Abstract

Research has already demonstrated advantages in performing piezoball tests when compared to piezocone in estimating the soil undrained shear strength (Su) along the stratigraphy and remolded strength (Sur) through cyclic tests, showing a shorter range of strength correction factors (N) and lower dependence on the soil stiffness index (Ir). Another possible application is estimating the remolded shear strength directly from penetration (qin) and extraction (qext) measurements without requiring cyclic tests. This research performed piezocone, vane, and piezoball tests (standard and cyclic) in a soft soil deposit in southern Brazil. Additionally, undisturbed samples were collected for characterization. The in situ investigation resulted in cone and ball factors in accordance with the international practice recommendation, resulting in similar profiles of undrained strength Su which increases with depth from 3 to 14 kPa and constant values of remolded undrained strength Sur. Regarding estimating the Sur through direct measurements of penetration and extraction of the piezoball, it was necessary to carefully evaluate the time laps between probe insertion and extraction to avoid overestimating the remolded strength.

Abstract

The present paper aims to validate the applicability of a piezoball test equipped with pressure transducers at the probe’s tip, middle, and equator faces to estimate the coefficient consolidation behavior of a soft soil deposit. The proposals of Mahmoodzadeh et al. (2015) and Liu et al. (2023), derived from numerical solutions, can be adopted to estimate horizontal coefficients of consolidation (ch) through the piezoball dissipation measurements. The dissipations tests were performed at depths of 4, 6, 8, and 10 m and were conducted up to at least about 70% of dissipation of the excess pressure generated during the penetration, except for the test at a depth of 4m, done at 85%. Results were directly compared with piezocone, and the estimated values for the consolidation coefficient were similar for all methodologies applied, both at the face and equator positions.