An experimental study of spatial-temporal evolution of water-soil response and stability of a rainfall-induced accumulation landslide
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摘要:
降雨在松散堆积土中入渗引起内部水土力学的变化是影响稳定性的关键。目前研究多侧重考虑颗粒粒径、含量等因素对斜坡破坏的影响，但是针对斜坡体内部水土响应及稳定性时空演化方面的研究存在不足。基于野外滑坡案例，通过室内降雨滑坡模型试验、土力学试验和理论分析手段，研究了降雨触发松散堆积体斜坡变形破坏过程及模式，采用Van Genuchten模型（VG模型）重构了土体的土-水特征曲线，重点探究了斜坡内部水土力学变化以及稳定性时空演化规律。结果表明：（1）堆积体斜坡破坏经历了微裂隙发育-局部破坏-整体破坏3个阶段，呈现出“初期拉裂-坡面坍塌-塑性滑动”的破坏模式；（2）入渗过程斜坡体积含水率以及孔隙水压力急速增加，而土颗粒之间基质吸力下降甚至消散，促进了斜坡破坏发展；（3）土体力学强度随体积含水率升高呈指数下降，体积含水率为36.3%时，有效黏聚力和有效内摩擦角仅为0.27 kPa、3.39°；（4）基于极限平衡理论和斜坡土水特征监测数据，构建了斜坡稳定性时空演化图谱，与模型试验破坏特征有较好的一致性。研究结果对降雨作用下的堆积层斜坡监测预警与防灾减灾提供理论支撑。
Abstract:The change of soil and water mechanics caused by rainfall infiltration in loose soil is the key to affect stability. At present, most studies focus on the influence of particle size, content and other factors on slope failure. However, the research on the internal water-soil response and spatial-temporal evolution of slope stability is insufficient. Based on a field landslide case, this study explores the deformation and failure processes and mode of loose accumulation slope triggered by rainfall through the flume test, soil mechanics test, and theoretical analysis. The Van Genuchten model (VG model) is used to reconstruct the soil-water characteristic curve of the soil, and the mechanical change of soil and water in the slope and the temporal and spatial evolution of stability are mainly explored. The results show that: (1) The failure processes of the accumulation slope emerge in three stages, that is, the micro-fracture development stage, local failure stage and complete collapse stage, presenting the failure mode of “initial cracking-slope collapsing-plastic sliding”. (2) The volumetric water content and pore water pressure of slope increase rapidly during infiltration, while the matric suction between soil particles decreases or even dissipates, which promotes the development of slope failure. (3) The mechanical strength of soil decreases exponentially with the increasing volumetric water content. When the volumetric water content is 36.3%, the effective cohesion and effective internal friction angle are only 0.27 kPa and 3.39°. (4) Based on the limit equilibrium theory and the monitoring data of slope soil-water characteristics, the spatio-temporal evolution map of slope stability is constructed, which is in good agreement with the failure characteristics of the model test. The research results provide theoretical support for monitoring and early warning of accumulation slope under rainfall and disaster prevention and mitigation.
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Key words:
- accumulation slope /
- rainfall infiltration /
- flume test /
- stability analysis /
- hydrological response
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表 1 斜坡稳定性分析土体参数（t=10 min）
Table 1. Soil parameters for slope stability analysis (t=10 min)
参数 Z/cm c'/kPa φ'/（°） γd/（kN·m−3） β/（°） θr/% θs/% 数值 5.06 3.14 28.74 11.86 25 3 49 12.47 3.33 12.83 3.34 15.00 3.37 25.27 3.45 
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