Volume 8, Issue 4 (December 1985)
Repeated Load Triaxial Testing of Frozen and Thawed Soils
This paper describes the equipment and methodology used to determine the resilient properties of granular soils that exhibit thaw-weakening behavior. Such soils suffer a significant loss in stiffness as the result of freezing and thawing and subsequently experience an increase in stiffness during a recovery phase. The recovery phase results from gradual desaturation of the thawed soil and is characterized by an increase in the soil moisture tension level. We have developed a means to simulate this freeze-thaw-recovery process in the laboratory that calls for testing specimens several times at soil moisture tension levels corresponding to field observations.
We have designed test cells with removable bases to facilitate this sequential testing procedure. A given specimen remains on one cell base throughout the course of testing, thus avoiding excessive handling and allowing the material to remain in contact with a porous element built into the base. The porous element is part of a tensiometer system that continuously monitors the moisture tension level of the soil.
The cells are equipped with axial and radial displacement transducers and a load transducer, which, along with the other cell components, are assembled about each mounted specimen to be tested. All transducers are interchangeable between our larger and smaller triaxial cells. The cells receive 152.4-mm-diameter, 381-mm-long specimens and 50.8-mm-diameter, 127-mm-long specimens, respectively.