Compressibility behaviour and properties of peaty soils from Dian-Chi Lake area, China

Abstract

Peat deposits are widely encountered in many parts of the world and present various challenges for the geotechnical engineering community because of their low bearing capacity and very high compressibility and creep potential. This paper describes extensive index and oedometer testing to investigate the compressibility behaviour/properties of deep, strongly to completely humified peat and highly organic fine-grained soil layers at the northeast shore of Dian-Chi Lake in Kunming, southwest China; a region that recently is experiencing significant infrastructure construction. Compared to surficial peat deposits, the peaty soil layers investigated, with organic contents ranging 23.5–80.0%, have been subjected to a 6.7-m depth of inorganic soil overburden, such that they have substantially lower water content and void ratio and higher preconsolidation stress. Nevertheless, with deduced Cα/Cc = 0.04–0.07, Cr/Cc = 0.14–0.18 and Ck/e0 = 0.23, the Dian-Chi peaty soils exhibit similarities with surficial fibrous peats from other countries/regions. Unlike fibrous peats, however, the Dian-Chi peaty soils have extremely low permeability, with deduced kv values of the order of 1 × 10−9 to 1 × 10−10 m/s, consistent with their hunification level. Existing linear Cc – w0 correlations were found inadequate for the Dian-Chi peaty soils, such that a new Cc – w0 correlation is proposed from curve-fitting of the gathered experimental data to better capture their non-linear relationship.