How are Larsen sheet piles removed?

After backfilling a deep foundation pit, Larsen sheet piles should be removed to facilitate reuse. Before removing Larsen sheet piles, the extraction method sequence, extraction conditions, and soil holes should be carefully and scientifically considered. Due to the vibration hazards associated with pile extraction, excessive pile clamping can cause ground collapse and movement, damaging the project's underground structure and endangering the safety of adjacent existing buildings, structures, or underground pipelines. Removing pile clamps is crucial. The key at this stage is to select a water and sand injection strategy.

What precautions should be taken when removing Larsen sheet piles?

Pile Extraction Method

Pile extraction is performed using a vibrating hammer. The forced vibrations caused by the hammer oscillate the soil, breaking the cohesion of the ground around the Larsen sheet pile, eliminating resistance to extraction, and using additional lifting force to extract the pile.

Common Problems in Pile Extraction

1. Pile Extraction Starting Point and Sequence

For closed Larsen sheet pile walls, the starting point for pile extraction should be five points above the corner piles. The starting point for pile extraction can be determined based on the pile's sinking condition. A jump extraction method can also be used if necessary. The order of pile extraction is reversed during foundation piling.

2. Vibration

When extracting piles, first vibrate the sheet pile lock with a vibrating hammer to reduce soil adhesion, then continue vibrating while extracting. For sheet piles that are difficult to remove, first vibrate the pile downward 100-300 mm with a diesel hammer, then switch to a vibrating hammer for further vibration.

The lifting equipment should be loaded slowly as the vibrating hammer is operated. The lifting force should generally be slightly below the compression limit of the shock absorber spring.

3. If the Larsen steel sheet pile cannot be removed, the following countermeasures can be taken:

1) Use a vibrator to strike again to eliminate resistance caused by adhesion to the ground and rust between the interlocking parts;

The order of pile removal is the opposite of the order of sheet pile support;

2) If the soil layer on the side of the sheet pile that bears the earth pressure is denser, drive another sheet pile around it and side by side to smoothly remove the original sheet pile;

3) Drill holes on both sides of the sheet pile and fill them with bentonite slurry to reduce resistance during pile extraction.

The solution is as follows:

Use a wooden pallet to lock the front lock of the sheet pile to the driven position of the foundation pile; install a movable pulley support in the gap on both sides of the sheet pile to prevent the sheet pile from rotating during lowering; and fill both sides of the buckle on both sheet piles with washers and pins.

Note:

This steel pipe pile consists of a steel pipe, a tongue and groove, and a tongue and groove pin. The left end of the steel pipe is perpendicular to the tongue and groove. The groove has a box-shaped cross-section with one side open. The groove side is provided with reinforcing ribs, and the right end wall of the steel pipe and the wall at the radius are vertically connected with a tongue and groove pin. The tongue and groove pin is in the shape of an I-beam.