A versatile triaxial apparatus for frozen soils

Settlement and damage to infrastructures in permafrost regions depend in part on the mechanical properties of permafrost layers. In order to get a better understanding of the mechanical behavior of frozen soils, a triaxial apparatus was developed with three new features in addition to the traditional functions. The first is the accurate temperature control, which allows temperature to fluctuate within ± 0.1 °C during the loading period, and ± 0.02 °C before loading, so as to get a better understanding of the mechanical properties of frozen soils under temperatures close to thawing point. The second feature is used to measure K0 of frozen soils. A highly-sensitive radial strain measurement device was designed and the K0 state can be accurately maintained by automatically adjusting the radial pressure when radial deformation changes more than ± 10 μm. The third is the precise measurement of the volumetric strain through the displacement of axial and radial loading pistons. The capabilities of the triaxial apparatus are shown using a series of test results. It is considered to be a promising tool to investigate the mechanical properties of frozen soils.