Tubos Paraguas - Obras Subterráneas



Tube umbrella, also known as forepoling, are mainly used in underground works, both in mining and civil works for tunnel mouths.

This underpinning element is designed to be used in poor quality soils and rocky masses, thereby delivering terrain consistency immediately.

Rotation and percussion is applied to the RING BIT via the PILOT BIT, leaving the CASING SHOE, which is welded to the starting casing, free. This enables the casing to not rotate, and therefore the torque requirements in the rotating head are much lower.

Tubos Paraguas - Obras Subterráneas

Ring bit welding in our workshop

Tubos Paraguas - Obras Subterráneas

Installation of tube umbrella in Santiago de Chile Underground L-3


BRAXIMA forepoling system is made up of high quality steel tubes that range from OD 76.1 mm to OD 139.7 mm with WT ranging from 5.6 to 10 mmOur RING BITS and PILOT BITS are designed to optimize drilling performance.

The tubes are supplied in custom lengths with normal or double-entry threads to reduce installation time and with 8 mm guide entry to facilitate correct alignment in the assembly process.

Injection Valves

The tubes may be equipped with 12 mm or 16 mm injection valves for opening pressures of 3 bar and 5 bar respectively.

Cement Grout

Cement grout is generally used to fill the space between the tubes and soil.

A lid is used in the end tube and the filler is applied using the grout. Some clients use tubes with one-way injection valves for higher pressure injections and therefore improve filler quality. Consequently, a better soil reinforcement is achieved.

Technical table

Steel Grades

Steel degree Yield point Tensile strength Elongation
min. N/mm2 N/mm2 min. %
S355 355 490-630 22
MP-80 552-752 689 18

Technical table


Braxima Code Max. Wall Thickness
BXA76.1 7
BXA88.9 8
BXA101.6 10
BXA114.3 8
BXA139.7 10
Tubos Paraguas - Obras Subterráneas

BXA76.1 – BXA88.9 – BXA101.6 – BXA114.3 – BXA139.7

System Casing O.D. W.T Max. Ring Bit I.D. Ring Bit I.D. Ring Bit O.D. Thread Grade
BXA76,1/8 76,1 8 47 90 59 R32 S355/N80
BXA88,9/8 88,9 8 50,8 94,9 70 C38 S355/N80
BXA101,6/10 101,6 10 65 110 79 C38 S355/N80
BXA114,3/10 114,3 10 73,5 120 92,5 C38 S355/N80
BXA139,7/10 139,7 10 94 145,7 117,5 C45 S355/N80
Tubos Paraguas - Obras Subterráneas

Starter tube, Extension tube, End tube

Tubos Paraguas - Obras Subterráneas

Starter tube, Extension tube, End tube

Tubos Paraguas - Obras Subterráneas

Ring bit, Starter tube, Pilot Bit