Abstract
Design of flexible pavements is not straightforward when reinforcement materials, such as geogrid, geocell, and other types of geosynthetic materials, are used in pavement construction. Presently in India, elasticity theory is used to analyze strains due to wheel load applied on multi-layered soil system through a pavement analysis program, IITPAVE, to design the unreinforced pavement section as per Indian Roads Congress guidelines (IRC-37: 2012). The improvement in the performance of geogrid- reinforced pavement with respect to unreinforced pavement can be quantified in terms of Layer Coefficient Ratio (LCR) or Traffic Benefit Ratio (TBR). In the present study, both LCR and TBR based approaches are proposed to design geogrid-reinforced base courses of pavements with specific goals. These specified goals included designs based on (a) reduction in consumption of aggregates, and (b) reduction in the overall cost of construction of pavement reinforced with geogrids. Design charts are provided based on LCR and TBR values corresponding to selected traffic and California Bearing Ratio (CBR) of subgrades. The benefits of reinforcement in the pavement structure are found to be high when used over weak subgrades (CBR < 5%). For example, a reduction in thickness of aggregate layer is found to be in the range of 28% to 45%. Additionally, the sustainability of geogrid-reinforced pavement is quantified by comparing the embodied carbon (EC) generated from construction of geogrid-reinforced and unreinforced pavements. EC of reinforced pavements is found to have reduced by as much as 58 to 85 tCO2e/km in comparison with unreinforced pavement.
Highlights
The design of flexible pavement is complex owing to its non-homogenous nature of multiple pavement layers with different thicknesses and mechanical properties, and the wide range of loading and climatic conditions for which it is designed
This paper critically examines the IRC:SP:59 (2019), and proposes objective based design approaches for geogrid-reinforced pavement along with the design charts based on IRC guidelines
Design charts are provided based on layer coefficient ratio (LCR) and traffic benefit ratio (TBR) values corresponding to selected traffic and subgrade California Bearing Ratio (CBR) values according to the two objectives specified above
Summary
The design of flexible pavement is complex owing to its non-homogenous nature of multiple pavement layers with different thicknesses and mechanical properties, and the wide range of loading and climatic conditions for which it is designed. It is essential to incorporate new materials into the pavement design in order to optimize the material consumption and performance. The new materials such as geosynthetics have been used to reinforce pavement layers to improve their performance in critical site conditions and to sustain heavy loading situations. For sustainable development of transportation infrastructure, use of locally available materials in combination with engineered materials such as geosynthetics is considered one of the best solutions to preserve the dwindling natural resources. The use of geogrids offsets and partly reduces the aggregate requirement in the pavement layers and impart sustainability in pavement construction by lowering the carbon footprint (Morrison, 2011). An attempt is made to compute EC values for the unreinforced and geogrid-reinforced pavements with similar service life
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