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Visualizing the Tube Sampling Disturbance Strain Path

Generally soil samples were retrieved by pushing a tube into the ground, a process called tube sampling. Though better sampling techniques do exist, the required technical and financial support made them impractical for many projects so tube sampling is still the most widely used sampling method around the world. It has long been recognized that this sampling process can cause significant disturbances to the soil, so the soil samples obtained do not truly reflect the in-situ soil state. Though numerous researchers have studied sampling disturbances experimentally, the real movement of soil during tube sampling has never been measured. It is easy to recognize the practical difficulties of such measurements: the tube sampling happens underground and there is no means to see into the soil.

Geotechnical research has been advancing rapidly and researchers are now equipped with a new series of experimental techniques to assess this old problem. The development of transparent soil (Iskander et al., 2002; Liu et al., 2003) made it possible to observe displacement inside the soil body. The application of Particle Image Velocimetry (PIV, White et al., 2003) enables the accurate measurement of whole field soil movement. A physical modeling system combing these two were successively used to obtain strain fields inside the soil during the installation of straight and augered piles (Ni et al, 2009). It is proposed in this research project to exploit these new methods and establish an innovative physical modelling system to investigate the tube sampling disturbance.

For more information please contact Dr Qing Ni.