Sharing of construction methods for drilling rock-socketed piles with core barrel with roller bits

1. Characteristics of construction methods

1) The tools used in this construction method are basically the same as those required for drilling steel particles and alloys. The only difference is that the drill bit, a rock crushing tool, is replaced and a weighter is added. It can be promoted and used in general rock-socketed pile construction sites.

2) Easy to operate and wide adaptability. It can be drilled without circulation or with reverse circulation. Production workers can master the operation technology after short-term training.

3) This construction method breaks the rock uniformly, has high efficiency, has lower construction costs than alloy drilling, and has good hole-forming quality.

2. Scope of application

This construction method is suitable for the construction of rock-embedded pile holes with a pile diameter within φ1500mm and a relatively flat rock surface.

3. Process principle

1) When the single cone of roller bit is working at the bottom of the hole, it not only revolves around the drill pipe string, but also rotates around the center axis of the cone palm. Its rotation is in the form of rolling, and the running resistance is small, so it can withstand large drilling pressure.

2) When the roller bit is in contact with the rock at the bottom of the hole, the contact area between the alloy inserts on the tooth palm and the rock is small (fulcrum contact), and it is easy to obtain a higher unit axial pressure to facilitate crushing of the rock.

3) When the roller bits at the bottom of the hole, in addition to the axial pressure of the drill string, it is also affected by the impact load caused by the change in the height of the cone center during rotation, which improves the rock crushing effect.

4) When the roller bits at the bottom of the hole, it crushes the rock alternately. Each working time is short and the wear rate is low, which is beneficial to extending the life of the drill bit.

4. Process flow

1) Use alloy drill bits for pile hole opening and soil covering construction, and follow the rotary drilling cast-in-place pile construction procedures.

2) When using alloy drill bits to construct into strongly weathered rock formations or hard rock formations, you can lift the drill and replace it with a suitable core barrel with roller bit to drill to the depth required by the design.

3) When the construction reaches the required exploration level and the bedrock cuttings are recovered from the flushing fluid above the pile hole mouth, and after the on-site supervisor agrees with the final hole, it can be transferred to the clear hole, lower steel cage, lower conduit, and secondary Clean the holes and pour underwater concrete into piles.

4) After the core barrel with roller bit is lifted, the cuttings and sediments in the protective barrel should be removed in time, and the wear of the roller palm, support points and flange should be checked. If there is any damage, it should be repaired in time for use.