Probabilistic analysis of soil suction and cracking in fibre-reinforced soil under drying–wetting cycles in India

Desiccation crack propagation with suction (ψ) in field conditions are dependent on various uncertain parameters such as soil pore-size distribution, drying–wetting cycles and environmental conditions. The evolution of crack intensity factor (CIF) with ψ was generally explored in a deterministic approach. In literature, bivariate dependency between CIF and the inducing ψ has rarely been accounted. The objective of the paper is to explore the bivariate dependencies in CIF and ψ by using the copula approach. Data from 105 d of monitoring on four soil types (one bare and three fibre reinforced) was done. This paper also investigates the use of three natural fibres (coir, jute and water hyacinth (WH)) to minimise soil desiccation and their effect on the CIF–ψ relationship. Compacted bare soil showcased the highest desiccation compared to reinforced specimens, particularly at high suction range (near 4000 kPa). The peak CIF was less for fibre-reinforced samples because of the ‘bridge effect’ of fibres. Coir fibre, being multifilament and highly ductile, had showcased the lowest CIF values. Four copulas were explored, among which Clayton (bare and WH), Gaussian (coir) and Frank (jute) were found to be the best fit to the dependence structure for CIF–ψ in unsaturated soil.