A cast-in-place pile type with a transition layer for reducing side friction

Abstract

The utility model discloses a kind of to be used to realize the reduction of side friction of transition layer cast-in-place pile type, belong to pile foundation construction technical field, including cast-in-place pile, transition layer, pile cap, transition layer is set in cast-in-place pile outside, with coaxial arrangement, pile cap is set in cast-in-place pile upper end, and bonding between cast-in-place pile, pile cap is composed of circular ring type board and two sleeves of size, welding connection is used between circular ring type board and size sleeve, the inner diameter of circular ring type board is same with small sleeve diameter, and the diameter of large sleeve is same with outer sleeve. Through the transition layer of being set in cast-in-place pile surface and then reach the problem of eliminating the influence of soft soil area or fill area construction process and post-construction settlement to pile foundation.

Description

Technical Field

[0001] This utility model belongs to the field of pile foundation construction technology, specifically relating to a cast-in-place pile type that uses a transition layer to reduce side friction. 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 technology for eliminating 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 cast-in-place pile type that uses a transition layer to reduce side skin friction. Summary of the Invention

[0005] To address the aforementioned technical problems in existing technologies, this utility model proposes a cast-in-place pile type that uses a transition layer to reduce side friction, 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 is eliminated.

[0006] To achieve the above objectives, the present invention adopts the following technical solution:

[0007] A type of cast-in-place pile that uses a transition layer to reduce side friction 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 cast-in-place pile. The pile cap is located at the upper end of the cast-in-place pile and is bonded to the cast-in-place pile. The pile cap is composed of a circular ring plate and two sleeves of different sizes. The circular ring plate and the large and small sleeves are connected by welding. The inner diameter of the circular ring plate is the same as the diameter of the small sleeve, and the diameter of the large sleeve is the same as the outer sleeve.

[0008] Preferably, the pile cap is made of steel, and the surface of the pile cap is coated with an anti-corrosion layer. The outer diameter of the annular plate is 1.2-1.5 times that of the large sleeve.

[0009] 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.

[0010] The beneficial technical effects of this utility model are as follows:

[0011] 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

[0012] Figure 1 This is a schematic cross-sectional view of the overall structure of a cast-in-place pile type that uses a transition layer to reduce side friction resistance, according to this utility model.

[0013] Figure 2 This is a three-view drawing of the pile cap in a cast-in-place pile type that uses a transition layer to reduce side friction.

[0014] Among them, 1 - cast-in-place pile, 2 - transition layer, and 3 - pile cap. Detailed Implementation

[0015] The present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments: Example 1:

[0016] like Figure 1-2 As shown, a type of cast-in-place pile that uses a transition layer to reduce side friction includes a cast-in-place pile 1, a transition layer 2, and a pile cap 3. The transition layer 2 is located on the outside of the cast-in-place pile 1 and is arranged coaxially with the cast-in-place pile 1. The pile cap 3 is located on the upper end of the cast-in-place pile 1 and is bonded to the cast-in-place pile 1. The pile cap 3 is composed of a circular annular plate and two sleeves of different sizes. The circular annular plate and the large and small sleeves are connected by welding. The inner diameter of the circular annular plate is the same as the diameter of the small sleeve, and the diameter of the large sleeve is the same as the outer sleeve.

[0017] Preferably, the pile cap 3 is made of steel, and the surface of the pile cap 3 is coated with an anti-corrosion layer. The outer diameter of the annular plate is 1.2-1.5 times that of the large sleeve.

[0018] 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. Example 2:

[0019] like Figure 1-2 As shown, a type of cast-in-place pile that uses a transition layer to reduce side friction is described. The stratum consists of two layers: an upper backfill layer and a lower consolidated cohesive soil. In this stratum, to reduce the negative skin friction of the backfill layer on the cast-in-place pile 1, a transition layer 2 is set within the depth of the backfill layer. The transition layer 2 is located outside the cast-in-place pile 1 and is arranged coaxially with the cast-in-place pile 1. The pile cap 3 is set at the upper end of the cast-in-place pile 1 and is bonded to the cast-in-place pile 1. The pile cap 3 consists of a circular annular plate and two sleeves of different sizes. The circular annular plate and the sleeves of different sizes are connected by welding. The inner diameter of the circular annular plate is the same as the diameter of the small sleeve, and the diameter of the large sleeve is the same as the outer sleeve.

[0020] Preferably, the pile cap 3 is made of steel, and the surface of the pile cap 3 is coated with an anti-corrosion layer. The outer diameter of the annular plate is 1.2-1.5 times that of the large sleeve.

[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] The specific construction method for this structure can be carried out using the following steps:

[0023] Step 1: Drilling of Pile 1

[0024] 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; the drilling of cast-in-place pile 1 can be carried out using rotary drilling equipment, positive circulation equipment, etc.

[0025] Step 2: Lowering the steel cage

[0026] 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.

[0027] Step 3: Forming holes in transition layer 2

[0028] 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 process, 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 reinforcing cage 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.

[0029] Step 4: Pouring concrete

[0030] 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.

[0031] Step 5: Pull out the double-sleeve structure

[0032] 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.

[0033] Step Six: Install Pile Caps 3

[0034] The double-casing drilling rig and the double casing are moved as a whole, and the pile cap 3 is concentrically placed into the annular transition layer 2 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 1, after the cast-in-place pile 1 has initially set, the small casing of the pile cap 3 is directly sleeved onto the already formed cast-in-place pile 1, and the large casing is inserted into the outside of the transition layer 2. In this way, the inner side of the small casing in the pile cap 3 is bonded to the cast-in-place pile 1, and the outer side of the large casing is in frictional contact with the soil.

[0035] In the description of the embodiments of this utility model, 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 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, and therefore should not be construed as a limitation of this utility model. In the description of this utility model, it should be noted that unless otherwise explicitly specified and limited, the terms "set" and "connected" should be interpreted broadly. For example, it can refer to a fixed connection, a detachable connection, or an integral connection; it can refer to a direct connection or an indirect connection through an intermediate medium; it 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 utility model through specific circumstances.

[0036] Of course, the above description is not intended to limit the present utility model, and the present utility model 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 utility model are also within the protection scope of the present utility model.

Claims

1. A type of cast-in-place pile that uses a transition layer to reduce side friction, characterized in that: It includes cast-in-place piles, transition layers, and pile caps. The transition layer is located outside the cast-in-place piles and is arranged coaxially with them. The pile cap is located at the top of the cast-in-place piles and is bonded to them. The pile cap consists 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 the diameter of the small sleeve, and the diameter of the large sleeve is the same as the outer sleeve.

2. The cast-in-place pile type according to claim 1, which uses a transition layer to reduce side friction, is characterized in that: The pile cap is made of steel and coated with an anti-corrosion layer. The outer diameter of the circular plate is 1.2-1.5 times that of the large sleeve.

3. The cast-in-place pile type according to claim 1, which uses a transition layer to reduce side friction, is characterized in that: Flexible insulating materials are gel-like and can support their own weight and suspended particles. They can also firmly adsorb water molecules. Bentonite is one type of flexible insulating material.

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