planning of kolkata metro railways

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    Planning of Kolkata metro railway system

    Prasun Roy Chaudhuri (2011MT 0130)

    Gautam Kumar Jha (2011MT0132)

    Nandan Kumar (2011MT0134)

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    Planning of Kolkata metro railways

    Historical background

    The city was designed by the British and could not cope up with the conditions of modern

    traffic increase. The streets were getting congested with overflow of cars and personal vehicles

    causing traffic jams. The city needed a new type of mass transport which could transport the

    people easily, fast and efficiently.

    There were different commissions set up to check for the feasibility of sub urban train lines.

    The ideas included over ground circular railways light tramways and other forms of

    transportations.

    There were reports by different commissions to up over-ground circular railways. The circular

    railway though set up couldnt ease the traffic congestion in the heart of the business district

    since the circular railways couldnt be constructed too close to Esplanade and Park Street area.

    The 1st

    commission to consider the underground metro system was the FRENCH METRO

    MISSION in 1949. Though the Mission did express some concern about the construction of

    underground tunnels due to bad soil condition in Kolkata.

    The French Metro Mission had proposed a two electrified routes from Howrah maidan to

    Sealdah (3.91miles) and another from Paikpara to Kalighat (7.14 miles). The Mission also

    proposed the creation of a passenger terminal in heart of the business district.

    The report proposed that both the route to be electrified and the ultimate capacity of the

    system be 50,000 passengers per hour.

    The mission reports was not considered then due to the lack of funding and also during that

    time the circular railways construction was given preference.

    Some of the major world cities with metro railways

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    Cities Population

    (in millions)

    Kilometers of

    rapid transit line

    Year of

    operation

    London 7.0 410 1863

    Paris 8.5 240 1900

    New York 17.2 370 1868

    Moscow 8.0 182 1935

    Tokyo 24.3 190 1927

    Kolkata 9.0 10 1984

    As we ca n se e from the abov e chart mo st of the mo dern ci ti es in the wo rld pref er

    mass transport system in the form of metro railways.

    Historical background of Kolkata metro

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    Kolkata was first Metro Railway system in India and was designed on international standards

    to ferry people to the business district quickly, efficiently and comfortably all the while keeping

    the transportation cost low.

    Idea was conceived in 1949 by Chief Minister. During the French Metro mission the

    underground rapid transport RTS (Rapid Transport System). But during that time the plans

    couldnt be materialized due to the lack of funds.

    Metropolitan Transport Project (MTP) setup in 1969 under Ministry of Railways and this body

    was given the authority to look over the construction of the metro project.

    Work of first line sanctioned in 1972. Surveys and construction work started in 1973-

    74 and completed in 1995 in 6 parts, first in Oct, 1984. DumDum (Airport) to Tollygunge a

    distance of 16.4 Km. 15 stations entirely underground was planned while the terminal stations

    were on the surface.

    Delay due to availability of funds, u/g utilities, court injunctions, no availability of vital material.

    There was a lot of opposition to the project since it was a new concept in India and also since a

    lot of the roads were to be dug up and traffic was to be diverted during the constructional

    phases.

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    The proposed route map of the metro

    The north south line shown in green is already constructed while the blue line is

    under construction.

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    Aspects considered when planning was done

    a) Geographical featuresb) Climatec)

    Drainage and flood levels

    d) Seismic datae) Geological featuresf) Traffic conditionsg) Predicted passenger entry

    Geographical features

    The land is flat and clayey in nature. Clay is not a good soil for tunnel construction since it hashigh water content and very low strength thus making the construction site and tunnel very

    prone to collapse and flooding.

    Most of it alluvial deposits due to the river delta formation. Since the work site is in close

    proximity to the river this added to the risk of water seepage.

    The maximum elevation of the land is 9m with average elevation of 6m from sea level. This also

    meant that the water table was high and the construction had to be shallow such that it did not

    penetrate the water table and case a disturbance in it.

    The land mass on the east and western sides are tidal marsh land. Thus the route on the east

    and west couldnt be constructed underground.

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    Climate

    The climate is tropical. Hot and humid for most of the year. Due to close proximity to the river

    the humidity of the city is high.

    There are distinct seasons. There is a hot season followed by the monsoons and a dry cold

    season. But the cold season is short and the monsoon rains are not uniform sometimes

    excessive rains causes flooding (in 1984). This caused the site to fill up and construction came to

    a halt.

    Some data about the climate of Kolkata

    Highest ever recorded temperature 43.9C in June,1924

    Lowest recorded temperature 6.1C in January, 1962

    Highest rainfall in 24 hours 369.6mm (28-9-78)

    Highest humidity 100%

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    Drainage and flood levels

    Drainage is a major factor in any underground construction since is prone to flooding. This is a

    very important factor since during construction there were concerns for site flooding and in

    some cases the trenches were deeper than the main drains which are supposed to take away

    the water. So pumps were kept handy to pump the water out to the main sewers.

    The drainage is done by sewer system which is managed by Kolkata Municipal Corporation. The

    water from the site was pumped into the main sewers which carried the water to the

    Bidyadhari river and out to sea.

    Due to heavy rains and flooding the metro station entry is kept at 500mm above the highest

    flood point at the location. So that during operation the water doesnt flood into the stations

    and tunnels from the entry points.

    Water due to seepage into the tunnels are collected in reservoirs in the tunnel midsections and

    pumped out by the use of SUMPs.

    Due to the planning for drainage and flooding the metro system has never been flooded. Even

    so there are 2 SUMPs provided at each stations to cope up in case of emergency.

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    Maximum flood level at a few major station sites

    Name of the station Level of crown of road

    (meters)

    Highest flood level

    (meters)

    Tollygunge +4.98 +5.16

    Kalighat +4.26 +4.36

    Rabindra Sadan +4.17 +4.65

    Park Street +5.10 +5.10

    Chandni Chowk +5.7 +5.7

    M G Road +3.96 +4.64

    Syambazar +5.43 +5.53

    Dumdum Jn Elevated station

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    Seismic data

    India lies in an earthquake belt and many regions are subjected to frequent earthquake thus

    the seismic monitoring is very important before construction. Although tunnels are considered

    much safer than surface buildings but earthquake can cause collapse and is dangerous during

    the construction phase.

    Kolkata falls in seismic ZONE III with and horizontal seismic coefficient of 0.04 to 0.06. Though

    Kolkata has minor tremors it is never in the dangerous level.

    Geological features

    Preliminary soil investigation was done by 50m borehole at 500m. The core got from thesewas sent to the lab for primary investigation. Detailed investigation was done by sinking 30m

    borehole at 100m interval.

    The primary strata were found to be Gangetic alluvium no borehole has been able to penetrate

    beyond it. The top soil is soft except for the upper layer which is firm and stiffness increases as

    depth increases.

    The soil was layered with patches of hard and silt and sandy river deposits. The soil just below

    the upper layer was of rotten timber and clay. The topmost layer is compact but the sub layers

    were much less harder but hardness increases with depth. The bedrock is so deep that that till

    now no excavation has reached it.

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    The strata can be divided into the following classification

    Top stratum

    (reduced level Approx in meters)

    Highest Lowest

    Stratum I Light brown sandysilt

    Ground level generally at 0.00

    Stratum II Grey or dark silty

    clay with semi

    decomposed timber

    +0.25 -11.5

    Stratum III Bluish grey silty clay -8.0 -17.5

    Stratum IV Brown sandy silt -13.0 -22.0

    Stratum V Brown or grey clay -15.0 -35.0

    Stratum VI Brown or light

    brown silty fine

    sand

    -30.0 -45.0

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    Strata details

    Stratum type Natural moisture

    content

    Cohesion

    C

    Kg/cm2

    Angle of friction

    degree

    Stratum I 30 0.28 0

    Stratum II 55 0.28 0

    Stratum III 30 0.56 0

    Stratum IV 26 to 32 0.42 15 to 33

    Av 32

    Stratum V 22 to 25 1.05 0

    Stratum VI 29 to 30 -- 40

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    Traffic conditions

    The major factor for the construction of the metro was to ease the traffic flow in the business

    districts of Kolkata.

    The chart below gives the people inflow via public transport into the business

    district

    Type of

    transport

    In bound traffic Outbound traffic

    Morning peak

    hours

    Daily total Evening peak

    hours

    Daily total

    Tram 48,019 3,91,230 43,247 3,79,661

    Bus 36,278 3,44,685 33,247 3,39,986

    Total 84,294 7,35,915 76,970 7,19,647

    From the above chart we can see that a huge volume of people use the public transport to get

    to the business district. Since these public transports are all surface based increasing the

    number of these will also increase in surface congestion.

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    Few of the causes for deteriorating traffic conditions in Kolkata

    1. Road area is not adequate to support the amount of traffic we have.2. Uneven footpath allocation and utilization.3. Some areas have 6 to 10 feet wide footpath where no people walks.4. 80% of Kolkata footpath is occupied by hawkers.5. Our habit - we do not like to walk on footpath. Even where there is no hawker on

    footpath people prefer to walk on road.

    6. All the road sides are used for parking for Taxi, Private cars, School bus etc.7. Not enough or none at all parking spaces available.8. People walking on road never want to abide by the signal.

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    Predicted passengers entry in metro railways after its construction

    Stations Predicted passenger entry perday in 1990

    Dum Dum 1, 23,000

    Syambazar 1, 43,000

    M G Road 1, 02,000

    Esplanade 1, 23,000

    Park Street 51,000

    Kalighat 1, 71,000

    Tollygunge 1, 96,000

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    System and parameter that was considered during construction

    The transit system is chosen to be a double rail system and mostly underground as there was

    no space for over ground space for construction of that magnitude. The construction was cut

    and covers but was carried out in phases so as to cause minimum disturbance to traffic.

    The 1st

    transit line was for Rapid Transport System was to be constructed between DumDum in

    the north and Tollygunge in the south. This too was constructed in phases.

    The stations are approximately 1km apart and are located at places of public interest where

    maximum passengers can be got most efficiently.

    After the route was fixed the main thing used in the system the coach dimensions other factors

    like moving dimension and fixed dimensions are calculated.

    This was used to predict the required clearance for peak hour traffic.

    Based on these calculations and dimensions the fleet of cars was decided.

    This helped in calculation of peak hour traffic and gave an average idea of the dimensions of

    the stations and platforms based on the peak rush hour passengers.

    In case of Kolkata metro the signaling system of international standard is considered such thattrains can be run at close intervals to each other.

    The frequency of the trains are scaled up or down during peak hours and off peak hours thus

    increasing passenger carrying efficiency.

    The rake size that was chosen for Kolkata metro has the following dimentions

    Length over couplers 20.3 meters

    Width 2.74 meters

    Height 3.70 meters

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    Station stop time of the trains

    Station stop time is an important factor to be planned.

    The station stop time should be such that it gives enough time for passengers to de board and

    get aboard the train while now allowing the train to idle in the platform for too long.

    The optimum time was predicted to be 30 sec per station while the average speed of the train

    35km/hr with a top speed of 80km/hr.

    A central control room was to be set up to monitor the trains from a central location and

    control the signaling system.

    The trains were also provided with public address system so that the next stations can be

    announced and people can get off more easily and also to announce the closing of the doors.

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    Features of Kolkata metro

    General features

    Gauge 1676mm (5-6)

    Length

    Centre to centre of the termini 16.450km

    Total length 17.185km

    Length of connection to car depot 0.877km

    Total including car depot 18.062km

    Number of station

    Underground stations 15

    Elevated 1

    Surface 1

    Distance between stations

    Average 1.028km

    Maximum 2.151km (DumDum to Belgachia)

    Minimum 0.597km (Chandni Chowk to Central)

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    Expected traffic when full section is opened

    Average weekday traffic

    1. Year of opening 1.32 million2. 5 years after opening 1.53 million3. 12 years after opening 1.73 million

    One way peak hour volume

    1. Year of opening 51,000 passengers2. 5 years of opening 60,000 passengers3. 12 years of opening 67,000 passengers

    Average tr ip le ngth 6. 80 km

    Train frequency during peak hours

    1. Year of opening 24 pairs/hr2. 5 years after opening 28 pairs/hr3. 12 years after opening 31 pairs/hr4. Theoretical 40 pairs/hr

    Number of trains per day

    1. Year of opening 3112. 5 years after opening 3743. 12 years after opening 429

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    Rolling stock and traction

    Number of coaches to be procured

    1. Year of opening 2322. 5 years after opening 2643. 12 years after opening 304

    Train composition 8 coaches total 163 in length

    1. Driving coach 22. Non driving motor coach 43. Trailer coach 2

    Class of accommodation One class

    Carrying capacity1. Driving motor coach 42 sitting 259 standing2. Non driving coach 48 sitting 278 standing3. Trailer coach 48 sitting 278 standing4. Total 8 coaches 372 sitting 2186 standing

    Coach dimension1. Length (buffer to buffer) 20.40 m2. Width (outer to outer) 2.74 m3. Height (above rail level) 3.70 m4. Maximum axle load 17.00 tones

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    Acceleration

    1. Maximum 1.1 m/sec22. Jerk rate 0.75 m/sec2

    Deceleration1. Service 1.1 m/sec22. Emergency 1.3 m/sec2

    Speed

    1. Maximum 80 km/hr2. Schedule 30 km/hr

    Station stop time 30 sec

    Traction system

    A. Voltage 750v DCB. Current collector 3rdrail (return running rail )C. Braking electro dynamic and pneumaticD. Motors

    Bhel 93KW 338v 310 A

    NGEF 160KW 675v 265 A

    Controls rheostatic and thyristor/ GTO

    Door operation electro pneumatic

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    An older metro rake

    Picture taken by Railfan Siddhartha Mukherjee

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    A new AC rake

    Picture taken by Railfan Saugata Sengupta at Park Street station

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    Ventilation system parameters

    Main parameters

    1. Max temperature (in stations) 30 C2. Max temperature (in tunnels) 32.8 C3. Max relative humidity (stations) 87%4. Max relative humidity (tunnels) 77%5. Max air velocity (stations) 3m/sec6. Max air velocity (tunnels) 2.5m/sec7. Air changes in station 29 times per hour8. Air changes in tunnels 12 times per hour

    The ventilation system is provided both at the platforms and in the tunnel mid sections

    of the tunnels. The ventilation system is divided and air is blown into the platform from

    both ends via ducts. There are ducts running below the platform which helps to remove

    the heat from the traction motors when the train stops at the station. The mid section

    fans are also used to exhaust the air from the tunnels.

    Air conditioning units are also provided at each station to keep the station air cool

    during the hot seasons.

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    Civil engineering concerns and planning

    Method of construction

    1. Reinforced concrete box 13.874 km2. Driven tunnel with C.I or R.C 1.232 km3. Elevated length 1.584 km4. Surface trough 1.372 km5. Total 18.062 km

    A box section

    Picture taken at Syambazar station showing the box section and the diaphragm

    wall with the ventilation fan access on the right

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    A circular tunnel section driven using compressed air method

    Starting of the circular bored tunnel section just after Syambazar station towards

    Belgachia side.

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    Platforms

    Length All platforms are of the same length 170m

    Height above rails 1.03m

    Type and width

    DumDum 2 side platform

    5.0m & 7.0m wide

    Central One island platform

    8.26m and 2 side ones

    with 4.13m

    Park street 2 side platform of 5.5

    m each

    Tollygunge 2 side platform 6.0m

    wide

    Other stations Island platform 10.26m

    and 8.26m and 1.03m

    Depth of station

    Underground station

    Depth of station from ground level

    Maximum at central 12.854 m

    Minimum at park street 6.920 m

    Elevated station

    Height above ground 6.975 m

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    Box tunnel dimensions

    Box section

    Tangent track 8.19 X 4.64 m internal

    Curved track 200m radius 9.04X4.15 m internal

    Bored tunnel

    Single track 5.10 m internal dia

    5.50 m external dia

    Horizontal alignment

    Minimum radius of curvature

    In block section 200m

    In stations 1000m

    Gradient abstract

    Steepest grade

    In running line 1 in 50

    In connection to depot 1 in 25

    Longest continuous length 0.726km

    of gradient in running line

    Level line longest length 0.627km

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    Vertical alignment

    Gradient

    a) Max running line gradient 2%b) Min track gradient between station 0.3c) Max track gradient in coach depot 4%d) Min track gradient at station 0.2%e) Max track gradient at station 0.2%

    Vertical curve

    Min radius of vertical curve 2000m

    Curve abstract

    Ratio of total curve length

    Tollygunge to Dumdum 38.84%

    Dumdum to Tollygunge 38.47%

    Average amount of curvature per Km

    Tollygunge to Dumdum 388 m

    Dumdum to Tollygunge 384.7m

    Track structure

    a) Main tracks are ballast less and consists of 60kg rails with elastic fastenings on concretebed.

    b) In the depots the tracks consists of 44.61 kg/m or 90R rails on sleepers resting onballasts.

    c) 1 in 10 points and crossings are on wooden sleepers resting in ballast in running linesand 1 in 8 for car depot.

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    Constructional planning

    Most of the underground tunnels were done by using cut and cover method.

    In cases where the tunnel had to go under a water body like near Syambazar shield tunnelingwas done.

    Shield tunneling was also used to tunnel under the Chitpur rail yards where the rail yard

    couldnt be closed for construction.

    Constructional considerations

    - Traffic Diversions- Environment- Washing of rake and Low Noise of Equipments- Utilities diversion- Safety Independent safety organization of Contractor/GC- Barricading & controlled Access of sites- Risk analysis before activity starts- Exhaustive Instrumentation

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    Tunnel dimensions

    The next step of planning was to predict the tunnel dimensions.

    The factors that were to be considered while planning tunnel dimensions are the size of carsand moving dimension and maximum permissible speed of the rakes.

    The dimensions were decided by Indian Rlys Schedule and also from world practices.

    The tunnels are chosen to allow rakes of 4.64 m in width and on the curved section the rakes

    have a tolerance up to 5.515m.

    The overall average internal dimension of the tunnel is 8.190 m X 4.640 m.

    In case of bored tunnel the diameter is 5.1 m for single track.

    The platform width is approximately 6m on average with maximum width of 10m and height of

    5.20m from the floor.

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    Cut and cover details

    Majority of the tunnel was under main city roads there was a problem and traffic had to

    be diverted and also utility like gas, power, water and telephones had to be diverted for

    construction.

    The majority of the utility was supported by struts and other support above the

    construction site while work continued underneath them.

    H-piles where sunk to support the brackets which in turn held up the struts to support

    the utility lines. Most of the excavation work was done manually and was thus very

    labor intensive. The gas lines had to be turned off or redirected during the construction

    and excavation phase.

    During the cut and cover design the main construction was done by constructing adiaphragm wall and then the excavation took place.

    The walls were approximately 10 m apart where there were normal parallel tracks and

    about 19m apart where there were stations.

    The excavation depth ranged from 12 m to 14 m.

    The diaphragm wall was held in place by struts of 3 to 5 levels depending on the depth

    and nature of the soil at the site.

    Different types of cut and cover used

    Diaphragm walls 12.687 km

    Sheet piles 0.365 km

    Sheet piles with timber 0.684 km

    Open cut 0.937 km

    Most of the construction was done with diaphragm wall constructio n

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    Machinery used to erect one section of wall per day

    Batching plants 1 No Dumpers 3 No Bentonite mixing units 1 No Vertical spindle type Bentonite pump 2 No (P & H) Tata 320 crane 2 No Grab Heavy 2 No Form tube 600 mm diameter 2 No Tremmie pipes 200 mm diameter with funnel 2 No Bailer 1 No Chisel 1 No Power Winch 1 No Tripod 1 No Scrapper 1 No Mobile Bentonite tank 1 No Welding plant 2 No Gas cutting unit 1 No

    These machines were used in the construction of only one section of the wall per

    day.

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    Details of the diaphragm wall

    The main excavations for the diaphragm wall was done by use of GRABS mounted on

    the cranes and were guided by telescopic guides. The length of each panel varied from 3

    m to 6 m and the depth varied from 16 m to 23 m. The excavated volume was filled with

    Bentonite slurry to prevent the collapse of the excavation. Then reinforcement cages

    were lowered and concrete of grade M-200 was poured into the excavation sealing the

    bottom of the cage. As the concrete is pumped in more and more the Bentonite is

    pumped out and is poured back in tanks for recycling and reuse.

    Some places where there had to openings made for ducts and passenger exits hollow

    cages were used which used a framework of beam and ducts for exposing the areas to

    be cut later.

    Problems faced in diaphragm wall construction

    Excessive cut The walls are constructed with a tolerance limit of 1 to 60 mostly the

    excavation went smoothly but in area near Bhowanipore (Km 12.50 to Km 13.50) the

    shapes of the walls are irregular due to the bad soil condition there were internal

    collapses and sometimes due to over grabbing of soil. Again at Km 13.10 to Km 13.80

    due to clayey soil and sand the soil could not hold its shape it collapsed into small

    pockets. Thus the walls in these locations are irregular and they had to be laboriously

    chiseled into shape.

    Jamming of end pipes There were steel cylindrical pipes made of sheet steel. These

    were to hold the cages in position when there would pouring of concrete. They were to

    be removed as the concrete settles in. in some case the pipes got jammed and concrete

    had to be poured in the pipe cores and they were made integral part of the diaphragm

    walls.

    Incomplete grabbing to the full length In some areas grabbing to the full length was

    unsuccessful due to the soil conditions. The grabbing had to be stopped when a

    compact sand layer was encountered. To overcome the problem jets were used to

    loosen up the sand but in most cases it was unsuccessful. The diaphragm walls were

    prematurely terminated and could not achieve full length.

    Segregation of concrete The concrete poured had heavy segregation and also there

    were blank pockets in the diaphragm wall. These problems were seen when excavation

    was being done and then concrete was poured into the blank pockets to seal them up.

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    Delays, risks and other problems faced by the project

    1. Delay in Approval of Detailed Project Report (DPR)2. Land Acquisition risks3. Design Risks4. Technology Selection Risks5. Approval and Permit Risks6. Financial and Investment Risks7. Political Risks8. Environment Related Risks9. Geo-technical Risks10.Major / Minor Accidents during Execution11.Unforeseen Heavy Rains12.Force Majeure Risks like Flood, Fire, Earthquake etc.13.Labor Agitation and Strikes14.Inflation Risk15.Delayed Payment from Client16.Delayed Payment to Subcontractor

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    Land acquisitions problems

    Since the metro was mostly built under the city the land acquisition was not a problem for the

    main running tracks.

    The land to be acquired for the construction of depots at Tollygunge and Dumdum was a issue

    but was sorted out.

    Land was also needed to be acquired for the construction of the station exits and ventilation

    shafts.

    The land acquired from different agencies and parties

    Land in acres

    Eastern railways 9.52

    Ministry of defense 1.702

    CMC & Baranagar municipality 74.81

    Govt of Bengal relief and rehabilitation

    department

    18.37

    Tollygunge club 21.56

    Private parties 178.00

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    Land acquisitions near DumDum for car shed construction

    Nearly 261.00 acres of land was acquired for the construction of the shed near dumdum

    station.

    Most of the land belonged to Eastern Railways and was a part of the track embankment.

    The rest of land belonged to CMC and Baranagar municipality and was used as a

    dumping ground.

    Land acquired for contracts depots

    Location Area

    Talla park 6258 sq m

    Desbandhu park 2823 sq m

    D N Mitra Square 2040 sq m

    Southern park 4098 sq m

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    Damage to surrounding structures and their precautions

    Settlement of ground during cut and cover is a common occurrence. It is a common

    practice to strengthen old building and monuments before the start of the construction.

    In the Tollygunge Esplanade section there were stray cracks due to soil settlement.

    In Bhawanipore area where the buildings are of old masonry and shallow foundations

    there were large cracks.

    Metro authority was responsible for these repairs.

    Soil settlement problems

    1. Subsoil profile and properties of soil.2. Shape and depth of excavation.3. Type and stiffness of support system.4. Sequence and method of construction.5. Time of construction

    In Kolkata the major factors were

    1. Spacing between the struts (specially 1st & 2nd)2. Time effect

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    Preconstruction precautions

    Before the excavation was started all inside the chosen zone of influence masonry

    buildings over 40 years old were surveyed and put under observation.

    Plumb lines and other monitoring equipment were installed at convenient locations to

    monitor sinking or leaning of buildings.

    Whenever they showed any signs of cracks the building was repaired and the soil was

    grouted.

    Station aesthetics

    Stations were designed so that they do not look dull and monotonous.

    The flooring is marble in most stations while the pillars are colorful tiles and designs.

    Murals were put up at different places to have a lively atmosphere.

    Historical painting replica and other lightings brighten up the atmosphere in the

    stations.

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    Bibliography

    1. The metro railway working literature2. Electrical maintenance manual of Kolkata metro3. Figures and plans of Kolkata metro4. Pictures of the rakes provided by Railfans Saugata Sengupta and Siddartha Mukherjee5. Wikipedia.org6. Kolkata metro railways official web site