How does horizontal directional drilling solve the problem of high groundwater levels?

Today, Drillto Trenchless Co., Ltd., a manufacturer of horizontal directional drills, will introduce you to horizontal directional drilling. When drilling in areas with high groundwater levels, comprehensive technical measures, including mud performance optimization, formation improvement, managed pressure drilling, and emergency response, are required, along with targeted adjustments to the construction plan and equipment configuration, to ensure project safety and efficiency. The following are specific solutions:
1. Mud System Optimization: Building an "Underground Moat"
In horizontal directional drilling, mud is the core medium for stabilizing the borehole wall and balancing formation pressure. For high-water-level formations, specialized muds formulated with high-performance bentonite are required. By increasing viscosity (to 22-25s) and density (to 1.15-1.25g/cm³), a dense mud crust is formed to effectively control groundwater infiltration. For example, in the Fenshui River crossing project, to address the problem of collapse caused by a surge in water content in the pebble layer, the construction team added a polymer viscosity enhancer to control slurry filtration loss to less than 8mL/30min, significantly improving the wall protection.

II. Ground Improvement and Isolation: Building a "Double Line of Defense"

Casing-in-Pipe Technology: In areas at risk of collapse, an "outer casing + inner drill pipe" structure is employed. The outer casing is pre-inserted through the weak layer to create a stable channel. For example, in a project involving a section of heavily weathered granite that had become pulverized by water, 800mm Φ casing was used to isolate the high-water level stratum, successfully preventing collapse.

High-Pressure Jet Grouting: In fractured strata, high-pressure jet grouting is used to inject cement slurry, creating a continuous water-stopping curtain. This method reduced the ground permeability to 10⁻⁶cm/s in a river crossing project, effectively blocking groundwater seepage paths. 3. Managed Pressure Drilling and Dynamic Monitoring: Achieving "Precise Guidance"

A graded pressure control system: This system adjusts mud pressure in real time based on formation pressure, reducing the drilling speed to 0.3 m/min in areas prone to slurry leaks. The system also maintains mud pressure at 1.1-1.2 times the formation hydrostatic pressure to prevent sudden pressure changes that can trigger well kicks.

An intelligent monitoring platform: This system integrates water level gauges, inclinometers, and other equipment to monitor groundwater levels and borehole wall stability in real time. For example, one project leverages IoT technology to upload data every five minutes, automatically triggering an early warning mechanism when the water level fluctuates by more than 0.5 meters.

4. Emergency Response Plan: Building "Safety Redundancy"

Backup Equipment and Materials: A dual drilling rig system (e.g., a 600-ton main rig + a 350-ton auxiliary rig) is deployed on-site. If the main drill becomes stuck, the auxiliary rig can be quickly activated for rescue. Sufficient emergency supplies, such as cement slurry and casing, are also stockpiled to ensure leaks are sealed within four hours. Rapid Decision-Making Mechanism: A team of geological, construction, and safety experts was established to conduct real-time diagnosis of emergencies through a remote consultation system. For example, when a project encountered an underground cave, the expert team developed a "cement slurry plugging + steel casing follow-up" plan within two hours, reducing the downtime to 12 hours.