Placement of embedded pressure cells

INTRODUCTION The determination of stresses within an elastic medium is a fundamental problem for various research communities, particularly when tests are being carried out at less than full scale. The laws associated with testing at model scale have been well described by Nielsen (1977) with particular reference to silo testing, and by Scho®eld (1980) with reference to centrifuge modelling. The research community in soil mechanics has considerable experience in the use of centrifuge tests for the determination of phenomena in soils at model scale (e.g. Boulebnane et al., 1994) and the accuracy of centrifuge modelling is con®dently known. Pressure measurement in a granular solid can be achieved by cells (called `free-®eld' or `embedded' cells) placed within the medium. This note shows that suitable technology exists that can be used by any laboratory to reliably determine pressures within a medium. In addition, it shows that the centrifuge could be used as a method of practical calibration for cells, and that such a calibration method could be used in the future determination of appropriate advances in cell design. Values of K0 for a Fontainebleau sand are measured.