Page 82 - SAPEM-Chapter-10-2nd-edition-2014
P. 82
South African Pavement Engineering Manual
Chapter 10: Pavement Design
Pavement structure
Loading
Material parameters
• Resilient properties
• Strength properties
Pavement (Resilient)
Response Model
• Stresses and strains
Critical Response Parameters
• Stress or strain parameter
Design iterations:
Empirical Damage Models • Material quality
adjustment
• Layer thickness
Pavement Structural adjustment
Capacity Estimate
No
Adequate?
Yes
Final pavement design
Figure 30. Main Components of a Mechanistic-Empirical Pavement Design Method
The process begins with the characterisation of the design problem in terms of the following inputs:
• Pavement structure
− Number of layers
− Layer thickness
• Material characteristics for each pavement layer
− Resilient response characteristics: Resilient modulus and Poisson’s Ratio (see Chapter 2: 3 for definitions)
− Strength characteristics, which depend on the material type
− Material properties, which also depend on the material type
• Design loading
− Number of loads
− Coordinates for each individual load
− Contact stress, load or load radius for each individual load
(i) Loading
Historically, ME design has used the standard axle as the load input. See Section 4.1.3 for a definition of a standard
axle and details on how to convert actual loading to the equivalent standard axle. A circular load of uniform contact
pressure is used.
(ii) Inputs
The solution type used for the multi-layered pavement system dictates the required material models and inputs,
namely Young’s modulus and Poisson’s ratio (defined in Chapter 2: 3). Young’s modulus applies to perfectly linear-
elastic materials, while pavement materials mostly behave non-linearly and inelastically. The resilient modulus (M r ),
a linear secant modulus, is used as the Young’s modulus input to approximate the non-linear, stress-strain behaviour
of pavement materials.
Section 6: Structural Capacity Estimation
Page 71
