不同条件下贺兰口岩画载体岩石冻融损伤特征与机制研究

Study on the characteristics and mechanisms of freeze-thaw damage of rock carrier of Helankou rock paintings under different conditions

独特的气候特征和复杂的水化学环境所导致的冻融和化学溶蚀作用是贺兰口岩画载体变质砂岩片状起翘与脱落、刻痕变浅的重要原因。通过对分别浸泡于蒸馏水和浓度均为0.5 mol/L的Na2SO4,Na HCO3和CaCl2溶液的0,15,30,45和60次冻融循环后的岩石试样,进行质量、弹性波速、单轴抗压强度测试,系统探索岩画载体岩石在化学和冻融共同作用下的损伤特征。通过扫描电子显微镜(SEM)、X–射线衍射分析(XRD)以及基于孔隙率变化为基础建立损伤变量,对试样累积性损伤机制进行定性和定量联合分析。结果表明:在不同条件的冻融循环过程中,岩石宏观性质出现不同程度的累积性损伤,而且这种损伤是由冻胀、溶蚀和盐分结晶出现不同组合情况而造成试样孔隙的类型、数量和联通情况产生了差异而导致的。

Unique climatic characteristics and complex hydrochemical environments lead to freeze-thaw and chemical dissolution combining action,which is an important reason for the exfoliating and nick becoming shallow of the metamorphic sandstone carrier of the Helankou rock paintings.The mass,elastic wave velocity and uniaxial compressive strength of rock samples after 0,15,30,45 and 60 freeze-thaw cycles respectively immersed in distilled water and Na2 SO4,Na HCO3 or CaCl2 solution of 0.5 mol/L concentration were tested,and the damage characteristics of rock paintings carrier under the combined action of chemical and freeze-thaw were systematically explored.The cumulative damage mechanism was analyzed qualitatively and quantitatively by scanning electron microscopy(SEM),X-ray diffraction analysis(XRD)and the damage variable based on the change of the porosity.The results show that the rock samples present different degrees of cumulative damage in the process of freezing and thawing cycles under different conditions and that the damage is caused by the differences of the type,quantity and connection of the sample pore aroused by different combinations of frost heave,dissolution and salt crystallization.