Weathering Principle and Conservation Treatment of the Cliff at Mogao Grottoes

摘要

The key conservation work of the Mogao Grottoes at Dunhuang falls into three aspects:consolidation of the rock,prevention and control of the sand and wind,and conservation of the wall paintings.As for the first aspect,the large-scaled stabilization project of the rock body started since 1960s has fundamentally got rid of the threats to the caves caused by the rock deformation.However,the long-term strong wind-sand erosion and the extreme variations of temperature have resulted in intensive weathering of the cliff,which causes the falling down of rocks and endangers the increasing visitors to the caves.When the top rock layer above the caves becomes thinner and thinner because of wind erosion,water penetration would become possible and damage the cultural relics inside such as wall paintings and sculptures.Through detailed investigation of the conservation conditions of the rock at the Mogao Grottoes,this paper comes to the following conclusions:the main cliff weathering deteriorations are physical ones,and the main factors resulting in rock weathering are the variations of temperature and relative humidity,precipitation and wind;The main deteriorations of the rock body are collapsing,falling,sand erosion and salt efflorescence,and the weathering intensity varies with the landforms,resulting different weathering deteriorations;the essential conservation of the rock body at the Mogao Grottoes is to improve the stabilization of the caves and the slopes,and cut off the hydrosphere channel into the caves,keep the cave isolated and maintain its present condition;A series of successful engineering treatments,such as the PS stabilization,crack grouting,anchor consolidation,thin top layer treatment and local removing can effectively prevent the weathering deteriorations of the rock at the Mogao Grottoes.