The rotary drilling rig, a hole-forming equipment gaining widespread acceptance in recent years, has become a widely recognized method in underground foundation construction. As the fastest-developing innovative pile hole construction technique, rotary drilling cast-in-place piles are hailed as a "green construction process" due to their high efficiency, superior quality, and minimal dust and slurry pollution. However, some issues have emerged. This article compares rotary drilling rigs with traditional impact and rotary drilling rigs, offering practical recommendations for selecting appropriate hole-forming equipment in pile foundation construction.

Here is an analysis and comparison between the three most common types of drilling rigs: impact, rotary and rotary drilling rigs.

1. Analysis of impact drill

Impact drilling rigs are versatile hole-forming equipment that combines both mechanical and hydraulic systems. They are adaptable to diverse geological conditions, including silty soils, sandy soils, gravel layers, pebbles, boulders, soft rock, and hard rock. These rigs are particularly effective for driving rock-socketed piles in mountainous and hilly areas. When encountering soft soil layers, operators can temporarily replace the surface soil to stabilize the drilling rig.

Impact drills can be self-assembled according to the actual site conditions and are characterized by simple operation. In terms of structural design and operational complexity, impact drills outperform rotary and rotary-digging rigs. When considering geological conditions alone without factors like project schedule or economic efficiency, impact drills remain universally applicable. Regarding hole formation speed, impact drills fall short compared to rotary and rotary-digging rigs in specific geological environments. In cost per linear meter for single-hole drilling, impact drills show the highest efficiency, rotary drills the lowest, while rotary-digging rigs occupy the middle ground.

2. Analysis of rotary drilling rig

Both positive circulation and reverse circulation drilling rigs are suitable for dry soil, soil layers containing small gravel or pebbles, and soft rock. However, they are not recommended for large tamping stone layers or hard rock strata. Positive circulation rigs are also applicable to silt and fine-medium-coarse sand layers. Conversely, reverse circulation rigs in sandy layers may cause borehole accidents if slurry formulation parameters are insufficient or drilling speed is excessive.

Rotary drilling rigs are particularly suitable for bored pile construction in inland plains with thick alluvial layers and coastal tidal flats. In terms of hole formation speed, rotary drilling rigs outperform percussion drills but lag behind rotary excavators. From an engineering cost perspective, rotary drilling rigs are the most economical among the three types of drilling equipment, being the most affordable option.

3. Deficiencies of impact and rotary drilling rigs

As discussed above, both impact drilling rigs and rotary drilling rigs share the common characteristics of being cost-effective equipment with simple operation. After decades of market selection, they have become mainstream machinery for pile foundation hole formation. However, with the advancement of society, some insurmountable shortcomings have gradually emerged:

Polluting the environment, not environmentally friendly

Both slurry wall construction and suspended sediment discharge require slurry. However, slurry production causes environmental pollution to both the construction site and surrounding areas, failing to meet modern society's growing demands for eco-friendly construction practices. The use of recycled slurry necessitates slurry ponds, which occupy significant construction space.

Slow hole formation

According to the normal construction quality requirements and general geological strata conditions, rotary drilling rig can drill holes about 8-IOm per day. However, the hole formation speed of impact drilling is slower.

Poor adaptability

In addition to the strong adaptability of impact drilling rigs, rotary drilling rigs cannot deal with harder strata beyond the strong weathered layers. Both impact drilling rigs and rotary drilling rigs can only drill vertical holes, not material holes.

Low degree of automation

The labor intensity of the operation workers is high. The working environment is poor and the automation degree of impact drillers and rotary drillers is not high. It is basically ear-wearing operation. The working environment of the workers is harsh, which does not meet the current social trend of humanization and high automation.

4. Analysis of rotary drilling rig

Environmental health

When a thousand holes are formed, there is no pollution to the site and surrounding environment. Even when static mud is used to form holes, compared with the pollution of impact drillers and rotary drillers, rotary drilling machines produce less pollution to the site.

Formation is formed quickly

In standard geological formations, rotary drilling rigs achieve 4-6 times faster hole formation rates than conventional drilling rigs. When constructing bridge pile foundations within 10 meters of length in typical strata, the drilling process meets quality control standards for qualified pile foundations. While rotary drilling typically takes 24-36 hours, skilled rotary drilling operators with technical guidance can complete pile foundation drilling in just 6-9 hours. This demonstrates the significant advantage of rotary drilling rigs in foundation construction.

Strong adaptability

Rotary drilling rigs can be equipped with various drill bits. Common types include rotary drill bits and rotary buckets. Additionally, there are specialized tools such as cylindrical coring bits, expanded-base drills, impact drills, and grab cone drills designed for different geological conditions. These rigs can drill through sand layers, soil layers, rock layers, and other formations. Known as "rotary drills," these machines can move independently, ensuring precise and convenient positioning before drilling. Not only can they drill vertical piles, but they are also capable of constructing inclined piles.

 supermatic

The operation labor intensity is small. The working environment is comfortable. The rotary drilling rig is a product integrating high power, full hydraulic, mechatronics and operational comfort (humanization). It is the crystallization of modern high technology, embodying the unity of humanization, intelligence and high efficiency.