An anti-corrosion structure and construction method for the pile foundation columns of a seawall bridge

Abstract

The present invention discloses an anti-corrosion structure and construction method for bridge pile foundation columns of a seawall, including a seawall, an outer slope, a road surface, an inner slope, etc. Mainly, a pile foundation of a bridge bored pile is set on the inner slope at the inner edge of the road surface. After the concrete at the top of the pile foundation is excavated, the pile head concrete is chiseled off, and the steel bars are extended and concrete is poured to form a column. Then, a three-dimensional composite drainage net is arranged outside the column and wrapped from bottom to top. At the same time, the inner side of the three-dimensional composite drainage net extends downward at a certain slope to overlap with the top of the drainage ditch on the inner slope to form a hopper shape. Compacted backfill soil and salt-tolerant vegetation are filled in the space enclosed by the hopper shape and the column. The gap between the outer side of the three-dimensional composite drainage net and the road surface is backfilled with compacted backfill material. Therefore, the improved anti-corrosion structure has construction advantages such as simple structure, economic savings, ecological environmental protection, safety and high efficiency, and convenient construction. Combined with the corresponding construction method, it has remarkable economic benefits, energy conservation and environmental protection benefits, and social benefits.

Description

Technical Field

[0001] The present invention relates to the field of environmental protection construction of bridges, and specifically refers to an anti-corrosion structure and construction method for the pile foundation columns of seawall bridges. Background Art

[0002] The main facility for reclaiming land from the sea is the seawall, which plays a role in promoting the formation of the reclamation project and protecting the reclaimed land. Highways and municipal roads are often built on or inside the seawall in the reclaimed area from the sea, or bridge pile foundations are set on the seawall. Due to the corrosiveness of seawater, protective measures need to be taken for the concrete engineering structure according to the actual situation.

[0003] The existing main anti-corrosion measures for concrete include external protection such as concrete surface coating, silane impregnation, impressed current cathodic protection of concrete, epoxy resin-coated steel bars, hot-dip galvanized steel bars, stainless steel bars, permeable formwork, hydrophobic chemical pore plugs, sprayed polyurea elastomers, etc., and marine concrete that improves the anti-corrosion performance of concrete itself. These measures can all increase the structural durability to varying degrees, but some have a relatively low anti-corrosion cost performance, some have poor environmental protection performance and may cause secondary pollution, and some have cumbersome construction. Therefore, it is necessary to develop a concrete anti-corrosion structure and construction method with better anti-corrosion effect, low cost, ecological environmental protection and convenient construction. At the same time, the anti-corrosion performance sensitivity of the structure near the joint of the pile foundation and the column is the greatest, and more effective anti-corrosion measures need to be taken. Summary of the Invention

[0004] The technical problem to be solved by the present invention is to overcome the defects of the prior art and provide an anti-corrosion structure and construction method for the pile foundation columns of seawall bridges that are simple in structure, economical, ecological and environmentally friendly, safe and efficient, and convenient for construction.

[0005] The technical problem of the present invention is realized through the following technical solutions:

[0006] An anti-corrosion structure for the pile foundation columns of seawall bridges includes a seawall, an outer slope outside the seawall, a road surface on the top of the seawall, and an inner slope inside the seawall. A pile foundation of a bridge bored cast-in-place pile is set on the inner slope at the inner edge of the road surface. After the concrete at the top of the pile foundation is excavated, the pile head concrete is chiseled off, and the steel bars are spliced and concrete is poured to form a column. Then, a three-dimensional composite drainage net is wrapped around the column from bottom to top. The inner side of the three-dimensional composite drainage net extends downward at a certain slope to overlap with the top of the drainage ditch on the inner slope to form a hopper shape. The space enclosed by the hopper shape and the column is filled with compacted backfill soil, and polyhalophyte vegetation is planted on the backfill soil. The gap formed by excavating the pile head at the top of the pile foundation between the outer side of the three-dimensional composite drainage net and the road surface is filled with compacted backfill material.

[0007] The described three-dimensional composite drainage net includes a three-dimensional geogrid core, with a needle-punched perforated non-woven geotextile adhered to one side of the geogrid core and an anti-seepage geomembrane adhered to the other side; the geogrid core includes a vertical rib, and an inclined rib at the top and bottom respectively; the anti-seepage geomembrane of the three-dimensional composite drainage net faces the backfill and the bottom of the backfill soil, and generates a shear resistance at the top surface of the contact part of the backfill soil triangular load and the shear stress of its own tensile deformation . Assuming that the displacement of the three-dimensional composite drainage net in the direction of the inner slope of the column and the vertical section of the outer diameter of the column is zero, the included angle between the bottom surface of the three-dimensional composite drainage net with a comprehensive tensile stiffness of K and the top of the drainage ditch is , the inclined length is L, and the coefficient of earth pressure at rest of the backfill soil with a unit weight of is K x . The normal stress and active shear stress of the backfill soil in the directions perpendicular and parallel to the top surface of the three-dimensional composite drainage net are respectively . The displacement differential equation and the tensile force of the three-dimensional composite drainage net under the action of the backfill soil triangular load T ( x ) calculation formula are obtained;

[0008] Formula 1. Differential equation and analytical solution of the three-dimensional composite drainage net under the action of the backfill soil (6) triangular load

[0009]

[0010] In the formula

[0011]

[0012] When the three-dimensional composite drainage net is in the elastic working stage, , we get

[0013]

[0014] In the formula

[0015]

[0016] The boundary conditions are

[0017]

[0018] Solving the above differential equation, we get

[0019]

[0020] In the formula

[0021]

[0022] Formula 2. Calculation of the maximum tensile force of the three-dimensional composite drainage net

[0023]

[0024] The definitions of each symbol in Formula 1 to Formula 2 are as follows:

[0025] —— The diameter of the pile foundation or column ;

[0026] —— The inclined length when the angle between the bottom surface of the three-dimensional composite drainage net and the top of the drainage ditch is ;

[0027] —— The angle between the bottom surface of the three-dimensional composite drainage net and the horizontal plane ;

[0028] —— The displacement at any when the three-dimensional composite drainage net is under tension ;

[0029] —— The abscissa with the vertical section of the outer diameter of the column as the origin in the direction of the inner slope of the column for the three-dimensional composite drainage net ;

[0030] —— The unit weight of the backfill soil ;

[0031] —— The coefficient of earth pressure at rest of the backfill soil

[0032] —— The comprehensive tensile stiffness of the three-dimensional composite drainage net ;

[0033] —— The vertical stress, the horizontal stress parallel to the top surface of the three-dimensional composite drainage net, the normal stress perpendicular to the top surface of the three-dimensional composite drainage net (4), and the active shear stress on the top surface of the three-dimensional composite drainage net respectively ;

[0034] —— The shear stress when the three-dimensional composite drainage net is under tension ;

[0035] —— The displacement at any when the three-dimensional composite drainage net is under tension ;​

[0036] —— Tensile force at any point when the three - dimensional composite drainage net is under tension, ; ;

[0037] —— Allowable tensile force of the three - dimensional composite drainage net, ;

[0038] —— Proportionality coefficient between shear stress and displacement when the three - dimensional composite drainage net is in the elastic working stage, ;

[0039] —— Coefficient, , ;

[0040] —— Coefficient, ;

[0041] —— Coefficient, 。

[0042] The backfill soil is the backfill soil at the excavation gap during the construction of pile foundations and the laying of three - dimensional composite drainage nets on the seawall, and is backfilled and compacted in layers with a thickness of 20 cm to 30 cm.

[0043] The backfill material is gravel with good permeability, which is filled in the excavation gaps of the seawall and the road surface, and is located between the outer side of the three - dimensional composite drainage net and the road surface.

[0044] The drainage ditch is longitudinally arranged along the inner slope and discharges the water permeated from the three - dimensional composite drainage net.

[0045] The bottom of the seawall is provided with a ground line, which is the ground of the reclaimed seawall or the coastal water network dike pond. The seawall has a trapezoidal cross - section that is narrower at the top and wider at the bottom. The outer slope is the outer side of the seawall facing the sea water or the water network, and the opposite inner side of the seawall is the inner slope. The road surface is the top surface of the seawall for vehicle or pedestrian passage.

[0046] A water retaining wall is provided at the outer edge of the road surface.

[0047] A construction method for the anti - corrosion structure of the pile foundation columns of a seawall bridge includes the following steps:

[0048] Step 1: Preliminary design of the anti - corrosion structure of the pile foundation and columns of the seawall bridge

[0049] 1. Detect the content of harmful substances in the water inside and outside the seawall and in the seawall, and analyze the water penetration law and its impact on the engineering structure in combination with the geological data of the seawall;

[0050] 2. Based on the situation of harmful substances in water bodies, preliminarily determine the anti-corrosion structure dimensions of the bridge piles and columns of the seawall, select the model specifications of the three-dimensional composite drainage net, and quantitatively calculate and analyze the anti-corrosion indicators of the bridge piles and columns;

[0051] 3. Recheck the mechanical properties of the three-dimensional composite drainage net according to Formula 1 and Formula 2, and recheck the standards and design requirements;

[0052] 4. Design the construction drawings of the anti-corrosion structure of the bridge piles and columns of the seawall, and put forward construction technical requirements and precautions;

[0053] Step 2. Construction of the anti-corrosion structure of the bridge piles and columns of the seawall

[0054] 1. Test and detect the indicators such as the peel strength and water permeability rate of the three-dimensional composite drainage net, which meet the design requirements;

[0055] 2. Measure and set out the positions of the bridge piles on the inner slope of the seawall, and excavate the inner slope of the seawall to the design elevation of the bridge piles;

[0056] 3. Erect the pile foundation construction machinery to carry out pile foundation drilling, lower the steel reinforcement cage, and complete the pile foundation construction by pouring concrete;

[0057] 4. Excavate the concrete at the top of the pile foundation to a certain depth to chisel off the pile head concrete, extend the reinforced concrete column, remove the backfill soil on the inner slope, excavate the drainage ditch, and compact the pile foundation to the slope surface of the drainage ditch with a small compaction machine, and the slope surface is 1% - 2%;

[0058] 5. Then wrap the three-dimensional composite drainage net from bottom to top on the side of the column outer diameter close to the road surface. The three-dimensional composite drainage net extends from the side of the column outer diameter close to the road surface to the inner slope of the seawall downward according to the design slope and overlaps with the top of the drainage ditch on the inner slope, so that the three-dimensional composite drainage net is in an overall dustpan shape;

[0059] 6. Backfill and compact the backfill material outside the three-dimensional composite drainage net on the side of the column close to the road surface, and fill and compact the backfill soil in the dustpan-shaped enclosed space between the column and the three-dimensional composite drainage net;

[0060] 7. Plant salt-tolerant vegetation such as Salicornia europaea, Atriplex patens, Albizia julibrissin, Robinia pseudoacacia, Jasminum nudiflorum, Hibiscus syriacus, Lonicera japonica, Campsis grandiflora, Sabina chinensis, Ligustrum lucidum on the backfill soil, and maintain it in a timely manner;

[0061] Step 3. Regularly detect and understand the anti-corrosion effect

[0062] Regularly take samples to detect the water body in the drainage ditch to understand the anti-corrosion effect of the three-dimensional composite drainage net. If problems are found, take measures in a timely manner to improve the durability of the bridge piles and columns of the seawall.

[0063] Compared with the prior art, the present invention mainly sets the pile foundation of the bridge bored cast-in-place pile on the inner slope of the inner edge of the road surface of the seawall. After the concrete at the top of the pile foundation is excavated, the pile head concrete is chiseled off, and the steel bars are extended and concrete is poured to form a column. At the same time, a three-dimensional composite drainage net is provided outside the column, which is wrapped from bottom to top. At the same time, the inner side of the three-dimensional composite drainage net extends downward along the designed slope to the top of the drainage ditch on the inner slope and overlaps to form a dustpan shape. The space enclosed by the dustpan shape and the column is filled with compacted backfill soil, and polyhalophyte vegetation is planted on the backfill soil. The gap between the outer side of the three-dimensional composite drainage net and the road surface is filled with compacted backfill material. The anti-corrosion structure adopted by the present invention mainly has the following advantages: First, it has a high cost performance compared with the existing concrete anti-corrosion methods, will not cause secondary pollution, and is ecological and environmentally friendly; Second, the structure near the joint of the pile foundation and the column is most likely to have construction quality problems, which is the key anti-corrosion part and has strong pertinence; Third, the structure is simple, the construction is convenient, the construction machinery, materials and labor are saved, and the cost is low; Fourth, the provided design calculation method has clear principles, is scientific and reasonable, practical and easy to implement, can guide the anti-corrosion structure design and construction of the seawall bridge pile foundation and column, and improves the safety performance and durability. Therefore, the present invention has construction advantages such as simple structure, economic savings, ecological environmental protection, safety and high efficiency, and convenient construction, reflects the concept of green engineering construction, improves the durability of the engineering structure, and has high economic benefits, energy conservation and environmental protection benefits and social benefits in combination with the corresponding construction methods. BRIEF DESCRIPTION OF THE DRAWINGS

[0064] Figure 1 It is an elevation view of the present invention.

[0065] Figure 2 It is a structural schematic diagram of the column combined with the three-dimensional composite drainage net.

[0066] Figure 3 It is an internal force calculation diagram of the three-dimensional composite drainage net. DETAILED DESCRIPTION OF THE INVENTION

[0067] The embodiments of the present invention will be further described in detail below with reference to the above drawings.

[0068] As Figures 1 to 3 shown, 1. Ground line, 2. Seawall, 21. Outer slope, 22. Inner slope, 23. Drainage ditch, 24. Water retaining wall, 25. Road surface, 3. Column, 4. Three-dimensional composite drainage net, 5. Backfill material, 6. Backfill soil, 7. Vegetation.

[0069] An anti-corrosion structure and construction method for the pile foundation column of a seawall bridge, as Figure 1 shown, relates to the field of bridge environmental protection construction, and its structure includes a seawall 2, an outer slope 21 outside the seawall, a road surface 25 on the top of the seawall, and an inner slope 22 inside the seawall.

[0070] The bottom of the seawall is provided with a ground line 1, which is the ground of the reclaimed seawall or the coastal water network dyke, and the seawall or dyke has a trapezoidal cross-section that is narrower at the top and wider at the bottom. The outer slope 21 is the outer side of the seawall facing the sea water or water network, and the opposite inner side of the seawall is the inner slope 22. The road surface 25 is the top surface of the seawall for vehicle or pedestrian passage, and a water retaining wall 24 is provided at the outer edge of the road surface. Due to the seepage of water, seawater or polluted water will seep into the seawall or dyke, corroding the pile foundation concrete on the seawall or dyke, which will affect the durability of the engineering structure.

[0071] The pile foundation of the bridge bored cast-in-place pile is set on the inner slope 22 at the inner edge of the road surface. The concrete at the top of the pile foundation is excavated to a certain depth to remove the pile head concrete, and the steel bars are extended and concrete is poured to form a column 3. Then, a three-dimensional composite drainage net 4 is wrapped around the column from bottom to top.

[0072] The three-dimensional composite drainage net 4 includes a three-dimensional geotextile core, with a needle-punched perforated non-woven geotextile adhered to one side of the geotextile core and an anti-seepage geomembrane adhered to the other side. The geotextile core includes a relatively thick vertical rib, and an inclined rib at the top and bottom respectively; the three-dimensional composite drainage net 4 itself is a pore maintenance system, which can block capillary water under high load. At the same time, it can also play a role in isolating the salt-containing corrosive seepage water of the seawall and strengthening the inner slope.

[0073] The inner side of the three-dimensional composite drainage net 4 extends downward at a certain slope to overlap with the top of the drainage ditch 23 on the inner slope to form a dustpan shape. The space enclosed by the dustpan shape and the column 3 is filled with compacted backfill soil 6, and salt-tolerant vegetation 7 is planted on the backfill soil; the gap formed by excavating the pile head at the top of the pile foundation between the outer side of the three-dimensional composite drainage net 4 and the road surface 25 is filled with compacted backfill material 5.

[0074] The backfill material 5 is gravel with good permeability, which is filled in the gap excavated on the seawall 2 and the road surface, and is located between the outer side of the three-dimensional composite drainage net 4 and the road surface 25, and is compacted with small machinery; the backfill soil 6 is the backfill soil at the gap excavated during the construction of the pile foundation and the laying of the three-dimensional composite drainage net 4 on the seawall 1, which is backfilled in layers with a thickness of 20 cm to 30 cm and is compacted with small compaction machinery, and the drainage net is not damaged during filling and compaction.

[0075] The drainage ditch 23 is longitudinally arranged along the inner slope and drains the water seeping from the three-dimensional composite drainage net 4, playing a role in protecting the pile foundation concrete from corrosion.

[0076] The vegetation 7 is greening plants, which not only play a role in beautifying the environment, but also the salt-tolerant vegetation can absorb salt and reduce the salt content of the seabed slope.

[0077] The described three-dimensional composite drainage net 4 includes a three-dimensional geogrid core, with a needle-punched perforated non-woven geotextile adhered to one side of the geogrid core and an anti-seepage geomembrane adhered to the other side; the geogrid core includes a vertical rib, and an inclined rib at the top and bottom respectively; the anti-seepage geomembrane of the three-dimensional composite drainage net 4 faces the backfill 5 and the bottom of the backfill soil 6, and generates a shear resistance and a shear stress for its own tensile deformation at the top surface of the contact area of the backfill soil triangular load . Assuming that the displacement of the three-dimensional composite drainage net 4 in the direction of the inner slope of the column and the vertical section of the outer diameter of the column is zero, the included angle between the bottom surface of the three-dimensional composite drainage net with a comprehensive tensile stiffness of K and the top of the drainage ditch is , the inclined length is L, and the coefficient of earth pressure at rest of the backfill soil with a unit weight of is K x . The normal stress and active shear stress of the backfill soil in the directions perpendicular and parallel to the top surface of the three-dimensional composite drainage net are respectively . The displacement differential equation and the tensile force of the three-dimensional composite drainage net under the action of the backfill soil triangular load T ( x ) calculation formula are obtained;

[0078] Formula 1. Differential equation and analytical solution of the three-dimensional composite drainage net 4 under the action of the backfill soil 6 triangular load

[0079]

[0080] Where

[0081]

[0082] When the three-dimensional composite drainage net 4 is in the elastic working stage, , we get

[0083]

[0084] Where

[0085]

[0086] The boundary conditions are

[0087]

[0088] Solving the above differential equation, we get

[0089]

[0090] Where

[0091]

[0092] Formula for calculating the maximum tensile force of the three-dimensional composite drainage net 4

[0093]

[0094] The definitions of the symbols in Formula 1 to Formula 2 are as follows:

[0095] —— The diameter of the pile foundation or column 3, ;

[0096] —— The inclined length at the angle of between the bottom surface of the three-dimensional composite drainage net 4 and the top of the drainage ditch 23, ;

[0097] —— The angle between the bottom surface of the three-dimensional composite drainage net 4 and the horizontal plane, ;

[0098] —— The displacement at any when the three-dimensional composite drainage net 4 is under tension, ;

[0099] —— The abscissa with the vertical section of the outer diameter of the column 3 in the direction of the inner slope 22 as the origin when the three-dimensional composite drainage net 4 is under tension, ;

[0100] —— The unit weight of the backfill soil 6, ;

[0101] —— The coefficient of earth pressure at rest of the backfill soil 6;

[0102] —— The comprehensive tensile stiffness of the three-dimensional composite drainage net 4, ;

[0103] —— The vertical stress, the horizontal stress parallel to the top surface of the three-dimensional composite drainage net 4, the normal stress perpendicular to the top surface of the three-dimensional composite drainage net 4, and the active shear stress on the top surface of the three-dimensional composite drainage net 4 respectively, ;

[0104] —— The shear stress when the three-dimensional composite drainage net 4 is under tension, ;

[0105] —— The displacement at any when the three-dimensional composite drainage net 4 is under tension, ;

[0106] —— Tensile force at any point on the three - dimensional composite drainage net 4 when it is in tension, ; ;

[0107] —— Allowable tensile force of the three - dimensional composite drainage net 4, ;

[0108] —— Proportionality coefficient between shear stress and displacement when the three - dimensional composite drainage net 4 is in the elastic working stage, ;

[0109] —— Coefficient, , ;

[0110] —— Coefficient, ;

[0111] —— Coefficient, .

[0112] The construction method of the anti - corrosion structure of the pile foundation columns of the seawall bridge mainly includes the following steps:

[0113] Step 1: Preliminary design of the anti - corrosion structure of the pile foundation and columns of the seawall bridge

[0114] 1. Detect the content of harmful substances in the water inside and outside the seawall and in the seawall, and analyze the water penetration law and its impact on the engineering structure in combination with the geological data of the seawall;

[0115] 2. According to the situation of harmful substances in the water, preliminarily design the dimensions of the anti - corrosion structure of the pile foundation and columns of the seawall bridge, select the model specifications of the three - dimensional composite drainage net, and quantitatively calculate and analyze the anti - corrosion indexes of the pile foundation and columns of the bridge;

[0116] 3. Re - check the mechanical properties of the three - dimensional composite drainage net according to Formula 1 and Formula 2, and the re - check standards and design requirements;

[0117] 4. Design the construction drawings of the anti - corrosion structure of the pile foundation and columns of the seawall bridge, and put forward construction technical requirements and precautions;

[0118] Step 2: Construction of the anti - corrosion structure of the pile foundation and columns of the seawall bridge

[0119] 1. Test and detect indexes such as the peel strength and water permeability rate of the three - dimensional composite drainage net, which meet the design requirements;

[0120] 2. Measure and set out the positions of the pile foundations of the inner slope of the seawall bridge, and excavate the inner slope of the seawall to the design elevation of the pile foundation of the bridge;

[0121] 3. Erect pile foundation construction machinery to carry out pile foundation drilling, lower the steel reinforcement cage, and complete the pile foundation construction by pouring concrete;

[0122] 4. Excavate the concrete at the top of the pile foundation to a certain depth, chisel off the pile head concrete, extend the reinforced concrete column, and remove the backfill soil on the inner slope. Excavate the drainage ditch 23, and compact the pile foundation to the slope of the drainage ditch with a small compaction machine. The slope is 1% - 2%;

[0123] 5. Then wrap the three - dimensional composite drainage net 4 from bottom to top along the side of the column outer diameter close to the road surface. The three - dimensional composite drainage net extends downward from the side of the column outer diameter close to the road surface to the top of the drainage ditch 23 on the inner slope 22 of the seawall according to the design slope, so that the three - dimensional composite drainage net 4 is in an overall shape of a dustpan;

[0124] 6. Backfill the compacted backfill material 5 outside the three - dimensional composite drainage net 4 on the side of the column close to the road surface, and fill and compact the backfill soil 6 in the dustpan - shaped enclosed space between the column 3 and the three - dimensional composite drainage net 4;

[0125] 7. Plant salt - accumulating vegetation 7, such as Salicornia europaea, Atriplex patens, Albizia julibrissin, Robinia pseudoacacia, Jasminum nudiflorum, Hibiscus syriacus, Lonicera japonica, Campsis grandiflora, Sabina chinensis, Ligustrum lucidum, etc. on the backfill soil, and maintain it in a timely manner;

[0126] Step Three: Regularly detect to understand the anti - corrosion effect

[0127] Regularly take samples to detect the water body in the drainage ditch to understand the anti - corrosion effect of the three - dimensional composite drainage net. When problems are found, take measures in time to improve the durability of the pile foundation and column of the seawall bridge.

[0128] The above - mentioned are only specific embodiments of the present invention. Those skilled in the art should understand that any structural design equivalent to this embodiment should be included within the protection scope of the present invention.

Claims

1. An anti-corrosion structure for a pile foundation column of a seawall bridge, comprising a seawall (2), an outer slope (21) on the outer side of the seawall, a road surface (25) on the top surface of the seawall, and an inner slope (22) on the inner side of the seawall, characterized in that, On the inner slope (22) of the inner edge of the pavement (25), a pile foundation of a bridge bored cast-in-place pile is set. After the concrete at the top of the pile foundation is excavated, the pile head concrete is chiseled off, and the steel bars are extended and concrete is poured to form a column (3). A three-dimensional composite drainage net (4) is wrapped around the column from bottom to top. The inner side of the three-dimensional composite drainage net extends downward at a certain slope and overlaps with the top of the drainage ditch (23) on the inner slope (22) to form a hopper shape. Backfill soil (6) is filled and tamped in the space enclosed by the hopper shape and the column (3), and salt-tolerant vegetation (7) is planted on the backfill soil. The gap formed by excavating the pile head at the top of the pile foundation between the outer side of the three-dimensional composite drainage net (4) and the pavement (25) is backfilled with compacted backfill material (5). The three-dimensional composite drainage net (4) includes a three-dimensional geonet core, with a needle-punched perforated non-woven geotextile adhered to one side of the geonet core and an anti-seepage geomembrane adhered to the other side. The geonet core includes a vertical rib and an inclined rib at the top and bottom respectively. The anti-seepage geomembrane of the three-dimensional composite drainage net (4) faces the backfill material (5) and the bottom of the backfill soil (6).

2. The anti-corrosion structure of the pile foundation column of a seawall bridge according to claim 1, characterized in that, The backfill soil triangular load generates a resisting shear force at the top surface of the contact area and a shear stress for self-stretching deformation . Assuming that the displacement of the three-dimensional composite drainage net (4) in the direction of the inner slope of the column and the vertical profile of the outer diameter of the column is zero, the included angle between the bottom surface of the three-dimensional composite drainage net with a comprehensive tensile stiffness of K and the top of the drainage ditch is , the inclined length is L, and the coefficient of earth pressure at rest of the backfill soil with a unit weight of is K x . The normal stress and active shear stress of the backfill soil in the directions perpendicular and parallel to the top surface of the three-dimensional composite drainage net are respectively . The displacement differential equation and the tensile force of the three-dimensional composite drainage net under the action of the backfill soil triangular load T ( x ) calculation formula; Formula 1, Differential Equation and Analytical Solution of the Three-Dimensional Composite Drainage Net (4) under the Triangular Load of the Backfill Soil (6) ​ In the formula When the three-dimensional composite drainage net (4) is in the elastic working stage, , it is obtained that In the formula The boundary condition is Solving the above differential equation, we get In the formula Formula II. Calculation of the maximum tensile force of the three-dimensional composite drainage net (4) The definitions of each symbol in Formula I - Formula II are as follows: —— Diameter of pile foundation or column (3), ; —— The included angle between the bottom surface of the three-dimensional composite drainage net (4) and the top of the drainage ditch (23) is the oblique length of ; —— the included angle between the bottom surface of the three-dimensional composite drainage net (4) and the horizontal plane, ; —— Displacement at any point when the three-dimensional composite drainage net (4) is in tension, ; ; —— The abscissa with the vertical section of the outer diameter of the column (3) as the origin in the direction of the three-dimensional composite drainage net (4) towards the inner slope (22) of the column (3), ; —— unit weight of backfill soil (6), ; ——Coefficient of earth pressure at rest of the backfill soil (6); —— Comprehensive tensile stiffness of the three-dimensional composite drainage net (4), ; — the vertical stress, the horizontal stress parallel to the top surface of the three-dimensional composite drainage net (4), the normal stress perpendicular to the top surface of the three-dimensional composite drainage net (4), and the active shear stress acting on the top surface of the three-dimensional composite drainage net (4), respectively ; —— Shear stress when the three-dimensional composite drainage net (4) is in tension, ; —— The displacement at any point when the three-dimensional composite drainage net (4) is in tension, ; ; —— Tensile force at any point when the three-dimensional composite drainage net (4) is under tension, ; ; —— The three-dimensional composite drainage net (4) is allowed to be subjected to tensile force, ; —— The proportional coefficient of shear stress to displacement when the three-dimensional composite drainage net (4) is in the elastic working stage, ; —— coefficient, , ; —— coefficient, ; —— coefficient, .

3. The anti-corrosion structure of the pile foundation column of a seawall bridge according to claim 1, wherein, The backfill soil (6) is the backfill soil at the excavation gap during the construction of the pile foundation and the laying of the three-dimensional composite drainage net (4) on the seawall (2), and is backfilled and compacted in layers with a thickness of 20 cm - 30 cm.

4. The anti-corrosion structure of the pile foundation column of a seawall bridge according to claim 1, characterized in that The backfill material (5) is gravel with good permeability, which is filled in the excavation gap of the seawall (2) and the pavement (25) and is located between the outer side of the three-dimensional composite drainage net (4) and the pavement (25).

5. The anti-corrosion structure of a pile foundation column of a seawall bridge according to claim 1, wherein The drainage ditch (23) is longitudinally arranged along the inner slope (22) and discharges the water permeated from the three-dimensional composite drainage net (4).

6. The anti-corrosion structure of the pile foundation column of a seawall bridge according to claim 1, characterized in that, The bottom of the seawall (2) is provided with a ground line (1), which is the ground of the reclamation seawall or the coastal water network seawall pond. The seawall has a trapezoidal cross-section with a narrow top and a wide bottom. The outer slope (21) is the outer side of the seawall facing the sea water or the water network, and the opposite inner side of the seawall is the inner slope (22). The pavement (25) is the top surface of the seawall for vehicle or pedestrian passage.

7. A corrosion prevention structure for a pile foundation column of a seawall bridge according to claim 1, characterized in that, A water retaining wall (24) is provided at the outer edge of the pavement (25).

8. The construction method of an anti-corrosion structure for a pile foundation column of a seawall bridge according to any one of claims 1 to 7, characterized in that, The construction method includes the following steps: Step 1. Preliminary design of the anti-corrosion structure of the seawall bridge pile foundation and column 1. Detect the content of harmful substances in the water inside and outside the seawall and in the seawall, and analyze the water penetration law and its impact on the engineering structure in combination with the geological data of the seawall; 2. According to the situation of harmful substances in the water, preliminarily design the dimensions of the anti-corrosion structure of the seawall bridge pile foundation and column, select the model specifications of the three-dimensional composite drainage net, and quantitatively calculate and analyze the anti-corrosion indexes of the bridge pile foundation and column; 3. Recheck the mechanical properties of the three-dimensional composite drainage net according to Formula I and Formula II; 4. Design the construction drawings of the anti-corrosion structure of the seawall bridge pile foundation and column, and put forward construction technical requirements and precautions; Step 2. Construction of the anti-corrosion structure of the seawall bridge pile foundation and column 1. Test and detect the peel strength and water conductivity of the three-dimensional composite drainage net, which meet the design requirements; 2. Measure and set out the positions of the bridge pile foundations on the inner slope of the seawall, and excavate the inner slope of the seawall to the design elevation of the bridge pile foundations; 3. Erect pile foundation construction machinery to carry out pile foundation drilling, lower the steel reinforcement cage, and complete the pile foundation construction by pouring concrete; 4. Excavate the concrete at the top of the pile foundation to a certain depth to chisel off the pile head concrete, extend the reinforced concrete column, remove the backfill soil on the inner slope, excavate the drainage ditch, and compact the pile foundation to the slope of the drainage ditch with small compaction equipment, and the slope is 1% - 2%; 5. Then wrap the three-dimensional composite drainage net (4) from bottom to top along the side of the column outer diameter close to the road surface. The three-dimensional composite drainage net extends from the side of the column outer diameter close to the road surface to the inner slope (22) of the seawall downward according to the design slope and overlaps with the top of the drainage ditch (23) on the inner slope (22), so that the three-dimensional composite drainage net is in a dustpan shape as a whole; 6. Backfill the compacted backfill material (5) outside the three-dimensional composite drainage net on the side of the column close to the road surface, and fill and compact the backfill soil (6) in the dustpan-shaped enclosed space between the column and the three-dimensional composite drainage net (4); 7. Plant salt-tolerant vegetation (7) on the backfill soil and carry out timely maintenance; Step 3: Regularly detect and understand the anti-corrosion effect Regularly take samples to detect the water body in the drainage ditch to understand the anti-corrosion effect of the three-dimensional composite drainage net. When problems are found, take measures in time to improve the durability of the seawall bridge pile foundations and columns.

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