Contents lists available at ScienceDirect Transportation Geotechnics journal homepage: www.elsevier.com/locate/trgeo Efectof road salts on the hydro-mechanical behavior of unsaturated collapsible soils Amir Akbari Garakani a, ⁎ ,S.MohsenHaeri b , Davood Yazdani Cherati b ,FaridAhmadiGivi b , Matin Kabiri Tadi b , Amir Hossein Hashemi b ,NavidChiti b , Fatemeh Qahremani c a Niroo Research Institute, Structural Research Department, Tehran, Iran b Sharif University of Technology, Dept. of Civil Eng., Tehran, Iran c University of Science and Culture, Dept. of Civil Eng., Tehran, Iran ARTICLEINFO Keywords: Unsaturated collapsible loess Road salts Transportation infrastructure Osmotic and matric suctions Laboratory tests Empirical model ABSTRACT Hydro-mechanical behavior of unsaturated collapsible soils can be drastically afected by saline infltrations. Saline infltrations into the underlain soil layers of the urban transportation and lifelines due to deicing or existence of trafc pollutants has been a common issue of concern for years in many countries. Additionally, many reports have been published so far, indicating the construction of roads and railways on unsaturated collapsible soils. In this research, hydro-mechanical characteristics of an unsaturated collapsible loessial soil diluted with saturated solutions of three diferent salts that are frequently involved in transportation infra- structure (namely NaCl, CaCl 2 and KCl) are investigated by conducting scanning electron microscopy (SEM), flter paper, uniaxial compression and oedometer tests. Obtained test results have been analyzed by simulta- neousconsiderationofthematricandosmoticsuctionsinthesoiltextureandtheappliedstresses.Testresults revealed that the soil texture and hydro-mechanical responses of the soil are considerably afected by the salt type,salinedegreeofsaturationandappliedloadingpaths.Resultsalsoimplythatthereisacriticalsalinedegree of saturation (corresponded to each loading path and each mixing salt type), at which the magnitude and modality of the osmotic and matric suctions within the soil fabric are changed. In addition to experimental studies,empiricalconstitutivemodelsarepresentedinthispapertopredictthechangesinstrength,stifnessand yieldstressofthetestedcollapsiblesoilsubjectedtodiferentroadsalts.Comparisonsshowverygoodagreement betweenthelaboratorytestresultsandthemodelpredictions.Theachievementspresentedinthisresearchcan be directly implemented for better prediction of the behavior of unsaturated collapsible soils subjected to salinity. In addition, the result can be implemented in a suitable stabilization plan when the soil and salt in- volved in transportation infrastructures. Introduction Research background Hydro-mechanical behavior of unsaturated soils are drastically af- fectedbythechangesofefectivestress,soilmoisture,soildensityand pore structure inside the soil matrix [53]. Collapsible soils are parti- cular types of unsaturated problematic soils, which possess open and meta-stable structure, low dry density (less than16kN/m 3 ),lowinitial degree of saturation and high initial void ratio [16,24,42].Increasein watercontentinnormalorexpansivesoilsusuallyleadstoadecreasein efective stress level and consequently increase in the soil volume and expansionofthesoilstructure.However,incollapsiblesoils,increasein water content would result in breaking inter-particle bonds under adequate efective stress, and sudden soil volume reduction and soil structural collapse occurs [16,22]. The collapsible behavior of these types of problematic soils has caused numerous damages to transportation infrastructures (e.g., roads, pavements, railways, airports…). For instance, in 1993, numerous sink- holesappearedduringtheTGVRailwaysconstructioninNorthernFrance due to collapsible behavior of an underneath loessial soil layer [12]. Similar problem has been reported in Romania for a railway https://doi.org/10.1016/j.trgeo.2018.09.005 Received 1 July 2018; Received in revised form 19 September 2018; Accepted 20 September 2018 ⁎ Corresponding author. E-mail addresses: aakbari@nri.ac.ir (A.A. Garakani), smhaeri@sharif.edu (S.M. Haeri), davood.yazdani71@student.sharif.edu (D.Y. Cherati), farid.ahmadi1992@student.sharif.edu (F.A. Givi), m.kabiri2015@student.sharif.edu (M.K. Tadi), amirhossein.hashemi94@student.sharif.edu (A.H. Hashemi), navid.chiti1992@student.sharif.edu (N. Chiti), f.qahremani@usc.ac.ir (F. Qahremani). Transportation Geotechnics 17 (2018) 77–90 Available online 27 September 2018 2214-3912/ © 2018 Elsevier Ltd. All rights reserved. T