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valves with closed loop control of vertical, cell and back pressure; two pressure transducers for external feedback on cell and back pressure; a volume changer; and a computer. Two bender elements transmitter and receiver (each consisting of two thin piezoceramic plates)-were embedded in the base pedestal and at the top platen of the triaxial cell respectively. Each of the elements protruded 4 mm into a soil sample. The bender elements generate shear waves in a soil sample and detect their arrivals at the sample edges, allowing the initial shear modulus Go of the soil to be obtained. A In this study the effect of ageing on the small-strain L stiffness of overconsolidated kaolin clay is investigated. Kaolin clay samples are remoulded in the laboratory with the same dry density and moisture content. The samples are saturated, isotropically consolidated, and swelled to obtain an overconsolidation ratio (OCR) of 2. Up to this point all the samples have undergone the same stress history. The samples are then left to age under the same mean effective pressure for different periods of time, and after that are subject to undrained shearing. The tests are conducted in a computer-controlled triaxial apparatus fitted with bender elements and non-contact proximity sensors. The bender elements are employed for dynamic measurements of Go (e.g. Viggiani & Atkinson, 1995; Arulnathan et al., 1998), and the proximity sensors can be used for static measurements of local axial and radial strains (e.g. Hird & Yung, 1989; Scholey et al., 1995). The results of measurements by bender elements at very small strains (less than 0.001%) show an increase of 14% in Go after 7 days of ageing.
Authors:Rammah, K.I. and Val, D.V. and Puzrin, Alexander
Index Terms:geomechanics; GeomechanicsGroup; Puzrin, Alexander; Rammah, K.I.; Val, D.V.
Further Information:Date published: 2004