Cracks generated in shrink-swell soils detrimentally affect hydraulic and mechanical properties of soils, and alter soil-water processes, such as gas diffusion, water flow, solute transport, and root penetration. Root additives and salinity beget physicochemical changes in soils, resulting in variations of crack morphology. Understanding these variations provides effective means of crack utilization or prevention. In this study, we investigated the effects of maize roots and sodium chloride (NaCl) on crack dynamics and morphology in shrink-swell light clays. Drying experiments were conducted in soils containing roots (root densities: 0, 0.5, 1.0 and 1.5 cm/cm³) or NaCl (mass contents: 0.03, 1.0, 1.5 and 2.0 %). Crack evolution patterns were photographed at regular intervals and crack parameters were calculated from the resulting images using morphological algorithms. We investigated the dynamic geometry, topology, and statistical behaviors of cracks. Results indicate that incorporating maize roots effectively restrained crack area and width, but increased crack length, tortuosity, and number of cracks. Crack networks in root-treated soils contained a vast number of dead-ends and displayed pronounced fragmentation and low connectivity. Distribution of crack intersection angle well approximate normality with a mean around 120°. The bonding and friction between roots and particles, the bridging effects, stiffness, and ductility of roots improved the soil tensile strength and altered the intrinsic release criteria of tensile stress. The NaCl treatments increased crack area and width but decreased total crack length and tortuosity. With a slight amount of NaCl, the crack network tended to be highly connected with no dead-ends. Distribution of crack intersection angle in sodic soils exhibited asymmetric bimodality and was well described by a mixture of two Gaussian distributions, with primary and secondary peaks around 105° and 165°, respectively. We proposed a statistical function that describes crack area probability distribution considering water content as a variable, which proved to be a good fit in modeling dynamic statistics of crack patterns. Our results provide compelling evidence of how roots and salinity alter crack evolution, dynamics, and morphology in shrink-swell soils, which will be beneficial in crack inhibition and utilization, and in hydrological use such as water management in saline-sodic soils and prevention of preferential flow. However, cracking behaviors are highly susceptible to sample size effects and basal boundary. We hypothesize cracking behaviors (in roots- or salinity-treated soils) in small scale and in-situ scale are dimensionally similar, and the validity of these conclusions being generalized to in-situ cracked soils should be further investigated.

收缩膨胀土壤中产生的裂纹不利地影响土壤的水力和机械性能，并改变土壤-水的过程，例如气体扩散，水流，溶质迁移和根系渗透。根系添加剂和盐分会引起土壤的物理化学变化，从而导致裂缝形态的变化。了解这些变化可提供有效的裂纹利用或预防方法。在这项研究中，我们研究了玉米根和氯化钠（NaCl）对收缩膨胀轻质粘土的裂纹动力学和形态的影响。在含有根的土壤中进行干燥实验（根密度：0、0.5、1.0和1.5 cm / cm ³）或NaCl（质量含量：0.03、1.0、1.5和2.0％）。定期拍摄裂纹发展模式，并使用形态学算法从所得图像中计算出裂纹参数。我们研究了裂纹的动态几何形状，拓扑和统计行为。结果表明，掺入玉米根能够有效地抑制裂纹的面积和宽度，但增加了裂纹的长度，曲折度和裂纹数量。经过根部处理的土壤中的裂缝网络包含大量死角，并表现出明显的碎片化和低连通性。裂纹相交角的分布很好地近似于正态分布，平均值约为120°。根与颗粒之间的键合和摩擦，桥接效应，刚度，根的延展性提高了土壤的抗张强度，并改变了张应力的内在释放标准。NaCl处理增加了裂纹的面积和宽度，但减小了总的裂纹长度和曲折度。含有少量的氯化钠时，裂纹网络趋于高度连接，没有任何死角。钠盐土壤中裂缝相交角的分布表现出不对称的双峰性，并通过两种高斯分布的混合得到了很好的描述，主峰和次峰分别在105°和165°左右。我们提出了一种统计函数，该函数描述了以水含量为变量的裂缝区域概率分布，这被证明非常适合对裂缝模式的动态统计建模。我们的结果提供了令人信服的证据，证明根和盐分如何改变裂纹的发展，动力学，收缩膨胀土壤中的形态和形态，这将有利于裂纹的抑制和利用，有利于水文应用，例如盐碱土壤中的水管理和防止优先流动。但是，开裂行为极易受到样本大小影响和基边界的影响。我们假设小规模的裂化行为（在经过根或盐分处理过的土壤中）和原位尺度在尺寸上是相似的，这些结论推广到原位裂化土壤的有效性应进一步研究。