Empirical correlations for Sri Lankan peaty soils

Abstract

The composition of natural deposits of peaty soil may vary considerably among different sites, as do their engineering properties. Peat, generally formed in marshy and water logged areas, is usually dark brown to black in colour, has distinctive odour of decaying vegetation, is spongy in consistency without exhibiting distinct plasticity and has amorphous and fibrous texture. As a result, engineering properties of peaty soils are significantly different from most of the inorganic soils. The important engineering properties of the peat are permeability, compression index, coefficient of secondary compression and shear strength. These properties may vary due to chemical and biological conditions. Humification of organic constituents alters the compressibility, shear strength and hydraulic conductivity. There are useful relationships found between index properties and mechanical properties for peaty soils. The preliminary design of structures to be built on peats can profit from these relationships, sometimes even more so than when dealing with clays, due to the difficulty of obtaining high quality peat samples and to the extreme variability of peat deposits. Since the engineering properties of peaty soils are region specific, the empirical correlations for peaty soils found in Southern Transport Development project (STOP) and the updated correlations for Sri Lankan peaty soils are presented in this study.