Trenchless drilling rigs use high-pressure water jets to cut holes in soft ground. The directional drilling bottom drilling tool is composed of an elbow joint and a drill bit with a nozzle. Drill string back to straight hole. If the drill string does not rotate, under the action of feed force and water jet, a directional arc hole can be produced.
Trenchless drilling rigs in hard rock or pebble layers, the directional drilling method of jet drilling will be ineffective. At this point, a hole must be drilled. The drilling tool assembly in the hole is composed of elbow joint, screw motor and drill bit. Drill bits or diamond bits can be used according to the formation conditions.
For trenchless drilling rigs in soft formations with hard interlayers, the drilling tool assembly in the hole consists of elbow joints and alloy drill bits or roller cone bits. With a tricone bit, sometimes two of the three nozzles are plugged and the remaining one allows water to enter the formation. If a hard interlayer is encountered, the drill string can be rotated, and the rock can be broken by the tricone or alloy drill bit to cross the obstacle.
