Construction method for bored pile of subway station enclosure structure of upper-soft lower-hard ground

Abstract

The invention discloses a construction method for a bored pile of a subway station enclosure structure of upper-soft lower-hard ground. The method includes the steps that firstly, measurement and paying-off are conducted, wherein measurement and paying-off are carried out at a pile position of the bored pile to be constructed, and the bored pile to be constructed is a cast-in-place pile constructed and formed in the upper-soft lower-hard ground; secondly, a steel casing is buried, wherein the steel casing is buried in the soft ground where the bored pile to be constructed is located; thirdly, drilling construction of pile holes is conducted; fourthly, a steel rib frame is laid down; fifthly, concrete pouring construction is conducted; sixthly, the steel casing is detached; seventhly, the bored pile is formed. Drilling construction of the pile holes includes the steps that 301, drilling construction is conducted on an upper pipe hole section and 302, drilling construction is conducted on a lower pile hole section, wherein the lower pile hole section is subjected to drilling construction by being divided into multiple pile hole section bodies from top to bottom, and when any hole section body is subjected to drilling construction, drilling for cores and secondary overcoring are conducted. The method is simple, design is reasonable, construction is easy and convenient, drilling difficulty of the pile holes is low, the use effect is good, and the bored pile construction process of the upper-soft lower-hard ground can be easily, conveniently and quickly completed.

Description

technical field [0001] The invention belongs to the technical field of pile foundation construction, and in particular relates to a method for constructing bored piles for an enclosure structure of a subway station on upper soft and lower hard strata. Background technique [0002] When bored cast-in-situ piles (hereinafter referred to as bored piles) are used for the enclosure structure of subway stations, it is difficult to form holes in unfavorable strata such as silt, rock filling, and hard rock (slightly weathered granite) protrusions. Moreover, since bored piles are concealed projects during construction, quality control is difficult. Especially when the upper part is a soft soil stratum such as silt layer or sand layer and the lower part is a hard rock stratum (hereinafter referred to as upper soft and lower hard stratum) construction of bored piles, the difficulty of forming holes is very large. Conventional bored pile pile hole forming methods mainly include the fol...

AI Technical Summary

Problems solved by technology

Conventional bored pile pile hole forming methods mainly include the following types: hammer impact drilling, down-the-hole hammer impact drilling and cone rotary drilling drilling into holes. The above pile hole forming methods mainly exist in the following constructions: Defects in several aspects: first, a large amount of mechanical equipment is required, there are many on-site machinery and large power consumption: because the impact drill uses electricity as the power source, multiple devices work at the same time, the power consumption is huge, and the load of the nearby transformer is almost saturated. It cannot meet the needs of the site, and if the generator is rented, it will cost a lot; at the same time, due to the large vibration, it is easy to cause the hole to collapse under complex geological conditions, resulting in repeated backfilling and rushing, resulting in waste of materials; second, the construction time is long and the construction period is not easy to guarantee : The construction efficiency of impact drilling is low, unable to meet the requirements of the construction period, and the construction period is relatively tight; third, the hole formation is difficult, easy to collapse and shrink in diameter, especially the process of forming holes with bedrock protrusions takes a long time, the mechanical wear is large, and the work efficiency is low. And it is not easy to guarantee the quality of hole formation

[0003] When ordinary percussion drilling is used in the upper soft and lower hard strata, it takes about 20 days for a drilled pile with a depth of about 15m into the rock to form a pile. and other phenomena, so the quality of pore formation in soft soil formations such as silt formations cannot be guaranteed.

When the air down-the-hole hammer is used in conjunction with the impact drill for construction, the hard rock is first crushed by the down-the-hole hammer, and then the mud is circulated with the impact drill to remove the slag, and then the down-the-hole hammer is used for construction. Repeatedly, it takes 15 hours for a pile to become a pile. and it is easy to cause the collapsed hole during the construction process. After the collapsed hole, mix sand and clay to fill it up to 1m above the collapsed hole section, and re-drill after compacting, which is labor-intensive and wasteful.

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