Highway Engineering

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Highway Engineering

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1-Geometric Design Introduction Design
Controls and Criteria for Geometric Design
Cross Section Design Sight Distance
Highway Vertical Alignment Horizontal
Alignment Design of Highway At-Grade
Intersections Grade Separations- and
interchanges Intersections
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• 2- STRUCTURE DESIGN
• 1- Introduction
• 2-Soil Engineering of Highways
• 3-Strength and Density of Soils
• 4-Pavement Components
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• 5-Highway Materials
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• 6-Flexible Pavement Design
• 7-Design of Rigid Pavements
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• Teaching and Learning Methods
• I- Methods
• Lectures
• Laboratory work.
• Tutorial problem solving
•  
• II- Instruments
• White board presentations
• Power Point presentations
• Interactive discussions

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• Schedule
• 1- Drop Quizzes
  Random
• 2- Solving Assignment Problems
  Every Week
• 3- Reports Presentations IT applications
• 
  As per lecturer schedule
• 4- Practical Works Reports Exam 13th to 15th
  Weeks
• 5- Mid-term written exams
  9th Week
• 6- Final written exams
  16th Week

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• Procedures Used
• I- Class Works
• Drop Quizzes.
• Solving Assignment Problems
• Reports.
• Practical Works.
• II- Written Exams
• Mid-term written exams.
• Final written exams.
  

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PART II STRUCTURE DESIGN OF HIGHWAYS
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CHAPTER 1INTRODUCTION

• The structure design of highway pavements
  comprises studying soil and paving materials
  their behavior under wheel loads, and the design
  of a pavement to carry that load under all
  climatic conditions

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General Definitions

• Right-of-way
• The right-of-way includes the following
• -The roadway (Traffic lanes and shoulders)
• -Drainage system (ditches, drains, culverts and
  
• bridges).
• Structures such as guard rails, side slopes,
• retaining walls, road signs, light signals
  and
• traffic control devices at intersections.

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Fig.1 Highway Structure (Right of Way)
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Pavement Types

• Two types of pavements are commonly used,
  flexible- and rigid pavements as shown in Figure
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• 1-Flexible Pavement Flexible pavements consist
  of a layered system in which wheel load effects
  are progressively reduced with depth. The
  flexible pavement structure consists of three
  layers, wearing course, base course and subbase.
  Under subbase laying the subgrade soil.

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• 2.Rigid Pavement Rigid pavements have relatively
  high resistance to bending such as Portland
  cements concrete pavements. The essential
  difference between the two types of pavements, is
  the manner in which they distribute the loads
  over the subgrade. High modules of elasticity
  for rigid pavement tend to distribute the load
  over a relatively wide area of soil. Thus, a
  major portion of the structure capacity is
  supplied by the slab itself

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Structural Components of Pavements

• 1) Surface course
• It is the top layer of the pavement directly in
  contact with traffic and has the following
  functions
• 1. It acts as a wearing surface which resists
  the abrasion and direct traffic effects and
  pressure.
• 2. It transmits the wheel loads to the base
  and subgrade without cracking or disintegration.
• 3. It reduces the tractive resistance of
  traffic.
• 4. It protects the base course from the action
  of water and climatic affect.

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• 2-Base Course
• It is a layer of high quality material below the
  wearing course through which the wheel loads are
  transmitted to the subgrade soil or subbase. The
  main functions of base course are
• 1.It acts as a foundation to the top surface
  course
• 2. It distributes the wheel load into a greater
  area
• 3. It protects the surface course against the
  volume changes of clay subgrades
• 4. It prevents the capillary rise.

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• Base courses are used under rigid pavements for
  various reasons as
• 1. control of pumping
• 2. control of frost action
• 3.drainage
• 4.control of the subgrade swelling.

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• 3- Subbase Course
• It is a layer of material may be used between
  base course and subgrade. The functions of
  subbase are
• 1-It drains the water and prevents the rise of
  capillary water, and subsequently protects the
  base course against the volume changes of
  subgrade.

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• 2. In soft clay subgrades, a sand or stabilized
  soil subbase must be used to prevent the working
  of clay subgrade into the voids of the crushed
  stone or gravel above it.
• 3. It transmits the wheel load to subgrade and
  protect it against frost action in freezing
  weather.
• Subbase are usually from granular materials as
  gravel, sand, crushed stones, and stabilized soil.

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• 4- Subgrade
• The subgrade is the top layer of embankment in
  fill soil or the top portion in the cut over
  which the pavement are placed. It has a depth of
  30-50 cm and acts as the foundation, and must be
  compacted to max. dry density by artificial means
  of compaction.

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• 1.The wheel load, W, is transmitted to the
  surface of pavement through the tire as a uniform
  vertical pressure Po . The stresses are spread
  through the pavement structure to produce a
  reduced vertical stress, P1 at the base surface,
  P2 at the subbase surface and P3 at the subgrade
  surface
• 2.The deflection in pavement structure leads to
  creating compressive and tensile stresses

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1.2. Traffic Loading

• The primary loading factors in flexible pavement
  design are
• 1. Amount of axle (and wheel) loads
• 2. Volume and composition of axle loads
• 3. Tire pressure and contact area.

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1.2.1. Wheel Loads

• 1. single and dual wheels
• 2. single and tandem axles.

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1.2.2.Volume and Composition of axle loads

• The asphalt Institute and also the AASHO
  recommend that the effects of traffic on
  structural design of the pavement be expressed in
  terms of the number equivalent single axle loads
  (ESAL).

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3.Tire Pressure and Contact Area

• The radius of contact area is as follows
• a ? P/Pt . ?
• where
• a radius of contact area
• P total tire load,
• Pt contact pressure.

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