The effect of drained pre-shearing on the undrained behaviour of loose sand with a small amount of fines
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RESEARCH PAPER
The effect of drained pre-shearing on the undrained behaviour of loose sand with a small amount of fines D. C. Bobei • D. Wanatowski • M. M. Rahman S. R. Lo • C. T. Gnanendran
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Received: 7 December 2011 / Accepted: 5 November 2012 / Published online: 4 December 2012 Springer-Verlag Berlin Heidelberg 2012
Abstract Stress history is recognised to play a major role in determining stress–strain behaviour of soil in undrained shearing. Most experimental studies on the effects of stress history on undrained behaviour are mainly limited to clean sand. In this paper, an experimental study carried out to investigate the effect of stress history on the undrained behaviour of loose sand with a small amount of fines is presented. Four series of triaxial compression tests, with different types of drained stress histories to near-failure prior to commencement of undrained shearing, were conducted. The experimental results indicate that drained preshearing to near-failure affects significantly the undrained behaviour of loose sand. In general, the drained preshearing improves the subsequent undrained behaviour of loose sand to the extent that liquefaction may not occur. It is shown that the effect of drained pre-shearing cannot be explained by the reduction in void ratio induced by drained
D. C. Bobei Aurecon, 116 Military Road, Neutral Bay, NSW 2089, Australia D. Wanatowski (&) Nottingham Centre for Geomechanics, Division of Materials, Mechanics and Structures, Faculty of Engineering, University of Nottingham, University Park, Nottingham NG7 2RD, UK e-mail: [email protected] M. M. Rahman School of Natural and Built Environments & Barbara Hardy Institute, University of South Australia, Mawson Lakes, SA 5095, Australia S. R. Lo C. T. Gnanendran School of Engineering and Information Technology, University of New South Wales Canberra (UNSW Canberra), Australian Defence Force Academy (ADFA) Campus, Canberra, ACT 2600, Australia
pre-shearing. However, for specimens subjected to drained pre-shearing, p0d0 /p0u0 can be used as a parameter for analysing the effects of preloading history. It is also shown that for different preloading histories that brought the same change in void ratio or state parameter, drained preshearing to near-failure is the most effective, whereas precompression alone is the least effective in improving subsequent undrained behaviour of loose sand. Keywords Laboratory tests Pre-shearing Sand with fines Static liquefaction Steady state Triaxial
List of symbols e Void ratio ecs Void ratio at critical state ed0 Void ratio at the start of drained pre-shearing eu0 Void ratio at the start of undrained shearing 0 p Mean effective stress, p0 = (r01 ? 2r03 )/3 Reference stress in Eq. 1, pa = 100 kPa pa p0cs Mean effective stress at critical state Mean effective stress at the start of pre-shearing p0d0 Mean effective stress at the start of undrained p0u0 shearing q Deviator stress, q = r1 - r3 qmax Maximum deviator stress qmin Minimum deviator stress e1 Major principal st
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