Construction method and steel mould for half fender post of shallow foundation pit of underground structure

Abstract

The invention relates to the technical field of engineering construction, and discloses a construction method and a steel mould for a half fender post of an underground structure shallow foundation pit, the method comprises the following steps: S1, installing a reinforcement cage in a pore-forming area, hanging the reinforcement cage in place, and fixing the reinforcement cage after the reinforcement cage is detected to be qualified; s2, concrete is poured into the whole pile area through a guide pipe; s3, before initial setting of concrete in the whole pile area, the steel mold is hoisted and placed in the half-pile reinforcement cage area, and the steel mold is fixed when the lower end of the steel mold is located at the designed elevation position of the pile top of the whole pile; s4, concrete is poured into the half pile area; s5, after the concrete in the half pile area is initially set, the steel mold is hoisted out; and S6, after the half pile and the whole pile reach the design strength, the empty pile area is backfilled. The construction method has the beneficial effects that when the half pile is constructed, concrete is poured into the semicircular cylinder formed by the flat steel plate and the arc-shaped steel plate, so that the half pile is directly formed, the construction cost is reduced, the construction period is shortened, and the quality of the half pile is ensured.

Description

Technical Field

[0001] The present invention relates to the field of engineering construction technology, and specifically relates to a construction method and steel formwork for a semi-pile of a retaining pile for a shallow foundation pit of an underground structure. Background Art

[0002] With the acceleration of China's urbanization process and the sharp increase in the demand for underground space development, as the core carrier of the urban traffic framework, the line planning of the subway project is usually arranged along the main urban roads, passing through commercial and residential dense areas, and the station location is preferably considered at the road intersection to meet the passenger flow gathering and dispersing needs. Due to the limited urban ground space and the environmental constraints of surrounding buildings, pipelines, etc., the underground structure is usually constructed by the semi-top-down method or the top-down method. The cover plate of the top-down method is usually supported on the cast-in-place piles of the foundation pit. The cast-in-place piles need to retain soil and serve as the support points for the cover plate. Therefore, semi-piles are set within a certain height below the top of the cast-in-place piles.

[0003] At present, the construction plan for the semi-pile of the cast-in-place pile is to first install the steel reinforcement cage in the hole-forming area; then pour concrete to form a circular cast-in-place pile; and then chisel off the redundant concrete on the circular cast-in-place pile to form the semi-pile of the cast-in-place pile, resulting in a long construction period, and it is difficult to guarantee the quality of the semi-pile after chiseling a semi-circle on the whole cylinder. The transportation workload is large, and a large amount of concrete is seriously wasted. Summary of the Invention

[0004] The technical problem to be solved by the present invention is that it is difficult to guarantee the quality of the semi-pile after chiseling a semi-circle on the whole cylinder, the construction time is long, the transportation workload is large, and the production cost is high. The purpose is to provide a construction method and steel formwork for a semi-pile of a retaining pile for a shallow foundation pit of an underground structure, which is convenient for pouring concrete into the steel formwork during the construction of the semi-pile, preventing the concrete from flowing into the cavity area behind the semi-pile during pouring, enabling the semi-pile to be directly formed in the steel formwork, replacing chiseling the full pile into a semi-pile, reducing the construction cost, shortening the construction period, and ensuring the quality of the semi-pile.

[0005] The present invention is achieved by the following technical solutions: A construction method for a semi-pile of a retaining pile for a shallow foundation pit of an underground structure includes the following steps: S1: Install the steel reinforcement cage in the hole-forming area, and fix the steel reinforcement cage after it is hoisted in place and inspected qualified; S2: Use a conduit to pour concrete into the full-pile area; S3: Before the concrete in the full-pile area starts to set, hoist and sleeve the steel formwork outside the semi-pile steel reinforcement cage area, and fix the steel formwork when the lower end of the steel formwork is at the designed elevation position of the top of the full-pile; S4: Pour concrete into the semi-pile area; S5: After the concrete in the semi-pile area starts to set, hoist the steel formwork out.

[0006] The beneficial effects of the present invention are as follows: by installing a steel reinforcement cage in the hole-forming area, then pouring concrete in the entire pile area, and before the concrete in the entire pile area begins to set, hoisting and placing the steel form into the semi-pile steel reinforcement cage area, it is convenient to ensure that the lower end of the steel form is located at the designed elevation of the pile top of the entire pile, thereby ensuring the accuracy of the installation position of the steel form, ensuring the dimensional accuracy of the overall structure of the retaining pile composed of the semi-pile and the entire pile, and also facilitating pouring concrete into the steel form during the construction of the semi-pile to prevent the concrete from flowing into the cavity area behind the semi-pile during pouring, enabling the semi-pile to be directly formed, replacing the process of chiseling the entire pile into a semi-pile, reducing construction costs, shortening the construction period, and ensuring the quality of the semi-pile. Then, pour the semi-pile inside the steel form and remove the steel form after the concrete in the semi-pile area begins to set to prevent damage to the semi-pile structure when hoisting the steel form.

[0007] In some embodiments, it further includes step S6: after the semi-pile and the entire pile both reach the designed strength, backfill the empty pile area. Backfilling the empty pile area at the upper end of the entire pile can prevent workers or materials from falling into the empty pile area.

[0008] In some embodiments, it further includes constructing the top beam of the semi-pile and the top beam of the entire pile. After the construction of the semi-pile and the entire pile is completed, and after the backfill area and the foundation pit excavation surface are excavated to the designed elevation of the pile top of the semi-pile, construct the top beam of the semi-pile. After excavating all the backfill areas and excavating the foundation pit to the designed elevation of the pile top of the entire pile, construct the top beam of the entire pile. By excavating the backfill area and the foundation pit excavation surface after the construction of the semi-pile and the entire pile is completed, the area for constructing the top beam of the semi-pile is exposed to construct the top beam of the semi-pile. After excavating the foundation pit to the designed elevation of the pile top of the entire pile, then construct the top beam of the entire pile to enhance the stiffness and stability of the support system through the top beam of the semi-pile and at the same time transfer and distribute the loads around the foundation pit.

[0009] In some embodiments, several retaining rings are provided on the steel reinforcement cage, and the retaining rings are evenly distributed along the length direction of the steel reinforcement cage, and the distance between two adjacent retaining rings is 2m. By providing a retaining ring on the outer side of the steel reinforcement cage every 2m, support points of the steel reinforcement cage are formed to prevent the steel reinforcement cage from closely adhering to the hole wall due to its own weight or collision during the lowering process, ensuring uniform thickness of the protective layer.

[0010] In some embodiments, the concrete in the semi-pile area is poured before the initial setting of the concrete in the full-pile area. The pile tops of both the full-pile and the semi-pile are provided with an over-pouring height, and the over-pouring height is not less than 0.5 m. By pouring the concrete in the semi-pile area before the initial setting of the concrete in the full-pile area, the full-pile and the semi-pile can form an integral whole, ensuring the overall quality of the entire retaining pile. Also, during the concrete pouring process (especially underwater concrete pouring), mud, scum, cement slurry, etc. will float on the surface of the concrete, forming a "floating slurry layer" with relatively low strength. Therefore, by setting the over-pouring height, the floating slurry layer is lifted to ensure that the actual length of the pile body is not less than the designed length.

[0011] In some embodiments, steel bar protection sleeves are sleeved on the steel bar sections above the pile tops of both the semi-pile and the full-pile, and the steel bar protection sleeves are PVC pipes. Since the over-poured concrete at the steel bars anchored into the capping beam above the pile tops of the semi-pile and the full-pile needs to be chiseled off later, the steel bars anchored into the capping beam are protected by steel bar protection sleeves to prevent the concrete to be chiseled from solidifying on the steel bars and reduce the difficulty of chiseling the over-poured concrete.

[0012] In some embodiments, before the construction of the capping beam at the pile top of the full-pile and the capping beam at the pile top of the semi-pile, the over-poured concrete at the pile tops of the semi-pile and the full-pile is chiseled off and cleaned up. Before the construction of the capping beam at the pile top of the full-pile, the over-poured concrete at the pile top of the full-pile is chiseled off and cleaned up, so as to eliminate the hidden danger of floating slurry, ensure the reliability of the connection interface, meet the requirements of the structural design, and thus improve the integrity and structural safety of the pile-capping beam joint.

[0013] The present invention also provides a steel formwork for the semi-pile of the retaining pile in the shallow foundation pit of the underground structure. The steel formwork for the construction of the semi-pile of the shallow foundation pit retaining pile includes an arc-shaped steel plate and a flat steel plate. The virtual axis of the arc-shaped steel plate is coaxial with the virtual axis of the full-pile; the flat steel plate is welded to both sides of the arc-shaped steel plate to form a shell with a semi-circular cross-section, and the top of the flat steel plate is set at a distance higher than the arc-shaped steel plate.

[0014] By setting the flat steel plate welded to both sides of the arc-shaped steel plate to form a shell with a semi-circular cross-section, it is convenient to pour the concrete into the semi-circular cylinder formed by the flat steel plate and the arc-shaped steel plate during the construction of the semi-pile, preventing the concrete from flowing into the cavity area behind the semi-pile during pouring, enabling the semi-pile to be directly formed, replacing the cutting of the full-pile into the semi-pile, reducing the construction cost, shortening the construction period, and ensuring the quality of the semi-pile.

[0015] In some embodiments, the top of the flat steel plate is set at a distance higher than that of the arc-shaped steel plate, and several lifting holes are arranged at the top of the flat steel plate. By setting the top of the flat steel plate at a distance higher than that of the arc-shaped steel plate, it is convenient to arrange several lifting holes within the range of the set distance, prevent the lifting tool from contacting the cast concrete, ensure the quality of the cast concrete, and facilitate lifting the steel formwork during work to demold it from the already formed cast concrete.

[0016] In some embodiments, the set distance is 200 mm to 300 mm. By setting the distance to 200 mm to 300 mm, it is convenient to lift the steel formwork from the already formed cast concrete for demolding.

[0017] Compared with the prior art, the present invention has the following advantages and beneficial effects: 1. By providing the steel formwork, it is convenient to pour the concrete into the semi-cylindrical tube composed of the flat steel plate and the arc-shaped steel plate during the construction of the semi-pile, prevent the concrete from flowing into the cavity area behind the semi-pile during pouring, directly form the semi-pile, reduce the construction cost, shorten the construction period, and ensure the quality of the semi-pile.

[0018] 2. Pour the concrete in the semi-pile area before the concrete in the full-pile area starts to set, so that the full-pile and the semi-pile can form an integral body to ensure the overall quality of the entire retaining pile.

[0019] 3. Also, during the concrete pouring process (especially underwater concrete pouring), mud, scum, cement slurry, etc. will float on the surface of the concrete to form a "floating slurry layer" with relatively low strength. Therefore, by setting the overpour height, the floating slurry layer is lifted up to ensure that the actual length of the pile body is not less than the designed length. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] In order to more clearly illustrate the technical solutions of the exemplary embodiments of the present invention, the following will briefly introduce the drawings required for the embodiments. It should be understood that the following drawings only show some embodiments of the present invention, and therefore should not be regarded as limiting the scope. For those of ordinary skill in the art, without creative efforts, other related drawings can also be obtained based on these drawings. In the drawings: Figure 1 is a schematic structural diagram after performing step S1 in the present invention; Figure 2 is a schematic structural diagram after performing step S2 in the present invention; Figure 3 is a schematic structural diagram after performing step S3 in the present invention; Figure 4 is a schematic structural diagram after performing step S4 in the present invention; Figure 5It is a schematic structural diagram after performing step S5 in the present invention; Figure 6 It is a schematic structural diagram after performing step S6 in the present invention; Figure 7 It is a structural diagram after fabricating the top beam of the half-pile and the top beam of the full-pile in the present invention; Figure 8 It is a structural diagram of the steel formwork in the present invention; Figure 9 It is a partial structural diagram in the present invention.

[0021] Labels in the attached drawings and corresponding component names: Ground 1, empty pile area 2, steel reinforcement cage 3, steel reinforcement protection casing 4, retaining wall ring 5, concrete 6, steel formwork 7, arc-shaped steel plate 8, flat steel plate 9, lifting hole 10, top of the full-pile 11, top of the half-pile 12, top surface of the excess-poured concrete 13, backfill material in the empty pile area 14, top beam of the half-pile 15, top beam of the full-pile 16, foundation pit excavation surface 17, main reinforcement 18, hole wall 19. Detailed implementation manners

[0022] To make the objectives, technical solutions and advantages of the present invention clearer and more understandable, the present invention will be further described in detail below with reference to the embodiments and the attached drawings. The illustrative embodiments and descriptions thereof of the present invention are only used to explain the present invention and are not intended to limit the present invention.

[0023] Throughout the specification, the reference to "an embodiment", "embodiment", "an example" or "example" means that the specific features, structures or characteristics described in connection with that embodiment or example are included in at least one embodiment of the present invention. Thus, the phrases "an embodiment", "embodiment", "an example" or "example" appearing throughout the specification do not necessarily all refer to the same embodiment or example. In addition, the specific features, structures or characteristics can be combined in any suitable combination and / or sub-combination in one or more embodiments or examples. In addition, those of ordinary skill in the art should understand that the drawings provided herein are for illustrative purposes only and are not necessarily drawn to scale. The term "and / or" used herein includes any and all combinations of one or more of the related listed items.

[0024] In the description of the present invention, the orientation or positional relationship indicated by the terms "front", "rear", "left", "right", "upper", "lower", "vertical", "horizontal", "high", "low", "inner", "outer", etc. is based on the orientation or positional relationship shown in the attached drawings, and is only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and thus should not be construed as limiting the protection scope of the present invention.

[0025] In the present invention, terms such as "first" and "second" are used only to distinguish the corresponding components for the sake of clear description, and are not intended to limit any order or emphasize importance, etc. In addition, the term "connection" used herein, without special explanation, can be directly connected or indirectly connected via other components.

[0026] Embodiment 1 Refer to Figures 1-9 , Embodiment 1 of the present invention provides a construction method for a semi-pile of a retaining pile for a shallow foundation pit of an underground structure, including the following steps: S1: Install the steel reinforcement cage 3 in the hole-forming area. The steel reinforcement cage 3 shall not damage the hole wall 19. After the steel reinforcement cage 3 is hoisted in place and inspected to be qualified, fix the steel reinforcement cage 3; S2: Use a conduit to pour concrete 6 in the area of the whole pile; S3: Before the concrete in the area of the whole pile starts to set, hoist and install the steel formwork outside the area of the semi-pile steel reinforcement cage. When the lower end of the steel formwork is at the designed elevation of the pile top of the whole pile, fix the steel formwork; S4: Pour concrete 6 in the area of the semi-pile; S5: After the concrete 6 in the area of the semi-pile starts to set, and ensuring that the corners of the concrete 6 will not be damaged, hoist out the steel formwork 7.

[0027] By installing the steel reinforcement cage 3 in the hole-forming area, then pouring concrete 6 in the area of the whole pile, and also hoisting and placing the steel formwork 7 into the area of the semi-pile steel reinforcement cage 3 before the concrete 6 in the area of the whole pile starts to set, it is convenient to ensure that the lower end of the steel formwork 7 is at the designed elevation of the pile top of the whole pile, and further ensure the accuracy of the installation position of the steel formwork, so as to ensure the dimensional accuracy of the overall structure of the retaining pile composed of the semi-pile and the whole pile, replace chiseling the whole pile into a semi-pile, reduce construction costs, shorten the construction period, and ensure the quality of the semi-pile. Then pour the semi-pile inside the steel formwork 7 and take out the steel formwork after the concrete 6 in the area of the semi-pile starts to set, so as to prevent damage to the semi-pile structure when hoisting the steel formwork 7.

[0028] Refer to Figure 6 , and also includes step S6: After the semi-pile and the whole pile both reach the designed strength, backfill the empty pile area 2. Backfilling the empty pile area 2 at the upper end of the whole pile can prevent workers or materials from falling into the empty pile area 2. Specifically, the backfill material 14 for the cavity area can be selected as sand or the muck dug out on site, etc.

[0029] Refer to Figure 7, it also includes constructing a capping beam 15 at the top of the half-piles. The capping beam 15 at the top of the half-piles is constructed after all the half-piles and full-piles are completely constructed, and after the backfill area of the empty pile area 2 and the foundation pit excavation surface 17 are excavated to the designed elevation of the top of the half-piles 12. By excavating the backfill area and the foundation pit excavation surface 17 after all the half-piles and full-piles are completely constructed, the area for constructing the capping beam 15 at the top of the half-piles is exposed to construct the capping beam 15 at the top of the half-piles, so as to enhance the stiffness and stability of the support system through the capping beam 15 at the top of the half-piles, and at the same time transfer and distribute the loads around the foundation pit. The top of the capping beam 15 at the top of the half-piles is lower than the ground 1. See Figure 7 , it also includes constructing a capping beam 16 at the top of the full-piles. The capping beam 16 at the top of the full-piles is constructed after the foundation pit is excavated to the designed elevation of the top of the full-piles 11. By excavating the foundation pit to the designed elevation of the top of the full-piles 11 and then constructing the capping beam 16 at the top of the full-piles, the stiffness and stability of the support system are enhanced through the capping beam 15 at the top of the half-piles, and at the same time the loads around the foundation pit are transferred and distributed.

[0030] See Figure 7 , several retaining wall rings 5 are arranged on the steel reinforcement cage 3. The retaining wall rings 5 are evenly distributed along the length direction of the steel reinforcement cage 3, and the distance between two adjacent retaining wall rings 5 is 2 m. By arranging a retaining wall ring 5 on the outer side of the steel reinforcement cage 3 every 2 m, support points of the steel reinforcement cage 3 are formed to prevent the steel reinforcement cage 3 from closely adhering to the hole wall 19 due to its own weight or collision during the lowering process, and ensure the uniform thickness of the protective layer. Specifically, the steel reinforcement cage 3 includes main reinforcement bars 18, and the retaining wall rings 5 are connected to the outer sides of the main reinforcement bars 18.

[0031] See Figure 4 , the concrete 6 in the half-pile area is poured and completed before the concrete 6 in the full-pile area starts to set. The tops of both the full-piles and the half-piles are provided with a superpour height, and the distance between the top surface 13 of the superpoured concrete and the pile top is not less than 0.5 m. By pouring and completing the concrete 6 in the half-pile area before the concrete 6 in the full-pile area starts to set, the full-piles and the half-piles can form an integral body to ensure the overall quality of the entire retaining pile. Also, during the pouring process of the concrete 6 (especially underwater concrete pouring), slurry, floating slag, cement slurry, etc. will float on the surface of the concrete 6 to form a "floating slurry layer" with lower strength. Therefore, by setting a superpour height, the floating slurry layer is lifted to ensure that the actual length of the pile body is not less than the designed length.

[0032] See Figures 1-5 , the steel bar sections above the tops of both the half-piles and the full-piles are sleeved with steel bar protection sleeves 4, and the steel bar protection sleeves 4 are PVC pipes. Since the superpoured concrete 6 at the steel bars anchored into the capping beam above the tops of the half-piles and the full-piles needs to be chiseled off later, the steel bars anchored into the capping beam are protected by the steel bar protection sleeves 4 to prevent the concrete 6 to be chiseled off from solidifying on the steel bars and reduce the difficulty of chiseling off the superpoured concrete 6.

[0033] See Figures 1-5 , before the construction of the full-pile pile top capping beam 16 and the half-pile pile top capping beam 15, the excess concrete 6 at the half-pile pile top 12 and the full-pile pile top 11 is chiseled and cleaned. Before the construction of the full-pile pile top capping beam 16, the excess concrete 6 at the full-pile pile top 11 is chiseled and cleaned, so as to eliminate the hidden danger of floating slurry, ensure the reliability of the connection interface, meet the requirements of structural design, and thus improve the integrity and structural safety of the pile and capping beam joint.

[0034] Embodiment 2 See Figure 8 , this Embodiment 2 provides a steel formwork for the half-pile of the retaining pile in the shallow foundation pit of the underground structure, including an arc-shaped steel plate 8 and a flat steel plate 9. The virtual axis of the arc-shaped steel plate 8 is coaxial with the virtual axis of the full-pile; the flat steel plate 9 is welded to both sides of the arc-shaped steel plate 8 to form a semi-circular shell in cross-section, and the top of the flat steel plate 9 is set higher than the arc-shaped steel plate 8 by a distance.

[0035] See Figure 8 , the top of the flat steel plate 9 is set higher than the arc-shaped steel plate 8 by a distance, and several lifting holes 10 are arranged at the top of the flat steel plate 9. By setting the top of the flat steel plate 9 higher than the arc-shaped steel plate 8 by a distance, it is convenient to arrange several lifting holes 10 within the range of the distance, prevent the lifting tool from contacting the cast concrete 6, ensure the quality of the cast concrete 6, and facilitate lifting the steel formwork 7 during work to demold it from the already formed cast concrete 6. Specifically, the flat steel plate 9 and the arc-shaped steel plate 8 can be integrally formed. The top and bottom of the cylinder formed by the flat steel plate 9 and the arc-shaped steel plate 8 are both open.

[0036] See Figure 8 , the distance is 200mm - 300mm. By setting the distance to 200mm - 300mm, it is convenient to lift the steel formwork from the already formed cast concrete 6 for demolding. During specific operation, a demolding agent is applied to the inner side of the steel formwork 7. The types of demolding agents that can be selected are common knowledge in the art and will not be elaborated here.

[0037] The above specific embodiments have further elaborated on the purpose, technical solutions, and beneficial effects of the present invention. It should be understood that the above are only specific embodiments of the present invention and are not used to limit the protection scope of the present invention. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principles of the present invention shall be included in the protection scope of the present invention.

Claims

1. A construction method for semi-piles of retaining piles in shallow foundation pits of underground structures, characterized in that, It includes the following steps: S1: Install the steel reinforcement cage in the hole-forming area, and fix the steel reinforcement cage after it is hoisted in place and passes the inspection; S2: Pour concrete into the entire pile area using a conduit; S3: Before the concrete in the entire pile area begins to set, hoist and set the steel formwork outside the semi-pile steel reinforcement cage area, and fix the steel formwork when the lower end of the steel formwork is at the designed elevation of the pile top of the entire pile; S4: Pour concrete into the semi-pile area; S5: After the concrete in the semi-pile area begins to set, hoist out the steel formwork.

2. The construction method for the semi-pile of the retaining pile of the shallow foundation pit of the underground structure according to claim 1, characterized in that, It also includes step S6: After the semi-pile and the entire pile reach the designed strength, backfill the empty pile area.

3. The construction method for the semi-pile of the retaining pile of the shallow foundation pit of the underground structure according to claim 1, characterized in that, It also includes constructing the semi-pile pile top capping beam and the entire pile pile top capping beam. After the construction of the semi-pile and the entire pile is completed, and after the backfill area and the foundation pit excavation surface are excavated to the designed elevation of the semi-pile pile top, construct the semi-pile pile top capping beam, and after all the backfill areas are excavated and the foundation pit is excavated to the designed elevation of the entire pile pile top, construct the entire pile pile top capping beam.

4. The construction method for the semi-pile of the retaining pile of the shallow foundation pit of the underground structure according to claim 1, characterized in that, Several retaining rings are arranged on the steel reinforcement cage, and the retaining rings are evenly distributed along the length direction of the steel reinforcement cage, and the distance between two adjacent retaining rings is 2m.

5. The construction method for the semi-pile of the retaining pile in the shallow foundation pit of the underground structure according to claim 1, characterized in that, Before the concrete in the entire pile area begins to set, complete the pouring of the concrete in the semi-pile area. The pile tops of the entire pile and the semi-pile are both provided with an over-pouring height, and the over-pouring height is not less than 0.5m.

6. The construction method for the semi-pile of the retaining pile of the shallow foundation pit of the underground structure according to claim 1, characterized in that, The steel bar sections above the pile tops of the semi-pile and the entire pile are all sleeved with steel bar protection sleeves, and the steel bar protection sleeves are PVC pipes.

7. The construction method for the semi-pile of the retaining pile in the shallow foundation pit of the underground structure according to claim 3, characterized in that, Before the construction of the entire pile pile top capping beam and the semi-pile pile top capping beam, chisel and clean the over-poured concrete at the pile tops of the semi-pile and the entire pile.

8. A steel formwork for a semi-pile of a retaining pile in a shallow foundation pit of an underground structure, characterized in that, A construction method for a semi-pile of a shallow foundation pit retaining pile for an underground structure according to any one of claims 1-7, includes: An arc-shaped steel plate, the virtual axis of the arc-shaped steel plate is coaxial with the virtual axis of the entire pile; A flat steel plate, the flat steel plate is welded to both sides of the arc-shaped steel plate to form a shell with a semi-circular cross-section.

9. The steel form for the semi-pile of the retaining pile of the shallow foundation pit of the underground structure according to claim 8, characterized in that, The top of the flat steel plate is set higher than the arc-shaped steel plate by a set distance, and several lifting holes are arranged at the top of the flat steel plate.

10. The steel form for the semi-pile of the retaining pile in the shallow foundation pit of the underground structure according to claim 8, characterized in that, The set distance is 200mm - 300mm.

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