Heading and benching in tunneling involves division of excavation section in to upper and/or middle and lower steps. The upper step is called heading and the lower step is called benching.
Around 100 to 120 holes are drilled with wedge cut pattern using two arms drilling Jumbo on the heading face.
Post drilling, face charging using electric detonator and non-electric detonator is undertaken at specific reaches.
Bench charging is carried out in a controlled manner with 30-40 detonators.
After stemming of holes, the cartridges are connected in series before blasting.
Post blasting, the muck is removed and disposed off to designated Muck dumping sites at both the tunnel drives using loaders and dumpers.
Lattice girders are supporting elements in tunnels and they normally consist of steel bars laced together in triangular patterns to suit the shape of the tunnel. They are not expected to contribute much to the overall support of the tunnel.
Rock bolt is a long anchor bolt used for stabilization of rock excavations, by transferring the load from the unstable exterior to the confined interiors of the rock mass.
Concrete is sprayed while being conveyed through hose and pneumatically projected at high velocity on to the tunnel face, typically reinforced by conventional steel rods, steel mesh or fibre, to prevent further movement of rock.
Emergency exits must allow the road users to abandon the tunnel afoot and reach a safe place in case of accident or fire.
Precast concrete element casted in yard has been used for the panels of egress tunnel.
Kicker is a structure like column, wall or curved structure which acts as the foundation for the arch lining. While it is raised, water proof dimpled membrane is also fixed between the primary and the final kicker lining.
Final lining is the most important stage of construction of a tunnel. It represents the final reinforcement which determines the strength and durability of the underground works, as well as being supports for the service installations like ventilation and lighting.
A provision is made in the tunnel to allow air ventilation and removal of smoke from vehicles from out of the main tube by creating a passage above the ventilation duct slab above the carriageway.
State of the art semi-transverse ventilation system powered by three axial fans of 630 KW is installed at each portal. The firefighting, illumination and monitoring system is based on Supervisory Controlled and Data Acquisition (SCADA).
All equipment used in the electrical and mechanical systems have been selected based on their performance in the high altitude areas.
DLC or dry lean concrete is an important part of modern rigid pavement. It is a smooth concrete with large proportion of aggregate in relation to cement than conventional concrete and is generally used for base/sub-base course for hard paving.
A superior performance concrete laid over the underlying course of rigid pavement is called Pavement Quality Concrete (PQC).