Pay attention to the following problems when drilling pilot holes with horizontal directional drilling rig

① If the bit encounters rock vein or pebbles with large particle size during drilling in weathered granite layer, the drilling track may deviate from the design track obviously, and the deviation of the bit is difficult to predict. When the operator is aware of minor changes such as hard objects or difficult drilling conditions encountered by the drill bit, he/she should immediately stop drilling and check the position of the drill bit. At this time, reduce the WOB, feed slowly, and let the bit slowly pass through the area. During drilling, the position of the drill bit shall be checked frequently.
② When the bit encounters a hard formation, the weight on bit usually needs to be increased. However, the increase of WOB will cause the bending of drill pipe in the hole. If the stratum at the bent part of the drill pipe is soft, the bent drill pipe will enlarge the hole. The direction control probe can only determine the position of the drill bit, and it is difficult to determine the drilling path formed by bending the drill pipe. In this case, the WOB should be properly reduced, and the percussive drilling method should be used to pass through the hard formation. At the same time, increasing the pump volume or jet effect may help to soften the obstacles.