A field permeability measurement technique using a conventional self-boring pressuremeter

A new permeability measurement method using a conventional self-boring pressuremeter (SBP) is described. The SBP self-bores to a predetermined depth. It is then retracted a short way, leaving a well-defined cavity in the ground. Water is pumped into the cavity at a constant rate, and the permeability is derived from the change in injection pressure with injection How, rate. A sequence of tests at a given horizon involves cavities of varying lengths, including a flush bottom or zero length cavity. In homogeneous materials the data from variable cavity lengths can be used to determine the anisotropy ratio. In heterogeneous materials the same data may allow the scale dependence to be evaluated if the anisotropy ratio can be independently obtained. Potential measurement errors are discussed in relation to smearing, temperature effects and leakage along the instrument. Results from Gault clay, London clay and Bothkennar clay are presented, with corroborating laboratory and other field test results where available. The preliminary assessment of scale dependence at these sites corresponds well to the degree of heterogeneity identified for the tested clays through visual observation.