多重模拟条件下贺兰山岩画病害形成机理研究

Research on the mechanism of rock painting deterioration in Helan Mountain:A multiple simulation approach

针对长期暴露于自然环境中的宁夏贺兰山岩画所产生严重病害致使其濒危的问题,分别设置了干燥、中性水环境、酸性水环境模拟文物遗址赋存环境,开展干湿冻融循环试验、单轴压缩试验、扫描电镜测试与X射线衍射测试,分析宏观外表、微观形貌、物理性质和矿物成分变化,研究病害的形成机理。研究结果表明,干燥环境、中性水环境和酸性水环境中的主要劣化病害分别为轻度粉状剥落、裂隙发育和重度酥粉状剥落。岩石的单轴抗压强度以近似指数函数的形式下降,孔隙率以近似指数函数的形式上升,其中酸性环境下变化幅度最大,中性环境下次之,干燥环境下最小。表面剥落、裂隙与载体坍塌病害形成的主要原因分别为酸雨溶蚀导致的成分变化、温湿度变化导致的微裂隙扩展联通与微观结构损伤导致的强度下降。研究结果可为贺兰山岩画的保护工作提供理论依据。

Helan Mountain rock paintings in Ningxia has been exposed to the natural environment for a long time,resulting in serious deterioration which makes it endangered.Therefore,three conditions,including dry,neutral water,acid water,were set up to simulate the environment of cultural relics sites.The dry-wet-freeze-thaw cycle test,uniaxial compression test,scanning electron microscope test and X-ray diffraction test were carried out.The changes of macroscopic appearance,microscopic morphology,physical properties and mineral composition are analyzed to study the deterioration mechanism.The results show that the main deterioration in dry,neutral water and acid water are mild powdery peeling,crack development and severe powdery peeling,respectively.The uniaxial compressive strength decreases in the form of approximate exponential function,the porosity increases in the form of approximate exponential function,and the change ranges of physical quantities are the largest in acidic environment,followed by neutral environment and dry environment.The main reasons causing the surface spalling,crack and carrier collapse are the change of composition caused by acid rain dissolution,the expansion and connection of micro crack caused by temperature-humidity change and the decrease of strength caused by microstructure damage.The research results would provide a theoretical basis for protection of Helan Mountain rock paintings.