Full Length Article Feasibility of using electrokinetics and nanomaterials to stabilize and improve collapsible soils Arash Hosseini a, * , S. Mohsen Haeri b , Siavash Mahvelati a , Aria Fathi c a Department of Civil and Environmental Engineering, Temple University, Philadelphia, PA 19122, USA b Department of Civil Engineering, Sharif University of Technology, Tehran, Iran c Department of Civil Engineering, The University of Texas at El Paso, El Paso, TX 79968, USA article info Article history: Received 29 August 2018 Received in revised form 25 March 2019 Accepted 13 June 2019 Available online xxx Keywords: Loess Electrokinetics Collapsible soil Soil improvement Unsaturated oedometer Nanosilica abstract Loess as a subcategory of collapsible soils is a well-known aeolian deposit generally characterized as a highly-porous medium with relatively low natural density and water content and a high percentage of fine-grained particles. Such collapsible soil sustains large stresses under a dry condition with natural water content. However, it can experience high and relatively sudden decreases in its volume once it reaches a certain water content under a certain load and therefore, the natural condition of the soil might not be suitable for construction if the possibility of the exposure of the soil to excessive water exists during the lifetime of the project. This research presents the utilization of an innovative method for stabilization and improvement of Gorgan loessial soil. This method uses electrokinetics and nano- materials to instigate additives to move through soil pores, as an in situ remedial measure. To assess the acceptability of this measure, the deformability and strength characteristics of the improved collapsible soil are measured and compared with those of the unimproved soil, implementing several unsaturated oedometer tests under constant vertical stress and varying matric suction. The result emphasizes the importance of the matric suction on the behavior of both improved and unimproved soils. The test re- sults indicate that the resistance of the soil was highly dependent on the water content and matric suction of the soil. The oedometer tests on samples improved by 3% lime and 5% nanomaterials show considerable improvement of the collapse potential. Results also reveal that stabilized samples experi- ence notably lower volume decrease under the same applied stresses. Ó 2019 Institute of Rock and Soil Mechanics, Chinese Academy of Sciences. Production and hosting by Elsevier B.V. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/ licenses/by-nc-nd/4.0/). 1. Introduction Collapsible soils such as loess have relatively high resistance at their natural water content, but as soon as they are exposed to saturation, their volume rapidly decreases especially under addi- tional load. Consequently, large destructive deformations are ex- pected to occur in such situations (Haeri et al., 2015). Loess, a well- known collapsible soil, is a type of aeolian deposit formed by the accumulation of wind-blown silt. It can be found in arid and semi- arid regions and is usually characterized as a homogeneous and highly porous medium traversed by vertical capillaries. These capillaries allow the soil to fracture and to form vertical bluffs (Heydartaemeh et al., 2017). Terzaghi et al. (1996) described loessial soils as “uniform cohesive wind sediments mainly comprised of quartz in size of silt and fine sand, which are weakly constructed and dras- tically lose their cohesiveness (caused by the presence of clayey par- ticles and calcium carbonate bonds) by increasing moisture”. After being exposed to additional sources of water, these relatively dry deposits may undergo large suction and bond strength reductions which result in a sharp increase in compressibility (i.e. virtually collapse) (Lawton et al.,1992; Haeri, 2016). Common incidents that can expose unsaturated loess to additional water are comprised of excessive irrigation, broken water/sewer pipe, groundwater level rise, and heavy and continuous rainfall. In loess with a considerable portion of fine particles such as silt or clay, the initial high negative pore pressures can result in a significant contribution to suction (Houston and El-Ehwany, 1991; Haeri et al., 2012, 2014a, b). The behavior of loessial soils has caused severe damages to (infra-) structures built in/over loess. Only considering China as an example over the time span 1974e1975, it has been reported that a * Corresponding author. E-mail address: amhosseini@temple.edu (A. Hosseini). Peer review under responsibility of Institute of Rock and Soil Mechanics, Chi- nese Academy of Sciences. Contents lists available at ScienceDirect Journal of Rock Mechanics and Geotechnical Engineering journal homepage: www.rockgeotech.org Journal of Rock Mechanics and Geotechnical Engineering xxx (xxxx) xxx Please cite this article as: Hosseini A et al., Feasibility of using electrokinetics and nanomaterials to stabilize and improve collapsible soils, Journal of Rock Mechanics and Geotechnical Engineering, https://doi.org/10.1016/j.jrmge.2019.06.004 https://doi.org/10.1016/j.jrmge.2019.06.004 1674-7755 Ó 2019 Institute of Rock and Soil Mechanics, Chinese Academy of Sciences. Production and hosting by Elsevier B.V. This is an open access article under the CC BY- NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/).