| Chongqing Danzishi Cliffside Figure were made by peasant rebellion army during the late Yuan Dynasty to the early Ming Dynasty on sandstone.It represents the sandstone Cliffside Figure in Chongqing and have more historical,cultural,artistic,religious or research value.Besides,Danzishi Cliffside figure was selected momentous relics throughout China in 2013.With the city development and weathering influence,the Ciffside Figure suffered various diseases and kinds of degree.This situation result in more challenge to protect and exhibit historic relics in the future.The protection of Danzishi Cliffside Figure was selected the demonstration project of Grotto weathering prevention in Chuanyu by National Cultural Heritage administration in 2016.The purpose is provide the experiences to protect other sandstone relics in similar environment.This study obtain weathering disease types and characteristic via accurate investigation in site.Besides,using Ground Penetrating Radar to survey the stratum and lithology.In order to assess weathering characteristic and degree,we conducted kinds of site tests including hardness,elastic wave velocity,drilling resistance and karsten tube.In other way,this research simulate drying and wetting cycle,acid rain or salt weathering and combine SEM or XRD to reveal the exfoliation mechanism of Danzishi Cliffside Figure.The main results are as follow:(1)Throughing the accurate investigation,the main weathering diseases include Mechanical fracture,surface granular disintegration,surface flake exfoliation,partial loss,crack,superficial fissure,cavernous weathering,smoking,and crack of cement repair.In addition,the diseases include surface chalking of sandstone,surface flake exfoliation,cavernous weathering and superficial fissure are resulted from weathering.Exfoliation distribute more widely and influence more serious.Because of the deference of environment,Wufo Cliffside Figure perform granular disintegration and Dafo Cliffside Figure suffered more surface flake exfoliation.(2)The results of hardness test reveal that the weathering degree of Wufo Cliffside Figure(259HLD)is more serious than Dafo(427HLD),this result was coincide to the result of elastic wave velocity.The result of drilling resistance and karsten tube are able to reflect sandstone weathering degree.Besides,the depth of surface rock mass weathering is about 4.7~10mm throughing drilling resistance.With the increase of sandstone depth,the structure of sandstone become more density and drilling resis-tance gradual stability.In a word,combine all results of index,the weathering degree of Wufo Cliffside Figure is more serious than Dafo Cliffside Figure.(3)The results of stratified spalling study,according to exfoliation from the inside out,the rock surface layer suffered weathering erode that become enhancing from the inside out,the roughness increased and hardness reduction(The hardness decree-sed from 258 HLD to 210HLD),the reduction of bluge layer is much bigger than exten tion layer,the most attenuation rates can reach 9.48%.In addition,particle decrease and pores increased,this future allowed medium of water to enter roock inside and permeation become more easyer and faster.Besides,Micromorphology is coincide to the result of karsten tube.(4)In orfer to study granular disintegration,we set up 3 experiments indoors,the conclusion include: Sodium sulphate have more influence than Calcium nitrate.During the experiments,the The quality changes dramatically and hardness or Elastic wave velocity performed reduced tendency.Besides,the simulation acid and drying and wetting cycle perform the granular disintegration.According to the result of SEM or XRD,the amount of quartz and dolomite increased,the feldspar has decreased,and the content of Illite increased,feldspar alteration is the important mechanism result in the weathering exfoliation on danzishi Cliffside figure. |
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