不同条件下贺兰口岩画载体变质砂岩干湿损伤特征与机制研究

Dry-wet damage characteristics and mechanism of metamorphic sandstone carrying Helan mouth’s rock paintings under different conditions

干湿与化学损伤作用是继冻融和化学损伤又一种导致与加速贺兰口岩画载体变质砂岩风化进程的重要原因。研究通过对岩画载体岩石在不同溶液下进行15,30,45,60,90,120,150及180次的干湿循环,以此来探索岩画载体岩石在干湿和化学溶液共同作用下的损伤特征。研究表明:试样的质量、纵波波速、单轴抗压强度、应力-应变特征总体呈现随干湿循环次数的增加而逐渐差异性衰减的规律,且变化速率呈现3个阶段,具有15和60次2个明显的拐点。结合SEM和XRD分析试验对试样的微观结构和成分进行定性分析,并以孔隙率为中间基础建立了损伤变量与宏观试验指标的定量联系。最后通过分析内部损伤机制得到试样由不同干湿条件导致的水解、化学溶蚀以及盐结晶和溶解3种作用差异性组合而造成岩石内部线性孔隙和孔洞数量和连接情况出现了不同而形成的,这为岩画科学的保护提供了必要的理论与支撑。

Dry-wet and chemical damages are important reasons that lead to the quickly weathering process of metamorphic sandstone carrying Helan mouth’s rock paintings following freeze-thaw and chemical damages. The research conducted 15,30,45,60,90,120,150 and 180 dry-wet cycles of rock paintings carrier in different solutions to explore the damage characteristics of rock paintings carrier under the combined action of dry-wet and chemical solutions. The results show that the mass,the longitudinal wave velocity,the uniaxial compressive strength and the stress-strain characteristics of the samples generally present gradual and differential attenuation as the number of dry-wet cycles increases,and the rate of change presents three stages with two obvious inflection points of 15 times and 60 times. SEM and XRD analysis tests were performed to qualitatively analyze the microstructure and composition of the samples,and the quantitative relation between damage variables and macroscopic test indicators was established based on the porosity. Finally,by analyzing the internal damage mechanism,it is found that the differential combination of hydrolysis,chemical corrosion,salt crystallization and dissolution result in the formation of the different number and connection of linear pores and pores in the rock due to different dry-wet conditions,which provides the necessary theory and support for the scientific protection of rock paintings.