Sandstone is widely distributed in cold regions and the freeze-thaw deterioration of them has caused many geological engineering disasters.As an important and direct index of frost resistance,the strength loss of sand...Sandstone is widely distributed in cold regions and the freeze-thaw deterioration of them has caused many geological engineering disasters.As an important and direct index of frost resistance,the strength loss of sandstones under freeze-thaw actions should be investigated to provide a guidance for the stability assessment of geological engineering.In this research,the UCS(Uniaxial compressive strength)loss of six typical sandstones with different water contents after 0,20,40 and 60 freeze-thaw cycles was measured in the laboratory.The experimental results indicated that the freeze-thaw damage was more serious in sandstones containing high water contents,and the critical saturations for causing a significant loss of UCS under freeze-thaw were 60%-80%for these sandstones.Below this critical saturation,the UCS loss of the sandstones was mainly caused by water weakening rather than freeze-thaw damage.Besides,a developed strength prediction model was proposed by combining the exponential decay function and multiple linear regression method.The initial porosity,elastic modulus and tensile strength of fresh sandstones were a good parameter combination to accurately determine the decay constant in this developed model.The main novelty of this model is that it can accurately and easily estimate the UCS loss of sandstones after any freeze-thaw cycle only using the initial parameters of fresh sandstones,but it does not need to perform freeze-thaw and mechanical strength experiments.This study not only provides an accurate prediction model of UCS under freeze-thaw,but also makes a contribution to better understanding the frost resistance mechanism of sandstones.展开更多
Saturated vapor pressure, critical evaporation temperature and evaporation loss rate of Fe-Ga alloy were calculated under different conditions of Ga and Fe contents with activity coefficients. The relationship between...Saturated vapor pressure, critical evaporation temperature and evaporation loss rate of Fe-Ga alloy were calculated under different conditions of Ga and Fe contents with activity coefficients. The relationship between the change of Ga content and melting time was determined. The results demonstrated that saturated vapor pressure of Ga was higher than that of Fe under the same conditions. The difference value of critical evaporation temperature of Ga with and without Ar was nearly 800 K. The critical evaporation temperature of Fe was higher than that of Ga under vacuum, indicating that Ga was more volatile than Fe. At 1800 K, the evaporation rate of Ga was 84 times higher than that of Fe in the melt of Fe81Ga19 alloy. Under this condition, the change of Ga content and smelting time kept a linear relationship. The higher the temperature was, the faster the Ga content decreased, which was consistent with theoretical calculations.展开更多
基金supported by National Natural Science Foundation of China(Nos.42072300 and 41702291).
文摘Sandstone is widely distributed in cold regions and the freeze-thaw deterioration of them has caused many geological engineering disasters.As an important and direct index of frost resistance,the strength loss of sandstones under freeze-thaw actions should be investigated to provide a guidance for the stability assessment of geological engineering.In this research,the UCS(Uniaxial compressive strength)loss of six typical sandstones with different water contents after 0,20,40 and 60 freeze-thaw cycles was measured in the laboratory.The experimental results indicated that the freeze-thaw damage was more serious in sandstones containing high water contents,and the critical saturations for causing a significant loss of UCS under freeze-thaw were 60%-80%for these sandstones.Below this critical saturation,the UCS loss of the sandstones was mainly caused by water weakening rather than freeze-thaw damage.Besides,a developed strength prediction model was proposed by combining the exponential decay function and multiple linear regression method.The initial porosity,elastic modulus and tensile strength of fresh sandstones were a good parameter combination to accurately determine the decay constant in this developed model.The main novelty of this model is that it can accurately and easily estimate the UCS loss of sandstones after any freeze-thaw cycle only using the initial parameters of fresh sandstones,but it does not need to perform freeze-thaw and mechanical strength experiments.This study not only provides an accurate prediction model of UCS under freeze-thaw,but also makes a contribution to better understanding the frost resistance mechanism of sandstones.
基金Item Sponsored by National Natural Science Foundation of China(51161019)Project of Department of Science and Technology of Jiangxi Province of China(20133BBE50011)Project of Department of Science & Technology of Jiangxi Province of China(20141BDH80025)
文摘Saturated vapor pressure, critical evaporation temperature and evaporation loss rate of Fe-Ga alloy were calculated under different conditions of Ga and Fe contents with activity coefficients. The relationship between the change of Ga content and melting time was determined. The results demonstrated that saturated vapor pressure of Ga was higher than that of Fe under the same conditions. The difference value of critical evaporation temperature of Ga with and without Ar was nearly 800 K. The critical evaporation temperature of Fe was higher than that of Ga under vacuum, indicating that Ga was more volatile than Fe. At 1800 K, the evaporation rate of Ga was 84 times higher than that of Fe in the melt of Fe81Ga19 alloy. Under this condition, the change of Ga content and smelting time kept a linear relationship. The higher the temperature was, the faster the Ga content decreased, which was consistent with theoretical calculations.
