Device and method for reducing negative friction resistance of prefabricated pipe pile

Abstract

The invention discloses a device and a method for reducing the negative friction resistance of a prefabricated pipe pile. The concrete outer surfaces of a neutral-point pipe pile section and pipe pilesections above the neutral-point pipe pile section are wrapped by composite geomembrane layers capable of sliding relative to each other, the composite geomembrane layers can be basically degraded when the settlement amount of a soil body is smaller than that of a pile foundation, a pile hole expanding structure is welded on a steel end plate at the lower end of the neutral-point pipe pile section, and a fixing structure is arranged at the position, close to the steel end plate of the pipe pile, of the lower ends of the composite geomembrane layers. According to the device, the composite geomembrane layers capable of sliding relative to each other are used for wrapping the neutral-point pipe pile section and the concrete outer surfaces of the pipe pile sections above the neutral-point pipe pile section, so that the neutral-point pipe pile section is reduced, the friction coefficient of a pile-soil interface is reduced, and the negative friction resistance of the pipe pile is reduced;and when the settlement amount of the soil body is smaller than that of the pile foundation, the composite geomembrane layers can be basically degraded, and the upward positive friction resistance isgenerated along the full length of the pile body. The method is simple and easy to implement and convenient to construct, and can effectively reduce the damage caused by the negative friction resistance of the prefabricated pipe pile.

Description

technical field [0001] The invention belongs to the technical field of foundation treatment and pile foundation, and in particular relates to a device and method for reducing negative frictional resistance of prefabricated pipe piles. Background technique [0002] When the pile foundation deals with soft soil foundation, when the pile foundation passes through the highly compressive soil layer, under the action of self-weight consolidation, surface overload or groundwater extraction, the settlement of the soil around the pile exceeds the settlement of the foundation pile, and it will be on the side of the pile. The part above the neutral point of the surface produces downward negative frictional resistance, and the negative frictional resistance on the side of the pile cannot contribute to bearing the upper load, but instead produces a pull-down force on the pile side. For friction piles, negative frictional resistance will cause additional settlement of piles. For buildings...

AI Technical Summary

Problems solved by technology

For friction piles, negative frictional resistance will cause additional settlement of piles. For buildings, large settlements and uneven settlements will occur in buildings, resulting in damage to the superstructure; for end-bearing piles, negative frictional resistance will cause piles to sink. The load increases, resulting in the destruction of the strength of the pile body or the failure of the bearing layer at the pile end

[0003] At present, there are many ways to reduce the negative friction of pile foundations. For example, before constructing pile foundations, preload the foundation to accelerate the consolidation of the foundation soil and reduce the compressibility of the soil. This method is difficult to construct and requires a lot of financial resources. Material resources, long construction period; on the outside of the pile body above the neutral point, a casing with a diameter slightly larger than the pile diameter is covered to isolate the pile body from the surrounding soil. This method requires the use of a large amount of steel, and the construction process It is more complicated; apply a thin layer of asphalt paint on the part above the neutral point of the pile body. This method is widely used. Although the effect is good, there are still some problems, such as: high performance requirements for asphalt, requiring uniform application and thickness requirements Control it at the millimeter level, and asphalt coating will also cause soil pollution; before piling, drill a hole with a diameter slightly larger than the pile diameter, and the depth reaches the neutral point, and use driving or other conventional methods below the neutral point Construction to ensure the positive frictional resistance of the pile, and above the neutral point, fill with bentonite mud to reduce negative frictional resistance. During construction, it is necessary to replace the drill bit, or carry out two sets of drilling and static pressure (or vibration) pile sinking at the same time The process requires more equipment and the process is complicated

[0004] Chinese patent CN 102628269 A discloses "A Technical Device and Application Method for Reducing Negative Friction Resistance of Immersed Tube Cast-in-situ Pile", by driving a cylindrical double-layer plastic film into the outer side of the immersed tube-filled cast-in-situ pile and within the depth range above the neutral point , so as to reduce the friction coefficient of the pile-soil interface above the neutral point of the pile body, and effectively eliminate the unfavorable factors caused by the negative friction resistance of the pile foundation. and pull out, the construction process is complicated and the construction period is long; Chinese patent CN 202500134U announced "a prefabricated pile body that can reduce negative friction resistance", and by pasting a film on the surface above the neutral point of the pile body, the pile body and the soil mass are increased. The smoothness of the contact surface reduces the friction between the pile and the soil. Although this kind of prefabricated pile is simple and easy to implement, when the prefabricated pile with a film enters the soil, the film may be destroyed and the prefabricated pile may be peeled off. body risk; Chinese patent CN 105649075 A discloses a "device and method for reducing the negative frictional resistance of bored piles". Reduce the friction coefficient of the pile-soil interface above the neutral point of the foundation pile, and reduce the adverse effects of the negative friction resistance of the pile foundation. By radially pushing the hanging cloth to the double-layer cloth bag grouting, so that the bottom end is close to the hole wall, it can Effectively prevent concrete from entering around the hanging cloth during subsequent grouting, so that the double-layer hanging cloth can be attached to the hole wall from bottom to top, forming a sliding sleeve with low friction coefficient, and graphite is used as the slippery layer between the double-layer hanging cloth agent, the double-layer cloth bag set by this method will eventually stay in the pile body, destroying the integrity of the pile, and the outer surface of the hanging cloth is coated with asphalt, which has higher requirements on the performance of the asphalt, which requires uniform application and thickness control at the millimeter level. Bituminous coatings also cause soil pollution

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