Underground and overground continuous construction method for major-diameter high flat bed pile in sandy soil stratum

Abstract

An underground and overground continuous construction method for a major-diameter high flat bed pile in a sandy soil stratum comprises the following steps: (I) a hole is drilled and cleaned, steel reinforcement cages and a grouting guide pipe are placed, and underwater concrete is poured; (II) an upper earlier stage construction platform and the grouting guide pipe are removed, a pile casing is pulled upwards slowly, and pouring is suspended when the concrete pouring height is 30-50cm above the ground; (III) the pile casing is pulled out slowly, and a grouting funnel is removed; (IV) concrete 5m below an orifice is vibrated, remaining concrete and slurry around the drilled hole are cleaned up, and sand and sand bags are piled up at the bottom of a steel formwork in a filling mode; (V) overground concrete is poured and vibrated repeatedly through a vibrating spear, and pouring of the overground concrete is stopped when the surface of the overground concrete exceeds a certain height; (VI) secondary vibrating is conducted within 30 minutes before initial setting of the overground concrete; form stripping is conducted 24 hours later, and maintenance is conducted. According to the underground and overground continuous construction method for the major-diameter high flat bed pile in the sandy soil stratum, the construction steps are reasonable in design, construction is convenient, cost is low, the construction period is short, and construction quality is controllable; the high flat bed pile after construction has the advantages that the connection position continuity of a pile body is good, so that the pile body is free of leakage, and pile quality is high.

Description

technical field [0001] The invention relates to the technical field of building foundation engineering, in particular to an underground continuous construction method for large-diameter and high-capped piles in sandy soil stratum. Background technique [0002] At present, our country is in a period of rapid development of engineering construction. The use of advanced design and construction technology to achieve the construction goals of saving investment, shortening the construction period, and ensuring safety has always been pursued by the engineering community. Bored pile foundations are currently widely used at home and abroad. A form of deep foundation, generally low-capped piles, which can meet the needs of the project according to the normal construction technology, but for some foreign-related petrochemical engineering LNG projects, it is gradually required to use large-diameter high-capped piles, currently for high-capped piles There are mainly the following three c...

AI Technical Summary

Problems solved by technology

First of all, in the first construction method, there will be a weak structural surface at the pile connection site. Small strain detection usually shows a "broken pile" waveform here, which poses a safety hazard. When the pile body bears a large load, the stress distribution is uneven and easy Stress concentration occurs, which may lead to broken piles or structural damage in severe cases

Secondly, the second method is to pull up the casing below the ground and use it as a steel formwork for the pile body above the ground. It is feasible, but because the casing cannot be cleaned and painted with release paint, and it is difficult to control the verticality of the casing, There are problems such as rough surface of the pile body above the ground level, pockmarked surface, inclined pile body on the ground, and instability of the casing

Finally, the third method, since the casing needs to be pulled out inside the steel formwork, it is necessary to reserve enough space for the casing to be pulled up, and the diameter of the upper pile body will eventually be much larger than that of the lower pile body, but for petrochemical LNG For engineering projects, because the design has very strict requirements on the pile diameter, the diameter of the upper pile body can neither exceed the design diameter by 50mm nor be lower than the design pile diameter, which is generally not applicable

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