Transportation Engineering II UNIT - I

Transcription

1 Transportation Engineering II UNIT - I I. Components of a Permanent Way: A. Rails: Rails are the I-section members of a track laid in two parallel lines to provide a level surface for the movement of trains. Function of Rails: To provide a continuous and level surface for the movement of trains. To serve as a lateral guide for the wheels. To transmit the load to a large area of the formation through sleepers and ballast. To bear the stresses developed due to vertical loads transmitted to them. Types of Rails Double Headed Rail Bull Headed Rail Flat-footed Rail

2 Track Gauge: As per Indian Railways, it is the clear minimum distance between the running faces of two rails. Name of the Gauge Width (m) Broad Gauge (B.G.) Meter Gauge (M.G.) Narrow gauge (N.G.) Standard Rail Sections: Name of the Gauge Length (m) Broad Gauge (B.G.) 13 Meter Gauge (M.G.) 12 Narrow gauge (N.G.) 12 B. Sleepers Sleepers are the transverse ties laid to support the rails. Function of Sleepers: To hold the rails in their correct gauge and alignment To give a firm and even support to the rails To transfer the load evenly from the rails to a wider area. To provide the longitudinal and lateral stability to the permanent way. To act as a elastic medium between the rails and the ballast to absorb the vibrations caused by wheel loads.

3 Types of Sleepers Timber Sleepers Steel Sleepers Cast Iron Sleepers Prestressed Concrete Sleepers Sleeper Density - Number of Sleepers per unit length. Sleeper Density = (M+x) or (N+x) Where M or N = length of Rail, m X = Number which depends on factors such as Axle load and speed Type and section of rails Type and Strength of Sleepers Type of Ballast and depth of ballast cushion Nature of formation Comparison of different types of sleepers Characteristics Type of Sleeper Wooden Steel Cast Iron Concrete Service life (Years) Weight (Kg) Maintenance Cost High Medium Medium Low Gauge Adjustment Difficult Easy Easy No Gauge Adjustment possible Track Circuiting Best Difficult Difficult Easy Scrap Value Low Higher than Wood High No Scrap Value

4 C. Ballast Layer of broken stones, gravel, moorum or any other granular material placed and packed below and around sleepers. Functions of Ballast Provides a level and hard bed for the sleepers to rest on. Holds the sleepers in position. Transfers and distributes load from the sleepers to a large area of the formation. Provides effective drainage of the track. Provides elasticity and resilience to the track for proper riding comfort. Types of Ballast Types of Advantages Disadvantages Suitability Ballast Sand Ballast Good Drainage Causes Excessive Suitable for CI pot properties wear sleeper tracks Cheap Blows off easily Moorum Prevents water Very soft and turns Used as a sub- Ballast from percolating into dust ballast Cheap, if locally Initial Ballast for available new construction Coal Ash or Easily available Harmful for steel Used in yards and Cinder Cheap sleepers sidings Corrodes rail bottom and steel sleepers Broken Stone Hard and Durable Initial cost is high Used for high Ballast Economical in the speed tracks long run Other types of Ballast Brickbat Ballast

5 Kankar Stone Ballast Earth Ballast Sizes of Ballast Types of Sleepers Size of Ballast used Flat-Bottomed Sleepers 50 mm (2 ) (Concrete and Wooden Sleepers) Metal Sleepers 40 mm (1.5 ) Specification of Ballast (Indian Railways) = 25 mm to 65 mm Collection and Transportation of Ballast Collecting the ballast at ballast depots and transporting it to the site in ballast trains Collecting the ballast along the cess and placing the ballast on the track directly. D. Subgrade and Formation Subgrade is a naturally occurring soil which is prepared to receive the ballast. Formation is the prepared flat surface which is ready to receive the ballast along with sleepers and rails. Functions of formation: Provides a smooth and uniform bed for laying the track Bears the load transmitted to it from the moving load through the ballast Facilitates the drainage Provides the stability to the track

6 Formation can be in the shape of embankment or cutting Embankment : Rised soil bank constructed over the natural ground Cutting : Formation below the natural ground Width of formation of different tracks Gauge Single - line section Double line section Width of Width of Width of Width of embankment cutting (m) embankment cutting (m) (m) (m) B.G M.G N.G E. Rail fittings and Fastenings To hold the rails in their proper position in order to ensure the smooth running of trains. To join the rails together as well as fixing them with sleepers. Types of Fittings and Fastenings Purpose Joining rail to rail Joining rail to wooden sleepers Joining rail to steel sleepers Joining rail to cast iron sleepers Elastic fastenings Types of Fittings and Fastenings Fish plates, bolts and nuts Dog spikes, screw spikes and bearing plates Loose jaws, keys and liners Tie bars and cotters Elastic or Pandrol clip Fish plates, bolts and nuts

7 Pandrol Clip II. Engineering Surveys for Track Alignment Preliminary Investigations for a new railway line based on the study of ; Existing topo sheets and other maps of the area Published figures of trade and population of the area to be served Statistical data of existing railway lines in similar terrain in other areas Types of Engineering Surveys 1. Traffic Survey 2. Reconnaissance Survey 3. Preliminary Survey 4. Final location Survey 1. Traffic Survey A detailed study of the traffic conditions in the area to determine; The most promising route for the railways in the area The possible traffic the railway line will carry The standard of railway line to be followed 2. Reconnaissance Survey It is a rapid and rough investigation of the area with a view to determine the technical feasibility of the proposal as well as the rough cost of one or more alternatives to the new line. Survey Instruments used: Prismatic Compass

8 Aneroid Barometer Abney Level Binocular Pedometer 3. Preliminary Survey It consists of a detailed instrumental examination of the route to be selected as a result of the reconnaissance survey. Survey Instruments used: Theodelite Tacheometer Dumpy Level Plane Table Prismatic Compass 4. Final location Survey It is done to prepare working details and make accurate cost estimates for the chosen alignment. Project Report 1. Introduction Objective of the investigation and background Programme and methodology of the investigation Special features of the investigation 2. Characteristics of the project areas Topographical areas and geographical features Climate and Rainfall characteristics 3. Standard of construction Gauge Category of line Speed and load Ruling Gradient Degree of Curves Component of a Permanent way Type and depth of ballast Stations details Standard signaling and telecommunication Type of Traction 4. Route selection Data related to the various alternative routes examined 5. Project Engineering 6. Estimation of cost and Construction Schedule Cost estimate of preliminary expenses, land, formation, bridges, permanent way, station building and residential quarters, road crossings, station equipment, signaling and interlocking, rolling stock, etc. Modern surveying techniques Satellite Imagery

9 Aerial photographs Topographic maps Digital Terrain Modelling Photogrammetric plotted sheets Modern Geotechnology in aid of preparation of subgrade formation III. Railway Track Alignment Track Alignment refers to the direction and position of the centerline of the railway track. Horizontal Alignment: Straight Path of the Track, Curved Track, etc. Vertical Alignment: Gradients and Vertical Curves in a track Basic Requirements of an Ideal Alignment Purpose of the new railway line Strategic or Political Consideration Development of Backward Areas Shortening of Existing Railway line Connecting trade centres Integrated Development Economic Considerations Shortest Route Minimum Construction and Maintenance Cost Minimum Operating Expenses Maximum Safety and Comfort

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