Calibrating a t-bar factor for calcareous silt subjected to simple shear

Field tests suggest that the T-bar factor may vary over a large range for calcareous soils. As the T-bar penetrates very deep into soft soil, a full flow-round mechanism is formed around the T-bar. Examining the stress states around this mechanism suggests that soil elements are subjected to a varying stress state, and the element behaviour represents a combination of triaxial compression, simple shear, and triaxial extension conditions. This paper reports results of T-bar penetrometer tests performed at an elevated gravity of 150-g (where g is earth’s gravity) in a geotechnical centrifuge on a calcareous silty sediment collected from the North West Shelf of Australia. Once the centrifuge tests were completed, a tube sample was cored from the centrifuge strongbox. Two specimens were prepared from two reference depths, and undrained monotonic simple shear tests were carried out. The undrained shear strengths obtained from the simple shear tests were used to back analyse the T-bar bearing factor (NT-bar). A mean T-bar factor of 9.92 was found for the calcareous silt tested. A three-dimensional large deformation finite element analysis was conducted to find out the T-bar factor in an ideal soil, showing the potential for undertaking further parametric analyses using an appropriate constitutive model to develop a robust interpretation framework for T-bar test data.