Evaluation of Thawing and Stress Restoration Method for Artificial Frozen Sandy Soils Using Sensors

Abstract

Undisturbed frozen samples can be efficiently obtained using the artificial ground freezing method. Thereafter, the restoration of in situ conditions, such as stress and density after thawing, is critical for laboratory testing. This study aims to experimentally explore the effects of thawing and the in situ stress restoration process on the geomechanical properties of sandy soils. Specimens were prepared at a relative density of 60% and frozen at −20 °C under the vertical stress of 100 kPa. After freezing, the specimens placed in the triaxial cell underwent thawing and consolidation phases with various drainage and confining stress conditions, followed by the shear phase. The elastic wave signals and axial deformation were measured during the entire protocol; the shear strength was evaluated from the triaxial compression test. Monotonic and cyclic simple shear tests were conducted to determine the packing density effect on liquefaction resistance. The results show that axial deformation, stiffness, and strength are minimized for a specimen undergoing drained thawing, restoring the initial stress during the consolidation phase, and that denser specimens are less susceptible to liquefaction. Results highlight that the thawing and stress restoration process should be considered to prevent the overestimation of stiffness, strength, and liquefaction resistance of sandy soils.

Use of a Piezoelectric Bender Element for the Determination of Initial and Final Setting Times of Metakaolin Geopolymer Pastes, with Applications to Laterite Soils

“…In combination with piezoelectric sensors, the bender element can effectively determine the shear wave velocity and the initial shear modulus of materials in studies [ 2 , 3 , 4 , 5 , 6 ]. As an example, the bender element test was applied to studying soil characteristics, e.g., thawing and stress restoration in artificial frozen sandy soils [ 7 ], transition evaluation of fine sand from capillarity to cementation [ 8 ], expansion-induced crack propagation monitoring in rocks [ 9 ], response monitoring of transitional mixtures retaining the memory of in-situ overburden pressure [ 10 ], etc. For concrete materials, various studies can also be carried out using the bender element, e.g., the characterization of recycled concrete aggregate [ 11 ], evaluation of damage induced by alkali-silica reaction [ 12 ], etc.…”