What is “forepoling”?
A method of advancing a mine working or tunnel in loose, caving, or watery ground, such as quicksand, by driving sharp-pointed poles, timbers, sections of steel, or slabs into the ground ahead of, or simultaneously with, the excavating; a method of supporting a very weak roof.
Generally, urban tunnels are subject to severe excavation conditions e.g. in unconsolidated sandy layers, with a thin earth cover, right under existing structures and near underground structures. Under such difficult conditions, and in accordance with NATM (New Austrian Tunnelling Method), forepoling has been introduced as one of the most cost-effective auxiliary methods.
Forepoling has been frequently used to stabilize the ground around the cutting face, and to control the settlement of ground surface.
Steel tubes (spiles) are installed in an umbrella shape and then injected to form a protective arch that is further supported with steel arches.
LTM Forepoling system allows the steel tubes to be simultaneously drilled in the cutting face with an additional time and cost reduction of the project.
LTM supply the complete set of equipment to all those companies needing to drill umbrella tubes with the forepoling method.
Our tubes range is from 76 mm to 219,1 mm with wall thickness from 6.1 mm to 12.7 mm.
According to customer requirements, we can provide tubes with right or left hand thread, and with one, two or three starts threads. (Read threads article here for details)
|Type of tube||End 1||End 2||Thread type||Accessories|
|Starter Pipe||Reamer set welding||Pin or Box Thread||1, 2 or 3 starts||Drilled holes or injection valves|
|Extention pipe||Pin thread||Box thread|
|End pipe||Pin or Box Thread||Straigth cut|