广汉龙居寺中殿墙体壁画载体结构安全调查研究

Study on Structural Safety of Walls as Mural Carrier in the Central Hall of Longju Temple, Guanghan

广汉龙居寺中殿墙体壁画载体为编竹夹泥墙结构,存在明显的结构安全问题。为了解壁画载体结构安全现状,综合采用现状调查、三维扫描、X射线成像、探孔探查等原位无损或微损方法,对墙体结构安全问题种类及特点、外部形态特征、内部结构缺陷和材料劣化等进行了调查,分析了结构安全问题的成因。结果表明:壁画载体存在墙面变形起鼓、墙体周围缝隙和墙体表层裂隙三类问题,其中内侧墙面变形起鼓对壁画保存构成严重威胁。墙体两侧泥层和中间骨架之间连接较弱且存在大量不密实区等结构缺陷,骨架竹木材料因白蚁危害劣化严重。壁画载体结构安全问题主要受控于墙体两侧泥层结构变形,与两侧泥层和中间骨架之间结构缺陷、中间骨架材料严重劣化两方面密切相关。此研究为该壁画载体结构安全问题的处理提供了依据,对于四川地区同类古代建筑壁画载体结构安全调查具有参考价值。

In Sichuan there are more than ten extant ancient buildings of Ming dynasty which are decorated with murals. Most of the murals were painted on walls of the daub and bamboo lattice structure, and so are the murals in the Central Hall of Longju Temple in Guanghan. As the carrier of murals, the walls of the Central Hall have obvious structural safety issues. Comprehensive methods were adopted to identify the problems and to assess the exterior morphological characteristics as well as the interior structural defects and degradation of materials, including investigation on the status quo, 3-D scanning, X ray imaging and prospect hole probing, which are non-destructive or only cause micro damages. The results indicate that the major structural safety issues include deformation and bulge of the wall surface, cracks surrounding the walls and superficial crevices, amongst which the bulge of the inner side of walls poses most severe threat to the murals. The connection between the daub layers and the bamboo skeleton in between is weak and there are lots of loose areas, while termites cause serious degradation of bamboo and wooden components. The structural safety issues are mainly caused by deformation and contraction of the daub layers, and are closely correlated to the structural defects between the layers and the deterioration of materials in central layer of bamboo lattice. The results of the study provide theoretical basis and guidance for handling structural safety issues of mural carriers, and are also of reference value for the structural safety investigation on similar mural carriers of ancient buildings in Sichuan.