Geomechanical Characteristics of Gneiss in Antarctica Determined by Freeze-Thaw Tests

초록

Freeze-thaw tests were performed on gneiss samples collected from Terra Nova, Antarctica, in order to examine and compare the properties of rocks that were slightly weathered (SW) and moderately weathered (MW). The tests were conducted under temperatures ranging from -20 +/- 2 degrees C to 20 +/- 2 degrees C. A cycle of testing consisted of 5 h of freezing followed by another 5 h of thawing under full saturation with water. In this paper, a total of 200 cycles of the freeze-thaw test were performed and were followed by measurements of porosity, absorption, ultrasonic velocity, and Shore hardness per each 20 cycles, with uniaxial compressive strength (UCS) determined every 50 cycles. The strength of the SW rocks decreased by approximately 0.07 MPa per single cycle, while that of MW rocks decreased by approximately 0.19 MPa per single cycle. During the 200 cycles of SW rocks, the absorption increased from 0.23% to 0.39% and the P-wave velocity decreased from 4,227 m/s to 3,596 m/s. Similarly, those of MW rocks changed from 0.65% to 1.6% and from 3,751 m/s to 2,877 m/s. In conclusion, it was inferred that the properties of SW rocks that experienced approximately 200-300 cycles of freeze-thaw became close to those of MW rocks.

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