Department of Civil and Environmental Engineering, University of California at Berkeley, Berkeley, CA 94720, USA.
School of Civil, Environmental and Architectural Engineering, Korea University, Seoul 02841, Korea.
Sensors (Basel). 2021 Mar 9;21(5):1916. doi: 10.3390/s21051916.
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.
未扰动的冻结样本可以通过人工冻结法有效地获得。此后，解冻后恢复原位条件，如应力和密度，对于实验室测试至关重要。本研究旨在通过实验探讨解冻和原位应力恢复过程对砂土的岩土力学性质的影响。将相对密度为 60%的试样在 -20°C 下以 100kPa 的竖向应力进行冻结。冻结后，将三轴室内的试样进行解冻和固结阶段，采用不同的排水和围压条件，随后进行剪切阶段。在整个试验过程中测量弹性波信号和轴向变形；从三轴压缩试验评估剪切强度。进行单调和循环简单剪切试验以确定堆积密度对液化阻力的影响。结果表明，对于经历排水解冻的试样，轴向变形、刚度和强度最小，在固结阶段恢复初始应力，并且更密实的试样不易发生液化。结果表明，应考虑解冻和应力恢复过程，以防止对砂土的刚度、强度和液化阻力的高估。
