Surface Weathering Characteristics And Mechanism Study Of The Xiao Fo Wan Statues Dazu Rock Carving

The XiaoFoWan Statues in Mountain Baoding,as an importat part of the World Cultural Heritage,have formed a serious weathering phenomena in the last 800 years.The Conservation and Restoration Project of the XiaoFoWan Statues was listed in the Sichuan-Chongqing Grottoes Conservation Demonstration Project by the State Administration of Cultural Heritage in April 2016,which could offer a reference and demonstration for that of other similar types historic stone conservation.Based on field disease investigation and field test,the study has researched the current preservation status and weathering characteristics of the XiaoFo Statues,and also researched the weathering mechanism of the surface rock mass of the XiaoFoWan Statues by SEM,XRD and indoor weathering simulation.The main conclusions of this study are as below.(1)According to the field disease investigation,the XiaoFoWan Statues have produced stone broken flake,cranny,pulverization,exfoliate,empty drum,water damage,salting out,smoked,biological disease,of which the most serious weathering disease is exfoliation,which also reflects the differences in disease types and forms between indoor and outdoor cultural relics.(2)The surface value hardness of the material points has slightly differences under different environmental conditions,which is parted from small to large as indoor layer,outdoor environment and indoor second floor per the location of the material point in the drilling resistance tests zone.The weathering layer thickness of sandstone strip is between 1~5mm,but the stability of the drilling resistance is basically same,and the outdoor weathering sites are more severe than indoor cultural relics.(3)By the measured results of XRD and SEM of weathered sandstone and fresh sandstone samples in the XiaoFoWan Statues,the study reveals that he main mineral composition of the pluton at XiaoFoWan Statues is quartz,feldspar,calcite and clay minerals,and the differences between the weathering fall on loose microstructure,which make the calcareous cementation loss and the secondary mineral generates with the content decrease of kaolinite and gypsum and feldspar minerals at the same time.(4)Single influence factor simulation weathering test how that,the influence of sandstone weathering in the XiaoFoWan statues can be listed as acid rain corrosion,freeze-thaw cycle and dry-wet cycle in descending order among the three single factors.And the dry-wet cycle damages the well bedded developed sandstones most severely;the weathering detected in the freeze-thaw cycle tests is much obvious in the rock mass,and the weathering of the frozen thawing samples more significant than that of the dry frozen thawing samples;the acid rain corrosion has a greatest influence on the surface properties of the samples,and the damage of the sandstone samples is also enhanced with the increase of acid.(5)The weathering of the XiaoFoWan Statues is the result of the internal and external interaction,and whose material composition and microstructure provide the material basis for weathering,and the external environmental factors provide the motivation for the weathering.