Qing Cheng

Although overland flow strongly governs soil erosion and sediment transport, its response to desiccation cracking induced by drying‐wetting cycles is not fully understood. This study addresses this gap through laboratory rainfall simulations on a slope model subjected to three drying‐wetting cycles. Soil moisture and suction were monitored at shallow depth, crack patterns were quantified through image processing, and runoff and sediment yields were measured during rainfall events. Infrared thermography was applied to capture flow velocity and spatial organization. Results show that drying‐wetting cycles accelerated moisture loss, steepened suction gradients, and promoted the initiation and propagation of cracks. Crack ratio and total crack length increased markedly during the first two cycles but stabilized in the third, indicating that the slope surface had reached a state of structural equilibrium. Runoff generation was influenced by both antecedent moisture and crack development: higher initial moisture reduced infiltration capacity and produced rapid, high‐magnitude runoff, while progressive cracking enhanced infiltration and weakened runoff response in later cycles. Sediment yield closely followed runoff intensity, peaking in the second cycle due to the influence of reduced infiltration and structural weakening. Infrared thermography showed that leading‐edge velocity declined during rainfall while the continuity‐derived equivalent runoff depth increased, reflecting different responses of local tracer‐front propagation and integrated runoff generation to evolving flow connectivity and effective hydraulic resistance. Across cycles, leading‐edge velocity rose initially and then declined, consistent with the transition from high antecedent moisture and structural weakening to stabilized crack networks. Spatial indices further confirmed this shift, indicating progressive increases in surface roughness, enhanced flow dispersion, and shortened effective flow paths.

Desiccation cracking significantly impacts the engineering properties of soils, influencing fluid infiltration and structural stability. A key phenomenon in desiccation cracking is the size effect, where soil dimensions, including thickness and radius, alter cracking behavior. However, the size effect remains poorly understood, particularly in linking laboratory-scale findings to field conditions. Existing studies are often limited to small laboratory samples, leading to discrepancies in crack behavior across scales and a lack of standardized guidelines for determining suitable sample sizes in laboratory tests. This study investigates the size effect on desiccation cracking in clayey soils and identifies suitable laboratory sample sizes to represent field-scale cracking patterns. Desiccation tests were performed on soil samples with varying radii (25-100 mm) and thicknesses (5-18 mm). Cracking behavior during drying and equilibrium-state crack patterns were analyzed. A size parameter (λ), defined as the ratio of sample radius to thickness, was introduced to characterize the soil's volumetric size. Results reveal three distinct stages of the size effect: (i) the crack-free stage (λ

Near‐surface soils are increasingly exposed to repeated wetting‐drying (W‐D) cycles under intensifying climate change. Such hydroclimatic fluctuations progressively degrade soil structure and mechanical properties, posing risks to the stability of earthen slopes and infrastructures. This study aims to investigate how climate‐driven W‐D cycles influence the tensile behavior and microstructural evolution of compacted near‐surface soils. Direct tensile tests were conducted on soil specimens after different number of W‐D cycles, followed by measurements of water content, void ratio and suction. Microstructural changes were analyzed using mercury intrusion porosimetry. Results show that tensile strength decreases significantly with increasing W‐D cycles and tends to stabilize after three cycles. This reduction in tensile strength indicates a decreased resistance to crack initiation and propagation, making surface soils more susceptible to desiccation cracking under successive W‐D cycles. Microstructural analysis reveals a trimodal pore size distribution in soil specimens, characterized by macropores, mesopores and micropores. With continued cycles, macropores collapse significantly, micropores remain relatively stable, while mesopores and potential macrocracks unexpectedly increase. The soil microstructure approaches an equilibrium state after three W‐D cycles. Based on these observations, a physically meaningful damage coefficient is proposed to quantify climate‐induced microstructural damage. A concise predictive model incorporating this coefficient is developed and validated to describe the evolution of tensile strength. These findings provide microstructural insights into the climate‐driven mechanical degradation of near‐surface soils, with broad implications for cracking, erosion, and shallow instability of earth structures under a changing climate.

Soil desiccation cracking is a ubiquitous natural phenomenon that intensifies under drought conditions. Experimental tests and field observations have shown that desiccation cracks often initiate at defects such as foreign inclusions, tiny pits, and uneven soil surfaces. However, the underlying mechanisms by which defects affect soil desiccation cracking remain poorly understood due to the lack of stress field information from laboratory tests. This study utilizes the three‐dimensional Discrete Element Method to examine the micromechanics of how defects impact soil desiccation cracking. In this research, sand inclusions were used to model defects, and the effects of defect size, quantity, and distribution were carefully analyzed. The findings reveal that defects cause significant local stress concentration, triggering arc‐shaped micro‐cracks that eventually develop into Y‐shaped cracking patterns. Defects influence the surrounding maximum principal tensile stress field within a range of 2–2.5 times the defect diameter. When a crack enters this influence zone, it is drawn toward the defect. The presence of defects increases soil heterogeneity, disrupting the sequential and hierarchical pattern of desiccation cracks observed in homogeneous soil specimens. Consequently, the crack network in soils containing defects consists of both orthogonal and non‐orthogonal cracks.

Climate‐induced desiccation cracks exhibit a hysteresis behavior, referred to as crack dynamic hysteresis (CDH), where they display different geometric characteristics during the drying and wetting phases at constant soil water content. This phenomenon has a complex effect on slope stability, an aspect often overlooked in analytical and numerical methods. In this study, we conducted experimental and numerical analyses to provide new insights into the effects of the CDH on slope stability. A series of laboratory experiments on desiccation cracking under drying‐wetting cycles were performed. The testing results were used to develop and validate an extended dynamic dual‐permeability model. The proposed model was integrated into a set of slope stability analyses using the finite element method. The numerical model results show that CDH causes greater fluctuations in crack dynamics and increases soil water retention under drying‐wetting cycles. Neglecting this phenomenon leads to underestimation of slope stability during dry conditions and overestimation during wet conditions, with these discrepancies becoming more pronounced as the cycles progress. Furthermore, CDH changes the mechanical properties of soil, transitioning relatively stable zones to regions prone to localized instability. These unstable zones present significant challenges for accurately analyzing and managing slopes with cracked soil layers. Monitoring groundwater fluctuations and local crack development after heavy rainfall events is essential for mitigating localized slope collapses.