斜坡非饱和带低渗透岩石结构体风化前锋扩展机理

发布时间：2018-03-14 02:33

本文选题：非饱和带　切入点：风化前锋　出处：《昆明理工大学》2017年硕士论文　论文类型：学位论文

【摘要】：本文主要对非饱和带低渗透岩石结构体中的风化前锋扩展机理问题进行研究,旨在阐明风化作用下岩石内部风化前锋的扩展过程及不同湿度环境对风化前锋扩展产生的影响。主要采用化学全分析、岩石薄片鉴定、电子显微镜扫描等试验方法,并结合理论研究和数值模拟两方面进行分析。结果表明:岩石结构体风化前锋界限附近的岩石矿物结构主要以物理风化为主,化学风化相对较少,处于不同风化带的岩石矿物结构存在明显差异。风化初期,水气分子在浓度梯度和大气压力的驱使下侵入岩石内部,受优先风化效应的影响,产生了风化前锋。随后在浓度梯度作用下,水气开始在岩石内部扩散。数值模拟结果表明:胶结物溶蚀产生的贯通孔隙是水气在低渗透岩石中的贮存场所和主要扩散通道。水气进入岩石后,沿指向结构体内部的法线方向扩散,表现形式为水气从两侧相向扩散,造成岩石结构体棱角钝化。相对湿度的变化会影响岩石的完全风化时间和风化前锋的扩展速率。在理想条件下,风化前锋的扩展速率遵循先逐渐减小后迅速增大的规律。研究成果对于岩崩、泥石流等地质灾害和工程问题具有一定的实际意义。本文取得的主要成果如下:(1)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。(2)天然状态下,水气分子的贮存和流动主要出现在胶结物被腐蚀的贯通孔隙内,水气在贯通孔隙内的流动符合流体流动的一般规律。(3)相对湿度的变化对岩石风化的影响主要表现为相对湿度越高,岩石完全风化所需时间越短。低湿度条件下,风化前锋扩展速率的变化受空气中实际水气压的控制。高湿度条件下,风化前锋的扩展速率受浓度梯度控制。
[Abstract]:In this paper, the propagating mechanism of weathering front in low permeability rock structure in unsaturated zone is studied. In order to elucidate the propagation process of weathering front in rock under weathering and the influence of different humidity environment on weathering front propagation, chemical total analysis, rock sheet identification, electron microscope scanning and other test methods are mainly used. In combination with theoretical research and numerical simulation, the results show that the rock mineral structures near the front boundary of weathering of rock structures are mainly physical weathering, while chemical weathering is relatively less. The mineral structure of rocks in different weathering zones is obviously different. In the early stage of weathering, water vapor molecules intrude into the rock interior under the influence of concentration gradient and atmospheric pressure, and are affected by the preferential weathering effect. A weathering front is produced. Then, under the concentration gradient, The numerical simulation results show that the through-hole produced by the dissolution of cement is the storage place and main diffusion channel of water gas in low permeability rock. Diffusing along the normal direction pointing to the interior of the structure, in the form of water vapor diffusing from both sides, The change of relative humidity will affect the complete weathering time of rock and the spreading rate of weathering front. The spreading rate of weathering front follows the law of decreasing at first and then increasing rapidly. Geological hazards such as debris flow and engineering problems have certain practical significance. The main results obtained in this paper are as follows: (1) taking micro-sand fine feldspar quartz sandstone as the research object, the cast thin slice images of sandstone are obtained under electron microscope. In the natural state of sandstone, the storage and flow of water gas molecules mainly occur in the penetrating pores where the cement is corroded. The effect of the change of relative humidity on rock weathering is that the higher the relative humidity, the shorter the time required for complete weathering of rock. The variation of the propagation rate of the weathering front is controlled by the actual water pressure in the air, and the spreading rate of the weathering front is controlled by the concentration gradient at high humidity.
【学位授予单位】：昆明理工大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TU45

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