Anchor structure and construction method suitable for excavation-free foundation pit in medium-weathered rock strata

Abstract

The present invention discloses an anchoring structure and construction method suitable for excavation-free foundation pits in medium-weathered rock formations. A circular interlocking pile is provided as a pile foundation, and a shaft-type ground-connected wall is formed by overlapping a rectangular interlocking pile and a circular interlocking pile. The ground-connected wall is embedded in the medium-weathered rock. A plurality of longitudinal moment interlocking piles and circular interlocking piles are overlapped to form a longitudinal ground-connected wall. A plurality of transverse moment interlocking piles are rigidly connected to form a transverse ground-connected wall. A cell is formed by interlacing the longitudinal ground-connected wall and the transverse ground-connected wall. The cell and the front end area of ​​the cell front wall are reinforced by grouting. A cap and an anchor body are sequentially provided on the top of the ground-connected wall. The structure of the present invention has good control over the settlement and deformation of the soil in the construction area, and can provide a large vertical and horizontal bearing capacity. By performing grouting construction in the cell, there is no need to construct and cast the bottom plate and lining like the traditional ground-connected wall structure, and there is no need to excavate the soil in the cell of the shaft-type ground-connected wall. The construction workload is reduced, the construction period is short, and the scheme has good economic efficiency.

Description

Technical Field

[0001] The present invention belongs to the technical field of bridge construction, and more specifically, relates to an anchoring structure and a construction method suitable for a medium-weathered rock stratum without excavation of a foundation pit. Background Art

[0002] The anchor foundation is the main load-bearing component of the suspension bridge. The load-bearing performance of the anchor foundation is directly related to the overall stability and bearing performance of the suspension bridge. It is mainly assumed that the anchor foundation is a rigid structure, and the design of the anchor foundation is carried out by verifying the base bearing capacity, anti-sliding stability and anti-overturning stability of the anchor foundation.

[0003] At present, the anchor foundation generally adopts gravity anchor, and the anchor foundation bottom plate is set on the lower bearing layer, which is the key part to support the main cable and ensure the stability of the main structure of the whole bridge. Gravity anchor includes caisson foundation, ground-connected wall foundation, composite anchor foundation, etc. The anchor foundation of domestic large-span bridges generally adopts caisson foundation or underground continuous wall foundation. The anchor foundation buried underground is supported and laterally constrained by the rock and soil body, and the constraint load provided by the soil around the anchor is not considered. However, the construction scale of these two foundations is generally large, and the main construction process is more. The excavation of the anchor foundation pit and the pouring of the anchor body are long. During construction, the excavation of the anchor foundation pit needs to be carried out in layers, and the anti-overturning stability of the foundation pit needs to be considered. It is necessary to set up an inner lining or inner support for the foundation pit support. Its enclosure structure only plays a role as a supporting structure and does not participate in the overall force of the anchor foundation, which increases the construction difficulty and construction process, and greatly prolongs the construction period.

[0004] Therefore, at this stage, there is a need for an anchor foundation that can meet the requirements of bearing capacity and settlement, which can provide good work efficiency while ensuring the stability of the foundation structure, making the construction simpler and shortening the construction period. Summary of the invention

[0005] In view of the defects that the anchor foundation of the prior art needs to be provided with an inner lining or an inner support for foundation pit support, and has the advantages of great construction difficulty, many construction processes, and a long construction period, the present invention provides a technical solution, by providing circular interlocking piles as pile foundations, and adopting rectangular interlocking piles and circular interlocking overlaps to form a shaft-type ground-connected wall, the shaft-type ground-connected wall is embedded in the medium-weathered rock strata, and adopts an excavation-free method, which has better control over the settlement and deformation of the soil in the construction area, can provide better vertical and horizontal bearing capacity, and has a short construction period.

[0006] In order to achieve the above-mentioned purpose, the present invention provides an anchoring structure suitable for excavation-free foundation pits in medium-weathered rock strata, comprising a plurality of circular interlocking piles arranged in an array in a soil layer; rectangular interlocking piles connected to the circular interlocking piles, comprising longitudinal moment interlocking piles and transverse moment interlocking piles, the longitudinal moment interlocking piles are overlapped with adjacent circular interlocking piles on both sides to form longitudinal ground connecting walls, and the transverse moment interlocking piles are overlapped with the longitudinal moment interlocking piles on both sides to form transverse ground connecting walls; the plurality of longitudinal ground connecting walls and transverse ground connecting walls constitute a shaft-type ground connecting wall, the bottom of which is embedded in the medium-weathered rock strata; a cell formed by the interlacing of the longitudinal ground connecting walls and the transverse ground connecting walls; a grouting reinforcement area arranged in the cell and in the front end of the cell front wall and in the front end area of ​​the cell front wall; and a cap and an anchor body arranged in sequence on the top of the cell.

[0007] Furthermore, the shaft-type ground-connected wall comprises 5 groups of longitudinal ground-connected walls and 4 groups of transverse ground-connected walls, which are overlapped and have 12 cells therein.

[0008] Furthermore, the circular interlocking pile foundation has a diameter of 3m, a length of 30m, and a rock-embedded depth of 5m.

[0009] Furthermore, the grouting reinforcement area includes a semicircular area located at the front end of the cell front wall with the cell front wall (9) as the diameter, and the cell front wall is 30m long.

[0010] Furthermore, the thickness of the foundation is 7m, and its size range is 42m in the longitudinal direction of the bridge and 30m in the transverse direction of the bridge.

[0011] According to another aspect of the present invention, there is also provided an anchor construction method applicable to a medium-weathered rock stratum without excavation of a foundation pit, comprising the following steps:

[0012] S100: Level the site and make guide walls for the circular bite piles and the rectangular bite piles. The diameter of the positioning holes of the guide walls should be 20 mm larger than the pile diameters of the circular bite piles and the rectangular bite piles.

[0013] S200: Carry out the pile foundation construction of the circular interlocking pile. After completion, lower the steel cage and the acoustic detection pipe and pour concrete;

[0014] S300: Carry out the trench section construction of the moment bite piles. After completion, lower the steel cage and pour concrete. The moment bite piles along the bridge are overlapped by bite, and the moment bite piles across the bridge are connected by rigid joints.

[0015] S400: Under the lattice frame structure composed of circular interlocking piles and rectangular interlocking piles, the soil in the cell and the front area of ​​the cell front wall is reinforced by foundation grouting;

[0016] S500: Roughen the top of the cell, erect the formwork and tie the steel bars, and after completion, cast the cap by pouring concrete in layers;

[0017] S600: The anchor body is cast in layers and blocks on the formed foundation.

[0018] Furthermore, the circular interlocking pile construction method comprises the following steps:

[0019] S201: Use total station to accurately locate the center of the pile;

[0020] S202: According to the water quality and soil quality of the construction area, the mud ratio is carried out, and bentonite and other admixtures are selected and mixed in proportion to obtain high-quality mud with stable performance, less precipitation, good wall protection effect and high hole-forming quality;

[0021] S203: Put the drilling rig into position by using the rotary drilling rig, and straighten the mast to perform straight hole operation;

[0022] S204: The removed drilling slag is uniformly placed in a drilling slag box and transported to the off-site by vehicle in a timely manner;

[0023] S205: After the borehole reaches the designed elevation, the hole is cleaned and the pile bottom sediment thickness shall not exceed 10cm;

[0024] S206: Lower the steel cage and the acoustic detection pipe and pour concrete. The concrete grade is C30. The buried depth of the concrete pump pipe is between 2m and 6m. After the circular interlocking pile (1) is poured, the verticality deviation of the pile body is <1%.

[0025] Furthermore, the construction method of the moment bite pile comprises the following steps:

[0026] S301: Use total station to accurately locate the pile slot width;

[0027] S302: Mix the mud according to the water quality and soil quality of the construction area. The relative density of the fresh mud is between 1.05 and 1.1.

[0028] S303: The groove is formed by a slot milling machine. The vertical deviation of the groove shall not be greater than 1 / 400 of the wall height. The mud level in the groove shall be kept above the groundwater level by more than 1m. The load concentration near the groove wall shall be less than 20kN / ㎡.

[0029] S304: Lower the steel cage and pour concrete. The moment bite piles along the bridge are overlapped by bite, and the moment bite piles across the bridge are connected by rigid joints.

[0030] Furthermore, the grouting reinforcement area is a semicircular area inside the cell and in front of the cell front wall with the cell front wall as the diameter. The grouting depth of the grouting reinforcement area 6 is 10m. The strength of the grouting cement slurry should not be less than 10MPa within 7 days. After the grouting volume reaches the design requirements, the grouting pressure reaches the control pressure and maintains the load for 5 minutes.

[0031] Furthermore, the anchor body is divided into a left anchor block and a right anchor block and cast separately, each block is cast in layers, and the thickness of most layers is about 2m; two layers of cooling pipes are arranged in each layer, and the cooling pipes are water-transmitting black iron pipes with a diameter of φ42.3mm and a wall thickness of 3.25mm, and the horizontal and vertical spacings of the cooling pipes are both about 1m; the time interval between the pouring of each adjacent layer of concrete of the anchor body (8) is preferably 5 to 7 days; after the concrete is poured, a retarder is sprayed on the surface, and after reaching an appropriate strength, the surface slurry is removed with high-pressure water, and then clean water is stored for curing; before the next layer of concrete is poured, the poured concrete surface needs to be roughened and cleaned; after the two concrete layers of the anchor body are formed, the sections are poured to connect the blocks as a whole.

[0032] In general, the above technical solutions conceived by the present invention can achieve the following beneficial effects compared with the prior art:

[0033] 1. The present invention is an anchor structure and construction method suitable for excavation-free foundation pits in medium-weathered rock strata. Circular interlocking piles and rectangular interlocking piles are used to form a shaft-type ground-connected wall, which is embedded in the medium-weathered rock strata to ensure the coordinated force and deformation stability of the entire foundation. It can provide a larger vertical and horizontal bearing capacity, and does not require the casting of a base plate and an inner lining, so the construction workload is reduced and the bearing capacity of the anchor foundation is guaranteed.

[0034] 2. The present invention is an anchoring structure and construction method suitable for excavation-free foundation pits in medium-weathered rock strata. By providing a grouting reinforcement area, grouting is directly performed on the soil in the cell without excavating the soil in the shaft-type ground-connected wall cell. The scheme has good economy, little impact on the surrounding environment, and is relatively safe and quick to construct. Furthermore, grouting reinforcement is performed on the front end area of ​​the front wall of the cell, and the soil in the front end area is reinforced. When the anchor structure is subjected to horizontal tension, the horizontal displacement of the shaft-type ground-connected wall will be smaller, further ensuring the coordinated force and deformation stability of the entire foundation.

[0035] 3. The present invention is an anchor structure and construction method suitable for medium-weathered rock formations without excavation foundation pits, which can not only ensure the force requirements of the anchor foundation during the bridge cable hanging operation period, but also reduce the excavation of the anchor foundation soil, and has the characteristics of reducing construction difficulty, reducing project costs, and shortening construction period. BRIEF DESCRIPTION OF THE DRAWINGS

[0036] Figure 1 Schematic diagram of an anchor structure suitable for excavation-free foundation pit in medium-weathered rock strata according to an embodiment of the present invention;

[0037] Figure 2 A schematic diagram of a shaft-type ground-connected wall of an anchor structure suitable for excavation-free foundation pits in medium-weathered rock formations according to an embodiment of the present invention;

[0038] Figure 3 A top view of a shaft-type ground-connected wall structure in an embodiment of the present invention;

[0039] Figure 4 A side view of a shaft-type ground-connected wall in an embodiment of the present invention;

[0040] Figure 5 It is a schematic flow chart of an anchor construction method applicable to a medium-weathered rock layer without excavation foundation pit according to an embodiment of the present invention;

[0041] Figure 6 The present invention is a structural diagram of the steel bars of the cap in an anchorage structure suitable for excavation-free foundation pits in medium-weathered rock strata according to an embodiment of the present invention.

[0042] In all the drawings, the same figure numbers represent the same technical features, specifically: 1-circular interlocking piles, 2-moment interlocking piles, 201-moment interlocking piles in the longitudinal direction of the bridge, 202-moment interlocking piles in the transverse direction of the bridge, 3-cells, 4-ground-connected walls in the longitudinal direction of the bridge, 5-ground-connected walls in the transverse direction of the bridge, 6-grouting reinforcement area, 7-capping platform, 8-anchor body, 9-cell front wall. DETAILED DESCRIPTION

[0043] In order to make the purpose, technical solutions and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not intended to limit the present invention. In addition, the technical features involved in the various embodiments of the present invention described below can be combined with each other as long as they do not conflict with each other.

[0044] like Figure 1-6As shown, the present invention provides an anchoring structure and construction method suitable for excavation-free foundation pits in medium-weathered rock formations, wherein a pile foundation hole is dug out by a rotary drilling reverse circulation hole-making process, and a steel cage is placed in for grouting to form a circular interlocking pile 1; a slot is formed by a slot milling machine to form a second-phase slot section overlapping the circular interlocking pile 1, and a steel cage is placed in for grouting to form a moment interlocking pile 2, which includes a longitudinal moment interlocking pile 201 and a transverse moment interlocking pile 202; a plurality of longitudinal moment interlocking piles 201 are overlapped and combined with the circular interlocking pile 1 to form a longitudinal ground connection wall 4; a plurality of transverse moment interlocking piles 202 are rigidly connected to form a transverse ground connection wall 5; the longitudinal ground connection wall 4 and the transverse ground connection wall 5 are combined into a shaft-type ground connection wall to ensure The coordinated stress and deformation of the entire anchor foundation are stable; the lattice frame structure composed of circular interlocking piles 1 and rectangular interlocking piles 2 forms a cell 3, and multiple cells 3 are connected to each other to form a large-diameter pile foundation, which can provide good foundation bearing capacity. Further, the cell 3 is excavated without excavation, and the soil in the cell 3 and the front of the cell front wall 9 is reinforced by foundation grouting. By reinforcing the surface soil of the stratum, the deformation of the soil inside the shaft-type ground-connected wall is controlled to ensure the bearing performance of the ground-connected wall enclosure structure; by pouring the pedestal 7 and the anchor body 8 on the top of the cell 3 in sequence, the excavation of the anchor foundation soil is greatly reduced, and the complicated excavation and concrete backfilling construction procedures are reduced. While ensuring the stress requirements of the anchor foundation bridge during the cable hanging operation, the construction difficulty is reduced, and it has the characteristics of low project cost and short construction period.

[0045] like Figure 6 As shown, an embodiment of the present invention provides an anchor construction method applicable to a medium-weathered rock layer without excavation of a foundation pit, comprising the following steps:

[0046] S100: Leveling the site, making guide walls for the circular bite pile 1 and the rectangular bite pile 2, wherein the diameter of the positioning hole of the guide wall should be 20 mm larger than the pile diameter of the circular bite pile 1 and the rectangular bite pile 2;

[0047] S200: performing pile foundation construction of the circular interlocking pile 1, after which the steel cage and the acoustic detection pipe are lowered and concrete is poured;

[0048] S300: constructing the groove section of the moment bite pile 2, and after completion, lowering the steel cage and pouring concrete, wherein the moment bite pile 4 along the bridge is overlapped by a bite method, and the moment bite pile 5 in the transverse bridge is connected by a rigid joint;

[0049] S400: Under the lattice frame structure formed by the circular interlocking piles 1 and the rectangular interlocking piles 2, the lower part of the cell 3 and the front end area of ​​the cell front wall 9 are subjected to foundation grouting reinforcement treatment;

[0050] S500: roughening the top of the cell 3, erecting the formwork and tying the steel bars, and after completion, pouring the cap 3 by pouring concrete in layers;

[0051] S600: Casting the anchor body 8 in layers and blocks on the formed foundation 3.

[0052] In the production of the circular interlocking pile 1 in step S200, the specific construction steps are as follows:

[0053] S201: Use total station to accurately locate the center of the pile;

[0054] S202: According to the water quality and soil quality of the construction area, the mud ratio is carried out, and bentonite and other admixtures are selected and mixed in proportion to obtain high-quality mud with stable performance, less precipitation, good wall protection effect and high hole-forming quality;

[0055] S203: Put the drilling rig into position by using the rotary drilling rig, and straighten the mast to perform straight hole operation;

[0056] S204: The removed drilling slag is uniformly placed in a drilling slag box and transported to the off-site by vehicle in a timely manner;

[0057] S205: After the borehole reaches the designed elevation, the hole is cleaned and the pile bottom sediment thickness shall not exceed 10cm;

[0058] S206: Lower the steel cage and acoustic detection pipe and pour concrete.

[0059] In a preferred embodiment of the present invention, when performing step S200 to manufacture the circular interlocking pile 1, the circular interlocking pile 1 has a pile foundation diameter of 3m, a pile foundation length of 30m, and a rock embedding depth of 5m, and the drilling operation content of step S203 can be set according to the specifications of the circular interlocking pile 1; when performing step S206 to pour concrete, concrete with a grade of C30 can be used, and the rising height of the concrete surface can be accurately controlled during the pouring process, and the buried depth of the concrete pump pipe can be strictly controlled between 2m and 6m to ensure the quality of the bottom of the pile body, and the verticality deviation of the pile body can be strictly controlled to be <1%.

[0060] In a preferred embodiment of the present invention, when manufacturing the moment engagement pile 2 in step S300, the specific construction steps are as follows:

[0061] S301: Use total station to accurately locate the pile slot width;

[0062] S302: Mix the mud according to the water quality and soil quality of the construction area. The relative density of the fresh mud is between 1.05 and 1.1.

[0063] S303: Use a slot milling machine to form the slot. The verticality deviation of the slot shall not exceed 1 / 400 of the wall height. The mud level in the slot shall be kept at least 1m above the groundwater level.

[0064] S304: Lower the steel cage and pour concrete. The moment bite piles along the bridge are overlapped by bite, and the moment bite piles across the bridge are connected by rigid joints.

[0065] In a preferred embodiment of the present invention, during the trench section construction in step S303, in order to ensure the stability of the trench wall, the load near the trench wall must be strictly controlled, and the load concentration is required to be no more than 20 kN / ㎡.

[0066] When the grouting construction of the cell 3 in step S400 is performed, the grouting reinforcement area 6 is the semicircular area in the cell 3 and located at the front of the cell front wall 9 with the cell front wall 9 as the diameter, wherein the cell front wall 9 is 30m long and the grouting depth of the grouting reinforcement area 6 is 10m; during the grouting construction, the grouting pipe is ensured to be unobstructed, and the grouting volume and pressure are controlled. Ordinary silicate cement should be used for grouting, and the cement slurry strength should not be less than 10MPa within 7 days. After the grouting volume reaches the design requirements, the grouting pressure reaches the control pressure and is held for 5 minutes, the grouting can be terminated.

[0067] In a preferred embodiment of the present invention, when the cap 7 is made in step S500, the cap 7 is cast by pouring concrete in layers. In order to avoid temperature cracks in concrete construction, temperature control design is required before construction. After the concrete is poured, the thickness of the cap 7 is 7m, and the size range is 42m in the longitudinal direction of the bridge and 30m in the transverse direction of the bridge.

[0068] In the production of the anchor body 8 in step S600, the anchor body 8 is a large-volume concrete structure, which is cast in left and right anchor blocks, and a post-casting section is set between the blocks to connect the blocks as a whole. Each block is cast in layers, and the layer thickness is mostly about 2m. Two layers of cooling pipes are set in each layer. The cooling pipes are water-transmitting black iron pipes with a diameter of φ42.3mm and a wall thickness of 3.25mm. The horizontal and vertical spacing of the cooling pipes are both about 1m. The time interval between the pouring of concrete of each adjacent layer of the anchor body should be 5 to 7 days, and should not exceed 10 days. In order to ensure the bonding quality of the horizontal joints, after pouring the concrete, a retarder should be sprayed on the surface. After reaching the appropriate strength, the surface slurry should be removed with high-pressure water, and then cleaned with water for maintenance. When the temperature drops sharply, special attention should be paid to the surface insulation of the initial concrete to prevent the concrete from cracking. Before pouring the next layer of concrete, the poured concrete surface needs to be roughened and cleaned. During the entire process of anchor construction, the settlement of the anchor foundation should be observed regularly so that countermeasures can be taken.

[0069] like Figure 1-4As shown, in another embodiment of the present invention, there is also provided an anchoring structure suitable for excavation-free foundation of medium-weathered rock strata, including 5 groups of longitudinal ground diaphragm walls and 4 groups of bridge-direction ground diaphragm walls, a total of 40 circular interlocking piles 1, 35 longitudinal moment interlocking piles 201 and 16 transverse moment interlocking piles 202, the interior of the shaft-type ground diaphragm wall is divided into 12 cells, and the soil in the cells and the semicircular area with the front wall of the cells as the diameter is subjected to foundation grouting to form a grouting reinforcement area 6. The shaft-type ground diaphragm wall of the embodiment of the present invention has the characteristics of no excavation, high construction efficiency and stable force; a reinforced concrete pedestal 7 is arranged on the top of the shaft-type ground diaphragm wall foundation as the force transmission and stiffness requirement of the anchoring foundation, and further, an anchor body 8 is cast out of concrete on the pedestal 7, the anchor body 8 is a large-volume concrete structure, the anchor body 8 is cast in layers and blocks, a post-cast section is arranged between the anchor block and the loose cable saddle pier, and the post-cast section adopts micro-expansive concrete. Cooling water pipes are set in each layer of concrete for water cooling; multiple layers of pressure-bearing steel mesh are set under the rear anchor surface of the anchor block to bear and distribute the stress under the anchor; multiple layers of reinforcing steel mesh are set in the solid section at the top of the pier to resist the pressure transmitted by the loose cable saddle.

[0070] The present invention is an anchoring structure suitable for excavation-free foundation in medium-weathered rock strata. The circular interlocking piles 1 and the rectangular interlocking piles 2 form a shaft-type ground-connected wall, and the wall is embedded in the medium-weathered rock strata to ensure the coordinated force and deformation stability of the entire foundation. The structure can provide a large vertical and horizontal bearing capacity, and does not require the pouring of the bottom plate and the lining, which reduces the construction workload and ensures the bearing capacity of the anchoring foundation. The grouting reinforcement area 6 is provided to directly grout the soil in the cell 3 without digging the shaft-type ground-connected wall. The soil in the wall grid room has good economic efficiency, little impact on the surrounding environment, and is safe and quick to construct. Furthermore, the front end area of ​​the front wall 9 of the grid room is reinforced by grouting, and the soil in the front end area is reinforced. When the anchor structure is subjected to horizontal tension, the horizontal displacement of the shaft-type ground-connected wall will be smaller, further ensuring the coordinated force and deformation stability of the entire foundation; by successively pouring the pedestal 7 and the anchor body 8 on the shaft-type ground-connected wall, the force requirements of the anchor structure during the bridge cable hanging operation are guaranteed.

[0071] It will be easily understood by those skilled in the art that the above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the present invention should be included in the protection scope of the present invention.

Claims

1. An anchor construction method suitable for medium-weathered rock strata without excavation of foundation pits, characterized in that: The steps include: S100: Leveling the site, making guide walls for the circular interlocking piles (1) and the rectangular interlocking piles (2), wherein the diameter of the positioning holes of the guide walls should be 20 mm larger than the pile diameters of the circular interlocking piles (1) and the rectangular interlocking piles (2); S200: Carry out pile foundation construction of the circular interlocking pile (1), after which the steel cage and the acoustic detection pipe are lowered and concrete is poured; S300: constructing the groove section of the moment bite pile (2), after which the steel cage is lowered and concrete is poured, wherein the moment bite pile (201) along the bridge is overlapped by a bite method, and the moment bite pile (202) across the bridge is connected by a rigid joint; S400: Under the lattice frame structure formed by the circular interlocking piles (1) and the rectangular interlocking piles (2), a foundation grouting reinforcement treatment is performed on the soil inside the cell (3) and in the front end area of ​​the cell front wall (9); S500: roughening the top of the cell (3), erecting a formwork and tying steel bars, and after completion, pouring the cap (7) by pouring concrete in layers; S600: Casting the anchor body (8) in layers and blocks on the formed foundation (7); Among them, the anchor structure obtained by the anchor construction method suitable for medium-weathered rock strata without excavation of foundation pit includes: A plurality of circular interlocking piles (1) are arranged in an array in a soil layer, wherein the circular interlocking piles (1) are formed by digging a pile foundation hole using a rotary drilling reverse circulation hole-making process and placing a steel cage therein for grouting; A moment interlocking pile (2) connected to the circular interlocking pile (1), the moment interlocking pile (2) being formed by placing a steel cage in a second-stage slot section overlapped with the circular interlocking pile (1) for grouting, comprising a moment interlocking pile (201) in the longitudinal direction and a moment interlocking pile (202) in the transverse direction, the moment interlocking pile (201) in the longitudinal direction being overlapped with the adjacent circular interlocking pile (1) to form a longitudinal ground connection wall (4), and the moment interlocking pile (202) in the transverse direction being overlapped with the moment interlocking pile (201) in the longitudinal direction to form a transverse ground connection wall (5); the plurality of longitudinal ground connection walls (4) and the transverse ground connection walls (5) constitute a shaft-type ground connection wall, the bottom of which is embedded in a medium-weathered rock layer; A cell (3) is formed by interlacing the longitudinal ground connection wall (4) and the transverse ground connection wall (5); a plurality of cells (3) are interconnected to form a large-diameter pile foundation, providing a good foundation bearing capacity; A grouting reinforcement area (6) provided in the cell (3) and in the front end area of ​​the cell front wall (9); And a cap (7) and an anchor body (8) which are sequentially arranged on the top of the cell (3).

2. The anchoring construction method applicable to medium-weathered rock strata without excavation of foundation pit according to claim 1 is characterized in that: The shaft-type ground-connected wall comprises five groups of longitudinal ground-connected walls (4) and four groups of transverse ground-connected walls (5) which are overlapped and each other, and twelve cells (3) are arranged therein.

3. The anchoring construction method applicable to medium-weathered rock strata without excavation of foundation pit according to claim 1, characterized in that: The circular interlocking pile (1) has a pile foundation diameter of 3 m, a pile foundation length of 30 m, and a rock embedding depth of 5 m.

4. The anchoring construction method applicable to medium-weathered rock strata without excavation of foundation pit according to claim 1, characterized in that: The grouting reinforcement area (6) comprises a semicircular area located at the front end of the cell front wall (9) with the cell front wall (9) as the diameter, and the cell front wall (9) is 30 m long.

5. The anchoring construction method applicable to medium-weathered rock strata without excavation of foundation pit according to claim 1, characterized in that: The thickness of the cap (7) is 7 m, and its size range is 42 m in the longitudinal direction of the bridge and 30 m in the transverse direction of the bridge.

6. The anchoring construction method applicable to medium-weathered rock strata without excavation of foundation pit according to claim 1, characterized in that: The circular interlocking pile (1) construction method comprises the following steps: S201: Use total station to accurately locate the center of the pile; S202: According to the water quality and soil quality of the construction area, the mud ratio is carried out, and bentonite and other admixtures are selected and mixed in proportion to obtain high-quality mud with stable performance, less precipitation, good wall protection effect and high hole-forming quality; S203: Put the drilling rig into position by using the rotary drilling rig, and straighten the mast to perform straight hole operation; S204: The removed drilling slag is uniformly placed in a drilling slag box and transported to the off-site by vehicle in a timely manner; S205: After the borehole reaches the designed elevation, the hole is cleaned and the pile bottom sediment thickness shall not exceed 10cm; S206: Lower the steel cage and the acoustic detection pipe and pour concrete. The concrete grade is C30. The buried depth of the concrete pump pipe is between 2m and 6m. After the circular interlocking pile (1) is poured, the verticality deviation of the pile body is less than 1%.

7. The anchoring construction method applicable to medium-weathered rock strata without excavation of foundation pit according to claim 1, characterized in that: The construction method of the moment-interlocking pile (2) comprises the following steps: S301: Use total station to accurately locate the pile slot width; S302: Mix the mud according to the water quality and soil quality of the construction area. The relative density of the fresh mud is between 1.05 and 1.

1. S303: The groove is formed by a slot milling machine. The vertical deviation of the groove shall not be greater than 1 / 400 of the wall height. The mud level in the groove shall be kept above the groundwater level by more than 1m. The load concentration near the groove wall shall be less than 20kN / ㎡. S304: lower the steel cage and pour concrete, overlap the longitudinal moment bite piles (201) by bite, and connect the transverse moment bite piles (202) by rigid joints.

8. The anchoring construction method applicable to medium-weathered rock strata without excavation of foundation pit according to claim 1, characterized in that: The grouting reinforcement area (6) is the soil in the semicircular area at the front of the cell (3) and the cell front wall (9) with the cell front wall (9) as the diameter. The grouting depth of the grouting reinforcement area (6) is 10m. The strength of the grouting cement slurry should not be less than 10MPa within 7 days. After the grouting volume reaches the design requirement, the grouting pressure reaches the control pressure and is held for 5 minutes.

9. The anchoring construction method applicable to medium-weathered rock strata without excavation of foundation pit according to claim 1, characterized in that: The anchor body (8) is divided into a left anchor block and a right anchor block, which are cast separately. Each block is cast in layers with a layer thickness of 2m. Two layers of cooling pipes are arranged in each layer. The cooling pipes are water-transmitting black iron pipes with a diameter of φ42.3mm and a wall thickness of 3.25mm. The horizontal and vertical spacings of the cooling pipes are both 1m. The time interval between the pouring of each adjacent layer of concrete of the anchor body (8) is preferably 5 to 7 days. After the concrete is poured, a retarder is sprayed on the surface. After reaching an appropriate strength, the surface slurry is removed with high-pressure water, and then clean water is stored for curing. Before pouring the next layer of concrete, the poured concrete surface needs to be roughened and cleaned. After the two concrete layers of the anchor body (8) are formed, pouring is performed to connect the blocks as a whole.

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