斜坡非饱和带低渗透岩石中水气分子的扩散机理

根据分子运动论,对水气分子在低渗透岩石中的扩散模式进行研究,得出水气分子中的主要气体H2O、CO2以及O2在新鲜二长岩和玄武岩中的扩散为过渡型扩散.通过计算得到三者的有效扩散系数.以微砂质细粒长石石英砂岩为研究对象,在电子显微镜下获得砂岩的铸体薄片图像,并对其进行处理,建立砂岩的二维孔隙扩散模型,模拟岩石风化过程中水气分子在砂岩孔隙内的扩散过程,得到砂岩模型内部的速度分布图、压力分布图和雷诺数图.结果表明,天然状态下,水气分子的流动主要出现在胶结物受腐蚀的风化区域.胶结物溶蚀产生的贯通孔隙是水气分子的主要扩散通道和贮存场所.水气分子在砂岩内部孔隙中的流动符合流体流动的基本规律,雷诺数的量级为10-3,流动状态为层流.同时对风化岩石的剖面进行分带,分析了水气分子扩散对岩石风化产生的影响.

Diffusion mechanism of water vapor in the unsaturated zone of slope with low permeability

According to the theory of molecular motion, the diffusion mode of water vapor in the low-permeability rocks was studied in this paper and found that diffusion patterns of the main components in water vapor, such as H2O, CO2 and O2 , were defined as transitional forms in the fresh monzonite and basalt. The effective diffusion coefficients of these three kinds of gas in the monzonite and basalt were acquired by calculation. Micro sandy fine feldspathic quartz sandstone was analyzed by the sandstone casting thin-section image processing under an electron microscope, and therefore two-dimensional sandstone pore diffusion model was established in order to simulate the diffusion process of water vapor in the weathering process of sandstone. The velocity distribution, pressure distribution and Reynolds number of the internal model of sandstone were obtained. The results show that the flow of water vapor in the natural state mainly occurr in the weathered corrosion area of the cements. The through-pores formed by dissolution of cements in the low-permeability rocks were the main diffusion channels and storage sites of water vapor in weathering process. The flow of water vapor in the pores of the sandstone complied with the basic rules of fluid flow, and the Reynolds number was 10 -3 . The flow state was laminar. At the same time, the section of weathered rock was divided into different zones and the influence of diffusion of water vapor on the weathered rock mass was analyzed.