Rotary Drilling Machinery and Technology: Drill Bit Selection and Problem-Solving

Rotary drilling is an advanced construction method widely applied in fields such as bridges, building foundations, and ground improvement. It relies on rotary drilling rigs, which use drill bits to cut through soil or rock and discharge it out of the borehole to create pile holes. The quality and efficiency of rotary drilling depend not only on the performance of the machinery but also on the proper selection of drill bits and effective handling of issues encountered during the process. This article explores the optimization of rotary drilling machinery and technology through drill bit selection and problem-solving.

1. Drill Bit Selection

The drill bit is the core component of rotary drilling, and its design and selection directly affect drilling efficiency and construction quality. Choosing the right drill bit for different geological conditions is critical:

1. Soil Layers
   For soft soil, clay, or sandy layers, auger bits or bucket bits are suitable. These bits efficiently cut and remove soil while minimizing disturbance to the surrounding ground.

2. Gravel and Cobble Layers
   In harder gravel or cobble layers, open-type bits are recommended. These bits reduce resistance during drilling and prevent blockage by cobbles, ensuring efficient drilling.

3. Hard Rock or Alternating Soft-Hard Layers
   For hard rock formations or complex layers with alternating soft and hard materials, wear-resistant alloy-toothed bits or coring bits are ideal. These bits enhance rock-breaking capability while reducing vibration impact on the equipment.

4. Specialized Layers
   For unique geological conditions like silt or expansive soils, drill bits with special cutting teeth are advised to adapt to varying ground hardness and prevent borehole collapse.

By selecting the right drill bit for specific ground conditions, drilling efficiency can be significantly improved while reducing equipment wear and construction risks.

2. Construction Issues and Solutions

During rotary drilling, various technical issues may arise, such as borehole collapse, drill bit blockage, and difficulty in debris removal. Effective solutions include:

1. Borehole Collapse

• Use slurry wall technology to form a protective film on the borehole wall to prevent collapse.

• Adopt casing wall technology for rigid support, especially in easily collapsible layers.

• Causes: This issue typically occurs in sandy or silty soil layers with high groundwater levels due to loose ground structures or inadequate support.

• Solutions:

2. Drill Bit Blockage

• Enhance the bit's debris removal capability and regularly lift the bit for cleaning.

• Use specialized drill bits, such as double-bottom open bits, to reduce blockage risks.

• Causes: Common in cobble layers or cohesive soils, where the drill bit may become clogged with accumulated materials.

• Solutions:

3. Debris Removal Challenges

• Optimize slurry mixture to improve debris-carrying capacity.

• Regularly inspect and maintain debris removal systems to ensure smooth operation.

• Causes: Excessive debris or improper slurry density may hinder debris removal and affect drilling efficiency.

• Solutions:

4. Drilling Deviation

• Level the equipment before starting operations to ensure vertical alignment.

• Use drill tools with high positioning accuracy to minimize deviations.

• Causes: Equipment misalignment, bent drill rods, or uneven ground conditions can result in drilling deviation.

• Solutions:

5. Equipment Failures

• Conduct regular inspections and maintenance to ensure equipment is in good working condition.

• Perform routine servicing of critical components like the power head and drill rods to prevent long-term fatigue or overload-related issues.

• Causes: Issues such as insufficient torque from the power head, drill rod deformation, or abnormal hydraulic pressure can lead to downtime or reduced efficiency.

• Solutions:

3. Optimizing the Construction Process

To further enhance drilling efficiency and quality, consider the following measures:

1. Pre-Construction Geological Survey
   Conduct comprehensive geological surveys to understand ground structures and soil characteristics, providing a basis for drill bit selection and construction planning.

2. Real-Time Monitoring of Construction Parameters
   Use advanced monitoring systems to track parameters like drilling pressure, torque, and vibrations, ensuring stable operations and prompt adjustments to abnormalities.

3. Team Coordination and Technical Support
   Equip the construction team with professional technical support to respond quickly to issues during operations, ensuring smooth progress.

4. Conclusion

Rotary drilling machinery and technology play a vital role in modern engineering construction. By selecting drill bits suitable for different geological conditions and implementing effective solutions for problems during construction, it is possible to improve efficiency, ensure quality, extend equipment lifespan, and reduce risks. Moving forward, further optimization of drilling processes and equipment performance should be pursued to meet the demands of more