The triaxial cell is used to determine soil properties of intact and reconstituted soil specimens via stress path testing in compression and extension. Multi-path stress path testing is particularly powerful in being able to give the soil a complex stress history to mimic field conditions. Research in recent years has shown the need to measure strains locally to accurately capture the non-linear nature of soil.
There are currently two triaxial apparatus available for high quality soil testing on 38mm or 50mm diameter soil samples. Both use hydraulic digital pressure controllers to control cell pressure, back pressure and ram load and both are equipped with local strain measurement devices. These are linearly variable differential transformers (LVDT) for axial strain and proximity sensors for radial strain). The facility to measure very small strain stiffness via S and P wave velocity is additionally available on one apparatus.