The construction procedure for Rotary Drilling and Concrete Infilled Piles.

The term generally refers to the pile type constructed by a rotary drilling rig, officially known as Rotary Driven Bored Piles, commonly abbreviated in engineering as Rotary Piles. Owing to the use of machinery, it does not require a large workforce, thereby significantly reducing labor costs.

The hole formation process with a rotary drilling rig initiates when a bucket-type drill bit, equipped with a bottom valve, rotates to crush soil and rock, directly collecting the debris into the drill bucket. Subsequently, the rig's lifting mechanism and telescopic drill rod hoist the bucket out of the hole for soil disposal, repeating this cycle until reaching the designed depth. For cohesive soils with good bonding properties, dry drilling or clear water drilling techniques can be employed without requiring slurry support. Conversely, in loose and collapsible soil strata or where groundwater is present and the borehole walls are unstable, static mud walling is essential, involving injecting stabilizing mud or fluid into the hole to maintain its integrity.

**(1) Surveying and Layout, Positioning**

1. The center position of each pile is marked using a total station, with wooden stakes placed at these points. A circle is drawn around the stake by pulling a line and scattering lime powder; the drilling rig is then positioned with its center aligned to the pile center. Allowable deviations for pile positioning in a group are 20mm, while for single-row piles, it is 10mm.

2. Installation and positioning of the casing: The deviation between the center of the casing and the pile center must not exceed 50mm.

**(2) Casing Installation**

1. The casing should be fabricated from steel plates no less than 10mm thick.
2. The inner diameter of the casing should be 200-300mm larger than the drill bit diameter.
3. The top of the casing should have 1-2 overflow holes.
4. The top of the casing must extend at least 300mm above ground level.
5. The standard depth for casing installation ranges from 2 to 4 meters.
6. After installing the casing, its displacement and verticality must be checked, allowing a 50mm tolerance for the center alignment and a maximum vertical deviation of 1%.

**(3) Checking the Pile Central Axis**

**(4) Drilling Rig Placement**

1. The rig features an onboard leveling system to adjust the verticality of the drill rod.
2. Drill tools include: rotary drilling buckets, tube-type drill bits, bell-bottom drill bits, debris retrieval tubes, core drilling buckets, and cone spiral drill bits.

**(5) Drilling Operations**

1. Prior to commencing drilling, notify the site supervisor and the project engineer to verify the pile number, design diameter, and length against those from the advance drilling records, and document the commencement time of drilling.
2. Implement an intermittent piling sequence, ensuring a minimum safety distance of four times the pile diameter, or a waiting period of no less than 36 hours, between recently poured concrete piles and adjacent ones being drilled. The excavated soil should be kept at least 6 meters away from the pile opening and promptly removed.
3. To ensure stable and safe operation of the rotary drilling rig, lay steel plates (base plates) that can support its secure movement and operation on the site if necessary.
4. While drilling, closely monitor any movement of the casing or tilt of the drill rod, promptly rectifying any issues identified.