◆ Classification based on methods of Tunnel
Construction
a) Cut and Cover Tunnels. These are built by
excavating a trench, constructing the concrete
structures in the trench and covering the soil. The
tunnel may be constructed in place or by using precast sections.
b) Bored or Mined Tunnels. These are built without excavating the ground. These tunnels are named
according to the material through which they pass.
c) Rock tunnels. These are excavated through the rock by drilling and blasting, by mechanized excavators in softer rocks or by using ‘Tunnel Boring Machines’ (TBMs). Sequential Excavation Method (SEM) is also used, in new tunnels these days.
d) Soft Ground Tunnel. These are excavated through soil using shield or by TBMs which balance earth pressure or by mining methods.
e) Immersed Tunnels. These are made from very large precast concrete or concrete filled steel elements that are fabricated in the dry, floated to the site, placed in prepared trench below water and connected to previous elements and then covered up with backfill.
f) Jacked Box Tunnels. Are pre-fabricated box
structure jacked horizontally through the soil using methods to reduce surface friction. Jack tunnels are used where surface must not be distributed like beneath a runway, or embankment.
No comments:
Post a Comment