Comprehensive Research Analysis On Weathering Of Yungang Grottoes

With over1500history, Yungang Grottoes were recognized as a world heritagesite. It has suffered the serious weather denudationg from the natural and man-madeharmful effects. Although Support vector machine (SVM) has been widely used invarious fields, the applied research about stone relics protection has not been reported.Make use of terahertz time-domain spectroscopy (THz-TDS) technology, we canattain the THz spectral data of Yungang Grottoes weathered stone, field ultrasoundtests in this region, and then the weathered degree of outer walls of Yungang Grottoeswere obtained by wave velocity ratio. Afterwards we integrated two groups of data asthe input feature vectors of forecasting model, and chose radial basis function as thekernel function of prediction model, and selected the optimal parameters used theLeave-One-Out Cross Validation（LOO-CV）method, finally established a model forpredicting weathered degree of stone relics based on spectral data and the SVM. Theaccuracy rates by using the prediction sample and the Leave-One-Out CrossValidation before promote the use of model. All the works in the dissertation aresummarized as follows:1. By using THz-TDS technology, the THz spectral characteristics of YungangGrottoes weathered stone have been studied. The experimental results showed thatdifferent grottoes weathered stone can be separated or identified on the basis of theirTHz transmission or refractive index spectroscopy. As a result, the spectral valuescorresponding to wave band with higher distinguish degrees can be extracted as theinput of training and testing samples to establish SVM prediction model.2. By using ultrasonic (US) detection technology, the ultrasonic wave velocity ofthe outer wall test area in Yungang Grottoes have been studied and the correspondingweathering level value obtained. And the weathering level values of all grottoes arechosen as the output of training and testing samples date to establish SVM predictionmodel.3. Using the THz spectroscopy and US experimental data of Yungang Grottoesweathered stone, the regression prediction model could be established according tothe basic principle and algorithm of SVM. We can analyze and predict the weatheringand damage degree of stone relics from the theoretical aspect. The results turn out thatthe SVM method has a strong capacity for processing spectral data. It can alsoidentify and predict weathering level as long as there are small differences in the samples, even if there are no characteristic peaks in the spectrum information.4. The further study of The Yungang Grottoes weathered stone using X-raydiffraction machine and scanning electron microscope (SEM) is not only apromising complement and auxiliary analyzing for THz spectroscopy and USdetection, but also an effective evidence to explain the reason of the weatheringdifference.5. Based on the summary of both domestic and foreign stone relics repairmethods, the repaired method of combine the optical material with eave for YungangGrottoes was proposed. The optical material can control light and then realize controlgrottoes’ temperature, and the protective eave can isolate rain and snow.