Page 8 - SAPEM-Chapter-10-2nd-edition-2014

South African Pavement Engineering Manual
Chapter 10: Pavement Design

TABLE OF CONTENTS

1. Introduction ....................................................................................................................................... 1
2. Design Principles ................................................................................................................................ 5
2.1 Flexible Pavements ................................................................................................................. 5
2.2 Rigid Pavements ..................................................................................................................... 6
2.3 Block Pavements ..................................................................................................................... 7
3. Design Considerations ........................................................................................................................ 8
3.1 Road Category ........................................................................................................................ 8
3.2 Analysis and Structural Design Periods ...................................................................................... 9
3.3 Life Cycle Strategies .............................................................................................................. 10
3.4 Pavement Balance................................................................................................................. 12
3.4.1 Flexible Pavements ..................................................................................................... 12
3.4.2 Concrete (Rigid) Pavements ........................................................................................ 13
3.4.3 Concrete Block Pavements........................................................................................... 13
3.5 Pavement Behaviour ............................................................................................................. 13
3.5.1 Behaviour Under Loading ............................................................................................ 13
3.5.2 Load Sensitivity .......................................................................................................... 14
3.5.3 Long-Term Pavement Behaviour .................................................................................. 14
3.5.4 Materials .................................................................................................................... 20
3.6 Variability in Traffic Loading, Material Properties and Construction ............................................. 20
3.7 Environmental Considerations ................................................................................................ 20
3.7.1 Geology and Climate ................................................................................................... 21
3.7.2 Meteorological Environment ......................................................................................... 22
3.8 Practical Design Considerations .............................................................................................. 23
3.8.1 Drainage .................................................................................................................... 23
3.8.2 Compaction ................................................................................................................ 24
3.8.3 Variable Cross Sections and Paved Shoulders ................................................................ 24
3.9 Pavement Type Selection for New and Rehabilitated Pavements ............................................... 25
3.9.1 Traffic Accommodation................................................................................................ 25
4. Design Traffic Estimation ................................................................................................................. 27
4.1 Concepts and Terminology ..................................................................................................... 28
4.1.1 Legal Axle Loads......................................................................................................... 28
4.1.2 Axle Load Histograms ................................................................................................. 29
4.1.3 Standard Axles and Equivalent Standard Axles .............................................................. 30
4.1.4 E80s per Heavy Vehicle (E80/HV) ................................................................................. 33
4.1.5 Traffic Classes for Structural Pavement Design .............................................................. 34
4.2 Methods of Traffic Measurement and Classification .................................................................. 35
4.2.1 Traffic Measurement ................................................................................................... 35
4.2.2 Vehicle Classification ................................................................................................... 36
4.3 Daily Equivalent Traffic Parameters ........................................................................................ 36
4.3.1 Average Daily Traffic (ADT) ......................................................................................... 36
4.3.2 Average Annual Daily Traffic (AADT) ............................................................................ 36
4.3.3 Average Daily Equivalent Axles (ADE) ........................................................................... 37
4.3.4 Annual Average Daily Equivalent Axles (AADE) .............................................................. 37
4.4 Traffic Loading Variation ........................................................................................................ 38
4.4.1 Lane Distribution ........................................................................................................ 39
4.4.2 Adjustment for Short-Term Variation ............................................................................ 39
4.4.3 Adjustment for Long-Term Variation (Heavy Vehicle and E80/HV Growth Rates) .............. 42
4.5 Sequence of Events and Cumulative Design Traffic .................................................................. 44
4.6 Traffic Investigations for Pavement Design .............................................................................. 46
4.6.1 Published Results........................................................................................................ 47
4.6.2 Transportation Planning Models ................................................................................... 48
4.6.3 Project Specific Visual Observation ............................................................................... 48
4.6.4 Project Specific Traffic Surveys .................................................................................... 50
4.7 Design Traffic Calculation ...................................................................................................... 50
4.7.2 Sensitivity Analysis ...................................................................................................... 52
4.7.3 Geometric Capacity Limitations .................................................................................... 53

Preliminary Sections
Page v