Page 15 - SAPEM-Chapter-10-2nd-edition-2014

South African Pavement Engineering Manual
Chapter 10: Pavement Design

Table 1. Elements of New and Rehabilitation Pavement Design

Element New Design Rehabilitation Design
Design Principles • Use material of sufficient strength and stiffness in the structural layers to withstand the
(Section 2) loading
• Provide sufficient cover to the subgrade to ensure it is outside the area of high stress
• Provide a pavement foundation of adequate support for the structural layers
• Create a gradual transition in strength from the structural layers to the subgrade for
flexible pavements
• Provide adequate support in the subbase for rigid pavements
• Maximise material strength, with proper compaction and by keeping the pavement dry:
− Proper drainage design and maintenance
− Maintain surfacing integrity
• Eliminate obvious problems, e.g., repair
badly cracked local areas before overlay
• Select appropriate remedial measures
for areas not requiring structural
strengthening
• Maximise the use of the existing
pavement structure in providing the
required structural capacity
Design • Road category
Considerations • Analysis and structural design periods
(Section 3) • Life cycle strategy
• Pavement balance (for flexible pavements)
• Pavement behaviour
• Materials
• Environmental considerations
• Practical considerations
• Pavement type selection
Design • Design traffic calculations
Techniques • Structural capacity estimation
(Sections 4 & 5)
Design Data collection: Structured approach for investigation:
Investigation • Available data • Initial assessment:
(Section 5) • Additional testing − Condition assessment
• Identify uniform subgrade sections − Homogeneous/uniform sections
• Assess material availability, quality and − Past and future traffic
cost − Initial structural capacity assessment
• Traffic investigation and design traffic • Detailed assessment:
Pavement Design Process Structural • Match structural capacity of the • Match structural capacity of the
− Identify distress mechanisms and
estimate
remedial measures
− Characterise the existing structure
for utilisation in the design
− Generate uniform section reports

pavement
pavement with future traffic demand
pavement with future traffic demand
design
• Use appropriate structural design
• Use appropriate structural design
techniques
(Sections 6,
7, 8 & 9)
− CBR, AASHTO Structural Number,
− Deflection based methods, AASHTO
Structural Number, DCP, SAMDM,
DCP, Catalogues, SAMDM, Pavement techniques
Number, cncPAVE, Lockpave Pavement Number, cncPAVE,
• Adhere to design principles Lockpave
• Adhere to design principles
Economic • Link to the life cycle strategy
analysis • Consider construction, maintenance and rehabilitation cost
(Section 5) • Select the most economically viable design

Section 1: Introduction
Page 4