Yi Wuzhi and Lang Xiangui
The maijishan grottoes, located 45 km southeast of
Tianshui, Gansu Province, is one of the most famous grotto sites in China. Dating from about 400 c. e., the site consists of 194 caves housing more than 7,800 sculptural objects and 1,000 m2 of wall paintings. From late 1975 to early 1994, a joint project for the restoration and consolidation of these fragile grottoes was undertaken (see acknowledgments). Four different techniques were tested and applied at the site: rock bolting, grouting, structural support, and spraying of concrete on the rock surface to prevent weathering.
Geology, Geomorphology, and Deterioration of the Maijishan Grottoes
Technical Research on Stabilization of the Grottoes
Shaped like a haystack, Maijishan mountain is 142 m high (Figs. 1, 2).
The east, west, and south sides are barren and steep with a slope of 95°. The bedrock is exposed and the lower part of the cliff has talus deposits. The Maijishan stratum, of Upper Tertiary period, is a purplish and brick-red conglomerate interspersed with thin layers of sandstone and mudstone loosely cemented by fine red clay containing calcium and iron (Huang 1976).
The severe, extensive deterioration of the Maijishan caves is the result of weathering, cracks caused by stress relief, and seismic activity. Various types of damage include cracking, collapse, flaking, and spalling due to moisture seepage, and repeated excavation of grottoes, all of which have left the cliff surface with many weathered, overhanging rocks (State Cultural Relics Museum 1964).
Based on the initial condition survey of the caves, the stabilization plan for the Maijishan grottoes was initiated in 1960. Various organizations, including the State Cultural Relics and Museum Institute, recommended reinforcement of the grottoes as the only way to preserve these cultural treasures. In 1974, after several years of extensive investigation, the Gansu Provincial Construction Survey and Design Bureau proposed the use of steel rock bolts and concrete retaining walls to reinforce the cliff on the
Figure 1
Maijishan grottoes after the 1984 stabilization.
Figure 2
An early view of the Maijishan grottoes.
West side and the use of steel-and-concrete frame structures to support the roof (Gansu Construction Survey 1975).
At the end of 1975, the authors conducted preliminary field testing of a rock bolting technique using steel and concrete grouting. The success of these trials demonstrated the possibility of designing a strategy employing new methods (Yi and Lang 1979). By the end of 1983, the team completed research, design, and application of the four techniques detailed below: sprayed concrete, rock bolting, grouting, and structural support.
World History
