Permeability of coarse silts using dissipation tests in cone penetration test: Case study, Finninmäki testing site

Dissipation tests were performed at the Finninmäki testing site, Tampere, Finland, through the cone penetration test (CPTu). In these tests, both contractive and dilative behaviors were observed. The parameter $t_{50}$, the time when 50 $\mathrm{\%}$ of initial pore pressure, $u_2$, dissipates, was computed for the tests using three methods proposed in literature. Then, soil permeability, $k$, was estimated following two approaches, using either $t_{50}$-based empirical equations or CPTu-based methods. It was observed that the $t_{50}$ values interpreted from the three methods were considerably different. The differences in the estimated $t_{50}$ values led to considerably variable $k$ estimations approximated by the $t_{50}$-based empirical equations. On the other hand, the CPTu-based $k$ estimates were considerably different from the $t_{50}$-based estimations. Besides, three undisturbed soil samples were taken by the 132 mm TUNI tube sampler in the field. These samples were used in the lab to measure the soil permeability, $k$, experimentally. Comparison of the experimental measurements with the $k$ estimates highlighted the significance of the improvement required for the available empirical equations to estimate $k$ for the studied coarse silts.