The pile hole is not vertical after drilling, with a deviation exceeding the specified L/100.
The reinforcement cage cannot be smoothly lowered into the hole.
The drilling rig is not level, or the construction site is not properly leveled and compacted, leading to uneven settlement during drilling.
The base of the offshore drilling platform is unstable or not level, causing deformation of the rig frame during drilling.
The drill pipe is bent or has loose connections, resulting in excessive wobbling of the drill bit.
Obstructions near old structures push the drill bit to one side.
Uneven soil hardness or encountering boulders and protruding rocks causes uneven force on the drill bit.
Level and compact the construction site before positioning the rig. Ensure the rig remains level during drilling. Offshore platforms must be stable and level before drilling begins.
Align the rig’s pulley groove, drill pipe chuck, and pile hole center vertically to prevent excessive movement.
Conduct pre-drilling surveys near old structures and use impact drilling if obstructions are found.
Regularly inspect and replace bent drill pipes.
Use controlled impact drilling with secondary hole formation to ensure verticality.
Use impact drilling to break through boulders.
If deviation exceeds limits, backfill with clay and re-drill after compaction.
The hole diameter narrows at certain sections, preventing inspection tools from reaching the bottom.
Weak soil layers compress inward under pressure.
Plastic soil layers expand when exposed to water.
Worn drill bits are not repaired in time.
Frequently ream holes when drilling through weak or plastic soil layers.
Regularly inspect and repair worn drill bits to maintain the required diameter.
Ream the hole repeatedly until the design diameter is achieved.
The borehole walls collapse during or after drilling.
Insufficiently dense slurry, leaks in the casing, or inadequate slurry head pressure.
Rapid drilling in loose sand layers.
Long pauses in drilling reduce slurry pressure.
Equipment or vehicle vibrations near the site.
Delayed concrete pouring after hole cleaning.
Avoid heavy equipment near the drilling site.
Seal the casing bottom and sides with compacted clay (50 cm thick).
Adjust slurry density and viscosity based on soil conditions.
Maintain continuous drilling operations.
Ensure gentle handling of the drill bit and reinforcement cage.
If collapse occurs, backfill and re-drill after stabilization.
The drill bit becomes stuck and cannot rotate.
Irregular hole shapes (e.g., “bellmouth” holes or protruding rocks).
Sudden lowering of the drill bit or excessive slack in the cable.
Falling debris or tools blocking the bit.
Overly aggressive drilling after bit repair.
Gently maneuver the bit to loosen it.
Avoid abrupt lowering of the drill bit.
Ensure repaired bits match the hole diameter.
Use controlled blasting (in rock) to loosen the bit.
Apply a vertical or lateral force to free the bit.
Use jacks or pulley systems (ensure hole stability).
The casing bottom collapses, causing the rig to tilt.
Poor compaction around the casing.
Casing is placed in weak soil or sand layers.
Insufficient casing diameter.
Water infiltration loosens backfill.
Backfill casing bottom with at least 50 cm of clay.
Extend casing through weak soil layers.
Use a casing 20–40 cm larger than the drill bit diameter.
For offshore drilling, sink the casing deeper.
Relocate the rig, reinstall the casing, and re-drill.
The cage twists or bends during lifting.
Lack of temporary bracing for long cages.
Incorrect lifting points.
Insufficient stiffening ring spacing.
Add stiffening rings every 2–2.5 m and reinforce lifting points.
Minimize splicing; use temporary supports for long cages.
Choose optimal lifting points (1–2 points based on length).
If severely deformed, dismantle and reconstruct the cage.
The cage sinks or shifts after placement.
Inadequate fixation.
Measurement errors or collisions with the concrete tube.
Secure the cage to wooden blocks on the casing.
Compact backfill around the casing.
Double-check positioning before pouring.
Use a crane to reposition the cage before the concrete sets.
The cage rises during concrete placement.
Fast pouring near the cage bottom.
The concrete tube snags the cage during lifting.
Slow pouring near the cage; maintain 2 m clearance.
Center the tube and prevent snagging.
Rotate the tube to detach it; apply downward force if needed.
Mud enters the tube, causing voids or layers in the pile.
Blocked tubes due to poor concrete mix.
Excessive tube extraction.
Leaky tube joints.
Test tubes for leaks before use.
Maintain 40–50 cm tube-to-bottom clearance.
Use workable concrete (18–22 cm slump).
Avoid over-deep tube embedding (2–4 m ideal).
Vibrate or rod the tube to clear blockages.
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