Synthesizing an Artificial Loess for Geotechnical Investigations of Collapsible Soil Behavior

Authors: Hamed Sadeghi, Pouya A. Panahi, Hamed Nasiri, Mohammad Sadeghi

Abstract:

Collapsible soils like loess comprise an important category of problematic soils for construction purposes and sustainable development. As a result, research on both geological and geotechnical aspects of this type of soil have been in progress for decades. However, considerable natural variability in physical properties of in-situ loess strata even in a single block sample challenges the fundamental laboratory investigations. The reason behind this is that it is somehow impossible to remove the effect of a specific factor like void ratio from fair comparisons to come with a reliable conclusion. In order to cope with this limitation, two types of artificially made dispersive and calcareous loess are introduced which can be easily reproduced in any soil mechanics laboratory provided that all its compositions are known and controlled. The collapse potential is explored for a variety of soil water salinity and lime content and comparisons are made against the natural soil behavior. Trends are reported for the influence of pore water salinity on collapse potential under different osmotic flow conditions. The most important advantage of artificial loess is the ease of controlling cementing agent content like calcite or dispersive potential for studying their influence on mechanical soil behavior.

Keywords: Artificial loess, unsaturated soils, collapse potential, dispersive clays, laboratory tests.

References:

[1] Assallay AM., Rogers CDF, Smalley IJ. 1997. "Formation and collapse of meta-stable particle packings and open structures in loess deposits." Engineering Geology 49, no. 1 (1997): 101–115.
[2] Sadeghi H, Nasiri H, Ali Panahi P, Sadeghi M. "Dispersivity, collapsibility and microstructure of a natural dispersive loess from Iran." In The 16th Asian Regional Conference on Soil Mechanics and Geotechnical Engineering (16ARC), Accepted. 2019.
[3] Muñoz-Castelblanco JA, Delage P, Pereira JM, Cui YJ. "On-sample water content measurement for a complete local monitoring in triaxial testing of unsaturated soils." Géotechnique 62, no 7 (2012): 595–604.
[4] Ng CWW, Sadeghi H, Jafarzadeh F. "Compression and shear strength characteristics of compacted loess at high suctions." Canadian Geotechnical Journal 54, no. 5 (2016): 690–699.
[5] Delage P, Cui YJ, Antoine P. "Geotechnical problems related with loess deposits in Northern France." In Proceedings of International Conference on Problematic Soils, pp. 517–540, 2005.
[6] Sadeghi H, Kiani M, Sadeghi M, Jafarzadeh F. "Geotechnical characterization and collapsibility of a natural dispersive loess." Engineering Geology 250 (2019): 89–100.
[7] Ahmadi Hosseini SA, Mojtahedi SF, Sadeghi H. "Optimisation of deep mixing technique by artificial neural network based on laboratory and field experiments." Georisk: Assessment and Management of Risk for Engineered Systems and Geohazards (2019): 1–16.
[8] Sadeghi H, Chiu CF, Ng CWW, Jafarzadeh F. "A vacuum-refilled tensiometer for deep monitoring of in-situ pore water pressure." Available online in Scientia Iranica (2018).
[9] Sadeghi H. "A micro-structural study on hydro-mechanical behavior of loess." Dual-degree PhD diss., Hong Kong University of Science and Technology & Sharif University of Technology, 2016.
[10] Jefferson I, Ahmed M. "Formation of artificial collapsible loess." In Geo-Denver 2007 Congress: New Peaks in Geotechnics, pp. 1–10. 2007.
[11] Zourmpakis A, Boardman DI, Rogers CD. "Creation of artificial loess soils." In Unsaturated Soils: Experimental Studies, pp. 123–134. Springer, Berlin, Heidelberg, 2005.
[12] Jiang M, Hu H, Liu F. "Summary of collapsible behaviour of artificially structured loess in oedometer and triaxial wetting tests." Canadian Geotechnical Journal 49, no. 10 (2012): 1147–1157.
[13] Gibbs H, Holland W. Y. Petrographic and engineering properties of loess. No. 28. Technical Information Branch, Denver Federal Center, 1960.
[14] Ng CWW, Sadeghi H, Hossen SB, Chiu CF, Alonso EE, Baghbanrezvan S. "Water retention and volumetric characteristics of intact and re-compacted loess." Canadian Geotechnical Journal 53, no. 8 (2016): 1258–1269.
[15] Haeri SM, Zamani A, Garakani AA. "Collapse potential and permeability of undisturbed and remolded loessial soil samples." In Unsaturated soils: Research and applications, pp. 301–308. Springer, Berlin, Heidelberg, 2012.
[16] Jennings JE and Knight K. “A guide to construction on or with materials exhibition additional settlements Due to ‘Collapse’ of Grain structure”, sixth regional conference for Africa on soil mechanics and foundation engineering, Johannesburg, pp. 99–105, 1975.
[17] Ng CWW, Sadeghi H, Jafarzadeh F, Sadeghi M, Zhou C, Baghbanrezvan S. "Effect of microstructure on shear strength and dilatancy of unsaturated loess at high suctions." Canadian Geotechnical Journal (2019).
[18] Asadi S, Moore F, Keshavarzi B. "The nature and provenance of Golestan loess deposits in northeast Iran." Geological Journal 48, no. 6 (2013): 646–660.
[19] Ng CWW, Baghbanrezvan S, Sadeghi H, Zhou C, Jafarzadeh F. "Effect of specimen preparation techniques on dynamic properties of unsaturated fine-grained soil at high suctions." Canadian Geotechnical Journal 54, no. 9 (2017): 1310–1319.
[20] Sadeghi H, Ng CWW. "Shear behaviour of a desiccated loess with three different microstructures." In 7th International conference on unsaturated soils. 2018.
[21] Sadeghi H, Hossen SB, Chiu AC, Cheng Q, Ng, CWW. "Water retention curves of intact and re-compacted loess at different net stresses." In Japanese Geotechnical Society Special Publication, 2(4): 221–225, 2016.