STUDY ON THE WEATHERING CHARACTERISTICS OF THE YUMEN GLUTENITE IN THE MOGAO GROTTOES IN DUNHUANG

Weathering is one of the most important diseases in the surrounding rocks of Mogao Grottoes, which seriously affects the purpose for long-term preservation. To study the weathering characteristics of Yumen glutenite in Mogao Grottoes, a test point on the south side of Mogao Grottoes is selected. The method of step by step dissection is adopted and a series of experiments are conducted, such as X-Ray diffraction test, soluble salt test, field acoustic wave test and rebound test at different distances from the surface, which are 0、3、5、8 and 10cm. The results illustrate that the main salts involve Na₂SO₄、NaCl、CaSO₄, and the main minerals are quartz, feldspar, calcite, dolomite while clay mineral is chlorite; the mechanical strength reduced due to the influence of weathering, which is confirmed by the field acoustic wave test and rebound test. Both of the results rise with the increase of depth. By analyzing Meteorological data and the results, the main effects on weathering are determined and the mechanism of rock weathering is discussed. Weathering includes that (1) temperature stress causes damage on the rock mass structure and fracture. (2) the main mineral calcite in the cement is easy to convert into soluble Ca (HCO₃)₂, which could affect the cementation of rock mass structure. (3) salt weathering is another important rock weathering. Salts migrate and enrich with moisture migration and hydrate with water, which causes damage to the cohesion between different particles and result in the breakdown of rock mass.