Transportation Engineering Study Material for SSC Junior Engineer (Civil) Exam PDF - CivilEnggForAll Exclusive

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CONTENTS

  • CLASSIFICATION OF ROADS
  • ROAD PATTERNS
  • PLANNING SURVEYS
  • HIGHWAY PLANNING IN INDIA
  • SURVEYS
  • HIGHWAY CROSS-SECTION ELEMENTS
  • SIGHT DISTANCE
  • SUPERELEVATION
  • HORIZONTAL TRANSITION CURVES
  • HIGHWAY MATERIALS
  • SUB-GRADE SOILS
  • STONE AGGREGATES
  • TESTS ON ROAD AGGREGATES
  • BITUMINOUS MATERIALS
  • TESTS ON BITUMEN
  • CUTBACK BITUMEN
  • HIGHWAY PAVEMENTS
  • STRENGTH CHARACTERISTICS OF PAVEMENTS

CLASSIFICATION OF ROADS

  • Based on weather. 
    • All-weather roads 
    • Fair-weather roads 
  • Based on the type of carriage way or road  pavement. 
    • Paved roads 
    • Unpaved roads (e.g. earth roads and gravel  roads) 
  • Based on the type of pavement surfacing  provided. 
    • Surfaced roads 
    • Unsurfaced roads 
  • Based on method of construction. 
    • Traffic volume (vehicle): 
      • Heavy traffic road; 
      • Medium traffic road, 
      • Light traffic roads 
    • Load transported or tonnage: 
      • Class I or Class A (tonnes/day), 
      • Class II or Class B etc. 
    • Location and function.

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MODIFIED CLASSIFICATION OF ROAD SYSTEM (Given by Third Road Development Plan  1981-2001) 

  1. Primary system. 
    1. Expressway 
    1. National Highway (NH) 
  2. Secondary system. 
    1. State Highway (SH) 
    1. Major District Roads (MDR) 
  3. Tertiary system or Rural roads. 
    1. Other District Road (ODR) 
    1. Village Road (VR)

ROAD PATTERNS

  • Rectangular or block pattern: Adopted in the  city roads of Chandigarh 
  • Radial or star and block pattern
  • Radial or star and circular pattern: e.g.  Connaught place 
  • Radial or star and grid pattern: Nagpur road  plan formulae were prepared assuming star and  grid pattern 
  • Hexagonal pattern 
  • Minimum travel pattern
Hexagonal Pattern
Radial or Star and Grid Pattern

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SURVEYS 

Engineering Surveys for Highway Location

Before a highway alignment is finalised in highway  project, the engineering surveys are to be carried out.  Survey stages.  The survey may be completed in four stages. 

1.  Map study 

2.  Reconnaissance 

3.  Preliminary survey. 

(a) Conventional approach by preliminary  survey.  It is carried out in following steps: 

  • Primary traverse 
  • Topographical features 
  • Levelling work 
  • Drainage studies and Hydrological data 
  • Soil survey
  • Material survey 
  • Traffic survey 
  • Determination of final centre line.

(b) Modern rapid approach by aerial survey. 

4. Final location and Detailed survey: The alignment finalised at the design office after  the preliminary survey is to be first located on the  field by establishing the centre line. Next detailed  survey should be carried out for collecting the  information necessary for the preparation of plans  and construction details for the highway project.  The data collected during the detailed survey should  be elaborate and complete for preparing detailed  plans, design and estimates of the project.

SIGHT DISTANCE

It is the length of road visible ahead to the driver at  any instance.  Three sight distance situations are considered in the  design: 

(1) Stopping Sight Distance (SSD) – The minimum sight distance available on a  highway at any instant or spot should be of  sufficient length to stop a vehicle travelling at  design speed, safely without collision with any other  obstruction. 

(2) Over taking Sight Distances (OSD) – The minimum distance open to the vision of the  driver of a vehicle intending to overtake slow  vehicle ahead with safety against the traffic of  opposite direction is called minimum overtaking  sight distance (OSD) or safe passing sight distance. 

(3) Sight Distance at Intersections – The IRC recommends that at uncontrolled  intersections, sufficient visibility should be  provided such that the sight distance on each road  is atleast equal to the SSD corresponding to the  design speed of the road.  IRC recommends that a minimum visibility  distance of 15 m along the minor road and a  distance of 220, 180, 145 and 110 m along the major  road corresponding to design speeds of 100, 80, 65  and 60 kmph. respectively may be provided.

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SUPERELEVATION

In order to counteract the effect of centrifugal force  and to reduce the tendency of vehicle to overturn or  skid, outer edge of the pavement is raised with respect  to the inner edge, thus providing a transverse slope  throughout the length of horizontal curve. This  transverse inclination to the pavement surface is called  superelevation or cant or banking. 

HORIZONTAL TRANSITION CURVE

Functions of the transition curves in the horizontal  alignment of highway: 

  • To introduce gradually the centrifugal force  between tangent point and the beginning of the  circular curve, avoiding a sudden jerk on the  vehicle. 
  • To enable the driver turn the steering gradually  for his own comfort and security. 
  • To enable gradual introduction of the designed  superelevation and extra widening of pavement  at the start of the circular curve. 
  • To improve aesthetical appearance of the road.

SUB-GRADE SOIL 

It is an integral part of the road pavement structure.  The main function of the sub-grade is to give adequate  support to the pavement and for this, the subgrade  should possess sufficient stability under adverse  climate and loading conditions. 

STONE AGGREGATES

Aggregates form the major portion of pavement  structure and they form the prime materials used in  pavement construction. 

Desirable properties of road aggregates. 

  • Capable of withstanding high stresses in addition  to wear and tear. 
  • Aggregate should be hard enough to resist the wear  due to abrasive action of traffic. 
  • Aggregate should be able to resist impact produced  by heavily loaded steel tyred vehicles. 
  • The stone used in the pavement construction  should be durable and should resist disintegration  due to action of weather. 
  • Too flaky and too much elongated aggregate  should be avoided as far as possible in road  construction. 
  • The aggregates used in bituminous pavements  should have less affinity with water when  compared with bituminous materials.

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TEST FOR ROAD AGGREGATES

  • Crushing test: The aggregate crushing value  provides a relative measure of resistance  to crushing under gradually applied compressive  load. 
    • Abrasion test: Abrasion tests are carried out to  test the hardness property of stones and to decide  whether they are suitable for the different road  construction works.
    • Impact test: A test designed to evaluate the  toughness of stone or resistance of the aggregates  to fracture under repeated impacts is called  impact test. The aggregate impact value indicates  a relative measure of resistance of aggregate to  impact, which has a different effect than the  resistance to gradually increasing compressive  stress. 
    • Soundness test: Soundness test is conducted to  study the resistance of aggregates to weathering  action. 
    • Shape test
      • Flakiness index: It is the percentage by weight  of aggregate particles whose least dimension/thickness is less than 0.6 of their mean dimension. This test is applicable for sizes larger than  6.3 mm 
      • Elongation index: It is the percentage by  weight of particles whose greatest dimension or  length is greater than 1.8 times their dimensions.  This test is not applicable for size smaller than  6.33mm. 
    • Specific gravity and Water absorption  test: The specific gravity of rocks vary from  2.6 to 2.9. Rock specimens having more than  0.66% water absorption are considered  unsatisfactory unless found acceptable based on  strength tests. 
    • Bitumen adhesion test: Adhesion problem  of bitumen with aggregate are observed due  to the pressure of water. Water liking aggregates  are called hydrophiopic aggregate and they have  greater alteration of bitumen than water.
Differences between Bitumen and Tar

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