Steel casing pulling-removal method

Abstract

The invention relates to a steel casing pulling-removal method which comprises the following steps of (1) adopting impermeable soil for backfilling, and preparing a mud slurry for plugging a formation; (2) full-length welding a capping steel plate at the upper end of a steel casing, and reserving a gas-liquid inlet pipe; (3) installing and moving equipment in: moving lifting equipment in, and installing a rotary motor and a vibration hammer, wherein the vibration hammer is connected with the steel casing; (4) liquifying a soil mass: starting the vibration hammer to liquify the soil mass aroundthe steel casing; (5) pressurizing through a hydraulic system: applying water pressure in the steel casing, slowly lifting the lifting equipment, and starting the rotary motor at the same time; (6) pressurizing through an air pressure system: applying air pressure into the steel casing, and continuously lifting the steel casing; and (7) pressurizing through a hydraulic system: when the steel casing is 3 to 5m away from a pile block, stopping air feeding, releasing pressure, starting the hydraulic system to apply water pressure into the steel casing, and then pulling out of a pile body. By adopting the method, through a gas-liquid pressurization combination method, the difficulty in pulling and removing the steel casing under a special condition in the prior art is saved, and the safety and the stability in the steel casing pulling-removal process are effectively ensured.

Description

technical field [0001] The invention relates to the construction field of cast-in-situ piles, in particular to a method for pulling out steel casings for special formations. Background technique [0002] The super-long steel casing is often used as the enclosure structure for bored piles, and the vibration hammering method is often used for sinking the steel casing. For the removal of the steel casing, the removal needs to overcome the self-weight of the steel casing and the frictional resistance of the formation. Large-scale lifting equipment is often used to pull it out. tearing, the casing cannot be pulled out, and this method is not applicable to the limited use of large equipment; the air pressure jacking method, after the casing is capped, no air pressure is added to the casing, and the air pressure is used to overcome the self-weight of the casing and formation friction resistance, the casing is pulled out of the formation, but the air pressure control is more compli...

AI Technical Summary

Problems solved by technology

For the removal of the steel casing, the removal needs to overcome the self-weight of the steel casing and the frictional resistance of the formation. Large-scale lifting equipment is often used to pull it out. tearing, the casing cannot be pulled out, and this method is not applicable to the limited use of large equipment; the air pressure jacking method, after the casing is capped, no air pressure is added to the casing, and the air pressure is used to overcome the self-weight of the casing and formation friction resistance, the casing is pulled out of the formation, but the air pressure control is more complicated. The air pressure method first overcomes the self-weight of the casing and the static friction resistance of the formation. When the casing is lifted up, the static friction of the formation instantly changes to dynamic friction. Because the static friction force is greater than the dynamic friction force, upward acceleration is generated, and there is a greater safety risk. In addition, this method cannot be applied to water-permeable formations, such as sand layers; the vibratory hammer method pulls out the casing, firstly, the formation is liquefied, and the friction resistance of the casing becomes smaller. It is dynamic friction, which can reduce the lifting force, but this method cannot be used for the limited use of lifting equipment

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