ROAD DETERIORATION MODELS KEY VARIABLES AFFECTING DETERIORATION OF

ROAD DETERIORATION MODELS. KEY VARIABLES AFFECTING DETERIORATION OF BITUMINOUS PAVEMENT.

AIMS AND OBJECTIVES l SESSION AIMS 4 To teach the key variables affecting road deterioration modeling in HDM-4. 4 To make the participant aware of the key reference document l SESSION OBJECTIVES 4 To outline the principles behind modeling of bituminous pavement deterioration. 4 To identify the various factors which affects bituminous pavement performance. 4 To explain the basis of various pavement defects and condition indicators which are modelled in HDM-4, and to highlight the most important explanatory variables.

INTRODUCTION l Road deterioration is broadly a function of the original design, material types, construction quality, traffic volume, axle load characteristics, road geometry, environmental conditions, age of pavement, and maintenance policy pursued. l HDM-4 includes relationships for modeling Road Deterioration (RD) and Road Works Effects (WE). These are used for the purpose of predicting annual road condition and for evaluating road works strategies.

PAVEMENT DETERIORATION l Various defects modelled in the following order 4 Cracking 4 Ravelling 4 Potholing 4 Edge break 4 Rutting 4 Roughness 4 Texture depth 4 Skid resistance

PAVEMENT CLASSIFICATION SYSTEM

FACTORS AFFECTING PAVEMENT PERFORMANCE 4 TRAFFIC - no. of esa’s 4 CLIMATE - moisture-temperature 4 TIME (AGE) - since construction or maintenance 4 STRENGTH - Structural no, DEF, etc 4 DRAINAGE - condition/quality 4 CONSTRUCTION - type and quality 4 MAINTENANCE - type and quality

TRAFFIC l The primary traffic-related variables that effect road deterioration include 4 number and type of vehicles using the road. 4 Axle loading characteristics of the different vehicles types.

CLIMATE AND ENVIRONMENT l The climate in a road is situated has a significant impact on the rate at which the road deteriorates. l Important climatic factors are related to 4 temperature 4 precipitation 4 winter condition

TEMPERATURE

RAINFALL/MOISTURE CLASSIFICATION

ENVIRONMENTAL COEFFICIENT

PAVEMENT STRENGTH l Affected by: 4 Pavement materials and thickness 4 Subgrade 4 Drainage regime and seasonality l Adjusted Structural Number(SNP) is used 4 Similar to modified structural number of HDMIII/AASHO 4 But contribution of pavement layers/subgrade weighted by depth.

EFFECT OF DRAINAGE l Depends on seasonal variations (wet and dry seasons) l Depend on type and condition of drains l Depends on ingress of water into pavement (crack and potholes)

CONSTRUCTION QUALITY Poor construction quality or variability in material properties have a significant effect on the performance of pavement 3 parameters are used to model these effects 4 COMP - relative compaction of the pavement layers affects the rate of deformation(rutting) 4 CDS - surface aspects - mainly driven by binder content - affects cracking and plastic deformation 4 CDB - roadbase aspects - affects potholing

CONCLUSIONS z. Pavement deterioration manifests itself in various kind of distresses, each of which should be modelled separately. z. As each mode of distress develops and progresses at different rates in different environments, it is important that RD relationships should be calibrated to locals conditions before using them for road investment analyses.