Conventional triaxial apparatus has limited capabilities for advanced testing of frozen soils, such as loading under controlled temperature and volume change measurements. To bridge this gap, in this paper, we presented a novel ultrasound-integrated double-wall triaxial cell designed specifically for stress and strain-controlled, as well as temperature-controlled testing of frozen soils. Monitoring pore ice content during triaxial tests in frozen soils poses a significant challenge. To overcome this hurdle, we developed an in-cell ultrasonic P wave measurement setup, which was integrated into the triaxial device to monitor freeze advancement at any stage of the test. We proposed a three-phase poromechanics-based approach to estimate the pore ice content of frozen soil samples based on the P-wave velocity. A series of creep tests under different freezing temperatures have been undertaken for frozen soil samples to investigate the effect of ice content and temperature on the volumetric deformations of frozen soils during creep tests. Our study demonstrates the potential of the proposed ultrasound-integrated double-wall triaxial apparatus for creep tests of frozen soils.
