Technology for Controlling and Correcting Hole Deviation in Rotary Drilling Rig Boring

    The verticality of the hole formed by the rotary drilling rig directly affects the bearing capacity of the pile foundation and structural safety. During construction, hole deviation often occurs due to uneven geology, improper equipment posture, inappropriate drill tool combination, and incorrect operating parameters. Effectively controlling the guidance, timely correcting deviations, and standardizing re-drilling are the keys to ensuring the quality of the formed hole.

    Guidance control is based on prevention, stabilizing the drilling trajectory from three aspects: equipment, drill tools, and technology. The drilling rig must be positioned on a flat and stable surface, and the verticality of the mast must be checked to ensure that the power head, drill pipe, and the center of the casing are coaxial. For drill tools, structures with a central pilot tip are preferred, combined with an extended barrel and guide ring to enhance the hole wall constraint and centering ability. The drill pipe is equipped with a stabilizer to reduce swing and lateral deviation. Drilling parameters should be adjusted according to the stratum; for soft-hard interbeds and inclined rock surfaces, a mode of light pressure, slow rotation, and short footage is adopted to avoid the drill bit deviating due to uneven force.

    Deviation correction for hole deviation follows the principle of early detection and early treatment, with graded disposal based on the degree of deviation. In case of slight deviation, retract 1 to 2 meters and repeatedly sweep the hole, level the steps at the bottom of the hole, reduce the drilling pressure and rotation speed, and slowly correct the trajectory in the opposite direction. For moderate deviations, eccentric drill bits, deviation correctors, or bent joints can be used for directional correction, combined with pilot holes drilled by small drill bits followed by reaming to form the hole, gradually returning to the center. When encountering inclined hard rock surfaces, first use a flat-bottom drill bit to level the rock surface, then resume normal drilling.

    Severe hole deviation or bent holes require the backfilling and redrilling process. First, clean up the sediment and debris at the bottom of the hole, then use clay, plain concrete, or graded sand and gravel to backfill to 1 to 2 meters above the starting point of the deviation. After the backfill is compacted and reaches a certain strength, re-drilling is carried out. During re-drilling, strengthen the guiding measures, lengthen the casing, optimize the drill tool combination, strictly control the attitude and parameters throughout the process to prevent secondary deviation. Monitor the verticality throughout the construction process, and immediately stop the machine for adjustment when abnormalities are found to avoid the expansion of deviation leading to the scrapping of the hole position.

    The core of hole deviation treatment is prevention first, dynamic regulation, and graded disposal. By stabilizing the equipment attitude, strengthening the drill tool guidance, optimizing construction parameters, and standardizing the deviation correction and re-drilling processes, the hole-forming accuracy can be effectively controlled, meeting the quality requirements of pile foundation projects, and improving construction efficiency and structural reliability.