可溶盐溶结循环对清水墙结构的风化影响

Weathering Effect of Melt-crystallization Cycle of Soluble Salt on DryWall

外界环境干湿交替变化形成的可溶盐溶结循环是导致中国南方清水墙结构风化的重要因素,截止目前尚缺乏系统化的有限元软件可以模拟这一风化程度。为了深入研究可溶盐溶结循环对南方清水墙结构的影响规律,对比分析了水冻融循环与饱和可溶盐溶结循环的作用特点与数学模型,并通过线性关系将二者联系起来。基于此分析,采用发展较为成熟的冻融循环“温度-应变耦合”模型来近似模拟可溶盐溶结循环过程,以期深化研究可溶盐溶结循环对清水墙结构的风化影响。结果显示,水冻融循环中的环境温度因子与可溶盐溶结循环中的环境湿度因子具有明显的线性关系,且该关系受孔隙比、环境湿度、可溶盐溶解度、线膨胀系数等因素的影响;随着可溶盐溶结循环次数上升,清水墙外侧逐渐向外位移膨胀,且墙体中部的水平位移(5.8 mm)略大于顶部的水平位移(5.4 mm);墙体膨胀现象由清水墙外侧向墙体内部逐步延伸,且最终趋于稳定;同时墙体外侧的风化程度远大于墙体内部的风化程度,上述成果可用于指导清水墙工程的修缮施工。

The melt-crystallization cycle,which is caused by the alternating dry and wet external environment,is an important factor leading to the weathering of dry wall structures in southern China.Up to now,there is no systematic finite element method(FEM)to calculate their weathering degree.In order to study the influence pattern of the melt-crystallization cycle of soluble salt on the structure of the southern dry wall,the characteristics and mathematical model of the water freeze-thaw cycle and saturated soluble salt melt-crystallization cycle were compared and analyzed.The two cycles were assumed to be of a linear relationship.In order to promote the study of the influence of the soluble salt melt-crystallization cycle on the weathering of dry wall structures,the temperature-strain coupling model,according to our analysis,is well developed.The results show that the temperature factor in the freeze-thaw cycle and the humidity factor in the soluble salt melt-crystallization cycle have an obvious linear relationship.The relationship is affected by porosity ratio,critical moisture content,salt solubility,and linear expansion coefficient.As melt-crystallization cycles increase,the outer free surface of the wall gradually moves outward and expands,and the horizontal displacement in the middle of the wall(5.8 mm)is slightly larger than the horizontal displacement in the top(5.4 mm).The wall expansion gradually extends from the free surface to the inside of the wall,and gradually stabilizes.Besides,the weathering degree of the outer surface is much greater than that of the inside.The results above can be used to be a reference for the repair and renovation of dry wall structures.