Technical device for reducing negative frictional resistance on driven cast-in-place pile, and application method thereof

Abstract

The invention relates to a technical device for reducing negative frictional resistance on a driven cast-in-place pile, and an application method thereof. The device is characterized in that a dual-layer steel sleeve is arranged outside of a pile mould, the inner sleeve and the outer sleeve are connected by using a holder and are fixed below a vibratory hammer, and a cylindrical dual-layer plastic thin film is arranged between the inner sleeve and the outer sleeve and is fixed on an annular prefabricated concrete block by using a buckle arranged on ends of the thin film, wherein the annular prefabricated concrete block is arranged on the lower portion of the dual-layer steel sleeve. According to the invention, the dual-layer steel sleeve along with the plastic thin film within the dual-layer steel sleeve and the annular prefabricated block is sunk to a predesigned depth in static pressure or vibration manner, the steel sleeve is pulled out of the ground after concrete poured by the driven cast-in-place pile has a certain strength, while the dual-layer plastic thin film and the annular prefabricated block are left in the foundation, so that frictional factor of a pile-soil interface above the neutral point of the pile body is reduced, damages caused by the negative frictional resistance on the pile foundation are eliminated, bearing capacity of the pile foundation is improved, at the same time forming quality on the upper portion of the pile body is controlled. The device has a convenient implementation, low cost, and good pile-forming assistance effect.

Description

technical field [0001] The invention belongs to the technical field of soft soil foundation treatment and pile foundation, and in particular relates to a technical device for reducing the negative friction resistance of an immersed tube grouting pile and an application method thereof. Background technique [0002] Pile foundation treatment In the weak soil foundation, when the settlement of the soil is greater than that of the pile due to factors such as ground load, groundwater level drop, and collapsible loess in contact with water, the pile side soil will produce downward negative frictional resistance on the pile body. The generation of negative frictional resistance not only fails to contribute to bearing the upper load, but also produces a pull-down load acting on the pile body and in the same direction as the load, which may cause yield or damage of the foundation at the pile end, damage of the pile body, and unevenness of the upper structure A series of problems such...

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Problems solved by technology

[0003] At present, the commonly used method to reduce the negative friction resistance of foundation piles is the pile body asphalt coating method, that is, a layer of 5-10 mm thick asphalt is applied to the range above the neutral point of the prefabricated pile body, but this method can only be used for prefabricated piles. piles, which are not suitable for immersed tube piles widely used in soft soil foundation treatment projects such as highways and high-speed railways, and asphalt coatings have certain pollution to the groundwater environment

Before the present invention, "A Device for Eliminating Negative Frictional Resistance of Pile Foundations" (Patent No.: ZL 201020517004.4) and "A Device for Preventing Negative Frictional Resistance" (Patent No.: ZL 200920156095.0) published The method of setting unloading devices such as casing pipes between the soil bodies eliminates the negative frictional resistance loaded on the pile body through the unloading device. Although this method can reduce the negative frictional resistance to a certain extent, the construction cost and engineering cost Relatively high; "Plastic casing with smooth surface and threaded part for cast-in-place concrete piles" (Patent No.: ZL 200720035479.8) discloses a semi-smooth and half-thread plastic casing method for cast-in-place concrete piles , the plastic casing is difficult to process, and pouring concrete directly into the plastic casing without protection will easily cause damage to the casing

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