基于红外温度场和近红外谱表征的岩质文物遗址中水分吸附-运移机理

Adsorption and transportation of water in rock media under temperature influence is the key factor causing the stone cultural relics diseases in arid and semi-arid regions. Infrared thermography and near-infrared spectroscopy are used simultaneously for the first time for the real-time and quantitative monitoring the temperature field and water-content distribution during non-gravity water transportation process in rocks. This project is directed at investigation of the infrared radiation features occurred during the adsorption and transportation of water in rocks by characterization of the real-time changes of the water content influenced by the temperature gradient; exploration of the dynamic law and the condition and criterion for initiating the water transportation process according to the monitored results of the water adsorption. Based on the experimental results, quantitative relation between the temperature and water-bearing content is established by utilizing the adsorption thermodynamic principle, in order to describe the features of the adsorption energy change, reveal the adsorption mechanism and transportation law of the water-bearing rocks under the action of temperature gradient. Outcome of this project will provide theoretical and technical supports to the preventive protection and governance of grottoes weathering, mural lesions and other disasters in arid and semi-arid regions.

温度梯度影响下的岩石介质中水分吸附-运移规律是干旱半干旱地区岩质文物病害成因的关键。项目首次采用红外热像和近红外光谱分析相结合的方法，实时、定量监测岩石中“非重力水分”运移中的温度场和水分分布特征；以温度梯度影响下的含水量实时变化特征为切入点，重点研究岩石水分吸附-运移过程中的红外辐射特征，确定红外辐射强度的动态变化规律； 根据结合水形成与迁移的监测结果，确定含水量的动态变化规律；建立水分运移启动条件和判据。 在此基础上，利用吸附热力学原理，建立温度场与含水量的定量关系，描述含水岩石的吸附能变化特征，揭示在温度梯度作用下，岩质文物遗址中水分吸附的机理和运移规律，为干旱半干旱地区石窟风化与壁画病变等灾害的预防性保护和治理提供理论依据。

在干旱半干旱地区，岩质文物遗址因其中的水分吸附-运移诱发一系列病害问题，至今运移机理和规律仍然是一项具有挑战性的工作。本项目采用红外热像和近红外光谱分析相结合的方法，深入研究了粉砂岩、砾岩、夯土中的水分运移过程中的红外辐射温度场和水分分布特征，（1）建立了基于红外辐射温度的定量描述理论体系：①建立了基于熵理论的水分运移启动判据；②运用热力学第一定律，建立了描述红外辐射温度与含水量关系的定量方程；③以定量方程为基础，提出识别水分运移湿润锋的方法；④进行了莫高窟崖壁粉砂岩水分运移的室内试验，利用热成像观测结果对上述理论体系进行了验证；⑤深入研究了夯土在不同吸水阶段的吸水增量与红外辐射温度之间的关系，提出了基于互信息的岩土介质非饱和-饱和过渡状态的识别方法，并对其进行了室内实验验证；（2）建立了近红外光谱特征表征的含水量识别模型：①利用互信息作为相关程度的度量标准，分别采用Best Individual Feature法和Maximal Information Coefficient法，研究了特征变量与含水量之间依赖关系的强弱程度，筛选了不同岩性的岩石近红外光谱的特征变量；②利用相关系数法分析了不同含水量的粉砂岩试样的近红外光谱特征与含水量之间的相关程度，在强相关谱段处构建了多元回归模型，并对模型进行了验证分析。上述基础理论研究，为干旱半干旱地区石窟风化与壁画病变等灾害的预防性保护和治理提供重要的理论支撑。