崩滑碎屑体堵江成坝研究综述与展望

堰塞坝是由崩塌、滑坡、泥石流等斜坡失稳体堵塞河流而形成的天然坝体。我国是堰塞坝的高发区,在作者统计的全世界范围内堰塞坝案例中,发生在我国的高达758例,占比59%。近年来,频发的地质构造活动和极端气候灾害(台风、暴雨、融雪等)诱发了大量的堰塞坝,严重威胁所在流域的生命财产安全。崩滑碎屑体堵江形成的堰塞坝通常结构松散、稳定性差、溃决程度大、溃决速度快,容易形成巨型洪灾,对下游生命财产造成更大危害。首先简要总结了一般堰塞坝堵江研究,阐明了崩滑型堰塞坝成坝特点。然后分析崩滑碎屑体运动及破碎机理和碎屑体堵江成坝机理研究,明确了颗粒破碎和水流条件对坝体形态特征、物质组成和稳定性的作用。崩滑碎屑体堵江通常有3种成坝模式：滑入型、爬高型和折返型,不同类型堰塞坝的稳定性具有显著差异。堰塞坝的稳定性与坝体关键特征参数(几何形态、坝体结构和物质组成)密切相关,而坝体特征参数又主要由崩滑体在运移过程中碰撞破碎和入河堵江时的固液耦合作用共同决定。考虑上述两种因素,结合物源性质、边坡地形、河谷及水流条件,本文提出了成坝影响因素与堰塞坝的空间形态、结构特征及稳定性的内在关系的研究思路,以便建立基于坝体稳定性快速评价的坝体特征预测模型。本研究的开展可为堰塞坝形成前坝体特征的事先预测以及堰塞坝形成后坝体稳定性的快速评估等方面的研究与实践提供重要理论依据。

Review and Prospect of the Formation Mechanism of Landslide Dams Caused by Landslide and Avalanche Debris

Landslide dams are natural dams, which are formed where rivers are blocked by avalanches, landslides, and debris flows. China is a high incidence area of landslide dam disasters. According to the statistics, among the cases of landslide dam in the world, 758 cases occurred in China, accounting for 59%. In recent years, frequent geological tectonic activities and extreme climate disasters (typhoons, rainstorms, snow melting, etc.) have induced a large number of landslide dams, which significantly threaten the lives and properties of upstream and downstream people. The landslide dams caused by landslide or avalanche debris normally have loose structure, poor stability, high breach size and fast breaching velocity, leading to huge breaching flood and catastrophic disaster to the downstream areas. This paper first briefly reviewed the blocking studies of generic landslide dam, and clarified the formation characteristics of landslide dam caused by avalanche and debris. Then, the movement and fragmentation mechanism of debris body and the blocking mechanism of debris body were analyzed, the characteristics of particle separation and accumulation in the process of dam formation were specifically summarized. On this basis, the effects of particle fragmentation and geological conditions on the morphological characteristics, material compositions and dam stability were confirmed with less previous studies. There were usually three dam-forming modes:sliding type, climbing type and reentry type. There were significant differences in the stabilities of different types of dams. The stability of landslide dams was closely related to the dam characteristics (geometric shape, dam structure and material composition) which were jointly determined by the debris colliding and disintegrating during sliding and solid-liquid coupled interacting during debris rushing into river. A research idea was put forward to reveal the internal relationships between the influencing factors of dam formation and the spatial shape, structural characteristics and stability of dams, so as to establish a prediction model of dam characteristics based on the rapid evaluation of dam stability. This research was meaningful in both academic and practical phases to predict the key parameters of landslide dams before its formation, and rapidly assess the landslide dam stability after its formation.