Nathpa Jhakri Hydroelectric Project

GUIDE BOOK FOR
FIELD EXCURSION
30 October – 02 November 2015
Indian Society of Engineering Geology
(Indian National Group of International Association for
Engineering Geology and Environment)
1500 MW Nathpa Jhakri Hydroelectric Station
INTERNATIONAL CONFERENCE ON
ENGINEERING GEOLOGY IN NEW MILLENNIUM
27-29 October, 2015 at New Delhi
Organized By
Sponsored By
(1965-2015)
Golden Jubilee Year
Indian Society of Engineering Geology
(IAEG India NG)
International Association for
Engineering Geology and the Environment (IAEG)
In Association with
Geological Survey of India
(Ministry of Mines, Government of India)
Mineral Exploration Corporation Ltd. ( MECL)
( A Mini Ratna Government of India Company)
Converner
Dr. Manoj Verman, Consultant
Co- converner
Mr. Ashok K. Chadha
Excursion Committee Members
Mr. B.M. Gairola, Superintending Geologist, GSI
Mr. Pradeep Singh, Superintending Geologist, GSI
Mr. Harish Bahuguna, Superintending Geologist, GSI
Mr. N.K. Mathur
Mr. Bhuvanesh Kumar
Mr. Jaydip Mukherjee
Mr. Shakti Prakash
Itinerary
30 October 2015:
New Delhi - Chandigarh (3hrs.25min by train)
0615hrs: Dep. Hotel for New Delhi railway station.
0740hrs: Dep. New Delhi by Kalka Shatabdi (Train No. 12011)
Breakfast courtesy Indian Railway.
1105 hrs: Arr. Chandigarh.
Chandigarh - Shimla (105kms)
1130hrs: Dep Chandigarh Railway Station by Taxi for Simla.
Brief stops enroute for Technical and Sightseeing at following locations:1. Kalka Barog section – The Paleogene succession of the Himalayan foreland basin (Subathu, Dagshai
and Kasauli Formation) are exposed between Kalka and Barog. This section is immensely important as
it preserves evidence of India-Asia collision.
2. Barog – Near Barog, the Main Boundary Thrust is present along which Palaeogene foreland basin
succession is thrust over by the late Neoproterozoic Infra Krol and Krol carbonate sequence.
3. Solan town – Here, within the antiformal portion of the Krol belt, due to erosion, the Sabathu
Formation is exposed as a window, which provides an evidence of Krol being a thrust sheet. Blaini
diamictite variously considered as flysh, mudflow and glaciomarine are also exposed in the section.
4. Kandaghat - here the Krol belt is truncated by Giri fault along which the Chaosa Formation of the
Shimal Group has been translated.
5. Kathlighat Railway Station - The Jutogh Thrust sheet has been translated over the Jaunsar along the
Jutogh thrust near Kathlighat Railway Station. The Jutogh Group in the Himachal Himalayas and their
equivalents elsewhere are considered to represent a several km thick crustal scale ductile shear zone,
the so called Main Central Thrust Zone. In this sector Jutogh forms part of a Klippe described as pear
shaped Shimla klippe.
(Lunch enroute at local restaurant)
1700hrs: Afternoon arrive at Shima, check in at hotel. After
freshened up in the evening proceed for an exciting
shopping spree. The main market of Shimla, known as The
Mall road is bustling with energy with umpteen shops
lining the area, you can head in any direction and you’ll be
treated to a number of delights. From the chaotic Tibetan
market to the dazzling lakkad bazaar, shopaholics are in for
a bundle of surprises. Wooden items, woolen clothes and a
plethora of souvenirs are some of the things you can pick
up here. In the night come back to hotel for Dinner.
Overnight at Shimla.
31 October:
Day 02: Shimla – Rampur Bushahr (135kms)
0900hrs: After Breakfast depart for Rampur Bushahr, an
old town on the banks of the River Satluj. Enroute are the
famous apple belts of Kotgarh and Kumarsain descending
to the Satluj Valley. It was the winter capital of the former
princely state of Bushahr, and an important centre on the
old Hindustan Tibet trade routes. Lunch enroute at local
restaurant.
1400hrs: Arrive Rampur Bushahr, check in at hotel.
1500hrs: After freshening up proceed for site visit to the
powerhouse of the 1500 MW capacity Nathpa Jhakri Hydroelectric Station located at Jhakri near
Rampur.
1900hrs: Evening come back to hotel for Dinner.
Overnight at Rampur Bushahr.
01 November
Day 03: Rampur Bushahr – Nathpa and back
(120kms)
0900hrs: After Breakfast depart for visit to dam site at
Nathpa.
1100hrs: Arrive Nathpa. After freshen up, buffet lunch at
Nathpa Rest house .
1400hrs: Proceed for site visit.
1900hrs: Return to hotel at Rampur; dinner at hotel.
Overnight at Rampur Bushahr.
02 November
Day 04: Rampur Bushahr – Chandigarh Station (243kms)
0800hrs: After Breakfast, proceed for Kalka station to catch the train to Delhi. Lunch enroute at local
restaurant.
1630hrs: Arrive Chandigarh station
1715hrs: Board on train, Dinner courtesy activity in Indian Railway onward journey.
2200hrs: Arrive Delhi; you will be picked from the station and transfer to your stay hotel.
Route map Delhi to Jeori
Jeori
Rampur
19
17
Sarahan
75
Narkanda
N
Shimla
64
120
Chandigarh
46
Ambala
210
Delhi
City
Name of the Hotel
Room Category
Nights
Shimla
Quality Inn or similar
Base Category
1
Rampur
Hotel Mahesh or similar
Base Category
2
Validity
Vehicle
Tour Cost in INR
01 Paying pax on twin sharing basis
Innova car 3 seater
` 17,100
01 Paying pax on single occupancy
Innova car 3 seater
` 21,220
*Above tour is valid for minimum 6 pax
**The rates have been revised due to amendments in the government taxes.
The tour cost includes the following specific services:
» Hotel accommodation in the hotels mentioned or similar based on sharing a double room with
attached bath for a total of 01 nights based on Room & Breakfast basis as per the itinerary. This
includes presently applicable Government taxes, which are subject to change.
» Check in and checkout time at all hotels is 14.00 hrs and 12.00hrs respectively unless otherwise
specified
» Sightseeing's and excursions as per the itinerary with services of accompanying appointed English
Speaking Guides.
» Briefing on geology for all the tour enroute.
» Intercity transportation and visits by air conditioned vehicle, as per the itinerary
The tour cost DOES NOT include:
» Items of a personal nature such as cost of meals, table drinks, telephone calls, laundry, tips etc.
» Presently applicable Government Service Tax of 3.5% on the total tour cost
» Any international air fares, visa charges.
General Terms:
» The tour cost includes only the services listed above and those mentioned in the enclosed itinerary
» Shopping is a personal activity, Meetings & More will not be responsible for any shopping
undertaken by the participant
Introduction
The 1500 MW Nathpa Jhakri Hydroelectric is one of the largest run-off-the-river schemes in the world.
It is designed to generate 1500 MW of power. The project is located at a distance of 150km from Shimla
and it is approachable by NH-22 Hindustan-Tibet road. In the project area river Satluj cuts across the
rock formations of higher Himalya. The power house site is about 150km from the nearest rail-head
Shimla. Construction of the project commenced in March 1993and was commissioned on 18th May
2004.
The project was started by nathpa-jhakri Power Corporation, a joint venture of the centre and state
government which was renamed as sutlej jal vidyut nigam four years ago. The Project was
commissioned in 2003 has been running successfully over the past 10 years constantly achieving new
milestones and setting new benchmarks of excellence. The company has managed to achieve and
sustain excellent physical and financial performance since commissioning of the NJHPS.
The field trip provides an opportunity to visit the various components of this mega project which is an
engineering marvel with a very large underground power house complex, desilting complex
comprising four chambers, each 525 mt long, 16.31 mt wide and 27.5m deep, capable of
accommodating a nine-storey building and one of the longest power tunnels in the world.
Geology along the excursion route
The excursion route also provides an opportunity to study one of the best developed, most easily
accessible and studied section of Himalayas since 1928 (Pilgrim and West, Mem GSI 53) along the
Kalka-Shimal-Rampur road (NH 22) leading up to the project site.
Table: Regional stratigraphic framework of Himalayan rocks along Chandigarh- Jhakri Road
Group
Formation
Quaternary
Sediments
Siwalik Gp.
Sirmur Gp.
Jaunsar/ Shimla
Gp.
Shali Gp
Rampur Gp.
Jeori Wangtoo
Gneissic Complex
Kasauli
Dagshai
Subhatu
Krol-A
Krol-Sandstone
Infra-Krol
Blaini
Age
Lithology
Recent to Sub-Recent
Alluvium
Upper Miocene to Upper
Pleistocene
Early Miocene
Late Eocene to Oligocene
Paleocene to Eocene
Late Precambrian
Fine to coarse grain upward coarsening mudstonesandstone succession.
Grey sandstone, siltstone, shale
Maroon sandstone, siltstone
Shale, siltstone, sandstone, limestone.
Limestone, dolomite and calcareous shale
Yellowish colour sandstone with friable nature
Shale,siltstone
Diamictite,Sandstone,Siltstone and Limestone
Neoproterozoic
Unconformity
Mesoproterozoic
Unconformity
Palaeoproterozoic
Unconformity
Paleoproterozoic
Sandstone, Shale, Siltstone, Limestone, conglomerate
Limestone, Shale, Sandstone
Quartz, Phyllite
Granite, Schist, Gneisses
Source: Geology & Mineral Resources of Himachal Pradesh, GSIMiscellaneous Publication No. 30 : Part - XVII
The Himalaya is the youngest evolving active mountain belt in the world, displaying various
geodynamic processes and the development of distinct tectonic This highest mountain chain in the
world extends laterally for about 2500 km from Nanga Parbat (8126 m, 338150N:748360E) in the west
to Namche Barwa (7756 m, 298370N:958150E) in the east and has a width of 250–300 km. The Nathpa
Jhakri Project is situated in the western part of the Himalaya.
The section along the excursion route begins with Indo Gangatic alluvium, which is followed by the
Siwalik sequence along the Himalayan Frontal Thrust (HFT), near Pinjor.
The Siwalik (Lower Siwalik = Nahan) continues slightly beyond the Police barriers located on the road
and contain plant fossils. The Siwaliks are followed by the Paleocene- Early Miocene sequence
constituting the marine Subathu, tidal flat- fresh water Dagshai and mainly fresh water Kasauli of
foreland basin.
This sequence is thrust over by the late Neoproterozoic Infra Krol, which in normal order of
superposition is followed up by the Krol carbonate sequence designated as Krol belt. Within the
antiformal portion of the Krol belt, due to erosion, the Sabathu Formation is exposed as a window in
the Solan area, which provides an evidence of Krol being a thrust sheet. Blaini diamictite variously
considered as flysh, mudflow and glaciomarine are also exposed in the section.
The Krol belt is truncated by Giri fault near Kandaghat along which the Chaosa Formation of the Shimal
Group has been translated. The Chaosa Formation is stratigraphically followed by the Sanjauli
Formation near Kiarighat, beyond which,the Shimla Group is overlain by Jaunsar Group along the Chail
Thrust.
The Jutogh Thrust sheet has been translated over the Jaunsar along the Jutogh thrust near Kathlighat
Railway Station. The Jutogh in this sector forms part of a Klippe described as pear shaped Shimla
klippe.
Near Sanjauli due to reversal of dips, Jaunsar, Blaini-Shimla appears below the Jutogh.
The Simla Group is again followed by the Jaunsar Group. Another thrust sheet (Kullu Thrust sheet) rests
over the Jaunsar near Kadiali, which in turn is followed by the main Jutogh Thrust sheet, near Narkanda.
Going down the road, Kulu thrust sheet is exposed near Kumarsain which continues close to
Duttnagar, where due to deep erosion of Satluj along antiform the Basantpur Formation is exposed in a
window near Charota and Rampur Group is exposed between Duttnagar and Karcham in a window
near Jhakri, a high angle reverse fault has emplaced the basement gneiss (Jeori-Wangtu Gneissic
Complex) over the Manikaran Formation. This is a feature within the window. The Nathpa Jhakri Project
is
Bioturbation structure in
Subathu Fm. Note the typical
splintry Khaki Green Shale.
Turritella CF. SP Fossil
observed in Subathu Fm
Nodular weathering in purple
green shale of Dagshai Fm
Massive sandstone of
Kasauli Fm
Project Geology
The area exposes mainly unfossiliferous metamorphic rocks with basic and acidic intrusions belonging
to Jeori – Wangtu Gneissic Complex. These rocks are strongly foliated with well-developed augengneiss, mylonitic gneiss and porphyroblastic biotite gneiss with non-foliated granitoids in the central
part. These are the oldest rocks exposed in Himachal Pradesh forming basement for the Rampur
Group. The rocks exposed in the project area are mainly of two types – gneiss and schist with
amphibolite, granite and pegmatite. In the project area, where dam complex, desilting chambers and
HRT up to about Ch. 15km is located, different types of gneisses with some schist and amphibolite
bands have been met. Down stream of HRT Ch.15 km to the powerhouse complex, largely quartz micaschist with its variants occurs.
As the project is located in the one of the most active seismic region of the world, i.e. the Himalaya,
detail seismotectonic evaluation of the project and its surrounding area was carried out and after
detailed studies PGA (peak ground acceleration) of 0.23g has been adopted in the design.
SALIENT FEATURES OF NATHPA JHAKRI PROJECT
● Catchment area 49820 Km2
● Design Discharge- 383.3 Cumecs.
● Design Flood- 5660 Cumecs.
● Net Head- 435.35m
● 62.5 m high concrete gravity dam.
● 4 nos. horse shoe, 6m dia Intakes.
● Reservoir water spread area- 23.45 Hec.
● Live storage- 303 Hec.
● 4 nos. eggs shaped underground Desilting Chambers each 525X16.31X27.5m to remove sediments
above 0.2mm size, one of the largest underground complex in the world.
● 27.3km long 10.15m finished dia, HRT to carry 405 cumecs of water.
● 301m deep restricted orifice type Surge Shaft with variable dia. of 21m and 10.2m of, one of the
deepest in the world.
● Power House Cavern size 222x20x49m, largest in India.
● Vertical Axis Francis turbine- 250 MW X 6
● Project cost 8187 Crore, partly funded by World Bank.
● Design Energy-6612 MU
● Start of the project- 1993.
● Commissioning of project- May 2004.
● Cumulative generation till March 2014- 65336 MU
● HVOF(High Velocity Oxy Fuel) coating available at project.
● Stack Holder of the project- 9 states of North India.
● Catchment Area Treatment was done as per requirement. Rupees 50 Crore (Till April 2012) spent on
CSR activities.
The spectacular half tunnels/ overhangs on NH - 22
Summary of Geological Investigations
Project located in Higher Himalayas having variety of metamorphic rocks like gneisses, schists,
quartzite and basic intrusive (amphibolite) granite and pegmatite of Pre-Cambrian Age. Geological &
Geotechnical investigation studies were carried out by Geological Survey of India from year 1971 to
1993, till the start of the project and continued during construction phase of the project also.
Explorations for various engineering structures of the project was carried out by detailed surface and
subsurface explorations involving geological mapping on scales varying from 1:10,000 to 1:500, 3dimensional logging of 16 exploratory drifts (cumulative length 3308m) and drill core logging of 77
holes aggregating 7000m length.
During the construction stage, the quantum of geological works involved in the project were
geological assessment of 43666m of tunneling (HRT, DT, adits & other approach tunnels), 2600m
length of underground chambers (Desilting chambers, PH cavern, Transformer cavern, valve chamber
etc.) and 1176mdeep shafts(surge shaft, gate shaft, approach shaft etc.). Total geologically mapped
area is 1.3 million m2. Panel of experts comprising National & International experts in various
disciplines including geology monitored & advised the project authority throughout the construction.
World Bank Mission made periodic visits of evaluation of the progress. Center Water Commission
(CWC) was the principal design consultant during the construction.
CIVIL STRUCTURES
DAM and INTAKES
At the dam and intake site, gneiss and augen gneiss, trending nearly parallel to the E-W flowing river,
with thin amphibolite and schist bands occur. These rocks are intruded by pegmatite. The dam is
founded on jointed gneiss/ augen gneiss with schist and amphibolite bands intruded by pegmatite.
The dam site was investigated with a total of 21 holes with an aggregate length of 922.59 and three
exploratory drifts totaling 108.7m in length. Excavation in the river section was carried out by removing
12-18m thick overburden exposing the foundation grade rock. On the rive banks, excavation of 1-2m
was made at places to achieve acceptable slopes in the foundation, otherwise no stripping was
required to achieve foundation grade rock. Pot holes 0.3m to 3m deep were encountered in the
foundations which were dentally treated.
Due to unfavorable foliation on the left bank above the dam & intake, the slopes were stabilized with
38-42m long cable anchors of 200 Tones capacity. Similarly due to an unfavorable joint on the right
bank the slope above the dam was stabilized with 100 Tones capacity. Dam stability is being monitored
by about 100 instruments. Annual dam safety inspection/audit is being done by an expert external
agency (Dam Safety Organization, Nasik).
Nathpa dam during construction
Installation of 200T capacity cable Anchors at the Intake
DESILTING CHAMBERS
The water drawn through four independent intakes is conveyed by means of 6.0 m diameter, horse
shoe shaped four inlet tunnels and 50 m long transitions to the four underground desilting chambers
located on the left bank of the river Satluj. Each of the chambers is 525 m long, 16.31 m wide at the
center and 27.5 m high inclusive of 5 m hopper portion. The chambers are egg-shaped, having circular
arch roof, curved walls and hopper shaped bottom. They are spaced 45.6 m center to center leaving a
rock pillar of about 29 m between adjacent chambers.
Chambers area was investigated by an exploratory drift for a length of 1190m. The chambers have
been excavated in hard & moderately to closely jointed gneiss & augen gneiss (fractured at places)
with pegmatite. Biotite schist was the weakest rock in chambers as thin bands of 10cm to < 1m. The
foliations were 45-70˚ askew to the alignment. The chambers were supported with rock bolts and SFRS
lining while excavating. Instability occurred in the chamber in the form of rock falls (3 nos. - at the
intersection of construction adits) and cracks in the SFRS, when the excavation was just above the
hoppers. Updating of the rock support design, after detailed wedge analysis, revised numerical
modeling, bore hole camera studies, instrumentation and consultation with various national &
international Experts & Agencies, was taken up. The revised support involved three rows of prestressed 60T 20m long cable anchors linked with RCC beams preceded by scaling of cracked & debonded SFRS/loose rock, application of fresh SFRS & additional rock bolts of 8-12m length. Stability of
chambers is being monitored by instrumentation.
Instability in Desilting Chamber
Remedial Measures
Scaling & Rock Bolting (6-12m long)
The L-section of the desilting chamber and DRESS
(Drainage-Reinforcement-Excavation-Support-Solution)
methodology
Head Race Tunnel
27.4 km long HRT was explored by 24 drill holes for cumulative length of 2573.54m along with 7 nos. of
exploratory drifts for a total length of 735.3m beside other investigations till preconstruction. HRT
alignment intersected seven perennial nallas, one of which had deepest bed level with a cover of 9m
above HRT. The water of one of the nalla in the upper part of the tunnel has been added to HRT through
a drop shaft to augment the firm power of the project during lean season. The maximum cover above
the tunnel was around 1400m. The tunnel has been constructed through seven adits, the maximum
distance between two adits was 6600m. Rock types encountered along the HRT were gneiss, augen
gneiss (49.82 %), quartz mica schist (34.75%), amphibolite (11.99%) and quartzite (3.44%) intersected
by joints, shears, shear zones, weak zones & fractured zones.
Major shear zones
Though number of thick shear zones intersected the unnel, most have been tackled by normal
tunnelling techniques except Nathpa and Daj shears. Nathpa Shear of over 40m width intersected the
Nathpa Adit and has been negotiated by multiple drift method. Daj shear, where sheared rock zone
was anticipated to be 120m wide between Ch. 26,000m and 26,450m, branched into several smaller
shears. It was intersected at Ch.26139 m (Ratanpur d/s heading) where flowing conditions were
encountered with heavy ground water flow and was associated with a 30-40 m hick very soft rock zone.
Daj Shear was tackled by using DRESS Methodology (drainage, reinforcement, excavation, and
support solution), a special method employed in tunnelling through sheared and flowing media.
HRT intersected 3.37 Km long high temperature geothermal zone with a number of thermal water
manifestations in the middle lengths with maximum & minimum temperature of 60°C & 36°C
respectively. The geothermal zone began with a heavy thermal water blowout with a discharge of upto
125 l/sec at a temperature of 54°C flooding the tunnel. The high temperature in the working area
made the tunnelling conditions extremely difficult and the temperature was brought down by
deploying high power ventilator fan and dumping of large quantity of ice at the working face in the hot
zone.
Hot water ingress in HRT
Face collapse at heading
Tunnelling under a nalla with 8m cover consisting of Nalla material was successfully achieved. HRT is
concrete lined throughout except for two reaches of inadequate cover where steel liners of 8.5m dia.
for a cumulative length of 1085.56m (except transitions) have been provided.
No alteration of conceived HRT alignment was affected during construction despite of above
difficulties.
Surge Shaft
301m deep 21m dia. surge shaft was explored by four drill holes for a total length of 503.35m and three
drifts aggregating to the total length of 293m and encountered variety of litho units which included
loose overburden, weathered and sheared rock, shear zone and competent quartz mica schist
gneissose at places. The support system comprised of circular heavy steel sets at 1.25m c/c embedded
in RCC lining of 600m from the top of the shaft upto initial 55m which included a shear zone of 13m
width. The rock support in the sound rock consisted of 6-7.5m long grouted anchors bars at 3.0m c/c
with 50-100mm thick shotcrete. Shear keys were also provided. No major problem was encountered
during the entire excavation of the shaft.
View of the top of Surge Shaft
Power House Complex
222x20x49m Power house cavern was explored by 9 hole & 802m of exploratory drift. The power
house cavern was excavated with in low strength quartz mica schist with varying percentage of biotite
& muscovite. The cable anchor earlier proposed for the roof support during tender were replaced by
rock bolts, shotcrete with wire mess based on the geological data encountered during the excavation
of the adit to the power house. The crown was supported with 5-6.2m long, dia 32mm rock bolts &
150mm thick shotcrete with wire mess. Two reaches having sheared & weak rocks were additionally
supported with 11m long rock bolts, two layers of wire mess & adequate thickness of shotcrete to
cover the wiremess. The walls were supported with 7.5-11m long rock bolts, 32mm dia. at 3m c/c
staggered with wire mess & 150mm thick shotcrete. The vertical spacing among the rows was 1.5m.
No problem was encountered during the excavation of the power house. Some cracks developed in
the shotcrete in crown and on both the walls at different times & different stages of excavation were
proved to be present only in the shotcrete. The affected area in the walls was additionally supported
with three rows of 13.5 long rock bolts at 1.5 c/c. The power house cavern is being monitored by
various instruments like MPBX, crack meters.
Transformer hall cavern also encountered similar rock type but the rock strength was reduced due to
the high percentage of muscovite & biotite in the rock. Encountering of a thick shear zone in the initial
reaches of the adit along the transformer hall resulted in providing of rib support in the crown.
TRT area was explored by 16 holes. In the TRT out fall area the hill side channel slopes were supported
with 100T capacity 22-35m long, 412 nos. pre-stressed cable anchors of decreasing length from top to
bottom. After a huge slide resulting in reducing the length of TRT channel. Overburden slopes in the
TRT area were dressed to 32 slopes and lot of plantation was done to stabilize the area. The overburden
slopes were drained by drainage gallery at two levels and 50m long horizontal drainage hole and are
being monitored by piezometers.
View of the power house after completion
Notes
Notes
Topic:
Date:
Axis
View of the 'Kinnar Kailash' peak from Rekong Peo.
According to Hindu mythology the peak is considered as the winder abode of Lord Shiva