Page 53 - ENGINEERING

3.1.31. Improvement of Marugutti Tunnel :

It is a D-shaped tunnel of diameter 4.92 m at the face and height of
6.70 m at crown level (from RL). The length of the tunnel is 1.645 km, out
of which 200 m length Gulbarga end and 25 m towards BIDR end with
cut and cover method. The tunnel has been lined for the length of 1200
m and balance 400m is unlined portion. The maximum over burden
available is 25m. The tunnel approaches towards Gulbarga end are

made with five benches and normal cutting of 9-10m at BIDR end. The
catch water drain has been provided at the bottom bench for
Gulbarga end.

REASON FOR THE COLLAPSE OF THE FACE WALL GULBARGA END AND
FALLING OF BOULDERS FROM CUTTING BIDR END

(i) Gulbarga end: while making the cut and cover portion the
cutting made is much lower than normal hillock. The catch
water provided with CC walls only upto the centre of the

tunnel balance portion up to disposable point was not done,
this resulted in stagnation of water in the entire 200 m length
and suddenly gushed the face wall which is build with normal
stone masonry wall and entire masonry of 10m length along
with boulders, filled material laying over cut and cover portion
came on to the track.

(ii) BIDR end: The catch water drains provided are become
defunct the rain water entered into the cutting and the
weathered rock and some portion of the slopes which are with
normal earth fallen on to the track. The retaining wall
constructed was sunk for a length of 10 m.
PERMANENT MEASURES TAKEN
Gulbarga end:

(i) Provided pucca catch water drain with RCC for a length of 120 mts.
The existing soil heap is removed and widened on both sides of
LHS&RHS to prevent the slippage of earth into drain due to heavy
rain
(ii) Jacketing of face and parapet wall with RCC in integrating with
tunnel at Gulbarga end.

Before