Direct Pipe – Legacy Microtunelling

Direct Pipe

The Game-Changing Approach to Pipeline Installation

Direct Pipe® technology is a breakthrough in the field of pipeline installation that ingeniously combines the strengths of microtunnelling and horizontal directional drilling technology (HDD).

This one-step technology operates in a multitude of geological terrains from soft to heterogeneous soils, and even solid rock, and is designed to handle pipe diameters ranging between 0.8 and 1.5m (30-60").

In an efficient and economical manner, this innovation enables the simultaneous installation of a prefabricated pipeline and creation of the required borehole. This method permits the rapid and cost-effective laying of pipelines exceeding 1,500 meters in length.

Seamlessly Integrating Two Technologies for Enhanced Performance

Direct Pipe® technology integrates two technologies in a seamless manner:

Soil Excavation

The process begins with the removal of soil from the starting pit utilizing a liquid-supported microtunnelling machine. This machine effectively transports the overburden via a conveyor circuit within the prefabricated pipeline above ground, directing it to a separation plant.

Pipeline Installation

Concurrently with the drilling, the pipeline, which is assembled above ground on roller blocks and welded to the machine, is impelled into the drilled hole. A pipe thruster delivers the required propulsion force, pushing the microtunnelling machine along with the pipeline with a thrust of up to 750 tons in strokes of 5 meters.

The working face can be monitored consistently and reliably, even in diverse, water-permeable soils. Uphill and downhill gradients, as well as precise cornering during the route, are feasible, thanks to a gyro-based navigation system.

An Overview of the Working Mechanism of Direct Pipe

Direct Pipe® system operates in a logical, methodical sequence:

Soil is excavated by the AVN machine’s specialized tools.

The front of the excavation is supported hydraulically via liquid suspension.

The overburden is moved through a hydraulic pumping circuit via lines laid within the pipeline.

The Pipe Thruster pushes the AVN machine along the pipeline.

Finally, the pipeline is installed in the tunnel created.

Achieving Maximum Efficiency with Minimum Space

Despite its comprehensive process, the Direct Pipe® method is notably space-efficient at both starting and end points. Its compact nature allows for operation in populated residential areas where space is at a premium. It requires only simple, close-to-the-surface starting and target excavations, negating the need for constructing deep shafts. After the completion of the drive, the microtunnelling machine is retrieved in segments of approximately 3 meters. Finally, supply and disposal lines are extricated from the installed pipeline, marking the completion of the project.

Optimizing Logistics through One-Sided Operation

The Direct Pipe system’s entire tunneling infrastructure, including the prefabricated pipeline, is situated on one side of the obstacle being crossed. This design greatly reduces the logistical effort and space requirements at the destination.

This technology is particularly suited for creating sea outfalls or landfalls. The pipeline is thrust directly from the mainland towards a sea or lake. Once the necessary length is reached, the machine is retrieved in the water, completing the process.