In recent years, the demand for horizontal directional drilling (HDD) has surged dramatically. This trend is expected to continue over the next decade. Driven by increasing communication and energy needs, HDD contractors will face growing challenges when laying underground cables and pipelines.

    Traditional HDD tools can be applied to various projects. However, these products are not the most effective for drilling in rocky formations. When contractors encounter difficulties, unsuitable tools can slow down progress and increase costs. To successfully complete projects in hard rock formations, six key factors must be considered.

  1. Use Pneumatic Down-the-Hole Hammers

    Many leading HDD contractors have adopted pneumatic down-the-hole hammers for drilling in rock layers. Compared to conventional directional drilling tools used in softer formations, down-the-hole hammers offer significant advantages. Most importantly, down-the-hole tools can drill through a wide range of formations, including hard rock, broken rock, gravel, boulders, and loose geology. In the face of these geological conditions, down-the-hole tools have the highest success rate for penetration. In summary, down-the-hole tools are more efficient when drilling through rock, potentially halving the drilling time or more.

  2. Prepare All Tool Accessories at the Job Site

    Geological conditions and project designs can change at any time, so it is essential to have tool accessories ready to meet varying construction needs. As mentioned earlier, different drilling formations require different tools. For clay formations, traditional, common bits or tool components are needed, while rock geology requires down-the-hole hammers. Operators also need to use a diverter to connect the reamer and the pipe during reaming, allowing the reamer to rotate while keeping the pipe stationary, only subjected to drag force and not torque, to avoid twisting and damaging the pipe. Additionally, hydraulic quick-release clamps are recommended for safety. Finally, some consumables should be prepared, such as drill rods, stabilizers, drill bits, and guide bits. Operators need to prepare in advance to avoid chaos on the job site.

  3. Regularly Maintain Tools to Extend Lifespan

    Proper maintenance of tools is straightforward but often overlooked by many contractors. They frequently put tools away directly after use, only to pull them out for the next project. In fact, all tools should be cleaned promptly after each project. Operators should ensure that the diverter is lubricated after the project is completed; for pneumatic down-the-hole hammers, it is crucial to drain the air after use, store the hammer horizontally, and keep it in a dry environment. For long-term storage, the hammer should be disassembled, and all components checked to ensure proper operation and that the tool's interior is free from contamination.

  4. Factors to Consider When Selecting Hard Rock Tools

   There is significant performance variation among tools, and as the saying goes, "you get what you pay for." All drilling components, from the rig to the drill bit, must be compatible. Contractors should carefully select tools to avoid substandard products affecting project quality. When choosing hard rock tools, consider the following points:

• The rig's performance must match the geological conditions.
• Assess the cost of the tools and overall construction costs.
• Determine whether specific tools and equipment are necessary.
• Prioritize tools with guiding features, high penetration rates, easy maintenance, and low construction costs.
• Choose reputable tool manufacturers.
• Maintain close cooperation with project expert teams.

  5. Common Issues in Hard Rock Directional Drilling Projects

    Conducting thorough evaluations and project planning before starting can greatly reduce common mistakes. A qualified project engineer should do the following:

• Accurately understand geological conditions and develop corresponding construction plans before the project starts.
• Carefully select tools that closely meet construction requirements.
• Ensure the borehole diameter is 1.5 times that of the pipeline, avoiding sizes that are too large or too small.
• Seek expert advice promptly when difficulties arise.

    6. Keep Tools Clean

    For example, pneumatic down-the-hole hammers use compressed air as power, with pistons reciprocating within cylinders to repeatedly impact the rear of the drill bit, achieving continuous work and generating high-frequency energy impacts on the rock that needs to be broken. At the same time, the gas cools the drill bit and clears cuttings under certain airflow conditions to achieve drilling objectives. Ensure tools are clean before use to avoid jamming during construction. With the growing development of underground fiber optics, communications, and other municipal projects, teams with specialized operational knowledge and rich drilling experience will be the leaders in shaping the industry.

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