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Common Issues and Solutions in Bored Pile Construction

Bored piles offer significant advantages such as vibration-free construction, minimal soil displacement, low noise levels, and suitability for urban areas with dense building concentrations. As a result, they are widely used in construction projects. However, several issues may arise during the construction process. Below, we summarize common problems and their solutions.

1. Deviation (Oblique Hole)

Causes:

  1. The drilling rig is not level, or the construction site is uneven and uncompacted, leading to uneven settlement during drilling.

  2. The drilling platform foundation is unstable or not level, causing uneven deformation of the rig frame.

  3. Bent drill rods or loose connections result in excessive drill bit wobbling.

  4. Uneven soil hardness causes an unbalanced force on the drill bit, or obstructions like boulders are encountered.

Preventive Measures:

  1. Ensure the site is leveled and compacted before rig setup. Adjust the rig to a horizontal position and frequently check its alignment during drilling.

  2. Align the rig’s pulley groove, drill rod chuck, and pile centerline vertically to prevent excessive movement.

  3. Regularly inspect drill rods; replace or straighten bent ones.

  4. When using impact drilling, avoid excessive stroke and opt for secondary hole formation to ensure verticality.

2. Hole Shrinkage

Causes:

  1. Weak soil layers compress inward under earth pressure.

  2. Expansive clay layers absorb water and swell, reducing hole diameter.

  3. Excessive drill bit wear without timely repair leads to undersized holes.

Preventive Measures:

  1. Frequently ream the hole when encountering weak or expansive soils.

  2. Regularly inspect and repair worn drill bits before enlarging the hole to the designed diameter.

3. Hole Wall Collapse

Causes:

  1. Low-viscosity slurry fails to stabilize the hole, or leaks occur due to shallow or poorly sealed casing.

  2. Insufficient slurry density reduces hydrostatic pressure on the hole wall.

  3. Rapid drilling in loose sand prevents proper mud cake formation.

  4. Long pauses in drilling lower the slurry level, reducing wall pressure.

  5. Improper handling damages the whole wall during drilling or rebar cage installation.

  6. Vibrations from nearby heavy machinery or traffic.

  7. Delayed concrete pouring after hole cleaning.

Preventive Measures:

  1. Avoid heavy equipment or temporary roads near the drilling site.

  2. Compact a 50 cm clay layer beneath and around the casing to prevent water infiltration.

  3. Ensure casing penetrates soft layers and joints are watertight.

  4. Adjust slurry density and viscosity based on soil conditions; reduce speed in sandy layers.

  5. Maintain continuous drilling without unnecessary stops.

  6. Handle rebar cages and drill tools carefully to avoid wall contact.

  7. Pour concrete promptly after hole cleaning.

  8. Prevent direct water jetting on hole walls and surface water accumulation.

4. Broken Pile (Segregation or Discontinuity)

Causes:

  1. Low-slump or segregated concrete blocks the tremie pipe, leading to breaks if unresolved before setting.

  2. Incorrect tremie pipe height leaves the initial concrete unsubmerged.

  3. Over-extraction of the tremie pipe exposes it above the concrete surface.

  4. Rebar cage obstruction prevents concrete flow before setting.

  5. Leaky pipe joints allow slurry infiltration, creating weak layers.

  6. Excessive pipe embedment causes jamming or breakage.

  7. Prolonged concrete pouring interruptions exceed the setting time.

Preventive Measures:

  1. Test pipes for leaks and strength before use; use larger diameters where possible.

  2. Position the tremie pipe 40–50 cm above the hole bottom, ensuring ≥1 m initial concrete cover.

  3. Maintain 18–22 cm slump and consider retarders for long pours.

  4. Use butt-welded rebar cages to avoid tremie pipe snags.

  5. Measure concrete depth before extracting pipes; remove only one section at a time.

  6. Keep backup equipment and materials to ensure continuous pouring.

  7. Clear blockages by pipe vibration, rod insertion, or mechanical agitation.

  8. Rotate the pipe to detach from stuck rebar cages.

Safety Precautions

  1. Install warning lights and barriers around slurry pits and open holes.

  2. Avoid dropping rebar sections; ensure safe clearance before moving cages.

  3. Maintain 5 m spacing for oxygen and acetylene cylinders in upright positions.

  4. Verify welding quality and use proper lifting techniques for rebar cages.

  5. Secure work platforms and pipe holders during concrete pouring.

By addressing these common issues proactively, construction teams can ensure efficient and high-quality bored pile installation.

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