During rotary drilling rig construction, slippage at the bottom of the hole is a common problem, making drilling difficult. The main reasons for this are as follows:#drill and hammer drill#
1. Mud Formation
Slippage frequently occurs in sub-clay sub-slab drilling because the concentration and specific gravity of the mud increase during repeated use, causing the drill bit to float. When the drill bit is forcibly pushed into the hole, the excessive speed causes the mud to act as a lubricant, smoothing the clay at the bottom of the hole and the cutting surfaces of the drill teeth.#drill and hammer drill#
2. Drill Tool-Related Issues
Slippage can be caused by a series of factors, including misalignment between the drill bit and drill rod centers, a tooth angle less than 45 degrees, an unsuitable center cone, excessively dense tooth arrangement, and severe drill bit wear.
3. Geological Issues
Some geological formations consist of mudstone, which has low compressive strength (around 550 kPa) but is very dense and prone to slippage when wet. Solving mudstone slippage requires addressing the three issues mentioned above and carefully selecting the drill bit. This necessitates experienced operators.#drill and hammer drill#
4. Drill Rig Slippage During Construction
Excessive drill bit speed on the rotary drilling rig, lack of fast and slow speed settings, structural defects, insufficient pressure, and the drill rod's natural bending due to prolonged use can all cause slippage.
5. Improper Operating Methods Can Also Cause Slippage
Over-digging, where the bottom of the borehole is excessively flattened, can lead to slippage in subsequent drill passes. Incomplete closure of the drilling rig during drilling, resulting in a large amount of soil falling to the bottom of the hole, also causes slippage. Excessive starting speed leads to drill bit jamming; therefore, proper selection of operating procedures and drill bits is the fundamental solution to slippage problems.#drill and hammer drill#
