Self-boring pressuremeter testing in spearwood dune sands

Martin Fahey, James A. Schneider and Barry M. Lehane

The self-boring pressuremeter (SBP) offers the possibility of direct determination of parameters for sand in situ that cannot be obtained directly by any other means. The paper presents the results of SBP tests in sand in Perth at two locations: three boreholes in the Perth CBD and three boreholes at a test site in Shenton Park. The tests were carried out in Spearwood Dune sands (at both locations) and in Guildford/Perth Formation sands (in the CBD boreholes). The results presented show that the friction and dilation angles determined from the test are reasonable for the sands investigated. The Ko values obtained from the “liftoff” pressures show considerable scatter but, with no benchmark against which to compare them, it is impossible to state whether they are correct or not. With regard to the stiffness parameters, the results show that there is no simple relationship between small-strain stiffness Go and the larger-strain stiffness Gur measured in unload-reload loops in the SBP. For the tests in the CBD, the tendency observed is that Go is higher for the older Guildford/Perth Formation sands than for the younger Spearwood Dune sands, but the rate of “softening” for the former is greater than for the latter. However, the Spearwood Dune sands at Shenton Park show a much higher rate of softening than the Spearwood Dune sands in the CBD, probably due to partial saturation and/or slight cementation in the former.