A simple test and predictive models for assessing swell potential of Ankara (Turkey) Clay Zeynal Abiddin Erguler, Resat Ulusay * Department of Geological Engineering, Faculty of Engineering, Applied Geology Division, Hacettepe University, 06532 Beytepe, Ankara, Turkey Received 14 March 2002; accepted 8 August 2002 Abstract During the past three decades, damage due to swelling action of Ankara Clay has been observed more clearly in some parts of Ankara where rapid expansion of the city led to the construction of various kinds of structures. In this study, a comprehensive research program has been conducted (i) to investigate the effect of remoulding and desiccation on the swelling behavior of Ankara Clay and its swelling anisotropy, (ii) to estimate depth of active zone, (iii) to develop a simple technique in determining the magnitude of swelling based on water content of the soaked specimen after 24 and 72 h (w max24,72 ), and (iv) to produce predictive models which could be used to estimate the swelling potential of Ankara Clay from its mineralogical and simply measured engineering characteristics. A laboratory testing program was carried out using both undisturbed, and remoulded and desiccated samples selected from 20 different locations. Montmorillonite was identified as being the main clay mineral present. Based on the moisture content variation with depth, the active expansive zone was considered to be about 2 m. The test results suggest that swelling pressure of the clay considerably decreases and/or dies out when the water content is greater than 30%. It is also noted that the measured lateral swelling is significantly in excess of the vertical equivalent indicating an anisotropy with respect to swelling. Statistical assessments indicate that a new parameter (w max24,72 ) from a simple test, suggested in this study, is a very strong parameter for predicting swelling parameters of Ankara Clay. Based on 60 empirical predictive equations with coefficients of correlation between 0.96 and 0.66 from multiple regression analyses, w max24,72 , methylene blue value, liquid limit, dry unit weight and smectite content are the most important index and mineralogical properties to predict the swelling parameters of Ankara clay with small deviations from the measured values. D 2002 Elsevier Science B.V. All rights reserved. Keywords: Ankara clay; Predictive equations; Swell anisotropy; Swelling percent; Swelling pressure; w max24,72 test 1. Introduction Plastic clays exhibiting volume changes when subjected to moisture variations due to seasonal cli- matic conditions or artificial causes are termed expan- sive soils. These soils, which lie above the water table, undergo shrinkage on drying and swelling on wetting. Expansive soils occur extensively throughout the world and have been reported in numerous countries, including the United States, India, South Africa, China, Romania, Jordan and Saudi Arabia (e.g. Chen, 1988; Mohan et al., 1973; Bell and Maud, 1995; Du et al., 1999; Popescu, 1979; Basma et al., 1995; Abdul- 0013-7952/02/$ - see front matter D 2002 Elsevier Science B.V. All rights reserved. PII:S0013-7952(02)00205-3 * Corresponding author. Tel.: +90 – 312 – 297-7767; fax: +90 – 312 – 299-2034. E-mail address: resat@hacettepe.edu.tr (R. Ulusay). www.elsevier.com/locate/enggeo Engineering Geology 67 (2003) 331 – 352