Environmental Management Plan – Construction Methodology Hirong H.E. Project, Arunachal Pradesh 16-1 CISMHE 16 CONSTRUCTION METHODOLOGY 16.1 INTRODUCTION Hirong Hydro Electric Project is located on river Siyom in West Siang district of Arunachal Pradesh. The Project envisages construction of a concrete gravity dam 133.5 m high, a 9.2 km long Head Race Tunnel, a 15 m diameter Surge Shaft, two underground pressure shaft bifurcating into four near an underground Powerhouse to generate 500 MW. Considering the seasonal variation, the working season of seven months starting from mid October to mid May every year has been considered while preparing the construction programme especially for the project works in the open. Underground works have, however, been considered as continuous even during the monsoon season though with a slow rate of progress on account of practical problems in movement of heavy machinery and vehicles carrying men and material. Construction Programme and selection of methodology with the planning for equipment has, as such, been worked out keeping above site constraints in view. The project has been planned to be commissioned in a period of six and half years (78 months) including period for completion of infrastructure development works. 16.2 COMMON EQUIPMENT For construction of this project, main common equipments are Aggregate Processing Plant, Batching Plant and Concrete cooling arrangement. These are common for all civil works. In addition to this, diesel captive power is also amongst common facility. However, this has been dealt with in Infrastructure chapter because diesel generating capacity is designed not only for civil works but also for garage and workshops etc. 16.2.1 Aggregate Processing Plant (APP) Important aspects related to setting up of an APP inter-alia include the following: i). Capacity and production schedule of aggregates; ii) Location of plant; iii) Type of Plants; iv) Location of quarry areas and method of extraction of river bed materials (RBM) or quarrying rock, as the case may be.
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Environmental Management Plan – Construction Methodology
Hirong H.E. Project, Arunachal Pradesh 16-1
CISMHE
16 CONSTRUCTION METHODOLOGY
16.1 INTRODUCTION
Hirong Hydro Electric Project is located on river Siyom in West Siang district of
Arunachal Pradesh. The Project envisages construction of a concrete gravity dam 133.5 m high, a
9.2 km long Head Race Tunnel, a 15 m diameter Surge Shaft, two underground pressure shaft
bifurcating into four near an underground Powerhouse to generate 500 MW. Considering the
seasonal variation, the working season of seven months starting from mid October to mid May
every year has been considered while preparing the construction programme especially for the
project works in the open. Underground works have, however, been considered as continuous
even during the monsoon season though with a slow rate of progress on account of practical
problems in movement of heavy machinery and vehicles carrying men and material. Construction
Programme and selection of methodology with the planning for equipment has, as such, been
worked out keeping above site constraints in view. The project has been planned to be
commissioned in a period of six and half years (78 months) including period for completion of
infrastructure development works.
16.2 COMMON EQUIPMENT
For construction of this project, main common equipments are Aggregate Processing
Plant, Batching Plant and Concrete cooling arrangement. These are common for all civil works.
In addition to this, diesel captive power is also amongst common facility. However, this has been
dealt with in Infrastructure chapter because diesel generating capacity is designed not only for
civil works but also for garage and workshops etc.
16.2.1 Aggregate Processing Plant (APP)
Important aspects related to setting up of an APP inter-alia include the following:
i). Capacity and production schedule of aggregates;
ii) Location of plant;
iii) Type of Plants;
iv) Location of quarry areas and method of extraction of river bed materials (RBM) or
quarrying rock, as the case may be.
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The total quantity of concrete to be placed is estimated to be approximately 11.39 Lac
cubic meters for Dam and Intake, 12150 cubic meter in Sitten Nallah, 1.56 Lac cubic meters for
HRT, 34763 cubic meter for Diversion Tunnel and Coffer Dams and 79274 cubic meters for
Powerhouse. For construction of this project, Aggregate Processing Plants (APP) are proposed at
three locations and Concrete Batching Plants (CBP) at six locations. From location 1 of APP
(APP-1) at dam site, aggregate shall be supplied for concreting of Dam, Sitten Nallah and Intake.
From Second location (APP-2) at Powerhouse site near MAT portal, aggregate shall be supplied
for concreting of the lining of part of HRT, Surge Shaft and Powerhouse Complex. From 3rd
location (APP-3) near diversion tunnel portal, aggregate shall be supplied for concreting of
Diversion Tunnel and concrete lining of part of HRT.
As worked out above the APP having capacities of 500 TPH on left bank located at dam
site, 100 TPH APP will be located at Powerhouse site near MAT portal and 60 TPH APP will be
located near Diversion Tunnel portal.
• FE Loader 3 cum : 5 (2 at Quarry + 3 at APP)
• Dozer (180 HP) : 5 (2 at Quarry + 3 at APP)
• Crawler drill IRCM 341 : 2 (at Quarry)
• Compressor @ 450 cfm : 2 (at Quarry)
• 20 tonne capacity dumper : 14 (6 at Quarry + 8 at APPs)
16.2.1.1 Batching Plant
Important aspects related to setting up of an Batching Plant inter-alia include the
following:
i). Capacity and production schedule of aggregates;
ii). Location of plant;
iii). Type and layout
The maximum concreting in a month for all structures as per the construction program is
86,576 cum for Location-1 and 16,000 cum for Location-2 and 10,000 cum for Location-3. The
maximum concrete requirement per month for Location-1 is 82660cum. Also about 10,000 cum
per month concrete is required for Location-3.
Three CBP’s (CBP1, CBP2, CBP3) and CBP6 will be required to match with the APP-1
and APP3. For APP-1 works, three CBP’s, (CBP-1, 2 and 6), one of 300 cum/hr, second of 30
cum/hr and third 30 cum/hr capacity will be deployed. For APP-3 works one CBP-2 of 30 cum/hr
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shall be deployed. For APP-2 works two CBP’s one 30 cum/hr (CBP-4) and second 60 cum/hr
(CBP-5) capacity CBP will be deployed. The location of the CBP’s are given here in below:-
• 300 cum/hr capacity CBP-1.
• 30 cum/hr capacity CBP-2
• 30 cum/hr capacity CBP-3
• 30 cum/hr capacity CBP-6
• 30 cum/hr capacity CBP-4
• 60 cum/hr capacity CBP-5
16.3 DIVERSION ARRANGEMENT
The Hirong HE Project envisages construction of a Concrete Gravity dam having its
anticipated deepest foundation at 1225m with top of dam at 1358.50m. Thus the height of dam
from the deepest foundation level is 133.50m. Diversion arrangement for construction of
concrete gravity Dam of Hirong HE Project comprises of:
i). A Diversion Tunnel 10.15m dia Horse-shoe (modified) shaped, concrete lined and 473m
long.
ii). An Adit D-shaped 7m diameter and 280 m long.
iii) An Upstream concrete coffer dam with top at 1251m, 65.6m long at top.
iv) A Downstream concrete coffer dam with top at 1242m, 50.4m long at top.
In view of the better geology on the right bank of river Siyom, the diversion arrangement
has been planned on the right bank. The left bank is readily accessible and to have access to right
bank, a bridge on river Siyom along with access roads will be needed. However to take up the
construction of adit and DT, the equipment will be taken on the right bank in dismantled
condition by barges and by the time the excavation has been done, the access to this bank would
be established.
16.3.1 Sequence of Construction of Diversion Arrangement
Thus the sequence of construction shall be as below :
i) Excavation of adit after establishing its portal
ii). Establishment of junction of Adit and DT such that the invert of adit at the tunnel grade is
at 1239.659 i.e. the benching level of DT.
iii) Excavation of heading of DT both towards u/s and d/s side and leaving a rock plug at
both the u/s and d/s portal ends.
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iv) Regarding of adit invert in a length of about 36m to meet the invert of DT at the junction
i.e. 1236.609 m elevation
v) Invert excavation both on upstream and downstream side.
vi) The structures at the inlet and outlet of DT to be established along with the activity 1
above during non-monsoon period after making ring bunds
vii) Overt and invert lining of DT after activity 5 above followed by grouting.
viii) Removal of u/s and d/s plugs in DT, which were left earlier.
ix) Erection of H.M. equipment.
x). Construction of plug at the junction of DT and adit (before diverting river water into the
DT)
16.3.2 Underground Excavation of 7.0 m D-shaped Adit
The excavation of 7.0 m D-shaped (finished) Adit to Diversion Tunnel would be taken up
by drill/blast method tackling full face excavation, as soon as the portal is established. The
drilling shall be done by Two-Boom Hydraulic Jumbo and removal of excavated material shall
be done by a combination of 2.5 cum side dump loader and 20 ton capacity rear dumpers. The
excavated area of 7 m, D-shaped Adit to DT is 48.67 sq m at minimum excavation line.
Assuming twenty (20) working hours in a day and twenty five (25) working days in a month, the
monthly progress of 7.0 m D-shaped Adit works out to about 85 m.
16.3.3 Junction between Adit and DT:
After the Adit excavation, construction at the junction of Adit and DT will be completed.
This will involve widening of Adit just before it joins the DT and installation of shotcrete, rock
bolts and rib supports. Adjoining the junction the section of DT shall be kept marginally wider
than the regular size of Diversion Tunnel, to adequately support the Rib-arches in the Haunches.
After the junction area of Diversion Tunnel is excavated and adequately supported, excavation of
DT in the upstream and downstream of the junction will be taken up.
16.3.4 Excavation of 10.15 m dia Modified Horse-Shoe Shaped Diversion Tunnel
The excavation of DT will be done by heading and benching. The heading will be kept
7.5m such that bottom level of heading is at 1239.659 m and benching at 3.45m. The 10.15m
diameter Modified Horse-shoe shaped Diversion Tunnel having a length of about 473m would
largely be excavated in rocks of varying quality. The excavation of DT is to be done by using
Drill and Blast method (DBM). The Diversion Tunnel will have a lining thickness of 400mm,
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accordingly the minimum excavated dia as well as excavated vertical dimension will be 10.95m
with 8.0m base width. The excavation and lining of diversion tunnel will require about 12
months as such at least one monsoon season resulting in high water levels / flows in the river
Siyom has to be faced by the under construction diversion arrangement. The drilling of holes will
be done by Two Boom Hydraulic Jumbos. Haulage of excavated material shall be done by a
combination of 2.5 cum side dump loader and 20 ton capacity rear dumpers.
16.3.5 Ventilation
At the time of excavation of tunnels, adequate provision for proper ventilation is
absolutely essential, therefore an effective ventilation arrangement has been planned during
execution of Adit and DT. It is proposed to provide two fans ZVN-1-14-110/4 in series with a
circular ventilation duct of 1.4 dia. As soon as the tunnel is through, ventilation will not be
required. Following criterion have been adopted for provision of ventilation arrangement.
16.3.6 Concrete Lining of DT
After the excavation in heading followed by benching is completed, the invert of the
Diversion Tunnel will be properly dressed and a 100mm thick layer of lean concrete (PCC M10)
shall be laid to form the level base at the requisite invert slope to be maintained in the Diversion
Tunnel in downstream. Suitable shuttering will be done and lining concrete of 400mm thick shall
then be paced at invert base and on sides, up to 2m height.
While the overt lining for the downstream reach is in progress, simultaneously the invert
laying in the upstream reach would be carried out. After the completion of overt lining on the
downstream side the shutter would be moved from downstream side to the upstream side, where
the invert would have been laid by then for the length of the reach such that it can accommodate
the shutter easily. At the time of execution of Diversion Arrangement, it is planned to set up a
Concrete Batching Plant of 30 m3/hr capacity and to cater for the requirement of Aggregate, an
Aggregate Processing Plant of 60 TPH (APP-3) shall be provided nearby CBP (CBP-2). At the
time of construction of Diversion Arrangement, an weighted average lead of about 1.2 km has
been considered from CBP-2 to the Portal of Adit to Diversion tunnel.
16.3.7 Removal of Rock Plugs
When the contact grouting on the upstream side is being carried out, rock plug on the
downstream side will be removed by excavation in heading and benching and adequately
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supported with the help of rock bolts / ribs as the case may be. Then the invert for this reach
would be laid. While the shutter for the lining in the reach occupied by the downstream rock
plug is being erected, the upstream rock plug would be removed by excavation in heading and
benching.
16.3.8 Inlet and Outlet Structures
During the time when all the above cited activities viz. excavation of Adit and DT,
establishment of Adit portal, raising of small ring dykes and concreting lining of DT are going
on, following activities will also be carried out concurrently in the sequence given below:
i). Removal of overburden material and excavation for Portals at the Inlet and Outlet ends of
DT
ii). Concreting for structure of portals at the Inlet and Outlet
iii). Raising of 4m high earthen ring dyke for the inlet structure and 3.5m high for the outlet
structure.
iv). Reinforcement and Concreting for the walls of the Box RCC structure duly fixing the first
stage embedment of gates
v). Excavation of toe wall
vi). Concreting of toe wall
vii) Reinforcement and concreting of roof of the inlet and outlet structures
viii) Laying of CC Blocks in front and on sides of inlet and outlet structures
ix). Invert of the inlet and outlet structures
x). Second stage concreting for gates in the groves etc.
xi) Lowering of gates and installation of HM equipments.
xii) Removal of earthen dykes.
16.3.9 Methodology for Erection of Main H.M. Equipment
Following shall be the typical erection sequence of Vertical fixed wheel gate
components:-
i) Erection of the first stage embedment (anchor bolts) in the blockout left in the RCC walls.
ii). Each set of guides, and seal seat arrangements shall be assembled in the respective
blockouts, secured in place by anchorages.
iii). Placement of second stage concrete in blockout
iv). Gate/Stoplog units transported in sub-assemblies by trailer and shall be assembled and
erected by suitable mobile crane
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v). Rubber seals shall be fitted with gate to make it leak proof.
vi). Suitable Hoisting arrangement shall be installed at 1262 m. for Inlet and 1253m for
Outlet.
16.3.10 Plugging of Adit
The Diversion Tunnel has to be ready for diverting the river water along with plugging of
Adit before the Earthen dykes for concreting of closure of coffer dams is taken up. At the same
time the last few activities in the diversion tunnel which are removal of rock plugs, concrete
lining of the respective reaches upstream and downstream along with contact / consolidation
grouting have to be completed prior to commencement of work on the construction of earthen
dykes. These earthen dykes would be constructed for closure of coffer dam only after the
diversion tunnel is fully ready for passing of the diverted water of the river i.e. the Diversion
Tunnel is complete in all respects and the Adit has been plugged.
16.3.11 Coffer dams
Diversion of river water shall be carried out for taking up the construction of main dam.
The upstream cofferdam shall be founded at 1234m and downstream cofferdam shall be founded
at 1231m depending upon availability of rock. The u/s and d/s coffer dams are planned to be
constructed using pumped concrete of grade M15A20/A40 and are likely to have maximum
heights of 17-18m and 09-10m, respectively. On completion of all the works related to DT,
plugging of Adit and removal of earthen dykes provided at the Inlet and Outlet structures will be
taken up so that the river water gets diverted to DT and raising of earthen dykes for the coffer
dams can be taken up.
For the closure of the coffer dams, earthen dykes would need to be constructed. From the
water availability series evolved for the Hirong HE Project it is seen that maximum 10-daily
inflows during the Jan, Feb and March months are 94.60, 125.42 and 102.34 cumecs. As such the
closure of the coffer dams has to be planned during the months from January to March.
16.4 DAM AND INTAKE
The construction methodology for the main dam mainly consists of (a) excavation of bed
up to sound rock profile (b) Treatment of shear zones, if any (c) Laying of concrete in lifts of 2.0
m thickness (d) Consolidation grouting (e) Curtain grouting (f) Drainage holes (g) Laying of
spillway bridge (h) Erection of hydro mechanical equipments.
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16.4.1 The Sequence of Construction
The quantities of main items i.e. excavation and concrete to be executed in these
structures are as below:
Dam Blocks:
1. Open excavation in gravels and boulders 1,19,733 m3
2. Rock excavation 1,74,003 m3
Trajectory impact pit
1. Open excavation in gravels and boulders 1,02,114 m3
2. Rock excavation 1,06,652 m3
Left Bank excavation between dam blocks and trajectory impact pit
1. Open excavation in gravels and boulders 88,985 m3
2. Rock excavation 1,04,461 m3
Excavation for Road between dam blocks and trajectory pit on left and right bank
1. Open excavation in gravels and boulders 30,402 m3
2. Rock excavation 36,074 m3
Total quantities of excavation in dam blocks are as below:
1. Open excavation in gravels and boulders 3,41,235 m3
2. Rock excavation 4,21,191 m3
Total quantities of excavation in intake structure are as below:
1. Open excavation in gravels and boulders 3,762 m3
2. Rock excavation 11,964 m3
Total quantities of concrete are as below:
(1) (a) In Dam Blocks 11,16,093 m3
(b) In CC Blocks d/s of dam 1,300 m3
Total 11,17,393 m3
Total quantity of concrete in intake 20,277 m3
The civil works for Main Dam and Intake are planned to be executed in five working seasons.
i) First Working Season (16th Oct 2012 to 15
th May 2013)
ii) Second Working Season (16th Oct 2013 to 15
th May 2014)
iv) Third Working Season (16th Oct 2014 to 15
th May 2015)
iv) Fourth Working Season (16th Oct 2015 to 15
th Oct 2016) :
v) Fifth Working Season (16th Oct 2016 to 15
th Sep 2017)
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16.4.2 Excavation Methodology
For excavation in overburden material, combination of Ex-400 hydraulic excavator (2
cum bucket) and dumpers shall be used. For rock excavation, drilling and blasting shall be done
with crawler drills (with compressors). In addition, rock drills with or without pusher legs will
also be used. The loading and haulage equipment will be same as for excavation in overburden
material. The excavators shall be assisted by Dozers as needed. The type and number of
equipment required has been worked out in paragraphs on equipments.
16.4.3 Methodology for Concrete Placement
The concerting of dam blocks essentially consists of three main activities viz.
manufacture of concrete which includes Aggregate Processing Plant for production of Aggregate,
Batch and Mixing Plant and Ice Plant for production of ice. Aggregate processing plant and
Batch/Mixing Plants shall produce concrete for Dam, Intake as well as for other components of
the project such as HRT lining components of the project. The maximum concrete requirement
for placement of concrete in Dam Blocks is 200 m3/ hour. The Aggregate Processing Plant of 500
t/hr capacity shall be installed for production of aggregate and Batch/ Mixing plant of capacity
300 cum/hr shall be installed for production of concrete (Refer Chapter on Common works). The
ice plant of 90 t/hr capacity shall be installed so that required quantity of ice may replace the
water to be mixed in concrete to bring the production temperature of concrete to 10°C. The
placement temperature of concrete as worked out by thermal studies is 12°C. It has been assumed
that the temperature of concrete will rise by 2°C by the time it reaches from batch mixing plant to
the placement location.
16.4.4 Equipment Required for Works of Dam and Intake
List of equipment required for works of Dam and Intake Structure is as below
i). Ex-400 Hydraulic excavator/equivalent 2 Nos.
ii) 20 t capacity dumpers 9 Nos.
iii) Crawler/ wagon drills IRCM-341 4 Nos.
iv) Compressor 450 cfm 4 Nos.
v) Compressor 1000 cfm 2 Nos.
vi) Dozers 180 HP/equivalent 2 Nos.
vii) JCB Back Hoe 2 Nos.
viii) Radial Cable Cranes (9 m3 capacity) 2 Nos.
ix) Concrete buckets (9 m3 capacity) 4 Nos.
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x) Silo Buses 10 Nos.
xi) Concrete pump 38cum/ hr 2 Nos.
xii) Transit Mixers (6 cum capacity) 3 Nos.
xiii) Needle Vibrators (65 mm dia. Needle) 6 Nos.
xiv) 150 mm dia Needle Vibrators with frequency changers 2 Nos.
xv) Mobile crane (Hydra) 8/10 capacity 2 Nos.
xvi) Air water Jet Blaster 2 Nos.
xvii) Sand Blasting Equipment 2 Nos.
xviii). Grout Pump SURFEX with capacity of 50 lit/min 2 Nos.
at 1.5 N/mm2 pressure
xix) Drilling machines Diamec 262 2 Nos.
xx) Dozers D-50 (wheel Mounted) 2 Nos.
xxi). Dry shotcrete Machine 4/6 m3 per hour 2 Nos.
16.5 HEAD RACE TUNNEL
The total length of the 7.5 m dia (finished) circular shape Head Race Tunnel, aligned on
right bank of river Siyom is 9202 m. Tunnel with a circular shape will be concrete lined having a
finished diameter of 7.5 m. The alignment of tunnel has been fixed in such a way that adequate
lateral and vertical rock cover is available at any particular location.
16.5.1 Infrastructure
In order to access the work sites on right bank from the BRO road on the left the
following basic infrastructure is required to be in place before taking up the tunnel excavation.
Two no. bridges of approximately 60 m and 80 m span shall be needed to access the Adit
locations. One steel girder bridge of 80 m span is proposed to be erected on river Siyom near
Powerhouse location at an Elevation of ± 1040 m. A suitable diversion road from existing BRO
road will be provided to connect the bridge location which will provide access to Adit near Surge
Shaft and Intermediate Adit no.-2. Second bridge of 60 m span across Siyom river is proposed to
be erected upstream of junction of Sitten Nallah with Siyom river. The bridge will provide access
to Inlet adit and Intermediate Adit no.-1.
16.5.2 Construction Methodology and Equipment Planning
The excavation of HRT will be done by using Drill and Blast Method (DBM). The
excavation of HRT shall be done by using four Adits of 7.0 m D-shaped i.e. Inlet Adit,
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Intermediate Adit-1 and 2 and Adit to HRT near Surge Shaft. The above Adits meet the HRT at
chainage 596.12 m, 3029.228 m, 5876.828 m and 9097.974 m respectively. Thus eight faces are
available for excavation of HRT.
16.5.2.1 Excavation
After jungle clearance and construction of roads and bridges, the excavation of Adit
portals will be taken up. The overburden will be removed with the help of Excavator and Dozer
whereas open excavation at portal face will be carried out by conventional Drill Blast Method
with the help of Jack hammers and portable compressor. The mucking will be done by Excavator
and Dumpers. The rock above the portal face will be excavated in a stabilized slope.
Four no. Adits (7.0 m D-shaped) will be provided for excavating HRT having total length
of 9202 m. The location of Adits has been fixed keeping in view the geological and
topographical conditions as well as construction convenience. The size of Adits has been kept as
7.0 m D-shaped keeping in view the easy movement of mucking equipment. The slope of various
adits has also been kept mild in order not to stress the loaded equipment unnecessarily. A
positive slope to all the adits has been provided in order to make them self draining. The
excavation of Adits has been planned to be carried out full face by normal Drill and Blast
Method as soon as the portals are established. The drilling operation for excavation of Adits is
proposed to be carried out by deploying two-boom drilling jumbos and mucking will be done
with the help of side tilting loader (2.5 cum) and 20 T capacity dumpers.
16.5.2.2 Head Race Tunnel (Heading)
The excavation of heading will be carried out in following operations.
i). Survey and marking of profile
ii). Drilling operation Drilling will be done by using two boom hydraulic drilling Jumbos,
which can theoretically drill up to 2 m per minute say 100 m per hour of 50 minutes
working)
iii). Charging and Blasting (The holes drilled will be loaded by Powergel or equivalent. Non-
electric detonators with millisecond delay are proposed to be used.
iv). Defuming (At the time of excavation of tunnels, adequate provision for proper ventilation
is absolutely essential; therefore an effective ventilation arrangement has been planned
during excavation of tunnels).
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v). Scaling (The scaling is proposed to be carried out manually with help of scissors
platform.
vi). Mucking
vii) Rock Support Measures (Shotcreting shall be carried out up to excavated face after each
blast whereas rock bolting shall be provided about 2 pulls behind the excavated face).
16.5.2.3 Head Race Tunnel (Benching)
After heading operations are complete between two Adits, the benching of 1.2 m will be
carried out by conventional bench blasting method. The progress targeted for benching
operations is 20 m per day i.e. a monthly progress of 500 m. Same equipment as provided for
heading excavation shall cater for benching operations as well.
16.6 EQUIPMENT PLANNING FOR TUNNEL EXCAVATION
The planning of equipment has been carried out based on following data.
i). Excavated Tunnel Area at minimum excavation line (heading) 49.94 m2
ii). Excavated Tunnel Area including payline and 5% over excavation (heading)52.44 m2
iii). Blast Hole diameter 41 mm
iv). Empty hole diameter 102 mm
v). Advance per pull 3 m
vi). Drilling Equipment Two boom hydraulic drilling Jumbos
vii). Theoretical rate of penetration 2 m / minute
or 100 m / hour
viii). Actual anticipated rate of drilling 80 m / hour
ix). Swell Factor 1.5
x). Estimated loose muck per pull 235.98 m3
xi). No. of drill holes 110
xii). Depth of drilling for each hole 3.5 m
xiii). Total drilling involved 385 m
16.7 CONCRETE LINING OF HRT
The concrete lining in HRT is proposed to be carried out after completion of benching.
The lining is proposed to be carried out by using three set of shutters (each set containing two
shutters and one traveler). The sequence of concrete lining operations in overt will be as follows:
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i). One set of shutter will be installed at chainage 0.0 m. This shutter will move towards Inlet
Adit (Ch. 596.12). After completion of this reach the above set of shutter will be
dismantled and installed at chainage 3029.228 m. This shutter will move towards the Inlet
Adit. For supply of concrete 30 cum/hr capacity CBP installed at Inlet Adit will be used.
ii). Second set of shutter will be installed at chainage 5876.828 m and lining will proceed
towards Intermediate Adit-1. The 30 cum/hr capacity CBP installed at the portal of
Intermediate Adit-1 will be used for concrete placement.
iii). Third set of shutter will be installed at upstream end of Surge Shaft at chainage 9202 m
and lining will proceed towards Adit to Surge Shaft i.e. 9097.974 m. The concrete during
this reach will be supplied from CBP of 30 cum/hr capacity installed at portal of Adit to
Surge Shaft. After completion of lining from chainage 9202 m to Ch. 9097.974 m the
above set of shutter will be installed at chainage 9097.974 m and the lining between the
two chainages i.e. 5876.828 m and 9097.974 m will be completed and concrete will be
supplied from 30 cum/hr capacity CBP installed at portal of Intermediate Adit-2.
16.7.1 Grouting
16.7.1.1 Contact Grouting
Contact grouting in the tunnel is proposed to be carried out after 30 days of placement of
concrete in tunnel invert. After this the contact grouting will progress simultaneously with lining
activity of tunnel. Contact grouting is provided to fill any gap, especially at crown level, which
has been left during concreting activity between rock and concrete lining. For this purpose grout
holes of 38 mm diameter will be drilled 300 mm inside the rock and grouting will be done at a
low pressure of about 1 to 1.5 kg/cm2. The water cement ratio in the beginning will be kept
leaner and the same will be thickened as grouting progresses.
16.7.1.2 Consolidation Grouting
The same holes as utilized for contact grouting will be re-drilled up to a depth of 6m for
consolidation grouting. The consolidation grouting will be done at a pressure ranging from 5
kg/cm2 to 7 kg/cm
2. The consolidation grouting in this case will also be carried out till refusal.
16.7.1.3 Plugging of Adits
Once the grouting operations in the tunnel as well as all other activities in adjacent
components i.e. Surge Shaft and Intake are completed the Adits will be plugged with concrete.
For this purpose adequate no. of Shear keys will be provided. To fill any gap between rock and
Environmental Management Plan – Construction Methodology
Hirong H.E. Project, Arunachal Pradesh 16-14
CISMHE
concrete plug the consolidation grouting will be carried out after plugging operations have been
completed. Two no. adits i.e. Adit near Surge Shaft and Inlet Adit are proposed to be provided
with a vehicular access each.
16.7.1.4 Cleaning of HRT
After completion of all activities the tunnel is to be thoroughly inspected for any foreign
material left inside during construction. This will ensure that no
16.7.2 Construction Equipment for HRT
The summary of equipment is given below
Sl. No Construction Equipment Quantity
A. Drilling and Blasting Equipment
i). Portable Compressors – 1000 cfm 6
ii). Two boom drilling Jumbos 6
iii). Crawler drill IRCM – 341 along with 450 cfm compressors 4
iv). Jack Hammer with Pusher legs 12
B. Mucking Equipment
v). Wheel mounted Dozer (180 HP) 3
vi). Loader 2.5 m3 bucket capacity side Dump Loader 6