砂岩质文物内部毛细水运移过程微电极响应特征

MICROELECTRODE RESPONSE CHARACTERISTICS OF CAPILLARY WATER MIGRATION IN SANDSTONE CULTURAL RELICS

盐结晶病害是砂岩质文物中最为常见的病害之一,可溶盐溶液在砂岩内部的毛细运移直接影响着文物保存的完整性。为了进一步了解不同因素影响下砂岩质文物内部中毛细水运移特征,以大足石刻砂岩材料为研究对象,自主设计了毛细吸水试验及微电极电阻率测试装置,定量分析孔隙结构、孔隙溶液、干湿循环及相对湿度对毛细运移和电阻率分布特征的影响。结果表明,松散的孔隙结构及较低的相对湿度对毛细运移有促进作用。毛细运移受可溶盐溶液表面张力影响明显,吸水量和运移速率随表面张力增加呈递增趋势。干湿循环作用导致内部孔隙扩张使毛细迁移速率加快,同时呈现出试样饱和度和砂岩电阻率的负相关性。可溶盐的存在极大降低了砂岩的电阻率,通过电阻率的时空分布特征,识别湿润锋的视电阻率范围与试样表层盐结晶劣化区域大致重合,整体趋势沿深度方向呈凹曲面变化。研究结果揭示了砂岩质文物内部毛细水运移规律,可为合理追踪盐害范围提供理论支撑。

Salt crystallization is one of the most common issues affecting sandstone cultural relics,directly impacting their integrity through the capillary migration of soluble salt solutions.To gain a deeper understanding of capillary water migration in sandstone relics under various influences,we designed independent capillary water absorption and microelectrode resistivity test devices based on the sandstones of Dazu Rock Carvings.We then conducted a quantitative analysis of the influence of pore structures,pore solutions,dry-wet cycles,and relative humidity on capillary water migration and electrical resistivity distribution characteristics.The results demonstrate that a loose microstructure and low relative humidity promote capillary water transport.Capillary migration is notably influenced by the surface tension of the soluble salt solution,with water absorption and migration rates increasing with surface tension.Dry-wet cycles lead to the expansion of internal pores,accelerating the capillary migration rate.Additionally,there is a negative correlation between the saturation of the sample and the resistivity of the sandstone.The presence of soluble salts significantly reduces the resistivity of the sandstone.The apparent resistivity of the wetting front of the sample approximately coincides with the salt crystallization deterioration area on the sample surface,revealing temporal and spatial distribution characteristics of resistivity.Moreover,the wetting front exhibits a concave trend along the depth direction.These results unveil the laws governing capillary water migration in sandstone relics,providing theoretical support for accurately tracking the range of salt damage.