Rohtang Tunnel
Monday, 10 July 2017
Saturday, 8 July 2017
Monday, 22 May 2017
3.8 Tunnel Final Lining
•The final lining of the tunnel is made of
M35A20 grade Reinforced Concrete with addition of polypropylene fibre (C3H6)n.
•Experiments revealed that Polypropylene fibre reinforced concrete maintains its compressive strength at high temperatures also. The PP fibre reinforced concrete thus will not fail during fire outbreak inside the tunnel.
•The quantity of PP fibre is maintained 3kg per m3 of concrete.
•Experiments revealed that Polypropylene fibre reinforced concrete maintains its compressive strength at high temperatures also. The PP fibre reinforced concrete thus will not fail during fire outbreak inside the tunnel.
•The quantity of PP fibre is maintained 3kg per m3 of concrete.
Polypropylene Fibre |
3.7 Insertion of Rock bolts
•A Rock Bolt is a long Anchor bolt for
stabilising rock excavations. A rock bolt transfers the load from unstable
exterior to confined interior of rock mass.
•Two types of Rock Bolts are used in Rohtang Tunnel:
•Two types of Rock Bolts are used in Rohtang Tunnel:
1) Swellex Mn24
As
the name suggests, Swellex swells when water pressure is applied at its opening. It anchors large
broken Rocks.
2) Injection Bolt
Injection bolt is a hollow steel tube of 35mm dia
provided with holes
of diameter 5mm throughout its length. When cement is grouted through
Injection bolt, the grout is released from these holes are broken pieces
of
are bound together.
3.6 Secondary Shotcrete
•After installation of lattice girders,
M40A10 grade concrete Reinforced with steel fibre is sprayed over the lattice
girders to a thickness at which lattice girders are completely covered.
•Steel Fibre provide strength and
flexibility to the shotcrete.
•The quantity of steel fibre is kept 35kg
per m3 of concrete.
•Length of fibre = 35mm
•Diameter of fibre = 0.54mm
3.5 Lattice Girder Installation
- Lattice girders are the supporting elements in tunnels and they normally consists of steel bars laced together in a triangular pattern.
- They are made to suit the shape of the tunnel.
- The main purpose of lattice girders is to provide temporary support to the rock which may fall readily.
- The secondary purpose of lattice girders is to provide an indication if sufficient thickness of shotcrete is applied.
- They also help in resisting tunnel deformations during rock bursts.
- Lattice girders are not used in case of Rock Class 1, 2 and 3.
Friday, 16 September 2016
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