PPT CAVITY Tunnel P1

1. SIVOK – RANGPO NEW B.G. RAIL LINE PROJECT
Tunnel T1 & T2
IRCON INTERNATIONAL LIMITED
THE INFRASTRUCTURE COMPANY

2. Contract Details
Agency M/s. GAMMON
Date of Award 21.08.2019
Completion Period 27 Months
Date of completion 21.11.2021
Contract value Rs. 595.86 cr.
Item Scope
(m)
Excavation Progress
(m)
Lining Progress (m)
Main Tunnel T1 4204 299.6 0.00
Main Tunnel T2 902 120.90 0.00
ADIT Tunnel 800 0.00 0.00
Approach road for
ADIT
320 0.00 0.00
Total
(T1+T2+ADIT)(m)
5906 420.50 0.00
Financial 595.86 Cr. 34.43 Cr
Main Tunnel (L – 4204 m)
2979m
800m
1225m
Gammon Scope
1 in 80
Main tunnel L=902m
T1P2
T1P1
T2P1 T2 P2
290.10
NH-10
Approach road of 320m
length to ADIT Portal
TUNNEL T1 & T2
120.90
Progress of Tunnel T-1 & T-2
9.5

3. Manpower & Machinery Tunnel no 1 & 2
SN DESIGNATION TO BE DEPLOYED
( As per available
front/face)
DEPLOYED SHORTFALL
1 Project Manager 1 1 0
2 Works Manager 1 1 0
3 QSS Engineer 1 1 0
4 Quality Manager 1 1 0
5 Safety Manager 1 2 0
6 Site Engineer 4 4 0
7 Geologist 1 1 0
8 Surveyor 2 2 0
9 Shift Engineer 6 6 0
10 NATM Foreman 6 6 0
Deployment of key personnel

4. SN Type of Plants/Equipment TO BE
DEPLOYED
( As per
available
front/face)
Deployed. shortfall Remarks
1 Hydraulic drill jumbo and
basket
4 4 0
2 Sprayed concrete pump 4 4 0
3 Tunnel excavator with
swiveling
3 3 0 Balance will be deployed as the
faces open and during the
execution of concrete lining of
Tunnel
4 Pay loader 3 3 0
5 Transit Mixers 10 6 4
6 Dumper (low profile) 16 16 0 All locally hired
7 Batching Plants 2 2 0
8 Mai Pump 4 5 0

5. SN Type of Plants/Equipment TO BE
DEPLOYED
( As per
available
front/face)
Deployed. shortfall Remarks
9 Rotor sprayed concrete 2 2 0
10 Working platform with swiveling
basket
4 0 4 Related activities being carried out
by Drill Jumbo basket
11 Excavator 3 3 0
12 Dozer 2 1 1 After handover of Adit
13 Fork lift 1 0 1 After handover of Adit
14 Trailers 2 2 0 All locally hired
15 Concrete pump 6 2 4 Remaining concrete pump will be
deployed as per requirement
16 Stone Crusher Plant 1 0 1 After handover of D.I land
17 Crane 1 1 0
18 Explosive Van 4 4 0 Hired from explosive supplier
19 DG Set 4 7 0 Capacity= 380,365,125x3, 30 & 3 KVA
20 Compactor 1 1 0
21 Mobile concrete mixer low 12 2 10 2 nos B/P set up at each tunnel site

6. Cavity formation in T1/P1
SIVOK-RANGPO RAIL LINK PROJECT

7. Introduction-
>Tunnel T1 is a part of Sivok to Rangpo BG Tunnel Project and being
constructed between Sivok Railway Station and Andheri Jhora with a total length
of approx. 4202 meter.
>The south portal of Tunnel T1 (hereby designated as T1P1) is being excavated
by NATM method. A total of 291.3 m from chainage 321.0 m to 612.3 m
(approx.) has been already excavated.

8. Anticipated Geological L-Section of The
Relevant Part

9. Tunnel (T1/P1 drive) Face at CH 610.8 m (Apx.) before Cavity Formation
There was no indication of presence of any
shear zone or shale layer at the face and the
face shows only Sandstone which was
medium grained, light gray colored,
generally dry to damp (LHS) in water
condition. The face log of 610.8 m also
attached with this report. The rock class
depicted at 610.8 m was Adv. Class IV. Pic-
1, (RMR=43)

10. Face log of CH 610.8 m

11. 3D Log of Tunnel T1P1

12. Tunnel (T1/P1 drive) before Cavity Formation

13. The cavity material was also
examined and it was found
weak to very weak & sheared &
highly weathered. Two pictures
of collapse material are given
for reference.
Collapse Material

14. Cavity formed after initial collapse

15. Initial Treatment
• Cavity formation started during further excavation from CH-610.8 due to sudden
encounter of shear zone. Sealing shotcrete (SFRS) was used as first control measure but
collapse could not controlled and further collapse continued.

16. Cavity increased up to CH. 608.6 m

17. • Collapse further continued after
first control measure, leading to
increase of cavity upwards and
backwards damaging the LG at
610.1m.
LG Damaged at
610.1m
Fore poles
damaged
Pic-3: LG at 610.1 m got damaged and all forepoles damaged

18. Cavity increased up to 607.5 m

19. Seeing that cavity may further extend
and immediate control is required, it
was decided to fill the face by the
muck and seal the same by shotcrete
for further treatment. By the time the
muck filling at face could be
completed, the cavity extended up to
606.8 m (approx.) after damage of LG
shotcrete & wire mesh.
Pic-4: LG at 608.6 m got damaged and all forepoles damaged

20. Cavity increased up to 606.8 m

21. Muck Filling at Face

22. In Surface visit,
a ditch was
found above
Cavity portion.
Therefore, it is
up to approx 34
m.
Possible extent of Cavity

23. Surface visit at the top of the cavity area.
Video of Ditch found at surface above cavity

24. Tunnel face filled with muck till 606.0 m. Drilling done to insert pipe to pour
concrete into the cavity.
Remedial Measures (1/13)

25. • Backfilling and grouting in progress
Remedial Measures (2/13)

26. Pipe roofing is being done
after concrete filling by 76
mm dia SDR.
Remedial Measures (3/13)

27. After Pipe roofing temporary rib has been installed at 606.8 m to support the pipe roofing.
Remedial Measures (4/13)

28. Second temporary rib
installed at 607.3 m.
Remedial Measures (5/13)

29. Collapse occurred from right side at 607.5 (approx.) while removing the
muck sealing to make space for third rib.
Remedial Measures (6/13)
VIDEO OF COLLAPSE FROM RIGHT SIDE

30. After collapse from right side
tunnel face packed with muck.
Grouting and backfilling done
by installing 105 mm holes.
Remedial Measures (7/13)

31. After grouting and
backfilling muck removal
done sequentially for
heading part only and
ISHB 150 ribs being
installed (starting from left
side of the tunnel) up to
612.0 m.
Remedial Measures (8/13)

32. After installation of ribs at
left side right side part of
the ribs being installed.
Remedial Measures (9/13)

33. Collapse occurred from
the right side again while
installation of permanent
ribs in right side was
going on.
Remedial Measures (10/13)

34. Tunnel sealed by muck
after collapse and the
installed ribs supported by
extra ISHB.
Remedial Measures (11/13)

35. • SDA 32mm dia installed
along the periphery of the
installed ribs at 610.0 m
and grouted.
Remedial Measures (12/13)

36. After grouting of SDA
sequential muck removal was
done at the right side of the
tunnel and Side Arch part of
the ribs installed one at a time
up to 612.0 m.
Remedial Measures (13/13)

37. Surface above
the cavity
portion was
traced with the
help of hand
GPS. A ditch
was formed
there which
was approx.
7m X 7m in
horizontal
dimensions &
3-5 m deep.
Effect of Cavity on Surface (1/2)
Weathered and sheared rock mass exposed at one
side of the ditch formed at the surface due to cavity

38. Monitoring
section at CH
598m & CH.
605.2m showing
deformation
within the safe
limit.
3D MONITORING at CH. 598m & CH. 605.2 m
CH 598 m
CH 605.2 m

39. • Due to unexpected shear zone the collapse occurred during excavation from CH 610.8 onwards.
Such shears are a common feature in Himalayan geology and exact location & extent is difficult
to map due to lack of outcrops & thick forest cover.
• The overburden cover of this area was determined from L-Section as 34.0 m.
• Tunnel T1 and T2 passes through Mahananda Wild Life Sanctuary in which there are certain
restrictions on free movement for surveying/investigation etc. Hand inspection of collapse
material and by surface visit, a Shear Zone is interpreted as shown in the schematic diagram and
surface photos shown below. This shear zone is considered as main cause of the cavity
formation. The orientation and extent of shear zone can be different from that shown in the
diagram.
Conclusion