Development and verification of a miniature cone penetration test
Date
2019
Authors
Kahramanoglu, Kubra, author
Bareither, Christopher A., advisor
Scalia, Joseph, committee member
Singleton, John, committee member
Journal Title
Journal ISSN
Volume Title
Abstract
The objectives of this research were to design and validate a miniature cone penetration test (MCPT) system for testing fine-grained soils. The system included a commercially-available miniature piezocone and a 300-mm-diameter, rigid-wall, calibration chamber. Three different materials were used in this study: (i) Ottawa sand, (ii) fine synthetic tailings (FST), and (iii) coal combustion product (CCP). Ottawa sand was used to evaluate repeatability of the MCPT apparatus and verify results via comparison to literature. The FST was a mixture of kaolin clay and silica flour, whereas CCP was primarily sand and silt and collected from a coal ash impoundment in North America. These two materials were tested to assess undrained and drained shear behavior and compare with previously measured shear strength. Replicate MCPTs conducted on Ottawa sand at three different relative densities indicated that the MCPT was repeatable. The assessment of tip resistance and sleeve friction in the Ottawa sand MCPTs were used to identify a functional depth of penetration whereby the friction sleeve was fully mobilized. Values of tip resistance and sleeve friction obtained from the MCPT at these depths of penetration were taken as representative of the specimen and subsequently validated via comparison to literature. Pore water pressure developed during cone penetration in the Ottawa sand and CCP were similar and indicative of drained conditions, whereas large, positive pore pressures in the FST were indicative of undrained conditions. The undrained shear strength estimated from MCPTs on FST (13 and 35 kPa) compared favorably and had a good agreement with undrained shear strength from triaxial tests. The effective stress friction angle for CCP based on MCPT (28.7° and 30.4°) yielded a conservative estimate relative to a previously determined effective friction angle via triaxial testing (36°).