STUDY ON WEATHERING CHARACTERISTICS OF ROCK MASS ALONG DEPTH DIRECTION OF CLIFF LOCATED AT NORTH OF DUNHUANG MOGAO GROTTOES

The increasingly severe weathering erosion affects the stability of surrounding rocks and the preserving environment of wall paintings, which has become a great threat to the security of the grotto relics. A cliff located at the north of the Mogao grottoes is selected as the research site. The method of gradual dissection is adopted, and samples are numbered in sequence along the horizontal direction from the surface. A series of experiments are conducted and include size distribution test, field acoustic wave test, soluble salt test and X-Ray diffraction test. The results illustrate that the grain composition of the cliff have an effect on weather resistance. The curve of wave velocity fluctuates along the excavation depth. The content of sodium feldspar decreases within depth of 0.7 m as Quartz increases. As one of the main contribution to weathering of rock mass, soluble salts accumulate within the depth ranging from 0.4 m to 1.0 m. By comprehensive analysis on experimental results, depths in 1.0 m, 0.6 m and 0.4 m are respectively regarded as the weathering depths of No.1, No.2 and No.3 horizontal testing caves. As for the variation among cliff space, the heaviest weathering happening at upper part and weakest weathering lies at lower part.