The concept of “apparent” Compression Index
One-dimensional consolidation tests are often performed without accurate control of the initial degree of saturation, since most commercially used testing apparatuses do not permit back-pressuring. As a result, the initial degree of saturation is often less than unity and, thus, the measured ‘Apparent’ Compression Index can be very different than the value corresponding to a fully saturated sample. Similar differences are caused by most oedometer tests being performed up to a maximum stress lower than the maximum pre-consolidation pressure. Oedometer tests on undisturbed samples, on initially unsaturated samples of reconstituted soil, and a data-base of commercial oedometer tests are presented in order to exhibit the effect of high maximum preconsolidation pressure, cementation and initial unsaturation. Finally, expressions for the volumetric deformation of unsaturated soils proposed by Alonso et al. (1990) are used to explain different trends exhibited by the ‘Apparent’ Compression Index for low- and high-plasticity soils.
KeywordsCompression Index Oedometer Test Reconstituted Soil Unsaturated Sample WKDQ WKRVH
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- Alonso EE, Gens A, Josa A (1990) A constitutive model for partially saturated soils. Géotechnique. 40: 405–430.Google Scholar
- Bardanis ME (1998) An experimental study of the ‘robustness’ of the Intrinsic Compression Line. M.Sc. Thesis, Imperial College of Science, Technology and Medicine, University of London.Google Scholar
- Bardanis ME (1999) An experimental study of the properties of intrinsic compressibility of one clay and one marl. In: Proceedings 13th Young Geotechnical Engineers Conference, Santorini, Greece, pp 88–97.Google Scholar
- Bardanis M, Cavounidis S (2001a) Empirical relations between the compression index of clayey soils and their physical characteristics (in Greek). In: Proceedings 4th Hellenic Conf on Geotechnical & Geoenvironmental Engng, pp 123–130.Google Scholar
- Bardanis M, Cavounidis S (2001b) Comparison between compression index from empirical relations and tests on clayey soils from Greece (in Greek). In: Proceedings 4th Hellenic Conf on Geotechnical & Geoenvironmental Engng, pp 131–138 (in Greek).Google Scholar
- Burland JB (1990) On the compressibility and shear strength of natural clays Géotechnique. 40: 327–378.Google Scholar
- Casagrande A (1936) The determination of the pre-consolidation load and its practical significance. In: Proceedings 1st Int Conf on Soil Mech & Found Engng, pp 60–64.Google Scholar
- Chandler RJ (1999) Clay sediments in depositional basins: the geotechnical cycle. Quart J of Engng Geol & Hydrogeology. 33: 7–39.Google Scholar
- Dineen K (1997) The influence of soil suction on compressibility and swelling. Ph.D. Thesis, Imperial College of Science, Technology and Medicine, University of London.Google Scholar
- Kavvadas MJ, Anagnostopoulos AG, Georgiannou VN, Bardanis ME (2002) Characterisation and engineering properties of the Corinth marl. In: Tan et al (eds) Proceedings Int Workshop ‘Characterisation and Engineering Properties of Natural Soils’. AA Balkema Publishers, pp 1435–1459.Google Scholar
- Kavvadas M, Anagnostopoulos AG, Kalteziotis N (1993) A framework for the mechanical behaviour of the cemented Corinth marl. In: Proceedings Int Symp on Hard Soils-Soft Rocks, Athens, Greece, pp 577–583.Google Scholar