Umbrella Steel Pipe Roofing

According to fortification literature of NATM the forepoling systems in tunnels uses to supporting top of excavation surfaces as understanding its name. According to soil conditions there are lot of types forepoling systems. As soil classes changes from weak up to strong diameters of forepoling systems changes same from small up to large also.

There are the forepolings that were applicated according to negative of soil conditions also. These forepolings that were called umbrella arch uses at especially the soils of high cohesion that are swelling and jaming. Most important particular of umbrella arch what do not use with bolt applications together and cover entire celing almost. Umbrella archs are aplicated two kinds as normal and self drilling. Normal drilling is same forepoling systems as told previously. Process of drilling and application are made together on self drilling systems. Self drilling system is made ring bits and pilot bits. Ring bits are welded end of forepiling pipe. The rods that end have pilot bits are passed inside to forepoling pipe and locked. Procces of locking are made to direction of drilling and started drilling. The rod is turned opposite direction and opened lock after drilling. Through this process the rod is pulled reverse but forepoling pipe and ring bit stays inside the hole.