International Journal of Science, Engineering and TechnologyAuthors: V.Nikhilesh, Assistant professor B.Narsimha
Abstract: Accessibility and connectedness to diverse areas through a well-connected transport network are crucial to any country's prosperity. Road transport is governments' top priority when it comes to directing massive capital investments; it is the most versatile means of travel under different topographical circumstances. Since clayey soils cover almost 40% of India's landmass, roadways in the country must traverse them. Less initial cost, a smoother riding surface, and simple maintenance are the primary reasons why flexible pavements are favoured over rigid ones. Construction costs are expensive because clay subgrades have low soaked CBR values, necessitating a thicker pavement design. Flexible pavements over clayey soils often collapse with significant rutting, a wavy surface, longitudinal cracking along the wheel track, and shear failure in the edge region, even though they provide a considerable pavement thickness. Additionally, expansive clays' shrink-swell behaviour in response to changes in moisture makes pavement building a major headache, and the material's extremely low strength in saturated condition, caused by swelling, drives up the price of pavement construction. Researchers are periodically trying to find ways to stabilise, reinforce, control moisture, and replace soil in order to make clay subgrades and expansive soils stronger and more stable (Katti, 1979; Natarajan and Shanmukha Rao, 1979, Steinberg, 1992, Ramana Murthy, Prasada Raju). Highway engineers have taken notice of geosynthetics and are considering using them to improve the performance of pavements. In particular, synthetic geotextile has been utilised over the past twenty years as a separator-filter-drain at clay subgrades, as well as for the management of reflection cracking in overlays, all because of its multi-functional behaviour. Holding geotextiles at the subgrade has dual benefits: first, it stiffens the base layer; second, it reduces natural stress on the subgrade caused by membrane action. Despite this, the membrane effect, which geotextiles may use to reinforce, has received very little attention. Based on deriving the reinforcing effect of subgrade put at subgrade, Giroud & Noiray (1981) provided a reinforced flexible pavement design for unpaved roads, and Satyanarayana Reddy and Murthy (2005) refined this technique for pavements over expansive clay subgrade. Alternative approaches created by Bender and Barenberg and The Koerner numbers are based on actual data. As a result, this study's primary objective is to establish and validate, via test track investigations, design approaches for expansive and non expansive clay subgrades. The current study presents a design methodology that controls swelling of the clay subgrade and ensures safety against shear and settlement failures. This is in response to the lack of practical evidence in the existing literature on reinforced flexible pavements over expansive subgrades (Satyanarayana Reddy and Rama Moorthy, 2005; Satyanarayana Reddy and Chinnapa Reddy, 2011). Test track has been built across expansive clay subgrade, which is part of NH-18 and passes through Kurnool town. This will prevent the flexible pavement from failing over non expansive clay subgrades.
