Pipe Umbrella System
Forepoling with pipe umbrella system is a pre-support measure that is employed in tunneling works in weak ground conditions to sustain loose formations, secure the upper arch and avoid roof collapses. This is achieved by drilling steel tube micropiles sub-horizontally to the contour of the tunnel section in the shape of an umbrella. Pipe umbrella system increases the stability by transferring loads in the longitudinal direction and reduce deformations due to excavations.
Forepoling using “casing advancing system” is especially suitable for tunnel construction in challenging ground conditions with high water flow, unstable fractured or cavernous rock.
Pipe umbrella system consists of external pipe casing and drill rods. External pipe casings are available in Ø76.10 to 219.10 mm and in the thickness of 6.10 to 12.7 mm. Typically, one pile consists of several steel pipes of 1.50 to 3.00 meters which are connected by thread and equipped with injection valves for grouting. Ring bit assembly consisting of ring bit and casing shoe is welded on to the first (starter) casing. Drill rods are fitted with a pilot bit which transmits the percussion energy to the ring bit.
Forepoling using “casing advancing system” is especially suitable for tunnel construction in challenging ground conditions with high water flow, unstable fractured or cavernous rock.
Pipe umbrella system consists of external pipe casing and drill rods. External pipe casings are available in Ø76.10 to 219.10 mm and in the thickness of 6.10 to 12.7 mm. Typically, one pile consists of several steel pipes of 1.50 to 3.00 meters which are connected by thread and equipped with injection valves for grouting. Ring bit assembly consisting of ring bit and casing shoe is welded on to the first (starter) casing. Drill rods are fitted with a pilot bit which transmits the percussion energy to the ring bit.
