Pipe Jacking vs Directional Drilling

Pipe jacking and directional drilling are distinct trenchless methods used for installing underground utilities with minimal surface disruption. Both techniques allow pipelines to be installed without open trenches, but they differ significantly in their execution and application.

While both methods provide trenchless solutions for utility installation projects, choosing between pipe jacking and directional drilling depends on factors such as pipe material, installation distance, and alignment requirements. By understanding their differences, this ensures the right technique is selected for your specific project needs based on suitability.

The following blog examines the key pipe jacking vs directional drilling differences. We also examine and emphasise the benefits of using either one of these trenchless techniques to install utility service lines when compared with traditional, open-cut trenching methods.

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Key Pipe Jacking vs Directional Drilling Differences

There are various key differences between these two trenchless methods when it comes to execution, application, and suitability. The following comparative analysis between pipe jacking vs directional drilling will help you to understand what’s needed for your installation project.

Pipe Jacking

Pipe jacking is a trenchless method where prefabricated pipes are hydraulically pushed through the ground from a launch shaft while an excavation head removes soil at the front. This trenchless technique is highly precise but follows a strictly straight path, making it ideal for short-to-medium distances under roads, railways, and dense urban areas.

Method: Uses hydraulic jacks to push prefabricated pipes through the ground while an excavation head actively removes soil at the front.
Alignment: Follows a straight-line path.
Best For: Short-to-medium distances, typically up to 150 metres per drive.
Pipe Types: Reinforced concrete, steel, or ductile iron.
Common Uses: Road and rail crossings, and any other urban installations where precision and stability are required.

Limitations: Limited to straight paths, and requires a launch and reception shaft.

Directional Drilling

Directional drilling, also commonly known as horizontal directional drilling (HDD), involves drilling a pilot borehole along a predetermined, slanted, curved, or straight path. The borehole is then gradually enlarged before pulling the pipeline into place. This trenchless method is best suited for longer-distance pipework installations, particularly under highways, rivers, or environmentally sensitive areas, where flexibility in the route’s trajectory is required.

Method: Uses a drill rig to bore a pilot hole along a curved path, then enlarges the hole, referred to as reaming, before pulling in the pipeline backwards.
Alignment: Can follow a curved or variable path.
Best For: Long-distance installations, potentially running into hundreds of metres depending on factors like pipe diameter, soil conditions, and equipment capacity.
Pipe Types: High-Density Polyethylene (HDPE), steel, or PVC.
Common Uses: Highway and river crossings, or other environmentally sensitive areas, and any installation projects requiring flexibility in depth or alignment.

Limitations: Higher risk of deviation from the pre-planned path, and not ideal for large-diameter rigid pipes which cannot flex to follow the drilled bore path.

Comparative Summary: Pipe Jacking vs Directional Drilling

In summary, pipe jacking is a mechanical excavation process where pipes are pushed forward using hydraulic jacks, while directional drilling is a borehole drilling process that creates a curved or straight path before pulling the pipe through. In short, pipe jacking is a pipe-pushing method, while directional drilling is a boring-and-pulling method. These two trenchless techniques serve similar purposes but with different methods, capabilities, and limitations.

While both techniques minimise surface disruption, pipe jacking is best for straight, controlled installations of rigid pipes, whereas directional drilling is ideal for long-distance, flexible routing beneath obstacles like roads, railways, and any other surface infrastructure.

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The Benefits of Trenchless vs Traditional Methods

When it comes to choosing trenchless methods over traditional open-cut trenching, there are several advantages — making both pipe jacking and directional drilling preferable solutions for installing service lines for water, gas, sewers, electricity and telecoms networks.

The key benefits of these two trenchless techniques include:

Reduced Surface Impact: Both techniques enable underground installation with minimal excavation, reducing disruption to roads, landscapes, and infrastructure.
Eco-Friendly Solutions: By disturbing less soil, these methods help prevent erosion and minimise harm to ecosystems, making them ideal for installations near rivers, wetlands, and other sensitive environments.
Lower Overall Costs: Although the initial setup cost may be higher, these methods lower expenses related to road closures, traffic management, and land restoration. They also require significantly less manual labour compared to open-cut trenching.
Quicker Project Completion: These techniques allow for faster installation than conventional trenching, enabling pipes to be laid beneath obstacles like roads and buildings without requiring demolition or reconstruction.
Broad Applicability: Unlike traditional trenching, trenchless methods are adaptable to various soil types, including rocky and clay-heavy conditions, making them suited for crossings under roads, rivers, railways, and densely built urban areas.
Enhanced Pipe Longevity: Pipes installed using pipe jacking or directional drilling are typically deeper and shielded from surface elements, reducing exposure to damage and extending their lifespan. This increased durability results in long-term cost savings.
Improved Safety Standards: Trenchless techniques significantly lower risks associated with open-cut trenching, such as worker injuries and public safety hazards.

Overall, trenchless methods offer more efficient, cost-effective, and eco-friendly alternatives to traditional trenching, especially in urban and environmentally sensitive areas. These methods are also much safer for everyone involved, reducing liabilities and costs all round.

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The Cost of Pipe Jacking vs Directional Drilling

So having established that both pipe jacking and directional drilling as trenchless installation methods are far more cost-effective than traditional open-cut trenching, how do these two techniques compare cost-wise to each other? A cost comparison depends on several factors, including pipe size, soil conditions, installation length, and project complexity.

Here’s a breakdown of the main cost drivers:

1. Pipe Diameter & Material

Pipe jacking is typically used for large-diameter, rigid pipes which are more expensive to manufacture and install.
Directional drilling is more cost-effective for smaller-diameter, flexible pipes which are generally lighter and cheaper.

2. Soil & Ground Conditions

Both methods perform well in stable soil such as clay, silt, and firm sand, although directional drilling is often cheaper.
Pipe jacking is often more reliable for hard rock or unstable ground, such as loose sand or gravel, but more expensive due to tunnelling requirements. Still, drilling fluid and borehole management using directional drilling in challenging soils can add to costs.

3. Installation Length

Pipe jacking can be more cost-effective for short-to-medium distances (up to ~150m) because of its accuracy and strong pipe durability.
Directional drilling is generally cheaper for longer distances (200m+) because it avoids the need for multiple shafts and allows for continuous pipe installation.

4. Site Access & Space Requirements

Pipe jacking needs launch and reception shafts, which can increase costs in urban areas or restricted sites.
Directional drilling only requires a drill rig and pullback area, making it cheaper where space for a project is limited.

5. Precision & Alignment Control

Pipe jacking provides higher precision, making it ideal for installations requiring exact alignment, although this adds to cost due to specialised tunnelling equipment.
Directional drilling offers flexibility but there is a risk of borehole deviations, which may require more correction work.

6. Equipment & Labour Costs

Pipe jacking requires hydraulic jacks, tunnel boring machines, and reinforced shafts, increasing overall setup costs.
Directional drilling typically involves a drill rig, reaming tools, and drilling fluid management, often making it more cost-effective for longer distances.

7. Surface Disruption & Restoration

Pipe jacking requires launch and reception shafts, which can increase excavation and restoration costs.
Directional drilling causes minimal surface disruption, reducing road closures, traffic control, and restoration expenses, representing a major cost advantage in urban areas.