slope repair are carried out, and a drainage ditch is excavated along the excavation edge line at the top and bottom of the foundation pit slope. At least a 1m to 2m platform is reserved between the bottom of the slope and the outside of the cap at the bottom of the foundation pit; Step 2: Slope protection: Slope leveling, soil nailing, steel mesh laying, and then C20 shotcrete anchoring; Step 3: Remove the foundation piles. Use a grinder to perform circular cutting at the designed elevation of the foundation pile head to remove the concrete protective layer of the over-filled pile head. Step 4: Fabrication of the steel frame of the cap, the manufacturing process is as follows: straightening the steel bars at the pile head, installing the bottom anti-crack mesh, installing the bottom steel bars, installing the steel mesh at the pile top, installing the pile head stirrups, installing the frame reinforcement, installing the inner steel bars at the top layer, installing the outer steel bars at the side, installing the outer steel bars at the top layer, installing the embedded steel bars at the tower base and the embedded segments of the main tower cap frame and pier body, after the steel frame of the cap is formed, a cooling structure is installed on the steel frame of the cap; Step 5: Installation of casting model: Place the prepared cap steel frame at the planned position in the cap pit foundation, and then draw the reference line of the construction and installation template along the four sides of the cap steel frame, and install the casting model corresponding to the cap structure according to the reference line; Step 6: Concrete pouring and curing. The central main tower cap uses C35 concrete, and the other auxiliary piers and transition pier caps use C30 concrete. They are poured layer by layer in the formwork. The pouring thickness of each layer is not less than 35cm. When a layer of concrete is poured, cooling water is gradually introduced into the cooling structure. The cooling water flow rate is increased every 30s-60s. After the cap is poured as a whole and solidified, the cooling water is withdrawn. Then, the formwork is removed after curing until the concrete reaches the required strength. Step 7: Backfill and drainage. After the maintenance of the foundation is completed, the foundation pit should be backfilled with excavated soil in time. Before the pier body is constructed, the backfill soil of the foundation pit should be no more than 30cm lower than the foundation, and drainage ditches should be excavated around the foundation to allow rainwater to be discharged in a directional manner.

2. A bridge cap construction method according to claim 1, characterized in that: Installing the pouring model corresponding to the cap structure according to the reference line includes the following steps: First, before installation, remove the stains on the formwork and set support pads at the bottom and both sides of the frame. Install the formwork on the upper and lower sides of the pedestal respectively, adjust the verticality and plane position of the formwork so that it is in a straight line horizontally and vertically, and then connect the formwork to the steel bars of the foundation piles through pre-buried steel bars so that the formwork is engaged in the foundation pit; Secondly, standard steel formwork is used to splice the sides of the cap, and then the tie rod assembly is used to connect to the steel frame for precise positioning and fixing, and putty is used to fill and smooth the joints to form a casting model of the cap; Finally, after the casting model of each pedestal is installed, the plane position and elevation are measured and verified to meet the design and specification requirements, and then concrete is poured in each casting model.

3. A bridge cap construction method according to claim 1, characterized in that: The layered pouring includes the following steps: firstly, a 20cm thick C20 concrete cushion layer is set at the bottom of the pedestal, and then a complete pedestal is formed by layered pouring on the concrete cushion layer; before pouring the upper layer of concrete, the top surface of the lower layer of concrete should be roughened, and the material is spread from the edge of the casting model toward the center; during the spreading process, the concrete is vibrated, and the next pouring construction is started after the concrete layer solidifies; wherein, the thickness of the layered poured concrete is not less than 35cm, and the concrete surface is smoothed and pressed at least twice after each layer is poured, and the pouring interval of each layer is controlled within 7 days.

4. A bridge cap construction method according to claim 1, characterized in that: Chiseling out the over-filled pile head includes the following steps: first, plan a 12-20cm cutting area at the position of the pile head, which is spirally coiled around the outer wall of the pile head; then, chisel a gap along the cutting area to the depth of the pile reinforcement position, and then peel off the concrete protective layer of the pile head above the gap, so that the pile reinforcement is completely separated from the concrete; finally, bend the reinforcement outward into an arc, chisel the concrete protective layer until the reinforcement is exposed at the root of the pile head, and then remove the scattered concrete debris.

5. A bridge cap construction method according to claim 1, characterized in that: In step 2, the soil nails are made of steel bars with a diameter of not less than 16 mm, and the soil nails inserted into the slope are arranged in a plum blossom shape, with a horizontal spacing of not more than 2.0 m and a vertical spacing of not more than 1.5 m. The diameter of the steel bars of the steel mesh is not less than 8 mm and the mesh size is not more than 300 mm×300 mm.

6. A bridge cap construction method according to claim 1, characterized in that: The bottom layer anti-cracking mesh is a steel mesh made of φ12 steel bars with a spacing of more than 10cm.

7. A bridge cap construction method according to claim 1, characterized in that: The thickness of the support pad shall not be less than 4cm, and the number of support pads shall not be less than 4 / m 2 , negative deviation of the support pad size is not allowed, and the positive deviation shall not be greater than 5mm.

8. A bridge cap construction method according to claim 1, characterized in that: The cooling structure includes a cooling pipe assembly 10 arranged and installed along the vertical and horizontal directions inside the steel frame of the base and a temperature measuring element arranged in the cooling pipe assembly. The cooling pipe assembly is a pipe formed by welding and enclosing thin steel sheets, and the surface of the thin steel sheets is provided with convex and concave points that are staggered on both sides. The cooling pipe assembly arranged and installed in the horizontal direction is symmetrically provided with water inlets and outlets.

9. A bridge cap construction method according to claim 8, characterized in that: The cooling pipe assembly includes vertical cooling pipes arranged and installed along the vertical direction inside the steel frame of the pedestal, and spiral cooling pipes spirally surrounding the steel frame of the pedestal. The spiral cooling pipes adjacent to each other downward are interconnected through a plurality of vertical cooling pipes. The spiral cooling pipes on the same plane are respectively equipped with interconnected water inlets, and water outlets are provided on the spiral cooling pipes on the opposite side of the water inlets.

10. A bridge cap construction method according to claim 9, characterized in that: The spiral cooling pipe and the vertical cooling pipe are respectively formed by multiple sections of pipes connected in series, each section of the pipe is composed of an outer cooling pipe and an inner cooling pipe sleeved in the outer cooling pipe, a water cooling channel is formed between the outer cooling pipe and the inner cooling pipe, a receiving cavity for placing a temperature measuring element is arranged on the inner wall of the inlet end or / and the outlet end of the outer cooling pipe, the inner diameter of the outlet end of the inner cooling pipe is smaller than the inner diameter of the inlet end, a plug joint is arranged at the outlet end of the inner cooling pipe, and a transition connection neck is provided between the plug joint and the outlet end of the inner cooling pipe, the inner cooling pipe of each adjacent section of the pipe is plugged into the inlet end of the next section of the inner cooling pipe through the plug joint, and the outlet end of the outer cooling pipe of each adjacent section of the pipe is connected to the inlet end of the next section of the outer cooling pipe by plugging and then welded and sealed.

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