How to prevent problems during horizontal directional drilling operations

I. Prevention of Guiding Deviation

1. Precise Positioning: Repeated adjustments are made before the drilling rig is positioned to ensure that the deviation between the drilling rig's centerline and the designed crossing axis is controlled within 0.1°.

2. Resistance to Magnetic Interference: On-site surveys are conducted before construction to identify sources of magnetic interference such as high-voltage lines and underground metal structures; straight-line drilling is used in interference sections, and the trajectory is corrected after separation.

3. Personnel Training: Operators must undergo professional training and be familiar with the operating logic of the directional control system to reduce human error.

II. Prevention of Grout Leakage

1. Geological Improvement: High-pressure jet grouting + compaction grouting is used for pretreatment of fractured strata and backfilled areas to enhance the integrity of the formation.

2. Optimization of Design Parameters: The entry and exit angles and radius of curvature are increased, and the length of the shallow buried section is shortened, allowing the borehole to quickly enter stable strata. 3. Mud Control:
Mix Optimization: Use non-dispersible, low-solids mud to balance viscosity and fluidity.
Pump Rate Adjustment: Follow the principle of "high at both ends, low in the middle" to avoid sudden pressure increases.
Real-time Monitoring: Immediately set up a temporary mud storage area and pump out any mud leakage to prevent further spread.

III. Drill String Damage Prevention
Equipment Selection and Matching: Use super roller cone reamers or large-diameter rock reamers in hard rock sections.
For long-distance traversal, it is recommended to have one drilling rig at each entry and exit point for easy accident handling.

2. Stress Control: Install a centralizer at the front end of the reamer to reduce torque fluctuations and lower the risk of "rope swing effect."
Strictly control drilling speed to avoid overloading.

3. Quality Control: Before construction, a professional team will inspect the drill pipe threads and body wear to prevent operation with defects.

IV. Strategies for Handling Drill Pipe Pullback Obstruction

1. Sufficient Enlargement: Enlarge the borehole in stages according to the formation properties. The final borehole diameter should be 10%~30% larger than the outer diameter of the pipe to ensure unobstructed flow.

2. Smooth Borehole: Avoid excessive enlargement stage differences to reduce the formation of "steps" and prevent pipe jamming.

3. Assisted Drill Pipe Pullback: Use a pipe pusher to provide rearward thrust; when the drill is stuck, use a combination of a pipe rammer and pulley system with multiple winches in parallel for emergency pullback.

V. Treatment of Borehole Wall Instability

1. Mud Wall Protection: Control the mud pressure to be close to the original formation stress to prevent excessive pressure from causing fracture expansion or excessive pressure from causing collapse; It is recommended to use non-dispersed low-solids mud, as its low solids content is beneficial to borehole wall stability.

2. Flow Rate Control: Maintain the mud in a laminar flow state to reduce the scouring effect on the borehole wall.

3. Geological Prediction: When traversing clay layers, pay attention to the water absorption and expansion characteristics of minerals (such as montmorillonite) and adjust the mud mix ratio in advance.

VI. Pipeline Undulation Suppression

1. Geological Pre-survey: Conduct a detailed investigation of the geological stratification along the traversal path before construction, and assess the risks of silt subsidence and sand layer uplift.

2. Dynamic Control: Frequently measure and adjust in areas with signal interference; during the jacking process, prioritize applying tension to straighten the guide rod before applying torque for advancement.

3. Synchronous Grouting: Inject sufficient and timely mud to suspend silt and prevent sedimentation that could cause the pipeline to float.

VII. Comprehensive Management and Support

1. Personnel Quality Improvement: Regularly organize technical briefings and practical drills to strengthen safety awareness and emergency response capabilities.

2. Systematized Equipment Maintenance: Establish a drilling tool life assessment mechanism, scientifically arrange maintenance cycles, and extend service life.

3. Intelligent Monitoring Application: Introduce a BIM + distributed fiber optic monitoring system to achieve settlement early warning, control surface deformation within 15mm, and meet municipal standards.