A rotary drilling rig is a more advanced construction method in the construction of bored piles in recent years.

The principle of pile formation is to rotate a barrel drill bucket with a valve under the combined force of the torque of the drill pipe and the pressure system.

The drill slag that is rotated during the rotation of the drill bucket enters the drill bucket from the bottom of the drill bucket.

When the drill bucket is filled with drill slag, the torque reaction force is significantly increased and reflected by the sensing device in the operating room.

Subsequently, under the operation of the crew, the drill rod is rotated in the reverse direction, and the drill bit is lifted out of the hole by the drilling rig lifting device and the telescopic drill rod to unload the soil.

This cycle is repeated, taking soil, unloading soil continuously, and drilling straight to the design depth.

Its characteristics of high efficiency, environmental protection, and high benefit are suitable for projects with tight construction periods, large engineering volumes, and good geological conditions.
　　

1. Process flow
　　

The main procedures of bored piles include: measuring and laying out, forming holes, steel cage production, transportation and installation, concrete mixing, concrete pouring into piles, post grouting, etc.

The construction process is shown in Figure 1.
　　

2. Rig positioning
　　

The drilling rig can be in place only after the pile position is checked correctly and the protective tube is buried in accordance with the requirements.

The positioning of the pile machine must be accurate, horizontal, vertical, and stable.

The centerline of the drill rig's guide rod, the centerline of the maneuvering disk, and the centerline of the protective cylinder must be kept in the same straight line.
　　

3. Mud preparation
　　

During the construction of the bored pile, in order to prevent the hole from collapsing, stabilize the water level in the hole and facilitate the entrainment of the drilling ballast, the mud is prepared by using bentonite to protect the wall.

Mud wall protection uses the pressure difference between the mud and groundwater to control the water pressure to ensure the stability of the whole wall, so the specific gravity of the mud plays a key role in maintaining this pressure difference.

If the specific gravity of the mud in the borehole is too small, the mud wall will easily lose its role in blocking the collapse of the soil; if the specific gravity of the mud is too large, it will easily block the mud pump and even make the replacement of concrete difficult, making the quality of the pile difficult. Guaranteed.

To give full play to the role of mud, the selection of its indicators is very important. This requires that in the actual construction of the project, according to the specific conditions of the project, reasonably control the mud indicators in different soil layers.
　　

4. Drill into a hole
　　

In the hole formation, the construction is carried out according to the parameters determined by the trial construction, and a full-time recorder is set to record various parameters of the hole formation process, such as the addition of drill rods, drilling depth, geological characteristics, mechanical equipment damage, obstacles, etc.

Records must be serious, timely, accurate, and clear.