Understanding the Basics of Impact Moling: What You Need to Know

Impact moling is a trenchless technology used for installing small-diameter pipes, ducts, and cables without requiring extensive digging. Instead of removing soil, a pneumatic tool compacts and displaces it, creating a bore for the installation. This method uses a “non-steerable” mole, which ensures precision and accuracy during the impact moling process.

At EPS-Trenchless Installations, our commitment to quality and detail ensures that each moling project is completed on time, within budget, and with minimal environmental impact.

What Are the Key Advantages of Impact Moling?

Impact moling is renowned for its simplicity and cost-effectiveness. Utility companies across the globe favour this method for installing service connections to gas, water, electricity, comms ducting and many more, typically under pavements and driveways for distances under approximately 45m. It requires minimal excavation, which means less disruption to the public and lower operational costs. 

The operational setup is straightforward, needing just a small air compressor and, occasionally, a mini digger for digging and reinstating pits.

What is the Demand For Impact Moling?

Impact moling is the most widely used trenchless construction method, with tens of thousands of units in service worldwide. The gas and water and construction industries have a significant demand for this technology, particularly for installing new service lines. 

Impact moling is well-suited for these installations due to its cost-effectiveness compared to other trenchless methods, especially for smaller projects and in ideal soil conditions.

he Applications of Impact Moling

Impact moling is widely used for installing gas, water, electricity, comms ducting and many more, particularly under pavements and driveways. It is effective for pipes up to approximately 125mm in diameter, though typically used for pipes between 25mm and 63mm.

Besides utility installations, impact moling is used for cabling, garden irrigation, landscape lighting, and drain replacements. The moling method is appropriate for compressible soils like clays, silt, and peat, but less suitable for sands and gravel, especially if densely packed. Solid rock is entirely unsuitable for this trenchless technology technique.

How Does Impact Moling Work?

Impact moling tools, also known as earth piercing tools or soil displacement hammers, consist of a steel tube with an air-powered piston, or striker. This piston strikes the tool’s nose, driving it forward through the soil. The soil is compacted and displaced laterally, forming a bore. The friction between the ground and the tool prevents backward movement, ensuring the mole moves forward. 

The tool operates untethered, relying on the frictional resistance of the soil to move forward. Some tools use a simple striking action, while others employ a two-stage action with a moving head to create a pilot bore and expand it to the final diameter.

The Impact Moling Installation Procedure

During the moling process, two pits are typically excavated, an entry pit and a reception pit. The mole is carefully aligned in the entry pit and driven forward in a straight line. If needed, the product pipe, cable, or duct can be towed during the boring process or inserted after the borehole is completed, depending on soil stability.

What Soil Conditions Can Moling Be Utilised In?

Impact moling is most effective in compressible soils such as clays, silt, and peat. It is less suitable for sand and gravel, especially if they are densely packed, and is entirely unsuitable for solid rock. Proper soil evaluation is crucial to determine the feasibility of impact moling for a specific project. The method works best in moderately compacted soil with consistent moisture content.

Changing ground conditions, such as natural strata variations (layers of different materials that naturally occur) or artificial backfills (materials used to fill excavated spaces), can affect the process. Identifying underground objects and potential obstructions is essential for planning the borehole route.

With EPS Trenchless Installations, we can install 100 metres of piping a day depending on the soil conditions, and install up to twenty metres of pipe in one shot in ideal ground conditions. Most mole shots are between 10 - 15 metres. HDD may be more suited for installations above 50 meters.

An Overview of Moling Equipment

Understanding the various moling tools and their specifications is crucial for selecting the right equipment for your project. Proper alignment, lubrication, and temperature management are essential for effective moling operations. With the right tools and preparation, impact moling can offer a cost-effective, efficient solution for trenchless installations.

Selecting the Correct Equipment

When selecting impact moling equipment, consider the project requirements, ground conditions, and the capabilities of different mole types. Moles are suitable for straight bores only, unlike Horizontal Directional Drilling which can install long curved bores. The size of the mole should match the diameter of the pipe being installed, with the borehole typically being 15-25% larger than the product pipe to allow for shrinkage and reduced friction. The tool should be properly aligned to ensure accuracy.

Types of Moling Tools

  • Non-Steerable Moles – Widely Used and Mostly Used:

    • Fixed Head vs Moving Head:
      • Fixed head moles have fewer moving parts, making them easier to maintain.
      • Moving head moles use a two-stage action where the chisel head creates a pilot bore, and the main casing expands it. These moles can handle adverse soil conditions better.

    • Replaceable Heads: 
      • Impact moles can use different tool heads to adapt to various soil conditions. Tapered heads are suitable for loose, wet soils without obstacles, while splined and stepped heads are better for compact, rocky soils.

  • Steerable Moles: Not widely used. Hdd was a better alternative.

    • Steerable moles use walkover tracking and remote steering, similar to horizontal directional drilling. These moles can follow curved trajectories and are more adaptable to changing ground conditions. They require a two-person team for operation: one to track and another to operate the mole. These moles were not very popular within the industry.

At EPS Trenchless Installations, we utilise non-steerable moles in our operations. This is because these types of moles are at the forefront of the industry and are a more reliable tool to operate during your project.

Moling Tool Sizes and Specifications

  • Moles Specifications:

    • Available in diameters from approximately 45mm to 200mm, creating boreholes from 45mm to 200mm.
    • Length ranges from 89cm to 3.3m, with weights between 9 to 226kg.
    • Cycle rates typically range from 200 to 400 cycles per minute, with some models exceeding 700 cycles per minute.

Are There Any Limitations and Considerations to Impact Moling?

Despite its many advantages, impact moling has a few limitations which can be managed with thorough planning and assessment prior to any moling services being carried out.

Unfavourable Ground Conditions

Its effectiveness can be impacted by adverse ground conditions such as cobbles, dense dry clays, and other non-compatible soils. These conditions can slow down the process, cause surface disturbance, or stray from the bore path. The method is also restricted by its limited boring diameter and length.

Ground conditions should be thoroughly evaluated to ensure successful application. Traceability options help detect path deviations, allowing corrections before significant issues arise.

Distance From Nearby Utilities

Research on the safe distances for impact moling near existing utilities is still developing, but it’s generally recommended to maintain a clearance of six times the pipe diameter being installed. Moles technology performs very well in stable soils if properly aligned, achieving accuracies within 5%.

Working near underground utilities or objects requires careful planning due to potential risks. Withs impact moling, minor damage from vibrations can be caused by pneumatic hammering. Some types of pipes, such as asbestos cement pipes, are more sensitive to these effects. Selecting a knowledgeable and skilled team such as EPS Trenchless Installations, can mitigate these risks as proper planning and surveying of the area will be undertaken before the project commences.

Operator Skill

A reliable and trusted impact moling organisation will always ensure that all necessary precautions are taken to minimise any risk of damage and to comply with industry safety standards. This includes conducting thorough preliminary assessments and being trained.

Typical training consist of:

  • Understand the various moling product range (i.e. what’s available) and benefits of employing different type devices when undertaking moling operations.
  • Identify ground/soil types and changeable conditions faced on-site for specific moling operations.
  • Explore allied accessories and special interchangeable heads and cones.
  • Understand the importance of direct towing in of PVC/PE ducts and pipes.
  • Complete a discussion of a ‘typical job site’ scenario to include: incorporation of health & site safety issues, correct operating techniques of impact moling, on-site theoretical problem solving, decommissioning of equipment, troubleshooting, basic operator precaution and maintenance issues.
  • Undertake practical training sessions that includes: the correct site ‘set-up’ of a impact mole, assembly of an impact mole, and safe working practices.

Impact Moling Services: Incredible Solutions For Your Moling Project

Impact moling is a versatile and efficient method for installing small-diameter pipes and cables with minimal disruption and cost. By understanding its advantages, limitations, and the conditions in which it operates best, utility companies and contractors can effectively employ this technology for a wide range of applications. 

Proper planning, soil evaluation, and tool selection are crucial for successful impact moling projects, ensuring efficient and accurate installations. 

At EPS Trenchless Installations, we prioritise thorough site assessments and state-of-the-art equipment to adapt to various soil conditions, enabling us to handle even the most challenging projects with precision and reliability. Our commitment to quality and detail ensures that each project is completed on time, within budget, and with minimal environmental impact.

Enquire About Your Impact Moling Project Today

At EPS Trenchless Installations, we specialise in providing impact moling services and can help you with your project needs. Contact us today to learn more about how impact moling can benefit your utility installations and to get started on your project. 

Our team of experts is here to assist you every step of the way, from planning and evaluation to execution and completion. Don’t hesitate to reach out and see how our pipe moling services can work for you.