Brig DN Bhatt

Chief Engineer

TUNNEL PROPER

            This tunnel project was conceived way back in1983 in view of the need to provide an all weather route to Leh and Lahaul & Spiti valley in Himachal Pradesh. Rohtang pass, located 51 km away from Manali, is at an altitude of 3978.0 m (13044 ft) and has been posing serious problem in maintaining the road communication for more than four months in a year. It faces heavy snow fall activity, high velocity winds and sub-zero temperature. Accordingly, feasibility study for the construction of tunnel across Rohtang pass conducted by M/S RITES. Detail Project Report (DPR) has been submitted for obtaining formal approval from cabinet committee on security. Formal approval for the project is yet awaited. Salient features of the proposed Rohtang Tunnel are given as under: -

 

Length of Tunnel

:

8.802 km

Shape of Tunnel

:

Horse Shoe shape.  Finished width 10.00 m at road level. (8.00 m pavement and 1.00 m footpath on both the sides)

General altitude of the tunnel

:

It lies between 3000-3100 m altitude

Design speed

:

80 km/h

 

Geology of Tunneling media

:

Uniformally dipping alternate sequence of  Quartzites, Quartzitc Schists, Quartz-Diolite-Schist with thin bands.

Temperature variation in the area

:

25-300 C during May-June

 

-200 C to -20 C during Dec-Jan

Overburden

:

Maximum-1900 m

 

Average more than 600 m

Construction technique proposed

:

Drill & Blast with NATM

Support System proposed

:

Fibre reinforced concrete (100 to 300 mm thick) combined  with rock bolt (26.50mm dia 5000 mm to 9000 mm long) has been proposed as principal support system.  In poor rock condition yieldable steel ribs (ISMB 150/ISMB 300) have been proposed in addition.

Tunnel ventilation

:

Semi transverse system of ventilation system has been proposed.  Following parameters have been taken in design:-

 

 

(a)

Upper tolerance limit for  concentration

-

150ppm

 

 

(b)

Visibility factor

-

0.009/m

 

 

 

(i)

Cars

-

3000 Nos

 

 

 

(ii)

Trucks

-

1500 Nos

 

 

(d)

Peak hour traffic

-

337.50 PCUs

 

 

(e)

Design vehicular speed in Tunnel

 

 

 

 

 

(i)

Maximum Speed

-

80 km/ph

 

 

 

(ii)

Minimum Speed

-

30 km/ph

Project Cost

 

Approximately Rs. 1458 Crore


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