| The Fengguosi in Yi County,Liaoning Province was built in 1020 AD,a thousand years ago,as a royal monastery by Emperor Shengzong in memory of his mother,Empress Dowager Xiao.The Main Hall of the Fengguosi is one of the three surviving Liao Dynasty buildings in China.The Fengguosi was declared by the State Council of the People’s Republic of China as one of the first batch of state priority protected sites in 1961.In 2013,the Main Hall along with the Wooden Pagoda of Ying County as wooden structures of Liao Dynasty entered into the tentative list for UNESCO World Heritage Site consideration.Inside the Main Hall,there are seven painted sculptures of Buddha(all above 9 m in height),known as the "Seven Buddhas of the Past".This form and the scale are very rare in Buddhist temples.On the two sides of each Buddha,there are two painted sculptures of Bodhisattvas(2.5 m-2.7 m in height),two painted sculptures of Heavenly Kings(3.5 m in height)on both sides of the Main Hall,and an inverted painted sculpture of Guanyin(2.8 m in height)behind the main Buddha statue,making a total of 24 painted sculptures.The wooden structure of the Main Hall of the Fengguosi and the exquisite painted sculptures inside the hall have preserved the style and cultural characteristics of the Liao Dynasty and conveyed valuable scientific information and artistic values.Fengguosi went through 34 times of different degrees of maintenance and additions from the Liao,Jin,Yuan,Ming and Qing Dynasties to date,including seven repairs involved in the Main Hall of painted sculptures.Among them,the Kangxi 45 years(1706)is the ancient history of the last comprehensive maintenance of the painted sculptures.In May 1958,Jinzhou City Cultural Heritage Bureau organized local craftsmen to repair the lotus-seats,the Bodhisattvas and the Kings of Heaven statue locally.It hasn’t been repaired since then.The current state of the painted sculptures presents the impact of these two maintenance.Through the disease survey,we found that because of long years out of repair,the painted sculptures developed many kinds of diseases.So it needs to be restored in a timely manner.During the literature research,it was found that there was a lack of original data and information of the painted sculpture of the Main Hall of Fengguosi.Therefore,non-destructive testing and internal structure measurement could obtain the basic data of the body of the painted sculpture,enhance the completeness of the original information of Fengguosi,and provide strong support for its application for World Cultural Heritage.The thesis takes the painted sculptures in the Main Hall of the Fengguosi as the research object.The aim is to study the restoration material of the cracks in the base layer on the painted sculptures.Based on plentiful research of historical documents,the characteristics of the materials of making painted sculptures and the development process of craftsmanship of the painted sculptures on the main historical dynasties of China were analyzed in detail.Also,the importance and particularity of the painted sculptures in the Fengguosi as the remains of the Liao Dynasty were pointed out.Through on-site disease investigation and data statistical analysis of diseases,the main types of diseases of the painted sculptures of the Fengguosi were clarified,and the location and the causes of the crack diseases were analyzed.Through basic geotechnical tests,scanning electron microscopy,X-ray diffraction,chemical analysis,and salt content analysis,the basic properties of the soil of the painted sculpture layer were tested and compared with the local colluvial soil and residual soil taken from Yi County.It was basically determined that the source of the material of the base layer was the local residual soil.By means of non-destructive tests such as wave velocity test,water content test,three-dimensional laser scan,endoscopic observation and X-ray detection,the internal wooden skeleton structure of the painted sculpture was revealed basically.Simultaneously,the production process of the painted sculpture in the Fengguosi was clarified.Aiming at the crack disease,we selected soil + hemp,supplemented with quartz powder to enhance the strength and weathering resistance of the base layer as the restoration materials,which is the closest to the nature of the original fine base layer.The most suitable material ratio for repairing was selected by considering the suitability of mass loss rate,volume change rate,wave speed and unconfined compressive strength.The main research contents and results are as follows:(1)The differences and characteristics of the production materials and craftsmanship were determined by comparing and analyzing the typical painted sculptures of different Chinese historical dynasties.The development of Chinese painted sculpture production techniques was ordered.The value and particularity of the painted sculpture in the Fengguosi as Liao Dynasty remains in history were revealed.At the same time,a disease survey of the painted sculptures found that crack disease is the main disease of the base layer of the painted sculptures.The crack disease was classified according to the causes,and repairing the cracks in the base layer was found to be necessary and urgent.The earliest Chinese painted sculptures can be traced back to the Red Mountain Culture of the Neolithic Age.At that time,the sculptures were still relatively primitive,such as pottery sculptures.Whereas some color painting had already started to appear on the surface of these pottery sculptures.Due to the introduction of Buddhism and the construction of cave temples,a large number of exquisite painted sculptures were created.Tang Dynasty was the heyday of the development of painted sculptures.The images of painted sculptures in this period were majestic and extraordinary.Ancient artisans hung the grass mat woven with reed stems on the wooden skeleton of the painted sculpture,which was more conducive to hanging mud.In Song Dynasty,the painted sculptures were handsome and realistic.The base layer was thinner and more delicate than other dynasties.Liao Dynasty was in the same historical period as Song Dynasty,but the production techniques and artistic styles is full of characters.The painted sculptures of Liao Dynasty are more voluminous,and the ornaments on the sculptures are gorgeous and rich,incorporating the characteristics of the Khitan nation.The painted sculptures of Yuan Dynasty focused more on the image and emotion of the figure.The craftsmen used hemp paper instead of plaster,which was more conducive to stopping and covering the expansion of cracks.Although Ming and Qing Dynasties imitated the Tang Dynasty in artistic style,the charm and manner were weakened.Some painted sculptures even eliminated the fine clay layer in the base layer,and the production process tended to be simplistic.The painted sculptures of the Fengguosi chose to give up binding straw on the wooden skeleton in the production process,while the sculptures still stand for a thousand years.Therefore,it is very meaningful and valuable to study the materials,structure,and restoration materials of the sculptures.There are many kinds of diseases,such as cracks,craquelure,flaking,color alteration,surface dust,etc.Among them,the cracks of the base layer are more seriously developed,so it is necessary to study the repair materials for the cracks of the base layer from the perspective of geological engineering.(2)The material property of the base layer of the painted sculpture in the Fengguosi was characterized through a series of test and analysis.The originality of the materials used for the base layer of the painted sculpture was clarified by analyzing the similarity with local soil samples from Yi County,which provides implications to the later restoration work.Generally speaking,when the ancients begin to construct temples,painted murals,and painted sculptures,they usually obtain materials from local sources.Local materials are often more suitable for local climate.Also,local materials can meet the needs of daily repair with low transportation cost.We took samples from broken part of original base layer,the colluvial soil,residual soil,and bed rock from Yi County.Through basic physical property tests,scanning electron microscope observation,X-ray diffraction mineral composition analysis,chemical composition analysis,and salt content analysis,it was finally determined that the soil used for the base layer of the Fengguosi painted sculpture came from the local residual soil of Yi County.This provided a theoretical basis for the subsequent restoration of the sculptures using local residual soil.(3)The internal structure of the wooden skeleton of the painted sculpture in Fengguosi was identified by means of multiple nondestructive testing.The preservation state of the wooden skeleton of the painted sculpture,the connection mode between the wooden skeleton and the fitting state between the wooden skeleton and the base layer were determined.Conclusively,the production process of the painted sculpture in the Liao Dynasty was represented.Furthermore,this research enriched the records of the internal wooden skeleton structure of the painted sculpture in the Fengguosi in historical documents.Ancient Chinese painted sculptures can be divided into clay sculptures,wood-bone clay sculptures,wood-carved clay sculptures,stone clay sculptures,pottery sculptures,etc.Depending on the production process,the painted sculptures in the Fengguosi belong to the wood-bone clay sculptures typically.Since the structure and profile of cultural relics need to be identified in advance when repairing,and there is little documentation of the production process of the painted sculptures of the Fengguosi in history,it is particularly important to restore the internal structure and production process through nondestructive testing.On account of the large size of the painted sculptures,and the original structure of the cultural relic cannot be damaged,a combination of actual and speculative measurements was used to explore the internal structure of the painted sculptures.We used 3D laser scanning to determine the shape parameters of the painted sculptures.We analyzed the layered structure of the base layer,the internal wooden skeleton building system,and historical restoration traces with the help of X-ray detection and endoscopy.The research word reproduced the production process of the painted sculptures in the Fengguosi and enriched the data records.The research basically restored the production process of the painted sculptures in the Fengguosi and improved the data records of the wooden structure.Studying the wooden skeleton structure is to clarify the internal preservation status of the painted sculptures and indicate the relationship between the base layer and the wooden skeleton.(4)Two types of materials including hemp and quartz powder have been added into the residual soil of Yi County with different mixture ratios and these samples were cured in an environment by referring to real summer and winter climates in Yi County.The most suitable material proportion for the repair of the cracks in the base layer of the painted sculpture of the Fengguosi was determined by analyzing the comprehensive performance of the restoration materials of different formulations in terms of shrinkage resistance and unconfined compressive strength.The screening method of the material for the repair of cracks in the base layer can also be potentially used for repairing same type of painted sculpture.We chose two environmental conditions,summer and winter.Different temperature and humidity were set according to the local climate characteristics of Yi County.The specimens with different ratios of the base layer were placed in a constant temperature and humidity chamber,and the changes of parameters in the process of water loss of the base layer specimens were measured.Based on disease investigation,the cracks of the base layer mainly include tension damage formed by shrinkage and extrusion deformation formed by misalignment of internal wooden skeleton.Therefore,four indicators,namely mass loss rate,volume change rate,wave velocity and unconfined compressive strength,were used as important parameters to measure pros and cons of the repair material.The overall performance of different ratios of base layers was considered in terms of shrinkage resistance and unconfined compressive strength.Finally,the residual soil of Yi County with 0.75% hemp fiber and 20% quartz powder was selected as the restoration material for the base layer of the Fengguosi.At the same time,the same method and process could be used for the screening of restoration materials for cracks in the same type of painted sculpture.This thesis identifies the unique status of the painted sculpture in the Fengguosi in the development of Chinese painted sculptures.We investigated the diseases of the painted sculpture,analyzed the material source of the original base layer,represented the structure of the internal wooden skeleton,and comprehensively evaluated the materials and formulas suitable for repairing the cracks.The innovation of this thesis lies in the nondestructive inspection of the large-scale painted sculpture of Liao Dynasty by X-ray detection,which reveals the internal wooden skeleton building system and the disease developed inside the base layer.By considering the four dimensions of material source,similarity to the nature of the original base layer,shrinkage resistance and unconfined compressive strength,we developed the most suitable restoration material for the base layer of the painted sculptures in the Fengguosi.Also,we established a set of screening methods and processes for restoration of cracks in the same type of the base layer of painted sculptures. |
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