Phase 2 Report
HRT Face-IV
Excavation:
The excavation of Face-IV has been successfully completed on 20th March 2017. The conventional method of Drilling and Blasting has been adopted throughout the whole stretch. Different classes of Rock have been encountered ranging from Poor to Medium Rock, which can be summarized as shown in Table 1.
|
RD(m)
|
Length (m)
|
Rock Class
|
Remarks
|
|
|
From
|
To
|
|||
|
1382.00
|
1390.50
|
8.50
|
Class-III
|
With Steel Ribs
|
|
1390.5
|
1405.25
|
14.75
|
Class-IV
|
Steel Ribs
|
|
1405.25
|
1414.25
|
9.00
|
Class-IV
|
Without Rib
|
|
1414.25
|
1416.50
|
2.25
|
Class-IV
|
Steel Ribs
|
|
1416.5
|
1419.5
|
3.00
|
Class-III
|
|
|
1419.50
|
1422.25
|
2.75
|
Class-III
|
With Steel Ribs
|
|
1422.25
|
1428.00
|
5.75
|
Class-III
|
Class-IV profile taken
|
|
1428.00
|
1436.25
|
8.25
|
Class-III
|
With Steel Ribs
|
|
1436.25
|
1460.50
|
24.25
|
Class-III
|
Class-IV profile taken
|
|
1460.50
|
1464.25
|
3.75
|
Class-III
|
With Steel Ribs
|
|
1464.25
|
1500.00
|
35.75
|
Class-III
|
Class-IV profile taken
|
|
1500.00
|
2096.00
|
596.00
|
Class-III
|
|
Table-1 Rock Classification of Face-IV
The details of the Excavation progress of Face-IV from January 2016 to March 2017 are detailed in Table-2.
|
Month
|
RD (m)
|
Length (m)
|
|
|
From
|
To
|
||
|
January-2016
|
1382
|
1404
|
22
|
|
February-2016
|
1404
|
1422.5
|
18.5
|
|
March-2016
|
1422.5
|
1456
|
33.5
|
|
April-2016
|
1456
|
1523
|
67
|
|
May-2016
|
1523
|
1574
|
51
|
|
June-2016
|
1574
|
1641.3
|
67.3
|
|
July-2016
|
1641.3
|
1700
|
58.7
|
|
August-2016
|
1700
|
1754
|
54
|
|
September-2016
|
1754
|
1796
|
42
|
|
October-2016
|
1796
|
1846
|
50
|
|
November-2016
|
1846
|
1894
|
48
|
|
December-2016
|
1894
|
1966
|
72
|
|
January-2017
|
1966
|
2019
|
53
|
|
February-2017
|
2019
|
2071
|
52
|
|
March-2017
|
2071
|
2096
|
25
|
Table-2: Details of monthly Excavation
Squeezing Zone:
Lower Class III and Class IV rock has been encountered between RD 1145 – 1422m along with consistent loose fall and cavity formation. On the recommendation of Geologist, Steel Ribs (ISMB 250) were provided for enhancing the stability of the profile. Later, in this area, due to high super incumbent cover, the presence of weak schistose rock, has resulted in squeezing condition. In several reaches, the steel ribs have deformed due to high stresses.
Total of 65 Nos. of steel ribs has been installed between RD 1382-1464m with 987.045 m3 of backfill concrete. Further, the profiles have been stabilized using channels (IS MC 100) as an umbrella and bracings.
Rib Rectification:
Upon the detailed survey of the squeezed zone, it was observed that the maximum settlement at crown was 28 cm at RD 1380m.
The invert was lowered by 50 cm at RD 1380 without disturbing the entire stretch of ribs at crown level in this zone and accordingly invert and overt lining was adjusted gradually from RD 1133 to RD 1520. The change in slopes is as shown in Table-3.
Further, the entire rib zone was evaluated for squeezing on RHS & LHS from the center line and following measures were taken at site: -
· Where ever desired dimension of 3.4 m from the center line to rib flange is less than 3.4 m on both side, remining was done on both side to achieved desired section.
· Where ever desired dimension of 3.4 m from the center line to rib flange is less than 3.4 m on one side and more than 3.4 m on opposite side, remining was avoided and the center line was adjusted to achieve the desired section.
· Where ever desired dimension of 3.4 m from the center line to rib flange is less on one side and exactly 3.4 m on opposite side, remining was be done on one side only.
|
SL. No
|
INVERT
|
|||||
|
RD (m)
|
Original Elevation
|
New Elevation
|
Original Slope
|
New Slope
|
Remarks
|
|
|
Change in Slope from RD 1133 – 1380m
|
||||||
|
1
|
1133
|
1698.84
|
1698.84
|
1 in 198.86
|
1 in 141.79
|
RD 1133-1380
New Slop 1 in 141.79
|
|
2
|
1380
|
1697.6
|
1697.10
|
|||
|
Change in Slope from RD 1380 – 1520m
|
||||||
|
3
|
1380
|
1697.6
|
1697.10
|
1 in 198.86
|
1 in 686.27
|
RD 1380-1520
New Slope 1 in 686.27
|
|
4
|
1520
|
1696.89
|
1696.90
|
|||
Table-3: Details of Change in Slope
Overt & Invert Lining:
The overt lining of Face-IV started on 18.05.2018. A total length of 2346 m of HRT Overt lining was done from Face-IV deploying four Gantries at a peak time. The last Gantry at the Adit junction was done on 26.10.2018. The details of the monthly progress of Overt Lining can be figured out from Table-4. Two Hydraulic kerb shutters (6 m each) was deployed for improving the progress of the Kerb concreting. Modified kerb shuttering was adopted along with modified Gantry for minimizing the joints (joints between kerb and gantry).
Invert concreting of 2319 m was started on 06.02.2018 and successfully completed on 12.11.2018 with the concreting of Adit Junction. Initially, Invert Scatter was used for Invert concreting which was later stopped due to slow progress. Manually, using the Invert Template was adopted for Invert Concreting. The monthly progress of Invert concrete was tabulated in Table-5.
|
SL. No
|
Month
|
Length (m)
|
Remarks
|
SL. No
|
Month
|
Length (m)
|
Remarks
|
|
|
|
|
|
||||
|
1
|
May-17
|
46.4
|
|
1
|
Feb-18
|
439
|
|
|
2
|
Jun-17
|
117.7
|
|
2
|
Mar-18
|
185
|
|
|
3
|
Jul-17
|
14.8
|
|
3
|
Apr-18
|
226
|
|
|
4
|
Sep-17
|
28
|
|
4
|
Sep-18
|
423
|
|
|
5
|
Oct-17
|
148
|
|
5
|
Oct-18
|
1016
|
|
|
6
|
Nov-17
|
102.5
|
|
6
|
Nov-18
|
30
|
|
|
|
|
|
|
Table-6: Details of Invert Lining
|
|||
|
7
|
Dec-17
|
211
|
|
||||
|
8
|
Jan-18
|
206.5
|
|
||||
|
9
|
Feb-18
|
59.4
|
|
||||
|
10
|
Mar-18
|
309.9
|
|
||||
|
11
|
Apr-18
|
88.8
|
|
||||
|
12
|
May-18
|
150
|
|
||||
|
13
|
Jun-18
|
426.9
|
|
||||
|
14
|
Jul-18
|
114
|
|
||||
|
15
|
Aug-18
|
103.6
|
|
||||
|
16
|
Sep-18
|
189.9
|
|
||||
|
17
|
Oct-18
|
28.6
|
|
||||
Table-4: Overt Lining Details
RCC Lining:
RCC lining was provided for 255 m stretch between RD 1145 to 1400 m. Double layer of reinforcements was provided with 25 mm dia @ 200 c/c as a main bar and 16 mm dia @ 200 c/c as distribution bar.
PS: Mailed to EE sir for further correction and necessary action.
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