Construction method for reducing side friction resistance of cast-in-place pile by adopting transition layer
By setting a transition layer and isolation material on the surface of the cast-in-place pile, the problem of increased negative friction was solved, thereby improving the stability and bearing capacity of the pile foundation, simplifying the construction process and reducing costs.
Patent Information
- Application Number
- CN202511095680.4
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-08-06
- Publication Date
- 2025-10-28
AI Technical Summary
In soft soil or deep fill strata, the downward displacement of the soil around the pile is greater than that of the pile itself, resulting in an increase in negative friction, which affects the bearing capacity and settlement of the pile foundation. Existing technologies are difficult to effectively eliminate negative friction, and commonly used methods are complex or increase costs.
A transition layer is set on the surface of the cast-in-place pile. Through a double-sleeve structure and flexible isolation material, an isolation layer is formed to reduce frictional resistance. Combined with the pile cap protection device, the pile is effectively isolated from the soil.
It effectively reduces negative friction, decreases settlement, improves the bearing capacity and stability of pile foundations, simplifies construction processes, and reduces costs.
Smart Images
Figure CN120844596A_ABST
Abstract
Description
Technical Field
[0001] This invention belongs to the field of pile foundation construction technology, specifically relating to a construction method that uses a transition layer to reduce the side friction of cast-in-place piles. Background Technology
[0002] Pile foundations are widely used in modern civil engineering due to their high vertical stiffness and bearing capacity, low settlement, and ability to withstand certain horizontal loads. However, when constructing pile foundations in soft soil or special soil strata (such as deep fill strata), the downward displacement of the surrounding soil often exceeds the downward displacement of the pile itself due to factors such as soil consolidation under its own weight, subsidence, lowering of the groundwater level, or surface overloading. This results in downward friction on the pile, creating a downward tension load on the pile sides—the so-called negative friction. The presence of negative friction increases the load on the pile, reduces the bearing capacity of the compression pile, and may lead to excessive settlement, causing building tilting and cracking, directly affecting the functionality and safety of the engineering structure. Therefore, reducing negative friction on the pile has become a key concern in the engineering field.
[0003] Currently, commonly used methods for eliminating negative skin friction are mainly divided into two categories: one is to control the source of negative skin friction, that is, to eliminate the harmfulness of the soil itself that is prone to generating negative friction through foundation treatment methods (dynamic compaction, preloading consolidation, etc.). This method has a long construction cycle and is generally not effective for deep soil layers. The other is to isolate the pile body from the surrounding soil. This type of method is more commonly used, including coating the pile surface with an asphalt film, installing unloading sleeves, installing protective sleeves, and driving isolation piles. This type of method has a more complex processing technology, which increases the manufacturing cost of the pile. While reducing negative friction, it also reduces positive friction.
[0004] In summary, the elimination of negative skin friction in deep soft soil layers and backfilled areas still requires further research. Although many scholars have conducted extensive research and achieved some results, the methods for eliminating negative skin friction are still incomplete. Based on this, this invention proposes a construction method that uses a transition layer to reduce the side skin friction of cast-in-place piles. Summary of the Invention
[0005] To address the aforementioned technical problems in existing technologies, this invention proposes a construction method that uses a transition layer to reduce the side friction resistance of cast-in-place piles, overcoming the shortcomings of existing technologies. By setting a transition layer on the surface of the cast-in-place pile, the impact of settlement during and after construction on the pile foundation in soft soil or filled soil areas can be eliminated.
[0006] In order to achieve the above object, the present invention adopts the following technical solutions: A construction method for reducing the side friction of cast-in-place piles using a transition layer is characterized by comprising a cast-in-place pile, a transition layer, and a pile cap. The transition layer is located on the outside of the cast-in-place pile and is arranged coaxially with the pile. The pile cap is located at the upper end of the cast-in-place pile and is bonded to it. The specific construction method is as follows: Step 1: Drilling of cast-in-place piles According to the design requirements, a hole-forming drilling rig was used to drill holes at the designed pile locations to ensure the stability of the hole walls; Step 2: Lowering the steel cage The reinforcing cage is fixed with protective layer pads at certain intervals, and the reinforcing cage is lowered to the set depth according to the design requirements. Step 3: Forming holes in the transition layer A double-casing drilling rig is used to squeeze the concentric double-casing structure into the hole. During the lowering of the double casing, the lower ends of the inner and outer casings are kept closed. The steel cage is located in the hole in the middle of the inner casing. The inner wall of the inner casing is in contact with the protective layer pad until the inner and outer casings are lowered to the set depth. Step 4: Pouring concrete Separate the main body of the double casing drilling rig from the double casing structure, keep the steel cage and double casing structure inside the hole, and pour concrete into the hole in the middle of the inner casing according to the design requirements until the set height is reached. Step 5: Pull out the double-sleeve structure After the concrete in the hole has initially set and has a certain self-stabilizing ability, the double casing drilling rig is connected to the double casing. Flexible isolation material is poured between the inner casing and the outer casing while the double casing structure is vibrated and lifted. At the same time, the lower end between the inner and outer casings is in an open state until the flexible isolation material is poured to the set height according to the design requirements. Step Six: Install Pile Caps The double-casing drilling rig and the double casing were moved as a whole, and the pile cap was concentrically placed into the annular transition layer as a pile head protection device. After the concrete strength reached the design strength, the pile foundation construction was completed.
[0007] Preferably, the double-casing structure consists of two casings of different sizes arranged coaxially, with a cavity between the two casings. The length of the inner casing is greater than or equal to the length of the outer casing, and the diameter of the outer casing is 1.0-1.1 times the diameter of the bored pile hole. The inner wall of the inner casing and the outer wall of the outer casing are coated with a drag-reducing layer.
[0008] Preferably, the flexible isolation material is characterized by high viscosity, high structural strength, strong stability in underground environments, gel-like structure, ability to support its own weight and suspended particles, resistance to sedimentation or segregation, strong adsorption of water molecules, and resistance to dehydration even under pressure, such as bentonite materials.
[0009] Preferably, the pile cap is made of steel and the surface of the pile cap is coated with an anti-corrosion layer. The pile cap is composed of a circular ring plate and two sleeves of different sizes. The circular ring plate and the sleeves of different sizes are connected by welding. The inner diameter of the circular ring plate is the same as that of the inner sleeve and the small sleeve. The diameter of the large sleeve is the same as that of the outer sleeve. The outer diameter of the circular ring plate is 1.2-1.5 times that of the large sleeve.
[0010] The beneficial technical effects of this invention are as follows: By setting a transition layer on the surface of the cast-in-place pile, the problem of settlement during and after construction in soft soil or filled soil areas can be eliminated. Attached Figure Description
[0011] Figure 1 This is a schematic cross-sectional view of the overall structure in a construction method for reducing the side friction of cast-in-place piles using a transition layer, as described in this invention. Figure 2 This is a three-view drawing of the pile cap in a construction method for reducing the side friction of cast-in-place piles using a transition layer, as described in this invention.
[0012] Among them, 1-reinforcing cage, 2-cast pile, 3-transition layer, 4-pile cap. Detailed Implementation
[0013] The present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments: Example 1:
[0014] like Figure 1-2 As shown, a construction method for reducing the side friction of cast-in-place piles using a transition layer includes a cast-in-place pile 2, a transition layer 3, and a pile cap 4. The transition layer 3 is located on the outside of the cast-in-place pile 2 and is arranged coaxially with the cast-in-place pile 2. The pile cap 4 is located at the upper end of the cast-in-place pile 2 and is bonded to the cast-in-place pile 2. The specific construction method is as follows: Step 1: Drilling of the second bored pile According to the design requirements, a hole-forming drilling rig was used to drill holes at the designed pile locations to ensure the stability of the hole walls; Step 2: Lowering the steel cage 1 The reinforcing cage 1 is fixed with protective layer pads at certain intervals, and the reinforcing cage 1 is lowered to the set depth according to the design requirements; Step 3: Forming holes in transition layer 3 A double-casing drilling rig is used to squeeze the concentric double-casing structure into the hole. During the lowering of the double casing, the lower ends of the inner and outer casings are kept closed. The steel cage 1 is located in the hole in the middle of the inner casing. The inner wall of the inner casing is in contact with the protective layer pad until the inner and outer casings are lowered to the set depth. Step 4: Pouring concrete Separate the main body of the double casing drilling rig from the double casing structure. Keep the steel cage 1 and the double casing structure inside the hole. Pour concrete into the hole in the middle of the inner casing according to the design requirements until the set height is reached. Step 5: Pull out the double-sleeve structure After the concrete in the hole has initially set and has a certain self-stabilizing ability, the double casing drilling rig is connected to the double casing. Flexible isolation material is poured between the inner casing and the outer casing while the double casing structure is vibrated and lifted. At the same time, the lower end between the inner and outer casings is in an open state until the flexible isolation material is poured to the set height according to the design requirements. Step Six: Install Pile Caps 4 The double-casing drilling rig and the double casing were moved as a whole, and the pile cap 4 was concentrically placed into the annular transition layer 3 as a pile head protection device. After the concrete strength reached the design strength, the pile foundation construction was completed.
[0015] Preferably, the double-casing structure consists of two casings of different sizes arranged coaxially, with a cavity between the two casings. The length of the inner casing is greater than or equal to the length of the outer casing, and the diameter of the outer casing is 1.0-1.1 times the diameter of the bored pile. The inner wall of the inner casing and the outer wall of the outer casing are coated with a drag-reducing layer.
[0016] Preferably, the flexible isolation material is characterized by high viscosity, high structural strength, strong stability in underground environments, gel-like structure, ability to support its own weight and suspended particles, resistance to sedimentation or segregation, strong adsorption of water molecules, and resistance to dehydration even under pressure, such as bentonite materials.
[0017] Preferably, the pile cap 4 is made of steel, and the surface of the pile cap 4 is coated with an anti-corrosion layer. The pile cap 4 is composed of a circular ring plate and two sleeves of different sizes. The circular ring plate and the sleeves of different sizes are connected by welding. The inner diameter of the circular ring plate is the same as that of the inner sleeve and the small sleeve. The diameter of the large sleeve is the same as that of the outer sleeve. The outer diameter of the circular ring plate is 1.2-1.5 times that of the large sleeve. Example 2:
[0018] like Figure 1-2 As shown, a construction method using a transition layer to reduce the side skin friction of cast-in-place piles is described. The stratum consists of two layers: an upper backfill layer and a lower consolidated cohesive soil layer. To reduce the negative skin friction of the backfill layer on the cast-in-place pile 2, a transition layer 3 is installed within the depth of the backfill layer. The transition layer 3 is located on the outside of the cast-in-place pile 2 and is coaxially arranged with it. A pile cap 4 is installed at the upper end of the cast-in-place pile 2 and bonded to it. The specific construction method is as follows: Step 1: Drilling of the second bored pile According to the design requirements, a drilling rig is used to drill holes at the designed pile locations to ensure the stability of the hole wall; for cast-in-place pile 2, rotary drilling equipment, positive circulation equipment, etc. can be used for hole formation.
[0019] Step 2: Lowering the steel cage 1 The reinforcing cage 1 is fixed with protective layer pads at certain intervals. In order to ensure that a protective layer is reserved between the reinforcing cage 1 and the inner casing, the reinforcing cage 1 is lowered to the set depth according to the design requirements. Step 3: Forming holes in transition layer 3 A double-casing drilling rig is used to squeeze the concentric double-casing structure into the hole. The double-casing structure can be regarded as a whole structure. It is directly lowered to the designated depth by the double-casing drilling rig. During the lowering of the double-casing, the lower ends of the inner and outer casings are kept closed, that is, there is nothing in the cavity between the inner and outer casings. The steel cage 1 is in the hole in the middle of the inner casing. The inner wall of the inner casing is in contact with the protective layer pad block until the inner and outer casings are lowered to the designated depth. Step 4: Pouring concrete Separate the main body of the double casing drilling rig from the double casing structure. Keep the steel cage 1 and the double casing structure inside the hole. Pour concrete into the hole in the middle of the inner casing according to the design requirements until the set height is reached. Step 5: Pull out the double-sleeve structure After the concrete in the hole has initially set and has a certain self-stabilizing ability, the double-casing structure is pulled out. Since the inner wall of the inner casing and the outer wall of the outer casing are equipped with drag-reducing layers, the pull-out is relatively easy. During the vibration pull-out process, the concrete pile body will not collapse. The double-casing drilling rig is connected to the double casing. Flexible isolation material is poured into the space between the inner casing and the outer casing while the double-casing structure is vibrated and lifted. At the same time, the lower end between the inner and outer casings is in an open state, and the flexible isolation material is lowered from the space between the inner and outer casings. As the double-casing structure is pulled out, the flexible isolation material fills the cavity after the pull-out until the flexible isolation material is poured to the set height as required by the design. Step Six: Install Pile Caps 4 The double-casing drilling rig and the double casing are moved as a whole, and the pile cap 4 is concentrically placed into the annular transition layer 3 as a pile head protection device. After the concrete strength reaches the design strength, the pile foundation construction is completed. In order to protect the stability of the cast-in-place pile 2, after the cast-in-place pile 2 has initially set, the small casing of the pile cap 4 is directly sleeved onto the already formed cast-in-place pile 2, and the large casing is inserted into the outside of the transition layer 3. In this way, the inner side of the small casing in the pile cap 4 is bonded to the cast-in-place pile 2, and the outer side of the large casing is in frictional contact with the soil.
[0020] Preferably, the double-casing structure consists of two casings of different sizes arranged coaxially, with a cavity between the two casings. The length of the inner casing is greater than or equal to the length of the outer casing, and the diameter of the outer casing is 1.0-1.1 times the diameter of the bored pile. The inner wall of the inner casing and the outer wall of the outer casing are coated with a drag-reducing layer.
[0021] Preferably, the flexible isolation material is characterized by high viscosity, high structural strength, strong stability in underground environments, gel-like structure, ability to support its own weight and suspended particles, resistance to sedimentation or segregation, strong adsorption of water molecules, and resistance to dehydration even under pressure, such as bentonite materials.
[0022] Preferably, the pile cap 4 is made of steel, and the surface of the pile cap 4 is coated with an anti-corrosion layer. The pile cap 4 is composed of a circular ring plate and two sleeves of different sizes. The circular ring plate and the sleeves of different sizes are connected by welding. The inner diameter of the circular ring plate is the same as that of the inner sleeve and the small sleeve. The diameter of the large sleeve is the same as that of the outer sleeve. The outer diameter of the circular ring plate is 1.2-1.5 times that of the large sleeve.
[0023] In the description of the embodiments of this invention, it should be understood that the terms "upper," "lower," etc., indicating the orientation or positional relationship are based on the orientation or positional relationship shown in the accompanying drawings, and are only for the convenience of describing the invention 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, and therefore should not be construed as a limitation of the invention. In the description of this invention, it should be noted that unless otherwise explicitly specified and limited, the terms "set" and "connected" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a direct connection or an indirect connection through an intermediate medium; they can refer to the internal communication of two elements. Those skilled in the art can understand the specific meaning of the above terms in this invention through specific circumstances.
[0024] Of course, the above description is not intended to limit the present invention, and the present invention is not limited to the examples given above. Any changes, modifications, additions or substitutions made by those skilled in the art within the scope of the present invention are also within the protection scope of the present invention.
Claims
1. A construction method for reducing the side friction of cast-in-place piles by using a transition layer, characterized in that: It includes cast-in-place piles, a transition layer, and pile caps. The transition layer is located outside the cast-in-place piles and is arranged coaxially with them. The pile caps are located at the top of the cast-in-place piles and are bonded to them. The specific construction method is as follows: Step 1: Drilling of cast-in-place piles According to the design requirements, a hole-forming drilling rig was used to drill holes at the designed pile locations to ensure the stability of the hole walls; Step 2: Lowering the steel cage The reinforcing cage is fixed with protective layer pads at certain intervals, and the reinforcing cage is lowered to the set depth according to the design requirements. Step 3: Forming holes in the transition layer A double-casing drilling rig is used to squeeze the concentric double-casing structure into the hole. During the lowering of the double casing, the lower ends of the inner and outer casings are kept closed. The steel cage is located in the hole in the middle of the inner casing. The inner wall of the inner casing is in contact with the protective layer pad until the inner and outer casings are lowered to the set depth. Step 4: Pouring concrete Separate the main body of the double casing drilling rig from the double casing structure, keep the steel cage and double casing structure inside the hole, and pour concrete into the hole in the middle of the inner casing according to the design requirements until the set height is reached. Step 5: Pull out the double-sleeve structure After the concrete in the hole has initially set and has a certain self-stabilizing ability, the double casing drilling rig is connected to the double casing. Flexible isolation material is poured between the inner casing and the outer casing while the double casing structure is vibrated and lifted. At the same time, the lower end between the inner and outer casings is in an open state until the flexible isolation material is poured to the set height according to the design requirements. Step Six: Install Pile Caps The double-casing drilling rig and the double casing were moved as a whole, and the pile cap was concentrically placed into the annular transition layer as a pile head protection device. After the concrete strength reached the design strength, the pile foundation construction was completed.
2. The construction method for reducing the side friction of cast-in-place piles using a transition layer according to claim 1, characterized in that: The double-casing structure consists of two casings of different sizes arranged coaxially with a cavity between them. The length of the inner casing is greater than or equal to the length of the outer casing, and the diameter of the outer casing is 1.0-1.1 times the diameter of the bored pile hole. The inner wall of the inner casing and the outer wall of the outer casing are coated with a drag-reducing layer.
3. The construction method for reducing the side friction of cast-in-place piles using a transition layer according to claim 1, characterized in that: Flexible isolation materials are characterized by high viscosity, high structural strength, strong stability in underground environments, gel-like structure, ability to support their own weight and suspended particles, resistance to sedimentation or segregation, and ability to firmly adsorb water molecules, making them resistant to dehydration even under pressure, such as bentonite materials.
4. The construction method for reducing the side friction of cast-in-place piles using a transition layer according to claim 1, characterized in that: The pile cap is made of steel and coated with an anti-corrosion layer. The pile cap consists of a circular plate and two sleeves of different sizes. The circular plate and the sleeves are connected by welding. The inner diameter of the circular plate is the same as that of the inner sleeve and the small sleeve. The diameter of the large sleeve is the same as that of the outer sleeve. The outer diameter of the circular plate is 1.2-1.5 times that of the large sleeve.