Forepoling Ring
Bit System
(Tube Umbrella)

Casing size 76–219 mm

Forepoling ring bit system and casing tubes are designed to be drilled with top hammer or DTH in an umbrella shape as secondary support in the tunnel roof. Weak ground and overburden must be strengthened by grouting through the casing and grouting valves into the ground.


Main applications

The system is available from 76 to 219 mm casings and for all major DTH shanks and top hammer threads.

Download the pdf data sheet for detailed information and measurements.

Use with
tunneling projects

Forepoling is used to strengthen tunnel roofs in soft or caving ground before excavation. Forepoling casings are drilled nearly horizontally into an arc formation and filled with grout that also spreads into the ground through the casing’s grouting valves. These supporting bars then hold the tunnel roof in place, making further excavation safe.


The system is available from 76 to 219 mm casings and for all major DTH shanks and top hammer threads.

Threaded casings normally come with 1 start but they are also available with 2–3 start trapezoidal threads and 10 mm entrance.

Steel Casings

Steel casings are the most used casing option. Their main features are:

GFRP casings

Glass fiber reinforced polymer casings are a special type of casings that are used in face stabilization. Their main features are:

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All Mincon casing systems are made with passion to drilling.
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Mincon Group plc is a global engineering business specialising in the design, development, manufacture, and service of rock drilling tools for a variety of applications.

Originally founded in 1977 in Shannon, Ireland, it now has a worldwide presence, with customer service centres and factories across the Americas; Europe and Middle East; Africa, and Asia Pacific. 


Mincon Group plc- The Driller's Choice ™


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