The Loess Plateau serves as a vital energy base in China, where proven reserves of coal, petroleum, and natural gas account for 64%, 29.6%, and 39.4% of the national totals, respectively. These resources play a critical role in securing energy supply for the East and North China regions. Meanwhile, the region has fragile ecological environments and frequent geological disasters, making it one of the areas with the most severe geological hazards. In recent years, as global warming and the rainfall belt gradually shifts northward, intensifying rainfall‑evaporation cycles and further increasing the collapse risk of loess sites. Loess exhibits notable collapsibility and a porous structure, while the fissures within it can form preferential flow paths that accelerate water infiltration and soil erosion. The main disaster types include five categories: landslides, mudslides, toppling, collapses, and ground fissures, totaling 26,775 occurrences. Among these, toppling, collapses, and ground fissures account for 39.54%, while landslides and mudslides make up 60.46%, of which disasters in the energy base are primarily dominated by toppling, collapses, and ground fissure. The evolutionary pattern and mechanism of rainfall-evaporation cycle-driven subsidence-collapse in fissured loess remain unclear. This study employs large-scale physical model tests to simulate the entire process, aiming to monitor hydro-mechanical responses, clarify unsaturated infiltration and deformation-failure mechanisms, and establish a framework for progressive collapse controlled by hydro-mechanical mutual feedback.
This study conducted large-scale (1:10) physical model tests using a self-developed apparatus, simulated the entire process of subsidence-settlement-collapse in fissured loess sites under rainfall-evaporation cycle, with systematic monitoring of moisture content, pore pressure, soil pressure, and strain/deformation dynamics response.
Unsaturated infiltration in fissured loess exhibits a marked dual-domain behavior. Preferential flow through the fissure domain leads to rapid advancement of the wetting front with a funnel-shaped, while matrix flow was slow, leading to significant hydro-mechanical response differentiation. This induced progressive differential settlement that accumulated over cycles. The collapse evolution follows a six-stage process: (1) preferential infiltration initiation, (2) drying shrinkage, (3) hydro-collapsible deformation, (4) fissure regeneration and propagation, (5) soil erosion and fluidization, and (6) final collapse. The mechanism is driven by hydro-mechanical feedback: preferential flow weakens the soil and redistributes stress, while evaporation promotes fissure development, further enhancing preferential flow. Repeated cycles lead to accumulated deformation and erosion-induced fluidization, causing structural collapse. The results provide critical scientific support for geohazard assessment and prevention in the Loess Plateau energy base, with significant value for improving geological risk control in major engineering projects.
黄土高原是中国重要的能源基地，煤炭、石油和天然气的已探明储量分别占全国总量的64%、29.6%和39.4%。这些资源在保障华东和华北地区的能源供应方面发挥着关键作用。与此同时，该地区生态环境脆弱且地质灾害频发，是地质灾害最严重的地区之一。近年来，随着全球变暖和降雨带逐渐向北移动，降雨蒸发周期加剧，黄土遗址的倒塌风险进一步增加。黄土表现出显著的塌陷性和多孔结构，而其裂缝可能形成优先流动路径，加速水的渗透和土壤侵蚀。主要灾害类型包括五类：滑坡、泥石流、倒塌、坍塌和地裂，共计发生26,775起。其中，倒塌、坍塌和地裂占39.54%，滑坡和泥石流占60.46%，其中能源基础灾害主要由倒塌、坍塌和地裂为主。降雨-蒸发循环驱动的裂隙黄土沉降-崩塌的演化模式和机制尚不明确。本研究采用大规模物理模型测试模拟整个过程，旨在监测水力机械响应，阐明不饱和入渗和变形失效机制，并建立由水力机械相互反馈控制的渐进坍塌框架。本研究使用自制设备进行了大规模（1：10）物理模型测试，模拟了裂缝黄土遗址在降雨-蒸发循环下的全部沉降-沉降-崩塌过程，系统监测了含水量、孔隙压力、土壤压力及应变/变形动力学响应。裂缝黄土中的不饱和渗透表现出明显的双域行为。优先流动通过裂隙域导致湿润前沿呈漏斗状快速推进，而基质流动则较慢，导致显著的水力力学响应差异。这导致了逐步积累的差异沉降，并伴随着周期积累。坍塌演化遵循六个阶段过程：（1）优先入渗启动，（2）干燥收缩，（3）水压塌变形，（4）裂隙再生与扩展，（5）土壤侵蚀与流化，以及（6）最终塌陷。该机制由水力机械反馈驱动：优先流动削弱土壤并重新分散应力，而蒸发则促进裂缝形成，进一步增强优先流动。反复循环导致堆积的变形和侵蚀引起的流化，导致结构坍塌。结果为黄土高原能源基底地质灾害评估和预防提供了关键科学支持，对改善重大工程项目中的地质风险控制具有重要价值。

Fissured loess site; Subsidence-collapse; Unsaturated infiltration; Rainfall-evaporation cycle.