ABSTRACT
The Load of Traffic on Pavement ...................................................................... 70 The Bearing of Load by Subgrade .................................................................... 71
General Characteristics of Subgrade Soils ............................................ 73 Soil Characteristics That Influence Bearing Value ................................ 76 California Bearing Ratio ........................................................................ 77 Unified Soil Classification...................................................................... 77 Sources of Information about Subgrade Soils........................................ 79
The Structural Roles of Pavement Materials...................................................... 81 Required Pavement Thickness................................................................ 84 Filter Layers and Geotextiles.................................................................. 86
Compaction and Its Alternatives ........................................................................ 89 The Proctor Reference for Compaction ................................................ 89 Construction with Little or No Compaction .......................................... 92
Pavement Adaptation to Freezing ...................................................................... 93 Frost Depth ............................................................................................ 93 Protection of Subgrade .......................................................................... 96 Protection of Pavement Reservoir .......................................................... 98 Experiences in Cold Climates ................................................................ 99
Pavement Adaptation to Special Subgrades ...................................................... 103 Adaptation to Wet Subgrade .................................................................. 103 Adaptation to Swelling Subgrade .......................................................... 103 Adaptation to Plastic Subgrade .............................................................. 105
Pavement Adaptation at Edges .......................................................................... 106 Support of Pavement Edges.................................................................... 106 Restraint of Flexible Pavement Edges.................................................... 107 Protection of Pavement Edges................................................................ 109
Trademarks ........................................................................................................ 111 Acknowledgments .............................................................................................. 113 References .......................................................................................................... 115
All pavements, porous and dense alike, must bear the traffic loads imposed on them in the soil and weather conditions where they are located. This chapter introduces important considerations in pavement structural design and the kinds of treatments
that can be used to respond to them. Later chapters will describe the requirements of specific porous paving materials.
