Cantilever-Type Local Deformation Transducer for Local Axial Strain Measurement in Triaxial Test

The cantilever-type local deformation transducer (cantilever-LDT) was developed as an alternative local axial strain measurement device for triaxial testing. The transducer behaves as a cantilever beam and the deflection at its free-end is measured by the output from the strain gages attached near the fixed-end. By placing two cantilever-LDTs along the same vertical alignment but at different levels of a specimen, the local axial strain is obtained from the relative movements of two cantilever-LDTs. The advantages over the original-LDT proposed by Goto et al. (1991) are: (i) a linear calibration curve, (ii) capability to release itself at large strains, and (iii) larger working range. With a gage length of 50 mm, the resolution, accuracy, and working range are 0.0012 %, 0.003 %, and 6 %, respectively. The triaxial test results on heavily overconsolidated clay specimens show that the cantilever-LDT can be used satisfactorily to measure the local axial strain accurately, but the reliability depends very much on the quality of specimen preparation and setup.