As we know that the stiffness of the bituminous of reduces at high temperature and proportion of plastic deformation out of the total deformation will be larger under higher temperature and application of higher load.
Due to repeated application of traffic load, High Temperature, and heavy load in the bituminous pavement are the main cause of rutting in the bituminous layer.
It controls the fatigue cracking (bottom-up), tensile stress, tensile strain at the bottom of CTB.
It is suggested If we provide a cement-treated base (CTB).
Horizontal tensile strain at the bottom of the bottom bituminous layer has to be controlled so it can control the bottom-up cracking in the bituminous layer.
The critical mechanistic parameter for controlling sub-grade rutting is the vertical compressive strain on top of the sub-grade.
The major concern to be taken into Considered in Design of flexible pavement
The design of flexible pavement inputs is elastic modulus, Poisson’s ratio and thickness of each layer by which IITPave software calculates the stresses, strains and deflection produced by a load applied at the surface of the pavement.
The subgrade is considered to be semi-infinite, and the sub-base, base and paving layer is considered to be infinite in the horizontal extent and finite in the thickness.
Analysis of pavement is based on the “Linear elastic layered theory ” in which the pavement is modeled as a multi-layer.
The critical mechanistic parameter is identified and controlled to a limiting value in the design process.
Distress or performance (ie stress, strain, and deflection ) calculated by specific theory and It explains in terms of mechanistic parameters. Hence we will discuss the only mechanistic-empirical type pavement model.
Mechanistic-empirical (most of the current design of flexible pavement is based on this model).
(i) Purely empirical (only based on past experience).
It is explained by performance models.
Hence these bituminous layer and granular layers are the main indicators of the functional and structural performance of the pavement. and poor quality and workmanship of bituminous or cementitious material cause cracking of layers. It is observed that variation in surface profile causes roughness to the pavement.
Design of flexible pavement for satisfactory functional and structural performance of the pavement during its life period.
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