A skew bridge abutment foundation adopts a construction method combining cast-in-place piles and shallow foundations

Abstract

The application relates to a construction method of a skew bridge abutment foundation adopting a cast-in-place pile and a shallow foundation combination type, which comprises the following steps: step one, right-width cast-in-place pile construction; the right-width abutment structure foundation adopts group pile design, the number of cast-in-place piles is increased or reduced according to the route width, the abutment foundation structure width, the abutment height, the abutment back soil pressure and the structure stress design requirements; step two, foundation pit excavation, pile head cutting and shallow foundation digging; step three, when the foundation pit is excavated, the left-width shallow foundation one side foundation pit excavation bottom surface should be excavated to the rock layer surface; step four, when the right-width cast-in-place pile one side pile head is cut, the pile cutting surface should be 5 cm higher than the design pile top, a wind pick or a professional pile cutting machine is used to break the pile head, then the pile top surface is manually chiseled to expose the fresh concrete surface; step five, the anchor rod is punched at the shallow foundation. The application effectively solves the problem that only the cast-in-place pile design is adopted but it is difficult to drill into the rock during construction when the geological exploration of the left and right widths of the abutment is inconsistent or the difference is relatively large.

Description

Technical Field

[0001] The invention relates to the technical field of pile foundation engineering, in particular to a construction method for an oblique abutment foundation using a combination of cast-in-place piles and a shallow foundation. Background Art

[0002] In the field of construction engineering or municipal engineering, it is common for abutment foundation structures to use cast-in-place piles as bridge pile foundations. There are also treatment methods such as expanded foundations or shallow foundations. However, it is rare to use a combination of cast-in-place piles and shallow foundations for the same abutment. The abutment foundation structure not only has to bear the load of the bridge superstructure, but also has to bear part of the load transmitted by the back-soil pressure. Therefore, both the design and construction aspects are relatively complicated, especially in skew bridges. The abutment foundation layout is all skewed and needs to match the route direction. Therefore, it brings considerable difficulties and challenges to both design and construction. In order to solve the above problems, a new construction method needs to be invented. Summary of the Invention

[0003] The technical problem to be solved by the present invention is to provide a construction method for the foundation of an oblique abutment using a combination of cast-in-place piles and shallow foundations, which effectively solves the problem that when the geological surveys of the left and right sides of the abutment are inconsistent or very different, it is difficult to drill into the rock during construction if only cast-in-place piles are used, or the problem that only shallow foundation structures are used, which affects the safety and stress conditions of the structure.

[0004] The technical solution adopted by the present invention to solve the technical problem is to provide a construction method for a skew abutment foundation using a combination of cast-in-place piles and shallow foundations, which specifically includes the following steps:

[0005] Step 1: Construction of right span cast-in-place piles. The right span abutment structure foundation adopts a pile group design, with 6 piles in 2 rows. The number of cast-in-place piles will be increased or decreased according to the route width, abutment foundation width, abutment height, abutment back soil pressure, and structural load design requirements. The cast-in-place piles are drilled using the punching method and the concrete is poured using underwater concrete pouring. The pile top surface is designed to be overfilled by at least 1m to ensure the quality of the concrete at the pile top.

[0006] Step 2: Excavate the foundation pit, cut the pile heads, and dig a shallow foundation. After the right-side cast-in-place pile construction is completed and the pile body integrity quality inspection is passed, the next step is to arrange the pile head cutting work. Because the left-side has a shallow foundation, the post-construction method should be selected. If the shallow foundation is constructed first, the foundation pit excavation will disturb the adjacent soil, affecting the construction quality and safety of the cast-in-place piles. Therefore, the left and right foundation pits are excavated simultaneously and the connecting beams are constructed at the same time.

[0007] Step 3: When excavating the foundation pit, the bottom surface of the foundation pit on the left shallow foundation side should be excavated to the rock surface. The rock surface should be compared with the geological survey data, and the quality of the exposed rock surface should be checked. The next step of construction can only be carried out after joint confirmation with relevant parties; the excavation width should meet the design width requirements;

[0008] Step 4: When cutting the pile head on one side of the right cast-in-place pile, the cut pile surface should be 5cm higher than the designed pile top. Use a jackhammer or a professional pile cutter to break the pile head, and then manually chisel the pile top surface to expose the fresh concrete surface to enhance the connection with the connecting beam;

[0009] Step 5: Driving anchor rods at shallow foundation;

[0010] S1. On the shallow foundation side, the bottom surface of the foundation is generally uneven after excavation because the geological rock layer may change. Therefore, the bottom surface of the foundation needs to be leveled to form a leveling layer. The leveling layer uses plain concrete with a concrete grade of no less than C30. When the ground layer height difference is large, it is poured in layers, and the thickness of each layer is no more than 300mm.

[0011] S2. Drilling: Use a dedicated drilling machine or pneumatic drill to drill holes to form buried holes. The drilling depth should be no less than 1.5m and the diameter should be 1.25 times the diameter of the anchor rod. After drilling, clean the holes with water flushing.

[0012] S3. Bury anchor rods. The anchor rods shall be hot-rolled ribbed steel bars with a diameter of not less than Ф25 and coated with a hot-dip galvanized layer. The length of the anchor rods buried in the holes shall be not less than 1.5m, the exposed length shall be not less than 1.5m, and the bending length shall be not less than 0.3m.

[0013] S4, grouting; After the anchor is buried, it is temporarily fixed to maintain its verticality. Cement slurry or grouting material with a strength of not less than 30Mpa is used to grout the hole to form a fixed structure for fixing the anchor. The grouting should be full. During grouting, the verticality of the anchor 2 should be ensured to prevent tilting;

[0014] S5. The top elevation of the concrete leveling layer on the shallow foundation should be consistent with the bottom elevation of the connecting beam above the right span cast-in-place pile after the pile is cut, so as to ensure that the left and right spans are at the same elevation to facilitate the overall construction of the connecting beam. The top elevation of the connecting beam on the left and right spans should also be consistent.

[0015] S6. Construction of the connecting beam: Because the bottom surfaces of the left and right abutment foundations are on the same horizontal plane, the steel bar binding and concrete pouring work are carried out according to the structural dimensions and steel bar arrangement of the connecting beam;

[0016] S7, platform construction;

[0017] S8. When excavating the foundation, appropriate slope protection methods should be adopted in combination with the excavation depth. When the excavation depths of the left and right sections are inconsistent, the most unfavorable slope protection method should be adopted to improve the overall stability of the slope.

[0018] As a supplement to the technical solution described in the present invention, in S1, when the pouring thickness exceeds 400 mm, a steel mesh is added to improve the overall stability of the concrete, and a steel mesh with a diameter of 6 mm and a layout of 200 mm*200 mm is used as the structural layer, and the thickness of the protective layer is not less than 55 mm.

[0019] As a supplement to the technical solution described in the present invention, in the S7, the abutment body is constructed in an integral manner; first, the top surface of the connecting beam is roughened to expose the fresh concrete surface, and then the abutment body reinforcement is tied, the formwork is supported, and the concrete is poured; the abutment structure is set as an integral type, which can effectively withstand the load transmitted from the upper structure and the soil pressure behind the abutment.

[0020] As a supplement to the technical solution described in the present invention, in the above S8, the most unfavorable slope protection method adopts natural slope reduction, steel sheet pile or sandbag protection.

[0021] As a supplement to the technical solution described in the present invention, the anchor rods are processed in a processing plant and then transported to the site by a transport vehicle. They should be stacked neatly on site, not directly in contact with the bottom surface, and placed on a bracket to prevent the anchor rods from being contaminated or rusted.

[0022] Beneficial effects: The present invention relates to a construction method for an oblique abutment foundation that adopts a combination of cast-in-place piles and shallow foundations. Since the overall layout of the bridge is at a certain angle to the route direction, it is oblique and also passes under the local road. The abutment foundation is also arranged obliquely, and its foundation is divided into a left span and a right span. The left span adopts a shallow foundation treatment form, and the right span adopts a cast-in-place pile foundation structure. Then, the shallow foundation and the cast-in-place pile foundation are connected together by a connecting beam to form an integral foundation structure as the abutment foundation. The upper part is the abutment body, and the construction parts such as the abutment body, abutment cap, and wing walls are completed by an integral construction method. The present invention effectively solves the problem that when the geological surveys of the left and right spans of the abutment foundation are inconsistent or there are large differences, it is difficult to drill into the rock when only cast-in-place piles are used. It also avoids the problem that only shallow foundations affect the stress safety of the structure, or only shallow foundation structures affect the stress safety of the structure. The present invention optimizes the number of cast-in-place pile designs while ensuring the safety of the structural design, thereby reducing the construction cost. Compared with existing solutions, the patent of the present invention has the following advantages: 1) It optimizes the foundation design and reduces the project cost while ensuring the safety of the structural stress; 2) If all cast-in-place piles are used for construction, the drilling speed will be slow when encountering rocks in the later stage, and the hammer teeth will be severely damaged, which reduces the construction efficiency. The present invention can reduce the degree of mechanical wear; 3) It breaks through the problem of difficult foundation treatment for the left and right sides of a bridge abutment with different geological conditions, and adopts a method of jointly bearing stress on different foundation structures and constructing the connecting beam and the abutment body as a whole. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 This is a planar layout diagram of a bridge abutment foundation structure combining a shallow foundation and a cast-in-place pile foundation according to the present invention;

[0024] Figure 2 It is a schematic diagram of the shallow foundation anchoring arrangement of the present invention;

[0025] Figure 3 This is a schematic elevation diagram of a skew abutment structure using a combination of shallow foundation treatment and cast-in-place piles;

[0026] Figure 4 It is a side view schematic diagram of the skew abutment of the present invention using shallow foundation treatment.

[0027] Diagram: 1. Buried hole, 2. Anchor rod, 3. Leveling layer, 4. Concrete leveling layer, 5. Rock surface, 6. Fixed structure, 7. Route center line, 8. PVC pipe drain hole, 9. Connecting beam, 10. Cast-in-place pile, 11. Abutment body, 12. Construction joint, 13. Concrete cushion, 14. Elevation schematic line, 15. Bottom elevation, 16. Top elevation, 17. PVC drain pipe. DETAILED DESCRIPTION

[0028] Below in conjunction with specific embodiment, further set forth the present invention.Should be understood that these embodiments are only used to illustrate the present invention and are not used in limiting the scope of the present invention.In addition, should be understood that after reading the content taught by the present invention, those skilled in the art can make various changes or modifications to the present invention, and these equivalent forms fall equally within the scope limited by the appended claims of the application.

[0029] The embodiment of the present invention relates to a construction method for a skew bridge abutment foundation using a combination of cast-in-place piles and shallow foundations, such as Figure 1-4 As shown, the specific steps include:

[0030] Step 1: Construction of right span cast-in-place piles. The right span abutment structure foundation adopts a pile group design, with 6 piles in 2 rows. The number of cast-in-place piles will be increased or decreased according to the route width, abutment foundation width, abutment height, abutment back soil pressure, and structural load design requirements. The cast-in-place piles are drilled using the punching method and the concrete is poured using underwater concrete pouring. The pile top surface is designed to be overfilled by at least 1m to ensure the quality of the concrete at the pile top.

[0031] Step 2: Excavate the foundation pit, cut the pile heads, and dig a shallow foundation. After the right-side cast-in-place pile construction is completed and the pile body integrity quality inspection is passed, the next step is to arrange the pile head cutting work. Because the left-side foundation is shallow, the method of post-construction should be selected. If the shallow foundation is constructed first, the foundation pit excavation will disturb the adjacent soil, affecting the construction quality and safety of the cast-in-place piles. Therefore, the left and right foundation pits are excavated simultaneously and the connecting beam 9 is constructed at the same time.

[0032] Step 3: When excavating the foundation pit, the bottom surface of the foundation pit on the left shallow foundation side should be excavated to rock layer level 5. The rock surface should be compared with the geological survey data, and the quality of the exposed rock surface should be checked. The next step of construction can only be carried out after joint confirmation with relevant parties; the excavation width should meet the design width requirements;

[0033] Step 4: When cutting the pile head on one side of the right cast-in-place pile, the cut pile surface should be 5 cm higher than the designed pile top. Use a jackhammer or a professional pile cutter to break the pile head, and then manually chisel the pile top surface to expose the fresh concrete surface to enhance the connection with the connecting beam 9;

[0034] Step 5: Driving anchor rod 2 at the shallow foundation;

[0035] S1. On the shallow foundation side, the bottom surface of the foundation is generally uneven after excavation because the geological rock layer may change. Therefore, the bottom surface of the foundation needs to be leveled to form a leveling layer 3. The leveling layer uses plain concrete with a concrete grade of no less than C30. When the ground layer height difference is large, it is poured in layers, and the thickness of each layer is no more than 300mm.

[0036] S2. Drilling: Use a dedicated drilling machine or pneumatic drill to drill to form the buried hole 1. The drilling depth should be no less than 1.5m and the diameter should be 1.25 times the diameter of the anchor rod 2. After drilling, clean the hole of debris by water flushing.

[0037] S3. Bury anchor rod 2. The anchor rod 2 is made of hot-rolled ribbed steel bar with a diameter of not less than Φ25 and coated with a hot-dip galvanized layer. The length of the anchor rod buried in the burial hole 1 is not less than 1.5m, the exposed length is not less than 1.5m, and the bending length and anchor end anchor length are not less than 0.3m.

[0038] S4, grouting; after the anchor rod 2 is buried, it is temporarily fixed to maintain its verticality. Cement slurry or a grouting material with a strength of not less than 30Mpa is used to grout the hole to form a fixed structure 6 for fixing the anchor rod 2. The grouting should be full. The verticality of the anchor rod 2 should be ensured during grouting to prevent tilting.

[0039] S5. The top elevation of the concrete leveling layer 4 on the shallow foundation should be consistent with the bottom elevation 15 of the connecting beam 9 on the upper part of the right span after the cast-in-place pile is cut, so as to ensure that the left and right spans are at the same elevation to facilitate the overall construction of the connecting beam 9; the top elevation 16 of the connecting beam 9 on the left and right spans should also be consistent;

[0040] S6. Construction of connecting beam 9: Since the bottom surfaces of the left and right foundations of the abutment are on the same horizontal plane, steel bar binding and concrete pouring are carried out according to the structural dimensions and steel bar arrangement of connecting beam 9.

[0041] S7. Abutment construction: The abutment 11 is constructed in an integral manner. First, the top surface of the connecting beam 9 is roughened to expose the fresh concrete surface. Then, the reinforcement of the abutment 11 is tied, the formwork is set up, and the concrete is poured. The abutment structure is designed as a whole, which can effectively withstand the load transmitted from the superstructure and the soil pressure behind the abutment.

[0042] S8. When excavating the foundation, appropriate slope protection methods should be adopted in combination with the excavation depth. When the excavation depths of the left and right sides are inconsistent, the most unfavorable slope protection method (natural slope reduction, steel sheet piles or sandbag protection) should be adopted to improve the overall stability of the slope.

[0043] In the above S1, when the pouring thickness exceeds 400mm, a steel mesh is added to improve the overall stability of the concrete. A steel mesh with a diameter of 6mm and a layout of 200mm*200mm is used as the structural layer, and the thickness of the protective layer is not less than 55mm.

[0044] The anchor rods 2 are processed in a processing plant and then transported to the site by a transport vehicle. They should be neatly stacked on site and cannot directly contact the bottom surface. They should be placed on a bracket to prevent the anchor rods 2 from being contaminated or rusted.

[0045] The overall layout of the bridge in the present invention is at a certain angle to the direction of the route, and is oblique, and also passes under the local road; the layout of the abutment foundation is also oblique, and its foundation is divided into a left and a right span. The left span adopts a shallow foundation treatment form, and the right span adopts a cast-in-place pile foundation structure. Then, the shallow foundation and the cast-in-place pile foundation use a connecting beam to connect the left and right span foundations together to form an integral foundation structure form, which serves as the abutment foundation; its upper part is the abutment body, and an integral construction method is used to complete the abutment body, abutment cap, wing wall and other construction parts. The present invention effectively solves the problem that when the geological surveys of the left and right spans of the abutment foundation are inconsistent or there are large differences, it is difficult to drill into the rock when only cast-in-place piles are used. It also avoids the problem that only shallow foundation forms affect the stress safety of the structure, or only shallow foundation structures affect the stress safety of the structure. The present invention optimizes the number of cast-in-place pile designs while ensuring the safety of the structural design, and reduces the construction cost.

[0046] In the description of the present invention, it should be understood that the directions or positional relationships indicated by directional words such as "front, back, up, down, left, right", "horizontal, vertical, perpendicular, horizontal" and "top, bottom" are usually based on the directions or positional relationships shown in the accompanying drawings. They are only for the convenience of describing the present invention and simplifying the description. Unless otherwise specified, these directional words do not indicate or imply that the device or element referred to must have a specific direction or be constructed and operated in a specific direction. Therefore, they cannot be understood as limiting the scope of protection of the present invention; the directional words "inside and outside" refer to the inside and outside relative to the outline of each component itself.

[0047] For ease of description, spatially relative terms such as "above", "above", "on the upper surface of", "above", etc. may be used herein to describe the spatial positional relationship of a device or feature to other devices or features as shown in the figures. It should be understood that spatially relative terms are intended to include different orientations of the device in use or operation in addition to the orientation described in the figures. For example, if the device in the drawings is inverted, the device described as "above other devices or structures" or "above other devices or structures" will be positioned as "below other devices or structures" or "below other devices or structures". Thus, the exemplary term "above" can include both "above" and "below". The device can also be positioned in other different ways (rotated 90 degrees or in other orientations), and the spatially relative descriptions used here are interpreted accordingly.

[0048] In addition, it should be noted that the use of terms such as "first" and "second" to limit components is only for the convenience of distinguishing the corresponding components. Unless otherwise stated, the above terms have no special meaning and therefore cannot be understood as limiting the scope of protection of the present invention.

[0049] The above is a detailed introduction to the construction method of the skew abutment foundation provided by the present application, which adopts a combination of cast-in-place piles and shallow foundations. Specific examples are used in this article to illustrate the principles and implementation methods of the present application. The description of the above embodiments is only used to help understand the method of the present application and its core idea. At the same time, for general technical personnel in this field, according to the ideas of the present application, there will be changes in the specific implementation methods and application scope. In summary, the content of this specification should not be understood as limiting the present application.

Claims

1. A construction method for a skew abutment foundation using a combination of cast-in-place piles and shallow foundations, characterized by: The specific steps include: Step 1: Construction of right span cast-in-place piles. The right span abutment foundation adopts a pile group design with 6 piles in 2 rows. The number of cast-in-place piles will be increased or decreased according to the route width, abutment foundation width, abutment height, abutment back soil pressure, and structural load design requirements. The cast-in-place piles are drilled using the punching method and the concrete is poured using underwater concrete pouring. The pile top surface is designed to be overfilled by at least 1m to ensure the quality of the pile top concrete. Step 2: Excavate the foundation pit, cut the pile heads, and dig a shallow foundation; After the right-side cast-in-place pile construction is completed and the pile body integrity quality inspection is passed, the next step is to arrange the pile head cutting work; because the left side has a shallow foundation, the method of post-construction should be selected. If the shallow foundation is constructed first, the foundation pit excavation will disturb the adjacent soil, affecting the construction quality and safety of the cast-in-place piles. Therefore, the excavation of the left and right side foundation pits adopts the method of simultaneous excavation and construction of connecting beams; Step 3: When excavating the foundation pit, the bottom surface of the foundation pit on the left shallow foundation side should be excavated to the rock surface. The rock surface should be compared with the geological survey data, and the quality of the exposed rock surface should be checked. The next step of construction can only be carried out after joint confirmation with relevant parties; the excavation width should meet the design width requirements; Step 4: When cutting the pile head on one side of the right cast-in-place pile, the cut pile surface should be 5cm higher than the designed pile top. Use a jackhammer or a professional pile cutter to break the pile head, and then manually chisel the pile top surface to expose the fresh concrete surface to enhance the connection with the connecting beam; Step 5: Driving anchor rods at shallow foundation; S1. On the shallow foundation side, the bottom surface of the foundation is uneven after excavation. Due to the changes in the geological rock layer, the bottom surface of the foundation needs to be leveled to form a leveling layer. The leveling layer uses plain concrete with a concrete grade of no less than C30. When the ground layer height difference is large, it is poured in layers, and the thickness of each layer is no more than 300mm. S2. Drilling: Use a dedicated drilling machine or pneumatic drill to drill holes to form buried holes. The drilling depth should be no less than 1.5m and the diameter should be 1.25 times the diameter of the anchor rod. After drilling, clean the holes with water flushing. S3. Bury anchor rods. The anchor rods shall be hot-rolled ribbed steel bars with a diameter of not less than Ф25 and coated with a hot-dip galvanized layer. The length of the anchor rods buried in the holes shall be not less than 1.5m, the exposed length shall be not less than 1.5m, and the bending length shall be not less than 0.3m. S4. Grouting: After the anchor is buried, it is temporarily fixed to maintain its verticality. Grouting material with a strength of not less than 30Mpa is used to grout the hole to form a fixed structure for the anchor. The grouting should be full and the verticality of the anchor should be ensured during grouting to prevent tilting. S5. The top elevation of the concrete leveling layer on the shallow foundation should be consistent with the bottom elevation of the connecting beam above the right span cast-in-place pile after the pile is cut, so as to ensure that the left and right spans are at the same elevation to facilitate the overall construction of the connecting beam. The top elevation of the connecting beam on the left and right spans should also be consistent. S6. Construction of the connecting beam: Because the bottom surfaces of the left and right abutment foundations are on the same horizontal plane, the steel bar binding and concrete pouring work are carried out according to the structural dimensions and steel bar arrangement of the connecting beam. S7, platform construction; S8. When excavating the foundation, appropriate slope protection methods should be adopted in combination with the excavation depth. When the excavation depths of the left and right sections are inconsistent, the most unfavorable slope protection method should be adopted to improve the overall stability of the slope.

2. The skew bridge abutment foundation according to claim 1 adopts a construction method combining cast-in-place piles and shallow foundations, characterized in that: In the above S1, when the pouring thickness exceeds 400mm, a steel mesh is added to improve the overall stability of the concrete. A steel mesh with a diameter of 6mm and a layout of 200mm*200mm is used as the structural layer, and the thickness of the protective layer is not less than 55mm.

3. The skew bridge abutment foundation according to claim 1 is constructed using a method combining cast-in-place piles with a shallow foundation, characterized in that: In the above-mentioned S7, the abutment body is constructed in an integral manner; first, the top surface of the connecting beam is roughened to expose the fresh concrete surface, and then the abutment body reinforcement is tied, the formwork is supported, and the concrete is poured.

4. The skew bridge abutment foundation according to claim 1 is constructed using a method combining cast-in-place piles with a shallow foundation, characterized in that: In the above-mentioned S8, the most unfavorable slope protection method is to use natural slope reduction, steel sheet pile or sandbag protection.

5. The skew bridge abutment foundation according to claim 1 adopts a construction method combining cast-in-place piles and shallow foundations, characterized in that: The anchor rods are processed in a processing plant and then transported to the site by a transport vehicle. They should be neatly stacked on site, not directly touching the bottom surface, and placed on a bracket to prevent the anchor rods from being contaminated or rusted.

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