Briefing: Specific gravity of solids relationship with ignition loss for peaty soils

Abstract

Peaty soils have an extremely high water content and a low specific gravity of solids (Gs) compared with most inorganic soils. Accurate knowledge of the Gs value allows void ratio computations for given water contents and densities. However, Gs determinations using the standard pycnometer test are time consuming and pernickety, such that the Gs value is often predicted by way of ignition loss (N) correlations instead. This paper presents original Gs–N data for 25 peaty soils (N = 23–86%) from the Dian-Chi Lake area, Kunming City, China, along with a data set assembled from various sources in the literature for 77 peaty clays and peats. The main research aim is to investigate correlations between Gs, natural water content (wn) and N for the standard ignition temperature of 440°C, thereby allowing indirect Gs estimations. For the 102 peaty soils examined, the best-fit Gs–N correlation was obtained for specific gravities of the inorganic and organic solids fraction values of 2.77 and 1.35, respectively. A weaker inverse bilinear relationship was found between Gs and wn. To overcome procedural differences between codes and for previous experimental work, it is recommended that an oven temperature of 105°C be consistently used for drying peaty soil specimens.