Transactions of the ASABE Vol. 54(4): 1325-1331 E 2011 American Society of Agricultural and Biological Engineers ISSN 2151-0032 1325 TERNARY DIAGRAM MODELING OF SOIL TEXTURE DATA FOR PREDICTING SUBSURFACE FRACTURING IN GLACIALLY RELATED FINE‐GRAINED MATERIALS E. K. Kim, Y. W. Kang, A. D. Christy, J. Weatherington‐Rice ABSTRACT. Fractures play an important role in the movement of water and contaminants through soil materials. The objectives of this research were: (1) to determine the best model for predicting fracturing, which could serve as a practical tool to anticipate and investigate fractures in glacially related fine‐grained soil materials, and (2) to identify those soil textures most likely to support fracturing. A dataset based on Ohio soils observed in the field to be fractured was extended to cover a wider range of textures through performing controlled laboratory fracturing experiments. The 30 data produced by these laboratory experiments were added to the 143 field data and together used to develop five statistical and graphical methods: the silhouette method, the girth method, the hexagonal field method, Weltje's method, and a non‐statistical best‐fit method. The best predictive model of the five was the non‐statistical best‐fit method. When plotted on a USDA ternary diagram, soils with <79% sand and >6% clay were predicted to support fracturing. All texture classes of soils were identified as able to sustain fracturing except the loamy sand and sand classes. This graphical model can be useful to explain how fractures are created in glacially related fine‐grained materials and may be a practical tool allowing geologists and field engineers to anticipate fractures without resorting to more costly methods such as soil borings, soil pits, or excavations. Keywords. Clay, Cracks, Modeling, Sand, Silt, Soil physical properties, Soil texture, Statistical analysis, USDA ternary diagram. ractures are commonly found in glacial tills and un‐ consolidated soil materials in Ohio (Brockman and Szabo, 2000; Tornes et al., 2000; Weatherington‐ Rice, 2003). Fractures play an important role in the movement of water and contaminants through these materi‐ als, resulting in recharging underlying aquifers but also facil‐ itating groundwater contamination when pollutants are discharged at or below the ground surface (Fausey et al., 2000; Weatherington‐Rice et al., 2000; Phillips et al., 2007). It is difficult to predict the occurrence and development of fractures in natural settings. The soil textures observed to sus‐ tain fractures are very diverse and include many different soil types (Tornes et al., 2000). Few statistical analyses of soil tex‐ tural data in fractured glacially related fine‐grained materials have been attempted. Soil texture is one of the two principal factors controlling the creation and development of fractures in glacially derived materials (Gross and Moran, 1971; Steiger and Holoway‐ chuck, 1971; Connell, 1984; Konen, 1995; Tornes et al., 2000; Kim and Christy, 2006). The other primary factor is Submitted for review in October 2010 as manuscript number SW 8828; approved for publication by the Soil & Water Division of ASABE in July 2011. The authors are Eun Kyoung Kim, Visiting Research Scholar, Young Woon Kang, Visiting Research Scholar, Ann D. Christy, ASABE Member, Associate Professor, and Julie Weatherington‐Rice, Adjunct Assistant Professor, Department of Food, Agricultural and Biological Engineering, The Ohio State University, Columbus, Ohio. Corresponding author: Ann D. Christy, Department of Food, Agricultural and Biological Engineering, 590 Woody Hayes Dr., The Ohio State University, Columbus, OH 43210; phone: 614‐292‐3171; e‐mail: christy.14@osu.edu. clay mineralogy. Ohio's clay minerals are typically a mixture of kaolinite, illite, and chlorite with limited amounts of ver‐ miculite (table 3 of Kim et al., 2010), and this mixture is rela‐ tively uniform in the greater Ohio geomorphological region. The locations in Ohio where samples were collected had low levels of smectites. Clay mineralogy will change as location shifts from the Midwest towards the western U.S. because more volcanic ash is present in the western glacial tills, which then weather out to the higher shrink‐swell smectites (e.g.,Ămontmorillonites and bentonites). Because kaolinitic clays are not as readily fractured as smectites (Boivin et al., 2004), it is likely that this fracturing research applies beyond Ohio. Secondary factors that also relate to fracturing are soil structure and macropores such as plant roots, worm holes, and animal burrows (Mitchell and van Genuchten, 1992; Dorner et al., 2009). These factors are the direct results of the effects of soil texture and clay mineralogy in native soils and disturbed fill materials. Soil structure development and pro‐ gressive fracturing of fill has been documented (Weatherington‐Rice and Hall, 2006). Roots have been shown to grow preferentially through fractures and other ma‐ cropores (McMahon and Christy, 2000). Several researchers (Gross and Moran, 1971; Steiger and Holowaychuck, 1971; Connell, 1984; Konen, 1995; Tornes et al., 2000; Kim and Christy, 2006; Kim et al., 2010) have investigated how the likelihood of fractures varied depending on the soil texture of unconsolidated materials. Their conclu‐ sions were that fractures were more likely to occur in glacial tills with loam, clay loam, silty loam, silty clay loam, silty clay, and clay textures (Gross and Moran, 1971; Steiger and Holowaychuck, 1971; Connell, 1984; Konen, 1995; Tornes et al., 2000; Kim and Christy, 2006; Kim, 2007; Kim et al., F