Development and Assessment of a Seepage-Induced Consolidation Test Apparatus

Abstract

The design, construction, and evaluation of a seepage-induced consolidation test (SICT) apparatus is described. Three materials were used in this study to encompass a range of compressibility: pure kaolin clay (kaolin), kaolin clay mixed with silica flour (silty clay), and silica flour mixed with fine sand (sandy silt). Consolidation experiments were conducted on each material in the SICT apparatus and conventional oedometer test to evaluate the ability of the experiments to measure consolidation. Consolidation behavior was characterized by void ratio versus effective stress, e-σ′, and hydraulic conductivity versus void ratio, k-e, constitutive relationships. Repeatability tests conducted on kaolin in the SICT yielded nearly identical e-σ′ and k-e relationships; oedometer results were also comparable. Constitutive relationships (e-σ′ and k-e) determined on 12 unique sets of seepage and loading pairs for kaolin were comparable to the composite e-σ′ and k-e models, which supports recommendations that a single seepage rate and single applied load can be used to determine e-σ′ and k-e relationships via the SICT. Compressibility was lower for the silty clay compared to pure kaolin because of the addition of 60 % silt; however, the range of hydraulic conductivity was nearly identical between the two materials and controlled by the kaolin. Hydraulic conductivity measured on the sandy silt in the SICT and computed from oedometer data via small-strain theory were nearly identical, which was attributed to lower compressibility that rendered small-strain theory more reasonable for oedometer data.