Fractures provide pathways for preferential flow, whereas porous rock acts as storage that delays fluid propagation through matrix imbibition. These dual-porosity mechanisms are investigated in laboratory experiments of partially saturated fracture infiltration. We analyze flow dynamics in terms of the fluid penetration depth in the fracture and delineate fracture- and matrix-dominated flow regimes at different flow rates. We compare wetting front propagation in fracture and matrix and examine the interference of matrix-wetting fronts with the lateral system boundary. The experimental data are interpreted using the analytical model of Nitao (1991), which accounts for the impact of fracture-matrix interactions on fluid propagation in the fracture. We find that matrix imbibition affects the observed discontinuous, partially saturated fracture flow to behave, on average, like plug flow. Consequently, and within the range of applied flow rates above a critical threshold, the model’s plug flow assumption is not a relevant precondition for its applicability. Fluid propagation in the fracture exhibits three characteristic scaling regimes (FP1-3) corresponding to the matrix imbibition state. Only two scaling regimes are established for flow rates below a critical threshold, hence required to recover bulk infiltration for the chosen geometry. Furthermore, wetting fronts switch from fracture-to matrix-dominated at moderate to high flow rates, indicating a flow-rate-dependent limitation of fracture-dominated infiltration depth. While the scaling regimes agree with experiments for applied flow rates above the critical threshold, the model underestimates the initial penetration depth below. Here, we observe the direct onset of flow regime FP2 and the delayed transition into FP3.

中文翻译：

---

实验和理论中的部分饱和裂缝基质渗透


裂缝提供了优先流动的通道，而多孔岩石则充当储存层，通过基质自吸延迟流体传播。这些双孔隙机制在部分饱和裂缝渗透的实验室实验中进行了研究。我们根据裂缝中的流体渗透深度来分析流动动力学，并描绘不同流速下裂缝和基质主导的流动状态。我们比较了裂缝和基质中的润湿锋传播，并检查了基质润湿锋与横向系统边界的干扰。实验数据使用 Nitao (1991) 的分析模型进行解释，该模型解释了裂缝-基质相互作用对裂缝中流体传播的影响。我们发现，基质渗吸会影响观察到的不连续、部分饱和的裂缝流，平均而言，其行为类似于活塞流。因此，在高于临界阈值的应用流量范围内，模型的活塞流假设并不是其适用性的相关先决条件。裂缝中的流体传播表现出与基质渗吸状态相对应的三种特征缩放状态（FP1-3）。对于低于临界阈值的流速，仅建立两种缩放方案，因此需要恢复所选几何形状的大量渗透。此外，润湿锋在中到高流速下从裂缝主导转变为基质主导，这表明裂缝主导的渗透深度存在与流速相关的限制。虽然缩放机制与高于临界阈值的应用流速的实验一致，但该模型低估了低于临界阈值的初始穿透深度。在这里，我们观察到流态 FP2 的直接开始和延迟过渡到 FP3。