LVDTs-based radial strain measurement system for static and cyclic behavior of geomaterials

The importance of local strain measurement on triaxial specimens has been widely recognized. The design of the radial strain measurement system has been relatively less advanced as compared to the axial strain measurement system. In this study, a new linear variable differential transformers (LVDTs)-based radial strain measurement system is developed. Firstly, the setup and methodology of the new radial strain measurement system along with the advantages are described in detail. The detailed calibration process of the measuring system is introduced, together with the error analysis. Also, the long-term performance of this new system under different levels of cell pressure and the varying temperature is examined. The paper also presents the radial strain measurement results of triaxial tests performed on natural rubber, quartz sand specimen, and cement-stabilized marine deposit column. In particular, the performance of the new measurement system under cyclic loading condition is evaluated, which is rarely reported in the existing literature. The calibration and test results confirm that the new measurement system can provide reliable and accurate radial strain results and minimize any associated measurement bias as the specimens are subjected to both static and cyclic loadings.