Blasting pile-forming method for three-stage bottom-enlarging prefabricated and cast-in-situ steel concrete combination pile body

Abstract

The invention relates to a blast method to construct the pile which has a composite three-section pedestal pile body and a cast-in-situ reinforced concrete pile body. The invention comprises the technique procedures that: a. an immersed tube with a metal pile crown is sunk to the hardpan until the design elevation is reached; b. the metal pile crown is taken out; c. the lower pedestal space is processed and the soil is cleaned, the lower pedestal is cast with concrete and a prefabricated hollow pile body which has a steel dowel at the lower end is placed into the immersed tube, then the immersed tube is pulled to the designed distance H1; d. the middle pedestal space is processed and then the immersed tube is pulled to the designed distance H2, then the upper pedestal space is enlarged with an extrusion equipment, then the fabricated solid pile body is placed and the soil is cleaned, then a long steel bar is lowered from the immersed tube to pass through the upper and the lower section and slightly pass through the middle pedestal; e. the middle and the upper pedestals are cast with concrete and the middle and upper section with reinforced concrete is cast to form the pile body; f. the immersed tube is taken out to form the pile. The invention can distinctly improve the utilization ratio of the material strength and the reduction coefficient can reach 0.9-1.0; the diameter ratio of the pedestal diameter to the pile body can reach 3.5-5.0, which considerably improves the carrying capacity of the individual pile.

Description

technical field [0001] The invention relates to a construction method of building pile foundation engineering, in particular to a blasting pile forming method of three-stage bottom-expanding 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...

AI Technical Summary

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

Images