Authors: Ramanuj Singh, Assistant Professor Hariram Sahu
Abstract: Flexible pavements founded on clay subgrades are prone to premature distress because clay soils frequently combine low bearing capacity with pronounced moisture sensitivity. Expansive clays undergo cyclic swelling and shrinkage that produce heave and cracking, while non-expansive clays exhibit low shear strength and high compressibility that lead to rutting and shear failure. Conventional remedies, such as soil replacement, chemical stabilization, and cohesive non-swelling cushions, are often costly, site-sensitive, or only partially effective, and the empirical California Bearing Ratio (CBR) design framework used across India does not explicitly capture swelling behaviour or the beneficial contribution of reinforcement. This paper presents a detailed literature review of the growing body of laboratory, test-track, and field research on the use of geotextiles and geogrids to reinforce clay subgrades beneath flexible pavements. The mechanisms of tensioned-membrane action in geotextiles and lateral-restraint/reinforced-mattress action in geogrids are examined, together with reported improvements in bearing capacity, rutting resistance, and pavement service life. Findings from Indian and international studies that employ the CBR test as the principal evaluation framework are synthesized, and Indian standards and codes relevant to reinforced-pavement design are discussed. The review identifies a persistent gap between the extensive experimental evidence for the benefits of geosynthetic reinforcement and the absence of a unified, quantitative, bearing-capacity-based design procedure that differentiates between expansive and non-expansive clay subgrade conditions, and concludes with directions for future research in this area.
