Determination of soft clay parameters from CPTU tests, the FINCONE test sites revisited

Abstract

The CPTU test offers the possibility of continuous and reliable measurements of three independent readings, namely conetip resistance (qc ), sleeve friction (fs ), and penetration porewater pressure at the shoulder (u2 ), which can then be used toderive various soil parameters. The article presents a new approach for the determination of preconsolidation pressure (σp′),undrained shear strength (su ), and constrained modulus for the over-consolidated region M0 . The preconsolidation pressure isderived from net tip resistance qnet , excess pore pressure u, and effective tip resistance qeff using nonlinear functions basedon the pore pressure parameter Bq . Well-established transformation models are then utilized to derive su and M0 from σp′.The proposed transformation models proved to work well for all tested data irrespective of the sensitivity of the clay. Theyalso provided better prediction performance compared to previous, partly more site-specific solutions. In addition, the threeindependent solutions using either qnet , u, or qeff gave very consistent solutions giving almost equal depth-wise predictions.