internship report on NJHPP

Submitted by

TONJHPC

University of Azad Jammu & Kashmir Muzaffarabad

INTERNSHIP REPORT

Internship Report

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LIST OF CONTENT ABSTRACT____________________________________04 INTRODUCTION________________________________05 LOCATION_____________________________________06 SALIENT FEATURES______________________________07 STRATIGRAPHY OF C1____________________________09 STRUCTURAL GEOLOGY OF C1_____________________11 DAM FEATURES_________________________________12 TUNNELING IN C1_______________________________14 CURTAIN GROUTING IN C1________________________19

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ABSTRACT

Nauseri area lies on the active fault called Main boundary thrust. The fault is thrust fault between Murree formation and Punjal formation. Area have numbers of drainage channel. Rocks of punjal formation are highly fractured and massive joints are also found. Rocks of Punjal formation are crushed and often joints are found in Dam site of C1. The drainage channel and active fault promote the rocks of punjal formation to fall in the shape of landslide and rock slide. These landslides may affect the Dam structure, due to these reasons debris flow channel is constructed. Tunneling in the Nauseri area is done by Drill and Blast (D & B) method. This method of tunneling is economical but time consuming. In tunnel sandstone and siltstone of Murree formation are found that are weak rocks but due to their stable structure Drill and Blast method is safe. Curtain grouting is done in the debris flow channel side of the dam to made underground barrier to prevent dam from seepage. The grouting is done on the fault zone due to which underground rocks are weak. Often during the filling of grout in the drilled hole the grout flow in the direction of subsurface joint or water channel. These problems are solved by using grout packers. Due to soft rocks of Murree formation in subsurface when bit cuts the soft rocks, bit rotate at a level and not cut further but increasing diameter of the hole. This make serious problem for workers. This problem is also solved by using grout packers.

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Introduction toNEELUM JHELUM HYDROELECTRIC PROJECT

ORGANIZATIONThe Project is running through Neelum Jhelum Hydro-Power Company (NJHPC) WAPDA, headed by a Board of Directors (BOD). The Chairman of the BOD is Chairman Wapda. Members of the Board are Chairman Wapda, Member (Water) WAPDA, Member (Power) WAPDA Member (Finance) WAPDA, CEO (NJHPC), CFO of the Company and EX-CEO of NJHPP, Chief Secretary Azad Jammu & Kashmir, Additional Secretary Ministry of Water and Power, Additional Secretary Economic Affair Division, Additional/Special Secretary Ministry of Finance. MD/Chief Executive Officer, the representative of Board of Directors, has his office at Islamabad whereas Project Director (General Manager) has his office at Muzaffarabad (AJ&K).

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LOCATIONNeelum Jhelum Hydroelectric Project (NJHEP) is located in the vicinity Muzaffarabad (AJ&K). It envisages the diversion of Neelum river water through a tunnel out -falling into Jhelum River. The intake Neelum Jhelum is at Nauseri 41 Km East of Muzaffarabad. The Powerhouse will be constructed at Chatter Kalas, 22 Km South of Muzaffarabad. After passing through the turbines the water will be released into Jhelum River about 4 Km South of Chatter Kalas. Neelum Jhelum Hydroelectric Project has installed capacity of 969 MW. The Project will produce 5.15 Billion units of electricity annually.

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SALIENT FEATURES

Overall Project Cost Rs. 274.882 Billions 

Installed Capacity 969 MW, Four Units @ 242.25 MW each

Dam,  Type  Composite Dam (Gravity + Rock fill)

Height / Length 60 / 160 Meters

Average Annual Energy           5.150 Billion electricity Units Annually

Average Head 420 MetersDesign Discharge 280 Cubic meter per secs

TunnelingTwin TunnelSingle TunnelTailrace Tunnel

Length 19.54 km eachLength 8.94 kmLength 3.54 km

EIRR   25.46 %

Date of Commencement 30-01-2008

Expected Completion date November 2016

Implementation Period  106 months

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The Neelum Jhelum Hydroelectric Project is split into the following three main geographic areas

1. NAUSERI AREA (ALSO KNOWN AS C1)A 60m high Composite (Gravity + Rock fill) diversion dam and sedimentation basin near Nauseri is on the Neelum River. The dam has 3 No. Radial gates and 2 No. flap gates designed to pass floods of 1000 year recurrence period and also allow the reservoir to be drawn down for sediment flushing. The sedimentation basins are designed to trap sediments that could erode the turbine blades at the powerhouse. The intake works are designed to divert up to 280m3/s into the headrace tunnels.

2. MAJHOI/THOTA (ALSO KNOWN AS C2)The headrace tunnel is 48 km long including twin tunnel and conveys the water from the intake area at Nauseri to the Powerhouse area near Chatter Kalas. The tunnel crosses under high ground and also across the Muzaffarabad fault zone. A 19.54 Km stretch of the tunnel from the Nauseri be constructed as a twin tunnel system each with x-sectional area ranging from 52-58 m2 and the rest of the route, a single tunnel of x-section area 100 m2 approx has been proposed. The tunnel portion to be excavated with TBM will be shortcrete lined with a concrete invert while the drill and blast portion of the tunnel will have full face concrete lining. The tunnel crosses under the Jhelum River at 602 m asl, approximately 180 m below Riverbed.

3. CHATTER KALAS AREA (ALSO KNOWN AS C3)The headrace tunnel will feed four vertical-shafts Francis turbines with an installed capacity of 969 MW housed in an underground powerhouse. The water is discharged back into the Jhelum River near Zamainabad through a 3.54 km tailrace tunnel. Associated facilities include a transformer hall, surge shafts, access tunnels, a 500 kv switchyard and housing facilities for the operations and maintenance personnel.

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STRATIGRAPHY OF C1The stratigraphy of the Nauseri area is comprised of two formations:

• PUNJAL FORMATION• MURREE FORMATION

PUNJAL FORMATION• The lithology of Punjal formation is consists of metavolcanics and

metasediments. In metavolcanics greenstone and graphitic schist are found. Greenstone are volcanic rocks that are metamorphosed up to green schist facies. In metasediments marble and quartz lenses and found in punjal formation. As shown in Fig:

• Age of the Punjal formation is Permian.

PUNJAL FORMATION

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MURREE FORMATION• Murree formation is the molasses deposits formed by the erosion during

Himalayan orogeny. The lithology of Murree formations is consists of sandstone, mudstone, and siltstone.

• Age of the Murree formation is Miocene.

MURREE FORMATION

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STRUCTURAL GEOLOGY OF C1• C1 is lies on Main boundary thrust (MBT) that is active fault between Punjal

formation and Murree formation. The Murree formation of Miocene age is thrusted on Punjal formation of Permian age. MBT is an active fault in Nauseri area (C1).

• The rocks of Punjal formation are fractured and massive joints are found. The foliated graphitic schist are crushed near the fault zone.

• There are numbers of drainage channel in the C1 area. These drainage channels promotes crushed rock material to slide in the shape of land sliding. Due to these reasons the debris flow channel is especially design for the safety of the dam; so that the crushed material often slides will collected in debris flow channel and will not affect the stability of the dam.

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Dam Features• A composite Dam (Gravity + Rock fill) 160m long and 60m high will be constructed

on Neelum River at Nauseri. It is a Gated Diversion Dam. The dam will create a head pond of 10 million cubic meters which will allow a peaking reservoir of 3.8 million cubic meters to meet daily peaking of power for more than 4 hours. A six gate tunnel intake structure of 280 cumecs capacity will be connected three conventional flushing surface basins installed at their end for taking sediment back into river. The total length of headrace tunnel is almost 48 Km. A 19.54 Km stretch of the tunnel from the Nauseri site will be constructed as a twin tunnel system each with cross sectional area ranging from 52-58m2. The remaining headrace tunnel down to the surge chamber will be a single tunnel having cross sectional area 100m2 approximately. The tunnel portion to be excavated with TBM will be shortcrete lined with a concrete invert while the drill and blast portion of the tunnel will have full face concrete lining. The tunnel crosses under the Jhelum River at EI. 602.0, m asl, approximately 180m below Riverbed. The tunnel is accessed by 8 construction Adits for removal of excavated spoil.

OUT IN

Spill ways & diversion tunnel

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The Surge Chamber consist of 341m high riser shaft and 820m long surge tunnel, four steel lined Penstock tunnels 118 m long and having 3.8 m internal diameter will also be constructed. The underground power Station will have four units with a total capacity of 969 MW. The Power Station will be connected with Gakhar Grid station through 500KV double circuit transmission line.

Debris flow channel Spill ways

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Adit 1

• Nauseri area (C1) contains one Adit (A1) to access the tunnel. As shown • A1 is 485m long connected to single headrace tunnel. The single headrace tunnel

is 800m in length after 800m single headrace tunnel is bifurcated into twin headrace tunnel. Both tunnels in twin headrace tunnel are connected with one another by cross-cut.

• In the Nauseri area (C1) tunneling is done by drill and blast method (D & B). The D & B method involves following steps:

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Survey to mention the points on the tunnel face for drilling and charging according to Blast design

• SURVEY: Survey is done to maintain the tunnel alignment. By the survey tunnel is avoided from under break and over break of tunnel. Survey also includes to mention the points on the tunnel face for drilling and charging according to Blast design.

• DRILLING AND CHARGING: Drilling is done by the machine called Hand held air leg pusher machine (HHALPM). Drill holes are filled with charge and connected to circuit have button to initiate the blast.

• BLAST: The button is pressed and blast happens on the charged face of the tunnel. All the charge holes are blasts not at a time but with difference of microseconds to avoid the whole structure to collapse.

HHALPM

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• MUCKING: Mucking is the process for removal of the excavated material.• SCALING: Scaling is the removal of loose rock parts mechanically & manually by

excavator bucket ,jack hammer and scaling bar. • GEOLOGICAL MAPPING: Geological Mapping is an important component during

tunnel excavation. The discontinuities (bedding & major joints , joints sets ,fault , shears etc. and lithological contacts) and lithology from exposed faces, crown ,walls are mapped and supports recommendation are made after evaluation of rock mass characteristics using Q – system.

Scaling with iron barExcavated material

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As the tunnel is excavated the crown and sides of tunnel need to be supported to avoid the rock falling and structural collapse. The support work includes the initial support and final support.• Initial support work Includes rock bolt, wire mash, shotcrete, UPN, ring beam,

lattice girder.1st LAYER OF SHOTCRTE (SRF)Spraying of 6 cm thick 1st layer of Fiber Reinforced Shotcrete by shotcrete Jumbo / machine / robot after flushing the surface with pressurized air and water.

SHOTCRTE

SUPPORT WORK

Rock bolt

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• INSTALLATION OF ROCK BOLTSInstallation involves grouting of clean drilled holes withcement –sand grout (1:1) then inserting rock bolt ф =25mm , 4~7 m long (10 cm outside).• FIXING OF WIREMESH• 2nd LAYER OF SHOTCRETESpraying of 8~10 cm thick 2nd layer of SRF• Final support work includes concrete lining contain needle beam framework and

35cm concrete thickness.• CONTACT GROUTING: After concrete lining holes are drilled that make contact of

concrete tunnel wall with side rocks. Mortar is injected into the drill holes.

Tunnel Lining under progress

TUNNEL AFTER CONCRETE LINNINGWIREMESH

CURTAIN GROUTING IN C1• Curtain grouting is the process to make barrier that protects the foundation of a dam

from seepage. In C1 curtain grouting is done on the dam site. The process of curtain grouting is done in different steps follows as:

• . DRILLING FOR GROUTING: In first step the hole is drill which has to grout• GROUT: Grout is mortar formed by mixing cement and water in specific ratio in the

Collided drum and send to agitator for mixing the grout.

Collided drumDrilling Machine

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• AGITATOR: Agitator is machine used for mixing of grout.• DENSITY TEST: The sample of grout from Agitator taken into the Density scale device.

Density scale device measure the density. The density value must be equal to the density desired value.

• VISCOSITY TEST: The sample of the grout from Agitator taken into the viscosity cup. When the viscosity cup is filled, allow the grout to flow out and stop is started at the same time. The viscosity value of grout must equal to the desired value.

Agitator

Density scale device

Viscosity cup

• After the density and viscosity test the process of grouting is ready to start.

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Flow Meter

FLOW METER: Grout from agitator flow to the Flow meter. Flow meter is an instrument used to measure rate at which grout flow into the drill hole. Wire from flow meter is connected to the Grouting recorder machine. PUMP MACHINE: Grout from the flow meter comes to the pump machine. Pump machine pump the grout to the pressure gauge.

PUMP MACHINE

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PRESSURE GAUGE: Pressure gauge is an instrument that measures and gives a visual display of the pressure in PSI. Wire from the pressure gauge is connected to the Grouting recorder machine. DENSITY METER: Grout is then comes to the density meter. Density meter is an instrument used to determine density of the grout. Wire from density meter is connected to the Grouting recorder machine.

Pressure gauge Density meter

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• GROUT RECORDER MACHINE: Grouting recorder machine is electronic device that determine and record the density value (R), flow rate (Q), total flow rate (Q) and pressure value. Wire from the density meter, pressure gauge and flow meter are connected to the grouting recorder machine, which display density value (R), flow rate (Q), total flow rate (Q) and pressure value on screen on recorded values on paper.

GROUT RECORDER MACHINE

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• GROUT PACKER: Grout packer is a device that has expending property, inserted into hole being grouted to prevent return of grout around the injection pipe. Often during the filling of grout in the drilled hole the grout flow in the direction of subsurface joint or water channel. These problems are solved by using grout packers. Due to soft rocks of Murree formation in subsurface when bit cuts the soft rocks, bit rotate at a level and not cut further but increasing diameter of the hole. This make serious problem for workers. This problem is also solved by using grout packers.

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Thank You