Calibrating a T-bar factor for Calcareous Silt Subjected to Simple Shear

摘要

Field tests suggest that the T-bar factor may vary over a large range forcalcareous soils. As the T-bar penetrates very deep into soft soil, a fullflow-round mechanism is formed around the T-bar. Examining thestress states around this mechanism suggests that soil elements aresubjected to a varying stress state, and the element behaviour representsa combination of triaxial compression, simple shear, and triaxialextension conditions. This paper reports results of T-bar penetrometertests performed at an elevated gravity of 150-g (where g is earth’sgravity) in a geotechnical centrifuge on a calcareous silty sedimentcollected from the North West Shelf of Australia. Once the centrifugetests were completed, a tube sample was cored from the centrifugestrongbox. Two specimens were prepared from two reference depths,and undrained monotonic simple shear tests were carried out. Theundrained shear strengths obtained from the simple shear tests wereused to back analyse the T-bar bearing factor (NT-bar). A mean T-barfactor of 9.92 was found for the calcareous silt tested. A threedimensionallarge deformation finite element analysis was conducted tofind out the T-bar factor in an ideal soil, showing the potential forundertaking further parametric analyses using an appropriateconstitutive model to develop a robust interpretation framework for Tbartest data.