Mixed pile forming method for high-bearing prefabricated and cast-in-situs steel concrete composite pile body

Abstract

The present is prefabricating and in-situ reinforcing concrete casting process for constructing high bearing capacity combined pile stem. The process includes the following steps: 1. immersing immersed tube with metal pile head into hardpan to design elevation; 2. taking out the metal pile head; 3. forming the lower base space, taking out soil, casting lower concrete base, immersing one prefabricated hollow pile stem with steel dowels in the lower end into the immersed tube, and drawing upwards the immersed tube to one first designed distance; 4. forming the middle base space, drawing upwards the immersed tube to one second designed distance, forming the upper base space and penetrating reinforcing bars through the upper and the middle base spaces; 5. pouring concrete to form the upper base, the lower base and the middle pile stem; 6. setting the prefabricated pile stem with steel dowels into the immersed tube; and 7. withdrawing the immersed tube.

Description

technical field [0001] The invention relates to a construction method of a building pile foundation project, in particular to a method for forming piles of a high-bearing-capacity prefabricated and cast-in-place steel-concrete combined pile body. It is the preferred construction method for high-rise building multi-level foundation large bearing capacity pile foundation engineering. 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 n...

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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. Based on the above factors, the diameter of the pile body must be made larger, and the pile with multiple bases is most afraid of having 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 attenuate greatly. sharp

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