Study Of Temporary Solidifying,extraction And Reversible Recovery Of Underwater Fragile Cultural Relics In Original State

Underwater cultural heritage is the precious physical witness of historical memory for cognition and exploration of the ocean,development and utilization of the ocean,prosperity and expansion of maritime trade,formation and development of diverse Marine Cultures.However,underwater cultural heritage,especially underwater fragile cultural relics,are in danger of being eroded by the surrounding environment.In order to prevent serious damage of underwater fragile cultural relics,it is a safe protection strategy to preserve them in a controlled environment for a long time after excavation.Extraction and transfer fragile cultural relics safely is an extremely important part of this strategy.However,due to the vulnerability of fragile cultural relics,the safety of underwater relics in the process of excavation,extraction and transfer is still facing huge challenges.The purpose of this study is to develop a class of temporary solidification materials for underwater fragile cultural relics,and to develop high-performance package reinforcement materials to ensure the safe extraction and transfer of cultural relics.In this study,the crystallization time,thermal stability,underwater reinforcement property,penetration depth,compressive strength of veratraldehyde were studied in detail.It is concluded that veratraldehyde has excellent underwater reinforcement properties for various underwater materials(wood,iron,ceramics and quartz sand),and the solidified veratraldehyde can be removed by using immersion method.In addition,adding a small amount of surfactant or attaching a layer of polypropylene fiber cloth can effectively solve the problem that the poor wettability of veratraldehyde on the surface of underwater cultural relics.The experimental results show that the liquid veratraldehyde can maintain the supercooled liquid state for a long time in a sealed container,which ensures the phase stability of the material during the process of transferring to the underwater sites.Under laboratory conditions,the technological process of the temporary solidification of underwater fragile cultural relics was simulated by using broken ceramic pieces and scattered beads without string as research objects.Fragile cultural relics are confronted the impact of water pressure,water flow and other uncertain physical factors during the process of extraction.In order to ensure the safety of cultural relics during extraction and transfer,it is particularly important to further package the veratraldehyde solidified system.Therefore,the properties and operation technology of carbon fiber/epoxy resin and modified polyurethane sponge/epoxy resin composites as underwater secondary encapsulation reinforcement layer were investigated in detail.The results show that the modified polyurethane sponge exhibit excellent super-hydrophobic/super–oleophilic properties.Compared with the complex laminated structure and fabrication process of carbon fiber/epoxy resin composites,the modified polyurethane sponge/epoxy resin composites can be directly used for underwater reinforcement in a simple single-layer structure without sealing.In addition,since the porous sponge can absorb a large amount of epoxy resin,the super-hydrophobic polyurethane sponge/epoxy resin composite can achieve the flexural strength of 3.56 MPa after curing under water.Finally,taking the underwater broken blue and white porcelain pot and fragile lacquer wood plate as research objects,underwater solidification,secondary package reinforcement and removal of each layer of reinforcement material after extraction from water were studied.The whole technological process of underwater fragile cultural relic undisturbed reinforcement,extraction and state restoration was investigated in detail.In conclusion,this study puts forward a new strategy of safe extraction and transfer fragile relics at underwater sites in original state,which makes up the gap of relevant materials and technologies,and provides a foundation for the subsequent restoration and preservation of underwater fragile relics.