Different Methods Are Adopted for The Construction of Small Rotary Drilling RIGS in Different Geological Conditions

Small rotary drilling RIGS need to flexibly adjust their construction methods under different geological conditions to ensure the efficiency and quality of hole formation. For the common stratum characteristics, the following differentiated construction strategies can be adopted:

1. Clay/silty clay strata: Short spiral drill bits are used for low-speed drilling, and the self-weight of the drill bucket is utilized to cut the soil to prevent the drill from getting stuck due to high-speed rotation. Lift the drill and clear the cuttings every 1 to 2 meters of progress to prevent the accumulation of cuttings from affecting the drilling speed.

2. Loose sand layer/gravel layer: The mud wall protection process is preferred, and a double-bottom sand dredging bucket is used in combination. When drilling, control the speed at 0.3-0.5 meters per minute and inject high-viscosity mud (specific gravity 1.2-1.3) simultaneously to prevent hole collapse.

3. Hard plastic soil layer/strongly weathered rock layer: Replace with a truncated barrel drill or a cone drill bit, and adopt a staged drilling method: First drill the guide hole, and then expand the hole to the designed diameter. The drilling pressure should be controlled at 80-120kN and the rotational speed at 8-12r/min to prevent excessive wear of the drill bit.

4. Backfill soil/miscellaneous fill soil layer: The full casing follow-up process is adopted, and the steel casing is pressed in by a vibrating hammer to isolate obstacles. In coordination with the rotary drilling bucket, remove debris such as bricks and concrete blocks. The depth of the casing should exceed the fill soil layer by 3 to 5 meters.

5. Soft soil layer with silt: Reduce the drilling speed to 0.1-0.2 meters per minute, and adopt the principle of "slow advance and frequent lifting of the drill". Cement slurry can be injected to improve the soil, or a drill pipe with a spray port at the bottom can be selected for simultaneous solidification treatment.

6. Moderately weathered/slightly weathered rock strata: Equipped with a down-the-hole hammer composite drill bit, it utilizes a combination of impact and rotation for rock breaking. First, the rock strata are impacted and crushed at a low rotational speed (5-8r/min), and then the debris is cleared using the sand dredging bucket. If necessary, static blasting pretreatment is combined.

Conclusion: The construction of small rotary drilling RIGS requires "tailoring policies to local conditions". Appropriate drill bits and processes should be selected based on the hardness of the formation, particle composition and hydrological conditions, and the drilling parameters should be dynamically adjusted at the same time. Scientific construction methods can not only enhance the efficiency of hole formation, but also reduce equipment wear and tear, ensuring the quality and safety of the project.