Nor Azizi Yusoff - Research Student

Telephone: 25056
Room: E104

email : na.yusoff@sheffield.ac.uk

Research Group

Research Project

Effect of Rate of Shearing on the Resistance of Fine Grained Soils

A wide range of industrial applications, on land and offshore, require the solution of time domain problems and an associated understanding of rate effects in clay soils. In recent decades many researchers have examined the correlation between shear strength of soils and variation of shear strain rate (Casagrande and Wilson, 1951; Richardson and Whitman, 1963; Roscoe, 1970; Craig, 1983) and it is generally accepted that the strength increases by 5 -20 % for each order of magnitude increase in shear strain rate (Graham et al., 1983). This has been observed in the field (e.g. Holeyman et al. 2001; Brown et al., 2006) and investigated more fully in physical model tests in a large calibration chamber (Brown, 2004; Nguyen, 2005). New rapid load pile testing methods and push-in pile installation techniques have highlighted the need for a better understanding of rate effects in clays. In order to gain an insight to the problem, a new Rowe Cell-Vane Shear apparatus has been developed with a servo motor to cover a wide range of rate of shearing ranging from 1x10-4 m/s to 1m/s. Three different vane dimensions with L/D ratios 1, 2 and 4 will be placed inside the consolidometer during the consolidation process. After consolidation, vane tests will be conducted by applying various torques monitored by a torque transducer. Simultaneously, the pore water pressures will also be measured during and after the test by four pore pressure transducers inside the consolidation cell. Three different mixtures of Kaolin-Sand-Silt (KSS) with widely varying plasticity will be consolidated around the vanes in the cell at different consolidation ratios (OCR) 1, 2, 4 and 8 in order to examine the effect of the rate of shearing on the shearing resistance of fine-grained soils. The aims of this research are to establish a relationship between rate effects, material characteristics and stress history with the aim of improving predictions of pile load capacity and stiffness using data from rapid load pile tests and pile push-in installation records.