不同岩体交叉裂隙结构下滴状流的分流机理研究

    Study on diversion mechanism of drip flow in different rock mass intersection fracture structures

    • 摘要: 岩土体中存在由大量天然裂隙组成的复杂且庞大的裂隙结构,地表积水沿裂隙下渗将引起岩土体力学性质改变。由于交叉裂隙对于非饱和裂隙结构渗流起重要控制作用,采用相场方法模拟两相界面,对不同几何结构的交叉裂隙中滴状流进行了计算。探讨了交叉裂隙的几何结构(开度比、倾斜角、裂隙夹角等)对于液滴在裂隙交叉口处分流行为的影响,并结合XGBoost方法对几何结构的3个参数进行了特征重要性分析。结果表明:通过与文献试验结果对比,验证了该计算方法的准确性和有效性;液滴在裂隙交叉口处表现出完全分流、部分分流且无拖曳、部分分流有拖曳和不分流4种流动形态;当液滴长度为2 cm时,随着裂隙开度比W_\textb、裂隙整体与水平面夹角\alpha 及裂隙间夹角\beta 的增大,液滴的分流比例\eta 在减小甚至出现不分流现象;在 W_\textb > 0.4 时出现明显的拖曳现象、20° \leqslant \alpha \leqslant 35°时液滴完全分流进入另一通道、当\alpha \leqslant 15°时,液滴在到达交叉口处时将不在流动,储存于裂隙中;通过特征重要性分析,发现裂隙整体与水平面夹角\alpha 和裂隙间夹角\beta 对于液滴分流行为的影响远高于裂隙开度比W_\textb。将此计算模型推广至裂隙网络结构中,对自然界中地表积水在裂隙结构中的非饱和渗流进行了分析。发现裂隙结构中常出现由于裂隙内空气的“阻塞效应”引起的非饱和流动现象,液滴在其中选择的“优势通道”与出入口间通道的笔直程度、过流面积等因素密切相关。研究结果可为工程中随机裂隙、裂隙结构的渗流仿真和工程设计提供一定的理论分析基础和方法借鉴。

       

      Abstract: Fractured geomaterials contain complex networks of natural fractures that influence hydro-mechanical behaviors through unsaturated flow. This study investigates droplet dynamics at fracture intersections using phase-field modeling, focusing on geometric controls (aperture ratio, tilt angle, and intersection angle) about splitting behavior. XGBoost-based feature importance analysis reveals the relative impacts of these parameters. Validated against experimental data, the work identifies four distinct flow regimes: complete splitting, partial splitting (with/without dragging), and non-splitting. When the droplet length is 2 cm, increasing the fracture aperture ratio W_\textb, the tilt angle \alpha of the fracture relative to the horizontal plane, and the intersection angle \beta leads to a decrease in the droplet splitting ratio \eta , and in some cases, no splitting occurs. At the condition W_\textb > 0.4 , a noticeable dragging phenomenon is observed; at the condition 20^ \circ \leqslant \alpha \leqslant 35^ \circ , the droplet completely splits into another channel; and at the condition \alpha \leqslant 15^ \circ , the droplet ceases to flow and gets stored in the fracture at the intersection. Feature importance analysis reveals that the tilt angle \alpha of the fracture relative to the horizontal plane and the intersection angle \beta have a far greater impact on droplet splitting behavior than the aperture ratio W_\textb. The model is then extended to a fracture network structure to analyze the unsaturated infiltration of surface water in fracture systems in nature. It is found that unsaturated flow phenomena caused by the "blocking effect" of air in the fractures are common. The "preferred channel" chosen by the droplet is closely related to factors such as the straightness and flow area between the inlet and outlet of the channels. These results provide theoretical insights and methodological references for simulating flow in fractured structures and design engineering solutions involving random fractures.

       

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