敦煌莫高窟支撑体砾岩吸水规律实验研究

Experimental study on water absorption of the support conglomerate at Mogao Grottoes in Dunhuang

水是引起洞窟围岩风化并产生盐害最活跃的因素之一。针对敦煌莫高窟支撑体砾岩进行液态水吸附(接触吸附)实验和气态水吸附(非接触吸附)实验;对比分析砾岩在这2种吸水条件下的吸水特性及其影响因素,通过借助各影响因素与砾岩吸水率的数学模型,定量分析各因素对砾岩在液态水和气态水条件下吸水能力的影响。实验结果表明:(1)2种不同吸水条件下,随着时间的变化,砾岩的吸水特征及演变规律基本相同,其双对数吸水特征曲线都呈上凸模式,其中液态水条件下的平均吸水率是气态水条件下平均吸水率的14.9倍;(2)高岭石与液态和气态吸水条件下的吸水能力均呈负相关,并且在气态吸水条件下对饱和吸水率的影响性最大;伊利石与液态吸水条件下的吸水能力呈负相关,与气态吸水条件下的吸水能力呈正相关;(3)孔隙率与2种吸水条件下的吸水能力均呈正相关,且对液态吸水条件下的吸水能力影响最大。研究结果为敦煌莫高窟文物保护和盐害防治提供了科学依据。

Water is one of the most active factors causing the weathering of and salt damage to the surrounding rock of the cave. Experiments of liquid water adsorption（contact） and gaseous water adsorption（non-contact） on the support conglomerate of Mogao Grottoes at Dunhuang were carried out. The water absorption characteristics of and its influential factors to the conglomerate under two types of conditions were compared and analyzed. The influence of each factor on the water absorbing capacity of conglomerate under liquid and vaporous water conditions was quantitatively analyzed through the mathematical models of the water absorption rate of conglomerate under the different influential factors. The experimental results showed that,for two different conditions,the characteristics of water absorption of the conglomerate samely varied with the time. The double logarithmic curves of water absorption have an upward convex shape. The average water absorption of liquid water is 14.9 times higher than that of gaseous water. The influence of the kaolinite on the water absorption capacity has a negative correlation under the liquid and gaseous water conditions. Especially,the kaolinite has the greatest influence on the rate of saturated water absorption under the gaseous water absorption. The illite has a negative correlation with the water absorption capacity under the liquid water condition,but has a positive correlation under the gaseous water condition. The porosity has a positive correlation with the water absorption capacity under the liquid and vaporous water conditions,and has the greatest influence on the water absorption capacity under the liquid water condition.