敦煌莫高窟洞窟围岩渗透特性研究

敦煌莫高窟壁画受自身材质和自然环境等的影响,已经保存了1000多年的壁画产生起甲、酥碱、空鼓、壁画大面积脱落等多种病害。多项研究已经证明,这些病害主要是由于水盐运移导致的,水汽在岩体内的运移促使盐分在壁画表面富集是造成石窟病害主要原因之一。通过石窟围岩的渗透性研究可以解释水汽运移的规律,研究壁画病害形成的机制。在研究中应用原位定水位渗透试验测得了莫高窟洞窟围岩不同地层岩组的渗透系数,并通过高密度电阻率法监测原位渗透试验、X射线CT计算岩石孔隙比等多种方法和手段研究莫高窟围岩的渗透性,认为敦煌莫高窟围岩不同地层具有不同的渗透性,因此,即便处于同一地层岩组,渗透系数也有较大差别;在莫高窟围岩中存在渗透性好的地层,使水汽通过这些地层岩组向洞窟内运移成为可能;鉴于文物的特殊性等原因,在无法直接测得围岩渗透性的情况下,高密度电阻率法和X射线CT扫描是了解围岩渗透特性有效的办法。

Research on permeability of surrounding rock at Dunhuang Mogao Grottoes

Influenced by the material and natural environment, the wall paintings of Dunhuang Mogao grottoes have many diseases: flaking, disruption, detachment and loss; and many researches have proved that these diseases are caused by moving of salts; however the moisture is the main factor for the activation and moving of the salt. So, research on rock permeability of the Mogao Grottoes can explain regulations of water migrations and help us to learn the mechanism of wall painting deterioration. This article adopted the test of designated water level in situ to get the permeation coefficient of different groups of surrounding rocks, the test of high-intensively resistivity permeation monitoring in situ experiments; X-Ray CT account the void ratio to study the permeability of the surrounding rocks. We know that different rock strata of Mogao Grottoes have different permeabilities; even the rocks from the same stratum have very different permeability coefficients. Some stratum with good permeability makes it possible that the water permeates inside the cave through the rock layers. Due to the particularity of culture relics and some other reasons, high-density electric resistivity method and X-Ray CT scanning are efficient ways to learn the permeability of surrounding rocks under the situation that we can't measure it directly.