![]() In this regard, the loss on ignition N is a useful index property, serving as a convenient, quicker and reliable means for specific gravity determination, with N correlating strongly with G s for various organic soils according to the following (see the Appendix (which also includes Figure 7 ) for equation derivation). The pycnometer method for specific gravity determinations is a pernickety and time-consuming test to perform, particularly for peaty soils ( O’Kelly, 2018, 2019). The rate and extent of this time-dependent process and its various controlling geoenvironmental factors (pH, carbon (C):nitrogen (N) ratio, aeration level, temperature) have been investigated for peat ( O’Kelly and Pichan, 2013, 2014 Wardwell et al., 1983) and for municipal organic sludge and residue materials ( O’Kelly, 2008, 2016 Zhan et al., 2014). For peat and other organic soils, increasing humification levels achieved over time cause a decrease in the soil’s organic fraction relative to its higher specific gravity inorganic fraction, such that as the N value decreases, the specific gravity of soil solids increases. It should be noted that different oven-drying temperature ranges of 110 ± 5☌ ( ASTM, 2014b) and 50.0 ± 2.5☌ ( BSI, 1990b) are specified for preparing the dried ignition specimens. For this ignition temperature value, the inorganic solids fraction is assumed inert and it remains as the ash residue in the specimen crucibles, with the N value (as %) calculated as 100 minus the percentage ash content. Total volatile solids (loss on ignition, N), as determined by the percentage reduction in the mass of an oven-dried test specimen on ignition in a muffle furnace at a standard temperature of 440 ± 40☌ ( ASTM, 2014b BSI, 1990b), is used as an indirect measure of the organic matter content ( P). Standard oven temperature ranges of 105–110☌ ( BSI, 1990a) and 110 ± 5☌ ( ASTM, 2014a) are specified for oven-drying of the soil material used in performing pycnometer tests. The definitive geotechnical laboratory approach for specific gravity determinations is the pycnometer method, which is performed on the soil fraction with particles sizes <2 mm (BS EN 1377-2:1990 ( BSI, 1990a)) or <4.75 mm (ASTM D 854-14 ( ASTM, 2014a)). ![]() Accurate knowledge of the G s value allows the determination of the void ratio (among other basic parameters) for given soil densities and water contents. ![]() As an important physical property, the specific gravity of solids ( G s) is defined as the ratio of the mass of dry solid particles to the mass of de-aired distilled water they displace, and its value is usually referenced to a standard temperature of 20☌ ( ASTM, 2014a BSI, 1990a). For instance, the natural (in situ) gravimetric water content ( w n) typically ranges from approximately 200 to 2000% ( Hobbs, 1986 Mesri and Ajlouni, 2007 O’Kelly, 2015 O’Kelly and Sivakumar, 2014) for heavily consolidated decomposed (amorphous) peat deposits and coarse-fibrous surficial peat deposits, respectively. Compared with most inorganic soils, these materials generally have an extremely high water content, a high organic content, a low specific gravity of solids and hence low bulk and dry density values. Surficial peat deposits cover large areas of the world’s land mass, and peaty soil layers can occur at depth. To overcome procedural differences between codes and for previous experimental work, it is recommended that an oven temperature of 105☌ be consistently used for drying peaty soil specimens. A weaker inverse bilinear relationship was found between G s and w n. For the 102 peaty soils examined, the best-fit G s– N correlation was obtained for specific gravities of the inorganic and organic solids fraction values of 2.77 and 1.35, respectively. The main research aim is to investigate correlations between G s, natural water content ( w n) and N for the standard ignition temperature of 440☌, thereby allowing indirect G s estimations. This paper presents original G s– 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. ![]() However, G s determinations using the standard pycnometer test are time consuming and pernickety, such that the G s value is often predicted by way of ignition loss ( N) correlations instead. Accurate knowledge of the G s value allows void ratio computations for given water contents and densities. Peaty soils have an extremely high water content and a low specific gravity of solids ( G s) compared with most inorganic soils.
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