Causes of Hole Collapse in Rotary Drilling Rig Construction and On-site Emergency Disposal Plans

    In the drilling operation of rotary drilling machines, hole collapse is a common quality hazard that affects construction safety, progress, and cost. It can range from minor issues such as hole enlargement and diameter expansion to severe issues such as buried drilling and broken rods, and even pose risks to the foundation pit and surrounding structures. Scientific prediction of causes and standardized implementation of emergency response measures are key to ensuring the quality of borehole formation and construction safety.

    Geological conditions are the primary factor causing collapse of boreholes. Unstable geological layers such as loose sand layers, fine sand, silty soil layers, and backfill soil have poor self bonding strength and are prone to instability under drilling disturbances, mud erosion, and changes in water head pressure. When the groundwater level is high, the confined water is active, and the formation is saturated with water, the strength of the soil on the borehole wall decreases significantly, which is also an important reason for the high incidence of borehole collapse.

    Improper construction operations can also exacerbate the risk of borehole collapse. The mud density, viscosity, and colloid rate do not meet the standards, making it impossible to form effective protective mud skin and causing the pore wall to lose protection; The casing is buried too shallowly and the surrounding backfill is not compacted, resulting in hole leakage and water head loss; Excessively fast drilling speed, large hole expansion coefficient, and excessive lifting and drilling can all cause suction effects, which can damage the stability of the hole wall. Excessive pile load at the hole opening, mechanical equipment vibration, and construction disturbance caused by adjacent pile positions being too close can also induce hole collapse.

    After a hole collapse occurs, drilling should be stopped immediately on site, and forced continuation of operations is strictly prohibited. Priority should be given to ensuring the safety of personnel and equipment. Minor collapse of the hole can be addressed by first increasing the mud density and viscosity, supplementing high-quality mud to stabilize the water head, slowly sweeping the hole to repair the hole wall, and checking whether the casing leaks and reinforcing the hole opening. If the collapse range is large, clay, cement soil or concrete should be backfilled in a timely manner. The backfill height should exceed the collapse section, and it should be left to settle and compacted before slowly drilling again to strengthen the protective wall.

    For situations where there is a serious risk of hole collapse or buried drilling, all actions must be immediately stopped to maintain the stability of the drilling rig, and blind lifting and pulling of the drill is strictly prohibited. Quickly backfill and compact the material to stabilize the hole position, prevent collapse and expansion, synchronously clean up the pile load at the hole opening, isolate the vibration source, and develop a special plan to handle the drilling tools after the hole is stable to avoid accident escalation.

    Prevention is far more important than disposal. Conduct a detailed geological survey before construction and develop a targeted wall protection plan; Strictly control the mud indicators to ensure the quality of the buried cylinder and the height of the water head; Optimize drilling parameters to reduce borehole wall disturbance; Reasonable planning of pile position sequence and construction spacing can significantly reduce the probability of hole collapse. Adhere to the principle of stabilizing the borehole first, then disposing of it, and then resuming work, in order to efficiently control risks and ensure the quality of borehole formation and continuous construction.