Weathering Characteristics of White Marble Relics Around the Hall of Supreme Harmony (Taihe Dian) in the Forbidden City

摘要

Fangshan Hanbaiyu is a typical white marble in China that was mainly used in high-grade royal buildings represented by the Forbidden City. Over centuries of natural erosion, most marble artifacts have undergone a variety of deterioration. Based on the deterioration investigation of a total of 726 balusters, 559 dragon heads, and 698 frieze panels around the Hall of Supreme Harmony (Taihe Dian), nondestructive testing technology, including portable x-ray fluorescence, colorimeter, and surface hardness tester, were also used to evaluate the weathering degree and analyze the relationship between the deterioration patterns and the type and spatial distribution of marble components. The results show that the temperature difference stress caused by solar radiation and the erosion caused by rainwater are the main reasons for the weathering. This explains why the components facing the South and East are more deteriorated. In addition, an evaluation method for stone relics deterioration based on three indicators (surface integrity, surface color, and surface hardness) of stone relics was established, and the health index of 12 typical marble components was calculated by this method, the values showed a good linear correlation with the field survey, which can provide a useful reference for subsequent investigation and assessment of the deterioration of the marble relics.