Volume 28, Issue 5 (September 2005)
New Local System of Measurement of Axial Strains for Triaxial Apparatus Using LVDT
This paper presents a new local system of measurement of axial strains for triaxial apparatus using LVDT. The bodies of four nonsubmersible transducers are supported by an independent circular ring, while the rods are simply put on local targets (pins pushed through the membrane into the sample). A flexible metal plate is used to attach the body of the LVDT to the circular ring and a nonrigid connection is considered between the rod and the pin. These original developments allow the system to investigate the soil behavior in large strains, up to 15 × 10−2 m/m, and to accommodate the radial deformation, tilting, and usually inevitable barreling of the sand specimen. The soil stiffness in the small strain domain, less than some 10−5 m/m, can be evaluated with good accuracy, as well as its evolution during triaxial compression or extension tests. The assessment of errors is discussed and the performance of the device is shown with results of tests on Hostun RF sand.