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_qQ_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. Journal of Geotechnical and Geoenvironmental Engineering