Compared with the previous reinforcement method of retaining pillars, the new techniques of concrete spraying, rock bolting, grouting, and structural support used at the Maijishan grottoes demonstrated a range of valuable characteristics, as follows:
1. Thinness: The retaining pillars, which are about 0.5-10 m thick, were reinforced by spraying concrete and rock bolting. When steel bolts 3-15 m long were used to anchor the fractured rocks, a concrete coating with a thickness of only 50-150 mm was needed.
2. Firmness: Steel bolts 3-15 m in length used to strengthen the cliff face effectively increased the internal strength of the rocks. These rods function like ribs in a body.
3. Depth: Steel rods anchored deep into bedrock remarkably increased the cohesion and stability of the rock.
4. Adaptability: In addition to strengthening, these techniques can also be applied to the restoration of the site (collapsed bedrock, corridors, and eaves).
5. Speed: High-speed, high-efficiency electric machines were used to carry out drilling, grouting, and spraying.
6. Economy: Much less material was needed for this design when compared to that of the construction of a typical retaining pillar.
7. Aesthetics: An appropriate amount of red clay was added to the concrete coating to match the original surface color. Thus, steel rods anchored into the rocks do not affect the appearance of the grottoes or the cliff face.
Conclusions
Acknowledgments
In a 1984 evaluation, conservation experts and scholars stated, “Loosely cemented conglomerate, the steep slope, and the huge rocks hanging inside the caves have made the consolidation of the Maijishan grottoes a difficult and dangerous operation” (Yi and Lang 1984).
The present comprehensive approach to the consolidation of the Maijishan grottoes—concrete spraying, grouting, rock bolting, and construction of a structural support—all without substantially changing the appearance of the caves, has opened a new avenue for the conservation of grotto sites (Figs. 4, 5). This is an outstanding example of how advanced technology can be applied in the protection of threatened cultural heritage.
The research, design, and implementation of this project were carried out under the guidance of the State Bureau of Cultural Relics, the State Cultural Relics Museum and Research Institute, and the Gansu Provincial Culture Department from the end of 1975 to the beginning of 1994. This is a joint effort among specialists from the Gansu Provincial Architecture Institute; the Gansu Construction Survey and Design Institute; the Fifth Construction Engineering Company; and the Maijishan Consolidation Office, a temporary office in charge of project design and supervision. The authors would like to take this opportunity to express their sincere gratitude to the leading officers, experts, and all the engineering crew members who assisted in this project.
Figure 4
An early view of Maijishan Grotto 15 to the fifth section.
Figure 5
Grotto 15 to the fifth section after stabilization.
References
Gansu Construction Survey and Design Institute
1975 The Preliminary Design for the Repair and Stabilization of the Maijishan Grottoes (in
Chinese). Lanzhou: Gansu Construction Survey and Design Institute.
Huang Yuding
1976 Report on the Geological Survey for the Maijishan Stabilization Project (December) (in Chinese). Xian: Shanxi Prospecting Institute.
Li Zuixiong and Yi Wuzhi
1983 Feasibility Study on the Application of CPS Inorganic Compound to Grout the Crevices in the Maijishan Conglomerate (in Chinese). Lanzhou: Gansu Museum and the Gansu Architectural Research Institute.
State Cultural Relics Museum and Research Institute 1964 Survey Report on Maijishan Grottoes (July) (in Chinese). Xian: State Cultural Relics
Museum and Research Institute.
Yi Wuzhi
1984 The Techniques of the Spraying, Grouting, Rock-Bolting and Supporting Techniques for the Stabilization of Maijishan Grottoes (April) (in Chinese). Tenshui: Maijishan Stabilization Office, with the assistance of the Gansu Survey and Design Institute, the Gansu Fifth Construction Company, and the Gansu Architectural Research Institute.
Yi Wuzhi and Lang Xiangui
1979 Research and Experiments on Spraying Concrete and Rock-Bolting Stabilization Techniques (April) (in Chinese). Lanzhou: Gansu Architectural Research Institute.
Research and Experiments on Spraying, Grouting, Rock-Bolting and Supporting Stabilization Techniques (April) (in Chinese). Lanzhou: Gansu Architectural Research Institute.
World History
