Pre-Support

Using long distance fore-piles or short distance fore-poles to form an umbrella-like pipes’ roof provides the pre-support for tunnel excavation work under weak ground conditions. It has already become the standard auxiliary tunneling method in recent years.

Pre-support elements include umbrella pipe roof with longer distance, short steel tubes’ spiles, and self-drilling spiles, which are installed in front of the tunnel's longitudinal direction to prevent collapsing during excavation.

Regardless of the elements’ strength itself, strong bonding with the surrounding ground through proper injection work forms a rigid roof, which doubles the pre support effect and plays a key role in the success of the method.