WATER ABSORPTION OF SURROUNDING ROCKS OF MOGAO GROTTOES AT DUNHUANG AND ITS INFLUENCING FACTORS

Water absorption experiments are carried out on three different types of surrounding rocks collected from Mogao Grottoes at Dunhuang. It uses a self-developed intelligent water absorption equipment. Its objective is to investigate their water absorption characteristics and underlying key influencing factors. The water absorption characteristics of the three types of rocks are analyzed and compared based on their water absorption curves obtained from the water absorption experiments. Meanwhile, the mineral components, microstructure features and pore structure parameters are determined by multiple means of X-ray diffraction, scanning electron microscopy and mercury intrusion porosimetry. Finally, the effects of clay minerals and micropore structure on water absorption of the investigated three typical rocks from Mogao Grottoes are comprehensively discussed. Results show that the patterns of the water absorption curves of the three types of rocks are very similar and all characterized by a similar kind of dynamic process with decreasing water absorption rate that can be well fitted by a negative exponential function. However, significant differences are found in water absorption ability among the three types of rock samples which can be sorted in an order of black sandstone > mudstone > siltstone. Finally, it concludes that for the three different types of rock samples investigated in this study, the content of clay minerals (mainly illite) is not the main factor restricting its water absorption, whereas the key factor determining the water-absorption capacity and rate is the pore structure especially porosity.