The symmetric drilling method, also known as symmetrix drilling, is a specialized technique used for drilling large-diameter boreholes in challenging geological conditions, such as hard rock formations. It's commonly employed in various applications including foundation drilling, micropile installation, and anchoring.
Here's how the symmetric drilling method works:
Drill Bit Design: The drill bit used in symmetric drilling consists of a central pilot bit surrounded by multiple radial wings or cutters arranged symmetrically around the circumference of the bit.
Borehole Creation: Initially, the central pilot bit drills a small-diameter pilot hole into the rock formation. As the drilling progresses, the radial wings or cutters engage with the surrounding rock, gradually enlarging the borehole to the desired diameter.
Simultaneous Casing Installation: While drilling, casing or steel tubes are concurrently installed behind the symmetric drill bit. These casings provide immediate support and stabilization to the newly drilled section of the borehole.
Cuttings Removal: Cuttings generated during drilling are flushed out of the borehole through the annular space between the casing and the borehole wall. This continuous flushing action helps maintain borehole stability and prevents blockages.
Completion: Once the desired depth and diameter of the borehole are reached, the symmetric drill bit is removed, leaving the casing in place. Depending on the application, grouting or other materials may be injected into the annular space between the casing and the borehole wall to further stabilize the borehole.
The symmetric drilling method is favored for its ability to drill large-diameter boreholes efficiently in challenging geological conditions. It ensures borehole stability and integrity, making it suitable for construction projects such as foundation drilling where stability is crucial.
