Abstract:
This paper discusses the interpretation of the pore water dissipation curves obtained during a piezocone test with the prime objective of determining the seismic behaviour of fine-grained soil. The pore pressure dissipation approach was attempted to perform a faster diagnosis of liquefiability of fine-grained soils where the ground water table is almost at the surface. Furthermore, because non-plastic silts are very difficult to sample for laboratory testing, such an in situ measurement appears to be the only realistic method for the purpose. Most of the dissipation tests were conducted by using the u(2) filter on the neck of the probe, and the others were performed by using the u(1) filter where the piezometer is located on the cone tip. Penetration was arrested at depths where the presence of silts had been detected by previous sounding and drilling, and t(50), t(90) and t(100) were determined analytically. The results indicate that t(90) values have a notable potential for diagnosing a potential for liquefaction. This was demonstrated by a t90 of 300 s or less for liquefiable layers, whereas considerably longer periods are required for non-liquefiable silts similar to clays. This feature is illustrated by the presentation of several types of dissipation curves.
