A method for vertical-first and then oblique excavation of a super-large-section abutment foundation on a strong unloading zone stratum

Abstract

The present invention discloses a method for excavating a super-large-section arch foundation on a strong unloading zone stratum vertically first and then obliquely. The arch foundation and the pier foundation connected thereto are excavated simultaneously, and the overall excavation sequence is from top to bottom; the vertical pier foundation is excavated first, which provides a work platform for subsequent construction; when the vertical pier foundation is excavated, part of the arch foundation in the same horizontal plane is excavated synchronously; and then the remaining arch foundation is excavated. The present invention first excavates the vertical pier foundation to solve the problem of no construction access road on site, provides a work platform for subsequent construction, reduces the construction difficulty, and improves the construction efficiency; when vertically excavating, the slope protection of the strong unloading zone stratum is simultaneously strengthened to ensure the safety and reliability of the excavation process, and greatly improves the excavation construction efficiency of the super-large-section arch and pier foundation.

Description

Technical Field

[0001] The present invention relates to the technical field of large-span arch bridge construction, and more specifically, to a method for first vertically and then obliquely excavating a super-large-section arch seat foundation on a strong unloading zone stratum. Background Art

[0002] In the plateau and mountainous areas of my country with harsh natural environments, the engineering geological performance is poor, the terrain is undulating, most of the bedrock is exposed, and the protruding rock mass is mostly strong unloading fracture zone rock mass. Under such geological conditions, large-span arch bridges are often used as the main passages across rivers or deep canyons. As the most important lower structure of the arch bridge, the arch seat foundation needs to pass through the strong unloading fracture zone to enter the stable rock mass to ensure the safety of the bridge structure. Therefore, the arch seat foundation usually adopts an integral embedded inclined arch seat foundation. This form of arch seat foundation has the characteristics of large excavation cross-sectional area, deep excavation depth, and large excavation slope. At the same time, due to the structural characteristics of the arch bridge, the arch seat foundation is connected to the pier or the pier foundation of the building on the arch. When excavating the arch seat foundation, it is necessary to consider the influence of the pier foundation construction process.

[0003] When excavating an ultra-large cross-section, large-angle inclined arch foundation with an excavation cross-sectional area greater than 100 square meters and a vertical inclination angle of about 45°, appropriate excavation methods and engineering measures must be adopted to ensure rock stability and work safety during the arch foundation excavation construction. In the existing domestic construction technology, the construction of the arch bridge arch and pier foundation is mostly carried out separately, with the arch foundation excavation and pouring construction being carried out first, and then the pier excavation and pouring construction being carried out. The foundation is mostly excavated in steps by combining manual drilling and blasting with small mechanical excavators. However, the above excavation method has the following four defects and shortcomings: (1) The arch and pier foundations are excavated and poured separately, the construction process is alternated many times, and the replacement of on-site equipment and resource configuration increases the difficulty of construction organization. (2) The process connection is unreasonable, and the concrete age difference between the arch and pier foundations is large, which is not conducive to the overall stress of the structure. (3) When the arch foundation is excavated obliquely first, there is no existing construction road, and it is difficult for equipment and resources to enter the site, making oblique excavation construction more difficult. In addition, there are fewer working surfaces, and the mechanized construction efficiency and slag discharge efficiency are low. (4) The integrity of the slope rock is poor, there are cracks and fractures and strong unloading zone geology, and no effective and appropriate slope reinforcement measures were taken before the oblique excavation of the arch foundation, resulting in a high safety risk during the excavation construction process.

[0004] In view of the above problems, it is urgent to develop a construction method for excavating super-large-section arch and pier foundations on strong unloading zone strata to ensure that the excavation of arch and pier foundations is completed safely and efficiently. Summary of the invention

[0005] One purpose of the present invention is to provide a method for excavating a super-large-section arch seat foundation on a strong unloading zone stratum vertically first and then obliquely, which is suitable for the construction and excavation of the arch seat and the connected pier seat foundation. The vertical pier seat foundation is first excavated to solve the problem of no construction access road on site, provide a work platform for subsequent construction, reduce the construction difficulty, and improve construction efficiency; during vertical excavation, the slope protection of the strong unloading zone stratum is simultaneously strengthened to ensure the safety and reliability of the excavation process, and greatly improve the excavation construction efficiency of the super-large-section arch seat and pier seat foundation.

[0006] In order to solve the above technical problems, the present invention provides a method for excavating a super-large-section arch seat foundation on a strong unloading zone stratum vertically first and then obliquely, wherein the arch seat foundation and the pier seat foundation connected thereto are excavated simultaneously, and the overall excavation sequence is from top to bottom; the vertical pier seat foundation is excavated first, which provides a working platform for subsequent construction; when the vertical pier seat foundation is excavated, part of the arch seat foundation in the same horizontal plane is excavated synchronously; and then the remaining arch seat foundation is excavated.

[0007] Preferably, horizontal layered excavation is adopted when the vertical pier foundation and part of the arch foundation in the same horizontal plane are excavated simultaneously, with each layer excavation height of 1.0~2.0 meters, and the excavation is gradually carried out from the outside to the mountain side; after each layer excavation is completed, slope protection construction is carried out simultaneously.

[0008] Preferably, when excavating the remaining arch seat foundation, the remaining arch seat foundation is divided into two parts, namely the outer part and the mountain side part. The arch seat foundation of the outer part is excavated in horizontal layers, and the excavation height of each layer is 2.0~3.0 meters; the arch seat foundation of the mountain side is excavated in steps and layers, and the vertical excavation height of each step is designed to be 2.5~3.0 meters, and the excavation depth of each layer is designed to be 2.5~3.0 meters; after each layer is excavated, slope protection construction is carried out simultaneously.

[0009] Preferably, the outer part of the arch foundation and the part of the arch foundation on the mountain side are excavated at the same time; after each layer of excavation is completed, the slope protection construction is carried out simultaneously.

[0010] Preferably, the excavation depth of the outer part of the abutment foundation is one layer earlier than that of the part of the abutment foundation on the mountain side, so as to ensure smooth excavation and slag removal of the part of the abutment foundation on the mountain side.

[0011] Preferably, the partial arch seat foundation on the mountain side is divided into multiple steps and multiple deep excavation layers by excavation layering lines and excavation step lines that are perpendicular to and parallel to the arch seat contour line and staggered horizontally and vertically. When excavating the partial arch seat foundation on the mountain side, the cross section is horizontally divided into three excavation working surfaces. The excavation depths of step 1 close to the arch seat contour line of the three horizontal excavation working surfaces are the same, and the excavation depths of the middle working surfaces of the remaining steps lag behind the working surfaces on both sides.

[0012] Preferably, when excavating the arch foundation on the mountain side, step one is always excavated first, and then other steps are excavated in sequence to ensure that the depth of step one is the deepest. After step one is excavated, slope protection construction is immediately carried out to form an advanced support structure for the cave roof.

[0013] Preferably, when excavating the partial abutment foundation on the mountain side, the number of excavation steps and the number of excavation layers per step are increased sequentially; and at the same time, the layered excavation of the partial abutment foundation on the outer side is carried out synchronously.

[0014] Preferably, specifically: first, excavate the first layer of step one and step two of the arch seat foundation on the mountain side in turn, with a depth of 1.0~2.0 meters, and the excavation depth of the remaining steps is 2.5~3.0 meters, and the first layer of the outer part of the arch seat foundation is excavated synchronously; secondly, excavate three layers of step one obliquely into the hole, and complete the excavation of the first layer of the outer part of the arch seat foundation at the same time; thirdly, excavate multiple layers of step one, step two, and step three obliquely into the hole, and complete the excavation of the second layer of the outer part of the arch seat foundation at the same time; then, continue to excavate multiple layers of step one, step two, and step three obliquely into the hole; then, repeat the above steps, excavate the number of steps and the number of steps increased in turn, and simultaneously carry out layered excavation of the outer part of the arch seat foundation until all excavation is completed.

[0015] Preferably, the slope protection construction includes: simultaneously carrying out the construction of internal support and shotcrete support of the excavation section steel arch frame during excavation, and constructing prestressed anchor cable protection at the same time.

[0016] The present invention has at least the following beneficial effects:

[0017] (1) The arch and pier foundations are excavated at the same time, and can be poured and constructed in a unified manner later. The process connection is reasonable, the alternation of construction processes is reduced, and the difficulty of organizing on-site equipment and resources is reduced.

[0018] (2) The arch seat and pier seat are cast continuously to avoid a large difference in foundation age, reduce the risk of concrete cracking at the junction of the arch seat and pier seat, and ensure that the overall stress performance of the foundation concrete structure is good.

[0019] (3) The excavation sequence is from top to bottom, first excavating the pier shaft foundation and then the arch shaft foundation. When excavating the pier shaft foundation, the internal support and prestressed anchor cable protection of the excavation section are carried out simultaneously to improve the stability of the slope and provide safety guarantee for subsequent construction.

[0020] (4) The excavation of the pier shaft foundation is completed, which can provide a construction platform for the subsequent excavation of the arch seat inclined shaft, facilitate the operation of mechanical construction such as excavators, and reduce the difficulty of the inclined shaft construction.

[0021] (5) Sections ② and ③ can be excavated and constructed simultaneously, thus increasing the overall construction area and improving excavation efficiency.

[0022] (6) The excavation of part ③ adopts a multi-step and multi-working surface construction method and forms an advanced support structure on the top of the tunnel to improve the efficiency of mechanized construction, while ensuring construction safety and accelerating the construction progress.

[0023] Other advantages, objectives and features of the present invention will be embodied in part through the following description, and in part will be understood by those skilled in the art through study and practice of the present invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 It is a schematic diagram of the substructure of the arch seat and pier seat foundation excavation of the present invention;

[0025] Figure 2 Schematic diagram of the vertical excavation of the abutment and pier foundation of the present invention Figure 1 ;

[0026] Figure 3 Schematic diagram of the vertical excavation of the abutment and pier foundation of the present invention Figure 2 ;

[0027] Figure 4 This is a schematic diagram of excavation of the corner area where part ① and part ② of the present invention meet;

[0028] Figure 5 It is a schematic diagram of the excavation section of the corner area where the parts ① and ② of the present invention meet;

[0029] Figure 6 This is a schematic diagram of the oblique excavation of the step ③ of the present invention;

[0030] Figure 7 This is a schematic diagram of the oblique excavation of steps 1 to 3 of the present invention;

[0031] Figure 8 This is a cross-sectional view of the oblique excavation of steps 1 to 3 of the present invention;

[0032] Fig. 9 The steps 1 to 3 of the third part of the present invention are excavated and deepened obliquely;

[0033] Fig.10 This is a schematic diagram of the oblique excavation of steps 1 to 5 of step ③ of the present invention;

[0034] Fig.11 This is a cross-sectional view of the oblique tunnel excavation of steps 1 to 5 of part ③ of the present invention;

[0035] Fig.12 This is a schematic diagram of the oblique excavation of steps 1 to 6 of step ③ of the present invention;

[0036] Fig.13 This is a cross-sectional view of the oblique tunnel excavation of steps 1 to 6 of part ③ of the present invention;

[0037] Fig.14 This is a schematic diagram of the oblique excavation of steps 1 to 8 of step ③ of the present invention;

[0038] Fig.15 This is a schematic diagram of the oblique excavation of the remaining steps of part ③ of the present invention Figure 1 ;

[0039] Fig.16 This is a schematic diagram of the oblique excavation of the remaining steps of part ③ of the present invention Figure 2 .

[0040] Description of reference numerals:

[0041] 1. Pier foundation, 2. Arch foundation, 3. Slope line, 4. Excavation layer line, 5. Excavation step line, 6. Pier contour line, 7. Arch contour line, 8. Step one, 9. Step two, 10. Step three, 11. Step four, 12. Step five, 13. Step six. DETAILED DESCRIPTION

[0042] In order to better understand the purpose, structure and function of the present invention, the present invention is further described in detail below in conjunction with the accompanying drawings so that those skilled in the art can implement it according to the description.

[0043] It should be noted that the experimental methods described in the following embodiments are conventional methods unless otherwise specified, and the reagents and materials are commercially available unless otherwise specified; in the description of the present invention, the terms "lateral", "longitudinal", "upper", "lower", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside" and the like indicate orientations or positional relationships based on the orientations or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as a limitation on the present invention.

[0044] like Figure 1 Shown is the excavation division of the arch seat and pier foundation.

[0045] The invention discloses a method for excavating a super-large-section arch foundation on a strong unloading zone stratum vertically and then obliquely. The excavation sequence is from top to bottom. First, vertical and horizontal construction is carried out to excavate the pier and part of the arch foundation; then, the arch foundation is excavated in steps and layers. During the foundation excavation, the steel arch frame internal support and the excavation surface sprayed concrete support construction are carried out simultaneously.

[0046] The excavation of the arch and pier foundation is mainly divided into three parts, such as Figure 1As shown in the figure, the pier foundation 1 and the partial arch foundation 2 in the same plane as the pier foundation are defined as the first part to be excavated, that is, the vertical pier foundation and the partial arch foundation in the same horizontal plane. The slope line 3 is shown in the figure; the remaining arch foundation is divided into part 2 (partial arch foundation on the outside) and part 3 (partial arch foundation on the mountain side) from top to bottom and from outside to inside. First excavate part 1, which is the pier and partial arch foundation. Horizontal layered excavation is adopted, and the excavation height of each layer is 1.0~2.0 meters. It is gradually excavated from the outside of the slope line 3 to the mountain side. After each layer of excavation is completed, the internal support of the steel arch frame is constructed simultaneously. Part 2 is a partial arch foundation, which is also excavated horizontally in layers, and the excavation height of each layer is 2.0~3.0 meters. The arch foundation of part 3 is constructed by step-by-step layered inclined excavation. The height of each vertical step is designed to be 2.5~3.0 meters, and the depth of each layer is designed to be 2.5~3.0 meters. Parts ② and ③ are excavated simultaneously, and after each layer of excavation is completed, the internal supports of the steel arch frame are constructed simultaneously.

[0047] When the ② and ③ parts are ready for excavation, the excavation depth of the ② part is one layer ahead of the ③ part to ensure the smooth excavation of the slag in the ③ part. When the ③ part is excavated, it is excavated in steps and layers from top to bottom. When the ③ part is excavated, the cross section is divided into 3 excavation working surfaces horizontally. The excavation depth of the first step of the three horizontal working surfaces is the same. The excavation depth of the second step of the middle working surface lags behind the working surfaces on both sides, and it is ensured that the excavation of the first step is ahead of the other steps. The number of excavation steps and the number of excavation layers of each step are increased in sequence to complete the excavation of the ③ part.

[0048] After the excavation is completed, the pier base outline 6 and the abutment base outline 7 are formed on the mountain side. Specific embodiment:

[0050] (1) Step 1: ① Partial excavation and strengthening of slope support.

[0051] like Figure 2 and Figure 3 As shown, the arch and pier foundations are excavated by excavators. The pier and part of the arch foundations are excavated by horizontal layers. Figure 2 The excavation layer line 4 is shown in the figure. The excavation height of each layer is 1.0~2.0 meters, and the excavation is gradually carried out from the outside to the mountain side. After each layer of excavation is completed, the steel arch frame internal support and shotcrete support construction of the excavation surface are carried out simultaneously, and prestressed anchor cables are constructed at the same time to strengthen the slope protection. Until the horizontal layered excavation construction of the entire part ① is completed.

[0052] (2) Step 2: Excavate the corner area where parts ③ and ② meet.

[0053] like Figure 4 and Figure 5As shown, the arch foundation of part ③ is constructed by step-by-step and layered inclined excavation. The dividing line of part ③ perpendicular to the arch contour line is defined as excavation layer line 4, and the dividing line parallel to the arch contour line is defined as excavation step line 5; the vertical excavation height of each step is 2.5~3.0 meters, that is, the spacing between adjacent excavation step lines is 2.5~3.0 meters; the foundation is layered in depth, the first layer is 1.0~2.0 meters deep to ensure that the steel arch frame internal support can be constructed, and the excavation depth of each layer is 2.5~3.0 meters, that is, the spacing between adjacent excavation layer lines is 2.5~3.0 meters. Part ② is a partial arch foundation, which also adopts horizontal layered excavation, and the excavation height of each layer is 2.5~3.0 meters.

[0054] When excavating the corner area where part ③ and part ② meet, first excavate the first layer (that is, the first layer of the layers from top to bottom formed by multiple excavation layers) of step 1 8 (that is, the step between the excavation step line closest to the arch seat contour line and the arch seat contour line) and step 2 9 (that is, the step between the excavation step line closest to the arch seat contour line and the adjacent second excavation step line, from the arch seat contour line outward, step 1, step 2, step 3...) of part ③ in sequence, and excavate the first layer of part ② at the same time. After the excavation of the first layer of step 1 of part ③ is completed, the steel arch frame internal support is constructed immediately. When excavating part ③, the cross section is divided into three excavation working surfaces horizontally, and the excavation depth of step 1 of the three horizontal working surfaces is ensured to be the same, and the excavation depth of step 2 of the middle working surface lags behind the working surfaces on both sides, so as to ensure that step 1 is excavated ahead of other steps and the depth is always the deepest. The purpose of this is to immediately carry out the steel arch frame internal support construction after each layer of step 1 is excavated, forming a cave top advance support structure to ensure construction safety.

[0055] (3) Step 3: Dig the third step diagonally into the hole.

[0056] like Figure 6 As shown in the figure, the step 1 of part ③ is excavated in an oblique direction into the hole for 3 layers, and the first layer of part ② is excavated at the same time. The internal support of the steel arch frame is constructed synchronously during the excavation of parts ③ and ②.

[0057] (4) Step 4: Dig steps 1 to 3 obliquely into the cave.

[0058] like Figure 7 and Figure 8 As shown, three working surfaces are excavated synchronously in an oblique manner to construct Section ③. Step 1 8 is excavated to add 3 layers, Step 2 9 is excavated to add 3 layers, and Step 3 10 is excavated to add 2 layers. At the same time, the second layer of Section ② is excavated. The internal support of the steel arch is constructed synchronously during the excavation of Section ③ and Section ②.

[0059] (5) Step 5: Steps 1 to 3 of step ③ are excavated diagonally to deepen the tunnel.

[0060] like Fig. 9As shown, the number of layers of the oblique tunnel from step 1 to step 3 in step ③ is further deepened, among which step 1 excavation adds 3 layers, step 2 excavation adds 3 layers, and step 3 excavation adds 2 layers. During the excavation of step ③, the internal support of the steel arch frame is constructed simultaneously.

[0061] (6) Step 6: Steps 1 to 5 of step ③ are excavated diagonally to deepen the tunnel.

[0062] like Fig.10 and Fig.11 As shown, further deepen the vertical excavation of part ③ to step 4 11 and step 5 12, and increase the number of excavation layers of each step by 1 to 3 layers. At the same time, excavate the third layer of part ②. During the excavation of parts ③ and ②, the internal support of the steel arch frame is constructed simultaneously.

[0063] (7) Step 7: Steps 1 to 6 of step ③ are excavated obliquely to deepen the tunnel.

[0064] like Fig.12 and Fig.13 As shown, further deepen the vertical excavation of part ③ to step 6 13, and increase the number of excavation layers of each step by 1 to 4 layers. At the same time, carry out partial excavation of the fourth layer of part ② to ensure the slag discharge channel of part ③. During the excavation of parts ③ and ②, the internal support of the steel arch frame is constructed simultaneously.

[0065] (8) Step 8: Steps 1 to 8 of step 3 are excavated diagonally to deepen the tunnel.

[0066] like Fig.14 As shown, further deepen the vertical excavation of part ③ to step 8, and increase the number of excavation layers of each step by 1 to 4 layers. At the same time, excavate the remaining part of part ② to ensure the slag discharge channel of part ③. During the excavation of parts ③ and ②, the internal support of the steel arch frame is constructed simultaneously.

[0067] (9) Step 9: Steps 1 to 8 of step ③ are excavated diagonally to deepen the tunnel.

[0068] like Fig.15 and Fig.16 As shown, gradually deepen the vertical excavation steps of part ③ and the number of excavation layers of each step to complete the excavation of the remaining part of part ③. During the excavation, the internal support of the steel arch frame is constructed simultaneously.

[0069] It is understood that the present invention is described by some embodiments, and those skilled in the art are aware that various changes or equivalent substitutions may be made to these features and embodiments without departing from the spirit and scope of the present invention. Although the embodiments of the present invention have been disclosed as above, they are not limited to the applications listed in the specification and the implementation mode, and they can be fully applied to various fields suitable for the present invention. For those familiar with the art, other modifications can be easily implemented, so without departing from the general concept defined by the claims and the equivalent scope, the present invention is not limited to the specific details and the illustrations shown and described here.

Claims

1. A method for excavating a super-large-section abutment foundation vertically and then obliquely on a strong unloading zone stratum, characterized in that: The arch foundation and the pier foundation connected to it are excavated at the same time, and the overall excavation order is from top to bottom; the vertical pier foundation is excavated first, which provides a working platform for subsequent construction; when the vertical pier foundation is excavated, part of the arch foundation in the same horizontal plane is excavated simultaneously; then the rest of the arch foundation is excavated; When the vertical pier foundation and part of the arch foundation in the same horizontal plane are excavated simultaneously, horizontal layered excavation is adopted. The excavation height of each layer is 1.0~2.0 meters, and the excavation is gradually carried out from the outside to the mountain side. After each layer of excavation is completed, the slope protection construction is carried out simultaneously; When excavating the remaining arch foundation, the remaining arch foundation is divided into two parts, namely the outer part and the mountain side part. The arch foundation of the outer part is excavated in horizontal layers, and the excavation height of each layer is 2.0~3.0 meters; the arch foundation of the mountain side is excavated in steps and layers. The vertical excavation height of each step is designed to be 2.5~3.0 meters, and the excavation depth of each layer is designed to be 2.5~3.0 meters; after the excavation of each layer is completed, slope protection construction is carried out simultaneously.

2. The method for excavating a super-large-section abutment foundation vertically and then obliquely on a strong unloading zone stratum according to claim 1 is characterized in that: The outer part of the arch foundation and the part of the arch foundation on the mountain side are excavated at the same time; after each layer of excavation is completed, slope protection construction is carried out simultaneously.

3. The method for excavating a super-large-section abutment foundation vertically and then obliquely on a strong unloading zone stratum according to claim 2 is characterized in that: The excavation depth of the outer part of the arch seat foundation is one layer earlier than that of the arch seat foundation on the mountain side, ensuring smooth excavation and slag removal of the arch seat foundation on the mountain side.

4. The method for excavating a super-large-section abutment foundation vertically and then obliquely on a strong unloading zone stratum according to claim 1, characterized in that: The partial arch seat foundation on the mountain side is divided into multiple steps and multiple deep excavation layers through the excavation layering lines and excavation step lines that are perpendicular to and parallel to the arch seat contour line and staggered horizontally and vertically. When excavating the partial arch seat foundation on the mountain side, the cross section is horizontally divided into three excavation working surfaces. The excavation depths of step 1 close to the arch seat contour line of the three horizontal excavation working surfaces are the same, and the excavation depths of the middle working surfaces of the remaining steps lag behind the working surfaces on both sides.

5. The method for excavating a super-large-section abutment foundation vertically and then obliquely on a strong unloading zone stratum according to claim 4 is characterized in that: When excavating the arch foundation on the mountain side, always excavate step one first, and then excavate other steps in sequence to ensure that the depth of step one is the deepest. After the excavation of step one, slope protection construction is carried out immediately to form an advanced support structure for the cave roof.

6. The method for excavating a super-large-section abutment foundation vertically and then obliquely on a strong unloading zone stratum as claimed in claim 5, characterized in that: When excavating the arch foundation on the mountain side, increase the number of excavation steps and the number of excavation layers per step in sequence; at the same time, carry out layered excavation of the outer arch foundation simultaneously.

7. The method for excavating a super-large-section abutment foundation vertically and then obliquely on a strong unloading zone stratum according to claim 6, characterized in that: Specifically: first, excavate the first layer of step one and step two of the arch seat foundation on the mountain side in turn, with a depth of 1.0~2.0 meters, and the excavation depth of the remaining steps is 2.5~3.0 meters, and the first layer of the outer arch seat foundation is excavated synchronously; secondly, excavate three layers of step one obliquely into the hole, and complete the excavation of the first layer of the outer arch seat foundation at the same time; thirdly, excavate multiple layers of step one, step two, and step three obliquely into the hole, and complete the excavation of the second layer of the outer arch seat foundation at the same time; then, continue to excavate multiple layers of step one, step two, and step three obliquely into the hole; then, repeat the above steps, excavate the number of steps and the number of steps increased in turn, and simultaneously carry out layered excavation of the outer arch seat foundation until all excavation is completed.

8. The method for excavating a super-large-section abutment foundation vertically and then obliquely on a strong unloading zone stratum according to any one of claims 1 to 7, characterized in that: Slope protection construction includes: simultaneous construction of steel arch internal support and shotcrete support for the excavation section during excavation, and construction of prestressed anchor cable protection.

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