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.
Highlights
With the recent increase in demand for the complicated and extensive infrastructure, construction is being conducted on comparatively weak deposits, such as loosely compacted granular sand
The bender elements are extruded as a cantilever beam to have better contact with the specimen
This study aims to estimate the effects of the thawing and in situ stress restoration This aims tostrength, estimateand the liquefaction effects of theresistance thawing of and in situfrozen stress sandy restoration process onstudy the stiffness, artificial soils
Summary
With the recent increase in demand for the complicated and extensive infrastructure, construction is being conducted on comparatively weak deposits, such as loosely compacted granular sand. The undrained shear response of the deposits, which is one of the most important geomechanical characteristics, is primarily affected by the soil fabric, density, and stress conditions [1]. The most effective method for evaluating engineering parameters (i.e., the in situ strength and deformation characteristics under static and dynamic loading conditions) can be achieved through laboratory tests using undisturbed specimens. Considerable attention has been focused on obtaining undisturbed samples from sand deposits to evaluate soil characteristics (e.g., log information, shear strength, and liquefaction resistance). An undisturbed sandy sample cannot be obtained using conventional sampling methods. The artificial ground freezing method is considered to be the most effective technique for obtaining undisturbed soil samples from cohesionless sandy deposits [3,4,5,6]
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