Arched low-pier continuous beam bridge foundation and construction method

Abstract

The present invention discloses an arched low-pier continuous beam bridge foundation and construction method, which is applicable to the field of bridge pile foundation construction. The arched low-pier continuous beam bridge foundation of the present invention includes a continuous beam body and a plurality of bridge piers. The plurality of bridge piers are arranged below the continuous beam body and support the continuous beam body. The plurality of bridge piers include two main piers, each of which is supported by a pedestal, and a pile foundation structure is arranged below the pedestal. The main piers are low curved piers, and the cross-section of the low curved piers gradually increases from the pedestal to the bottom of the continuous beam body. When calculating the pull-out force of the main pier pedestal and pile foundation, the amplification effect of the low curved piers on the pull-out force of the pedestal and pile foundation due to the greater rigidity of the main pier structure should be considered. The aspect ratio e is set as the pull-out force influence coefficient characterized by its rigidity. The present invention takes the maximum aspect ratio to estimate the pull-out force design requirement of the corresponding pile foundation. Under the action of external force, the low curved piers of the continuous beam pile foundation can well withstand the upward pull-out force.

Description

Technical Field

[0001] The present invention relates to the technical field of bridge construction, and in particular to an arched low-pier continuous beam bridge foundation and a construction method. Background Art

[0002] The structure of Liuxi River Bridge is designed as a low-pier arch continuous beam bridge due to the design requirements of municipal engineering landscaping and to control the transition distance of the approach bridges at both ends of the bridge as much as possible. Compared with traditional high-pier bridges, for low-pier continuous beam bridge structures, the lower the main pier height and the larger the cross-section, the greater its rigidity, and the stronger the tensile force transmitted from the main pier to the pier and its pile foundation under the action of external force. Therefore, the low pier height of Liuxi River Bridge leads to greater column pier stiffness, and the design of its pier and pile foundation also needs to be fully considered. Attention should be paid to strengthening the seismic and pull-out resistance of the pier and pile foundation to ensure the structural stability and safety of the bridge.

[0003] This application is based on the construction of pile foundations for the main piers of the Liuxi River Bridge. The site of the Liuxi River Bridge reveals that the Carboniferous bedrock is mainly limestone, which is a typical karst geological area with strongly developed caves and complex dissolution fissures. The difficulty of large-diameter pile foundation construction in such a complex and changeable karst area is self-evident. The pile foundation construction of the beaded caves in the karst area has always been the focus and difficulty of pile foundation construction in the karst area. The pile foundation construction of the cave is unpredictable and dangerous. Compared with the traditional pile foundation construction, more attention should be paid to the bearing capacity of the pile foundation to ensure the overall bearing capacity of the highway or bridge and avoid settlement problems in the later period. If the cave treatment method is improper, it will often cause accidents such as drill drop, hammer jam, hammer burial, slurry leakage, hole collapse, and pile breakage, and even seriously affect the structural safety of the bridge.

[0004] In order to solve the above problems, this application makes improvements to the pile foundation structure. It not only makes a quantitative estimate of the pull-out resistance demand of the pile foundation of low-pier continuous bridges to meet the pull-out resistance requirements, but also ensures the reliability of the pile foundation structure by setting up a casing device during construction in karst areas. Summary of the Invention

[0005] The purpose of the present invention is to provide an arched low-pier continuous beam bridge and a construction method, which sets low curved piers and sets double-layer steel bars in the pile foundation structure, so as to ensure that the continuous bridge pile foundation structure can well withstand the pulling force under the action of external force.

[0006] To achieve the above object, the present invention provides the following technical solutions:

[0007] An arched low-pier continuous beam bridge foundation, comprising a continuous beam body and a plurality of piers, wherein the continuous beam body is an arched variable-section continuous beam structure, the plurality of piers being arranged below the continuous beam body and supporting the continuous beam body, the plurality of piers including two main piers, each of the main piers supporting the main pier via a cap, a pile foundation structure being arranged below the cap, the pile foundation structure being provided with a casing and a steel cage, the casing being sleeved outside the steel cage and fixedly connected to the steel cage;

[0008] The main pier is a low curved pier, and the cross section of the low curved pier gradually increases from the pier cap to the bottom of the continuous beam body. When designing the seismic and wind-resistant structure of the main pier cap and pile foundation, that is, when performing pull-out force design calculations, the amplification effect of the low curved pier on the pull-out force of the pier cap and pile foundation due to the greater rigidity of the main pier structure should be considered, and the aspect ratio e is set as follows:

[0009] e=a / h

[0010] Where a is the side length or diameter of the main pier cross section, and h is the height of the main pier body;

[0011] According to the above formula, the design pull-out force of the cap or pile foundation is as follows:

[0012] f 设 =f 计 * (1 + e)

[0013] where f 设 is the design pull-out force of the cap or pile foundation, where f 计 Calculated pull-out force for the main pier;

[0014] For low curved piers, the aspect ratio e is selected as the coefficient of influence of the pull-out force caused by its rigidity.

[0015] As the preferred technical solution of the present invention, the maximum aspect ratio of the main pier is taken as max As the influence coefficient, it is used to estimate the pull-out resistance design requirement of the corresponding pile foundation, that is, the maximum flatness ratio a max Take the side length or diameter of the largest main pier cross section.

[0016] As a preferred technical solution of the present invention, the cross section of the main pier is circular, and the aspect ratio a is the diameter of the circle; the cross section of the main pier is square, and the aspect ratio a is the longest side of the square.

[0017] As a preferred technical solution of the present invention, the main pier is divided into an upper main pier and a lower main pier by the pier body dividing line. The lower main pier is the inclined portion from the pier base elevation to the pier body dividing line; the upper main pier is the curved portion from the pier body dividing line to the bottom of the continuous beam body. The external shape of the main pier is similar to the vase-shaped pier body with an upward opening, which ensures aesthetics, a low pier body, and sufficient bearing capacity.

[0018] As an optimal technical solution of the present invention, a steel cage with double-layer steel bars is provided in the pile foundation structure, and the outer main bars of the steel cage are formed by a plurality of long bars and a plurality of short bars arranged radially at intervals. The outer wall of the outer main bars is welded and fixed by spiral bars, and the inner wall of the outer main bars is provided with an outer reinforcing hoop and fixed by welding. The inner main bars of the steel cage are formed by a plurality of steel bars and are arranged on the inner side of the outer main bars. A reinforcing hoop is provided on the inner wall of the inner main bars every several meters, and an inner triangular support is provided on the reinforcing hoop, and the inner triangular supports are aligned from top to bottom in the same plane position along the length of the pile; the spiral bars are composed of two sections of spiral bar units with different pitches, and the pitch of the second section of the spiral bar unit is twice the pitch of the first section of the spiral bar unit; positioning bars are provided around the outer and inner reinforcing hoops, with a group provided every several meters, and each group is provided with a plurality of positioning bars.

[0019] Further preferably, the steel cage is formed by welding, and the reinforcing hoops are double-sided welded; the steel bars of the steel cage are all HRB400 steel bars.

[0020] The present invention provides a construction method for an arched low-pier continuous beam bridge foundation, including a construction method for a pile foundation structure, which specifically comprises the following steps:

[0021] S1. Construction preparation: Measure the vertical and horizontal coordinates and span coordinates to determine the pile position; then conduct geological drilling to determine the designed pile length; finally, survey the practical site within the pile foundation construction range to determine the bridge pile foundation construction surface;

[0022] S2. Drilling platform erection: The drilling platform uses a steel pipe pile foundation, and the upper structure uses Bailey beams as the upper load-bearing structure. I-beams and steel plates are laid on top of the load-bearing structure as the bridge deck structure. The steel pipe piles are driven in with a vibratory hammer. After the driving is completed, the upper structure and steel panels are installed.

[0023] S3. Burying of hole casing: After the drilling platform is erected, a guide device is installed on the top of the platform, and the hole casing is pre-buried using a pile hammer. The casing is required to penetrate the strongly weathered rock by no less than 50 cm. At the same time, the burial of the hole casing must ensure that the deviation between the center of the top surface of the hole casing and the designed pile position is no more than 5 cm, and the inclination is no more than 1 / 200 (0.5%), so as to meet the process requirements of the follow-up of the inner casing and the protective net when treating the cave in the next step.

[0024] S4. Inner casing follow-up and cave treatment: In the center of the buried casing, the inner casing is used to follow up the cave in the karst area. After the inner casing is buried, the pile hammer is replaced and continued to drive. The cave is backfilled with a three-phase mixture of stone, clay and bagged cement in the weight ratio of 6.5:3:0.5.

[0025] S5. Fabrication and installation of steel cage: The steel cage is fabricated in sections at the steel processing plant. For each section of the steel cage, the outer main reinforcement is first installed, followed by the outer reinforcing hoops; then the inner main reinforcement is installed, followed by the inner reinforcing hoops; finally, the inner triangular bracing, spiral reinforcement and positioning reinforcement are installed;

[0026] The designed cage length of the pile foundation reinforcement cage is adjusted according to the pile length. The reinforcement cage is manufactured in sections with a standard section length of 12~13m. The top cage and the middle cage are both standard sections, and the bottom cage is an adjustable section. The processed double-layer reinforcement cage is transported to the site for installation and docking. It is lowered to the pile foundation hole by a crane, and lowered vertically along the inner wall of the casing. The three sections of the reinforcement cage are matched and connected to the main reinforcement through straight threaded sleeves. The number of main reinforcement joints in the same connection section shall not exceed 50%, and the spacing between adjacent joints shall be 35d and not less than 500mm. Finally, the docked reinforcement cage is placed in the pile foundation hole.

[0027] S6. Underwater concrete pouring: Pour the pile body concrete into the pile foundation hole to complete the pile foundation construction.

[0028] As the preferred technical solution of the present invention, the guide device described in step S3 of the pile foundation structure construction method is provided with two layers in total, and the first layer of the guide device is fixed to the top surface of the platform; the second layer of the guide device is provided using the platform steel pipe piles, that is, the corbels are welded on the steel pipe piles, and I25a I-beams are laid on the corbels and welded to the corbels. When installing the second layer of the guide device, a hanging hammer ball method is required to ensure that the two layers of guide frames are perpendicular to each other; the positioning of the open hole casing is achieved by setting large diameter bolts in the center of the four sides of the guide device, and the screws and nuts are welded and locked, and the edge of each screw is 10 mm away from the designed position of the outer edge of the casing.

[0029] As the preferred technical solution of the present invention, in step S5 of the pile foundation structure construction method, the main reinforcement is placed on a semicircular mounting platform, and after the main reinforcement is installed, the reinforcing hoops are placed, the verticality of the reinforcing hoops and the main reinforcement is corrected, and then they are spot welded and fixed; after the main reinforcement is arranged, the spiral reinforcement is placed, and the spiral reinforcement is inserted into the main reinforcement in sections according to the designed spacing and spot welded on the main reinforcement, and the positioning reinforcement is welded on the main reinforcement in the length direction of the steel cage, and the positioning reinforcement corresponds to the reinforcing hoops and is arranged equidistantly along the circumference according to the design requirements.

[0030] In summary, compared with the prior art, the beneficial effects of the present invention are as follows: the bridge of the present invention is a three-span continuous beam, the main body of the continuous beam is a variable-section continuous beam structure, and the three-span continuous beam is supported by two low curved piers. Regarding the variable-section low curved pier, when designing and calculating the pull-out force of the main pier cap and pile foundation, in order to consider the amplified effect of the low curved pier on the pull-out force of the cap and pile foundation due to the greater rigidity of the main pier structure, the aspect ratio formula is introduced. The ratio of the side length or diameter of the main pier cross section to the height of the main pier body is used as the pull-out force influence coefficient caused by its rigidity. a takes the side length or diameter of the maximum main pier cross section, that is, the connection between the continuous beam main body and the main pier is the maximum main pier cross section. The pull-out force borne at the maximum main pier cross section is the largest. When the corresponding main pier maximum aspect ratio e is taken max As an influence coefficient, the pull-out force design requirement of the corresponding pile foundation can be estimated, while ensuring that the pull-out force design requirement of the pile foundation is within the safety value, thereby improving the reliability and stability of the entire main pier foundation's seismic and wind-resistant structure. Therefore, the low curved pier can withstand the upward pulling force generated by the vibration of the three-span continuous beam.

[0031] To further improve the pullout resistance of the low-profile curved piers, a double-layer steel cage is installed within the pile foundation structure. The double-layer steel reinforces the low-profile curved piers' load-bearing capacity, enabling them to withstand the upward pullout forces generated during bridge vibration. The outer main reinforcement, with short and long bars spaced circumferentially along the cage, enhances the concrete column's resistance to lateral displacement and torsional to improve its overall stability. This arrangement ensures the safety and reliability of the low-profile curved piers during bridge vibration. Furthermore, the use of low-profile curved piers can reduce traffic disruption and improve road efficiency. Compared to other high-profile pier designs, the arched low-pier continuous beam bridge of the present invention is not only aesthetically pleasing, but also offers advantages such as lower cost and reduced construction difficulty. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] Figure 1 Schematic diagram of the elevation structure of the arched low-pier continuous beam bridge of the present invention;

[0033] Figure 2 This is a schematic diagram of the main pier structure of the arched low-pier continuous beam bridge of the present invention;

[0034] Figure 3 The cross section of the double-layer steel cage in the pile foundation structure of the arched low-pier continuous beam bridge of the present invention;

[0035] Figure 4 This is a flow chart of a pile foundation structure construction method for an arched low-pier continuous beam bridge according to the present invention;

[0036] In the figure: 1- continuous beam body, 2- main pier, 21- lower main pier, 22- upper main pier, 3- pile foundation structure, 4- pedestal, 5- spiral reinforcement, 6- stiffening hoop, 61- inner stiffening hoop, 62- outer stiffening hoop, 7- inner triangular support, 81- short reinforcement, 82- long reinforcement, 9- inner main reinforcement. DETAILED DESCRIPTION

[0037] The following is a further description of specific embodiments of the present invention in conjunction with the accompanying drawings. It should be noted that the description of these embodiments is intended to facilitate understanding of the present invention and does not constitute a limitation of the present invention. In addition, the technical features involved in the various embodiments of the present invention described below may be combined with each other as long as they do not conflict with each other.

[0038] like Figures 1 to 4 As shown, an arched low-pier continuous beam bridge foundation includes a continuous beam body 1 and several piers. The continuous beam body 1 is an arched variable-section continuous beam structure. The several piers are arranged below the continuous beam body 1 and support the continuous beam body 1. The several piers include two main piers 2, each of which supports the main pier 2 through a cap. A pile foundation structure 3 is provided under the cap 4. The pile foundation structure 3 is provided with a casing and a steel cage. The casing is sleeved outside the steel cage and fixedly connected to the steel cage.

[0039] The main pier 2 is a low curved pier, and the cross section of the low curved pier gradually increases from the pedestal 4 to the bottom of the continuous beam body 1. When designing the seismic and wind-resistant structure of the pedestal 4 and the pile foundation of the main pier 2, that is, when performing the pull-out force design calculation, the amplification effect of the low curved pier on the pull-out force of the pedestal and pile foundation due to the greater structural rigidity of the main pier 2 should be considered, and the aspect ratio e is set as follows:

[0040] e=a / h

[0041] Where a is the side length or diameter of the cross section of the main pier 2, and h is the height of the main pier 2;

[0042] According to the above formula, the design pull-out force of the cap or pile foundation is as follows:

[0043] f 设 =f 计 * (1 + e)

[0044] where f 设 is the design pull-out force of the cap or pile foundation, where f 计 Calculated pull-out force for the main pier;

[0045] For low curved piers, the aspect ratio e is selected as the coefficient of influence of the pull-out force caused by its rigidity.

[0046] The preferred implementation of this embodiment corresponds to the maximum aspect ratio e of the main pier 2. max As the influence coefficient, it is used to estimate the pull-out resistance design requirement of the corresponding pile foundation, that is, the maximum flatness ratio a max Take the side length or diameter of the largest main pier cross section.

[0047] In a preferred implementation of this embodiment, the cross section of the main pier 2 is circular, and the aspect ratio a is the diameter of the circle; the cross section of the main pier 2 is square, and the aspect ratio a is the longest side of the square.

[0048] The preferred implementation of this embodiment is as follows Figure 2 As shown, the main pier 2 is divided into two sections, an upper main pier 22 and a lower main pier 21, by the pier body dividing line. The lower main pier 21 is the inclined part from the elevation of the pedestal 4 to the pier body dividing line; the upper main pier 22 is the curved part from the pier body dividing line to the bottom of the continuous beam body 1.

[0049] The preferred implementation of this embodiment is as follows Figure 3 As shown, a double-layer steel bar cage is provided in the pile foundation structure 3. The outer main reinforcement of the steel cage is formed by a plurality of long bars 82 and a plurality of short bars 81 arranged radially at intervals. The outer wall of the outer main reinforcement is welded and fixed by spiral bars 5. The inner wall of the outer main reinforcement is provided with an outer reinforcing hoop 62 and fixed by welding. The inner main reinforcement 9 of the steel cage is surrounded by a plurality of steel bars and is arranged on the inner side of the outer main reinforcement. An inner reinforcing hoop 61 is provided every several meters on the inner wall of the inner main reinforcement 9. An inner triangular support 7 is provided on the inner reinforcing hoop 61. The inner triangular support 7 is aligned from top to bottom along the length of the pile in the same plane position; the spiral reinforcement 5 is composed of two sections of spiral reinforcement 5 units with different pitches, and the pitch of the second section of the spiral reinforcement 5 unit is twice the pitch of the first section of the spiral reinforcement 5 unit; positioning bars are provided around the outer and inner reinforcing hoops 6, with a group provided every several meters and a plurality of positioning bars arranged in each group.

[0050] Further preferably, the steel cage is formed by welding, and the reinforcing hoop 6 is double-sided welded; the steel bars of the steel cage are all HRB400 steel bars.

[0051] This embodiment provides a construction method for an arched low-pier continuous beam bridge foundation, including a construction method for a pile foundation structure, specifically comprising the following steps:

[0052] S1. Construction preparation: Measure the vertical and horizontal coordinates and span coordinates to determine the pile position; then conduct geological drilling to determine the designed pile length; finally, survey the practical site within the pile foundation construction range to determine the bridge pile foundation construction surface;

[0053] S2. Drilling platform erection: The drilling platform uses a steel pipe pile foundation, and the upper structure uses Bailey beams as the upper load-bearing structure. I-beams and steel plates are laid on top of the load-bearing structure as the bridge deck structure. The steel pipe piles are driven in with a vibratory hammer. After the driving is completed, the upper structure and steel panels are installed.

[0054] S3. Burying of hole casing: After the drilling platform is erected, a guide device is installed on the top of the platform, and the hole casing is pre-buried using a pile hammer. The casing is required to penetrate the strongly weathered rock by no less than 50 cm. At the same time, the burial of the hole casing must ensure that the deviation between the center of the top surface of the hole casing and the designed pile position is no more than 5 cm, and the inclination is no more than 1 / 200 (0.5%), so as to meet the process requirements of the follow-up of the inner casing and the protective net when treating the cave in the next step.

[0055] S4. Inner casing follow-up and cave treatment: In the center of the buried casing, the inner casing is used to follow up the cave in the karst area. After the inner casing is buried, the pile hammer is replaced and continued to drive. The cave is backfilled with a three-phase mixture of stone, clay and bagged cement in the weight ratio of 6.5:3:0.5.

[0056] S5. Fabrication and installation of steel cage: The steel cage is fabricated in sections at the steel processing plant. Each section of the steel cage is first installed with the outer main reinforcement, followed by the outer reinforcing hoop 62; then the inner main reinforcement 9 is installed, followed by the inner reinforcing hoop 61; finally, the inner triangular brace 7, spiral reinforcement 5 and positioning reinforcement are installed;

[0057] The designed cage length of the pile foundation reinforcement cage is adjusted according to the pile length. The reinforcement cage is manufactured in sections with a standard section length of 12~13m. The top cage and the middle cage are both standard sections, and the bottom cage is an adjustable section. The processed double-layer reinforcement cage is transported to the site for installation and docking. It is lowered to the pile foundation hole by a crane, and lowered vertically along the inner wall of the casing. The three sections of the reinforcement cage are matched and connected to the main reinforcement through straight threaded sleeves. The number of main reinforcement joints in the same connection section shall not exceed 50%, and the spacing between adjacent joints shall be 35d and not less than 500mm. Finally, the docked reinforcement cage is placed in the pile foundation hole.

[0058] S6. Underwater concrete pouring: Pour the pile body concrete into the pile foundation hole to complete the pile foundation construction.

[0059] In a preferred implementation manner of this embodiment, the guide device described in step S3 of the pile foundation structure construction method is provided with two layers in total, and the first layer of the guide device is fixed to the top surface of the platform; the second layer of the guide device is provided using the platform steel pipe piles, that is, the corbels are welded on the steel pipe piles, and I25a I-beams are laid on the corbels and welded to the corbels. When installing the second layer of the guide device, a hanging hammer ball method is required to ensure that the two layers of guide frames are perpendicular to each other; the positioning of the open hole casing is achieved by setting large diameter bolts in the center of the four sides of the guide device, and the screws are welded and locked with the nuts, and the edge of each screw is 10 mm away from the designed position of the outer edge of the casing.

[0060] In a preferred implementation manner of this embodiment, in step S5 of the pile foundation structure construction method, the main reinforcement is placed on a semicircular mounting platform, and after the main reinforcement is installed, the reinforcing hoops are placed, the verticality of the reinforcing hoops and the main reinforcement is corrected, and then they are spot welded and fixed; after the main reinforcement is arranged, the spiral reinforcement is placed, and the spiral reinforcement is inserted into the main reinforcement in sections according to the designed spacing and spot welded, and positioning reinforcement is welded on the main reinforcement in the length direction of the steel cage, and the positioning reinforcement corresponds to the reinforcing hoops and is arranged equidistantly along the circumference according to the design requirements.

[0061] The above pile foundation structure construction method ensures the appropriate position and depth of the bridge pile foundation, improving the safety and stability of the bridge structure; through measures such as the burial of the drilling casing, the follow-up of the inner casing, and the treatment of the cave, the stability during the drilling process and the correct installation of the steel pipe piles are guaranteed, avoiding construction difficulties caused by poor geological conditions; the steel cage is manufactured in sections according to standard section lengths, which can be easily transported and spliced ​​on site, shortening the construction period; the use of underwater concrete pouring can form a dense structural system for the bridge pile foundation, thereby improving the bearing capacity and stability of the bridge.

[0062] In summary, this embodiment is specifically applied to the Chashen Bridge project. The bridge is a three-span continuous beam, and the main body of the continuous beam is a variable-section continuous beam structure. The three-span continuous beam is supported by two low curved piers. Regarding the variable-section low curved pier, when designing and calculating the pull-out force of the main pier cap and pile foundation, in order to consider the amplified effect of the low curved pier on the pull-out force of the cap and pile foundation due to the greater rigidity of the main pier structure, the aspect ratio formula is introduced. The ratio of the side length or diameter of the main pier cross section to the height of the main pier body is used as the pull-out force influence coefficient characterized by its rigidity. a takes the side length or diameter of the maximum main pier cross section, that is, the connection between the continuous beam main body and the main pier is the maximum main pier cross section. The pull-out force borne at the maximum main pier cross section is the largest. When the corresponding main pier maximum aspect ratio e is taken max As an influence coefficient, the pull-out force design requirement of the corresponding pile foundation can be estimated, while ensuring that the pull-out force design requirement of the pile foundation is within the safety value, thereby improving the reliability and stability of the entire main pier foundation's seismic and wind-resistant structure. Therefore, the low curved pier can withstand the upward pulling force generated by the vibration of the three-span continuous beam.

[0063] To further improve the pullout resistance of the low-profile curved piers, a double-layer steel cage is installed within the pile foundation structure. The double-layer steel reinforces the low-profile curved piers' load-bearing capacity, enabling them to withstand the upward pullout forces generated during bridge vibration. The outer main reinforcement, with short and long bars spaced circumferentially along the cage, enhances the concrete column's resistance to lateral displacement and torsional to improve its overall stability. This arrangement ensures the safety and reliability of the low-profile curved piers during bridge vibration. Furthermore, the use of low-profile curved piers can reduce traffic disruption and improve road efficiency. Compared to other high-profile pier designs, the arched low-pier continuous beam bridge of the present invention is not only aesthetically pleasing, but also offers advantages such as lower cost and reduced construction difficulty.

[0064] The embodiments of the present invention are described in detail above with reference to the accompanying drawings, but the present invention is not limited to the described embodiments. It is apparent to those skilled in the art that various changes, modifications, substitutions, and variations to these embodiments may be made without departing from the principles and spirit of the present invention, and these changes and modifications still fall within the scope of protection of the present invention.

Claims

1. An arched low-pier continuous beam bridge foundation, comprising a continuous beam body and a plurality of piers, the continuous beam body being an arched variable-section continuous beam structure; the plurality of piers being disposed below the continuous beam body and supporting the continuous beam body; the plurality of piers comprising two main piers, each of which is supported by a cap; a pile foundation structure being disposed below the cap; the pile foundation structure comprising a casing and a reinforcement cage, the casing being sleeved over the reinforcement cage and fixedly connected to the reinforcement cage; The main pier is a low curved pier. The cross section of the low curved pier gradually increases from the pier cap to the bottom of the continuous beam body. When designing the seismic and wind-resistant structure of the main pier cap and pile foundation, that is, when performing pull-out force design calculations, the amplification effect of the low curved pier on the pull-out force of the pier cap and pile foundation due to the greater rigidity of the main pier structure should be considered. The aspect ratio e is set as follows: e=a / h, where a is the side length or diameter of the main pier cross section, and h is the height of the main pier body; According to the above formula, the design pull-out force of the cap or pile foundation is as follows: where f 设 is the design pull-out force of the cap or pile foundation, where f 计 Calculated pull-out force for the main pier; For low curved piers, the aspect ratio e is selected as the coefficient of influence of the pull-out force caused by its rigidity.

2. The arched low-pier continuous beam bridge foundation according to claim 1, characterized in that: The corresponding maximum aspect ratio of the main pier is e max As the influence coefficient, it is used to estimate the design demand for the pull-out force of the corresponding pile foundation bearing, that is, the maximum flatness ratio a max Take the side length or diameter of the largest main pier cross section.

3. The arched low-pier continuous beam bridge foundation according to claim 1, characterized in that: The cross section of the main pier is circular, and the aspect ratio a is the diameter of the circle; the cross section of the main pier is square, and the aspect ratio a is the longest side of the square.

4. The arched low-pier continuous beam bridge foundation according to claim 1, characterized in that: The main pier is divided into two sections, the upper main pier and the lower main pier, by the pier body dividing line. The lower main pier is the inclined part from the base elevation to the pier body dividing line; the upper main pier is the curved part from the pier body dividing line to the bottom of the continuous beam body.

5. The arched low-pier continuous beam bridge foundation according to claim 1, characterized in that: A steel cage with double-layer steel bars is provided in the pile foundation structure. The outer main bars of the steel cage are formed by a plurality of long bars and a plurality of short bars arranged radially at intervals. The outer wall of the outer main bars is welded and fixed by spiral bars. The inner wall of the outer main bars is provided with an outer reinforcing hoop and fixed by welding. The inner main bars of the steel cage are formed by a plurality of steel bars and are arranged on the inner side of the outer main bars. An inner reinforcing hoop is provided on the inner wall of the inner main bars every several meters. An inner triangular support is provided on the inner reinforcing hoop, and the inner triangular support is aligned from top to bottom in the same plane position along the length of the pile; the spiral bars are composed of two sections of spiral bar units with different pitches, and the pitch of the second section of the spiral bar unit is twice the pitch of the first section of the spiral bar unit; positioning bars are provided around the outer and inner reinforcing hoops, with a group provided every several meters and a plurality of positioning bars arranged in each group.

6. The arched low-pier continuous beam bridge foundation according to claim 5, characterized in that: The steel cage is formed by welding, and the reinforcing hoops are double-sided welded; the steel bars of the steel cage are all HRB400 steel bars.

7. A construction method for an arched low pier continuous beam bridge foundation as claimed in claim 5, characterized in that The construction method of the pile foundation structure specifically includes the following steps: S1. Construction preparation: Measure the vertical and horizontal coordinates and span coordinates to determine the pile position; then conduct geological drilling to determine the designed pile length; finally, survey the practical site within the pile foundation construction range to determine the bridge pile foundation construction surface; S2. Drilling platform erection: The drilling platform uses a steel pipe pile foundation, and the upper structure uses Bailey beams as the upper load-bearing structure. I-beams and steel plates are laid on top of the load-bearing structure as the bridge deck structure. The steel pipe piles are driven in with a vibratory hammer. After the driving is completed, the upper structure and steel panels are installed. S3. Burying of drilling casing: After the drilling platform is set up, a guide device is installed on the top of the platform. The drilling casing is pre-buried using a pile hammer. The casing is required to penetrate the strongly weathered rock by no less than 50 cm. At the same time, the drilling casing must be buried to ensure that the deviation between the center of the drilling casing top surface and the designed pile position is no more than 5 cm, and the inclination is no more than 1 / 200. S4. Inner casing follow-up and cave treatment: In the center of the buried casing, the inner casing is used to follow up the cave in the karst area. After the inner casing is buried, the pile hammer is replaced and continued to drive. The cave is backfilled with a three-phase mixture of stone, clay and bagged cement in the weight ratio of 6.5:3:0.

5. S5. Fabrication and installation of steel cage: The steel cage is fabricated in sections at the steel processing plant. For each section of the steel cage, the outer main reinforcement is first installed, followed by the outer reinforcing hoops; then the inner main reinforcement is installed, followed by the inner reinforcing hoops; finally, the inner triangular bracing, spiral reinforcement and positioning reinforcement are installed; The designed cage length of the pile foundation reinforcement cage is adjusted according to the pile length. The reinforcement cage is manufactured in sections with a standard section length of 12~13m. The top cage and the middle cage are both standard sections, and the bottom cage is an adjustable section. The processed double-layer reinforcement cage is transported to the site for installation and docking. It is lowered to the pile foundation hole by a crane, and lowered vertically along the inner wall of the casing. The three sections of the reinforcement cage are matched and connected to the main reinforcement through straight threaded sleeves. The number of main reinforcement joints in the same connection section shall not exceed 50%, and the spacing between adjacent joints shall be 35d and not less than 500mm. Finally, the docked reinforcement cage is placed in the pile foundation hole. S6. Underwater concrete pouring: Pour the pile body concrete into the pile foundation hole to complete the pile foundation construction.

8. The construction method of an arched low pier continuous beam bridge foundation according to claim 7, characterized in that: The guide device described in step S3 of the pile foundation structure construction method is provided with two layers in total, and the first layer of the guide device is fixed to the top surface of the platform; the second layer of the guide device is provided using the platform steel pipe pile, that is, the corbel is welded on the steel pipe pile, and the I25a I-beam is laid on the corbel and welded to the corbel. When installing the second layer of the guide device, the hanging hammer ball method must be adopted to ensure that the two layers of guide frames are perpendicular to each other; the positioning of the open hole casing is achieved by setting large-diameter bolts in the center of the four sides of the guide device, and the screws and nuts are welded and locked, and the edge of each screw is 10 mm away from the designed position of the outer edge of the casing.

9. The construction method of an arched low pier continuous beam bridge foundation according to claim 7, characterized in that: In step S5 of the pile foundation structure construction method, the main reinforcement is placed on a semicircular mounting platform, and after the main reinforcement is installed, the reinforcing hoops are placed, the verticality of the reinforcing hoops and the main reinforcement is corrected, and then they are spot welded and fixed; after the main reinforcement is arranged, the spiral reinforcement is placed, and the spiral reinforcement is inserted into the main reinforcement in sections according to the designed spacing and spot welded on the main reinforcement, and positioning reinforcement is welded on the main reinforcement in the length direction of the steel cage, and the positioning reinforcement is arranged equidistantly along the circumference corresponding to the reinforcing hoops according to the design requirements.

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