水岩作用对沈府君阙表层剥落影响机制分析

Influence mechanism of water-rock interaction to scaling off on Shenfujunque

水的长期作用是南方地区露天砂岩石质文物表层劣化的主因。该文以沈府君阙表层剥落为对象,通过病害特征和赋存水环境调查,结合新鲜岩样与表层剥落岩样微观结构、矿物成分、易溶盐等指标的对比分析,探讨了阙体水岩作用方式时空特征和表层剥落形成机制。结果表明,表层剥落表现为壳状、片状和粉状,分布具有空间伴生性和时间连续性,该病害主要由阙体岩石表层在水或水汽运移直接驱动下发生成分改变和在含水率变化间接参与下产生结构破坏共同导致。各种剥落形式的区别在于岩石表层破坏方式不同,壳状剥落为表层内外两侧结构差异性破坏,片状和粉状剥落为表层结构密实度破坏,粉状剥落破坏程度更严重,主要体现在盐风化方面。根据阙体岩石表层劣化进程不同,阙身下部和阙楼表层剥落可分别概化为“阶段性”和“渐进性”2种模式。

Shenfujunque,located in Dazhou,Sichuan Province of China,is a stone ancient building,and because of its great value,it has been honored as the key national protected site.Long term effects of water in south China is the main reason leading to degradation of sandstone heritage outdoor.This research selects scaling off on Shenfujunque as the survey object.By field investigation,the characteristic of scaling off and water surrounding were determined,combined with the indexes including micro structure,mineral composition and soluble salt from both fresh stone sample and scaling off sample,the authors explore the time and space characteristic of water-rock interaction and the developing mechanism of scaling off.The result shows as follow:scaling off in Shenfujunque presents as crust,slice and power,the three forms distribute associated in the space,while they develop continually.The main reason result in scaling off is the surface stone has been structurally damaged by water(both liquid form or vapor state)and composition change.The difference between three scaling off forms may lie in the different destruction styles on sandstone surface.Crust scaling off present structure otherness destruct on the both sides of surface stone.Slice and powder scaling off both result from the stone surface destroyed,powder scaling off is more serious,especially in soluble salt weathering area.According to the different degradation process of surface stone,scaling off located at the lower part and the middle-upper part can be generalized as two modes,one is"periodic mode",and the other is"gradual mode".