敦煌莫高窟围岩吸水特性及其影响因素分析

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

为了研究敦煌莫高窟典型围岩吸水特性及其关键影响因素,本文利用自主研发的岩石水理作用智能测试系统,对从敦煌莫高窟采集的3种不同岩性的岩石样品进行了无水压条件下的液态水吸附实验。依据吸水实验获得的3种围岩样品吸水随时间动态变化曲线,分析比较了不同种类岩石样品的吸水特性,建立了其吸水过程函数。同时,通过X射线衍射实验、电子显微镜扫描实验和压汞实验,分别获得了岩石样品的矿物成分及含量,微观孔隙结构特征和孔隙率等重要物理性质参数,综合分析讨论了黏土矿物及微观孔隙结构这两大重要因素对莫高窟3种典型岩石样品吸水特性的影响。研究结果表明,莫高窟3种围岩样品吸水动态变化的总体趋势有相似性,均表现为减速吸水过程,并可以用负指数函数进行拟合。3种岩样吸水能力差异显著,按大小排序依次为:黑砂岩>泥岩>粉砂岩。对于此次研究的3种不同岩性的莫高窟围岩样品而言,黏土矿物(主要是伊利石)的含量不是制约其吸水性的主要因素,决定其吸水量大小、吸水速率快慢的主要因素是岩石样品的微观孔隙结构特征尤其是孔隙率的大小。

Water absorption experiments are carried out on three different types of surrounding rocks collected from Mogao Grottoes at Dunhuang. It uses a selfdeveloped 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 ofthe 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 sandstonemudstonesiltstone. 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.