Nonlinear curve-fitting procedures for developing soil-water characteristic curves

Measurement of soil suction for developing soil-water characteristic curve, SWCC, is a laborious and time-consuming task. On the other hand, commercially available databases that employ empirical fitting functions or the estimation algorithms for establishing the SWCC are quite costly and hence, beyond the reach of many. In such a situation, application of two simple nonlinear curve-fitting procedures (viz., a spreadsheet based program, SBP, and Levenberg-Marquardt Algorithm, LMA) for developing the drying SWCC was investigated. The utility and efficiency of these fitting procedures have been demonstrated by comparing the results vis-A-vis those obtained from a dewpoint potentiameter, WP4, and a knowledge-based database, KBD. In addition to this, efforts were made to develop correlations between the parameters used in the SWCC fitting functions and the physical properties of the soil, which can be determined quite easily by conducting routine laboratory tests. It has been demonstrated that these correlations can be used very efficiently for indirect estimation of the SWCC of the fine-grained soil