Calibrating Hydraulic Conductivity Estimation Methods for Typical Swedish Tills Used as Core Materials

Empirical hydraulic-conductivity equations are widely used in geotechnical engineering, but none were developed specifically for the low-permeability glacial tills commonly used as core and seepage-control materials. This study evaluates and calibrates empirical conductivity equations for a dataset of 26 till materials from 10 source groups, including one Finnish source group represented by six materials. The main contribution is practical. Based on till-only screening supported by a broader multi-material comparison, the study identifies the Beyer method as the best-performing gradation-based method and the Slichter method as the best-performing porosity-dependent alternative. To adapt further for typical Swedish tills, Beyer showed little benefit from recalibration, whereas Slichter showed clearer improvement from coefficient adjustment. Gradation-based methods implicitly assume a representative packing state, whereas porosity-dependent methods explicitly account for porosity. This study also provides simple practitioner aids for estimating D₁₀ and porosity when direct material data are incomplete, for example, when sedimentation analysis or density determinations are missing. The results show that classical equations can support conductivity estimation for typical non-plastic glacial tills, but applicability remains strongly controlled by till domain, data envelope, and method class.