TUNNELING EXPLORATION

PREPARED BY:-Husain Jamali-07

CONTENTSINTRODUCTIONWHY TUNNELS ARE CONSTRUCTEDHISTORY OF TUNNELSCLASSIFICATION OF TUNNELSHAPE OF TUNNELPROCESS FOR CONSTRUCTION OF TUNNELTUNNEL CONSTRUCTION METHODSADVANTAGES

INTRODUCTIONTunnels are underground or underwater

passageway, excavated through the surrounding soil/earth/rock enclosed except for entry and exit, commonly at each end.

A tunnel may be used for foot or vehicular road traffic, rail traffic, or for a canal.

Secret tunnels are constructed for military purpose.

Special tunnels, such as wildlife crossings, are built to allow wildlife to cross human made barriers safely.

To provide the shortest route through an obstacle.To provide the rapid or timely provision of facilities. To reduce the steep gradients especially while climbing up and then

climbing down rapidly i.e. in short distance.To avoid the expensive acquisition of valuable commercial land.To avoid the damage of built urban facilities, roads, pavements, etc.When the depth of ground cutting exceeds 20 m. To avoid the expensive maintenance cost in open cut area in sliding

lands, sinking or unstable grounds, snow-drifting grounds, ponding, marshy, soaked, etc areas.

WHY TUNNELS ARE CONSTRUCTED

The first ever tunnels were made by cavemen.

About 2180B.C., Babylonia tunnel was built under Euphrates river. It was 900m long, 3600mm wide and 4500mm high.

The largest tunnel built in ancient times was 1470m long, 7600mm wide and 9000mm high between Naples and Pozzuoli in 36B.C.

HISTORY OF TUNNELS

TYPES OF TUNNELSCLASSIFIED BY EXAMPLE OF TUNNELS

• Purpose Railway tunnels, metro system, highway tunnels, pedestrian tunnels, water tunnels, sewage tunnels, services tunnels, storage tunnels.

• Geological location / condition Rock tunnels, earth tunnels, and submerged tunnels.

• Cross-sectional shapes Rectangular shape, circular shape, elliptical shape, egg shape, horse shoe shape, and segmental shape.

The shapes of tunnel are usually determined by their purpose, ground conditions, construction method and/or lining materials.There are four shapes of tunnel:-

Circular shape tunnelElliptical shape tunnelHorseshoe shape tunnelOval/Egg shape tunnel

SHAPES OF TUNNEL

This type of section offers greater resistance to external pressure.

If ground is highly unstable, such as soft clay or sand, it is necessary to use circular section.

For carrying water and sewerage circular shape tunnels are used e.g. Aqueduct

CIRCULAR SHAPE TUNNEL

They are used in grounds compare to rock.

These tunnel serve as water sewage condition.

The smaller cross section at the bottom maintains the flow at the required self cleaning velocity.

Because of their narrow base they are not used as traffic tunnels.

ELIPTICAL SHAPE TUNNEL

These section have narrow cross-sections at bottom. They are best suited for carrying sewage.

They maintain self-cleansing velocity of flow of sewage both in dry and rainy seasons.

They resist external as well as internal pressure due to their circular walls.

These section of tunnels are difficult to construct

OVAL/EGG SHAPE TUNNEL

They are commonly used for rock tunnelling. These shape consist of horizontal roof

together with arched sides and a curved invert.

It has the advantage of utilising the compressive strength of concrete in resisting the loading by means of arch action and the base is wide enough for traffic.

They are most popular as traffic tunnels for road and railway routes.

They are also difficult to construct.

HORSESHOE SHAPE TUNNEL

The tunneling survey is an underground survey done for constructing a tunnel The survey done can be divided into 3 methods:-

Surface surveyTransferring the alignment undergroundLevels in tunnels

TUNNELING SURVEYS

Surface survey connects points representing each portal of a tunnel. A traverse connecting the portal points determines the azimuth, distance & differences in

elevation of each end of the proposed tunnel. Based on the local conditions and proposed length of the tunnel the methods of working

are adopted. It is always advisable that the survey is based on the suitable local coordinate system. The alignment is permanently referenced by a system of monuments within an area

outside each tunnel portal.

SURFACE SURVEY

A long tunnel excavation is carried inward from both ends. But vertical shafts are also sunk up to the required depth along the alignment of the tunnel at intermediate locations along the routes. The vertical alignment can be done by:-• Plumb bob• Optical collimator• Laser

A heavy plumb bob (5 to 10 kg) is suspended on either a wire of heavy twine. Oscillations of the bob can be controlled by suspending it in a pot with high viscosity oil. The bob is suspended from a removable bracket attached to the surface side of the shaft.

Optical plumbing becomes important with the increase in depth of internal shaft.A Laser equipment can be used to provide a vertical line of sight. The laser generates a

light beam of high intensity and of low angular divergence and can be projected over long distances since the spread of the beam is very small to provide a visible line for constant reference.

TRANSFERING THE ALIGNMENT UNDERGROUND

Laser Equipment

In transferring levels underground, little difficulty is encountered at the ends of the tunnel, but at the shaft use is made of• Steel tape• Chain• Constructed rods• Steel wires

Now a days EDMI is also used. But in all cases the main idea is to deduct the height of the shaft measured from the top of a benchmark of known value.

Depth measured by EDM

Depth measured by Steel tape

LEVELS IN TUNNEL

CONSTRUCTION METHODS OF TUNNELING

Classical methodCut and Cover methodDrill and Blast methodImmersed Tube methodSequential Excavation Method (SEM)Tunnel Boring Machines(TBM)Shield tunneling methodNew Austrian tunneling method

CLASSICAL METHODSupports are predominantly timber, and transportation of

muck is done on cars on narrow gauge tracks powered by steam.

Progress is typically in multiple stages i.e. progress in one drift, then support, then in another drift and so on.

The lining would be of brickwork.These craft-based methods are no longer applicable,

although some of their principles have been used in combination up to present day.

Some of the great tunnels were built with this method. In this method excavation is done by hand or simple drilling

equipment.

Cut and cover tunnelling is a common and well-proven technique for constructing shallow tunnels.

In this method trench is excavated and roofed over with an overhead support system strong enough to carry the load of what is to be built above the tunnel.

• Step one: Construction of diaphragm walls, piles, and decking.

• Step two: Excavation within the diaphragm walls, installing struts as work progresses.

• Step three: Construction of permanent floor slabs and walls.

• Step four: Fitting out the internal structures, backfilling, and reinstating the surface structures.

CUT AND COVER METHOD

This tunnelling method involves the use of explosives.

Drilling rigs are used to bore blast holes on the proposed tunnel surface to a designated depth for blasting.

Explosives and timed detonators are then placed in the blast holes.

Once blasting is carried out, waste rocks and soils are transported out of the tunnel before further blasting.

DRILL AND BLAST METHOD

CUT AND COVER METHOD

When a canal, channel, river, etc., needs to be crossed, this method is often used.

A trench is dug at the water bottom and prefabricated tunnel segments are made water tight and sunken into position where they are connected to the other segments.

Afterward, the trench may be backfilled with earth to cover and protect the tunnel from the water-borne traffic, e.g., ships, barges, and boats.

IMMERSED TUBE METHOD

Soil in certain tunnels may have sufficient strength such that excavation of the soil face by equipment in small increments is possible without direct support. This excavation method is called the sequential excavation method.

Once excavated, the soil face is then supported using shotcrete and the excavation is continued for the next segment.

The cohesion of the rock or soil can be increased by injecting grouts into the ground prior to excavation of that segment.

SEQUENTIAL EXCAVATION METHOD (SEM)

A tunnel boring machine (TBM), also known as a "mole", is a machine used to excavate tunnels with a circular cross section through a variety of soil and rock strata.

The TBM is designed to support the adjacent soil until temporary or permanent linings are installed.

TUNNEL BORING MACHINE (TBM)

Tunnel Boring Machine

In New Austrian Tunnelling Method (NATM) a flexible lining is employed. It transforms the rock or soil surrounding the tunnel profile from a load exerting

system into a load-carrying one. This is achieved through monitoring the behaviour of underground excavations and

the revision of support to obtain the most stable and economical lining.

NEW AUSTRIAN TUNNELING METHOD(NATM)

Construction tunnel follow NATM technology.webm

Construction Methods For Different tunnel shapes

Methods Circular Horseshoe Rectangular Elliptical

Cut and Cover Shield Driven

Bored Drill and Blast

Immersed Tube Sequential Excavation

Jacked Tunnel

FACTORS AFFECTING SELECTION OF TUNNELING METHOD

Geological and Hydrological conditionCross-section and length of continuous tunnelLocal experience and Time/Cost considerationShape of tunnelManaging the risk of variations in ground qualityLimits of surface disturbance

Linings are required in most tunnels, always in soft ground and frequently in rock.

They are required for two purposes: structurally to retain the earth and water pressure, and operationally to provide an internal surface appropriate to the function of the tunnel.

The principal materials for permanent lining of bored tunnels are:1. Brickwork, blockwork and masonry2. Insitu concrete3. Preformed segments4. Sprayed Concrete

TUNNEL LINING MATERIALS

Tunnel ventilation systems can be categorized into four main types. The four types are as follows:-• Natural Ventilation• Longitudinal Ventilation• Semi-Transverse Ventilation• Full-Transverse Ventilation

TUNNEL VENTILATION SYSTEM

A naturally ventilated tunnel is as simple as the name implies. The movement of air is controlled by meteorological conditions and the piston effect created by moving traffic pushing the stale air through the tunnel.

This effect is minimized when bi-directional traffic is present.

The meteorological conditions include elevation and temperature differences between the two portals, and wind blowing into the tunnel.

Another configuration would be to add a centre shaft that allows for one more portal by which air can enter or exit the tunnel.

Many naturally ventilated tunnels over 180 m (600 ft) in length have mechanical fans installed for use during a fire emergency.

NATURAL VENTILATION

Longitudinal ventilation is similar to natural ventilation with the addition of mechanical fans, either in the portal buildings, the center shaft, or mounted inside the tunnel.

Longitudinal ventilation is often used inside rectangular-shaped tunnels that do not have the extra space above the ceiling or below the roadway for ductwork.

Also, shorter circular tunnels may use the longitudinal system since there is less air to replace; therefore, the need for even distribution of air through ductwork is not necessary.

The fans can be reversible and are used to move air into or out of the tunnel.

LONGITUDINAL VENTILATION

Semi-transverse ventilation also makes use of mechanical fans for movement of air, but it does not use the roadway envelope itself as the ductwork.

A separate plenum or ductwork is added either above or below the tunnel with flues that allow for uniform distribution of air into or out of the tunnel.

This plenum or ductwork is typically located above a suspended ceiling or below a structural slab within a tunnel with a circular cross-section.

SEMI-TRANSVERSE VENTILATION SYSTEM

Full-transverse ventilation uses the same components as semi-transverse ventilation, but it incorporates supply air and exhaust air together over the same length of tunnel.

This method is used primarily for longer tunnels that have large amounts of air that need to be replaced or for heavily traveled tunnels that produce high levels of contaminants.

The presence of supply and exhaust ducts allows for a pressure difference between the roadway and the ceiling; therefore, the air flows transverse to the tunnel length and is circulated more frequently.

This system may also incorporate supply or exhaust ductwork along both sides of the tunnel instead of at the top and bottom.

FULLY-TRANSVERSE VENTILATION SYSTEM

Tunnels are more economical than open cuts beyond certain depths.Tunnels avoid disturbing or interfering with surface life and traffic

during construction.Tunnels prove to be cheaper than bridges or open cuts to carry public

utility services like water, sewer and gas.If tunnels are provided with easy gradients, the cost of hauling is

decreased.In case of aerial warfare and bombing of cities, the tunnels would

grant better protection as compared to bridges.

ADVANTAGES

MONITOR-MERRIMAC MEMORIAL TUNNEL BRIDGE

CASE STUDY

Project details:-Project name-- Monitor-Merrimac Memorial

tunnel-bridgeClient- Common wealth transportation board

(formerly state highway and transportation board)

Contractor – Virginia department of transportation

Distance between portals – 1.463 kmTime required - 7 years (1985 to 1992)Method of construction – Immersed tube methodTotal cost of project – 400 million dollars Location – Hampton roads Northfolk and partly in

SuffolkQty. of materials – 40,800 Tons of Concrete 21,800 Tons of Steel 3 Million of Tiles

• Traffic lanes -13 feet wide, 2.5-foot-wide ledges on either side of the roadway• Vertical clearance -16.5 feet (road to ceiling)• Uniqueness – Radio signals does not break

Project Detail:Client: Indian RailwayExecuting Agency: IRCON (Indian Railway

Construction Company Limited)Contractor: HCC (IRCON being the Client for

HCC)Project Location: Jammu & KashmirConstruction Period: 2005-2013Length of the Tunnel: 10.96 KmProject Cost: 1150 Crore No. Of tracks: 1 (Broad Gauge)Need of this Project: To reduce the travel time

and to sustain connectivity between Quazigund (Kashmir) and Banhihal (Jammu)

PIR PANJAL RAILWAY TUNNEL

TECHNICAL SPECIFICATION • Width: 8.4 meters• Height: 7.9 meters

CONSTRUCTION TECHNIQUES• New Austrian Tunnelling Method (NATM)• Drill & Blast• Road Header (relatively new machinery to

the Indian construction market) UNIQUENESS

• Tunnel is open throughout the year.• Underground drainage system to avoid

seepage in tunnel. • 3 m wide road in tunnel for maintenance,

emergency rescue & relief.• Mobile connectivity inside the tunnel.

Challenges faced:-• Presence of Soft geology.• Presence of fairly populated village above the alignment.

Project Details :Client : Norwegian governmentContractor : Norwegian Public Roads

administration Consultants : Foundation for Scientific and

Industrial ResearchConstruction Period : 1995-2000Tunnel Length : 24.5 kmTunnel Width : 9 m (30ft)Route : Aurdal – Laerdal (Norway)Project Cost : 1082 Million Norwegian kroneNo. of lanes : 2Location : Sognog Fjordane, Norway

LAERDAL TUNNEL

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