Prestressed Double-row Pile Strong Constraint Deep Foundation Pit Supporting Method

Abstract

The invention discloses a method for shoring a prestressed double-row-pile strong-constraint deep foundation pit and belongs to the technical field of civil engineering construction. The method comprises that two rows of reinforced concrete cast-in-place piles are arranged successively on the periphery of the foundation pit to be excavated, one row of reinforced concrete cast-in-place piles, which are close to the foundation pit, serve as front row piles, and the other row of reinforced concrete cast-in-place piles, which are close to existing buildings, serve as rear row piles; front row piles are formed through concrete pouring of reinforcing cages, and rear row piles are formed through concrete pouring after binding and planting prestressed anchor cables and reinforcing cages into pile holes; one ends of prestressed anchor cables, which are close to the ground, are anchor cable free sections, and anticorrosion is conducted on outer surfaces through grease, thin films and bellows, so that prestressed anchor cables can extend and retract freely; and prestressed anchor cables and reinforcing cages are bound and placed into pile holes through anchor cable anchoring sections at the other ends before grouting, front row pile top beams, rear row pile top beams and coupling beams are poured, and anchor cable anchoring pads which exert the prestressing force on prestressed anchor cables are arranged on rear row pile top beams. By the aid of the method, the horizontal stiffness and the pit overturning stability of a shoring structure can be improved, and security coefficients of peripheral buildings can be improved.

Description

technical field [0001] The invention belongs to the technical field of civil engineering construction, and is mainly used for foundation pit support projects adjacent to important buildings and unable to be anchored and internally supported. Background technique [0002] During the excavation of urban foundation pits, since there are many existing buildings around the foundation pits, and the foundations of the buildings are relatively deep, excavation on slopes is not allowed. In order to ensure the stability of the foundation pit and limit the level of the soil around the foundation pit Displacement and settlement must adopt a suitable foundation pit support scheme. Commonly used foundation pit support methods in practice include: (1) pile row plus prestressed anchor cable method. That is to lay a row of reinforced concrete piles around the foundation pit first, then excavate the soil step by step, and apply prestressed anchor cables at the design depth to limit the horizo...

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Problems solved by technology

[0003] The above three foundation pit support schemes have their own limitations and are not applicable in some specific environments: (1) The method of rowing piles and prestressed anchor cables requires that the foundation of surrounding buildings should not be too deep, otherwise the anchor cables will It cannot be constructed; the (2) row of piles plus internal support method requires a narrow and long foundation pit, and the direction of steel support should not be too wide, otherwise the deflection of the steel support will be too large; the (3) double-row pile method, in the foundation pit In the case of deep and strict deformation requirements of adjacent buildings, the horizontal stiffness and anti-overturning capacity of the retaining structure cannot meet the deformation requirements

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