Piezocone penetration testing in atlantic Piedmont residuum

Piezocone soundings were performed in residual silts and fine sands of the U.S. Atlantic Piedmont geologic province to investigate penetration pore-wa ter pressures and subsequent dissipation characteristics in these "nontextb ook" geomaterials. Piedmont residuum has been formed by the in-place weathe ring of Paleozoic schist, gneiss, and, granite. Pore-water pressures were m easured at two positions: midface of the cone tip u(1) and at the shoulder or behind the tip u(2). At the standard rate of 2 cm/s, penetration pore-wa ter pressures on the midface element are fairly high positive values (u(I) = +600 kPa +/- 200 kPa), yet readings at the shoulder element were negative (u(2) approximate to -90+ kPa). At an increased penetration rate of 20 cm/ s, midface and shoulder readings increased in magnitude and were positive ( u(1) approximate to +800 kPa and u(2) approximate to +200 kPa); however, me asured tip resistance q(c) exhibited an unusual decrease, per comparisons w ith data available in the literature. Upon halt of penetration, both u(1) a nd u(2) decayed quickly and reached hydrostatic values u(0) within 1-2 min.