During rotary drilling rig construction, drill jamming and hole collapse are major safety hazards that can delay the project schedule at best and cause equipment damage or hole wall scrapping at worst. Mastering scientific emergency response plans and combining them with proactive preventive measures are essential to quickly resolve risks.
Drill Jamming: Accurately Identify Causes and Implement Tiered Solutions
Drill jamming is mostly caused by sudden changes in rock formations, drill cuttings accumulation, or improper operation. First, stop the machine to identify the cause: if the drill bit is stuck due to a hard rock interlayer, do not pull it out forcefully. Instead, start the power head to reverse at low speed, and gently lift and lower the drill pipe to loosen the rock formation with torque. At the same time, inject high-pressure mud into the hole to lubricate the gap between the drill bit and the hole wall.
If jamming occurs in a "candied haws" shape due to drill cuttings deposition, first increase the displacement through the mud circulation system to flush the sediment in the hole. After the slag content in the returned mud decreases, gradually lift the drill pipe using the "slow lifting and slow rotating" method. For large boulders stuck between the drill bit teeth, lower the drill pipe to the stuck position, adjust the angle through forward and reverse rotation, and use the drill bit's self-weight to impact the boulder until it detaches. After handling, check the drill bit wear to avoid secondary jamming.
Hole Collapse: Quickly Control Risks and Implement Tiered Repair and Reinforcement
Hole collapse mostly occurs in loose sand layers, silt layers, or when mud wall protection fails, characterized by mud blocks in returned slag and sudden sinking of the drill pipe. When collapse is detected, immediately lift the drill to prevent it from being buried, and quickly inject high-viscosity mud (viscosity 25-30s) into the hole to suppress the collapse range with mud pressure.
For minor collapse, after the mud stabilizes, use a small-diameter drill bit to ream the hole and re-form a stable hole wall. For deep collapse, lower a conduit and fill the hole with a mixture of clay and gravel in sections, then re-drill with the original drill bit after tamping. For collapse in quicksand layers, switch to bentonite mud and drive a steel casing outside the hole wall to the stable rock formation for double protection. After handling, inspect the hole wall verticality and diameter, and resume construction only after passing the inspection.
Proactive Prevention: Building a Risk Defense Line
Prevention is the key to reducing risks: conduct stratum exploration before construction and prepare high-quality mud in advance for loose layers; control the rotation speed and footage during drilling, and clean slag every 30cm in sand layers; regularly check mud performance and adjust viscosity and specific gravity in a timely manner. Replace with wear-resistant drill bits before hard rock construction, and slow down the drill lifting speed during operation in loose layers to reduce hole wall disturbance.
The core of handling drill jamming and hole collapse is to "first identify the cause, then implement measures, and operate cautiously". Construction teams should formulate emergency plans in advance, conduct regular practical drills, and combine handling skills with preventive measures to minimize construction risks and ensure smooth project progress.
