Metro systems and engineering involves planning, developing, constructing, and operating metro rail networks within cities. Key aspects include feasibility studies, route planning, infrastructure like trains, tracks, power systems, tunnels, elevated structures, and stations. Construction methods for tunnels include cut-and-cover and boring machines. Viaducts are commonly used for elevated tracks, with precast segmental construction being a main approach that allows for efficient assembly of prefabricated concrete segments. Careful consideration is given to factors like population density, traffic, connectivity, and environment.

1. Metro systems and
engineering
PLANNING AND DEVELOPMENT
SHUBHAM SHARMA
Department of civil engineering
BGIET, SANGRUR

2. Introduction
 The Planning for a metro system involves various stages, such as feasibility studies, route planning, design,
construction, and operations.
 It requires careful consideration of factors like population density, traffic patterns, connectivity, and
environmental impact.
 It's an exciting process that aims to provide efficient and sustainable transportation options for cities.
 The development of metro systems involves the construction and expansion of underground or elevated rail
networks within cities.
 It aims to provide a convenient, efficient, and sustainable mode of transportation for urban areas. Metro
systems typically consist of stations, tracks, trains, and various infrastructure components.
 They play a crucial role in reducing traffic congestion, improving air quality, and enhancing connectivity within
cities.

3. Infrastructure
(a) Trains
 Most rapid transit trains are electric multiple units with lengths from three to over ten cars.
 Some urban rail lines are built to a loading gauge as large as that of main-line railways; others are built to
smaller and have tunnels that restrict the size and sometimes the shape of the train compartments.
(b) Tracks
 Most rapid transit systems use conventional standard gauge railway track. Since tracks in subway tunnels are
not exposed to rain, snow, or other forms of precipitation, they are often fixed directly to the floor rather than
resting on ballast, such as normal railway tracks.
 For elevated lines, another alternative is the monorail, which can be built either as straddle- beam monorails or
as a suspended monorail.

4. (c) Motive power
 Power for the trains, referred to as traction power, usually takes one of two forms: an overhead line, suspended
from poles or towers along the track or from structure or tunnel ceilings, or a third rail mounted at track level and
contacted by a sliding "pickup shoe".
 The practice of sending power through rails on the ground is mainly due to the limited overhead clearance of
tunnels, which physically prevents the use of overhead wires.
 The use of overhead wires allows higher power supply voltages to be used.
(d) Tunnels
 Underground tunnels move traffic away from street level, avoiding delays caused by traffic congestion and leaving
more land available for buildings and other uses.
 In areas of high land prices and dense land use, tunnels may be the only economic route for mass transportation.
 Cut-and-cover tunnels are constructed by digging up city streets, which are then rebuilt over the tunnel;
alternatively, tunnel-boring machines can be used to dig deep- bore tunnels that lie further down in bedrock.

5. (e) Elevated railways
 An elevated railway or elevated train is a rapid transit railway with the tracks above street level on a viaduct or
other elevated structure (usually constructed from steel, cast iron, concrete, or bricks).
 The railway may be broad-gauge, standard-gauge or narrow- gauge railway, light rail, monorail, or a
suspension railway.
 Elevated railways are normally found in urban areas where there would otherwise be multiple level crossings.
Usually, the tracks of elevated railways that run on steel viaducts can be seen from street level.
 Elevated railways are a cheaper and easier way to build an exclusive right-of-way without digging expensive
tunnels or creating barriers. In addition to street level railways they may also be the only other feasible
alternative due to considerations such as a high water table close to the city surface that raises the cost of, or
even precludes underground railways (e.g. Miami).

6. (f) Stations
 Stations function as hubs to allow passengers to board and disembark from trains.
 They are also payment checkpoints and allow passengers to transfer between modes of transport, for instance
to buses or other trains.
 Access is provided via either island- or side platforms.
 Underground stations, especially deep-level ones, increase the overall transport time: long escalator rides to the
platforms mean that the stations can become bottlenecks if not adequately built.
 Some underground and elevated stations are integrated into vast underground or skyway networks respectively,
that connect to nearby commercial buildings.
 The deepest station in the world is Arsenalna station in Kyiv, Ukraine (105.5 m).

7. Construction methods
 Cut and Cover method
 In a cut and cover tunnel, the structure is built inside an excavation and covered over with backfill material when
construction of the structure is complete.
 is used when the tunnel profile is shallow and the excavation from the surface is possible, economical, and
acceptable.
 is used for underpasses, the approach sections to mined tunnels and for tunnels in flat terrain or where it is
advantageous to construct the tunnel at a shallow depth.
 Two types of construction are employed to build cut and cover tunnels; bottom-up and top-down.

8.  These construction types are described in more detail below.
 Figure is an illustration of cut and cover tunnel bottom-up and top-down construction.
 Figure (a) illustrates Bottom-Up Construction where the final structure is independent of the support of
excavation walls.
 Figure (b) illustrates Top-Down Construction where the tunnel roof and ceiling are structural parts of the
support of excavation walls.

9.  For depths of 30 to 40 feet (about 10 m to 12 m), cut-and-cover is usually more economical and more practical
than mined or bored tunnelling.
 The cut-and-cover tunnel is usually designed as a rigid frame box structure.
 In urban areas, due to the limited available space, the tunnel is usually constructed within a neat excavation line
using braced or tied back excavation supporting walls.
 Wherever construction space permits, in open areas beyond urban development, it may be more economical to
employ open cut construction.
 Where the tunnel alignment is beneath a city street, the cut-and-cover construction will cause interference with
traffic and other urban activities.
 This disruption can be lessened through the use of decking over the excavation to restore traffic.
 While most cut-and-cover tunnels have a relatively shallow depth to the invert, depths to 60 feet (18 m) are not
uncommon; depths rarely exceed 100 feet (30 m).

10. Conventional bottom-up construction
 As shown in figure, in the conventional “bottom-up” construction, a trench is excavated from the surface within
which the tunnel is constructed and then the trench is backfilled and the surface restored afterward. The trench
can be formed using open cut (sides sloped back and unsupported), or with vertical faces using an excavation
support system. In bottom-up construction, the tunnel is completed before it is covered up and the surface
reinstated.

12.  Advantages of Bottom-up construction includes :
 It is a conventional construction method well understood by contractors.
 Waterproofing can be applied to the outside surface of the structure.
 The inside of the excavation is easily accessible for the construction equipment and the delivery, storage and
placement of materials.
 Drainage systems can be installed outside the structure to water or divert it away from the structure.
 Disadvantages of bottom-up construction include:
 Somewhat larger footprint required for construction than for top-down construction.
 The ground surface can not be restored to its final condition until construction is complete.
 Requires temporary support or relocation of utilities.
 May require dewatering that could have adverse affects on surrounding infrastructure.

13. Top-Down Construction
 With top-down construction in figure, the tunnel walls are constructed first, usually using slurry walls, although
secant pile walls are also used.
 In this method the support of excavation is often the final structural tunnel walls. Secondary finishing walls are
provided upon completion of the construction.
 Next the roof is constructed and tied into the support of excavation walls. The surface is then reinstated before
the completion of the construction.
 The remainder of the excavation is completed under the protection of the top slab.
 Upon the completion of the excavation, the floor is completed and tied into the walls. The tunnel finishes are
installed within the completed structure.
 For wider tunnels, temporary or permanent piles or wall elements are sometimes installed along the centre of
the proposed tunnel to reduce the span of the roof and floors of the tunnel.

16.  Top-down construction offers several advantages in comparison to bottom-up construction:
 It allows early restoration of the ground surface above the tunnel . The temporary support of excavation walls are used
as the permanent structural walls.
 The structural slabs will act as internal bracing for the support of excavation thus reducing the amount of tie backs
required It requires somewhat less width for the construction area.
 Easier construction of roof since it can be cast on prepared grade rather than using bottom forms.
 It may result in lower cost for the tunnel by the elimination of the separate, cast-in-place concrete walls within the
excavation and reducing the need for tie backs and internal bracing.
 It may result in shorter construction duration by overlapping construction activities

17. Disadvantages of top-down construction include:
 Inability to install external waterproofing outside the tunnel walls.
 More complicated connections for the roof, floor and base slabs.
 Potential water leakage at the joints between the slabs and the walls.
 Risks that the exterior walls (or centre columns) will exceed specified installation tolerances and
extend within the neat line of the interior space.
 Access to the excavation is limited to the portals or through shafts through the roof.
Limited spaces for excavation and construction of the bottom slab.

18. metro stations/subway stations
 A metro station or subway station is a train station for a rapid transit system, which as a whole is usually called a
"metro" or "subway".
 A station provides a means for passengers to purchase tickets, board trains, and evacuate the system in the case of
an emergency.
 Location of metro stations
 The location of a metro station is carefully planned to provide easy access to important urban facilities such as
roads, commercial centres, major buildings and other transport nodes.
 Most stations are located underground, with entrances/exits leading up to ground or street level.
 The bulk of the station is typically positioned under land reserved for public thoroughfares or parks.
 Placing the station underground reduces the outside area occupied by the station, allowing vehicles and
pedestrians to continue using the ground-level area in a similar way as before the station's construction.
 This is especially important where the station is serving high-density urban precincts, where ground-level spaces
are already heavily utilised.

19. Entrance exit leading to ground level
 At street level the logo of the metro company marks the entrances/exits of the station.

20. Type of metro station based on
construction
 Shallow column station
 Deep column station
 Pylon station
 Single-vault station
 Cavern station

21. Shallow column station
 The shallow column station is a type of construction of
subway stations, with the distinguishing feature being an
abundance of supplementary supports for the
underground cavity.
 Most designs employ metal columns or concrete and steel
columns arranged in lines parallel to the long axis of the
station.
 Stations can be double-span with a single row of columns,
triple-span with two rows of columns, or multi-span.

22. Deep column station
 A deep column station is a type of subway
station consisting of a central hall with two side
halls connected by ring-like passages between a
row of columns.
 Depending on the type of station, the rings
transmit load to the columns either by "wedged
arches" or through Purlins, forming a "column-
purlin complex".
 The fundamental advantage of the column
station is the significantly greater connection
between the halls, compared with a pylon
station.

23. pylon station
 The pylon station is a type of deep underground
subway station.
 The basic distinguishing characteristic of the pylon
station is the manner of division of the central hall from
the station tunnels.
 The pylon station consists of three separate halls,
separated from each other by a row of pylons with
passages between them.
 The independence of the halls allows the architectural
form of the central and side halls to be differentiated.
 Building stations of the pylon type is preferable in
difficult geological situations, as such a station is better
able to oppose earth pressure.

24. Single vault station
 The construction of a single-vault station
consists of a single wide and high underground
hall, in which there is only one vault.
 The first single-vault stations were built in
Leningrad in 1975: Politekhnicheskaya and
Ploshchad Muzhestva.

25. Cavern station
 The cavern station is a metro station built
directly inside a cavern.
 Many stations of the Stockholm Metro,
especially on the Blue Line, were built in man-
made caverns; instead of being enclosed in a
tunnel, these stations are built to expose the
bedrock in which they are excavated.
 The Stockholm Metro also has a depot facility
built in a cavern system.

26. Viaduct
 Viaducts in metro systems are elevated structures that support the tracks and allow trains to travel above
ground level. They are commonly used in urban areas where space is limited or where the terrain requires
elevated tracks. Viaducts are typically constructed using various methods, including precast segmental
construction, which involves assembling precast segments to form the bridge spans. This method offers
advantages such as faster construction, reduced disruption to traffic, and improved quality control. Viaducts
are crucial components of metro systems as they provide efficient and reliable transportation options in
densely populated areas.
 A viaduct is a specific type of bridge that consists of a series of arches, piers or columns supporting a long
elevated railway or road. Typically a viaduct connects two points of roughly equal elevation, allowing direct
overpass across a wide valley, road, river, or other low-lying terrain features and obstacles. Viaducts are
commonly used in many cities that are railroad hubs, such as Chicago, Atlanta, Birmingham, London and
Manchester. These viaducts cross the large railroad yards that are needed for freight trains there, and also
cross the multi-track railroad lines that are needed for heavy rail traffic. These viaducts provide grade
separation and keep highway and city street traffic from having to be continually interrupted by the train
traffic. Likewise, some viaducts carry railroads over large valleys, or they carry railroads over cities with many
cross-streets and avenues. Many viaducts over land connect points of similar height in a landscape, usually by
bridging a river valley or other eroded opening in an otherwise flat area.

27.  Often such valleys had roads descending either side
(with a small bridge over the river, where necessary)
that become inadequate for the traffic load,
necessitating a viaduct for "through" traffic.
 Such bridges also lend themselves for use by rail traffic,
which requires straighter and flatter routes. Some
viaducts have more than one deck, such that one deck
has vehicular traffic and another deck carries rail traffic.
 Where a viaduct is built across land rather than water,
the space below the arches may be used for businesses
such as car parking, vehicle repairs, light industry, bars
and nightclubs

28. Construction methods - viaducts
 When it comes to construction methods for viaducts for metro, there are a few common ones.
 Some methods include precast segmental construction, balanced cantilever construction, and incremental
launching.
 Each method has its own advantages and considerations
Precast segmental construction balanced cantilever construction incremental launching method

29. Precast segmental construction
 It involves assembling a structure using precast concrete segments. This method is often used in the construction of
viaducts for metro systems due to its efficiency and cost-effectiveness. Here's how precast segmental construction is
typically applied to viaducts:
1. Segment Design and Manufacturing:
 Each segment of the viaduct is designed to precise specifications.
 Precast segments are manufactured off-site in a controlled environment, ensuring high quality and consistency.
2. Transportation to Site:
 Precast segments are transported to the construction site using trucks or other transportation methods.
3. Segment Erection:
 Cranes are used to lift and place the precast segments into position.
 Segments are typically joined together using post-tensioning techniques. Cables or tendons are inserted through ducts in
the segments and then tensioned to provide additional strength and stability.

30. 4. Pier Construction:
 Piers are constructed on top of the precast segments.
 These piers support the horizontal beams or girders that carry the load of the metro tracks.
5. Girder Installation:
 Horizontal beams or girders are installed on top of the piers to create the main framework of the viaduct.
 Precast concrete girders are commonly used in this construction method.
6. Track Installation:
 Metro tracks are then laid on the installed beams or girders.
 Track fastenings and other necessary components are installed.
7. Repetition of Segments:
 The process of segment erection, pier construction, and girder installation is repeated until the entire length of the viaduct is
completed.

31. 8. Deck Construction:
 The deck is constructed on top of the girders to provide a stable surface for the trains to travel on.
9. Finishing Touches:
 Additional components such as parapets, guardrails, and other safety features are added.
10. Testing and Commissioning:
 The constructed viaduct undergoes thorough testing before being commissioned for regular metro operations.
 Precast segmental construction offers advantages such as faster construction timelines, reduced on-
site labour requirements, and improved quality control. It's a popular method for viaducts in metro
systems where minimizing disruptions to existing transportation networks is crucial.

32. Balanced Cantilever Method
 This method is used for constructing bridges with span 50 to 250m. The bridge constructed can either be cast-in-
place or precast.
 Here, the segments are attached in an alternative manner at opposite ends of the cantilevers supported by piers.
 This is the best choice for the construction of long span length bridges, irregular length, and cable-stayed
bridges.

33. Incremental Launching Method
 The Incremental Launching Method (ILM) method of bridge construction is employed mainly for the
construction of continuous concrete bridges or steel girder bridges.
 The method performs the procedure in increments.
 With this method of construction, the bridge deck is built in sections by pushing the structure outwards from
an abutment towards the pier.
 The ILM method can be used for bridge decks with a length greater than 250m.

34. Span by Span Casting method of
Bridge Construction:
 Span by span is a relatively new construction technique historically associated with cantilever construction but the
advancement in external prestressing has enabled its own potential use to grow.
 Today it is considered to be the most economic and rapid method of construction available for long bridges and
viaducts with individual spans upto 60m.
 Decks are begun at one abutment and constructed continuously by placing segments to the other end of the bridge.
Segments can be positioned by either a temporary staying mast system through more commonly using an assembly
truss.
 Before segments are placed the truss with sliding pads is braced over two piers.
 Depending on the bridge location the segments are then transported by lorry or barge to the span under
construction.

35.  Each segment is then placed on the sliding pads and slid into its position. Once all segments are in position the pier
segment is then placed.
 The final stage is then begun by running longitudinal prestressing tendons through segments ducts and prestressing
entire span. Deck joints are then cast and closed and ducts grouted.
 When the span is complete the assembly truss is lowered and moved to the next span where construction cycle begins
until the bridge is complete.

36. Metro depots
 Metro depots are essential facilities for metro systems. They serve as maintenance and storage areas for metro
trains. Depots typically have various sections, including workshops for maintenance and repair, storage yards
for parking and maintaining trains, and administrative buildings for managing operations. These depots are
strategically located along the metro lines to ensure efficient maintenance and service of the trains. They play
a crucial role in keeping the metro system running smoothly.
 Metro trains are typically serviced in depots on a regular schedule, which can vary depending on the specific
metro system and the type of maintenance required. Regular maintenance tasks, such as inspections, cleaning,
and minor repairs, may be performed daily or on a frequent basis to ensure the trains are in optimal condition.
More extensive maintenance, such as major repairs or overhauls, may be scheduled at regular intervals, such
as every few months or annually. The goal is to maintain the trains' reliability, safety, and performance. The
specific maintenance schedule and procedures are determined by the metro system operators and
manufacturers to meet industry standards and ensure the smooth operation of the trains.

37. Commercial and service building
 There are commercial and service buildings integrated into the stations or nearby areas. These buildings can include
retail shops, restaurants, cafes, convenience stores, and service facilities like ticket offices, customer service centres, and
restrooms. They provide additional amenities and services for passengers, making their metro experience more
convenient and enjoyable. Some examples of metro systems with commercial and service buildings include the Grand
Central Terminal in New York City and the Shinjuku Station in Tokyo.
 In metro stations you can find shopping malls or retail centers within or adjacent to the stations. These malls often have a
variety of stores, including clothing shops, electronics stores, bookshops, and more. Additionally, there may be food
courts or restaurants where commuters can grab a bite to eat. Some metro systems even have commercial office spaces
or hotels connected to the stations. These buildings provide convenience and services for commuters and enhance the
overall experience of using the metro system.
 Commercial and service buildings in metro systems offer several benefits. Firstly, they provide convenience to commuters
by offering a range of amenities such as retail shops, restaurants, and cafes. This allows passengers to grab a quick bite to
eat or shop for essentials without having to leave the station or travel far. Secondly, these buildings generate revenue
through rent and advertising, which can contribute to the financial sustainability of the metro system. Additionally, they
help create a vibrant and lively atmosphere, making the overall commuting experience more enjoyable.

38. Site investigations Types:
 Site investigations have been carried out to gather further information about ground and environmental conditions ahead of
construction.
1. Arborist assessments:
 Arborist assessments were carried out on a number of trees along the project alignment. Arborist assessments documented
the size and health of trees, their proximity to the project alignment and assessed the potential impact of the project on
nearby trees.
 The information gathered from the tree assessments informed project planning, including identifying and minimising potential
impacts to trees from construction and operation of the new rail line.
2. Basement Surveys:
 We identified a number of properties along the proposed project alignment that have basements.
 To understand how the project's underground tunnels and stations will integrate with below ground features such as
basements, we needed to undertake a visual inspection and 3D laser scan to ensure we fully understood the underground
landscape in which the project will be built.
 The information gathered through these studies helped inform project designs and proposed construction methodologies.

39. 3. Geotechnical Investigations:
 Just like the landscape above ground has features like hills, rivers and different types of soil, underground portion of every
city has its own landscape. This landscape includes a variety of geological conditions such as hard rock, softer rocks and
clays, silt deposited by rivers and groundwater.
 Geotechnical investigations help us to gain a greater understanding of local geological conditions and assisted in planning
how the Metro Tunnel will be built and involved drilling into the ground to obtain rock and soil samples.
 We are undertaking a range of investigations across the project corridor to better understand local ground conditions and
the location of underground services ahead of the start of major construction.
4. Ground surface surveys:
 The ground surface survey is a low-impact activity designed to help us understand the way electrical currents may travel
through certain ground conditions. The survey involves laying a 50-100 metre line of metal probes at several locations
listed below.
 The small metal probes will be inserted approximately 5cm into the soil at regular intervals, and will collect data by
releasing a low electrical current into the soil. A meter box is set-up to measure the resistance of the electrical current
through the ground.
 This survey needs to be undertaken in a number of parkland areas across the alignment as the probes cannot be inserted
into asphalt. This method is commonly used in public spaces to test soil profile and density.

40. 5. Groundwater monitoring:
 Groundwater monitoring inspections were conducted at a select number of pre-existing boreholes and at some of our newly
newly established boreholes to determine how construction activities could potentially influence groundwater sources.
 Groundwater monitoring is undertaken by a specialist consultant who performs a visual inspection by lifting the lid of the
well and taking a photo. Once the lid is replaced, the consultant leaves the property.
6. Laser scanning
 3D laser scanning took place at various locations along the project alignment. Laser scanning technology allowed the
project to catalogue existing site conditions using photographs taken from a number of viewpoints to build a 3D model of
the current environment.
 Laser scanning helps to determine potential impacts from construction and operation of the new rail line on the existing
environment.
 3D laser scanning involves a team of two people:
 Assessing the current urban environment in the vicinity of the rail tunnel entrances. A scanner mounted on a tripod which
takes a series of images over a 15 minute period in each location.

41. 7. Level settlement monitoring:
 Level settlement monitoring helps us to understand horizontal and vertical ground movements along the
alignment during construction.
 The data gathered forms a baseline, allowing us to identify if any changes to ground levels have occurred
during construction.
 Level Settlement Monitoring is a standard activity undertaken in advance of any major construction project.
8. Noise and Vibration
 The purpose of the studies is to understand existing levels of noise and vibration in the urban environment.
 This helps us to:
 Assess current and future noise and vibration levels in these areas.
 Inform project designs and strategies to minimize potential impacts from noise and vibration during
construction and operation of the new rail line.

42. 9. Service Investigations
 Investigations were undertaken to identify the location of underground services in areas along the project alignment.
 These investigations included two activities, preliminary service investigations and trenching activities.
1. Preliminary Service Investigations
 Preliminary service identification involves the use of electronic detection equipment to confirm the location of
underground services in the area.
2. Trenching activities
 Trenching activities helps confirm the location of underground services
10. Visual inspections
 A team of assessors undertook a range of visual inspections to document the existing conditions of areas along the
project alignment.
 The assessors will took photographs to document the current condition of the urban environment.