Mogao Grottoes is a world heritage site at Dunhuang along the ancient Silk Road in northwest China, where exist 492 Buddhist caves containing a trove of gorgeous wall-paintings and statuaries. Because of the long-term deformation of cliff rockmass over thousands of years, cracks parallel to the cliff face cut through caves, resulting in large volume unstable rocks with a great threat to the caves' safety. During 1960s to 1980s retaining walls with large stones or reinforced concrete had been systematically built in front of the sloping faces of the grottoes to prevent the cliff rock from collapsing. The cliff rock above the retaining walls, on the other hand, underwent an intensive weathering due to the persistent exposure to the rainfall, cyclic wetting-drying and strong wind erosion. Loose sand and occasionally big stones fall down from the overhead slopes, possessed a new threat to the visitors to the caves. A combined technique for the abatement of deterioration of the cliff rocks is planed including local clearing of loose stone, anchoring of relaxed rockmass, and the consolidation of the weathered sediments on overhead slopes by grouting of potassium silicate. Engineering geological investigation results and engineering principles used for the stabilization and consolidation of Mogao Grottoes introduced in this paper may provide a successful prototype for the conservation of similar caves in western China.
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