Study On Microstructure Of Weathered Sandstone And Conglomerate At Mogao Grottoes

A multi-scale study on microstructure of weathered sandstone and conglomerate at Mogao Grottoes was carried out based on a summary about the development and achievements in stone weathering research. In this thesis, the weathered conglomerate of Mogao cliff was divided in different test groups according to lithology and weathering degree. A series of tests were conducted, including physical and mechanics tests, rock thin section identification, X-ray diffraction, SEM and mercury injection test, so to understand the physical and mechanical properties, mineral composition, particle composition, pore characteristics and cement microstructure of weathered sandy conglomerate. In this way, the index that can be used to judge weathering intensity degree is preliminary determined. The following conclusions are otained.1) The particle composition is significantly different to various lithological rock samples, which led to the differences in porosity and microstructure properties. Resistance of sandstone and sandstone lens to weathering is lower than that of conglomerate. The weathering mechanism varies by lithologies, therefore lithologies should be considered as a discussion element in the conglomerate rock weathering studies at Mogao Grottoes.2) The conglomerate wearthering process at Mogao Grottoes can be divided into two phases. The first stage is cement weathering, the second stage is particle debris disintegration.3) Clay minerals in the cement and the micro-structural integrity of cement can be used as a conglomerate index to measure the rate of decay at Mogao Grottoes.4) In the weathering study of conglomerate, the results by means of observation with the naked eye and optical microscope change little with the degree of weathering. To determine diffrence of weathering degree in conglomerate, micro-scale research is needed, such as SEM and mercury injection test.