Triaxial Testing of Frozen Soils—State of the Art

Mechanical properties of frozen soils are invaluable input parameters when designing building foundations or infrastructure in perennial frost areas. Mechanical properties are also important for natural resource development in the north, such as for mining and petroleum-industry-related projects. One of these properties is the shear strength of frozen soil under varying temperatures and loading times. If shear strength is estimated instead of measured, risks for failure or overdesign exist. Therefore, it is important to accurately measure the strength of frozen soils. Two main methods exist for measuring the shear strength of soils: the direct shear test (ASTM D3080) and the triaxial compression test (ASTM D4767, ASTM D7181, and ASTM D2850). Although these tests are routinely used for unfrozen soils, not much published information exists regarding their use for frozen soils. Yet the industry needs this property for planning their operations in cold regions. Therefore, ASTM International Subcommittee D18.19 on Frozen Soils and Rock has started a process of developing new standards for mechanical properties of frozen soils. Of special interest is the dynamic triaxial testing of frozen soils. The purpose of the study reported here was to collect information and practices for the current usage of triaxial testing for frozen soil, under either static or dynamic loading conditions. According to the results of the literature review, researchers use various modified testing systems and sample configurations, and unfortunately they do not always describe them fully. So, standardization of the testing method would be beneficial for creating comparable results between laboratories. The measurement of small strains and deformations in dynamic tests was reported to be challenging. A Split-Hopkinson pressure bar is currently being developed as a means to overcome this problem. Another challenge under investigation is the accuracy of the strain rate control. The synthesized information can be used as a starting point in the development of a standard test method for the dynamic triaxial testing of frozen soils.