Extrusion pile-forming method of belled prefabricated pile body

Abstract

The invention relates to a construction method for building pile foundation engineering, in particular to an extraction pile forming method of an enlarged-base precast pile body, which is the preferred construction method of a multi-stage base large-bearing-capacity pile. The pile forming method of the invention comprises the following process steps: an immersed tube with a metal pile head is sunk to a hard soil layer for designing elevation; the metal pile head is drawn out; the base is enlarged to form a lower base space and all fine earth is thoroughly taken out to ensure that fine earth is cleaned; a lower base is cast; a lower precast pile body and dowels are put into and anchored with the lower base; the immersed tube is pulled upward to a preset height H; the base is enlarged to form an upper base space and all fine earth is thoroughly taken out; steel bars are put into from the opening of the immersed tube and extended into the upper part of a lower recast hollow pile body, and flowing concrete is used for casting the upper base and casting the upper pile body of the reinforced concrete in place; and the immersed tube is pulled out, and concrete slurry is injected into the gap. The construction method has the advantages that: the bearing capacity and the reduction factor of a single pile are enhanced, the utilization rate of the material strength is improved, and the construction method is safe and stable, the construction cost of the pile base is reduced, therefore, the designed expected effect is reached.

Description

technical field [0001] The invention relates to a construction method of a building pile foundation project, in particular to a method for forming a pile by extrusion of a prefabricated pile body with an enlarged bottom. It is the preferred construction method for large load-bearing piles with multi-level foundations. Background technique [0002] According to the national standard, the whole body is cast-in-place (that is, the pile body is cast-in-place concrete, and the base is also cast-in-place concrete). The maximum diameter ratio of the base of the expanded bottom pile is limited to 3-3.5, while the immersed tube prefabricated steel concrete expanded bottom pile, this kind of pile It is prefabricated concrete for the pile body and cast-in-place concrete for the base. Obviously, the ratio of 3-3.5 is broken, and generally can reach 3.5-5. Although the bearing capacity is greater, it still cannot meet the needs of the project, especially when the diameter of the expanded...

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Problems solved by technology

These two points are quite unfavorable to multi-bearing plate (multi-level bottom expansion) piles. In other words, it brings two problems. 1) The national building code stipulates that the end bearing of the base of the pile expansion bottom using the positive and negative circulation method The force has to be multiplied by a factor of 0.45, because there is mud and the sediment at the bottom of the pile cannot be cleaned up. (The standard in Zhejiang Province is 0.24 discount). However, the construction conditions cannot be protected. In addition, the positive and negative circulation method works underwater, so the bottom expansion construction cannot be seen, and it is difficult to measure and record. It also often happens that a piece of upper soil falls off when the bottom is expanded underwater. Occurrence, also because the multi-stage piles of the prior art all use cast-in-place concrete for the whole body, and the strength of cast-in-place concrete is not high, and the quality is difficult to guarantee, and the quality is difficult to control when pouring concrete in water, plus multiple bases The bearing capacity of the piles is relatively large, the diameter of the pile body must be made larger due to the above factors, and this kind of multiple bases is most afraid of a large diameter of the pile body. Research and tests have shown that as the diameter of the pile body increases, its bearing capacity will be greatly attenuated.

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