Direct and Indirect Permeability of Fissured Tills
Hossain D
(Received 0 0; accepted 0 0)

Abstract
Comparison of direct and indirect measurements of water permeability on relatively large undisturbed and compacted Scottish till specimens in rigid-wall (Rowe cells) and flexible-wall (triaxial cells) permeameters shows the interaction of macro-fabric, test method, evaluation basis, effective stress, and possibly sidewall leakage. At low stresses, the sidewall leakage in a Rowe cell is the most likely cause of the directly measured permeability, k_d, and pore-pressure-dissipation-based permeability, k_p, becoming higher than settlement-based permeability, k_s. Similarly, fissures raise permeability measured in both permeameters. Generally, k_p is higher than k_s (or volume-change-based k_n from triaxial cells) with k_a in between but closer to k_s (or k_n). The differences decrease with increasing stresses; the reduction rate for fissured specimens is dependent on fissure coating thickness and permeability.

Keywords:
coefficient of permeability, consolidation, fine-grained soils, fissures, laboratory methods, leakage, permeameters, pore pressure, settlement, volume change

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Author Hossain D Title Direct and Indirect Permeability of Fissured Tills Symposium , Committee on