Karst area drilling cast-in-place pile structure and construction method

Abstract

The invention relates to a karst area drilling cast-in-place pile structure which is characterized in that a cast-in-place pile, a bag grouting body and a prestress anchor cable are included; an original karst portion is backfilled with a clay and rubble mixture; the top of the cast-in-place pile is provided with a pile top expansion pile body, and a karst position is provided with the bag grouting body; a squeezing reinforcement cage is arranged in the bag grouting body; prestress anchor cable holes are formed around the cast-in-place pile, and the top of the prestress anchor cable penetrates through the pile top expansion pile body. The karst area drilling cast-in-place pile structure has the advantages of being quick in construction speed, low in cost and the like. Besides, the bearing capacity of a single pile is enhanced by changing the action mechanism of the cast-in-place pile, and the aim of solidifying a foundation is achieved. The invention further discloses a construction method of the karst area drilling cast-in-place pile structure.

Description

technical field [0001] The invention relates to a structure and a construction method of a bored pile, in particular to a structure and a construction method of a bag squeezed and expanded bored pile in a karst area. It belongs to the field of foundation engineering and is suitable for foundation engineering in karst areas. Background technique [0002] my country has a vast territory, complex and diverse geological conditions, and karst areas are distributed in many areas. It is very difficult to carry out pile foundation construction in karst areas, with many accidents, slow progress, and high cost. Especially in the stratum where karst caves are encountered, problems such as slurry leakage, broken piles, and karst cave collapse are prone to occur. For this complex and special stratum, the commonly used pile foundation construction methods include the hole wall support construction method of excavated piles, the steel casing method of drilled cast-in-place piles, and the ...

AI Technical Summary

Problems solved by technology

This method is suitable for large karst caves with a height of more than 10m and in a filled or semi-filled state, and the inner steel casing is used to sink through the silt, gravel accumulation layer, and karst cave area to enhance the strength of the pile foundation retaining wall and ensure the normal pouring of concrete. Prevent hole collapse and broken piles, but this method has high requirements for karst cave filling, the filling must be completely dense, and the filling quality will greatly affect the bearing capacity of piles; punching is used to form holes, although the hole wall is strengthened to a certain extent strength, but the foundation vibrates greatly during the hammering process, and there is a disadvantage that the verticality is not easy to control

[0006] In order to further improve the bearing capacity of bored piles in karst areas, on the basis of the casing followed by perforated piles, a support disc machine is used to squeeze and expand the bottom of the karst cave to form a disc-shaped hole, and the enlarged pile body is formed after pouring concrete. By changing the mechanism of the pile foundation, the bearing capacity can be enhanced, but the expanded pile body formed by this method is not easy to install in the steel cage, and the strength of the expanded pile body is not high

[0007] To sum up, although the existing bored piles in karst areas have accelerated the construction speed of pile foundations, the strength of the hole wall has been strengthened in the way of hole formation, and the easy pile formation in karst areas has been effectively solved by backfilling clay flake mixture and other methods. Problems such as grout leakage, broken piles, and karst cave collapses have occurred, but there are still areas for improvement, mainly reflected in the fact that the piling process has high requirements for the density of backfill, and the bearing capacity of pile foundations in karst cave areas may be far below the design value

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