Permeability determination from on-the-fly piezocone sounding

Solutions are developed for the steady, partially drained, fluid pressure field that develops around a moving penetrometer. These include rigorous solution for a point volumetric dislocation moving in a saturated elastic soil and an approximate solution for a pseudostatic, finite-volume, penetrometer moving in a nondilatant soil. These solutions provide a consistent framework for viewing the penetration process, and enable the nondimensional sounding indices of normalized tip resistance Q(t) friction factor F-r, and pore pressure ratio B-q, to be straightforwardly linked to important material properties of the soil, most notably that of permeability, via a nondimensional permeability K-D. This factor K-D is inversely proportional to penetration rate, and is directly proportional to both permeability and vertical in situ effective stress. Simple relationships are developed to link these nondimensional sounding metrics, via K-D. Most notably, the resulting simple relationship K-D = 1/B(q)Q(t) enables soil permeability to be determined from peak fluid pressures recorded on-the-fly. Importantly, these parameterizations enable plots of B-q-Q(t), F-r-Q(t), and B-q-F-r to be contoured for K-D, and hence for permeability. These plots define the relative superiority of using B-q-Q(t) data pairs over those for F-r-Q(t) and B-q-F-r, in defining permeability. Similarly, the feasible range of permeabilities that may be recovered from peak pressure data are defined; permeabilities must be sufficiently high that penetration is not undrained, and sufficiently low that the resulting pressure response is not null (fully drained). These limits are a natural product of the analysis and represent permeabilities in the range 10(-4)-10(-7) m/s. The utility of these characterizations is confirmed with data from two locations where cone soundings are correlated with independently estimated permeabilities.