Pile foundation for isolating pile side soil or rock frictional resistance
By designing pile caps, isolation piles, and rock-embedded piles in the pile foundation, and combining them with steel casings and dry coarse sand filling layers, the problem of soil or rock friction on the pile side was solved, the stability and bearing capacity of the pile foundation were improved, the impact of negative skin friction on the pile body was reduced, and the safety and economic benefits of the project were enhanced.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Utility models(China)
- Current Assignee / Owner
- CMCU ENG
- Filing Date
- 2025-04-29
- Publication Date
- 2026-05-19
AI Technical Summary
In civil engineering, the problem of skin friction between the soil or rock on the side of the pile and the pile body, especially negative skin friction, leads to a decrease in the bearing capacity of the pile foundation and potential structural damage. Existing technologies are difficult to effectively isolate and mitigate this mechanical challenge, especially in soft soil foundations, liquefiable soil layers, slope buildings and foundation pit support.
The design adopts a top-down connection of pile cap, isolation section pile foundation and rock-socketed section pile foundation, combined with structural measures such as steel casing, dry coarse sand filling layer, waterproof sealing and steel ring plate, to isolate the soil or rock friction resistance of the pile side, and to enhance the stability of the pile foundation by setting reinforced concrete pile wall and cement mortar leveling layer.
Effectively isolates soil or rock friction on the pile side, improves the stability and bearing capacity of the pile foundation, reduces the impact of negative skin friction, reduces the risk of landslides, and enhances the safety and economic benefits of the project.
Smart Images
Figure CN224259348U_ABST
Abstract
Description
Technical Field
[0001] This utility model belongs to the field of civil engineering and relates to a pile foundation for isolating soil or rock friction resistance of the pile. Background Technology
[0002] In practical civil engineering, pile foundations serve as the stable "roots" of a building, and their performance directly affects the safety and lifespan of the structure. However, with the continuous expansion of project scale and the increasing complexity of geological conditions, the interaction between the soil or rock along the pile and the pile body has become increasingly prominent, becoming one of the key factors restricting project quality and safety. Especially in the following typical engineering scenarios, how to effectively isolate the skin friction of the soil or rock along the pile has become an urgent technical challenge to be solved.
[0003] First, the negative impact of negative skin friction on piles should not be underestimated. In soft soil foundations or easily liquefied soil layers, piles often bear additional downward frictional forces due to soil settlement or liquefaction, i.e., negative skin friction. This force not only weakens the bearing capacity of the pile foundation but may also lead to stress concentration in the pile body, accelerating pile aging and even failure. For example, in some coastal areas, due to seawater erosion and the characteristics of soft soil, pile foundations have been subjected to negative skin friction for a long time, resulting in varying degrees of settlement and tilting, seriously threatening the safety of buildings. Therefore, eliminating or mitigating this negative skin friction has become the primary task in ensuring the stability of pile foundations.
[0004] Secondly, controlling the vertical force transmitted from the piles to the landslide body is a major challenge in the design of pile foundations for buildings on slopes or near landslides. When a building's pile foundation is located on an unstable slope, the piles must not only bear the load of the superstructure but also resist the slope's downward tendency. If this vertical force cannot be effectively isolated and dispersed, it may exacerbate slope deformation or even trigger a landslide, causing catastrophic consequences. In reality, many mountainous buildings have experienced frequent landslides due to improper pile foundation design, resulting in huge losses to people's lives and property.
[0005] Furthermore, with the continuous development of urban underground space, the interaction between deep foundation pit support piles and the surrounding soil is becoming increasingly prominent. During the excavation of the foundation pit, the support piles not only have to withstand the lateral pressure of the soil, but also face the negative skin friction generated by the unloading of the soil. This complex mechanical environment can easily lead to the instability of the support piles, thereby affecting the overall safety of the foundation pit. In some large-scale urban subway construction projects, unreasonable design of support piles has led to foundation pit collapses, causing serious social impacts.
[0006] To address the above issues, continuous exploration and innovation are needed, along with a series of technical measures to isolate the soil or rock friction on the pile side. Utility Model Content
[0007] In view of this, the purpose of this utility model is to provide a pile foundation that isolates the soil or rock friction resistance of the pile side, effectively isolates the negative skin friction resistance of the pile side, and reduces the vertical force transmission of the pile foundation of the building at the top of the slope to the sliding body.
[0008] To achieve the above objectives, this utility model provides the following technical solution:
[0009] A pile foundation for isolating soil or rock skin friction includes a cap, an isolation section pile foundation, and a rock-embedded section pile foundation connected sequentially from top to bottom. A steel casing is provided on the outer periphery of the isolation section pile foundation, and a dry coarse sand filling layer is provided between the steel casing and the pile hole sidewall. A waterproof seal is provided at the top of the dry coarse sand filling layer, and a steel ring plate surrounds the pile at the bottom. The steel ring plate is welded to the steel casing. A reinforced concrete pile retaining wall is also provided between the dry coarse sand filling layer and the pile hole sidewall. The reinforced concrete pile retaining wall is located in the soil layer or strongly weathered rock layer section of the isolation section pile foundation near the cap.
[0010] Optionally, the steel ring plate is provided with a cement mortar smoothing layer on the side near the rock-embedded pile foundation, and the cement mortar smoothing layer fills the bottom of the dry coarse sand filling layer.
[0011] Optionally, the thickness of the cement mortar smoothing layer is 45-55 mm.
[0012] Optionally, the isolation section pile foundation is embedded in the pile cap, and a cushion layer is provided between the pile cap and the pile hole.
[0013] Optionally, the cushion layer includes a 90-120mm thick concrete cushion layer and a 90-120mm thick mattress layer; the concrete cushion layer and mattress layer are made of medium-coarse sand with a particle size of less than or equal to 20mm and a compaction degree of less than or equal to 0.9.
[0014] Optionally, the steel ring plate is disposed at the connection between the isolation section pile foundation and the rock-socketed section pile foundation.
[0015] Optionally, the steel casing is a coiled steel plate with a thickness of 8 to 12 mm.
[0016] Optionally, the steel ring plate is 8-12mm wide and 45-55mm thick.
[0017] Optionally, the length of the isolation section pile foundation is greater than 10m.
[0018] The beneficial effects of this utility model are as follows:
[0019] This invention provides a technical measure that can effectively isolate the soil or rock friction resistance on the pile side, and it has been successfully applied in actual engineering projects.
[0020] This invention, through a specific structural design including the installation of a steel casing, filling with dry coarse sand, and waterproof sealing, effectively isolates the soil or rock friction resistance along the pile side. Verification was conducted through a self-balancing static load test; the test results show that the isolation efficiency of this invention for pile side resistance can reach over 80%, significantly improving the isolation efficiency.
[0021] By isolating the soil or rock friction on the pile side, the pile foundation of this utility model helps to reduce the adverse external forces on the pile body, thereby enhancing the stability and bearing capacity of the pile foundation. This is of great significance for eliminating or reducing the negative skin friction on the pile side and reducing the vertical force transmitted from the pile foundation of the building at the top of the slope to the sliding body range, and helps to improve the safety of the overall project.
[0022] By improving the stability and bearing capacity of pile foundations, this invention also helps reduce the cost of later maintenance and repair, further enhancing the economic benefits of the project.
[0023] The proposal and implementation of this utility model not only solved the technical problems in actual engineering, improved the safety and stability of the project, but also improved construction efficiency and economic benefits, and promoted the innovation and development of related technologies.
[0024] Other advantages, objectives, and features of this invention will be set forth in part in the description which follows, and in part will be apparent to those skilled in the art from the following examination and study, or may be learned from practice of this invention. The objectives and other advantages of this invention can be realized and obtained through the following description. Attached Figure Description
[0025] To make the objectives, technical solutions, and advantages of this utility model clearer, the preferred embodiments of this utility model will be described in detail below with reference to the accompanying drawings, wherein:
[0026] Figure 1 This is a cross-sectional schematic diagram of the present invention;
[0027] Figure 2 for Figure 1 A schematic diagram of the AA cross-section;
[0028] Figure 3 for Figure 1 An enlarged schematic diagram of part 1;
[0029] Figure 4 This table shows the results of the self-balancing test of the foundation piles of this invention and two other isolation schemes.
[0030] Figure label:
[0031] 1. Foundation, 2. Concrete pad, 3. Mattress pad.
[0032] 4. Isolation section pile foundation, 5. Steel casing, 6. Dry coarse sand filling layer, 7. Waterproof sealing, 8. Steel ring plate, 9. Cement mortar leveling layer, 10. Rock-embedded section pile foundation, 11. Reinforced concrete pile wall. Detailed Implementation
[0033] The following specific examples illustrate the implementation of this utility model. Those skilled in the art can easily understand other advantages and effects of this utility model from the content disclosed in this specification. This utility model can also be implemented or applied through other different specific embodiments, and various details in this specification can also be modified or changed based on different viewpoints and applications without departing from the spirit of this utility model. It should be noted that the illustrations provided in the following embodiments are only schematic representations of the basic concept of this utility model. Unless otherwise specified, the following embodiments and features in the embodiments can be combined with each other.
[0034] The accompanying drawings are for illustrative purposes only and are schematic diagrams, not actual pictures. They should not be construed as limiting the present invention. To better illustrate the embodiments of the present invention, some parts in the drawings may be omitted, enlarged, or reduced, and do not represent the actual product dimensions. It is understandable to those skilled in the art that some well-known structures and their descriptions may be omitted in the drawings.
[0035] In the accompanying drawings of this utility model, the same or similar reference numerals correspond to the same or similar components. In the description of this utility model, it should be understood that if terms such as "upper," "lower," "left," "right," "front," and "rear" indicate the orientation or positional relationship based on the orientation or positional relationship shown in the drawings, they are only for the convenience of describing this utility model and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, the terms used to describe positional relationships in the drawings are only for illustrative purposes and should not be construed as limiting this utility model. For those skilled in the art, the specific meaning of the above terms can be understood according to the specific circumstances.
[0036] Example 1
[0037] Please see Figures 1-3This is a type of pile foundation designed to isolate soil or rock friction, comprising, from top to bottom, a pile cap 1, an isolation section pile foundation 4, and a rock-embedded section pile foundation 10. A steel casing 5 is provided on the outer periphery of the isolation section pile foundation 4, and a dry coarse sand filling layer 6 is provided between the steel casing 5 and the pile hole sidewall. A waterproof seal 7 is provided at the top of the dry coarse sand filling layer 6, and a steel ring plate 8 surrounds the pile at the bottom. The steel ring plate 8 is welded to the steel casing 5. A reinforced concrete pile wall 11 is also provided between the dry coarse sand filling layer 6 and the pile hole sidewall. A cement mortar smoothing layer 9 is provided on the side of the steel ring plate 8 near the rock-embedded section pile foundation 10, filling the bottom of the dry coarse sand filling layer 6. Both the steel ring plate 8 and the cement mortar smoothing layer 9 are located at the connection between the isolation section pile foundation 4 and the rock-embedded section pile foundation 10.
[0038] The isolation section pile foundation 4 is embedded in the pile cap 1. A 90-120mm thick concrete cushion layer 2 and a 90-120mm thick mattress layer 3 are provided between the pile cap 1 and the pile hole.
[0039] The thickness of the cement mortar leveling layer 9 is 45-55mm.
[0040] Concrete cushion layer 2 and mattress layer 3 are made of medium-coarse sand with a particle size of less than or equal to 20mm and a compaction degree of less than or equal to 0.9.
[0041] The steel casing 5 is made of rolled steel plate with a thickness of 8-12mm.
[0042] The steel ring plate is 8-12mm wide and 45-55mm thick.
[0043] The length of the isolation section pile foundation 4 is greater than 10m.
[0044] Example 2
[0045] Based on the above embodiment 1, this embodiment further specifies that the thickness of the concrete cushion layer 2 and the mattress layer 3 are both 100mm; the cement mortar leveling layer 9 uses M5 cement mortar with a thickness of 50mm; the steel casing 5 has a thickness of 10mm; and the steel ring plate 8 has a width of 10mm and a thickness of 50mm.
[0046] Example 3
[0047] Based on the above embodiment one or embodiment two, the reinforced concrete pile retaining wall 11 in this embodiment is only set in the soil layer section or strongly weathered rock layer section of the isolation section pile foundation 4 near the pile cap 1.
[0048] This utility model has been successfully applied to actual engineering projects and verified through self-balancing static load tests. During the testing phase, three isolation schemes were selected for comparative verification: ① a steel casing + dry coarse sand isolation scheme (this utility model) around the piles, with pile numbers 12#-07, 12#-21, and 12#-22; ② a flexible asphalt felt isolation scheme around the piles, with pile numbers 7#-110, 7#-118, and 7#-119; ③ a galvanized iron sheet isolation scheme around the piles, with pile numbers 12#-16, 8#-99, and 12#-23. Pile foundations of the same diameter were selected, and the above isolation measures were implemented for each group of three piles, for a total of three groups of nine piles. Figure 4 As shown in the table of self-balancing test results of the foundation piles, the test results show that when the six test piles using isolation schemes ② and ③ were loaded to the maximum force value of 3000kN, the concrete at the load box position did not crack and the displacement did not change. It can be indirectly concluded that the side resistance of a single pile in the isolation section is greater than the load value minus the self-weight of the isolation layer and the tensile cracking value of the concrete at the load box position (>1500kN, >1800kN). The side resistance of a single pile in the isolation section of the three test piles using isolation scheme ① (this utility model patent) is 564.4kN, 291.8kN, and 839.7kN, respectively, and the isolation efficiency of the pile side resistance reaches more than 80%.
[0049] In summary, the side resistance of the isolated piles in the three test piles using this utility model (isolation scheme ①) is significantly reduced, and the isolation efficiency for pile side resistance reaches more than 80%, which is far higher than other comparative schemes (isolation schemes ② and ③).
[0050] In soft soil foundations, liquefiable soil layers, or other soil layers prone to settlement, piles are often subjected to downward frictional forces, i.e., negative skin friction. This force reduces the bearing capacity of the pile foundation and may even lead to pile failure. This invention effectively isolates the direct contact between the pile and the soil by setting a steel casing 5 and a dry coarse sand filling layer 6 around the outer perimeter of the isolation section pile foundation 4, thereby significantly reducing the negative skin friction of the pile side and improving the bearing capacity and stability of the pile foundation.
[0051] In the design of pile foundations for buildings on slopes or near landslides, reducing the vertical force transmitted from the pile to the landslide body is an important issue. This invention, through the design of the isolation section pile foundation 4, successfully reduces the interaction between the pile and the surrounding soil, thereby reducing the vertical force transmitted from the pile foundation to the landslide body and helping to prevent geological disasters such as landslides.
[0052] The design and construction of pile foundations often face numerous challenges due to varying geological conditions. This invention, by flexibly adjusting structural parameters such as the steel casing 5, the dry coarse sand filling layer 6, and the steel ring plate 8, can adapt to the characteristics of different soil and rock layers, thereby improving the applicability and stability of pile foundations under complex geological conditions.
[0053] Finally, it should be noted that the above embodiments are only used to illustrate the technical solution of this utility model and are not intended to limit it. Although this utility model has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solution of this utility model without departing from the spirit and scope of this technical solution, and all such modifications or substitutions should be covered within the scope of the claims of this utility model.
Claims
1. A pile foundation for isolating soil or rock skin friction, characterized in that: The structure includes a pile cap (1), an isolation section pile foundation (4), and a rock-socketed section pile foundation (10) connected sequentially from top to bottom. A steel casing (5) is provided on the outer periphery of the isolation section pile foundation (4), and a dry coarse sand filling layer (6) is provided between the steel casing (5) and the side wall of the pile hole. A waterproof seal (7) is provided at the top of the dry coarse sand filling layer (6), and a steel ring plate (8) is provided at the bottom to surround the pile. The steel ring plate (8) is welded to the steel casing (5). A reinforced concrete pile wall (11) is also provided between the dry coarse sand filling layer (6) and the side wall of the pile hole. The reinforced concrete pile wall (11) is located in the soil layer or strongly weathered rock layer of the isolation section pile foundation (4) near the pile cap (1).
2. The pile foundation for isolating soil or rock skin friction as described in claim 1, characterized in that: The steel ring plate (8) is provided with a cement mortar smoothing layer (9) on the side near the rock-embedded section pile foundation (10), and the cement mortar smoothing layer (9) fills the bottom of the dry coarse sand filling layer (6).
3. The pile foundation for isolating soil or rock skin friction according to claim 2, characterized in that: The thickness of the cement mortar smoothing layer (9) is 45~55mm.
4. The pile foundation for isolating soil or rock skin friction as described in claim 1, characterized in that: The isolation section pile foundation (4) is embedded in the pile cap (1), and a cushion layer is provided between the pile cap (1) and the pile hole.
5. The pile foundation for isolating soil or rock skin friction according to claim 4, characterized in that: The cushion layer includes a 90-120mm thick concrete cushion layer (2) and a 90-120mm thick mattress layer (3); the concrete cushion layer (2) and mattress layer (3) are made of medium-coarse sand with a particle size of less than or equal to 20mm and a compaction degree of less than or equal to 0.
9.
6. The pile foundation for isolating soil or rock skin friction according to claim 1, characterized in that: The steel ring plate (8) is installed at the connection between the isolation section pile foundation (4) and the rock-socketed section pile foundation (10).
7. The pile foundation for isolating soil or rock skin friction according to claim 1, characterized in that: The steel casing (5) is a coiled steel plate with a thickness of 8~12mm.
8. The pile foundation for isolating soil or rock skin friction according to claim 1, characterized in that: The steel ring plate (8) is 8~12mm wide and 45~55mm thick.
9. The pile foundation for isolating soil or rock skin friction according to claim 1, characterized in that: The length of the isolation section pile foundation (4) is >10m.