1. When the drilling starts,the pilot bit drive the ring bit down to the hole, followed the casing shoe and casing tube.

2. When drilling the bedrock,reserve rotation of the tools and pull the pilot bit out from the hole, leaving the ring bit in the hole.

3. Pour the concrete or do the next construction work.

4. Using normal bit to drill to the desried depth.

Applications:
1. Geological disaster prevention and control (anchor cables, anchoring, landslied prevention and control, high slope stabilization);
2. Curtains and cofferdams (curtains and cofferdams of hydropower stations, reservoirs, etc.);
3. Building foundation treatment (slope support treatment of high-rise buildings, bridge piers, deep foundation pits, etc.);
4. Tunnel pipe shed support (support treatment of highwat and railway tunnels);
5. Water well wall protection.