A ring-shaped underground continuous wall foundation for a long-span arch bridge in a thick overburden area

Abstract

The patent of the present invention proposes a circular underground continuous wall foundation for a large-span arch bridge in a deep overburden area, which belongs to the field of geotechnical engineering. It includes a circular underground continuous wall, a cap beam, an inner lining wall, a bottom plate, an arch seat, a cover plate and a pile foundation; the circular underground continuous wall includes a phase I trough section and a phase II trough section, and the phase I trough section and the phase II trough section are alternately connected to form a ring; the cap beam is arranged along the contour of the circular underground continuous wall and is located at the top of the circular underground continuous wall; the inner lining wall is close to the inner side wall of the circular underground continuous wall; the bottom plate is a flat plate structure and is laid flat in the circular underground continuous wall; the arch seat is arranged on the upper end surface of the bottom plate; the top of the cover plate is flush with the top surface of the cap beam; the pile foundation is located in the circular underground continuous wall. The present invention has strong anti-overturning performance and excellent horizontal and vertical bearing performance, which can greatly reduce the construction difficulty and cost of the arch seat foundation of a traditional large-span arch bridge in a deep overburden area.

Description

Technical Field

[0001] The invention relates to the field of geotechnical engineering, and in particular to an annular underground continuous wall foundation of a large-span arch bridge in a deep overburden area. Background Art

[0002] In order to withstand the huge horizontal thrust and vertical load from the superstructure of the long-span arch bridge, and to meet the stringent requirements of the superstructure of the long-span arch bridge for horizontal and vertical displacement, the traditional long-span arch bridge foundation mostly chooses bedrock with good bearing capacity and integrity as the bearing layer, and the foundation form mostly adopts open excavation foundation. However, for areas with deep overburden, the deep burial of the bedrock layer makes the construction difficulty and cost of the long-span arch bridge foundation greatly increased. As a foundation form with three functions of retaining, anti-seepage and bearing, the underground continuous wall has the characteristics of high degree of mechanization, low noise, low cost, wide adaptability to soil types, and high hoop stiffness and excellent adhesion to the foundation soil. It is currently being promoted and applied to various large-span bridge foundations at home and abroad. For example, the shaft-type underground continuous wall foundation and the multi-wall underground continuous wall foundation have been widely used in the foundation engineering of many large-span bridge projects in Japan.

[0003] When building a long-span arch bridge in a deep overburden area, the selection of the arch seat foundation will play a vital role in the normal service of the arch bridge after its completion. The selected foundation form should not only have a huge horizontal bearing capacity, but also have excellent vertical load bearing capacity. If the traditional open excavation and gravity foundation with rock as the bearing layer is still used, the construction difficulty and cost of the foundation will increase significantly, and it will be difficult to meet the design requirements. In addition, because the underlying soil in the arch seat foundation area in the deep overburden area is mostly hydraulically connected with the river system, it brings many uncertainties to the subsequent construction of the arch bridge superstructure and the safety of later operation. The annular underground continuous wall foundation of the arch bridge has strong overall stiffness, excellent anti-seepage and huge anti-overturning performance, and the pile foundation is a deep foundation form with excellent vertical load bearing performance. The combination of the two will make it an important alternative foundation form for the arch seat foundation of a long-span arch bridge in a deep overburden area. Summary of the invention

[0004] The technical problem to be solved by the present invention is to solve the problems of great construction difficulty and high cost caused by using bedrock as the bearing layer of the arch seat foundation when building a long-span arch bridge in an area with a thick overburden layer. A combined foundation for a long-span arch bridge in an area with a thick overburden layer is proposed.

[0005] To achieve the above-mentioned purpose, the technical scheme adopted by the present invention is: a circular underground continuous wall foundation of a large-span arch bridge in a deep overburden area, comprising a circular underground continuous wall, a cap beam, a lining wall, a bottom plate, an arch seat, a cover plate and a pile foundation; the circular underground continuous wall comprises a phase I trough section and a phase II trough section, both of which are arc-shaped, the length of the phase I trough section is greater than the length of the phase II trough section, a number of the phase I trough sections and a number of the phase II trough sections are spaced to form a ring, and the bottom of the phase I trough section and the bottom of the phase II trough section are both embedded in the bedrock layer; the cap beam is annular in structure, and the cap beam is arranged along the circular underground continuous wall. The outline of the wall is set and is located at the top of the annular underground continuous wall; the lining wall is close to the inner wall of the annular underground continuous wall; the bottom plate is a flat structure and is laid flat in the annular underground continuous wall and is located in the middle of the annular underground continuous wall, and the side of the bottom plate is connected to the inner wall of the annular underground continuous wall; the arch seat is set on the upper end surface of the bottom plate; the cover plate covers the upper opening of the annular underground continuous wall, and the top of the cover plate is flush with the top surface of the cap beam; the pile foundation is located in the annular underground continuous wall, the upper end of the pile foundation is embedded in the bottom plate, and the lower end of the pile foundation is embedded in the bedrock layer.

[0006] Furthermore, a plurality of the pile foundations are distributed in a hexagonal area, and the pile foundations are constructed using a non-squeezing pile construction process, which includes a punched cast-in-place pile and a bored cast-in-place pile.

[0007] Furthermore, the annular underground continuous wall, cap beam, lining wall, base plate, arch seat, cover plate and pile foundation are all cast-in-place reinforced concrete structures.

[0008] Furthermore, the embedding depths of the phase I trough section and the phase II trough section are both greater than 4.0 m, and the thicknesses of the phase I trough section and the phase II trough section are both 0.8 m-1.6 m.

[0009] Furthermore, the outer edge thickness of the cap beam is 1.5-2.5m, the inner edge thickness of the cap beam is 2.0-3.5m, and the inner edge thickness of the cap beam is less than the outer edge thickness of the cap beam; the top width of the cap beam is greater than the thickness of the annular underground continuous wall, the horizontal distance from the outer edge wall of the cap beam to the outer wall of the annular underground continuous wall is 1.0-1.5m, and the inner edge wall of the cap beam is flush with the outer wall of the lining wall; the cap beam is cast in sections, and the construction joints of the cap beam are staggered with the joints of each groove section of the annular underground continuous wall.

[0010] Furthermore, the lining walls are cast in layers vertically, and each layer of the lining walls is cast in sections, and the construction joints of the lining walls are staggered with the construction joints of the cap beams and the joints of each groove section of the annular underground continuous wall; the outer wall surface of the top layer of the lining walls is flush with the side surface of the cap beam, and the thickness of the remaining layers of the lining walls should be 0.5-0.75m larger than that of the top layer of the lining walls; the sum of the heights of each layer of the lining walls is equal to the excavation depth of the foundation pit.

[0011] Furthermore, the thickness of the bottom plate is 5-8m.

[0012] Furthermore, the height of the arch seat is 18-25m, and the width of the arch seat is 8-13m; the arch seat is a separate and layered casting structure, and the number of layered casting times is 5-7 times.

[0013] Furthermore, it also includes a post-cast strip, which is located between the arch seat and the lining wall; the post-cast strip is cast in one time, and the top surface of the post-cast strip is flush with the bottom of the cover plate; after the construction of the post-cast strip is completed, sand is backfilled between the arch seat and the lining wall, and the top surface of the sand is flush with the bottom surface of the cover plate.

[0014] Furthermore, the cover plate has a thickness of 0.5-0.8 m and is a reinforced concrete structure cast in one step.

[0015] Due to the adoption of the above technical solution, the present invention has the following beneficial effects:

[0016] (1) The annular underground continuous wall of the present invention includes the first phase trough section 10 and the second phase trough section and forms an annular structure, with large annular stiffness, and through the hexagonal pile foundation and the lower end embedded in the bedrock layer, it has strong anti-overturning and anti-slip performance, wherein the underground continuous wall foundation is mainly used to bear the horizontal bearing capacity transmitted by the upper structure, and the pile foundation is mainly used to bear the vertical bearing capacity transmitted by the upper structure, and can meet the stringent requirements of the upper structure of the long-span arch bridge for horizontal and vertical displacement. The present invention has the three functions of retaining soil, anti-seepage, and bearing at the same time, and can meet the requirements of the foundation structure performance of the long-span arch bridge construction and operation stage under the working conditions of the deep overburden area and the lower overburden layer being hydraulically connected with the riverside water system.

[0017] (2) The present invention adopts a cast-in-place reinforced concrete structure. By casting the annular underground continuous wall, cap beam, lining wall and arch seat in sections, and staggering the joints during casting, the structural strength can be ensured while greatly reducing the construction difficulty and cost of the arch seat foundation of a large-span arch bridge in areas with thick covering layers.

[0018] (3) The present invention also includes a post-cast strip. By providing the post-cast strip, harmful cracks that may be generated in the cast-in-place reinforced concrete structure due to uneven temperature and shrinkage can be prevented, and the composite foundation can be further reinforced. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 is a plan layout diagram of the present invention;

[0020] Figure 2 It is a front view of the present invention;

[0021] Figure 3 It is a left side view of the present invention;

[0022] Figure 4 The construction trench section distribution diagram of the annular underground continuous wall of the present invention;

[0023] Figure 5 is a cross-sectional view of the present invention;

[0024] Figure 6 It is the distribution diagram of the pile foundation of the present invention.

[0025] In the attached figure, 1-annular underground continuous wall, 2-cap beam, 3-lining wall, 4-bottom plate, 5-arch seat, 6-cover plate, 7-pile foundation, 8-backfill sand, 9-post-cast strip, 10-phase I trench section, 11-phase II trench section. DETAILED DESCRIPTION

[0026] In order to make the technical features and advantages of the present invention clearer and to facilitate the application in practical engineering, the technical solutions and specific implementation methods involved in the present invention are described in detail and completely below. Obviously, the described embodiments are only part of the embodiments of the present invention, not all. Based on this embodiment, all other embodiments obtained by ordinary technicians in this field without creative work are within the protection scope of the present invention.

[0027] like Figures 1 to 6 As shown, a circular underground continuous wall foundation of a large-span arch bridge in a thick overburden area comprises a circular underground continuous wall 1, a cap beam 2, an inner lining wall 3, a bottom plate 4, an arch seat 5, a cover plate 6, a pile foundation 7 and a post-cast strip 9; wherein:

[0028] The annular underground continuous wall 1 includes a phase I trench section 10 and a phase II trench section 11, and the phase I trench section 10 and the phase II trench section 11 are connected alternately to form a ring, and the bottom of the phase I trench section 10 and the bottom of the phase II trench section 11 are both embedded in the bedrock layer; the embedding depth of the phase I trench section 10 and the phase II trench section 11 are both greater than 4.0m, and the thickness of the phase I trench section 10 and the phase II trench section 11 are both 0.8m-1.6m. The cap beam 2 is arranged along the contour of the annular underground continuous wall 1 and is located at the top of the annular underground continuous wall 1; the outer edge thickness of the cap beam 2 is 1.5-2.5m, the inner edge thickness of the cap beam 2 is 2.0-3.5m, and the inner edge thickness of the cap beam 2 is less than the outer edge thickness of the cap beam 2; the top width of the cap beam 2 is greater than the thickness of the annular underground continuous wall 1, the horizontal distance from the outer edge wall surface of the cap beam 2 to the outer side wall surface of the annular underground continuous wall 1 is 1.0-1.5m, and the inner edge wall surface of the cap beam 2 is flush with the outer side wall surface of the lining wall 3; the cap beam 2 is cast in sections, and the construction joints of the cap beam 2 are staggered with the joints of each groove section of the annular underground continuous wall 1.

[0029] The lining wall 3 is close to the inner wall of the annular underground continuous wall 1; the lining wall 3 is cast in layers vertically, and each layer of the lining wall 3 is cast in sections, and the construction joints of the lining wall 3 are staggered with the construction joints of the cap beam 2 and the joints of each slot section of the annular underground continuous wall 1; the outer wall surface of the top layer of the lining wall 3 is flush with the side of the cap beam 2, and the thickness of the remaining layers of the lining wall 3 should be 0.5-0.75m greater than the top layer of the lining wall 3; the sum of the heights of each layer of the lining wall 3 is equal to the excavation depth of the foundation pit. The bottom plate 4 is a flat plate structure and is laid flat in the annular underground continuous wall 1. The side of the bottom plate 4 is connected to the inner wall of the annular underground continuous wall 1, and the thickness of the bottom plate 4 is 5-8m. The arch seat 5 is arranged on the upper end surface of the bottom plate 4; the top of the cover plate 6 is flush with the top surface of the cap beam 2, and the cover plate 6 covers the upper opening of the annular underground continuous wall 1; the thickness of the cover plate 6 is 0.5-0.8m, and it is a reinforced concrete structure that is cast in one time. The height of the arch seat 5 is 18-25m, and the width of the arch seat 5 is 8-13m; the arch seat 5 is a separate and layered casting structure, and the number of layered castings is 5-7 times.

[0030] The pile foundation 7 is located in the annular underground continuous wall 1, and several of the pile foundations 7 are distributed in a hexagonal area; the upper end of the pile foundation 7 is embedded in the bottom plate 4, and the lower end of the pile foundation 7 is embedded in the bedrock layer; the pile foundation 7 is constructed using a non-squeezing pile construction process, and the non-squeezing pile construction process includes punching cast-in-place piles and bored cast-in-place piles. The post-cast strip 9 is located between the arch seat 5 and the lining wall 3; the post-cast strip 9 is cast in one time, and the top surface of the post-cast strip 9 is flush with the bottom of the cover plate 6; after the construction of the post-cast strip 9 is completed, backfill sand 8 between the arch seat 5 and the lining wall 3, and the top surface of the sand is flush with the bottom surface of the cover plate 6. In this embodiment, the annular underground continuous wall 1, cap beam 2, lining wall 3, bottom plate 4, arch seat 5, cover plate 6 and pile foundation 7 are all cast-in-place reinforced concrete structures.

[0031] Based on the above structure, the construction steps of this embodiment specifically include the following:

[0032] (1) Construction of pile foundation 7: According to the designed soil and the on-site measurement points, the specific position of each pile foundation 7 is determined. The pile foundation construction adopts the non-squeezing pile construction technology, such as impact cast-in-place piles and bored cast-in-place piles. The construction sequence of the pile foundation is first the middle and then the two sides. After the hole is excavated and the mud wall is protected, the underwater concrete is poured in time. During the pouring process, when the pile top elevation reaches the designed elevation, the concrete pouring is stopped, and then the drilled hole from the pile top to the surface depth is filled and compacted by backfilling sand 8.

[0033] (2) Construction of guide wall of annular underground continuous wall 1: The guide wall is set on both sides of the annular underground continuous wall 1 to bear the load of construction equipment, guide the slot milling machine, and prevent the collapse of the upper part of the slot section. The guide wall can be composed of "L" or "[" shaped reinforced concrete walls. Generally, the "L" shape is arranged on the outside and the "[" shape is arranged on the inside.

[0034] (3) Preparation of mud circulation system: In order to prevent the occurrence of hole collapse and instability during the excavation of each slot section of the annular underground continuous wall 1, mud wall protection measures are adopted to ensure the stability of the slot wall, and the mud also plays the role of lubrication, suspension of drilling cuttings, and cooling of drilling tools. If the construction site is limited by the site area, the mud circulation system can be set up on the inner side of the annular underground continuous wall 1, and a slurry storage tank, mixing tank, and circulation tank can be excavated on site. The expanded mud is pumped into the slot hole by a mud pump to play the role of wall protection. The mud liquid level is not lower than the top surface of the guide wall. For mud that does not meet the later indicators, such as mud recovered from pouring concrete, the hydraulic milling can be used to reversely extract the mud and send it to the mud purifier, and then pumped to the slurry storage tank.

[0035] (4) Preparation of mud: The wall protection mud can be prepared by mixing medium-viscosity sodium-based bentonite and clean water in a certain ratio, generally 100:1000. After being stirred by a cyclone-type high-speed mud mixer, it is placed in a new slurry pool and allowed to swell for 24 hours. After swelling, no segregation or precipitation occurs in the slurry. The slurry can be used when the slurry index meets the requirements. If the slurry index after recycling does not meet the requirements, sodium carboxymethyl cellulose (CMC) or sodium 2 CO 3 To increase the viscosity of the slurry, add barite powder to increase the weight of the slurry so that it can be used again after reaching the usage index.

[0036] (5) Construction of the annular underground continuous wall 1: The annular underground continuous wall 1 is constructed by skipping holes. First, the overlying soil layer is excavated with a grab bucket. For the harder bedrock layer, a slot milling machine is used to break and excavate it. The first phase slot section 10 is slotted by three millings, and the second phase slot section 11 is slotted by one milling. The width of the first phase slot section 10 is about three times that of the second phase slot section 11. During construction, the soil on both sides of the slot section is removed, and then the soil in the middle slot section is removed. Mud wall protection is used throughout the slot milling process. During the slot forming process, the verticality of the hydraulic guide plate is tracked and corrected to ensure that its verticality is controlled below 1 / 300. After the slot section is excavated, the silt at the bottom of the hole is removed by a slotting machine, and the slot wall is brushed with a wire brush until there is no silt attached to the wire brush, so as to ensure the connection quality between the slot sections.

[0037] (6) Processing of steel cages: The semi-finished steel cages are processed in the steel processing plant (cutting, bending, cutting, etc.), and transported to the site for assembly in batches according to the progress. The steel cages are assembled according to the principle of first bottom and then top, first truss and then single bar, and the steel cages are assembled in one go. PVC segment locators are set at both ends of the steel cages, and steel plate locators are set in the length direction. The main bars at the upper end of the steel cages are covered with PVC pipes to facilitate the removal of the pile heads in the later stage.

[0038] (7) Lifting of the steel cage: The steel cage of the ground-anchored wall is hoisted by two cranes. The maximum weight of the steel cage is 35t. A 180t crawler crane is used as the main hoist; an 80t crane is used as the auxiliary crane to assist in turning it over in the air. A "steel shoulder pole" double hook is used for lifting. The main hook has 8-10 lifting points and is arranged at the upper part; the auxiliary hook has 6-8 lifting points and is arranged in the middle and lower part.

[0039] (8) Concrete pouring: Two Φ280mm conduits are arranged in the phase I trough section 10, and one in the phase II trough section 11. Before installing the conduits, compression and air tightness tests are carried out. The first batch of concrete is poured using the isolation ball method. First, a small amount of mortar is injected for lubrication, and then concrete is poured in. The extrusion ball plug buries the bottom of the conduit. Each conduit is fed evenly, and the height difference of the concrete surface is not greater than 0.5m. The buried depth of the conduit shall not be less than 2m. The height of the concrete surface is measured every 30 minutes. The phase II trough section 11 in the middle can only be constructed 7 days after the construction of the phase I trough sections 10 on both sides is completed.

[0040] (9) Construction of cap beam 2: After the construction of the annular underground continuous wall 1 is completed, the construction of the upper cap beam 2 can be carried out. First, the foundation pit of the cap beam 2 section is excavated. After the excavation reaches the designed elevation, the concrete pouring of the cap beam 2 can be carried out after the bottom is cleaned and the trench is inspected. The cap beam 2 is poured in sections, and its construction joints are staggered with the joints of each annular underground continuous trench section.

[0041] (10) Excavation of foundation pit and construction of inner lining wall 3: After the construction of cap beam 2 is completed, the excavation of foundation pit can be carried out. When the foundation pit is excavated to the bottom elevation of each section of inner lining wall 3, the inner lining wall 3 of that section is cast in time. The inner lining wall 3 is cast in sections, and its construction joints are staggered with the joints of the cap beam 2 and each groove section of the annular underground continuous wall 1.

[0042] (11) Construction of base plate 4: After the foundation pit is excavated to the designed elevation and the bottom is cleaned and inspected, the construction of base plate 4 can be carried out. When cleaning the bottom, the top of the pile foundation 7 constructed previously is cut and cleaned according to the design requirements. The base plate 4 is poured at one time. Since the volume of concrete poured at one time for the base plate 4 is large, refer to the large-volume concrete construction process for guidance of the specific construction work.

[0043] (12) Construction of arch seat 5: The construction of arch seat 5 is carried out in layers. After the construction of base plate 4 is completed and the strength of the upper concrete meets the construction strength requirements, the construction of the first layer of concrete for arch seat 5 shall be carried out immediately. The interval time shall not exceed 10 days.

[0044] (13) Construction of post-cast strip 9: After the construction of the arch seat 5 is completed, the construction of the post-cast strip 9 between the arch seat 5 and the lining wall 3 can be carried out. The post-cast strip 9 is constructed in layers, and the construction joints between each layer are staggered with the construction joints of the arch seat 5.

[0045] (14) Backfilling with sand and soil: After the construction of the arch seat 5 and the post-casting strip 9 is completed, the backfilling work of sand and soil can be carried out. The space between the arch seat 5 and the lining wall 3 is backfilled with sand and soil of the designed grade and compaction degree. The backfilling height of sand and soil should be flush with the bottom surface of the cover plate 6.

[0046] (15) Construction of cover plate 6: After the sand backfill is completed, the construction of cover plate 6 can be carried out. The cover plate 6 is poured in one go. After the pouring is completed, attention should be paid to the maintenance of the cover plate 6.

[0047] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit the same. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or make equivalent replacements for some of the technical features therein, and these modifications or replacements do not deviate the essence of the corresponding technical solutions from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A circular underground continuous wall foundation for a long-span arch bridge in a thick overburden area, characterized by: It comprises an annular underground continuous wall, a cap beam, an inner lining wall, a bottom plate, an arch seat, a cover plate and a pile foundation; the annular underground continuous wall comprises a phase I trough section and a phase II trough section, both of which are arc-shaped, the length of the phase I trough section is greater than that of the phase II trough section, a number of the phase I trough sections and a number of the phase II trough sections are spaced to form a ring, and the bottom of the phase I trough section and the bottom of the phase II trough section are both embedded in the bedrock layer; the cap beam is annular in structure, the cap beam is arranged along the contour of the annular underground continuous wall and is located at the top of the annular underground continuous wall; the inner lining wall is close to the inner side wall of the annular underground continuous wall; the bottom plate is a flat plate structure and is laid flat in the annular underground continuous wall and is located in the middle of the annular underground continuous wall, and the side of the bottom plate is connected to the inner side wall of the annular underground continuous wall; the arch seat is arranged on the upper end surface of the bottom plate; The cover plate covers the upper opening of the annular underground continuous wall, and the top of the cover plate is flush with the top surface of the cap beam; the pile foundation is located in the annular underground continuous wall, the upper end of the pile foundation is embedded in the bottom plate, and the lower end of the pile foundation is embedded in the bedrock layer; The plurality of pile foundations are distributed in a hexagonal area, and the pile foundations are constructed using a non-squeezing pile construction process, which includes a punching cast-in-place pile and a bored cast-in-place pile; The outer edge thickness of the cap beam is 1.5-2.5m, the inner edge thickness of the cap beam is 2.0-3.5m, and the inner edge thickness of the cap beam is less than the outer edge thickness of the cap beam; the top width of the cap beam is greater than the thickness of the annular underground continuous wall, the horizontal distance from the outer edge wall surface of the cap beam to the outer wall surface of the annular underground continuous wall is 1.0-1.5m, and the inner edge wall surface of the cap beam is flush with the outer wall surface of the lining wall; the cap beam is cast in sections, and the construction joints of the cap beam and the joints of each groove section of the annular underground continuous wall are staggered; The lining wall is cast in layers vertically, and each layer of the lining wall is cast in sections, and the construction joints of the lining wall are staggered with the construction joints of the cap beam and the joints of each groove section of the annular underground continuous wall; the outer wall surface of the uppermost layer of the lining wall is flush with the side surface of the cap beam, and the thickness of the remaining layers of the lining wall should be 0.5-0.75m greater than that of the uppermost layer of the lining wall; the sum of the heights of each layer of the lining wall is equal to the excavation depth of the foundation pit; It also includes a post-cast strip, which is located between the arch seat and the lining wall; the post-cast strip is cast in one time, and the top surface of the post-cast strip is flush with the bottom of the cover plate; after the construction of the post-cast strip is completed, sand is backfilled between the arch seat and the lining wall, and the top surface of the sand is flush with the bottom surface of the cover plate.

2. The annular underground continuous wall foundation of a large-span arch bridge in a thick overburden area according to claim 1, characterized in that: The annular underground continuous wall, cap beam, lining wall, bottom plate, arch seat, cover plate and pile foundation are all cast-in-place reinforced concrete structures.

3. The annular underground continuous wall foundation of a large-span arch bridge in a thick overburden area according to claim 1, characterized in that: The embedding depths of the phase I trough section and the phase II trough section are both greater than 4.0 m, and the thicknesses of the phase I trough section and the phase II trough section are both 0.8 m to 1.6 m.

4. The annular underground continuous wall foundation of a large-span arch bridge in a thick overburden area according to claim 1, characterized in that: The thickness of the bottom plate is 5-8m.

5. The annular underground continuous wall foundation of a large-span arch bridge in a thick overburden area according to claim 1, characterized in that: The height of the arch seat is 18-25m, and the width of the arch seat is 8-13m; the arch seat is a separate and layered casting structure, and the number of layered casting times is 5-7 times.

6. The annular underground continuous wall foundation of a large-span arch bridge in a thick overburden area according to claim 1, characterized in that: The cover plate has a thickness of 0.5-0.8 m and is a reinforced concrete structure cast in one step.

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