Novel differentiated reinforcement structure cast-in-situ bored pile for deep foundation pit with soft upper part and hard lower part

Abstract

The utility model belongs to the field of deep foundation pit cast-in-situ bored piles, and particularly relates to a novel differentiation reinforcement structure cast-in-situ bored pile for a deep foundation pit with a soft upper part and a hard lower part, which comprises a pile body, and the pile body comprises a reinforcement cage hoisted in the pile body and concrete poured around the reinforcement cage. According to the cast-in-situ bored pile disclosed by the utility model, different stress areas of the pile body are divided according to the actual stress condition of each area, and regional differentiated reinforcement design is carried out, so that the performance of reinforcing steel bars arranged at each part of the pile body of the cast-in-situ bored pile can be fully exerted, and the stability and the safety of a foundation pit in the excavation construction process are better ensured; and in addition, the use amount of steel bars of the cast-in-situ bored piles is reduced, waste in the construction process is reduced, and the engineering cost is saved for deep foundation pit engineering project construction.

Description

Technical Field

[0001] The utility model belongs to the field of bored cast-in-place piles for deep foundation pits, and particularly relates to a bored cast-in-place pile with a novel differential reinforcement structure for deep foundation pits with soft upper and hard lower strata. Background Art

[0002] The retaining pile, also called the foundation pit retaining structure, is a supporting structure for underground engineering. Its types mainly include double-axis mixing piles, triaxial mixing piles, high-pressure jet grouting piles, bored cast-in-place piles, tensile steel sheet piles, and steel sheet piles, etc. The main functions of the retaining pile are water stop and soil retention. Nowadays, in many cases, the retaining pile will also be combined with other supporting structures such as internal supports to jointly form a complete supporting system.

[0003] In current deep foundation pit projects, a considerable proportion of the geological structures of deep foundation pits are the soft upper and hard lower soil-rock dual structures, which are widely present in many areas. In the construction of deep foundation pit excavation, due to more extensive applicable conditions, the bored cast-in-place pile is the most commonly used retaining pile structure type. In the pile body structure, the steel reinforcement cage, as an indispensable and important part of it, needs to meet strict specification requirements during pre-design calculation. Generally, the stress condition of the most dangerous section of the pile body under the most unfavorable working conditions of the deep foundation pit project is used as the condition that the steel reinforcement cage of the overall retaining pile must meet during reinforcement calculation. Under such a premise, the stability and safety of deep foundation pit projects are better guaranteed.

[0004] However, within the pile length range or even within the same cross-section range, the stress conditions of different parts are different. The reinforcement conditions of some parts have exceeded the design requirements by a large margin. Especially in deep foundation pits with soft upper and hard lower soil-rock dual structures, the most dangerous section generally appears within the range of the soil layer with weaker strength, while the lower rock layer has a hard texture and high strength. The reinforcement of the retaining pile designed according to the soil part has exceeded the requirements for rock mass support by a large margin. Such a reinforcement method is conservative, resulting in a high construction cost. At the same time, excessive reinforcement will also limit the full play of the tensile performance of the steel bars, which will instead reduce the performance of the retaining pile and may even be more prone to damage. It is not only uneconomical and unreasonable but also may have certain potential safety hazards. Summary of the Utility Model

[0005] In view of the various deficiencies of the prior art, the inventor has studied and designed a bored cast-in-place pile with a novel differential reinforcement structure for deep foundation pits with soft upper and hard lower strata through long-term practice. According to the soft upper and hard lower soil-rock dual structure, differential reinforcement is carried out, which improves the tensile performance of the steel reinforcement cage and reduces the cost at the same time.

[0006] To achieve the above object, the utility model provides the following technical solutions:

[0007] A bored pile with a new differentiated reinforcement structure for a deep foundation pit with a soft upper part and a hard lower part comprises a pile body, the pile body comprises a steel cage hoisted therein, and concrete poured around the steel cage. The steel cage comprises a plurality of tension zone steel bars and a plurality of compression zone steel bars extending longitudinally. The plurality of tension zone steel bars are evenly spaced and arranged in a semi-cylindrical shape, the plurality of compression zone steel bars are evenly spaced and arranged in a semi-cylindrical shape, and the plurality of tension zone steel bars and the plurality of compression zone steel bars are arranged together in a cylindrical shape.

[0008] The steel cage is also provided with a plurality of stirrups, which are annular and evenly spaced from top to bottom. The upper part of the steel cage is also provided with a plurality of supporting and reinforcing steel bars in the tension zone and a plurality of supporting and reinforcing steel bars in the compression zone. A supporting and reinforcing steel bar in the tension zone is provided between every two steel bars in the tension zone, and a supporting and reinforcing steel bar in the compression zone is provided between every two steel bars in the compression zone. The top ends of the supporting and reinforcing steel bars in the tension zone are flush with the top ends of the supporting and reinforcing steel bars in the compression zone, and the top ends of the steel bars in the tension zone are flush with the top ends of the steel bars in the compression zone. A hoisting positioning plate is also provided on the top of the steel cage.

[0009] Furthermore, each stirrup is welded and fixed to the contact position of each steel bar in the tension zone, and each stirrup is welded and fixed to the contact position of each steel bar in the compression zone.

[0010] Furthermore, each stirrup is welded and fixed to the contact position of each support reinforcement tensile zone steel bar, and each stirrup is welded and fixed to the contact position of each support reinforcement compressive zone steel bar.

[0011] Furthermore, the lengths of the steel bars in the support and reinforcement tension zone are equal to the lengths of the steel bars in the support and reinforcement compression zone.

[0012] Furthermore, the lengths of the steel bars in the tension zone and the steel bars in the compression zone are equal.

[0013] Furthermore, the supporting reinforcement steel bars in the tension zone and the supporting reinforcement steel bars in the compression zone are steel bars with a length of 12 m, and the tensile zone steel bars and the compression zone steel bars are steel bars with a length of 22.5 m.

[0014] Furthermore, the supporting reinforcement steel bars in the tension zone and the steel bars in the tension zone are both 5 C25 steel bars, and the supporting reinforcement steel bars in the compression zone and the steel bars in the compression zone are both 5 C14 steel bars.

[0015] Furthermore, the hoisting positioning plate includes a first positioning plate and a second positioning plate which are vertically arranged.

[0016] Furthermore, the first positioning plate and the second positioning plate are fixed by bolts.

[0017] Further, both ends of the first positioning plate are fixedly welded to the steel reinforcement cage, and both ends of the second positioning plate are also fixedly welded to the steel reinforcement cage.

[0018] The beneficial effects of the present utility model are as follows:

[0019] According to the actual stress conditions in each area, different stress areas of the pile body are divided, and differential reinforcement design is carried out for each area, so that the performance of the steel bars arranged in each part of the bored cast-in-place pile can be fully exerted, better ensuring the stability and safety of the foundation pit during the excavation construction process, reducing the amount of steel bars used in the bored cast-in-place pile, reducing waste during the construction process, and saving engineering costs for the construction of such deep foundation pit engineering projects. Description of the Drawings

[0020] Figure 1 is a schematic structural view of the present utility model;

[0021] Figure 2 is a top view of the present utility model.

[0022] In the drawings:

[0023] 1 - pile body, 10 - steel reinforcement cage, 11 - tension reinforcement in the support strengthening area, 12 - compression reinforcement in the support strengthening area,

[0024] 13 - tension reinforcement, 14 - compression reinforcement, 15 - stirrup,

[0025] 16 - hoisting positioning plate, 161 - first positioning plate, 162 - second positioning plate. Detailed Embodiment

[0026] In order to enable those skilled in the art to better understand the technical solutions of the present utility model, the technical solutions of the present utility model will be clearly and completely described below in conjunction with the drawings of the present utility model. Based on the embodiments in this application, other similar embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the scope of protection of this application. In addition, the directional terms mentioned in the following embodiments, such as "upper", "lower", "left", "right", etc., are only with reference to the directions in the drawings. Therefore, the directional terms used are for illustration rather than to limit the present utility model.

[0027] The present utility model will be further described below in conjunction with the drawings and preferred embodiments.

[0028] Referring to Figure 1 and Figure 2 , a bored cast-in-place pile with a novel differential reinforcement structure for a soft upper and hard lower deep foundation pit of the present utility model includes a pile body 1. The pile body 1 includes a steel reinforcement cage 10 hoisted therein and concrete poured around the steel reinforcement cage 10.

[0029] The bored pile of the utility model has a steel cage 10 inside which is designed in advance before construction and divided into different stress-bearing areas. Different stress-bearing areas use the amount of reinforcement that meets the corresponding design requirements, and arrange the corresponding steel bar layout, and then hoist and position it, so that the steel cage 10 can be accurately placed in the pile body 1, ensuring that the orientation of each stress-bearing area in the pile body 1 is consistent with the pre-designed one. Due to the different forces on the foundation pit in the spatial dimension, different foundation pit pile positions need to be designed with steel cages 10 with different differentiated reinforcements, so that the new bored pile can be customized.

[0030] The utility model divides the stress area of ​​the steel cage according to the results obtained by the deep foundation pit support structure design software and the finite element simulation software. There are two ranges of areas here: the pile cross-section range and the pile length range. The cross-section range is mainly divided into the tension zone and the compression zone. A circular cross-section pile is used, and the cross-section diameter line parallel to the foundation pit boundary line is used as the dividing line to divide it into the tension zone and the compression zone. According to the binary structure of the rock and soil layer of the deep foundation pit, the pile length range is divided into the branch reinforcement and the non-reinforcement area. The cast-in-place pile area corresponding to the weak and easily damaged soil layer is supported and strengthened; the lower rock layer has high strength and good stability, and the corresponding cast-in-place pile does not need a strong support capacity, and this area does not need to be strengthened. If more complex soil-rock combination geological conditions are encountered, for example, the rock mass is divided into weathered rock layers of different strengths due to different degrees of weathering, and then the cast-in-place pile length range is further subdivided according to the specific rock mass strength and stability, and the support area is increased or decreased. The support capacity is calculated.

[0031] The steel cage 10 of the utility model comprises a plurality of tension zone steel bars 13 and a plurality of compression zone steel bars 14 extending longitudinally. The plurality of tension zone steel bars 13 are evenly spaced and arranged in a semi-cylindrical shape, and the plurality of compression zone steel bars 14 are evenly spaced and arranged in a semi-cylindrical shape. The plurality of tension zone steel bars 13 and the plurality of compression zone steel bars 14 are arranged together in a cylindrical shape.

[0032] A plurality of stirrups 15 are also provided on the steel cage 10. The stirrups 15 are annular and evenly spaced from top to bottom. Each stirrup 15 is welded and fixed to the contact position of each tensile zone steel bar 13. Similarly, each stirrup 15 is welded and fixed to the contact position of each compressive zone steel bar 14.

[0033] A plurality of supporting and reinforcing steel bars 11 for the tension zone and a plurality of supporting and reinforcing steel bars 12 for the compression zone are also provided on the upper part of the steel cage 10. A supporting and reinforcing steel bar 11 for the tension zone is provided between every two steel bars 13 for the tension zone, and a supporting and reinforcing steel bar 12 for the compression zone is provided between every two steel bars 14 for the compression zone. Each stirrup 15 is welded and fixed at the contact position with each supporting and reinforcing steel bar 11 for the tension zone, and similarly, each stirrup 15 is welded and fixed at the contact position with each supporting and reinforcing steel bar 12 for the compression zone.

[0034] In this embodiment, the lengths of the tension-reinforced bars 11 and the compression-reinforced bars 12 for support strengthening are equal, and the lengths of the tension bars 13 and the compression bars 14 are equal. The top ends of the tension-reinforced bars 11 for support strengthening and the top ends of the compression-reinforced bars 12 for support strengthening are flush with each other, and the top ends of the tension bars 13 and the top ends of the compression bars 14 are flush with each other.

[0035] In this embodiment, the tension-reinforced bars 11 and the compression-reinforced bars 12 for support strengthening are steel bars with a length of 12 m, and the tension bars 13 and the compression bars 14 are steel bars with a length of 22.5 m. Both the tension-reinforced bars 11 and the tension bars 13 for support strengthening are 5 C25 steel bars, and both the compression-reinforced bars 12 and the compression bars 14 for support strengthening are 5 C14 steel bars.

[0036] See Figure 1 and Figure 2 , a hoisting positioning plate 16 is also provided at the top of the steel cage 10 in this embodiment. The hoisting positioning plate 16 includes a first positioning plate 161 and a second positioning plate 162 that are vertically arranged. The first positioning plate 161 and the second positioning plate 162 are bolted together. Both ends of the first positioning plate 161 are welded and fixed to the steel cage 10, and both ends of the second positioning plate 162 are also welded and fixed to the steel cage.

[0037] In this embodiment, a pointing arrow mark is marked on the hoisting positioning plate 16, pointing to the side close to the foundation pit. In this way, when hoisting and placing the steel cage 10, cooperating with the hoisting machinery, it can ensure that the position of the steel cage 10 in the pile body 1 is consistent with the pre-designed position, enabling the performance of the new cast-in-place bored pile to be normally exerted.

[0038] The utility model has been successfully applied to the excavation project of a deep foundation pit with a soil-rock dual structure in a certain subway station. The new-structured cast-in-place bored pile with regional differential reinforcement can achieve almost the same support control ability as the previous traditional retaining structure by adjusting the reinforcement in different areas of the pile body. When the excavation is completed, the maximum horizontal displacement of the retaining structure and the surrounding rock and soil mass only increases by 1.46%, and the maximum settlement displacement of the surrounding ground surface only increases by 1.31%. Moreover, 343 tons of steel bars can be saved, and the construction cost can be saved by 807,000 yuan. The economic benefit is remarkable. While achieving sufficient support strength, the utility model significantly saves the project cost for the project construction.

[0039] The above has made a detailed description of the utility model. The above description is only the preferred embodiment of the utility model, and it cannot limit the scope of the utility model. That is, all equal changes and modifications made according to the scope of this application should still fall within the scope covered by the utility model.

Claims

1. A bored pile with a new differential reinforcement structure for deep foundation pits with soft upper part and hard lower part, characterized in that, The pile body (1) comprises a steel cage (10) hoisted therein, and concrete poured around the steel cage (10); The steel cage (10) comprises a plurality of tension zone steel bars (13) and a plurality of compression zone steel bars (14) extending longitudinally; The plurality of tension zone steel bars (13) are evenly spaced and arranged in a semi-cylindrical shape, the plurality of compression zone steel bars (14) are evenly spaced and arranged in a semi-cylindrical shape, and the plurality of tension zone steel bars (13) and the plurality of compression zone steel bars (14) are arranged together in a cylindrical shape; The steel cage (10) is also provided with a plurality of stirrups (15), which are annular and evenly spaced from top to bottom; The upper part of the steel cage (10) is also provided with a plurality of supporting and reinforcing steel bars (11) in the tension zone and a plurality of supporting and reinforcing steel bars (12) in the compression zone; a supporting and reinforcing steel bar (11) in the tension zone is provided between every two steel bars (13) in the tension zone, and a supporting and reinforcing steel bar (12) in the compression zone is provided between every two steel bars (14) in the compression zone; The top end of the supporting and reinforcing steel bar (11) in the tension zone is flush with the top end of the supporting and reinforcing steel bar (12) in the compression zone, and the top end of the steel bar (13) in the tension zone is flush with the top end of the steel bar (14) in the compression zone; A hoisting positioning plate (16) is also provided on the top of the steel cage (10).

2. The bored cast-in-place pile with a new type of differential reinforcement structure for soft upper and hard lower deep foundation pits according to claim 1, characterized in that, Each stirrup (15) is welded and fixed at a contact position with each steel bar (13) in the tension zone, and each stirrup (15) is welded and fixed at a contact position with each steel bar (14) in the compression zone.

3. The bored cast-in-place pile of the novel differential reinforcement structure for the upper-soft and lower-hard deep foundation pit according to claim 2, characterized in that, Each stirrup (15) is welded and fixed at the contact position with each support reinforcement tension zone steel bar (11), and each stirrup (15) is welded and fixed at the contact position with each support reinforcement compression zone steel bar (12).

4. The bored cast-in-place pile with a new type of differential reinforcement structure for deep foundation pits with soft upper and hard lower parts according to claim 1, characterized in that, The lengths of the supporting and reinforcing steel bars (11) in the tension zone are equal to the lengths of the supporting and reinforcing steel bars (12) in the compression zone.

5. The bored cast-in-place pile with a new type of differential reinforcement structure for soft upper and hard lower deep foundation pits according to claim 4, characterized in that, The lengths of the tension zone steel bars (13) and the compression zone steel bars (14) are equal.

6. The bored cast-in-place pile with a new type of differential reinforcement structure for deep foundation pits with soft upper and hard lower parts according to claim 5, characterized in that, The supporting and reinforcing steel bars (11) in the tension zone and the supporting and reinforcing steel bars (12) in the compression zone are steel bars with a length of 12 m, and the supporting and reinforcing steel bars (13) in the tension zone and the supporting and reinforcing steel bars (14) in the compression zone are steel bars with a length of 22.5 m.

7. A bored cast-in-place pile with a novel differential reinforcement structure for a deep foundation pit with a soft upper part and a hard lower part according to claim 6, characterized in that, The supporting and reinforcing steel bars (11) in the tension zone and the steel bars (13) in the tension zone are both 5 C25 steel bars, and the supporting and reinforcing steel bars (12) in the compression zone and the steel bars (14) in the compression zone are both 5 C14 steel bars.

8. A bored pile with a new type of differential reinforcement structure for a soft - upper and hard - lower deep foundation pit according to claim 1, characterized in that, The hoisting positioning plate (16) comprises a first positioning plate (161) and a second positioning plate (162) which are arranged vertically.

9. The bored cast-in-place pile with a new type of differential reinforcement structure for deep foundation pits with soft upper and hard lower parts according to claim 8, characterized in that, The first positioning plate (161) and the second positioning plate (162) are fixed by bolts.

10. The cast-in-place bored pile with a novel differential reinforcement structure for a soft-top and hard-bottom deep foundation pit according to claim 9, characterized in that, Both ends of the first positioning plate (161) are fixedly welded to the steel cage (10), and both ends of the second positioning plate (162) are also fixedly welded to the steel cage (10).

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