干燥及饱水状态下裂隙岩石冻融特征研究

Freezing-thawing characteristics of fractured rockmass under dry and saturated conditions

岩体冻融风化作用主要受控于岩性、岩体结构、饱和状态及温变环境等因素。采取新疆寒区4种裂隙岩石进行温度变化下的冻融应变试验,得到了裂隙岩石在饱水及干燥冻融状态下的应变过程,即饱水状态下为8个阶段、干燥状态下为5个阶段;针对饱水裂隙岩石提出了冻融作用的胀缩率?,得到了不同岩性的?与冻融循环次数的拟合关系表达式,同时分析了在循环冻融过程中应变的变化规律,即裂隙岩石的冻胀阶段的微应变最大值都随循环次数的增加而增大。此外,通过在不同恒温下裂隙岩石冻融应变试验,分析了应变的变化规律,得到应变与不同恒温的拟合关系表达式;试验结果表明:裂隙岩石的?都随冻融次数的增加而增大,胀缩率的变化程度与不同岩样的孔隙率特征有关。饱水裂隙岩石在冻融过程中对温度具有较强的敏感性,损伤表现在温度损伤和冻胀损伤。

Freeze-thaw weathering of rock mass is mainly controlled by several factors, such as lithology, structure of rock mass, saturated water and temperature. In this study, the freezing and thawing strain tests were carried out on four kinds of fractured rock from the cold zone of Xinjiang. The strain processes of dry and saturated fractured rock were obtained under freezing and thawing conditions, respectively. It is found that the saturated fractured rock under eight strain stages, while the dry fractured rock experienced five strain stages. The swelling-shrinking ratio κ of saturated fractured rock was defined under the freezing and thawing action. Furthermore, the fitting relationships between the ratio κ of different lithology and freezing-thawing cycles were gained. At the same time, the variation law of strain in the process of cyclic freezing and thawing was analyzed, which revealed that the maximum micro-strain of fractured rock at the frost heave stage increased with the increase of the cycle number. Besides, the freeze-thaw strain tests on jointed rockmass were conducted under different constant temperatures, and the fitting relationships between strain and different constant temperatures were obtained as well. Testing results demonstrate that the ratio κ increased with increasing the freezing and thawing cycle. Moreover, the variation degree of swelling-shrinkage rate was related to rock porosity characteristics. In addition, saturated jointed rockmass was highly sensitive to the temperature during the freezing and thawing process, and the damage was reflected as the thermal and frost heaving damage.