Common Problems in Horizontal Directional Drilling

1. Guiding Deviation: The guide hole deviates from the designed trajectory, affecting the accuracy of pipeline laying. Main causes include:

Angle deviation between the drill rig positioning and the pipeline centerline;

External magnetic field interference (such as high-voltage lines or transformers) causing distortion of magnetic azimuth data;

Complex geological conditions (such as alternating soft and hard strata) causing drill bit deviation;

Insufficient operator experience or measurement errors.

2. Mud Leakage: Mud gushes out from unexpected locations on the surface, potentially polluting the environment and affecting construction safety. Common causes include:

The drilling path passes through fault zones or fractured areas, forming mud channels;

The entry and exit points are too shallow, causing significant soil disturbance and poor stability;

The annular space of the guide hole is too small, leading to poor slag removal and increased mud pressure, potentially causing ground fracturing.

3. Drill Tool Damage: Breakage, wear, or malfunction of the drill rod, drill bit, or reamer. Main contributing factors:

High-hardness rocks or obstacles in the formation cause uneven stress;
Excessive drilling speed leads to equipment overload;
Inadequate quality or maintenance of the drilling tools;
Frequent alternating stress triggers the "rope swing effect," causing drill pipe fatigue fracture.

4. Pullback Obstruction
Excessive resistance during the pullback process makes it difficult to pull the pipe in smoothly. Common factors include:

Insufficient borehole diameter or excessive borehole enlargement step difference results in an uneven borehole;
Steps, narrowing, or sediment accumulation within the borehole increase friction;
The formation consists of loose sand layers, gravel layers, or other weakly cemented structures, resulting in poor borehole stability.

5. Borehole Instability
Manifests as narrowing, collapse, or even surface subsidence. The causes include:

Minerals absorbing water and expanding when traversing clay layers, reducing borehole wall strength;
Improper mud pressure control (too high pressure causes cracking, too low pressure leads to loss of protection);
Excessively high mud flow velocity creates turbulence, eroding the borehole wall;
External disturbances (such as vehicle traffic) exacerbate soil loosening.

6. Borehole Shrinkage and Borehole Collapse

Borehole Shrinkage: Commonly seen in soft soil layers, the borehole diameter naturally shrinks, compressing the pipe;

Borehole Collapse: Commonly seen in sandy clay and loose backfill layers, easily causing drill bit burial and jamming, and in severe cases, road subsidence.

7. Difficulties in Construction with Quicksand Layers
Quicksand has adsorption properties, easily causing increased drag resistance. It is necessary to emulsify the quicksand with heavy colloidal solid phase mud to suspend and discharge it.

8. Mud Loss and Seepage

 Mud Loss: Occurs in loose strata or areas with low groundwater levels, preventing mud from returning.

 Mud Seepage: Mud seeps out from cracks in the ground during pullback, especially into residential or livestock areas.

9. Drill Pipe Fracture
 During long-distance drilling, drill pipes are subjected to combined tensile and torsional stresses. If the geological formation is complex or improper operation is used, fractures are likely to occur, leading to project interruption.