Controls Of Water Movement And Transform In Yungang Grottoes,Datong,China

Flooding and the threat of differentiation has become an important issue of stone artifacts. Yungang Grottoes Stated at south cliff of wuzhou mountain,west of Datong . The Grottoes was dugged in sandstone. The weathering damage of stone caving in face of continued increase. The most directed and fundamental fator of stone weathering is the water from everywhere. The way of solution the caving weathering is detected out the channel of water came into caves. By investigating. we find out the controlling factors of water sources, which provide a scientific basis for caves protection.The water sources of Yungang Grottoes mainly contain direct seepage from cave top or wall, perched water from mudstone of cave wall, condensation of air.The main factors affected rainfall seepage to grottoes are thickness of silt, fractured and so on. Permeability of silt is far below to the sand and gravel. in addition, the water storage capacity of silt is more high. The survey of silt infiltration illustrate that don't every part of rainfall can infiltration to the top of bedrock, only the thin area of silt can. Weather the water enter to the caves related to the development of cracks. The average infiltration of sandstone was minimal, the excretion of precipitation are runoff and evapotranspiration.The quantity of perched water is related the size and distribution of mudstone, and also related with the infiltration of precipitation. North-South profile shows that mudstone in contact with the cave is easy to form perched water and discharge to the cave.The main factors of control condensation generated are air temperature, ground temperature, air humidity, wind speed, and so on. The wind speed of Yun Gang grottoes is low throughout the year, so the main factor of condensation generate is the difference between air temperature and ground temperature, air humidity. In summer, the difference between air temperature and ground temperature is small, the humidity of air is high, so easy to generate condensation. The quantity of water condensation on the cliffs and rock is closely related to the degree of weathering, a high weathering rock, owing to the porosity of weathering sandstone are more, so than the condense surfaces is more big than the fresh rock .combined with that rock internal temperature is low than surface temperature, so the weathered rock condensate more condensation than the fresh rock .