Investigation of bearing capacity factor of T-bar penetrometer at shallow depths in clayey soils

The T-bar penetrometer is normally used in both in-situ and on the centrifuge to establish profiles of the undrained shear strength of fine-grain soils. However, adequate measurement of the undrained shear strength at shallow depths requires understanding the failure mechanism at these depths. For onshore and offshore structures such as pipelines, the assessment of soil parameters, in particular the undrained shear strength at shallow depth can be very critical to achieve both efficient and economic design. However, this requires the evaluation of the value of T-bar bearing factor (N_b) corresponding to both shallow and very shallow depths. This paper describes a series of geotechnical centrifuge tests undertaken using three different sizes of the T-bar penetrometer on two types of clayery soil. The results of the undrained strength obtained from each T-bar were compared with the results obtained from the bigger T-bars. The curves that describes the variation of the T-bar factor (N_b) versus the penetration depth were established from the comparison of all results obtained from the three different sizes of the T-bar. The results of (N_b) obtained in this study were compared with results obtained from both numerical and analytic solutions proposed in the literature. Generally, the experimental data obtained in this study presented N_b values higher than those predicted by others authors for all H/D ratios. However, the comparison indicates that the N_b values obtained in this study showed relatively reasonable agreement with those values obtained from the literature by adopting a non-homogenous strength profile.