Abstract. Stony soils that have a considerable amount of rock fragments are widespread around the world. However, experiments to determine effective hydraulic properties of stony soils (SHP), i.e. the water retention curve (WRC) and hydraulic conductivity curve (HCC), are challenging. Installation of measurement devices and sensors in these soils is difficult and the data are less reliable because of high local heterogeneity. Therefore, effective properties of stony soils especially in unsaturated hydraulic conditions are still not well understood. An alternative approach to evaluate the SHP of these systems with internal structural heterogeneity is numerical simulation. We used the Hydrus 2D/3D software to create virtual stony soils in 3D and simulate water flow for different volumetric rock fragment contents, f. Soils with volumetric stone contents from 11 to 37 % were created by placing impermeable spheres in the form of rock fragments in a sandy loam soil. Time series of local pressure heads in various depths, mean water contents and fluxes across the upper boundary were generated in a virtual evaporation experiment. Additionally, a multi-step unit gradient simulation was applied to determine effective values of hydraulic conductivity near saturation up to pF = 2. The generated data were evaluated by inverse modeling, assuming a homogeneous system, and the effective hydraulic properties were identified. The effective properties were compared with predictions from available scaling models of SHP for different volumes of rock fragments. Our results showed that scaling the WRC of the background soil based on only the value of f gives acceptable results in the case of impermeable rock fragments. However, the reduction of conductivity could not be simply scaled by the value of f. Predictions were highly improved by applying the Novák, Maxwell, and GEM models to scale the HCC. The Maxwell model matched the numerically identified HCC best.

中文翻译：

---

通过逆向建模识别的 3D 虚拟石土的有效水力特性

摘要。含有大量岩石碎片的石质土壤在世界各地普遍存在。然而，确定石质土壤 (SHP) 的有效水力特性的实验，即保水曲线 (WRC) 和导水率曲线 (HCC)，具有挑战性。在这些土壤中安装测量设备和传感器很困难，而且由于局部异质性高，数据不太可靠。因此，石质土壤的有效特性，尤其是在非饱和水力条件下的有效特性仍不清楚。评估具有内部结构异质性的这些系统的小水电的另一种方法是数值模拟。我们使用 Hydrus 2D/3D 软件在 3D 中创建虚拟石质土壤，并模拟不同体积岩石碎片含量的水流，f。通过在砂质壤土中以岩石碎片的形式放置不透水的球体，可以形成体积石含量为 11% 至 37% 的土壤。在虚拟蒸发实验中生成了不同深度的局部压力水头、平均含水量和跨越上边界的通量的时间序列。此外，应用多步单元梯度模拟来确定接近饱和的水力传导率的有效值，最高可达 pF = 2。通过逆向建模评估生成的数据，假设系统为均质系统，并确定了有效的水力特性。针对不同体积的岩石碎片，将有效特性与 SHP 可用比例模型的预测进行了比较。我们的结果表明，在不可渗透的岩石碎片的情况下，仅基于 f 值缩放背景土壤的 WRC 给出了可接受的结果。然而，电导率的降低不能简单地由 f 的值来衡量。通过应用 Novák、Maxwell 和 GEM 模型来扩展 HCC，预测得到了极大改进。Maxwell 模型与数字识别的 HCC 最匹配。