In-situ evaluation of undrained shear strength from seismic piezocone penetration tests for soft marine clay in Jiangsu, China

Abstract

Abstract Undrained shear strength, s u is an important geotechnical parameter of soft clay. The seismic piezocone test (SCPTU) can provide valuable information regarding in-situ soil behavior and stratigraphy in geotechnical site investigation. Therefore, the relationships of s u with the data obtainable in SCPTU testing have long been a topic of research interest. The objective of this paper is to evaluate the su of marine clay from Lianyungang in Jiangsu Province of China. First, existing methods for obtaining the su values of clay soils from basic SCPTU penetrometer readings are reviewed. The relationships between su and SCPTU parameters at the Lianyungang site are then determined. su values derived from field vane testing and CPTU results are also discussed. The relationship between su and the pore pressure cone factor is proposed and the pore pressure cone factor is shown to be approximately about 8.03, providing a means to estimate su. A previously developed method of using maximum excess pore pressure is also utilized here for the overconsolidated clays within the stratigraphic sequence. Additionally, a relationship between su and shear wave velocity is proposed, linking stiffness with strength in a stiffness-strength correlation. The derived correlations are in accordance with those previously reported in the literature, and the results also showed that SCPTU tests can be used comprehensively to estimate the su of Jiangsu marine clay.