Skip to main content

CLASSIFICATION OF TUNNEL

"Classification of Tunnel" play a main role to clarify shapes, differences & accountability in design of Tunnel Structure         

classification of tunnel
  

 Tunnel classification &Design of shape and size

  1. A tunnel classification may be for  foot or vehicular road traffic or for a canal.
  2. The central portion of rapid transit network are usually in the tunnel.Some tunnel are aqueduct to supply water for consumption or for hydroelectric station or sewers. 
  3. The shape of tunnel c/s is governed by nature and type of ground penetrated while size is largely controlled by the use to which tunnel is put
  4. Theoretically circular section is best for resisting either internal or external pressure and at the same time provides the greatest c/s area for least diameter

Shapes for tunnel classification
Shapes for tunnel cross section


Disadvantage

  1. But this circular section has disadvantage too .The top curved invert make it difficult in carrying railway tracks without considerable filling of the invert.
  2. The curved bottom also make it difficult for placing concrete of the invert.
  3. Now recent practice is to design tunneling rock with semicircular arch and vertical side walls .Tunnels in soft soils or ground re usually circular or horseshoe shaped as they have to withstand horizontal pressure.
  4. The horse shoe shape is a compromise section to minimize the inconvenience in lining the invert of circular section  

Procedure of work in Tunnel classification

In the wake of driving the tunnel are lined with timber masonry or concrete with suitable outlet to let out enclosed subsoil water behind the lining.Others items of work including the provision of ventilation during and after construction ,drainage and lighting if necessary are carried out to complete the construction of tunnel. 

Tunnel classification :

A/c to tunnel alignment

1)Offspur tunnel: To negotiate minor local obstacles ,very short in length
2)Saddle or base tunnel: Constructed in valley along natural,till slope not exceed ruling gradient
3)Slope tunnel: Constructed in steep hills.For economic and safe operation  
4)Spiral Tunnel: Provided in narrow valleys in forms of loops.It increase length of tunnel and avoid steep slope

SHAPES OF TUNNEL based on Tunnel Classification


SHAPES OF TUNNEL based on Tunnel Classification

1)Circular Section:

  • Offer great resistance to external pressure
  • Best theoretical section
  • Greatest c/s for least perimeter
  • For non cohesive soil
  • Suitable for sewer section
  • Difficult for concrete lining  

2)D section or Segmental Roof section

  • Section with arched roof  and straight sides
  • Most suited in rock tunnel
  • Suitable for subway or navigation tunnel
  • Slope of 1 in 24 is provided

3)Egg shaped section

  • Adopted for carrying sewage
  • Maintain self cleansing velocity of flow
  • Provide least c/s area@bottom

4)Elliptical section

  • Not used as traffic tunnel
  • Best for carrying water & sewage
  • Provided in soft rocks.An elliptical tunnel with height of section 1.6 times its the width has advantage over circular one as tensile stress in crown are reduced

5)Horseshoe Section

  • Most suitable for soft rock
  • Use for highway & Railway section
  • Best section for Traffic Purpose

6)Rectangular Section

  • Most suitable for Hard rock
  • For pedestrain traffic
  • This section are adopted if rcc caisson used for high tunnel 

    Influence of construction on shape in tunnel classification

  1. Conventional method suitable for driving horseshoe and flat arched section and less economical for circular 
  2. Shield method restrict almost to circular section
  3. Caisson method used for rectangular and circular section 
  4. Free face method for any shape
This how the tunnel  classification is being done to differentiate based on the categories used to adopt according to their usage.



Labels:

Comments

Post a Comment

Popular posts from this blog

METHOD OF TUNNELING IN SOFT ROCK

A Key article to learn " Method of Tunneling in Soft Rock " providing easy access to learn     Classification of  Method of tunneling in soft rock  1)Hard rock or fully self supporting 2)Soft soils  requiring temporary support during and after construction. Forepoling Method      Sequence of operation The shaft is sunk from surface to the grade level and properly protected with timber sheeting A wooden bent properly braced is setup a few inches from sheeting Small holes at close interval are drilled through the sheeting to facilitate section being cutout.The pattern of holes are 3 inches apart above the cap and other lines of holes below the cap A peice of sheeting is cutout along the top lines of the holes Forepoles or spiles consists of planks with wedge end are entered one at a time and driven through cut,into the ground for half their lengths with an upward inclination of 2 inch per foot. After all the roof and part of side spiles are driven to half their length a timber
Post a Comment
Read more

Previously Asked Question

Here you will get to know on which way we are going and how we will reach the destination 1. Pick up the explosive used for tunneling in soft rocks from the following :  A. Special gelatine B. Blasting gelatine C. Ammonia dynamite D. Semi-gelatine 2. Which one of the following tunnelling method is used for lying underground sewers ? A. Needle beam method B. German method  C. Army method D. English method 3. To attain the required shape of tunnel we use : A. Cutholes B. Chisels C. Erasers D. Trimmers 4. For initial surveys of tunnel, the following activities are involved :  a. Marking portal points with concrete pillars on the ground.  b. Marking tunnel obligatory points on the topograpical maps. c. Driving lines between the fixed obligatory points. d. Preliminary setting of the tunnel on the topograpical survey of Indian maps. The correct sequence of the activities are :  A. b,a,d,c B. a,b,c,d C. d,b,c,a D. c,b,d,a 5. If 'D' is a diameter of the tunnel in meters, then the thick
Post a Comment
Read more

How to Reduce Carbon dioxide from cement?

Get an overview to learn the Basics of properties of cement and know how the carbon dioxide is being removed                          ABSTRACT Concrete is the most widely used building material in the world because of its beauty, strength, and  durability, among other benefits. Concrete is used in nearly every type of construction, including  homes, buildings, roads, bridges, airports, and subways. And in an era of increased attention to the  environmental impact of construction, concrete performs well when compared to other building  materials. As with any building product, the production of concrete and its ingredients does require energy  that in turn results in the generation of carbon dioxide, or CO2. The amount of CO2 produced during  manufacturing and the net impact of using concrete as a building material is relatively small. The  following features of concrete construction help minimize its carbon footprint. Atmospheric concentrations of CO2 are expressed in units of parts per
Post a Comment
Read more