The following issues should be paid attention to when drilling pilot holes with Horizontal Directional Drilling Machine

① In the process of drilling weathered granite layer, if the drill bit encounters dikes or pebbles with larger particle size in the process of drilling in pebble layer, the drilling trajectory may deviate from the design trajectory obviously. At this time, the deviation of the drill bit It's hard to predict. When the operator realizes that the drill bit encounters a small change such as hard objects or difficult drilling conditions, he should stop drilling immediately and check the position of the drill bit. At this time, the drilling pressure should be reduced, and the feed should be slowed down, so that the drill bit can pass through the area slowly. When drilling, the position of the drill bit should be checked more frequently.

② When the drill bit encounters a hard formation, it is usually necessary to increase the drilling pressure. However, increasing the drilling pressure will cause the drill pipe in the hole to bend. If the formation at the bent part of the drill pipe is soft, the bent drill pipe will enlarge the borehole. The steering probe can only determine the position of the drill bit, and it is difficult to determine the drilling trajectory formed by the bending of the drill pipe. In this case, it is necessary to appropriately reduce the WOB, and try to use percussion drilling to pass through the hard formation. At the same time, increasing the pump volume or injection effect may help to soften obstacles.